阅读说明：本技术 掩模坯料、转印用掩模的制造方法、及半导体器件的制造方法 (Mask blank, method for manufacturing transfer mask, and method for manufacturing semiconductor device ) 是由 宍户博明 大久保亮 野泽顺 于 2020-02-20 设计创作，主要内容包括：本发明的课题在于,提供能够使掩模图案、硬掩模图案进一步微细化、以及能够提高图案品质的掩模坯料,为了解决该课题,本发明的掩模坯料(100)具备在透光性基板(1)上依次层叠有图案形成用薄膜(3)和硬掩模膜(4)的结构,该掩模坯料(100)如下所述地构成：上述硬掩模膜(4)的通过X射线光电子能谱法进行分析而得到的Si2p窄谱在103eV以上的键能具有最大峰,通过X射线光电子能谱法进行分析而得到的N1s窄谱的最大峰为检测下限值以下,硅与氧的含有比率(原子％)Si:O小于1:2。(In order to solve the problem, the mask blank (100) of the present invention is provided with a structure in which a pattern-forming thin film (3) and a hard mask film (4) are sequentially laminated on a light-transmitting substrate (1), and the mask blank (100) is configured as follows: the hard mask film (4) has a bond energy with a narrow Si2p spectrum of 103eV or more as analyzed by X-ray photoelectron spectroscopy, a maximum peak of a narrow N1s spectrum as analyzed by X-ray photoelectron spectroscopy, and a silicon to oxygen content ratio (atomic%) of Si: O of less than 1:2.)

1. A mask blank having a structure in which a thin film for pattern formation and a hard mask film are laminated in this order on a substrate,

the hard mask film is formed of a material containing silicon and oxygen,

the hard mask film has a maximum peak of a bond energy of a narrow Si2p spectrum of 103eV or more as analyzed by X-ray photoelectron spectroscopy,

the maximum peak of the narrow spectrum of N1s obtained by analysis of the hard mask film by X-ray photoelectron spectroscopy is less than or equal to the lower limit of detection,

the hard mask film has a silicon to oxygen content ratio in atomic% of Si to O of less than 1:2.

2. The mask blank according to claim 1,

the hard mask film has a maximum peak at a bond energy of 532eV or more in a narrow O1s spectrum obtained by analysis by X-ray photoelectron spectroscopy.

3. The mask blank according to claim 1 or 2, wherein,

the O1s narrow spectrum of the hard mask film analyzed by X-ray photoelectron spectroscopy has a maximum peak at a bond energy of less than 533 eV.

4. The mask blank according to any one of claims 1 to 3, wherein,

the difference between the bond energy of the maximum peak in the narrow Si2p spectrum obtained by analyzing the surface of the hard mask film by X-ray photoelectron spectroscopy and the bond energy of the maximum peak in the narrow Si2p spectrum obtained by analyzing the inside of the hard mask film by X-ray photoelectron spectroscopy is 0.2eV or less.

5. The mask blank according to any one of claims 1 to 4, wherein,

the difference between the bond energy of the largest peak in the O1s narrow spectrum obtained by analyzing the surface of the hard mask film by X-ray photoelectron spectroscopy and the bond energy of the largest peak in the O1s narrow spectrum obtained by analyzing the inside of the hard mask film by X-ray photoelectron spectroscopy is 0.1eV or less.

6. The mask blank according to any one of claims 1 to 5, wherein,

the hard mask film has a narrow Si2p spectrum obtained by analysis by X-ray photoelectron spectroscopy, and has no peak in the range of 97eV or more and 100eV or less of the bonding energy.

7. The mask blank according to any one of claims 1 to 6, wherein,

the hard mask film has an oxygen content of 60 atomic% or more.

8. The mask blank according to any one of claims 1 to 7, wherein,

the hard mask film is formed of a material containing silicon and oxygen, or a material containing silicon and oxygen, and at least one element selected from a non-metal element other than nitrogen and a semi-metal element.

9. The mask blank according to any one of claims 1 to 7, wherein,

the thin film for pattern formation is formed of a material containing one or more elements selected from chromium, tantalum, and nickel.

10. The mask blank according to any one of claims 1 to 9,

the pattern forming thin film is a light shielding film.

11. The mask blank according to claim 10,

a phase shift film is provided between the substrate and the light shielding film.

12. The mask blank according to any one of claims 1 to 9,

the pattern-forming thin film is an absorber film.

13. A method for manufacturing a transfer mask using the mask blank according to any one of claims 1 to 12, comprising:

forming a transfer pattern on the hard mask film by dry etching using a fluorine-based gas, using a resist film having the transfer pattern formed on the hard mask film as a mask; and

and forming a transfer pattern on the thin film for pattern formation by dry etching using a gas containing chlorine, using the hard mask film on which the transfer pattern is formed as a mask.

14. The method for manufacturing a transfer mask according to claim 13,

the dry etching using a chlorine-containing gas is performed in a state where a high bias is applied, using a chlorine-containing gas containing oxygen in which the ratio of the chlorine-containing gas is increased.

15. The method for manufacturing a transfer mask according to claim 13,

the dry etching using a chlorine-containing gas is performed under a high bias using a chlorine-based gas containing no oxygen.

16. A method of manufacturing a semiconductor device, the method comprising the steps of:

exposing and transferring the transfer pattern to a resist film on a substrate on which a semiconductor device is to be formed, using the transfer mask manufactured by the method for manufacturing a transfer mask according to any one of claims 13 to 15.

Technical Field

The present invention relates to a mask blank, a method for manufacturing a transfer mask using the mask blank, and a method for manufacturing a semiconductor device using the transfer mask manufactured from the mask blank.

Background

As a mask blank for a halftone phase shift mask, a mask blank having a structure in which a halftone phase shift film containing a metal silicide-based material, a light-shielding film containing a chromium-based material, and an etching mask film (hard mask film) containing an inorganic material are laminated on a light-transmitting substrate has been known (see, for example, patent document 1). In the case of manufacturing a phase shift mask using this mask blank, first, a resist pattern formed on the surface of the mask blank is used as a mask to form a pattern on an etching mask film by dry etching using a fluorine-based gas, then, the etching mask film is used as a mask to pattern a light-shielding film by dry etching using a mixed gas of chlorine and oxygen, and further, the pattern of the light-shielding film is used as a mask to pattern a phase shift film by dry etching using a fluorine-based gas.

Documents of the prior art

Patent document

Patent document 1: international publication No. 2004/090635

Patent document 2: japanese patent No. 6158460

Disclosure of Invention

Problems to be solved by the invention

In the mask blank as described in patent document 1, the light-shielding film made of a chromium compound is required to have light-shielding performance for reducing the amount of exposure light transmitted through the phase shift film to a predetermined value or less. When a phase shift mask is produced from the mask blank, a pattern including a light shielding tape is formed in the light shielding film. Further, it is required to satisfy a given optical density by a laminated structure of a phase shift film and a light shielding film. Meanwhile, the light-shielding film is required to function as an etching mask when the phase shift film is patterned by dry etching using a fluorine-based gas to form a phase shift pattern. In the phase shift mask completion stage, a relatively sparse pattern such as a light shielding pattern is generally formed in the light shielding film. However, in the process of manufacturing a phase shift mask from a mask blank, the light shielding film must function as an etching mask when forming a phase shift pattern, which is a fine transfer pattern, on the phase shift film. Therefore, it is desirable that a fine pattern can be formed with high dimensional accuracy also in the light-shielding film.

In dry etching of the light-shielding film containing a chromium-based material, a mixed gas of a chlorine-based gas and an oxygen gas (a chlorine-based gas containing oxygen) is used as an etching gas. In general, dry etching using such an oxygen-containing chlorine-based gas as an etching gas has a low tendency to anisotropic etching and a high tendency to isotropic etching.

In general, when a pattern is formed on a thin film for pattern formation by dry etching, etching is performed not only in the thickness direction of the film but also in the sidewall direction of the pattern formed on the thin film, that is, so-called lateral etching. In order to suppress the progress of the lateral etching, conventionally, it has been adopted to apply a bias from the opposite side to the main surface of the substrate on which the thin film is formed during dry etching, and to control the etching gas to contact the film more in the thickness direction. In the case of dry etching using an ion host of an etching gas having a high tendency to become an ionic plasma such as a fluorine-based gas, the controllability of the etching direction by the application of a bias is high, and the anisotropy of etching is improved, so that the lateral etching amount of the thin film to be etched can be made small.

On the other hand, in the case of dry etching using a chlorine-based gas containing oxygen, since oxygen has a high tendency to form radical plasma, the effect of controlling the etching direction by applying a bias is small, and it is difficult to improve the anisotropy of etching. Therefore, when a pattern is formed on the light-shielding film including the chromium-based material by dry etching using a chlorine-based gas containing oxygen, the amount of lateral etching is likely to increase.

When a light-shielding film of a chromium-based material is patterned by dry etching using a chlorine-based gas containing oxygen with a resist pattern formed of an organic-based material as an etching mask, the resist pattern is etched from above and degraded. At this time, the sidewall direction of the resist pattern is also etched to be degraded. Therefore, the width of the pattern formed on the resist film is designed in advance in anticipation of the amount of the sag caused by the lateral etching. In addition, the width of the pattern formed on the resist film is designed by estimating the amount of lateral etching of the light-shielding film made of chromium-based material.

In recent years, mask blanks have been used in which an etching mask film (hard mask film) made of a material having sufficient etching selectivity between chromium-based materials with respect to dry etching using a chlorine-based gas containing oxygen is provided on a light-shielding film made of a chromium-based material. In this mask blank, a pattern is formed on the hard mask film by dry etching using the resist pattern as a mask. Then, the light-shielding film is subjected to dry etching using a chlorine-based gas containing oxygen, using the hard mask film having the pattern formed thereon as a mask, thereby forming a pattern on the light-shielding film. The hard mask film is generally formed of a material that can be patterned by dry etching using a fluorine-based gas. Since dry etching using a fluorine-based gas is etching mainly using ions, anisotropic etching tends to be large. Therefore, the amount of lateral etching of the pattern sidewall in the patterned hard mask film is small. In addition, in the case of dry etching using a fluorine-based gas, the amount of lateral etching tends to be small also in a resist pattern used for forming a pattern on a hard mask film. Therefore, for the light-shielding film of chromium-based material, it is also desired that the amount of lateral etching in dry etching using a chlorine-based gas containing oxygen is small.

As a method for reducing the amount of lateral etching in the light-shielding film made of a chromium-based material, it has been studied to greatly increase the mixing ratio of a chlorine-based gas in a chlorine-based gas containing oxygen in dry etching of the chlorine-based gas containing oxygen. This is because the chlorine-based gas has a high tendency to become an ionic plasma. In dry etching using a chlorine-based gas containing oxygen in which the ratio of the chlorine-based gas is increased, it is inevitable that the etching rate of the light-shielding film made of a chromium-based material decreases. In order to compensate for the decrease in the etching rate of the light-shielding film made of chromium-based material, it has been studied to greatly increase the bias voltage applied during dry etching. Hereinafter, dry etching using a chlorine-based gas containing oxygen in which the ratio of the chlorine-based gas is increased and performed in a state where a high bias is applied will be referred to as "high bias etching of the chlorine-based gas containing oxygen".

The etching rate of the light-shielding film made of chromium-based material by the high-bias etching using the oxygen-containing chlorine-based gas is at a level comparable to that in the case of dry etching under conventional etching conditions. The amount of lateral etching of the light-shielding film during etching can be made smaller than in the prior art.

Further, when the light-shielding film is patterned under high-bias etching conditions using a hard mask film having a pattern formed thereon as a mask and using a chlorine-based gas containing oxygen as an etching gas by studying and adjusting the bonding, composition, and the like of a chromium-based material in the light-shielding film, the amount of lateral etching of the pattern of the light-shielding film to be formed can be greatly reduced, and as a result, a fine pattern can be formed on the phase-shift film with good accuracy (patent document 2).

However, further miniaturization of the pattern to be formed on the phase shift film is required, and for this reason, only the above-described technique of greatly reducing the amount of lateral etching of the pattern of the light-shielding film is insufficient. Further, there is a demand for further miniaturization of a pattern to be formed on a thin film for pattern formation such as a light-shielding film, a pattern to be formed on a hard mask film, and improvement of pattern quality. This is also true for a binary mask having a light-shielding film as a thin film for patterning and a reflective mask having an absorber film as a thin film for patterning.

