阅读说明：本技术 掩模坯料、相移掩模及半导体器件的制造方法 (Mask blank, phase shift mask and method for manufacturing semiconductor device ) 是由 桥本雅广 宍户博明 于 2018-05-16 设计创作，主要内容包括：本发明的掩模坯料(100)具备在透光性基板(1)上依次层叠有相移膜(2)和遮光膜(3)的结构,相移膜与遮光膜的层叠结构对于ArF准分子激光的曝光光的光密度为3.5以上,遮光膜具备从透光性基板侧起层叠有下层(31)及上层(32)的结构,下层由铬、氧、氮及碳的总含量为90原子％以上的材料形成,上层由金属及硅的总含量为80原子％以上的材料形成,上层对于曝光光的消光系数k<Sub>U</Sub>大于下层对于曝光光的消光系数k<Sub>L</Sub>。(A mask blank (100) of the present invention has a structure in which a phase shift film (2) and a light-shielding film (3) are laminated in this order on a light-transmitting substrate (1), the laminated structure of the phase shift film and the light-shielding film having an optical density of 3.5 or more with respect to exposure light of an ArF excimer laser, the light-shielding film having a structure in which a lower layer (31) and an upper layer (32) are laminated from the light-transmitting substrate side, the lower layer being formed of a material having a total content of chromium, oxygen, nitrogen, and carbon of 90 atomic% or more, the upper layer being formed of a material having a total content of metal and silicon of 80 atomic% or more, and the upper layer having an extinction coefficient k with respect to the exposure U Greater than lower for exposureExtinction coefficient k of light L 。)

1. A mask blank having a structure in which a phase shift film and a light shielding film are sequentially laminated on a light-transmitting substrate,

the optical density of the laminated structure of the phase shift film and the light-shielding film to the exposure light of an ArF excimer laser is 3.5 or more,

the light-shielding film has a structure in which a lower layer and an upper layer are laminated from the side of the light-transmitting substrate,

the lower layer is formed of a material containing chromium and having a total content of chromium, oxygen, nitrogen and carbon of 90 atomic% or more,

the upper layer is formed of a material containing a metal and silicon, the total content of the metal and silicon being 80 atomic% or more,

an extinction coefficient k of the upper layer to the exposure light_UIs larger than the extinction coefficient k of the lower layer to the exposure light_L。

2. The mask blank according to claim 1, wherein the transmittance of the phase shift film with respect to the exposure light is 1% or more.

3. Mask blank according to claim 1 or 2, wherein the extinction coefficient k of the lower layer_LAn extinction coefficient k of the upper layer of 2.0 or less_UGreater than 2.0.

4. The mask blank according to any one of claims 1 to 3, wherein the upper layer has a refractive index n for the exposure light_ULess than the refractive index n of the lower layer to the exposure light_LWith refractive index n of said upper layer for said exposure light_UDivided by the refractive index n of the lower layer for the exposure light_LAnd the ratio n obtained_U/n_LIs 0.8 or more.

5. According to the claimsThe mask blank according to claim 4, wherein the refractive index n of the lower layer_LIs 2.0 or less, and the refractive index n of the upper layer_ULess than 2.0.

6. The mask blank according to any one of claims 1 to 5, wherein the lower layer is formed of a material having a total content of chromium, oxygen and carbon of 90 atomic% or more.

7. The mask blank according to any one of claims 1 to 6, wherein the upper layer is formed of a material having a total content of tantalum and silicon of 80 atomic% or more.

8. The mask blank according to any one of claims 1 to 7, wherein the phase shift film is formed of a material containing silicon.

9. A phase shift mask having a structure in which a phase shift film having a transfer pattern and a light shielding film having a light shielding tape pattern are sequentially stacked on a light-transmissive substrate,

the optical density of the laminated structure of the phase shift film and the light-shielding film to the exposure light of an ArF excimer laser is 3.5 or more,

the light-shielding film has a structure in which a lower layer and an upper layer are laminated from the side of the light-transmitting substrate,

the lower layer is formed of a material containing chromium and having a total content of chromium, oxygen, nitrogen and carbon of 90 atomic% or more,

the upper layer is formed of a material containing a metal and silicon, the total content of the metal and silicon being 80 atomic% or more,

an extinction coefficient k of the upper layer to the exposure light_UIs larger than the extinction coefficient k of the lower layer to the exposure light_L。

10. The phase shift mask according to claim 9, wherein the transmittance of the phase shift film with respect to the exposure light is 1% or more.

11. According to claim9 or 10, wherein the extinction coefficient k of the lower layer_LAn extinction coefficient k of the upper layer of 2.0 or less_UGreater than 2.0.

12. The phase shift mask according to any one of claims 9 to 11, wherein the upper layer has a refractive index n for the exposure light_ULess than the refractive index n of the lower layer to the exposure light_LWith refractive index n of said upper layer for said exposure light_UDivided by the refractive index n of the lower layer for the exposure light_LAnd the ratio n obtained_U/n_LIs 0.8 or more.

13. The phase shift mask according to claim 12, wherein the refractive index n of the lower layer_LIs 2.0 or less, and the refractive index n of the upper layer_ULess than 2.0.

14. The phase shift mask according to any one of claims 9 to 13, wherein the lower layer is formed of a material having a total content of chromium, oxygen, and carbon of 90 atomic% or more.

15. The phase shift mask according to any one of claims 9 to 14, wherein the upper layer is formed of a material having a total content of tantalum and silicon of 80 atomic% or more.

16. The phase shift mask according to any one of claims 9 to 15, wherein the phase shift film is formed of a material containing silicon.

17. A method for manufacturing a semiconductor device, the method comprising: a process of exposing and transferring the transfer pattern to a resist film on a semiconductor substrate using the phase shift mask according to any one of claims 9 to 16.

Technical Field

The present invention relates to a mask blank for a phase shift mask, and a method for manufacturing a semiconductor device using the phase shift mask.

Background

In general, in a manufacturing process of a semiconductor device, a fine pattern is formed by photolithography. In forming such a fine pattern, a plurality of substrates called transfer masks are generally used. In general, the transfer mask has a fine pattern formed of a thin metal film or the like on a light-transmitting glass substrate. Photolithography is also used for manufacturing the transfer mask.

As a type of transfer mask, a halftone type phase shift mask is known in addition to a conventional binary mask having a light-shielding film pattern made of a chromium-based material on a light-transmissive substrate. The halftone phase shift mask includes a pattern having a phase shift film on a transparent substrate. The phase shift film has a function of transmitting light at an intensity that does not substantially contribute to exposure and causing a given phase difference between the light transmitted through the phase shift film and the light passing through the air at the same distance, thereby generating a so-called phase shift effect.

As disclosed in patent document 1, when a pattern of a transfer mask is transferred onto a resist film on 1 semiconductor wafer by exposure using an exposure apparatus, the pattern of the transfer mask is usually repeatedly transferred by exposure at different positions on the resist film. Further, the repeated exposure transfer of the resist film is performed without providing a space. An aperture is provided in the exposure device so that exposure light is irradiated only to a region (transfer region) of the transfer mask where the transfer pattern is to be formed. However, there is a limit to the precision with which the exposure light is coated (shielded) by the aperture, and it is difficult to avoid light leakage of the exposure light outside the transfer region of the transfer mask. Therefore, when performing exposure transfer on a resist film on a semiconductor wafer using an exposure apparatus, it is required to secure Optical density (OD: Optical Dimension) of a predetermined value or more in an outer peripheral region of a region in a transfer mask where a transfer pattern is to be formed, in order to prevent the resist film from being affected by exposure light transmitted through the outer peripheral region. Generally, the OD is desirably 3 or more (transmittance of about 0.1% or less) in the outer peripheral region of the transfer mask, and at least about 2.8 (transmittance of about 0.16%) is required.

