Mask blank, phase shift mask and method for manufacturing semiconductor device
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 前田仁 大久保亮 堀込康隆 于 2019-01-08 设计创作，主要内容包括：本发明涉及一种掩模坯料,在其透光性基板上具备的相移膜至少包含含氮层和含氧层,含氮层由氮化硅类材料形成,含氧层由氧化硅类材料形成,对含氮层进行X射线光电子能谱分析,获得Si2p窄谱的光电子强度的最大峰PSi_f,并对透光性基板进行X射线光电子能谱分析,获得Si2p窄谱的光电子强度的最大峰PSi_s时,用含氮层中的最大峰PSi_f除以透光性基板中的最大峰PSi_s而得到的数值(PSi_f)/(PSi_s)为1.09以下。(The present invention relates to a mask blank, wherein a phase shift film provided on a light-transmitting substrate comprises at least a nitrogen-containing layer and an oxygen-containing layer, the nitrogen-containing layer is formed of a silicon nitride-based material, the oxygen-containing layer is formed of a silicon oxide-based material, and when the nitrogen-containing layer is subjected to X-ray photoelectron spectroscopy to obtain a maximum peak PSi _ f of photoelectron intensity of a narrow spectrum of Si2p and the light-transmitting substrate is subjected to X-ray photoelectron spectroscopy to obtain a maximum peak PSi _ s of photoelectron intensity of a narrow spectrum of Si2p, a value (PSi _ f)/(PSi _ s) obtained by dividing the maximum peak PSi _ f in the nitrogen-containing layer by the maximum peak PSi _ s in the light-transmitting substrate is 1.09 or less.)
1. A mask blank having a phase shift film on a light-transmitting substrate,
the phase shift film comprises at least a nitrogen-containing layer and an oxygen-containing layer,
the oxygen-containing layer is formed of a material containing silicon and oxygen, or a material containing 1 or more elements selected from semimetal elements and nonmetallic elements, oxygen, and silicon,
the nitrogen-containing layer is formed of a material containing silicon and nitrogen, or a material containing 1 or more elements selected from non-metal elements and semi-metal elements, nitrogen, and silicon,
and X-ray photoelectron spectroscopy is performed on the nitrogen-containing layer to obtain a maximum peak PSi _ f of photoelectron intensity of a narrow spectrum of Si2p in the nitrogen-containing layer, and X-ray photoelectron spectroscopy is performed on the light-transmissive substrate to obtain a maximum peak PSi _ s of photoelectron intensity of a narrow spectrum of Si2p in the light-transmissive substrate, wherein a value (PSi _ f)/(PSi _ s) obtained by dividing the maximum peak PSi _ f in the nitrogen-containing layer by the maximum peak PSi _ s in the light-transmissive substrate is 1.09 or less.
2. The mask blank according to claim 1,
the nitrogen content of the nitrogen-containing layer is 50 atomic% or more.
3. The mask blank according to claim 1 or 2, wherein,
the total content of nitrogen and oxygen in the oxygen-containing layer is more than 50 atom%.
4. The mask blank according to any one of claims 1 to 3, wherein,
the oxygen content of the oxygen-containing layer is 15 atomic% or more.
5. The mask blank according to any one of claims 1 to 4, wherein,
the maximum peak of photoelectron intensity in the narrow spectrum of Si2p is a maximum peak in the range of a bond energy of 96[ eV ] or more and 106[ eV ] or less.
6. The mask blank according to any one of claims 1 to 5, wherein,
the X-ray irradiated to the phase shift film in the X-ray photoelectron spectroscopy is an AlK α -ray.
7. The mask blank according to any one of claims 1 to 6, wherein,
with Si in said nitrogen-containing layer3N4Number of bonds present divided by Si3N4Bond, SiaNbA ratio of the total number of bonds, Si-Si bonds, Si-O bonds and Si-ON bonds is 0.88 or more, wherein b/[ a + b ]]＜4/7。
8. The mask blank according to any one of claims 1 to 7, wherein,
the phase shift film has the following functions:
a function of transmitting the exposure light of the ArF excimer laser at a transmittance of 10% or more, and
and a function of generating a phase difference of 150 degrees or more and 200 degrees or less between the exposure light transmitted through the phase shift film and the exposure light passed only through the air having the same distance as the thickness of the phase shift film.