In order to solve the above-described problems, the present invention provides a mask blank having a structure in which a thin film for pattern formation such as a light-shielding film and a hard mask film are sequentially stacked on a substrate, and the mask blank can realize further miniaturization of a pattern to be formed on the thin film for pattern formation such as a light-shielding film, a pattern to be formed on the hard mask film, and improvement of pattern quality.

In particular, the present invention provides a mask blank which has a hard mask film having excellent performance suitable for high bias etching conditions and which can achieve further miniaturization of a pattern to be formed on a thin film for pattern formation and improvement of pattern quality.

The present invention also provides a method for manufacturing a transfer mask capable of forming a fine pattern on a pattern-forming film with good accuracy by using the mask blank.

The invention also provides a method for manufacturing a semiconductor device using the transfer mask.

Means for solving the problems

The present invention has the following means as means for solving the above problems.

(constitution 1)

A mask blank having a structure in which a thin film for pattern formation and a hard mask film are laminated in this order on a substrate,

the hard mask film is formed of a material containing silicon and oxygen,

the hard mask film has a maximum peak of bond energy in a narrow Si2p spectrum of 103eV or more as analyzed by X-ray photoelectron spectroscopy,

the maximum peak of the narrow spectrum of N1s obtained by analysis of the hard mask film by X-ray photoelectron spectroscopy is not more than the lower limit of detection,

the hard mask film has a silicon to oxygen content ratio (atomic%) of Si to O of less than 1:2.

(scheme 2)

The mask blank according to claim 1, wherein,

the hard mask film has a maximum peak of a bond energy of 532eV or more in a narrow O1s spectrum obtained by analysis by X-ray photoelectron spectroscopy.

(scheme 3)

The mask blank according to claim 1 or 2, wherein,

the narrow spectrum of O1s obtained by analysis of the above hard mask film by X-ray photoelectron spectroscopy has a maximum peak at a bond energy of less than 533 eV.

(scheme 4)

The mask blank according to any one of claims 1 to 3, wherein,

the difference between the bond energy of the maximum peak in the narrow spectrum of Si2p obtained by analyzing the surface of the hard mask film by X-ray photoelectron spectroscopy and the bond energy of the maximum peak in the narrow spectrum of Si2p obtained by analyzing the inside of the hard mask film by X-ray photoelectron spectroscopy is 0.2eV or less.

(scheme 5)

The mask blank according to any one of claims 1 to 4, wherein,

the difference between the bond energy of the largest peak in the O1s narrow spectrum obtained by analyzing the surface of the hard mask film by X-ray photoelectron spectroscopy and the bond energy of the largest peak in the O1s narrow spectrum obtained by analyzing the inside of the hard mask film by X-ray photoelectron spectroscopy is 0.1eV or less.

(scheme 6)

The mask blank according to any one of claims 1 to 5, wherein,

the hard mask film has a narrow Si2p spectrum obtained by analysis by X-ray photoelectron spectroscopy, and has no peak in the range of 97eV or more and 100eV or less in bond energy.

(scheme 7)

The mask blank according to any one of claims 1 to 6, wherein,

the hard mask film has an oxygen content of 60 atomic% or more.

(scheme 8)

The mask blank according to any one of claims 1 to 7, wherein,

the hard mask film is formed of a material containing silicon and oxygen, or a material containing silicon and oxygen, and at least one element selected from a non-metal element other than nitrogen and a semi-metal element.

(scheme 9)

The mask blank according to any one of claims 1 to 7, wherein,

the thin film for pattern formation is formed of a material containing one or more elements selected from chromium, tantalum, and nickel.

(scheme 10)

The mask blank according to any one of claims 1 to 9, wherein,

the pattern forming thin film is a light shielding film.

(scheme 11)

The mask blank according to scheme 10, wherein,

a phase shift film is provided between the substrate and the light shielding film.

(scheme 12)

The mask blank according to any one of claims 1 to 9, wherein,

the pattern-forming thin film is an absorber film.

(scheme 13)

A method for manufacturing a transfer mask using the mask blank according to any one of claims 1 to 12, comprising:

forming a transfer pattern on the hard mask film by dry etching using a fluorine-based gas, using a resist film having the transfer pattern formed on the hard mask film as a mask; and

and forming a transfer pattern on the thin film for pattern formation by dry etching using a gas containing chlorine using the hard mask film on which the transfer pattern is formed as a mask.

(scheme 14)

The method for manufacturing a transfer mask according to claim 13, wherein,

the dry etching using a chlorine-containing gas is performed in a state where a high bias is applied, using a chlorine-containing gas containing oxygen in which the ratio of the chlorine-containing gas is increased.

(scheme 15)

The method for manufacturing a transfer mask according to claim 13, wherein,

the dry etching using a gas containing chlorine is performed under a high bias using a chlorine-based gas containing no oxygen.

(scheme 16)

A method of manufacturing a semiconductor device, the method comprising the steps of:

using the transfer mask manufactured by the method for manufacturing a transfer mask according to any one of claims 13 to 15, the transfer pattern is exposed and transferred to the resist film on the substrate on which the semiconductor device is to be formed.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention having the above configuration, it is possible to provide a mask blank having a structure in which a thin film for pattern formation such as a light-shielding film and a hard mask film are sequentially stacked on a substrate, and the mask blank can realize further miniaturization and improvement in pattern quality of a pattern to be formed on the thin film for pattern formation such as a light-shielding film and a pattern to be formed on the hard mask film.

In particular, according to the present invention, it is possible to provide a mask blank which has a hard mask film having excellent performance suitable for high-bias etching conditions, and which can achieve further miniaturization of a pattern to be formed on a thin film for pattern formation and improvement of pattern quality.

Further, according to the present invention, it is possible to provide a method for manufacturing a transfer mask, in which a fine pattern is formed on a pattern forming film with good accuracy by using the mask blank.

Further, according to the present invention, a method for manufacturing a semiconductor device using the transfer mask can be provided.

Drawings

Fig. 1 is a schematic cross-sectional view of an embodiment of a mask blank of the present invention.

Fig. 2 is a schematic cross-sectional view showing a manufacturing process of the phase shift mask of the present invention.

Fig. 3 is a graph showing the results (Si2p narrow spectrum) of XPS analysis (depth direction chemical bond state analysis) performed on the mask blank of example 1.

Fig. 4 is a graph showing the results (N1s narrow spectrum) of XPS analysis (analysis of chemical bond state in the depth direction) of the mask blank of example 1.

Fig. 5 is a graph showing the results (O1s narrow spectrum) of XPS analysis (analysis of chemical bond state in the depth direction) of the mask blank of example 1.

Fig. 6 is a schematic cross-sectional view of an embodiment of a reflective mask blank of the present invention.

Fig. 7 is a schematic cross-sectional view showing a process of manufacturing a reflective mask according to the present invention.

Description of the symbols

1 light-transmitting substrate

2 phase shift film

2a phase shift pattern

3 light-shielding film

3a, 3b light-shielding pattern

4 hard mask film

4a hard mask pattern

5a resist pattern

6b resist pattern

11 substrate

12 multilayer reflective film

13 protective film

14 absorber film (phase shift film)

15 hard mask film

16 back conductive film

100 mask blank

200 phase shift mask (mask for transfer)

300 reflection type mask blank

400 reflection type mask

Detailed Description

Hereinafter, several embodiments of the present invention will be described, and the process of completing the present invention will be described first.

The present inventors have studied further miniaturization of the pattern formed on the hard mask film and improvement of the pattern quality, and as a result, have found the following.

First, it is known that a hard mask film formed of a material containing silicon and oxygen has a ratio of 1:2 to Si: O (oxygen-deficient SiO film)₂Film) of Si to O in a ratio (atomic%) of less than 1:2 (oxygen-deficient SiO)₂Film) < Condition 1 > the etching rate for fluorine-based gas is high, and the hard mask film can be etched rapidly and completely.

Second, it is known that when a hard mask film is formed of a material containing silicon and oxygen, the resistance to dry etching by a chlorine-based gas containing oxygen is significantly reduced when the presence ratio of Si — O bonds having a low oxidation degree is high or when the presence ratio of silicon bonds not bonded to oxygen (Si — Si bonds) is high. If the resistance to dry etching is reduced, in the process of patterning a thin film for pattern formation (such as a light-shielding film) by dry etching using a chlorine-based gas containing oxygen with the hard mask film having a fine pattern formed thereon as a mask, a phenomenon in which the edge shape of the fine pattern of the hard mask film is deteriorated and a phenomenon in which the side etching of the side wall of the fine pattern proceeds become remarkable. In this case, even if a fine pattern is formed on the hard mask film with high accuracy, a phenomenon occurs in which the pattern shape of the hard mask film is deteriorated when dry etching is performed on the thin film for pattern formation using the pattern of the hard mask film as a mask. This causes a problem that a fine pattern cannot be formed with good accuracy on the pattern forming film.

The hard mask film has a remarkably reduced resistance to dry etching using a chlorine-based gas containing oxygen under high bias etching conditions. In general, when a thin film is dry-etched, both etching by chemical reaction and etching by physical action are performed. Etching by chemical reaction was performed by the following process: the etching gas in the plasma state contacts the surface of the thin film and bonds with silicon or metal elements in the thin film to generate a low-boiling-point compound (e.g., SiF)₄、CrO₂Cl₂Etc.) to sublimate. In etching by chemical reaction, silicon or a metal element in a state of being bonded to another element (for example, O, N or the like) is cleaved by the bonding to generate low boiling pointThe compound of point. In contrast, physical etching proceeds as follows: when the plasma of ions in the etching gas accelerated by the bias collides with the surface of the thin film (this phenomenon is also referred to as "ion impact"), each element including silicon or a metal element on the surface of the thin film physically bounces off (at this time, the bond between the elements is broken), and the silicon or the metal element and a compound having a low boiling point are generated and sublimated.

The high bias etching is dry etching which improves utilization of physical action as compared with dry etching under ordinary conditions. Etching using physical action significantly contributes to etching in the film thickness direction, but less contributes to etching in the sidewall direction of the pattern. On the other hand, etching by chemical reaction contributes to any of etching in the film thickness direction and etching in the sidewall direction of the pattern (lateral etching).

In order to solve the problem of the hard mask film having a low resistance to dry etching using a chlorine-based gas containing oxygen, it is necessary to form the hard mask film from a material having a low proportion of Si — O bonds or a low proportion of Si — Si bonds. Further, it was found that a narrow spectrum of Si2p obtained by X-ray Photoelectron Spectroscopy (XPS) could be used as an index for measuring the ratio of the presence of bonds in the material constituting the hard mask film. Specifically, it is found that the narrow spectrum of Si2p obtained by analyzing the hard mask film by X-ray photoelectron spectroscopy is adjusted so that the bond energy of 103eV or more has the maximum peak, and that < condition 2 >. It can be said that, in the hard mask film in which such a narrow spectrum of Si2p is obtained, even if the content ratio (atomic%) of Si to O of silicon (Si) to oxygen (O) is less than 1:2, the existence ratio of Si — O bonds having a low oxidation degree is low, or the existence ratio of silicon bonds not bonded to oxygen (Si — Si bonds) is low.

Silicon (Si) and oxygen (O) may take various bonding forms. For example, a form in which one oxygen is bonded to one silicon (Si), a form in which two oxygens are bonded to one silicon (Si), a form in which three oxygens are bonded to one silicon (Si), a form in which four oxygens are bonded to one silicon (Si), and the like. In addition, silicon (Si), oxygen (O), and hydrogen (H) may take various bonding forms. For example, a form in which three oxygen (O) and one hydrogen (H) are bonded to one silicon (Si), a form in which one oxygen (O) and one hydrogen (H) are bonded to one silicon (Si), a form in which two oxygen (O) and one hydrogen (H) are bonded to one silicon (Si), and the like. Therefore, it is difficult to define the bonding form of each constituent element inside the film by defining the composition of the hard mask film.

On the other hand, the position of the bond energy of the maximum peak in the Si2p narrow spectrum obtained by analyzing the silicon nitride film by X-ray photoelectron spectroscopy is relatively close to the position of the bond energy of the maximum peak in the Si2p narrow spectrum obtained by analyzing the silicon oxide film by X-ray photoelectron spectroscopy. Therefore, if the hard mask film formed of a material containing silicon and oxygen contains nitrogen, the maximum peak of the narrow spectrum of Si2p may be located at a bond energy of 103eV or more due to the presence of Si — N bonds even when the hard mask film has a high presence ratio of Si — O bonds with a low oxidation degree or when the hard mask film has a high presence ratio of Si — Si bonds. In this case, the position of the bond energy of the maximum peak of the narrow spectrum of Si2p cannot be used as an index.