However, the phase shift film of the halftone type phase shift mask has a function of transmitting exposure light at a predetermined transmittance, and it is difficult to ensure a required optical density in the outer peripheral region of the transfer mask only by the phase shift film. Therefore, as disclosed in patent document 1, in the case of a halftone-type phase shift mask, a light-shielding layer (light-shielding band) is laminated on a semi-transparent layer in an outer peripheral region, and the above-mentioned optical density equal to or higher than a predetermined value is ensured by the laminated structure of the semi-transparent layer and the light-shielding layer.

On the other hand, as disclosed in patent document 2, a mask blank having a structure in which a halftone phase shift film containing a metal silicide material, a light-shielding film containing a chromium material, and an etching mask film containing an inorganic material are laminated on a light-transmitting substrate has been known as a mask blank for a halftone phase shift mask. When a phase shift mask is manufactured using this mask blank, first, an etching mask film is patterned by dry etching using a fluorine-based gas, using a resist pattern formed on the surface of the mask blank as a mask. Next, the light-shielding film is patterned by dry etching using a mixed gas of chlorine and oxygen with the etching mask film pattern as a mask, and the phase shift film is patterned by dry etching using a fluorine-based gas with the light-shielding film pattern as a mask.

Disclosure of Invention

Problems to be solved by the invention

In recent years, in an exposure technique using ArF excimer laser light (wavelength 193nm) as exposure light, miniaturization of a transfer pattern has been advanced, and a pattern line width smaller than the wavelength of the exposure light is required. In addition to the ultra-high NA technique (immersion exposure) in which NA (Numerical Aperture) is 1 or more, an optimization technique of applying a light source and a Mask that optimizes the illumination of an exposure apparatus with respect to all patterns on the Mask, that is, smo (source Mask optimization) has been started. An illumination system of an exposure apparatus to which this SMO is applied is complicated, and when exposure light is irradiated to the exposure apparatus with a phase shift mask provided, the exposure light may enter a light shielding film (light shielding zone) of the phase shift mask from a plurality of directions.

The light-shielding performance (optical density) of a conventional light-shielding film is determined on the premise that exposure light transmitted through a phase shift film at a predetermined transmittance enters from a surface of the light-shielding film on the phase shift film side and exits from a surface on the opposite side of the phase shift film. However, it was found that when the phase shift mask is irradiated with the exposure light of the complicated illumination system described above, the exposure light incident from the surface of the light-shielding film on the phase shift film side through the phase shift film is more likely to be emitted from the pattern sidewall of the light-shielding band than in the conventional case. The amount of exposure light (leak light) emitted from the side wall of the pattern is not sufficiently attenuated, and thus a resist film provided on a semiconductor wafer or the like is exposed (though less). When the resist film is exposed to light (though less) in a region where a transfer pattern is to be disposed, CD (Critical Dimension) of a resist pattern formed by developing the transfer pattern exposed in the region is also significantly reduced.

Fig. 3 is an explanatory diagram of a case where the transfer pattern of the phase shift mask is repeatedly transferred 4 times to the resist film on the semiconductor wafer. Image I₁Is an image transferred by 1-time exposure transfer of the transfer pattern of the phase shift mask, image I₂、I₃、I₄The same applies. Image p_1a～p_1eIs a pattern transferred by the same exposure transfer, image p_2a～p_2eImage p_3a～p_3eImage p_4a～p_4eThe same applies. Image S₁、S₂、S₃、S₄Is an image after the light-shielding tape pattern of the phase shift mask is transferred. As shown in fig. 3, the repeated exposure transfer of the resist film of the transfer pattern of the phase shift mask by the exposure device is performed without intervals. Therefore, the shading of adjacent transfer imagesThe light band pattern is repeatedly transferred. S in FIG. 3₁₂、S₁₃、S₂₄、S₃₄Is a region where the transferred images of 2 light-shielding tapes are overlapped and transferred, S₁₂₃₄The transfer images of the 4 light-shielding tapes are overlapped and transferred.

In recent years, miniaturization of semiconductor devices is sometimes remarkable, as shown by an image p in fig. 3_1a～p_1dIn this way, the transfer pattern of the phase shift film is arranged on the light-shielding tape (image S)₁) Is increasing. The arrangement of the plurality of transfer patterns repeatedly transferred on the resist film on the semiconductor wafer is a positional relationship in which adjacent light shielding tape patterns repeat. The transferred region is repeatedly exposed to light by the light shielding tape pattern and used as a cut edge when each chip is cut and separated after being formed on the semiconductor wafer.

In such a case, due to light leakage of exposure light generated by the light-shielding belt, a phenomenon of reduction in CD accuracy is likely to occur when a fine pattern arranged in the vicinity of the light-shielding belt is exposed and transferred to a resist film, and a resist pattern is formed by development or the like. Especially in the resist film region S which receives 4 times of exposure transfer of the light shielding belt pattern₁₂₃₄A fine pattern (a pattern p surrounded by a dotted circle in fig. 3) arranged in the vicinity_1d、p_2c、p_3b、p_4a) The accumulated amount of light leakage tends to increase, which is particularly problematic.

As a method for solving these problems, it is considered to increase the Optical Density (OD) of the light-shielding band by simply increasing the film thickness of the light-shielding film. However, if the film thickness of the light-shielding film is increased, it is necessary to increase the film thickness of a resist pattern (resist film) to be a mask when etching is performed to form a transfer pattern on the light-shielding film. Conventionally, the phase shift film is often formed of a material containing silicon, and the light-shielding film is often formed of a material containing chromium (chromium-based material) having a high etching selectivity with respect to the phase shift film. The light-shielding film containing a chromium-based material is patterned by dry etching using a mixed gas of a chlorine-based gas and an oxygen gas, but the resist film has low resistance to dry etching using a mixed gas of a chlorine-based gas and an oxygen gas. Therefore, if the film thickness of the light-shielding film is increased, it is necessary to increase the film thickness of the resist film significantly, but if a fine pattern is formed on such a resist film, the problem of the resist pattern being distorted or falling off is likely to occur.

On the other hand, as disclosed in patent document 2, by providing a hard mask film made of a material containing silicon on a light-shielding film made of a chromium-based material, the thickness of the resist film can be reduced. However, when a light-shielding film made of a chromium-based material is patterned by dry etching using a mixed gas of a chlorine-based gas and an oxygen gas, etching tends to proceed easily in the direction of the side wall of the pattern. Therefore, when the light-shielding film is subjected to dry etching using a hard mask film having a fine pattern as a mask, if the light-shielding film is thick, the amount of lateral etching tends to increase, and the CD accuracy of the fine pattern formed in the light-shielding film tends to decrease. The reduction in CD accuracy of the fine pattern of the light-shielding film causes a problem in that the CD accuracy of the fine pattern formed on the phase shift film by dry etching using the fine pattern of the light-shielding film as a mask is reduced. Further, there is a problem that the light-shielding film after the patterning is subjected to a cleaning step, and if the light-shielding film is thick, the pattern of the light-shielding film is likely to be distorted during the cleaning.