Taking into account the results of this problem, the following conclusions were drawn: if the maximum peak of the N1s narrow spectrum obtained by analyzing the hard mask film by X-ray photoelectron spectroscopy is equal to or less than the detection lower limit < condition 3 >, the presence or absence of nitrogen in the hard mask film does not affect the position of the bond energy that becomes the maximum peak in the Si2p narrow spectrum.

The results of the above intensive studies led to the following conclusions: when the hard mask film containing silicon and oxygen satisfies all of the above three conditions, it is possible to further miniaturize the pattern to be formed on the thin film for pattern formation and the pattern to be formed on the hard mask film, and to improve the pattern quality. The three conditions are as follows:

< Condition 1 > the content ratio (atomic%) of silicon (Si) to oxygen (O) is Si: O is 1: 2;

< condition 2 > the bond energy of the narrow spectrum of Si2p obtained by analysis by X-ray photoelectron spectroscopy at 103eV or more has the maximum peak;

the maximum peak of the narrow spectrum of < condition 3 > N1s is below the lower detection limit.

Such etching of the hard mask film can be completed in a short time, and the resist can be thinned accordingly. In addition, as the resist can be thinned, distortion of a finer resist pattern can be prevented, and formation of a finer resist pattern can be achieved. Further, the hard mask film can be rapidly subjected to etching processing as described above. Thus, the side wall roughness and the line edge roughness of the pattern of the hard mask film are small, and the pattern of the hard mask film having smooth (smooth) side walls can be formed. As a result, the pattern quality of the hard mask film can be improved.

When the etching rate of a certain film is increased, the etching time for patterning the film is shortened. If the etching time when patterning the film is short, the time during which the side wall of the film is exposed to the etching gas is short, resulting in a decrease in the amount of lateral etching.

In addition, when the etching rate of a certain film is increased, the etching time in the film thickness direction is shortened, and the time during which the sidewall of a certain film is exposed to the etching gas is shortened. This makes it possible to form a pattern having smooth (smooth) sidewalls with a small sidewall roughness.

In order to obtain the above-described effects and conditions, the oxygen content of the hard mask film formed of a material containing silicon and oxygen is preferably 66.5 atomic% or less, more preferably 66.0 atomic% or less, and still more preferably 65.5 atomic% or less. When the oxygen content is too large, the above-described effects and conditions are difficult to obtain.

In order to obtain the three effects and states of the first, second, and third features, the oxygen content of the hard mask film formed of a material containing silicon and oxygen is preferably 60 atomic% or more, more preferably 62 atomic% or more, and still more preferably 64 atomic% or more. When the oxygen content is too small, the above-described effects and states are difficult to obtain.

In order to obtain the above-described effects and conditions, the hard mask film formed of a material containing silicon and oxygen has a silicon content of preferably 30 atomic% or more, more preferably 31 atomic% or more, and still more preferably 32 atomic% or more. When the content of silicon is too small, the above-described effects and states are difficult to obtain.

In order to obtain the above-described effects and conditions, the hard mask film formed of a material containing silicon and oxygen has a silicon content of preferably 40 atomic% or less, more preferably 39 atomic% or less, and still more preferably 38 atomic% or less. When the content of silicon is too large, the above-described effects and states are difficult to obtain.

A hard mask film formed of a material containing silicon and oxygen has a silicon (Si) to oxygen (O) content ratio (atomic%) of Si: O of less than 1:2 (being SiO in which oxygen is deficient)₂Film), even in a high vacuum state, for example, only a small amount of an element, such as N, C, present in the film formation chamber enters the oxygen-deficient portion.

The characteristics of the thin film (including characteristics such as etching rate and pattern quality (etching quality/processing accuracy, sidewall roughness, and line edge roughness)) are not determined only by the composition of the thin film, and the film density and the crystalline state of the thin film are factors that influence the characteristics of the thin film. Therefore, various conditions for forming a thin film by sputtering are adjusted so that the thin film is formed to have predetermined characteristics. For example, the thin film is formed to have predetermined characteristics by adjusting a wide variety of conditions such as a pressure in the film forming chamber, a power applied to the sputtering target, and a positional relationship such as a distance between the target and the film formation substrate when the thin film is formed. These film forming conditions are inherent to the film forming apparatus, and are appropriately adjusted so that the thin film has predetermined characteristics.

When a thin film is formed by reactive sputtering, it is effective to adjust the ratio of a mixed gas of a rare gas and a reactive gas (oxygen gas), but the present invention is not limited thereto.

SiO as oxygen deficiency₂The method of forming the film includes, for example, using SiO₂And a method of forming a film by sputtering the target.

SiO as oxygen-non-missing₂Examples of the method for forming the film include using an Si target and using O₂And a method of forming a film by sputtering with a gas.

In order to obtain the above-mentioned effects and conditions, it is preferable that the narrow spectrum of Si2p obtained by at least X-ray Photoelectron Spectroscopy (XPS: X-ray Photoelectron Spectroscopy) has the largest peak in the bond energy of 103.5eV or less, which means that the hard mask film has not only highly oxidized Si-O bonds but also low oxidized Si-O bonds and Si-Si bonds.

In addition to the above conditions, it is preferable that the O1s narrow spectrum obtained by analyzing the hard mask film by X-ray photoelectron spectroscopy has a maximum peak in bond energy of 532eV or more, which means that a large amount of highly oxidized Si — O bonds and other high oxides are present in the hard mask film. In addition to the above conditions, it is preferable that the narrow spectrum of O1s obtained by analyzing the hard mask film by X-ray photoelectron spectroscopy has a maximum peak at a bond energy of less than 533eV, which means that a suboxide such as a low-oxidized Si — O bond is present in the hard mask film.

It is preferable that the narrow spectrum of Si2p obtained by analyzing a hard mask film made of a material containing silicon and oxygen by X-ray photoelectron spectroscopy has no peak (detection limit value or less) in the range of the bond energy of 97eV or more and 100eV or less. When the narrow spectrum of Si2p in the hard mask film has a peak in the range of bond energy of 97eV or more and 100eV or less, Si — Si bonds are present in the hard mask film at a ratio of a certain or more, which is not preferable.

When a hard mask film formed of a material containing silicon and oxygen actively has Si — Si bonds (for example, the area intensity of Si — Si bonds is half or more and the same as the area intensity of Si — O bonds, and both Si — O bonds and Si — Si bonds are present in a considerable proportion), a narrow spectrum of Si2p obtained by analyzing the hard mask film by X-ray photoelectron spectroscopy has a maximum peak at a bond energy of less than 103eV, and a bond energy in a range of 97eV or more and 100eV or less has a maximum peak of Si — Si bonds.

In the hard mask film formed of a material containing silicon and oxygen, a difference between a bond energy of a maximum peak in a narrow Si2p spectrum obtained by analyzing the surface of the hard mask film by X-ray photoelectron spectroscopy and a bond energy of a maximum peak in a narrow Si2p spectrum obtained by analyzing the inside of the hard mask film by X-ray photoelectron spectroscopy is preferably 0.2eV or less.

In addition, the difference between the bond energy of the maximum peak in the N1s narrow spectrum obtained by analyzing the surface of the hard mask film by X-ray photoelectron spectroscopy and the bond energy of the maximum peak in the N1s narrow spectrum obtained by analyzing the inside of the hard mask film by X-ray photoelectron spectroscopy is preferably 0.1eV or less in the hard mask film formed of a material containing silicon and oxygen.

In any of the Si2p narrow spectrum and the O1s narrow spectrum of the hard mask film, it is preferable that the difference in bond energy is smaller (preferably substantially the same) in the film thickness direction (depth direction) to obtain high controllability in etching of the hard mask film.

Hereinafter, the detailed configuration of the present invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals.

< first embodiment >

[ mask blank and production thereof ]

Mask blank

Fig. 1 shows a schematic configuration of a first embodiment of a mask blank. The mask blank 100 shown in fig. 1 has a structure in which a phase shift film 2, a light-shielding film 3 (a pattern-forming thin film), and a hard mask film 4 are sequentially stacked on one main surface of a light-transmissive substrate 1. The mask blank 100 may have a structure in which a resist film is laminated on the hard mask film 4 as necessary. Hereinafter, the main components of the mask blank 100 will be described in detail.

[ translucent substrate ]

The light-transmissive substrate 1 is formed of a material having good transmittance to exposure light used in an exposure step of lithography. As such a material, synthetic quartz glass, aluminosilicate glass, soda-lime glass, and low thermal expansion glass (SiO)₂-TiO₂Glass, etc.), other various glass substrates. In particular, a substrate using synthetic quartz glass has high transmittance to an ArF excimer laser beam (wavelength: about 193nm), and thus can be suitably used as the transparent substrate 1 of the mask blank 100.

The exposure step in lithography here refers to an exposure step in lithography using a phase shift mask produced using the mask blank 100. The exposure light is used in the exposure step. As the exposure light, any of ArF excimer laser (wavelength: 193nm), KrF excimer laser (wavelength: 248nm), and i-ray light (wavelength: 365nm) can be used, and the ArF excimer laser is preferably used for the exposure light from the viewpoint of miniaturization of the phase shift pattern in the exposure step. Therefore, an embodiment of the case where an ArF excimer laser beam is used as the exposure light will be described below.

[ phase-shift film ]

The phase shift film 2 has optical characteristics as follows: the exposure light used in the exposure transfer step is made to have a predetermined transmittance, and a predetermined phase difference is generated between the exposure light transmitted through the phase shift film 2 and the exposure light passing through the atmosphere only at the same distance as the thickness of the phase shift film 2.

Such a phase shift film 2 is formed here of a material containing silicon (Si). The phase shift film 2 is preferably formed of a material containing nitrogen (N) in addition to silicon. As the phase shift film 2, a material which can be patterned by dry etching using a fluorine-based gas and has sufficient etching selectivity for a CrOCN film or the like constituting the light-shielding film 3 described later is used.

The phase shift film 2 may further contain one or more elements selected from semimetal elements, nonmetal elements, and metal elements if it can be patterned by dry etching using a fluorine-based gas.

The semimetal element may be any semimetal element other than silicon. The nonmetal element may be any nonmetal element other than nitrogen, and preferably contains at least one element selected from oxygen (O), carbon (C), fluorine (F), and hydrogen (H), for example. The metal elements may be exemplified by molybdenum (Mo), tungsten (W), titanium (Ti), tantalum (Ta), zirconium (Zr), hafnium (Hf), niobium (Nb), vanadium (V), cobalt (Co), chromium (Cr), nickel (Ni), ruthenium (Ru), tin (Sn), boron (B), germanium (Ge).

The phase shift film 2 is made of, for example, MoSiN, and the refractive index n, the extinction coefficient k, and the film thickness of the phase shift film 2 are selected so as to satisfy a predetermined phase difference (for example, 140 DEG to 190 DEG, preferably 150 DEG to 180 DEG) and a predetermined transmittance (for example, 1% to 30%) with respect to exposure light (for example, ArF excimer laser), and the composition of the film material and the film formation conditions of the film are adjusted so as to satisfy the refractive index n and the extinction coefficient k.

[ light-shielding film ]

The light-shielding film 3 is preferably formed of a material containing at least one or more elements selected from chromium and tantalum. The film structure of the light-shielding film 3 may be any of a single-layer structure and a laminated structure of two or more layers. In the case of the laminated structure, the reflection reducing effect of reducing the reflectance can be exerted on the exposure light or the inspection light at the time of defect inspection. Each of the light-shielding films having a single-layer structure and the light-shielding films having a laminated structure of two or more layers may have substantially the same composition in the thickness direction of the film or layer, or may have a composition gradient in the thickness direction of the film or layer. The film containing at least one element selected from chromium and tantalum is a film that can be patterned by dry etching using a mixed gas of a chlorine-based gas and oxygen gas (a chlorine-based gas containing oxygen) or a chlorine-based gas substantially free of oxygen.