In order to solve the above-described problems, a first object of the present invention is to provide a mask blank having a structure in which a phase shift film made of a material containing silicon and a light-shielding film including a layer made of a material containing chromium are sequentially stacked on a light-transmissive substrate, wherein the phase shift mask manufactured from the mask blank is installed in an exposure apparatus to which a complicated illumination system such as SMO is applied, and wherein even when a resist film provided on a semiconductor wafer or the like as an object to be transferred is subjected to exposure transfer, the light density can be higher than that of the conventional mask blank due to the stacked structure of the phase shift film and the light-shielding film, and for example, a fine pattern formed on the resist film after development processing has high CD accuracy.

In addition, a second object of the present invention is to provide a mask blank in which the CD accuracy of a fine pattern formed on a light-shielding film by dry etching is high and the occurrence of distortion of the light-shielding film pattern is suppressed.

It is another object of the present invention to provide a phase shift mask manufactured using the mask blank, which can form a light shielding tape having an optical density higher than that of a conventional mask, in which a fine pattern formed on a resist film after development processing has high CD accuracy, even when the phase shift mask is set in an exposure apparatus of a complicated illumination system and is subjected to exposure transfer to the resist film, and which can form a fine pattern on the phase shift film with good accuracy.

Further, it is an object of the present invention to provide a method for manufacturing a semiconductor device using the phase shift mask.

Means for solving the problems

The present invention has the following configuration as a means for solving the above-described problems.

(constitution 1)

A mask blank has a structure in which a phase shift film and a light shielding film are sequentially laminated on a light-transmitting substrate.

The optical density of the laminated structure of the phase shift film and the light-shielding film with respect to exposure light of an ArF excimer laser is 3.5 or more,

the light-shielding film has a structure in which a lower layer and an upper layer are stacked from the light-transmitting substrate side.

The lower layer is formed of a material containing chromium and having a total content of chromium, oxygen, nitrogen and carbon of 90 atomic% or more,

the upper layer is formed of a material containing a metal and silicon, and the total content of the metal and silicon is 80 atomic% or more,

an extinction coefficient k of the upper layer with respect to the exposure light_UIs larger than the extinction coefficient k of the lower layer to the exposure light_L。

(constitution 2)

The mask blank according to configuration 1, wherein the transmittance of the phase shift film with respect to the exposure light is 1% or more.

(constitution 3)

The mask blank according to configuration 1 or 2, wherein the extinction coefficient k of the lower layer_LIs 20 or less, the extinction coefficient k of the upper layer_UGreater than 2.0.

(constitution 4)

The mask blank according to any one of configurations 1 to 3, wherein the upper layer has a refractive index n with respect to the exposure light_UA refractive index n smaller than that of the lower layer with respect to the exposure light_LA refractive index n of the upper layer with respect to the exposure light_UIn addition to the refractive index n of the lower layer with respect to the exposure light_LAnd the ratio n obtained_U/n_LIs 0.8 or more.

(constitution 5)

The mask blank according to configuration 4, wherein the refractive index n of the lower layer_LA refractive index n of 2.0 or less, of the upper layer_ULess than 2.0.

(constitution 6)

The mask blank according to any one of configurations 1 to 5, wherein the lower layer is formed of a material having a total content of chromium, oxygen, and carbon of 90 atomic% or more.

(constitution 7)

The mask blank according to any one of configurations 1 to 6, wherein the upper layer is formed of a material having a total content of tantalum and silicon of 80 atomic% or more.

(constitution 8)

The mask blank according to any one of configurations 1 to 7, wherein the phase shift film is formed of a material containing silicon.

(constitution 9)

A phase shift mask having a structure in which a phase shift film having a transfer pattern and a light shielding film having a light shielding tape pattern are sequentially stacked on a light-transmissive substrate,

the optical density of the laminated structure of the phase shift film and the light-shielding film with respect to exposure light of an ArF excimer laser is 3.5 or more,

the light-shielding film has a structure in which a lower layer and an upper layer are laminated from the side of the light-transmitting substrate,

the lower layer is formed of a material containing chromium and having a total content of chromium, oxygen, nitrogen and carbon of 90 atomic% or more,

the upper layer is formed of a material containing a metal and silicon, and the total content of the metal and silicon is 80 atomic% or more,

an extinction coefficient k of the upper layer with respect to the exposure light_UIs larger than the extinction coefficient k of the lower layer to the exposure light_L。

(constitution 10)

The phase shift mask according to claim 9, wherein the transmittance of the phase shift film with respect to the exposure light is 1% or more.

(constitution 11)

The phase shift mask according to constitution 9 or 10, wherein the extinction coefficient k of the lower layer_LAn extinction coefficient k of 2.0 or less, of the upper layer_UGreater than 2.0.

(constitution 12)

The phase shift mask according to any one of configurations 9 to 11, wherein the upper layer has a refractive index n with respect to the exposure light_UA refractive index n smaller than that of the lower layer with respect to the exposure light_LA refractive index n of the upper layer with respect to the exposure light_UIn addition to the refractive index n of the lower layer with respect to the exposure light_LAnd the ratio n obtained_U/n_LIs 0.8 or more.

(constitution 13)

The phase shift mask according to constitution 12, wherein the refractive index n of the lower layer_LA refractive index n of 2.0 or less, of the upper layer_ULess than 2.0.

(constitution 14)

The phase shift mask according to any one of constitutions 9 to 13, wherein the lower layer is formed of a material having a total content of chromium, oxygen and carbon of 90 atomic% or more.

(constitution 15)

The phase shift mask according to any one of constitutions 9 to 14, wherein the upper layer is formed of a material having a total content of tantalum and silicon of 80 atomic% or more.

(constitution 16)

The phase shift mask according to any one of configurations 9 to 15, wherein the phase shift film is formed of a material containing silicon.

(constitution 17)

A method for manufacturing a semiconductor device, the method comprising: a step of exposing and transferring the transfer pattern to a resist film on a semiconductor substrate using the phase shift mask described in any one of constitutions 9 to 16.

ADVANTAGEOUS EFFECTS OF INVENTION

Since the mask blank of the present invention has a laminated structure of a phase shift film and a light shielding film, which has a high optical density suitable for SMO such that the optical density with respect to exposure light of ArF excimer laser light is 3.5 or more, CD accuracy of a fine pattern formed on a resist film after development processing can be improved even when the phase shift mask manufactured using the mask blank is installed in an exposure apparatus using a complicated illumination system such as SMO and the resist film of a transfer target is subjected to exposure transfer.

In addition, when the mask blank of the present invention forms a fine pattern on the light-shielding film by dry etching, the formed fine pattern has high CD accuracy, and the formed fine pattern of the light-shielding film can sufficiently suppress distortion due to cleaning or the like.

Since the phase shift mask of the present invention is manufactured using the mask blank of the present invention, the CD accuracy of a fine pattern formed on a resist film after development processing can be improved even when the phase shift mask is installed in an exposure apparatus using a complicated illumination system such as SMO and the resist film of an object to be transferred is subjected to exposure transfer.

In addition, since a phase shift mask is manufactured using the mask blank of the present invention, the phase shift mask of the present invention can form a fine pattern on a phase shift film with good accuracy.

In addition, the method for manufacturing a semiconductor device using the phase shift mask of the present invention can transfer a fine pattern to a resist film on a semiconductor wafer with good CD accuracy.

Drawings

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

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

Fig. 3 is a schematic view showing the arrangement of each transfer pattern when the transfer pattern of the phase shift mask is repeatedly exposed and transferred to the resist film.

Description of the symbols

1 light-transmitting substrate

2 phase shift film

2a phase shift pattern

3 light-shielding film

31 lower layer

32 upper layer

3b light-shielding pattern

31a, 31b lower layer pattern

32a, 32b upper layer pattern

4a, 5b resist pattern

100 mask blank

200 phase shift mask

Detailed Description

First, the completion of the present invention will be explained. The present inventors have studied the optical density of a desired laminated structure of a phase shift film and a light-shielding film in order that a fine pattern formed on a resist film after development treatment has high CD accuracy even when the phase shift mask is installed in an exposure apparatus using a complicated illumination system such as SMO and the resist film installed on a semiconductor wafer or the like as an object to be transferred is subjected to exposure transfer. As a result, it was found that the optical density (hereinafter, simply referred to as optical density) of the laminated structure of the phase shift film and the light-shielding film against exposure light of ArF excimer laser light (hereinafter, referred to as ArF exposure light) must be 3.5 or more.

Next, the transmittance of the phase shift film with respect to ArF exposure light was further investigated assuming that the transmittance is 6% (about 1.2 in terms of optical density), which is a widely used transmittance. In this case, the light density of the light-shielding film to ArF exposure light must be 2.3 or more. Attempts have been made to form a light-shielding film having an optical density of 2.3 or more from a chromium-based material. When attempting to increase the film thickness of the light-shielding film to an optical density of 2.3 or more, it is difficult to form a fine pattern on the light-shielding film by dry etching because the thickness of the resist pattern needs to be increased significantly. In addition, a hard mask film made of a silicon-based material is provided on the light-shielding film, and dry etching is performed using the hard mask film having a fine pattern formed thereon as a mask, thereby forming a fine pattern on the light-shielding film. However, it was found that the amount of lateral etching generated when forming a fine pattern on the light-shielding film was large, and the CD accuracy of the fine pattern formed on the light-shielding film was low. In addition, when cleaning is performed after forming a fine pattern on the light-shielding film, a phenomenon of pattern separation of the light-shielding film occurs, and it is difficult to form a fine pattern on the light-shielding film with good accuracy even by this method.

The optical density per unit film thickness of the thin film of chromium-based material tends to increase as the chromium content increases. Therefore, it was confirmed whether a light-shielding film can be formed from a material having a very high chromium content, such that the optical density is 2.3 or more, and a hard mask film of a silicon-based material is laminated on the light-shielding film to form a fine pattern on the light-shielding film. However, as a result, the etching rate of the light-shielding film by dry etching using a mixed gas of a chlorine-based gas and an oxygen gas is very slow, and the CD uniformity in the surface of the pattern formed on the light-shielding film is low. As a result of these studies, it was found that it was difficult to form a light-shielding film having an optical density of 2.3 or more only with a chromium-based material in practical use.

Therefore, attempts have been made to form the light-shielding film as a laminated structure of a lower layer of a chromium-based material and an upper layer of a metal silicide-based material. By forming the lower layer of the light-shielding film on the phase shift film side with a chromium-based material, it is possible to have high etching resistance to dry etching with a fluorine-based gas performed when forming a fine pattern on the phase shift film, and to maintain the function as a hard mask. Further, the phase shift film has high etching resistance to dry etching by a mixed gas of a chlorine-based gas and an oxygen gas performed when the light-shielding film is removed, and therefore, the influence on the phase shift film when the light-shielding film is removed can be reduced. On the other hand, by forming the upper layer of the light-shielding film from a metal silicide material, dry etching using a mixed gas of a chlorine-based gas and an oxygen gas performed when forming a fine pattern on the lower layer of the light-shielding film can be highly resistant to etching, and can function as a hard mask. Further, the upper layer of the light-shielding film can be removed simultaneously by dry etching with a fluorine-based gas performed when forming a fine pattern on the phase shift film.

The lower layer of the light-shielding film preferably does not contain an element (such as silicon) that significantly reduces the etching rate in dry etching using a mixed gas of a chlorine-based gas and an oxygen gas. In view of this, the lower layer of the light-shielding film is formed of a material containing chromium and having a total content of chromium, oxygen, nitrogen, and carbon of 90 atomic% or more. In this case, it is difficult to increase the chromium content in the chromium-based material forming the lower layer of the light-shielding film and to increase the extinction coefficient k of the lower layer against ArF exposure light_L(hereinafter abbreviated as extinction coefficient k)_L. ) There are also limitations. In the above case, the large amount of oxygen is effective for increasing the etching rate of the thin film of chromium-based material in dry etching using a mixed gas of chlorine-based gas and oxygen gas, but oxygen is a factor for greatly reducing the extinction coefficient k of the thin film.

Conventionally, in consideration of having an antireflection function, a material having an extinction coefficient k smaller than that of a lower layer is often used for an upper layer of a light-shielding film. However, due to the recent improvement in the performance of exposure apparatuses, the restriction of the surface reflectance in the region outside the transfer pattern region (including the region where the light-shielding tape is formed) has started to be relaxed. Therefore, the extinction coefficient k of the upper layer of the light-shielding film is set to_UExtinction coefficient k greater than that of the lower layer_LSuch a configuration.

When patterning a lower layer of a chromium-based material by dry etching using a mixed gas of a chlorine-based gas and an oxygen gas, an upper layer of a light-shielding film is required to function as a hard mask. In the conventional hard mask film made of silicon-based material, it is also important to improve the etching selectivity of the thin film made of chromium-based material, and a silicon material containing relatively large amounts of oxygen and nitrogen is used.

In the present invention, the contents of oxygen and nitrogen were made smaller in the upper layer of the metal silicide material than in the conventional art, and the etching selectivity to dry etching using a mixed gas of a chlorine-based gas and an oxygen gas was verified between the upper layer and the lower layer of the chromium material. As a result, it was found that even if the upper layer of the metal silicide-based material substantially containing no oxygen and nitrogen (but the surface layer in contact with the atmosphere is oxidized), dry etching is performed by using a mixed gas of a chlorine-based gas and an oxygen gasWhen the lower layer of the chromium-based material is patterned, the upper layer can sufficiently function as a hard mask. In order to suppress an increase in the overall film thickness of the light-shielding film by stacking the upper layers, it is necessary to sufficiently increase the extinction coefficient k of the upper layer_U. According to these studies, the upper layer of the light-shielding film is formed of a material containing metal and silicon, and the total content of metal and silicon is 80 atomic%.

The mask blank of the present invention has been completed based on the results of the above intensive studies. Specifically, the mask blank has a structure in which a phase shift film and a light-shielding film are sequentially laminated on a light-transmissive substrate, the laminated structure of the phase shift film and the light-shielding film has an optical density of 3.5 or more with respect to exposure light of an ArF excimer laser, the light-shielding film has a structure in which a lower layer and an upper layer are laminated from the light-transmissive substrate side, the lower layer is formed from a material containing chromium and having a total content of chromium, oxygen, nitrogen, and carbon of 90 atomic% or more, the upper layer is formed from a material containing metal and silicon and having a total content of metal and silicon of 80 atomic% or more, and the upper layer has an extinction coefficient k with respect to the exposure light_UIs larger than the extinction coefficient k of the lower layer to the exposure light_L。

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

Mask blank

Fig. 1 shows a schematic configuration of an embodiment of a mask blank. The mask blank 100 shown in fig. 1 is configured such that: on one main surface of the light-transmitting substrate 1, a phase shift film 2, a lower layer 31 of a light-shielding film 3, and an upper layer 32 of the light-shielding film 3 are laminated in this order. The mask blank 100 may have a structure in which a resist film is laminated on the upper layer 32 as necessary. For the above reasons, the mask blank 100 is required to have a laminated structure of at least the phase shift film 2 and the light shielding film 3, and to have an optical density of 3.5 or more with respect to ArF exposure light. The optical density of the laminated structure of the phase shift film 2 and the light shielding film 3 of the mask blank 100 with respect to ArF exposure light is preferably 3.8 or more, and more preferably 4.0 or more. 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, low thermal expansion glass (SiO)₂-TiO₂Glass, etc.), other various glass substrates. In particular, a substrate using synthetic quartz glass has high transparency to ArF exposure light, and therefore can be suitably used as the transparent substrate 1 of the mask blank 100.