The light-shielding film 3 is preferably formed of a material containing chromium. As a material containing chromium for forming the light-shielding film 4, in addition to chromium metal, a material containing one or more elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and fluorine (F) in chromium (Cr) is also cited. Generally, a chromium-based material is etched using a chlorine-based gas containing oxygen, but the etching rate of chromium metal with respect to the etching gas is not so high. In view of increasing the etching rate of the chlorine-based gas containing oxygen with respect to the etching gas, the material for forming the light-shielding film 3 is preferably a material in which chromium contains one or more elements selected from oxygen, nitrogen, carbon, boron, and fluorine. The material containing chromium for forming the light-shielding film 3 may contain one or more elements selected from molybdenum (Mo), indium (In), and tin (Sn). By containing one or more elements of molybdenum, indium, and tin in the material containing chromium, the etching rate of the chlorine-based gas containing oxygen can be further increased. When the light-shielding film 3 is formed of a material containing chromium, the content of silicon is preferably 5 atomic% or less, more preferably 3 atomic% or less, and even more preferably substantially not contained. This is because when the light-shielding film 3 contains silicon, the etching rate with respect to a chlorine-based gas containing oxygen decreases, and is not preferable in dry etching of the light-shielding film 3.

When the light-shielding film 3 is formed of a material containing tantalum, the material may be, in addition to tantalum metal, a material containing one or more elements selected from nitrogen, oxygen, boron, and carbon in tantalum. Examples thereof include: ta, TaN, TaO, TaON, TaBN, TaBO, TaBON, TaCN, TaCO, TaCON, TaBCN, TaBOCN, and the like. In addition, in the case where Ta or TaN is used as the light-shielding layer of the light-shielding film 3, Ta or TaN has a high reflectance with respect to exposure light, and therefore, a laminated structure in which an antireflection layer formed of TaO or the like is provided on the light-shielding layer is desired. When the light-shielding film 3 is formed of a tantalum-containing material, the content of silicon in the tantalum-containing material is preferably 5 atomic% or less, more preferably 3 atomic% or less, and even more preferably substantially not contained. In the case where the light-shielding film 3 is formed of the above-described tantalum-containing material and the light-shielding film 3 is patterned by dry etching using the hard mask film 4 as a mask, a chlorine-based gas substantially not containing oxygen may be used as an etching gas.

The light-shielding film 3 is preferably an amorphous structure or a microcrystalline structure in terms of reducing the surface Roughness and the Line Edge Roughness (LER) of the light-shielding pattern to be formed.

The light shielding film 3 is preferably formed by sputtering, and any sputtering method such as DC sputtering, RF sputtering, and ion beam sputtering may be applied. The magnetron sputtering system may be a Dual (Dual) magnetron system, or a normal system. By forming the light-shielding film 3 by sputtering, the light-shielding film 3 can be formed into a film having an amorphous or microcrystalline structure. The film forming apparatus may be an inline (inline) type or a single-wafer type.

The light-shielding film 3 is required to secure an Optical Density (OD) of more than 2.0 with respect to exposure light by a laminated structure with the phase-shift film 2. The optical density is preferably 2.8 or more, more preferably 3.0 or more.

[ hard mask film ]

The hard mask film 4 is formed of a material containing silicon and oxygen, or a material containing silicon and oxygen, and one or more elements selected from a non-metal element other than nitrogen and a semi-metal element. In this case, the hard mask film 4 may contain any semimetal element. When the semimetal element contains one or more elements selected from boron, germanium, antimony, and tellurium, it is preferable because it is expected to improve the conductivity of silicon used as a target when the hard mask film 4 is formed by a sputtering method. Examples of the nonmetal elements include carbon (C), fluorine (F), and hydrogen (H).

The hard mask film 4 is provided in contact with the surface of the light shielding film 3. The hard mask film 4 is a film formed of a material having etching selectivity to an etching gas used when etching the light-shielding film 3. The hard mask film 4 has a sufficient thickness of a film functioning only as an etching mask until the end of dry etching for forming a pattern on the light-shielding film 3, and is not limited to optical characteristics basically. Therefore, the thickness of the hard mask film 4 can be made much smaller than the thickness of the light-shielding film 3.

The thickness of the hard mask film 4 is required to be 20nm or less, preferably 15nm or less, and more preferably 10nm or less. This is because, if the thickness of the hard mask film 4 is too large, the thickness of the resist film serving as an etching mask increases in the dry etching for patterning the hard mask film 4. The thickness of the hard mask film 4 is required to be 2nm or more, preferably 3nm or more. This is because, if the thickness of the hard mask film 4 is too thin, the pattern of the hard mask film 4 may disappear before the dry etching for forming the light-shielding pattern on the light-shielding film 3 is completed, depending on the conditions of the high-bias etching using the chlorine-based gas containing oxygen.

In the dry etching with a fluorine-based gas for forming a pattern on the hard mask film 4, it is sufficient that the resist film of an organic material used as an etching mask has a film thickness that functions only as an etching mask until the dry etching of the hard mask film 4 is completed. Therefore, the thickness of the resist film can be reduced significantly by providing the hard mask film 4, as compared with a configuration in which the hard mask film 4 is not provided.

When the hard mask film 4 is formed of a material containing silicon and oxygen, adhesion to a resist film made of an organic material tends to be low, and therefore, it is preferable to improve the adhesion of the surface by applying HMDS (Hexamethyldisilazane) treatment (either alone or in combination with the HMDS treatment) to the surface of the hard mask film 4.

The hard mask film 4 is preferably an amorphous structure or a microcrystalline structure in terms of reducing the surface Roughness and the Line Edge Roughness (LER) of the formed light shielding pattern.

The hard mask film 4 is preferably formed by sputtering, and any sputtering method such as DC sputtering, RF sputtering, and ion beam sputtering may be applied. The sputtering may be a magnetron sputtering method, a Dual (Dual) magnetron method, or a normal method. By forming the hard mask film 4 by sputtering, the hard mask film 4 can be made into a film of an amorphous or microcrystalline structure. The film forming apparatus may be an inline (inline) type or a single-wafer type.

The material of the target may be silicon, and a target formed of a simple substance of silicon, a target containing silicon and oxygen, SiO, or the like may be used as long as silicon is a main component₂Targets, and the like.

[ resist film ]

In the mask blank 100, a resist film of an organic material is preferably formed in a thickness of 100nm or less in contact with the surface of the hard mask film 4. In the case of a fine pattern corresponding to the DRAM hp32nm generation, an SRAF (Sub-Resolution Assist Feature) having a line width of 40nm may be provided in a light-shielding pattern to be formed on the light-shielding film 3. In this case, however, the hard mask film 4 is provided as described above to suppress the film thickness of the resist film, thereby making it possible to reduce the aspect ratio of the cross section of the resist pattern formed of the resist film to 1: 2.5. Therefore, damage and detachment of the resist pattern can be suppressed during development of the resist film, during rinsing, and the like. The thickness of the resist film is more preferably 80nm or less. The resist film is preferably a resist for electron beam lithography exposure, and the resist is more preferably a chemically amplified resist.

[ production sequence of mask blank ]

The mask blank 100 configured as described above is manufactured by the following procedure. First, the transparent substrate 1 is prepared. The end face and the main surface of the light-transmitting substrate 1 are polished to a predetermined surface roughness (for example, the root mean square roughness Rq is 0.2nm or less in the inner region of a quadrangle having a side of 1 μm), and then subjected to a predetermined cleaning treatment and drying treatment.

Next, a phase shift film 2 is formed on the transparent substrate 1 by sputtering. After the phase shift film 2 is formed, annealing treatment is performed at a given heating temperature. Next, the light shielding film 3 is formed on the phase shift film 2 by sputtering. Then, the hard mask film 4 is formed on the light-shielding film 3 by sputtering. In the deposition of each layer by the sputtering method, a sputtering target containing a material constituting each layer at a predetermined composition ratio and a sputtering gas are used. Further, film formation using a mixed gas of a rare gas and a reactive gas as a sputtering gas is performed as necessary. Then, when the mask blank 100 has a resist film, the surface of the hard mask film 4 is subjected to hmds (hexamethyldisilazane) treatment as needed. Then, a resist film is formed on the surface of the hard mask film 4 subjected to HMDS treatment by a coating method such as a spin coating method, thereby completing the mask blank 100.

Method for manufacturing phase shift mask

Next, a method for manufacturing a phase shift mask (transfer mask) according to the first embodiment will be described with reference to fig. 2, taking as an example a method for manufacturing a halftone phase shift mask using the mask blank 100 having the structure shown in fig. 1.

First, a resist film is formed on the hard mask film 4 of the mask blank 100 by a spin coating method. Next, the resist film is exposed by an electron beam to draw a first pattern (phase shift pattern) to be formed on the phase shift film 2. Then, the resist film is subjected to predetermined processes such as PEB (Post Exposure Bake) processing, development processing, Post Bake processing, and the like, and a first pattern (resist pattern 5a) is formed on the resist film (see fig. 2 (a)).

Next, dry etching of the hard mask film 4 is performed using a fluorine-based gas with the resist pattern 5a as a mask, and a first pattern (hard mask pattern 4a) is formed on the hard mask film 4 (see fig. 2 (b)). The resist pattern 5a is then removed. Here, the dry etching of the light-shielding film 3 may be performed in a state where the resist pattern 5a remains without being removed. In this case, the resist pattern 5a disappears during dry etching of the light-shielding film 3.

Next, high-bias etching using a chlorine-based gas containing oxygen is performed using the hard mask pattern 4a as a mask, and a first pattern (light-shielding pattern 3a) is formed on the light-shielding film 3 (see fig. 2 c). The dry etching of the light-shielding film 3 with the chlorine-based gas containing oxygen uses an etching gas having a higher mixing ratio of the chlorine-based gas than that used in the prior art. The mixing ratio of the chlorine-based gas containing oxygen in the dry etching of the light-shielding film 3 is preferably a chlorine-based gas: oxygen is more than 10: 1. more preferably 15 or more: 1. more preferably 20 or more: 1. by using an etching gas having a high mixing ratio of the chlorine-based gas, the anisotropy of dry etching can be improved. In the dry etching of the light shielding film 3, the mixing ratio of the mixed gas of the chlorine-based gas and the oxygen gas is preferably a chlorine-based gas: oxygen is 40 or less: 1.

in addition, in the dry etching of the light-shielding film 3 using a chlorine-based gas containing oxygen, the bias applied to the back surface side of the transparent substrate 1 is also higher than in the conventional case. Although the effect of increasing the bias voltage varies depending on the etching apparatus, the power when applying the bias voltage is, for example, preferably 15[ W ] or more, more preferably 20[ W ] or more, and still more preferably 30[ W ] or more. By increasing the bias voltage, the anisotropy of dry etching using a chlorine-based gas containing oxygen can be increased.

Next, dry etching using a fluorine-based gas is performed using the light-shielding pattern 3a as a mask to form a first pattern (phase shift pattern 2a) on the phase shift film 2 and remove the hard mask pattern 4a (see fig. 2 d).

Next, a resist film was formed on the light-shielding pattern 3a by spin coating. The resist film is exposed by an electron beam to draw a second pattern (light-shielding pattern) to be formed on the light-shielding film 3. Then, a predetermined process such as a development process is performed to form a resist film (resist pattern 6b) having a second pattern (light-shielding pattern) (see fig. 2 e).

Next, dry etching using a chlorine-based gas containing oxygen is performed using the resist pattern 6b as a mask, and a second pattern (light-shielding pattern 3b) is formed on the light-shielding film 3 (see fig. 2 (f)). The dry etching of the light-shielding film 3 at this time can be performed under conventional conditions with respect to the mixing ratio of the chlorine-based gas containing oxygen and the bias voltage.

The resist pattern 6b is further removed, and a predetermined process such as cleaning is performed to obtain a phase shift mask 200 (see fig. 2 g).

The chlorine-based gas used for the dry etching in the above-described production process is not particularly limited as long as it contains Cl. For example, the chlorine-based gas may be Cl₂、SiCl₂、CHCl₃、CH₂Cl₂、CCl₄、BCl₃And the like. The fluorine-based gas used for dry etching in the above-described production process is not particularly limited as long as it contains F. For example, CHF is an example of the fluorine-based gas₃、CF₄、C₂F₆、C₄F₈、SF₆And the like. In particular, since the etching rate of the glass substrate by the fluorine-based gas containing no C is low, damage to the glass substrate can be further reduced.

The phase shift mask 200 manufactured by the above steps has a structure in which the phase shift pattern 2a and the light shielding pattern 3b are stacked on the transparent substrate 1 in this order from the transparent substrate 1 side.

In the above-described method for manufacturing a phase shift mask, the phase shift mask 200 is manufactured using the mask blank 100 described with reference to fig. 1. In the production of such a phase shift mask, dry etching using a chlorine-based gas containing oxygen, which tends to be isotropic, is applied to the step of fig. 2(c), which is a step of dry etching for forming a phase shift pattern (a fine pattern to be formed on the phase shift film 2) on the light-shielding film 3. The dry etching with the oxygen-containing chlorine-based gas in the step of fig. 2(c) is performed under high-bias etching conditions in which the ratio of the chlorine-based gas in the oxygen-containing chlorine-based gas is high. This can improve the anisotropy of etching while suppressing a decrease in the etching rate in the dry etching step of the light-shielding film 3. This reduces lateral etching when forming the phase shift pattern on the light-shielding film 3.

In addition, in the present invention, by applying the hard mask film 4 having excellent performance suitable for the high bias etching conditions, it is possible to further miniaturize the pattern to be formed on the hard mask film 4 and to improve the pattern quality. As a result, the pattern to be formed on the light-shielding film 3 can be further miniaturized and the pattern quality can be improved.

Further, lateral etching of the light-shielding film 3 is reduced, and further miniaturization of the pattern to be formed on the light-shielding film 3 and improvement of the pattern quality are achieved, and the phase shift pattern 2a can be formed with high accuracy by dry etching the phase shift film 2 with a fluorine-based gas using the light-shielding pattern 3a having a phase shift pattern formed with high accuracy as an etching mask. By the above operation, the phase shift mask 200 with high pattern accuracy can be manufactured.

Method for manufacturing semiconductor device

Next, a method for manufacturing a semiconductor device using the phase shift mask manufactured by the above-described manufacturing method as a transfer mask will be described. The manufacturing method of the semiconductor device has the following characteristics: the transfer pattern (phase shift pattern 2a) of the phase shift mask 200 is transferred by exposure to a resist film on the substrate using the halftone type phase shift mask 200 manufactured by the above-described manufacturing method. The method of manufacturing such a semiconductor device is performed as follows.

First, a substrate on which a semiconductor device is formed is prepared. The substrate may be, for example, a semiconductor substrate, a substrate having a semiconductor thin film, or a microfabricated film may be further formed on the substrate. Then, a resist film is formed on the prepared substrate, and pattern exposure is performed on the resist film using the halftone-type phase shift mask 200 manufactured by the above-described manufacturing method. Thereby, the transfer pattern formed on the phase shift mask 200 is exposed and transferred to the resist film. At this time, as the exposure light, exposure light corresponding to the phase shift film 2 constituting the transfer pattern is used, and here, for example, ArF excimer laser is used.

The resist film after exposure and transfer of the transfer pattern is subjected to a developing process to form a resist pattern, and the surface layer of the substrate is subjected to an etching process using the resist pattern as a mask to perform a process of introducing impurities. After the treatment is completed, the resist pattern is removed. The above-described process is repeated on the substrate while replacing the transfer mask, and necessary processing is further performed, thereby completing the semiconductor device.

In the manufacture of the semiconductor device as described above, by using the halftone-type phase shift mask manufactured by the above-described manufacturing method as a transfer mask, a resist pattern can be formed on a substrate with a precision that sufficiently satisfies the initial design specifications. Therefore, when the circuit pattern is formed by dry etching of the underlayer film under the resist film using the pattern of the resist film as a mask, a high-precision circuit pattern free from short-circuiting or disconnection of the wiring due to insufficient precision can be formed.

< second embodiment >

[ mask blank and production thereof ]

The mask blank according to the second embodiment of the present invention is a mask blank for manufacturing a binary mask (transfer mask) in which a thin film for pattern formation is a light-shielding film. However, the mask blank of the second embodiment may also be used as a mask blank for manufacturing a Phase shift mask of a cut-in Levenson type, or a CPL (chrome free Phase Lithography) mask.

The mask blank according to the second embodiment of the present invention is the mask blank according to the first embodiment described with reference to fig. 1, from which the phase shift film 2 has been removed. However, the light-shielding film 3 of this second embodiment is required to satisfy the Optical Density (OD) required in the laminated structure of the phase shift film 2 and the light-shielding film 3 of the first embodiment only by the light-shielding film 3. The method for manufacturing a mask blank according to the second embodiment of the present invention is a method in which the phase shift film 2 is removed from the mask blank according to the first embodiment after the manufacturing step and the processing step (etching step).

In the mask blank according to the second embodiment of the present invention, all configurations of the transparent substrate 1, the light-shielding film 3, the hard mask film 4, and the like are the same as all configurations described in the mask blank according to the first embodiment.

< third embodiment >

[ mask blank and production thereof ]

The mask blank according to the third embodiment of the present invention is a mask blank for manufacturing a reflective mask (transfer mask) in which a pattern-forming thin film is an absorber film (including a case having a phase shift function).

Fig. 6 is a schematic view for explaining the structure of a reflective mask blank according to a third embodiment of the present invention. As shown in fig. 6, the reflective mask blank 300 includes: a substrate 11, a multilayer reflective film 12, a protective film 13, an absorber film 14 that absorbs euv (extreme Ultra violet) light, and a hard mask film (etching mask) 15, which is a hard mask for etching, are sequentially laminated. The multilayer reflective film 12 is formed on the first main surface (front surface) side of the substrate 11, and reflects EUV light as exposure light. The protective film 13 is provided to protect the multilayer reflective film 12. The protective film 13 is formed of an etchant used for patterning the absorber film 14 described later and a material having resistance to a cleaning solution. The hard mask film 15 serves as a mask when etching the absorber film 14. A back conductive film 16 for an electrostatic chuck is usually formed on the second main surface (back surface) side of the substrate 11.

Hereinafter, each layer will be described.

[ base plate ]

As the substrate 11, in order to prevent distortion of the absorber pattern caused by heat when exposure is performed with EUV light, a material having a low thermal expansion coefficient in the range of 0 ± 5ppb/° c is preferably used. As a raw material having a low thermal expansion coefficient in this range, for example: SiO 2₂-TiO₂Glass-like, multicomponent glass-ceramic, and the like.

[ multilayer reflective film ]

The multilayer reflective film 12 is provided with a function of reflecting EUV light in a reflective mask 400 (fig. 7(e)) described later. The multilayer reflective film 12 has a structure of a multilayer film in which layers containing elements having different refractive indices as main components are periodically stacked.

Generally, as the multilayer reflective film 12, a multilayer film in which a thin film of a light element or a compound thereof (high refractive index layer) as a high refractive index material and a thin film of a heavy element or a compound thereof (low refractive index layer) as a low refractive index material are alternately laminated for about 40 to 60 cycles is used. The multilayer film may be formed by laminating a plurality of periods as 1 period, in a laminated structure of a high refractive index layer/a low refractive index layer in which a high refractive index layer and a low refractive index layer are laminated in this order from the substrate 11 side, or may be formed by laminating a plurality of periods as 1 period, in a laminated structure of a low refractive index layer/a high refractive index layer in which a low refractive index layer and a high refractive index layer are laminated in this order from the substrate 11 side. The outermost layer of the multilayer reflective film 12 (i.e., the surface layer of the multilayer reflective film 12 on the side opposite to the substrate 11) is preferably a high refractive index layer for the following reasons. In the multilayer film described above, when a laminated structure (high refractive index layer/low refractive index layer) in which a high refractive index layer and a low refractive index layer are laminated in this order on the substrate 11 is laminated for a plurality of cycles as 1 cycle, the uppermost layer becomes the low refractive index layer. However, the low refractive index layer on the outermost surface of the multilayer reflective film 12 is easily oxidized, and thus the reflectance of the multilayer reflective film 12 decreases. In order to avoid a decrease in reflectance, it is preferable to form the multilayer reflective film 12 by further forming a high refractive index layer on the uppermost low refractive index layer. On the other hand, in the multilayer film described above, when a multilayer structure (low refractive index layer/high refractive index layer) in which a low refractive index layer and a high refractive index layer are sequentially laminated on the substrate 11 is formed in a plurality of cycles by 1 cycle, the uppermost layer is a high refractive index layer. In this case, it is not necessary to further form a high refractive index layer.

In the third embodiment, a layer containing silicon (Si) is used as the high refractive index layer. As the Si-containing material, in addition to the simple substance Si, an Si compound containing boron (B), carbon (C), nitrogen (N), and/or oxygen (O) in Si can be used. By using a layer containing Si as the high refractive index layer, the reflective mask 400 for EUV lithography excellent in reflectivity of EUV light can be obtained (fig. 7 (e)). In the third embodiment, a glass substrate is preferably used as the substrate 11. Si is also excellent in adhesion to a glass substrate. As the low refractive index layer, a simple metal selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or an alloy thereof can be used. For example, as the multilayer reflective film 12 for EUV light having a wavelength of 13nm to 14nm, a Mo/Si periodic laminated film in which Mo films and Si films are alternately laminated for about 40 to 60 periods is preferably used. The high refractive index layer as the uppermost layer of the multilayer reflective film 12 may be formed of silicon (Si), and a silicon oxide layer containing silicon and oxygen may be formed between the uppermost layer (Si) and the Ru-based protective film 13. By forming the silicon oxide layer, the cleaning resistance of the reflective mask 400 can be improved.

Methods of forming the multilayer reflective film 12 are well known in the art. Each layer of the multilayer reflective film 12 can be formed by, for example, ion beam sputtering. In the case of the Mo/Si periodic multilayer film described above, for example, an Si film having a thickness of about 4nm is first formed on the substrate 11 using an Si target by an ion beam sputtering method, and then an Mo film having a thickness of about 3nm is formed using an Mo target. The multilayer reflective film 12 is formed by laminating the Si film/Mo film for 40 to 60 cycles as 1 cycle. The outermost layer of the multilayer reflective film 12 is preferably an Si layer.

[ protective film ]

The protective film 13 is formed on the multilayer reflective film 12 to protect the multilayer reflective film 12 from dry etching and cleaning in the manufacturing process of the reflective mask 400 described later. In addition, the protective film 13 can protect the multilayer reflective film 12 when performing black defect correction using a phase shift pattern of an Electron Beam (EB). The protective film 13 may have a single-layer or multilayer laminated structure of two or more layers. As the material of the protective film 13, a material containing ruthenium as a main component, for example, a Ru metal simple substance, or a Ru alloy containing Ru and at least one metal such as titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), and rhenium (Re) can be used.

The material of the protective film 13 may further contain nitrogen. Among these materials, a Ru-based protective film containing Ti is particularly preferable. In the case of using the Ru-based protective film containing Ti, diffusion of silicon which is a constituent element of the multilayer reflective film from the surface of the multilayer reflective film 12 to the Ru-based protective film becomes small. Therefore, the surface roughness during mask cleaning is reduced, and the film is less likely to be peeled off. The reduction of the surface roughness is directly related to preventing the reduction of the reflectivity to the EUV exposure light. Therefore, reduction of surface roughness is important for improvement of exposure efficiency of EUV exposure and improvement of throughput. The lowermost layer and the uppermost layer of the protective film 13 are formed of a material containing Ru, and a metal other than Ru or an alloy is interposed between the lowermost layer and the uppermost layer.

The thickness of the protective film 13 is not particularly limited as long as the protective film 13 can function as the protective film 13. The thickness of the protective film 13 is preferably 1.0nm to 8.0nm, and more preferably 1.5nm to 6.0nm, from the viewpoint of the reflectivity of EUV light.

As a method for forming the protective film 13, a known film forming method can be used without particular limitation. Specific examples of the method for forming the protective film 13 include a sputtering method and an ion beam sputtering method.

[ absorbent film ]

An absorber film 14 for absorbing EUV light is formed on the protective film 13. As a material of the absorber film 14, a material which has a function of absorbing EUV light and can be processed by dry etching using a chlorine-based gas containing oxygen or a chlorine-based gas containing no oxygen can be used. In the case of patterning the absorber film 14 by dry etching using a chlorine-based gas containing oxygen, examples of suitable materials include: a material containing chromium (Cr) is used as a material for forming the light-shielding film 3 of the first embodiment. On the other hand, when the absorber film 14 is patterned by dry etching using a chlorine-based gas containing no oxygen, examples of suitable materials include: a material containing tantalum (Ta), a material containing nickel (Ni), and a material containing cobalt (Co).