The exposure step in lithography referred to herein is an exposure step in lithography using a phase shift mask produced using the mask blank 100, and the exposure light is an ArF excimer laser (wavelength: 193nm) used in the exposure step.

[ phase-shift film ]

The phase shift film 2 has the following functions: the ArF exposure light is made to transmit at an intensity that does not substantially contribute to the exposure, and a given phase difference is generated between the transmitted ArF exposure light and the exposure light passing through the air at the same distance as the thickness of the phase shift film 2. Specifically, by patterning the phase shift film 2, a portion where the phase shift film 2 remains and a portion where the phase shift film 2 does not remain are formed, and the phase of light transmitted through the phase shift film 2 (light of an intensity that does not substantially contribute to exposure) is substantially inverted with respect to exposure light transmitted through a portion where the phase shift film 2 does not remain. In this way, the light beams in the regions surrounding each other are cancelled out by the diffraction phenomenon, so that the light intensity at the pattern boundary portion of the phase shift film 2 becomes almost zero, and an effect of improving the contrast, i.e., the resolution, of the pattern boundary portion, that is, a so-called phase shift effect is obtained.

The transmittance of the phase shift film 2 to ArF exposure light is preferably 1% or more, and more preferably 2% or more. The transmittance of the phase shift film 2 to ArF exposure light is preferably 35% or less, and more preferably 30% or less. The phase difference of the phase shift film 2 is preferably 150 degrees or more, and more preferably 160 degrees or more. The above phase difference of the phase shift film 2 is preferably 200 degrees or less, and more preferably 190 degrees or less.

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. The phase shift film 2 can be patterned by dry etching using a fluorine-based gas, and has sufficient etching selectivity for the lower layer 31 of a Cr-based material constituting the light-shielding film 3 described later.

The phase shift film 2 is preferably formed of: the material containing silicon and nitrogen or the material containing 1 or more elements selected from a semimetal element and a nonmetal element is used as the material containing silicon and nitrogen. The phase shift film 2 may contain any semimetal element in addition to silicon and nitrogen. The semimetal element preferably contains 1 or more elements selected from boron (B), germanium (Ge), antimony (Sb), and tellurium (Te), since the conductivity of silicon used as a sputtering target can be expected. The phase shift film 2 may contain any non-metallic element in addition to silicon and nitrogen. Here, the nonmetal elements in the present invention include nonmetal elements in a narrow sense (nitrogen (N), carbon (C), oxygen (O), phosphorus (P), sulfur (S), selenium (Se)), halogen, and rare gas. Among the nonmetal elements, 1 or more elements selected from carbon, fluorine (F) and hydrogen (H) are preferably contained.

The phase shift film 2 may contain a rare gas (also referred to as rare gas, hereinafter, the same as in the present specification). The rare gas is an element which exists in the film forming chamber when the phase shift film 2 is formed by reactive sputtering, and which can increase the film forming speed and improve productivity. The rare gas is converted into plasma and collides with the target, whereby target constituent elements are ejected from the target and reach the transparent substrate 1, and in the process, the reactive gas is introduced and adheres to the transparent substrate 1, thereby forming the phase shift film 2 on the transparent substrate 1. During the period from when the target constituent element flies out from the target to when the target constituent element adheres to the transparent substrate 1, a small amount of rare gas is introduced into the film forming chamber. As a rare gas necessary for the reactive sputtering, argon (Ar), krypton (Kr), and xenon (Xe) are preferably cited. In order to relax the stress of the phase shift film 2, helium (He) or neon (Ne) having a small atomic weight may be actively introduced into the phase shift film.

The phase shift film 2 may further contain a metal element if it can be patterned by dry etching using a fluorine-based gas. Examples of the metal element to be contained include 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), and aluminum (Al).

The thickness of the phase shift film 2 is preferably 90nm or less. When the thickness of the phase shift film 2 is larger than 90nm, the time required for forming a pattern by dry etching using a fluorine-based gas becomes long. The thickness of the phase shift film 2 is more preferably 80nm or less. On the other hand, the thickness of the phase shift film 2 is preferably 40nm or more. If the thickness of the phase shift film 2 is less than 40nm, there is a concern that a given transmittance and phase difference required as a phase shift film cannot be obtained.

[ light-shielding film ]

The light-shielding film 3 has a structure in which a lower layer 31 and an upper layer 32 are stacked in this order from the phase shift film 2 side. The lower layer 31 is formed of a material containing chromium and having a total content of chromium, oxygen, nitrogen, and carbon of 90 atomic% or more. The lower layer 31 is preferably formed of a material having a total content of chromium, oxygen, nitrogen, and carbon of 95 atomic% or more, and more preferably formed of a material having a total content of chromium, oxygen, nitrogen, and carbon of 98 atomic% or more. This is because, in order to increase the etching rate in dry etching using a mixed gas of a chlorine-based gas and an oxygen gas, it is preferable to reduce the content of an element other than the above (particularly, silicon).

The lower layer 31 may contain a metal element, a semimetal element, and a nonmetal element other than the above constituent elements as long as the total content range is satisfied. The metal element in this case includes molybdenum, indium, tin, and the like. Examples of the semimetal element in this case include boron and germanium. Examples of the nonmetal elements in this case include nonmetal elements (phosphorus, sulfur, selenium) in a narrow sense, halogens (fluorine, chlorine, etc.), and rare gases (helium, neon, argon, krypton, xenon, etc.). In particular, the rare gas is an element which is introduced into the film in a small amount when the lower layer 31 is formed by a sputtering method, and may be an element which is advantageous if it is positively contained in the layer. However, the content of silicon in the lower layer 31 is required to be 3 atomic% or less, preferably 1 atomic% or less, and more preferably a detection limit value or less.

Preferably, the lower layer 31 is formed of a material containing chromium and having a total content of chromium, oxygen, and carbon of 90 atomic% or more. The lower layer 31 is preferably formed of a material having a total content of chromium, oxygen, and carbon of 95 atomic% or more, and more preferably formed of a material having a total content of chromium, oxygen, and carbon of 98 atomic% or more. As the nitrogen content in the lower layer 31 increases, the etching rate for dry etching using a mixed gas of a chlorine-based gas and an oxygen gas increases, but the amount of lateral etching also increases. Considering that the etching rate of dry etching using a mixed gas of a chlorine-based gas and an oxygen gas is not faster than that in the case where oxygen is contained in the lower layer 31, it can be said that the nitrogen content in the lower layer 31 is preferably small. The nitrogen content of lower layer 31 is preferably less than 10 atomic%, more preferably 5 atomic% or less, and still more preferably 2 atomic% or less. The lower layer 31 includes a system substantially composed of chromium, oxygen, and carbon and substantially containing no nitrogen.