As the material containing tantalum (Ta) forming the absorber film 14, in addition to tantalum metal, a Ta-based material in which tantalum contains one or more elements selected from nitrogen, oxygen, boron, and carbon can be cited. Examples thereof include: ta, TaN, TaO, TaON, TaBN, TaBO, TaBON, TaCN, TaCO, TaCON, TaBCN, TaBOCN, and the like. In addition, as a material for forming the absorber film 14, a TaTi-based material containing tantalum (Ta) and titanium (Ti) may be applied. Examples of such a tai-based material include a tai alloy and a tai compound in which the tai alloy contains at least one of oxygen, nitrogen, carbon, and boron. Examples of the TaTi compound include: TaTiN, TaTiO, TaTiON, TaTiCON, TaTiB, TaTiBN, TaTiBO, TaTiBON, TaTiBCON, and the like.

As a material containing nickel (Ni) forming the absorber film 14, a nickel (Ni) simple substance or a nickel compound containing Ni as a main component is used. Ni has a higher extinction coefficient in EUV light than Ta, and is a material that can be dry-etched with a chlorine (Cl) gas. The refractive index n of Ni at a wavelength of 13.5nm is about 0.948 and the extinction coefficient k is about 0.073. In contrast, in the case of TaBN, which is an example of a conventional material for an absorber film, the refractive index n is about 0.949 and the extinction coefficient k is about 0.030.

Examples of the nickel compound include compounds in which at least one of boron (B), carbon (C), nitrogen (N), oxygen (O), phosphorus (P), titanium (Ti), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), tellurium (Te), palladium (Pd), tantalum (Ta), and tungsten (W) is added to nickel. By adding these elements to nickel, the etching rate can be increased, the workability can be improved, and/or the cleaning resistance can be improved. The Ni content of these nickel compounds is preferably 50 at% or more and less than 100 at%, more preferably 80 at% or more and less than 100 at%.

On the other hand, by configuring the absorber film 14 to contain cobalt (Co) and/or nickel (Ni), the extinction coefficient k can be set to 0.035 or more, and the absorber film can be made thin. Further, by using the absorber film 14 as an amorphous metal, the etching rate can be increased, the pattern shape can be made good, and the processing characteristics can be improved. The amorphous metal may be a material in which at least one or more elements (X) selected from tungsten (W), niobium (Nb), tantalum (Ta), titanium (Ti), zirconium (Zr), hafnium (Hf), yttrium (Y), and phosphorus (P) is added to at least one or more elements selected from cobalt (Co) and nickel (Ni).

The absorber film 14 can be formed by a known method, for example, a magnetron sputtering method such as a DC sputtering method or an RF sputtering method.

The absorber film 14 may be an absorber film 14 for absorbing EUV light used for the binary-type reflective mask blank 300. The absorber film 14 may be an absorber film 14 used for the phase-shift-type reflective mask blank 300 and having a phase shift function in consideration of the phase difference of EUV light.

In the case of the absorber film 14 for absorbing EUV light, the film thickness is set so that the reflectivity of EUV light to the absorber film 14 becomes 2% or less.

In the case of the absorber film 14 having a phase shift function, the EUV light is absorbed and attenuated in the portion where the absorber film 14 is formed, and part of the light is reflected at a level that does not adversely affect the pattern transfer. On the other hand, the reflected light from the field portion where the absorber film 14 is not formed is reflected from the multilayer reflective film 12 via the protective film 13. By the absorber film 14 having the phase shift function, a desired phase difference can be formed between the portion where the absorber film 14 is formed and the reflected light from the field portion. The absorber film 14 is formed so that the phase difference between the reflected light from the absorber film 14 and the reflected light from the multilayer reflective film 12 (field portion) is 160 degrees (°) to 200 degrees (°). The light beams with the phase difference reversed by about 180 degrees interfere with each other at the edge of the pattern, thereby improving the image contrast of the projected optical image. As the image contrast is improved, the resolution is increased, and various tolerances related to exposure, such as exposure tolerance and focus tolerance, can be expanded. Although it depends on the pattern and the exposure conditions, the reflectance standard for obtaining the phase shift effect is generally 1% or more in terms of absolute reflectance and 2% or more in terms of reflectance to the multilayer reflective film 12 (with the protective film 13).

The absorber film 14 can be a single layer film. The absorber film 14 may be a multilayer film composed of two or more layers. When the absorber film 14 is a single-layer film, the number of steps in manufacturing a mask blank can be reduced, thereby improving the production efficiency. When the absorber film 14 is a multilayer film, the optical constants and the film thickness thereof may be appropriately set so that the upper layer film becomes an antireflection film for mask pattern inspection using light. This can improve the inspection sensitivity when the mask pattern is inspected by light. In this way, various functions can be added to the absorber film 14 by using the absorber film 14 of the multilayer film. When the absorber film 14 is an absorber film having a phase shift function, the use of the absorber film 14 having a multilayer film makes it possible to widen the range of adjustment of the optical surface, and to easily obtain a desired reflectance. Further, as a part (uppermost layer) of the absorber film 14 of the multilayer film, a mode using the hard mask film 15 of the present invention described later may be adopted.

An oxide layer is preferably formed on the surface of the absorber film 14 of nickel compound. By forming the oxide layer of the nickel compound, the resistance to cleaning of the absorber pattern 14a of the obtained reflective mask 400 (fig. 7(e)) can be improved. The thickness of the oxide layer is preferably 1.0nm or more, more preferably 1.5nm or more. The thickness of the oxide layer is preferably 5nm or less, more preferably 3nm or less. If the thickness of the oxide layer is less than 1.0nm, the oxide layer is too thin to expect an effect, and if it exceeds 5nm, the influence on the surface reflectance of the mask inspection light becomes large, and it becomes difficult to perform control for obtaining a predetermined surface reflectance.

Examples of the method for forming the oxide layer include subjecting a mask blank on which the absorber film is formed to a hot water treatment, an ozone water treatment, a heating treatment in an oxygen-containing gas, an ultraviolet irradiation treatment in an oxygen-containing gas, and O₂Plasma treatment, etc.

[ hard mask film ]

A hard mask film 15 is formed on the absorber film 14. The material, film thickness, and the like of the hard mask film 15 are all the same as those of the hard mask film 4 described in the first embodiment.

Ni has a lower dry etching rate with chlorine-based gas than Ta. Therefore, if it is desired to directly form the resist film 17 on the absorber film 14 made of a material containing Ni (fig. 7 a), the resist film 17 must be thickened, and it is difficult to form a fine pattern. On the other hand, by forming the hard mask film 15 made of a material containing Si on the absorber film 14, the absorber film 14 can be etched without increasing the thickness of the resist film 17. Therefore, by using the hard mask film 15, a fine absorber pattern 14a can be formed.

In addition, the hard mask film 15 made of a material containing silicon and oxygen according to the present invention has more excellent performance than the conventional hard mask film. In the present invention, by applying the hard mask 15 having excellent performance suitable for the high bias etching conditions, it is possible to further miniaturize the pattern to be formed on the hard mask film 15 and to improve the pattern quality. As a result, the pattern to be formed on the absorber film 14 can be further miniaturized and the pattern quality can be improved.

The hard mask film 15 is preferably 2nm or more in film thickness from the viewpoint of obtaining a function as an etching mask for forming a transfer pattern on the absorber film 14 with good accuracy. In addition, the hard mask film 15 has a film thickness of preferably 20nm or less, more preferably 15nm or less, from the viewpoint of reducing the film thickness of the resist film 17.

[ Back surface conductive film ]

Generally, a back conductive film 16 for an electrostatic chuck is formed on the second main surface (back surface) side of the substrate 11 (the opposite side to the surface on which the multilayer reflective film 12 is formed). The electrical characteristics required for the back conductive film 16 for an electrostatic chuck are generally 100 Ω/square or less. The back conductive film 16 can be formed by using a target of metal such as chromium or tantalum or an alloy thereof by, for example, magnetron sputtering or ion beam sputtering. Typical materials of the back conductive film 16 are CrN and Cr which are commonly used for manufacturing mask blanks such as light transmissive mask blanks. The thickness of the back conductive film 16 is not particularly limited as long as it satisfies the function as an electrostatic chuck, and is usually 10nm to 200 nm. The back conductive film 16 also serves to adjust the stress on the second main surface side of the mask blank 300. The back conductive film 16 can be adjusted so as to balance the stress from the various films formed on the first main surface side, thereby obtaining a flat reflective mask blank 300.

Reflective mask and method for manufacturing the same

The reflective mask blank 300 of the present third embodiment can be used to manufacture a reflective mask 400.

Referring to fig. 7, first, a reflective mask blank 300 is prepared, and a resist film 17 is formed on the hard mask film 15 on the first main surface thereof (which is not necessary in the case where the reflective mask blank 300 is provided with the resist film 17) (fig. 7 (a)).

Next, a desired pattern is drawn (exposed) on the resist film 17, and further developed and rinsed, thereby forming a predetermined resist pattern 17a (fig. 7 (b)).

The hard mask film 15 is etched using the resist pattern 17a as a mask to form an etching mask pattern 15a (fig. 7 c).

Next, the resist pattern 17a is removed by ashing, a resist stripping solution, or the like. Then, dry etching is performed using the etching mask pattern 15a as a mask, whereby the absorber film 14 is etched to form an absorber pattern 14a (fig. 7 d).

Then, the etching mask pattern 15a is removed by dry etching (fig. 7 (e)). Finally, at least one of washing with an acidic aqueous solution and washing with a basic aqueous solution is performed.

When the hard mask film 15 is formed of a material containing silicon (Si), CF may be used as an etching gas for forming the pattern of the hard mask film 15 and removing the etching mask pattern 15a₄、CHF₃、C₂F₆、C₃F₆、C₄F₆、C₄F₈、CH₂F₂、CH₃F、C₃F₈、SF₆And F₂Equal fluorine-containing gas, He and H₂、N₂、Ar、C₂H₄And O₂And the like (they are collectively referred to as "fluorine-containing gas").

Examples of the etching gas for the absorber film 14 include: cl₂、SiCl₄、CHCl₃And CCl₄Chlorine-containing gas is iso-supplied toA mixed gas containing a chlorine-based gas and He at a predetermined ratio, a mixed gas containing a chlorine-based gas and Ar at a predetermined ratio, and the like. In the etching of the absorber film 14, the etching gas does not substantially contain oxygen, and therefore, the Ru-based protective film does not have surface roughness. In the present specification, "the etching gas contains substantially no oxygen" means that the content of oxygen in the etching gas is 5 atomic% or less.

Note that, there is also a method of etching the absorber film 14 using the etching mask pattern 15a with the resist pattern 17a as a mask without removing the resist pattern 17a immediately after the etching mask pattern 15a is formed. In this case, the following features exist: when the absorber film 14 is etched, the resist pattern 17a is automatically removed, and the process is simplified. On the other hand, the following features exist: in the method of etching the absorber film 14 using the etching mask pattern 15a from which the resist pattern 17a has been removed as a mask, stable etching can be achieved without a change in organic products (exhaust gas) from the resist that disappears during etching.

Through the above steps, the reflective mask 400 having a fine pattern with a small side wall roughness and a small masking effect and high accuracy can be obtained.

Method for manufacturing semiconductor device

By performing EUV exposure using the reflective mask 400 of the present third embodiment, a desired transfer pattern based on the absorber pattern 14a on the reflective mask 400 can be formed on a substrate on which a semiconductor device is to be formed.

Examples

Hereinafter, embodiments of the present invention will be described more specifically by way of examples.

EXAMPLE 1

[ production of mask blank ]

Referring to fig. 1, a light-transmissive substrate 1 made of synthetic quartz glass having a main surface with dimensions of about 152mm × about 152mm and a thickness of about 6.35mm was prepared. The end face and the main surface of the light-transmitting substrate 1 were polished to a predetermined surface roughness (0.2 nm or less in Rq), and then subjected to a predetermined cleaning treatment and drying treatment.

Next, the translucent substrate 1 was set in a single-wafer DC sputtering apparatus, and argon (Ar) and nitrogen (N) were mixed by using a mixed sintering target of molybdenum (Mo) and silicon (Si) (Mo: Si 11 atomic%: 89 atomic%), and using a mixed sintering target of molybdenum (Mo) and silicon (Si)₂) And helium (He) as a sputtering gas, and a phase shift film 2 containing molybdenum, silicon, and nitrogen was formed on the transparent substrate 1 in a thickness of 69 nm.

Next, a heat treatment for reducing the film stress of the phase shift film 2 and for forming an oxide layer on the surface layer of the transparent substrate 1 on which the phase shift film 2 is formed is performed. Specifically, a heating treatment was performed in an atmosphere using a heating furnace (electric furnace) at a heating temperature of 450 ℃ for 1 hour. The transmittance and phase difference (amount of phase shift) of the phase shift film 2 after the heat treatment with respect to light having a wavelength of 193nm were measured by using a phase shift amount measuring apparatus (MPM 193 manufactured by Lasertec corporation), and the transmittance was 6.0% and the phase difference was 177.0 degrees (°).

Next, the translucent substrate 1 on which the phase shift film 2 was formed was set in a single-wafer DC sputtering apparatus, and argon (Ar) and carbon dioxide (CO) were added using a chromium (Cr) target₂) Nitrogen (N)₂) And helium (He) in a mixed gas atmosphere. Thus, a light-shielding film (CrOCN film) 3 containing chromium, oxygen, carbon, and nitrogen was formed in contact with the phase shift film 2 to a film thickness of 43 nm.

Next, the light-transmitting substrate 1 on which the light-shielding film (CrOCN film) 3 is formed is subjected to heat treatment. Specifically, a heating treatment was performed using a hot plate at a heating temperature of 280 ℃ for 5 minutes in the air. After the heat treatment, the optical density of the laminated structure of the phase shift film 2 and the light-shielding film 3 at the wavelength of ArF excimer laser light (about 193nm) was measured with a spectrophotometer (Cary 4000, manufactured by Agilent Technologies) for the light-transmitting substrate 1 on which the phase shift film 2 and the light-shielding film 3 were laminated, and was confirmed to be 3.0 or more.

Next, a translucent substrate 1 on which a phase shift film 2 and a light shielding film 3 are laminated is provided in a single-wafer RF sputtering apparatus, and silicon dioxide (SiO) is used₂) The target was sputtered with argon (Ar) gas (pressure 0.03Pa) and the power of the RF power source was adjustedA hard mask film 4 containing silicon and oxygen was formed on the light-shielding film 3 by RF sputtering to a thickness of 15nm, assuming that the power was 1.5 kW. Further, a given cleaning process was performed, and a mask blank 100 of example 1 was manufactured.

As will be described later, the hard mask film 4 containing silicon and oxygen has a high etching rate with respect to a fluorine-based gas, and thus the hard mask film 4 can be etched quickly and completely.

It is found that the hard mask film 4 containing silicon and oxygen tends to have a relatively low film density (low density), and the content ratio (atomic%) of silicon (Si) to oxygen (O) is such that Si: O is less than 1:2 (SiO in which oxygen is absent)₂A film).

A mask blank 100 in which a phase shift film 2, a light-shielding film 3, and a hard mask film 4 were formed on the main surface of the other transparent substrate 1 under the same conditions was prepared. The mask blank 100 was analyzed by X-ray photoelectron spectroscopy (XPS with RBS correction). As a result, the content of each constituent element of the hard mask film 4 was calculated as Si: 35 atomic%, O: 65 atom%.

The light-transmissive substrate 1, the phase shift film 2, the light-shielding film 3, and the hard mask film 4 of example 1 were analyzed by X-ray photoelectron spectroscopy, and the results of the analysis of the chemical bond state in the depth direction of the narrow spectrum of Si2p, the analysis of the chemical bond state in the depth direction of the narrow spectrum of N1s, and the analysis of the chemical bond state in the depth direction of the narrow spectrum of O1s, respectively, are shown in fig. 3, 4, and 5, respectively.

In the analysis of the hard mask film 4 by the X-ray photoelectron spectroscopy, the analysis in the film thickness direction was performed in the order of the hard mask film 4, the light-shielding film 3, the phase shift film 2, and the light-transmissive substrate 1 by repeating the steps of irradiating the surface of the mask blank 100 (the hard mask film 4) with X-rays, measuring the energy distribution of photoelectrons emitted from the hard mask film 4, digging into the hard mask film 4 for a predetermined time by Ar gas sputtering, irradiating the surface of the hard mask film 4 in the dug-in region with X-rays, and measuring the energy distribution of photoelectrons emitted from the hard mask film 4. In the analysis by the X-ray photoelectron spectroscopy, the X-ray source used was monochromated Al (14)86.6eV) and in the detection area of the photoelectrons isThe detection depth was about 4 to 5nm (extraction angle: 45 °) (the same applies to other examples and comparative examples described below).

In each of the depth direction chemical bond state analyses in fig. 3 to 5, the analysis result of the outermost surface of the hard mask film 4 before the Ar gas sputtering (sputtering time: 0min) is shown in a graph of "0.00 min", and the analysis result of the position in the thickness direction of the hard mask film 4 after the hard mask film 4 is dug in only 1.00min from the outermost surface by the Ar gas sputtering is shown in a graph of "1.00 min".

In the analysis of the chemical bond state in each depth direction in fig. 3 to 5, the analysis result of the position in the thickness direction of the light-shielding film 3 after digging only 4.00min from the outermost surface of the hard mask film 4 by Ar gas sputtering is shown in a graph of "4.00 min". Further, an analysis result of a position in the thickness direction of the light-shielding film 3 after digging only 9.00min from the outermost surface of the hard mask film 4 by Ar gas sputtering is shown in a "9.00 min graph". Further, an analysis result of the position in the thickness direction of the light-shielding film 3 after digging only 14.00min from the outermost surface of the hard mask film 4 by Ar gas sputtering is shown in a "14.00 min graph".

In the analysis of the chemical bond state in each depth direction in fig. 3 to 5, the analysis result of the position in the thickness direction of the phase shift film 2 after digging only 19.00min from the outermost surface of the hard mask film 4 by the Ar gas sputtering is shown in a graph of "19.00 min". The analysis result of the position in the thickness direction of the phase shift film 2 after digging only 24.00min from the outermost surface of the hard mask film 4 by the Ar gas sputtering is shown in a graph of "24.00 min", and the analysis result of the position in the thickness direction of the phase shift film 2 after digging only 30.00min from the outermost surface of the hard mask film 4 by the Ar gas sputtering is shown in a graph of "30.00 min". The analysis result of the position in the thickness direction of the transparent substrate 1 after digging in 44.00min from the outermost surface of the hard mask film 4 by the Ar gas sputtering is shown in a "44.00 min graph".

The scale of the vertical axis of the graphs in each narrow spectrum of fig. 3-5 is different. In the narrow spectrum of Si2p of fig. 3, the scale of the vertical axis is greatly enlarged compared to the narrow spectrum of Si2p of the other graphs for each of the "9.00 min graph" and the "14.00 min graph". That is, the wave of vibration in each narrow spectrum of the "graph of 9.00 min" and the "graph of 14.00 min" of the narrow spectrum of Si2p of fig. 3 does not indicate the presence of a peak, but only noise. This result shows that the content of silicon is equal to or less than the detection lower limit at the position in the thickness direction corresponding to each narrow spectrum of Si2p of the light-shielding film 3.

Among the N1s narrow spectra in fig. 4, each of the "0.00 min graph", "1.00 min graph", and "44.00 min graph" is also a scale in which the vertical axis is greatly enlarged as compared with the N1s narrow spectra of the other graphs. That is, the wave of vibration in each narrow spectrum of the "0.00 min graph", "1.00 min graph", and "44.00 min graph" of the N1s narrow spectrum of fig. 4 does not indicate the presence of a peak, but only indicates noise (i.e., not more than the detection lower limit value). This result shows that the nitrogen content is not more than the lower detection limit at the position in the thickness direction corresponding to the narrow spectrum of N1s of the hard mask film 4 and the transparent substrate 1.

The narrow spectrum of Si2p for the "4.00 min plot" of fig. 3 is also enlarged in scale on the vertical axis compared to the respective narrow spectra of the "0.00 min plot" and the "1.00 min plot". That is, the narrow spectrum of Si2p for the "4.00 min plot" indicates that a small number of peaks were detected. This result is considered that a peak is detected at a position in the thickness direction of the light-shielding film 4 corresponding to the "4.00 min graph" by being slightly affected by the hard mask film 5 present thereon.

The analysis result of the position in the thickness direction of the hard mask film 4 after digging only 1.00min from the outermost surface of the light-shielding film 3 by Ar gas sputtering was the measurement result of the portion other than the surface layer portion of the hard mask film 4.

From the results of the narrow spectrum of Si2p in fig. 3, it is understood that the hard mask film 4 of example 1 has the maximum peak at the bond energy (103.4eV) between 103 to 103.5eV, and this result means that Si — O bonds are present at a certain ratio or more (mainly Si — O bonds having a high oxidation degree) and that Si — O bonds and Si — Si bonds having a low oxidation degree are present at a low ratio.

From the results of the narrow spectrum of Si2p ("the narrow spectrum of the 0.00min graph" and the narrow spectrum of the "1.00 min graph") of the hard mask film 4 of fig. 3, it is understood that the waveform of the hard mask film 4 of example 1 has a substantially flat bond energy between 97 to 100eV and no peak (not more than the detection lower limit), and the result means that no Si — Si bond is detected from the hard mask film 4.

As can be seen from the results of the narrow spectrum of Si2p in fig. 3, the difference between the maximum peak position of the outermost surface (0.00min) and the maximum peak position of the film inside (1.00min) of the hard mask film 4 of example 1 is less than 0.2 eV. It is found that when the difference is relatively small, it is preferable to obtain high controllability in the etching of the hard mask film.

From the results of the narrow spectrum of N1s in fig. 4, it is understood that the maximum peak of the hard mask film 4 in example 1 is not more than the detection lower limit value. This result means that no nitrogen-bonded atoms including Si — N bonds were detected from the hard mask film 4 of example 1.

As is clear from the above, the hard mask film 4 of example 1 is formed of a material that satisfies the following three conditions at the same time. That is, the content ratio of silicon (Si) to oxygen (O), Si: O, is less than 1:2(1:1.86), satisfying condition 1; the narrow spectrum of Si2p has the largest peak at the bond energy (103.4eV) between 103 and 103.5eV, and the condition 2 is met; the maximum peak of the N1s narrow spectrum is equal to or less than the detection lower limit, and satisfies condition 3.

As is clear from the results of the narrow O1s spectrum of FIG. 5, the hard mask film 4 of example 1 has a maximum peak in the bond energy between 532-533 eV. This means that a high oxide (Si-O bond having a high degree of oxidation) (SiO) is present at a ratio of at least a certain value₂As the main body).

In addition, as is clear from the results of the narrow spectrum of O1s in fig. 5, the hard mask film 4 of example 1 has almost no difference (less than 0.05eV) between the maximum peak position of the outermost surface (0.00min) and the maximum peak position of the film interior (1.00 min). When the difference is relatively small, it is preferable to obtain high controllability in etching of the hard mask film.

[ production of phase Shift mask ]

Next, using the mask blank 100 of example 1, the halftone-type phase shift mask 200 of example 1 was manufactured in the following procedure. Referring to fig. 2, first, the surface of the hard mask film 4 is subjected to HMDS treatment.

Then, a resist film made of a chemical amplification resist for electron beam lithography was formed by a spin coating method so as to contact the surface of the hard mask film 4 with a film thickness of 70nm (conventionally 80 nm). Next, a first pattern, which is a phase shift pattern to be formed on the phase shift film 2, is drawn by electron beam irradiation on the resist film, and a predetermined developing process and cleaning process are performed to form a resist pattern 5a having the first pattern (see fig. 2 (a)). The first pattern is a pattern (phase shift pattern) including a fine pattern (SRAF pattern or the like having a line width of 35nm or less (conventionally 40nm or less)) to be formed on the phase shift film 2. The resist pattern 5a formed on the hard mask film 4 was good in that no distortion of the resist pattern was observed.

Next, CF was used using the resist pattern 5a as a mask₄The first pattern (hard mask pattern 4a) is formed on the hard mask film 4 by dry etching with gas (see fig. 2 (b)).

In this case, it is understood that the hard mask film 4 containing silicon and oxygen has a high etching rate with respect to the fluorine-based gas, and thus the hard mask film can be quickly etched with high accuracy.