The chromium content of the lower layer 31 is preferably 50 atomic% or more. This is because a material having a high optical density is selected as the upper layer 32 of the light-shielding film 3, but it is preferable that the lower layer 31 also ensure a certain degree of optical density. In addition, this is also for suppressing lateral etching that occurs when the lower layer 31 is patterned by dry etching. On the other hand, the chromium content of the lower layer 31 is preferably 80 at% or less, and more preferably 75 at% or less. This is to ensure a sufficient etching rate when patterning the light-shielding film 3 by dry etching.

The oxygen content of lower layer 31 is preferably 10 atomic% or more, and more preferably 15 atomic% or more. This is because a sufficient etching rate is ensured when patterning the light-shielding film 3 by dry etching. On the other hand, the oxygen content of the lower layer 31 is preferably 50 atomic% or less, more preferably 40 atomic% or less, and further preferably 35 atomic% or less. This is to ensure a certain degree of optical density also in the lower layer 31, as described above. In addition, this is to suppress lateral etching that occurs when the lower layer 31 is patterned by dry etching.

The carbon content of lower layer 31 is preferably 10 atomic% or more. This is to suppress lateral etching that occurs when the lower layer 31 is patterned by dry etching. On the other hand, the carbon content of the lower layer 31 is preferably 30 at% or less, more preferably 25 at% or less, and still more preferably 20 at% or less. This is to ensure a sufficient etching rate when patterning the light-shielding film 3 by dry etching. The lower layer 31 preferably has a difference in the film thickness direction of less than 10% in the content of each element constituting the lower layer 31. This is to reduce variation in the etching rate in the film thickness direction when patterning lower layer 31 by dry etching.

The thickness of the lower layer 31 is preferably greater than 15nm, more preferably 18nm or more, and still more preferably 20nm or more. On the other hand, the thickness of the lower layer 31 is preferably 60nm or less, more preferably 50nm or less, and further preferably 45nm or less. Although the light-shielding film 3 is formed of a material having a high optical density as the upper layer 32, there is a limit to increase the degree of contribution of the upper layer 32 to the optical density required for the entire light-shielding film 3. Therefore, the lower layer 31 also needs to secure a certain degree of optical density. In addition, the lower layer 31 needs to have a higher etching rate for dry etching using a mixed gas of a chlorine-based gas and an oxygen gas, and therefore, there is a limit to the improvement of the light shielding performance. Therefore, the lower layer 31 needs to have a predetermined thickness or more. On the other hand, if the thickness of the lower layer 31 is excessively increased, it becomes difficult to suppress the occurrence of lateral etching. The thickness range of the lower layer 31 is derived in consideration of these limitations.

The upper layer 32 is formed of a material containing metal and silicon, and the total content of metal and silicon is 80 atomic% or more. The upper layer 32 is preferably formed of a material having a total content of metal and silicon of 85 atomic% or more, and more preferably a material having a total content of metal and silicon of 90 atomic% or more. Of the elements constituting the upper layer 32, metal and silicon are elements that improve the light-shielding performance of the upper layer 32 against ArF exposure light. As described above, it was found that even if the total content of the metal and silicon in the upper layer 32 is increased, the dry etching using a mixed gas of a chlorine-based gas and an oxygen gas performed when forming a fine pattern in the lower layer 31 has high resistance and can function as a hard mask. On the other hand, since the surface of the upper layer 32 opposite to the phase shift film 2 is in contact with the atmosphere, the surface layer of the surface is easily oxidized. Therefore, it is difficult to form the entire upper layer 32 only from metal and silicon. On the other hand, the upper layer 32 is desired to have higher light shielding performance than the lower layer 31. In view of the above, the upper layer 32 is required to be formed of a material having a total content of metal and silicon of 80 atomic% or more, preferably 85 atomic% or more, and more preferably 90 atomic% or more, on average, over the entire layer.

The metal element contained In the upper layer 32 is preferably 1 or more metal elements selected from molybdenum (Mo), tungsten (W), titanium (Ti), tantalum (Ta), zirconium (Zr), hafnium (Hf), niobium (Nb), vanadium (V), cobalt (Co), chromium (Cr), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), indium (In), tin (Sn), and aluminum (Al). The metal element contained in the upper layer 32 is more preferably tantalum. Tantalum is an element having a large atomic weight and high light shielding performance, and has high resistance to a cleaning liquid used in a cleaning step performed in a process of manufacturing a phase shift mask from a mask blank, and a cleaning liquid used in cleaning a phase shift mask. The upper layer 32 is preferably formed of a material having a total content of tantalum and silicon of 80 atomic% or more, more preferably 85 atomic% or more, and still more preferably 90 atomic% or more.

The upper layer 32 may contain a semimetal element and a nonmetal element other than the above constituent elements as long as the total content range is satisfied. Examples of the semimetal element in this case include boron and germanium. Examples of the nonmetal elements in this case include nonmetal elements in a narrow sense (oxygen, nitrogen, carbon, phosphorus, sulfur, selenium), halogens (fluorine, chlorine, and the like), and rare gases (helium, neon, argon, krypton, xenon, and the like). In particular, the rare gas is an element which is introduced into the film in a small amount when the upper layer 32 is formed by a sputtering method, and is also an element which may be advantageous if it is positively contained in the layer.

The upper layer 32 preferably has a ratio of the metal content [ atomic% ] divided by the total metal and silicon content [ atomic% ] (i.e., the ratio of the metal content M [ atomic% ] where the total metal and silicon content [ M + Si ] [ atomic% ] in the upper layer 32 is taken as 100 is expressed by [% ]. hereinafter, the M/[ M + Si ] ratio) of 5% or more, more preferably 10% or more, and still more preferably 15% or more. In addition, the ratio of M/[ M + Si ] of the upper layer 32 is preferably 60% or less, more preferably 55% or less, and still more preferably 50% or less. In a thin film of a metal silicide type material, light shielding performance (optical density) tends to increase as the content ratio of metal and silicon approaches a stoichiometrically stable ratio in many cases. In the case of a thin film of a metal silicide type material, the metal: the ratio of silicon to 1:2 is often stoichiometrically stable, and the above-described ratio of M/[ M + Si ] of the upper layer 32 is obtained in consideration of this tendency.

The thickness of the upper layer 32 is preferably 5nm or more, more preferably 7nm or more, and still more preferably 10nm or more. On the other hand, the thickness of the upper layer 32 is preferably 40nm or less, more preferably 35nm or less, and further preferably 30nm or less. The contribution degree of the upper layer 32 to the optical density required for the entire light-shielding film 3 must be higher than that of the lower layer 31. In addition, there is a limit to the improvement of the optical density per unit film thickness of the upper layer 32. On the other hand, the upper layer 32 must be capable of forming a fine pattern by dry etching using the resist film on which the fine pattern is formed as a mask, and therefore there is a limit to the increase in the thickness of the upper layer 32. The thickness range of the upper layer 32 is derived in consideration of these limitations. The upper layer 32 is preferably thinner than the lower layer 31.

The upper layer 32 is formed into a fine pattern by dry etching using a resist film formed with a fine pattern as a mask, but the surface of the upper layer 32 tends to have low adhesion to a resist film made of an organic material. Therefore, it is preferable to perform HMDS (Hexamethyldisilazane or hexamethylisilizane) treatment on the surface of the upper layer 32 to improve the adhesion of the surface.