The etching rate of the hard mask film 4 was calculated from the film thickness and the etching time of the hard mask film 4, and as a result, the etching rate with respect to the fluorine-based gas was relatively larger than that of the hard mask film 4 of comparative example 1 described later.

In addition, the hard mask pattern 4a was observed with a Scanning Electron Microscope (SEM), and as a result, the surface of the sidewall was smooth.

Next, the resist pattern 5a is removed. Next, using chlorine gas (Cl) was performed using the hard mask pattern 4a as a mask₂) With oxygen (O)₂) Mixed gas (gas flow rate ratio Cl)₂：O₂13:1) dry etching (power at bias application of 50[ W ]]High-bias etching) of (b), a first pattern (light-shielding pattern 3a) is formed on the light-shielding film 3 (see fig. 2 (c)). The etching time (total etching) of the light-shielding film 3Etching time) was set to a time 1.5 times the time (appropriate etching time) from the start of etching of the light-shielding film 3 to the initial exposure of the surface of the phase-shift film 2. That is, overetching is performed by adding only 50% of the proper etching time (overetching time). By performing the over-etching, the verticality of the pattern sidewall of the light-shielding film 3 can be improved.

When the hard mask pattern 4a after the over-etching was observed with a Scanning Electron Microscope (SEM), the edge between the side wall of the pattern and the surface (the surface on the side opposite to the bottom surface of the pattern (the upper surface of the pattern)) was sharp (the angle was not rounded). In addition, the surface of the sidewall of the hard mask pattern 4a is smooth.

Next, using fluorine-based gas (SF) with the light-shielding pattern 3a as a mask, a process of forming a pattern using fluorine-based gas (SF) is performed₆+ He) forms the first pattern (phase shift pattern 2a) on the phase shift film 2 and removes the hard mask pattern 4a at the same time (see fig. 2 d).

Next, a resist film made of a chemical amplification resist for electron beam lithography was formed on the light-shielding pattern 3a by spin coating with a film thickness of 150 nm. Next, a second pattern, which is a pattern to be formed on the light-shielding film (a pattern including a light-shielding belt pattern), is drawn against resist exposure, and a predetermined process such as a development process is further performed, thereby forming a resist pattern 6b having a light-shielding pattern (see fig. 2 (e)).

Next, using chlorine gas (Cl) was performed using the resist pattern 6b as a mask₂) With oxygen (O)₂) Mixed gas (gas flow rate ratio Cl)₂：O₂Dry etching of 4:1) forms a second pattern (light-shielding pattern 3b) in the light-shielding film 3 (see fig. 2 (f)).

Further, the resist pattern 6b is removed and subjected to a predetermined process such as cleaning, thereby obtaining a phase shift mask 200 (see fig. 2 g).

The transfer mask 200 (halftone type phase shift mask) thus obtained was inspected for defects using a mask defect inspection apparatus, and it was confirmed that both the CD accuracy and the line edge roughness of the phase shift pattern 2a satisfied the required levels.

[ evaluation of Pattern transfer Property ]

With respect to the phase shift mask 200 manufactured by the above procedure, a simulation of a transfer image when transferred to a resist film on a semiconductor device by exposure to exposure light having a wavelength of 193nm was performed using the AIMS193 (manufactured by Carl Zeiss). The simulated exposure transfer image was verified, and as a result, the design specifications were fully satisfied. From the results, it is understood that the phase shift mask 200 of embodiment 1 can form a circuit pattern on a semiconductor device with high accuracy in the end even if it is set on a mask stage of an exposure apparatus and exposed to a resist film transferred onto the semiconductor device.

Comparative example 1

[ production of mask blank ]

The hard mask film 4 of comparative example 1 had a silicon (Si) to oxygen (O) content ratio (atomic%) of Si: O of 1:2 (SiO with no oxygen deficiency)₂Film), the mask blank and the transfer mask were manufactured, and the same as in example 1 was performed except for the characteristics of the hard mask film 4 and the film forming method. The following description deals with differences from example 1.

The same procedure as in example 1 was followed until the light-shielding film 3 was formed, and then argon (Ar) gas and oxygen (O) gas were introduced using a silicon (Si) target₂) By performing RF sputtering using gas as a sputtering gas, a hard mask film 4 containing silicon and oxygen was formed on the light-shielding film 3 to a thickness of 15 nm. The composition of the formed hard mask film was determined by XPS, where Si: O was 1:2 (atomic%).

As will be described later, the hard mask film 4 has a lower etching rate with respect to fluorine-based gas than in example 1, and thus it is not considered that the hard mask film can be etched quickly and completely.

It is found that the hard mask film 4 tends to have a relatively high film density (high density), and the content ratio (atomic%) of silicon (Si) and oxygen (O) is Si: O ═ 1:2 (SiO not lacking oxygen)₂A film).

The mask blank of comparative example 1 was obtained with a narrow Si2p spectrum, a narrow N1s spectrum, and a narrow O1s spectrum in the same procedure as in example 1. From the results of the narrow spectrum of Si2p (not shown), the hard mask film 4 of comparative example 1 had the maximum peak at the bond energy exceeding 103.5eV (103.8eV), which means that the existence ratio of Si — O bonds was very high. From the results of the Si2p narrow spectrum (not shown), it was found that the hard mask film 4 of comparative example 1 had a substantially flat waveform with no peak (lower limit of detection or less) at the bond energy between 97 to 100eV, which means that no Si — Si bond was detected in the hard mask film 4.

As is clear from the result of the narrow spectrum of N1s (not shown), the maximum peak of the hard mask film 4 of comparative example 1 is equal to or less than the lower detection limit, and this result means that no atom containing an Si — N bond and bonded to nitrogen is detected in the hard mask film 4 of comparative example 1.

As is clear from the above, the hard mask film 4 of comparative example 1 has a content ratio of silicon (Si) to oxygen (O) of 1:2, and does not satisfy the above condition 1, and the narrow spectrum of Si2p has a maximum peak at a bond energy exceeding 103.5eV (103.8eV), and does not satisfy the above condition 2. The hard mask film 4 of comparative example 1 has a maximum peak of the N1s narrow spectrum of not more than the detection lower limit value, and satisfies only the above condition 3.

As is clear from the results (not shown) of the narrow spectrum of O1s, the hard mask film 4 of comparative example 1 has a maximum peak of bond energy between 532-533 eV, which means that a high oxide (Si-O bond) (SiO) is present at least at a certain ratio or more₂As the main body).

[ production of phase Shift mask ]

Next, a halftone-type phase shift mask 200 was produced in the same manner as in example 1, using the mask blank 100 of comparative example 1. First, HMDS treatment is performed on the surface of the hard mask film 4.

Next, a resist pattern 5a having a first pattern was formed in the same manner as in example 1 (see fig. 2 (a)).

Next, CF was used using the resist pattern 5a as a mask₄The dry etching with gas forms a first pattern (hard mask pattern 4a) on the hard mask film 4 (see fig. 2 (b)).

At this time, it is found that the etching rate of the hard mask film 4 with respect to the fluorine-based gas is smaller than that of example 1, and it is not considered that the hard mask film can be quickly etched with high accuracy.

As a result of calculation of the etching rate of the hard mask film 4 based on the film thickness and the etching time of the hard mask film 4, it was found that the etching rate with respect to the fluorine-based gas was relatively smaller than that of the hard mask film 4 of example 1 described above.

In addition, when the hard mask pattern 4a was observed by a Scanning Electron Microscope (SEM), the surface of the sidewall was not smooth as compared with example 1.

Next, the resist pattern 5a is removed. Then, using chlorine gas (Cl) as a mask, the hard mask pattern 4a was used as a mask₂) With oxygen (O)₂) Mixed gas (gas flow rate ratio Cl)₂：O₂Dry etching (power at bias application of 50W) of 13:1 (power at bias application of 50W)]High-bias etching) of (b), a first pattern (light-shielding pattern 3a) is formed on the light-shielding film 3 (see fig. 2 (c)). At this time, over-etching was performed in the same manner as in example 1.

When the hard mask pattern 4a after the over-etching was observed with a Scanning Electron Microscope (SEM), the edge between the sidewall and the surface of the pattern was sharp (the corner was not rounded). In addition, the surface of the sidewall of the hard mask pattern 4a is not smooth.

Then, a transfer mask 200 (halftone type phase shift mask) was manufactured under the same conditions as in example 1 through the same procedure as in example 1.

The transfer mask 200 (halftone type phase shift mask) of comparative example 1 manufactured was subjected to defect inspection using a mask defect inspection apparatus, and as a result, it was found that the CD accuracy and the line edge roughness of the phase shift pattern 2a did not satisfy the required levels.

Comparative example 2

[ production of mask blank ]

In comparative example 2, the mask blank and the transfer mask were manufactured by forming the hard mask film 4 from a material having a relatively high Si — Si bond content, and the same process as in example 1 was performed except for the characteristics of the hard mask film 4 and the film formation method thereof. The differences from example 1 will be described below.

The same procedure as in example 1 was followed until the light-shielding film 3 was formed, and then oxygen (O) was added using a silicon (Si) target₂) And argon (Ar) gas as a sputtering gas, sputtering,thereby, SiO was formed on the light-shielding film 3 to a thickness of 15nm₂A hard mask film 4 is formed. The composition of the hard mask film 4 of comparative example 2 was determined by XPS, and the composition was 38.5:61.5 (atomic%) of Si: O.

The mask blank of comparative example 2 was obtained with a narrow Si2p spectrum, a narrow N1s spectrum, and a narrow O1s spectrum in the same procedure as in example 1. From the results of the Si2p narrow spectrum (not shown), the hard mask film 4 of comparative example 2 has peaks at a bond energy (99.2eV) of 97eV or more and 100eV or less and at a bond energy (102.7eV) of less than 103 eV.

In addition, it is found that the hard mask film 4 of comparative example 2 has an area intensity of Si — Si bond of half or more to the same degree as that of Si — O bond in a narrow spectrum of Si2p, and both of the Si — O bond and the Si — Si bond are present at a considerable ratio.

[ production of phase Shift mask ]

Next, a halftone-type phase shift mask 200 was produced in the same manner as in example 1, using the mask blank 100 of comparative example 1. First, HMDS treatment is performed on the surface of the hard mask film 4.

Next, a resist pattern 5a having a first pattern was formed in the same manner as in example 1 (see fig. 2 (a)).

Next, CF was used using the resist pattern 5a as a mask₄The dry etching with gas forms a first pattern (hard mask pattern 4a) on the hard mask film 4 (see fig. 2 (b)).

At this time, the etching rate of the hard mask film 4 with respect to the fluorine-based gas is larger than that of the hard mask film 4 of example 1. Therefore, it is understood that the hard mask film 4 can be etched quickly with high accuracy.

Next, the resist pattern 5a is removed. Then, using chlorine gas (Cl) as a mask, the hard mask pattern 4a was used as a mask₂) And oxygen (O)₂) Mixed gas (gas flow rate ratio Cl)₂：O₂Dry etching (power at bias application of 50W) of 13:1 (power at bias application of 50W)]High-bias etching) of (b), a first pattern (light-shielding pattern 3a) is formed on the light-shielding film 3 (see fig. 2 (c)). At this time, over-etching was performed in the same manner as in example 1.

When the hard mask pattern 4a after the over-etching was observed with a Scanning Electron Microscope (SEM), the corners of the edges between the sidewalls and the surface of the pattern were rounded. In addition, the surface of the sidewall of the hard mask pattern 4a is not smooth. From this, it is found that the function as a hard mask tends to be significantly reduced (the etching resistance to chlorine-based gases is significantly reduced, and particularly the etching resistance is further significantly reduced under high-bias etching conditions). Therefore, the light-shielding pattern 3a processed by dry etching using the hard mask pattern 4a as a mask has poor CD accuracy and line edge roughness. In addition, the phase shift pattern 2a processed by dry etching using the light-shielding pattern 3a as a mask also has poor CD accuracy and line edge roughness.

Then, a transfer mask 200 (halftone type phase shift mask) was manufactured under the same conditions as in example 1 through the same procedure as in example 1.

As a result of performing mask defect inspection on the transfer mask 200 (halftone type phase shift mask) of the manufactured comparative example 2, it was found that the CD accuracy and the line edge roughness of the phase shift pattern 2a were not satisfactory.

While the embodiments and examples of the present invention have been specifically described, the technical scope of the present invention is not limited to the embodiments and examples described above, and various modifications can be made without departing from the scope of the present invention.