For the above reasons, the extinction coefficient k of the upper layer 32 of the light-shielding film 3 is required_UGreater than the extinction coefficient k of the lower layer 31_L. Extinction coefficient k of lower layer 31_LPreferably 2.00 or less, more preferably 1.95 or less, and further preferably 1.90 or less. In addition, the extinction coefficient k of the lower layer 31_LPreferably 1.20 or more, more preferably 1.25 or more, and further preferably 1.30 or more. In contrast, the extinction coefficient k of the upper layer 32_UPreferably, it is more than 2.00, more preferably 2.10 or more, and further preferably 2.20 or more. In addition, the extinction coefficient k of the upper layer 32_UPreferably 3.20 or less, more preferably 3.10 or less, and further preferably 3.00 or less.

The phase shift film 2 must have both a function of transmitting the exposure light to be transmitted at a predetermined transmittance and a function of generating a predetermined phase difference. Since the phase shift film 2 is required to have a thinner film thickness to realize these functions, the phase shift film 2 is often formed of a material having a large refractive index n. On the other hand, in the above case, the lower layer 31 of the light-shielding film 3 contains a relatively large amount of chromium and a small amount of nitrogen, and nitrogen is an element which tends to increase the refractive index n of the material by being contained in the material. Therefore, the refractive index n of the lower layer 31 is smaller than that of the phase shift film 2. On the other hand, as described above, the upper layer 32 of the light-shielding film 3 is required to have a significantly improved light-shielding performance, and therefore, it is desirable that the nitrogen content be lower than that of the lower layer 31. In view of the above, the mask blank 100 has a laminated structure in which the refractive indices n of the phase shift film 2, the lower layer 31, and the upper layer 32 decrease in this order.

In general, in a structure in which a film having a large refractive index n and a film having a small refractive index n are stacked, when light passing through the inside of the film having a large refractive index n enters an interface between the film having a large refractive index n and the film having a small refractive index at a predetermined incident angle from a direction perpendicular to the interface, the light enters the film having a small refractive index n from the interface at an exit angle larger than the incident angle. In addition, the larger the difference in refractive index between a film having a large refractive index n and a film having a small refractive index n is, the larger the difference between the incident angle and the exit angle is. Therefore, when the exposure light traveling obliquely at a predetermined angle from the direction perpendicular to the interface of the phase shift film 2 enters the lower layer 31 of the light shielding film 3 from the phase shift film 2, the angle of inclination from the direction perpendicular to the interface is increased. When the exposure light entering the lower layer 31 enters the upper layer 32, the angle inclined from the direction perpendicular to the interface is further increased.

When a light-shielding zone is formed on the light-shielding film 3, when exposure light having a complicated irradiation angle due to SMO travels from the lower layer 31 to the upper layer 32, the light is easily emitted as leak light directly from the side wall of the upper layer 32 where the light-shielding zone is formed without being sufficiently attenuated by the increase in the angle inclined from the direction perpendicular to the interface. In order to reduce light leakage due to this phenomenon, the refractive index n of the upper layer 32 is set_ULess than the refractive index n of the lower layer 31_L(i.e., using the refractive index n of the upper layer 32_UWith the exception of the refractive index n of the following layer 31_LTo obtainTo a ratio n_U/n_LLess than 1.0) and the refractive index n of the upper layer 32 to be used_UWith the exception of the refractive index n of the following layer 31_LAnd the ratio n obtained_U/n_LIt is preferably 0.8 or more. The refractive index n of the upper layer 32 is used_UWith the exception of the refractive index n of the following layer 31_LAnd the ratio n obtained_U/n_LPreferably 0.85 or more, and more preferably 0.9 or more.

For the reasons described above, the refractive index n of the lower layer 31_LPreferably 2.00 or less, more preferably 1.98 or less, and still more preferably 1.95 or less. In addition, the refractive index n of the lower layer 31_LPreferably 1.45 or more, more preferably 1.50 or more, and further preferably 1.55 or more. In contrast, the refractive index n of the upper layer 32_UPreferably less than 2.00, more preferably 1.95 or less, and further preferably 1.90 or less. In addition, the refractive index n of the upper layer 32_UPreferably 1.30 or more, more preferably 1.35 or more, and further preferably 1.40 or more.

In the exposure step of lithography, in order to prevent a failure of exposure transfer due to reflection of ArF exposure light, it is desirable that the surface reflectance of the exposure light on both main surfaces of the phase shift mask is not excessively high. In particular, it is desirable that the light shielding film irradiated with the reflected light of the exposure light from the reduction optical system of the exposure apparatus has a reflectance of, for example, 60% or less (preferably 55% or less) on the front surface side (the surface farthest from the transparent substrate). This is to suppress stray light generated by multiple reflections between the surface of the light-shielding film and the lens of the reduction optical system.

The thickness of the laminated structure of the lower layer 31 and the upper layer 32 of the light-shielding film 3 is preferably 80nm or less, more preferably 75nm or less, and still more preferably 70nm or less. The thickness of the laminated structure of the lower layer 31 and the upper layer 32 of the light-shielding film 3 is preferably 30nm or more, more preferably 35nm or more, and still more preferably 40nm or more. When the entire film thickness of the light-shielding film 3 is too thick, it is difficult to form a fine pattern on the light-shielding film 3 with high accuracy. On the other hand, if the overall film thickness of the light-shielding film 3 is too thin, it is difficult to satisfy the optical density required for the light-shielding film 3.

The phase shift film 2, the lower layer 31 of the light-shielding film 3, and the upper layer 32 can be formed by sputtering. As the sputtering, a Direct Current (DC) power supply, a high frequency (RF) power supply, a magnetron sputtering system, or a normal system may be used. DC sputtering is preferable in terms of mechanism simplicity. Further, the use of a magnetron is preferable in terms of a faster film formation rate and improved productivity. The film forming apparatus may be of a tandem (inline) type or a single-wafer type.

[ resist film ]

In the mask blank 100, a resist film of an organic material is preferably formed in a film thickness of 100nm or less in contact with the surface of the upper layer 32 of the light-shielding film 3. In this case, it is preferable to apply the HMDS treatment to the surface of the upper layer 32 and then form a resist film. The upper layer 32 is formed of a material that can form a fine pattern by dry etching using fluorine gas. Since the upper layer 32 functions as a hard mask in dry etching using a mixed gas of a chlorine-based gas and an oxygen gas performed when forming a fine pattern on the lower layer 31, a fine pattern can be formed on the light-shielding film 3 even if the resist film is 100nm or less. 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.

The mask blank 100 described above has a laminated structure of the phase shift film 2 and the light shielding film 3, and has a high optical density suitable for SMO, such that the optical density with respect to exposure light of ArF excimer laser light is 3.5 or more. Therefore, even when the phase shift mask manufactured by the mask blank 100 is installed in an exposure apparatus using a complicated illumination system such as SMO and the resist film of the transfer target is subjected to exposure transfer, the CD accuracy of the fine pattern formed on the resist film after the development process can be improved. In addition, in the mask blank 100, when a fine pattern is formed on the light-shielding film 3 by dry etching, the formed fine pattern has high CD accuracy, and the fine pattern of the light-shielding film 3 formed can be sufficiently suppressed from being distorted by cleaning or the like.

Method for manufacturing 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, an annealing treatment at a predetermined heating temperature is performed as a post-treatment. Next, the lower layer 31 of the light-shielding film 3 is formed on the phase shift film 2 by sputtering. Then, the upper layer 32 is formed on the lower layer 31 by sputtering. In the deposition of each layer by the sputtering method, deposition is performed using a sputtering target containing a material constituting each layer at a predetermined composition ratio and a sputtering gas, and further using a mixed gas of the above-described rare gas and a reactive gas as a sputtering gas as necessary. When the mask blank 100 has a resist film, the HMDS treatment is performed on the surface of the upper layer 32 as needed. Then, a resist film is formed on the surface of the upper layer 32 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 and phase shift mask

Next, a method of manufacturing a halftone phase shift mask using the mask blank 100 having the configuration shown in fig. 1 will be described with reference to a schematic sectional view of a phase shift mask manufacturing process shown in fig. 2.

First, HMDS treatment is performed on the surface of the upper layer 32 of the light shielding film 3 in the mask blank 100. Next, a resist film is formed on the HMDS-treated upper layer 32 by spin coating. Next, the resist film is exposed by an electron beam to draw a 1 st pattern (phase shift pattern, transfer 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) process, development process, post bake (post bake) process, and the like, to form a 1 st pattern (phase shift pattern) (resist pattern 4a) on the resist film (see fig. 2 (a)). The 1 st pattern after the exposure drawing is optimized by SMO.

Next, dry etching of the upper layer 32 of the light-shielding film 3 is performed using a fluorine-based gas with the resist pattern 4a as a mask, and the 1 st pattern (upper layer pattern 32a) is formed on the upper layer 32 (see fig. 2 (b)). Then, the resist pattern 4a is removed (see fig. 2 c). Here, the lower layer 31 of the light-shielding film 3 may be directly dry-etched in a state where the resist pattern 4a remains without being removed. In this case, the resist pattern 4a disappears during dry etching of the lower layer 31.

Next, high-bias etching using a mixed gas of a chlorine-based gas and an oxygen gas is performed using the upper pattern 32a as a mask, and the 1 st pattern (lower pattern 31a) is formed on the lower layer 31 (see fig. 2 d). The dry etching of the lower layer 31 uses an etching gas having a higher mixing ratio of chlorine-based gas than that of the conventional etching gas. The mixing ratio of the mixed gas of the chlorine-based gas and the oxygen gas in the dry etching of the lower layer 31 is preferably a chlorine-based gas in terms of a gas flow ratio in the etching apparatus: 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 lower layer 31, 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 lower layer 31, 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 for applying the bias voltage is preferably 15[ W ] or more, more preferably 20[ W ] or more, and still more preferably 30[ W ] or more, for example. By increasing the bias voltage, the anisotropy of dry etching using a mixed gas of a chlorine-based gas and an oxygen gas can be increased.

Next, a resist film is formed on the upper layer pattern 32a and the phase shift film 2 by spin coating. The resist film is exposed to electron beams to draw a 2 nd pattern (pattern including a light shielding stripe 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 having the 2 nd pattern (light-shielding pattern) (resist pattern 5b) (see fig. 2 (e)).

Next, dry etching using a fluorine-based gas is performed to form a 1 st pattern (phase shift pattern 2a) on the phase shift film 2 using the lower pattern 31a as a mask and to form a 2 nd pattern (upper pattern 32b) on the upper pattern 32a using the resist pattern 5b as a mask (see fig. 2 f). Then, the resist pattern 5b is removed. Here, the lower layer pattern 31a of the light shielding film 3 described later may be directly dry-etched in a state where the resist pattern 5b remains without being removed. In this case, when the lower pattern 31a is dry-etched, the resist pattern 5b disappears,

next, dry etching using a mixed gas of a chlorine-based gas and an oxygen gas is performed using the upper layer pattern 32b as a mask, and the 2 nd pattern (the lower layer pattern 31b) is formed on the lower layer pattern 31a (see fig. 2(g) and (h)). In this case, the dry etching of the lower pattern 31a may be performed under the conventional conditions of the mixing ratio of the chlorine-based gas and the oxygen gas and the bias. Finally, a predetermined process such as cleaning is performed to obtain the phase shift mask 200 (see fig. 2 (h)).

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、SiH₂Cl₂、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 a phase shift film (phase shift pattern 2a) having a transfer pattern and a light shielding film (light shielding pattern 3b) having a light shielding pattern are sequentially stacked on the transparent substrate 1 (see fig. 2)(h) ). The phase shift mask is manufactured from a mask blank 100 and therefore has the same features as the mask blank 100. That is, the phase shift mask 200 is characterized by having a structure in which a phase shift film 2 having a transfer pattern and a light-shielding film 3 having a light-shielding band pattern are sequentially laminated on a transparent substrate 1, the laminated structure of the phase shift film 2 and the light-shielding film 3 has an optical density of 3.5 or more with respect to exposure light of ArF excimer laser light, the light-shielding film 3 has a structure in which a lower layer 31 and an upper layer 32 are laminated from the transparent substrate 1 side, the lower layer 31 is formed of a material containing chromium and having a total content of chromium, oxygen, nitrogen, and carbon of 90 atomic% or more, the upper layer 32 is formed of a material containing metal and silicon and having a total content of metal and silicon of 80 atomic% or more, and the upper layer 32 has an extinction coefficient k with respect to the exposure light_UIs larger than the extinction coefficient k of the lower layer 31 to the exposure light_L。

The phase shift mask 200 is manufactured using the mask blank 100. Therefore, the phase shift mask 200 can improve the CD accuracy of the fine pattern formed on the resist film after the development process even when the phase shift mask is installed in an exposure apparatus using a complicated illumination system such as SMO and the resist film of the transfer target is subjected to exposure transfer.

Method for manufacturing semiconductor device

Next, a method for manufacturing a semiconductor device using the phase shift mask 200 will be described. The method for manufacturing a semiconductor device is characterized in that the transfer pattern (phase shift pattern 2a) of the phase shift mask 200 is transferred to a resist film on a semiconductor substrate by exposure using the phase shift mask 200. 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 reduction transfer exposure is repeatedly performed on the resist film using the phase shift mask 200. Thus, the transfer pattern formed on the phase shift mask 200 is disposed on the resist film without a gap. Note that the exposure apparatus used at this time can irradiate ArF exposure light with an illumination system most suitable for the phase shift mask 200, the phase shift mask 200 having optimized the phase shift pattern 2a using SMO.

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.

The manufacture of the semiconductor device as described above uses an exposure apparatus that can repeatedly perform exposure transfer on a resist film on a semiconductor substrate by irradiating ArF exposure light with an illumination system that is complicated but most suitable for the phase shift mask 200 optimized for the application of SMO to the phase shift pattern 2a, and thus, can expose and transfer a fine pattern to the resist film with high accuracy. Further, the phase shift mask 200 is formed to have the following configuration: the laminated structure of the phase shift pattern 2a and the light shielding pattern 3b constituting the light shielding band has an optical density of 3.5 or more with respect to ArF exposure light, which is significantly improved as compared with the conventional one, and the extinction coefficient k of the upper pattern 32b of the light shielding pattern 3b_UGreater than the extinction coefficient k of the lower pattern 31b_LLight leakage from the light shielding tape is sufficiently suppressed. Thus, even if ArF exposure light is irradiated to the phase shift mask 200 using a complicated illumination system, a decrease in CD accuracy of exposing a fine pattern of a resist film transferred onto a semiconductor substrate due to light leakage can be sufficiently suppressed. Therefore, when the circuit pattern is formed by dry etching the lower 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.