9. The mask blank according to any one of claims 1 to 8, comprising a light-shielding film on the phase shift film.
10. A phase shift mask having a phase shift film on which a transfer pattern is formed on a light-transmissive substrate,
the phase shift film comprises at least a nitrogen-containing layer and an oxygen-containing layer,
the oxygen-containing layer is formed of a material containing silicon and oxygen, or a material containing 1 or more elements selected from semimetal elements and nonmetallic elements, oxygen, and silicon,
the nitrogen-containing layer is formed of a material containing silicon and nitrogen, or a material containing 1 or more elements selected from non-metal elements and semi-metal elements, nitrogen, and silicon,
and X-ray photoelectron spectroscopy is performed on the nitrogen-containing layer to obtain a maximum peak PSi _ f of photoelectron intensity of a narrow spectrum of Si2p in the nitrogen-containing layer, and X-ray photoelectron spectroscopy is performed on the light-transmissive substrate to obtain a maximum peak PSi _ s of photoelectron intensity of a narrow spectrum of Si2p in the light-transmissive substrate, wherein a value (PSi _ f)/(PSi _ s) obtained by dividing the maximum peak PSi _ f in the nitrogen-containing layer by the maximum peak PSi _ s in the light-transmissive substrate is 1.09 or less.
11. The phase shift mask according to claim 10,
the nitrogen content of the nitrogen-containing layer is 50 atomic% or more.
12. The phase shift mask according to claim 10 or 11,
the total content of nitrogen and oxygen in the oxygen-containing layer is more than 50 atom%.
13. The phase shift mask according to any one of claims 10 to 12,
the oxygen content of the oxygen-containing layer is 15 atomic% or more.
14. The phase shift mask according to any one of claims 10 to 13,
the maximum peak of photoelectron intensity in the narrow spectrum of Si2p is a maximum peak in the range of a bond energy of 96[ eV ] or more and 106[ eV ] or less.
15. The phase shift mask according to any one of claims 10 to 14,
the X-ray irradiated to the phase shift film in the X-ray photoelectron spectroscopy is an AlK α -ray.
16. The phase shift mask according to any one of claims 10 to 15,
with Si in said nitrogen-containing layer3N4Number of bonds present divided by Si3N4Bond, SiaNbA ratio of the total number of bonds, Si-Si bonds, Si-O bonds and Si-ON bonds is 0.88 or more, wherein b/[ a + b ]]＜4/7。
17. The phase shift mask according to any one of claims 10 to 16,
the phase shift film has the following functions:
a function of transmitting the exposure light of the ArF excimer laser at a transmittance of 10% or more, and
and a function of generating a phase difference of 150 degrees or more and 200 degrees or less between the exposure light transmitted through the phase shift film and the exposure light passed only through the air having the same distance as the thickness of the phase shift film.
18. The phase shift mask according to any one of claims 10 to 17, comprising a light-shielding film having a light-shielding pattern formed thereon.
19. 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 10 to 18.
Technical Field
The present invention relates to a mask blank and a phase shift mask manufactured using the mask blank. The present invention also relates to a method for manufacturing a semiconductor device using the phase shift mask.
Background
In a manufacturing process of a semiconductor device, a fine pattern is formed by photolithography. In addition, in forming the fine pattern, a plurality of transfer masks are generally used. In order to miniaturize the pattern of a semiconductor device, it is necessary to shorten the wavelength of an exposure light source used for photolithography in addition to miniaturizing the mask pattern formed on a transfer mask. In recent years, ArF excimer laser light (wavelength 193nm) is increasingly used in an exposure light source in the manufacture of semiconductor devices.
One of the transfer masks includes a halftone type phase shift mask. The halftone phase shift mask includes a light transmission portion through which exposure light is transmitted, and a phase shift portion (of a halftone phase shift film) through which the exposure light is attenuated, and the phase of the exposure light transmitted through the phase shift portion is substantially inverted (phase difference of approximately 180 degrees) with respect to the phase of the exposure light transmitted through the light transmission portion. The contrast of the optical image at the boundary between the light-transmitting portion and the phase shift portion is improved by the phase difference, and thus the halftone phase shift mask becomes a transfer mask with high resolution.
In the halftone-type phase shift mask, the higher the transmittance of the halftone phase shift film to the exposure light, the higher the contrast of the transferred image tends to be. Therefore, a so-called high-transmittance halftone type phase shift mask is used particularly mainly when high resolution is required. In a phase shift film of a halftone type phase shift mask, a molybdenum silicide (MoSi) -based material is widely used. However, in recent years, it has been found that the MoSi-based film has low resistance to exposure light of ArF excimer laser light (so-called ArF light resistance).
As a phase shift film of a halftone type phase shift mask, a SiN-based material containing silicon and nitrogen is also known, and is disclosed in patent document 1, for example. In addition, as a method for obtaining desired optical characteristics, patent document 2 discloses a method using a periodic multilayer film formed of an Si oxide layer and an Si nitride layerA halftone type phase shift mask of a phase shift film. Patent document 2 describes that F is a group F2The light of 157nm wavelength of the excimer laser obtains a given phase difference with a transmittance of 5%. Since SiN-based materials have high ArF light resistance, high-transmittance halftone phase shift masks using SiN-based films as phase shift films have attracted attention.
Disclosure of Invention
Problems to be solved by the invention
In the case of using a single-layer phase shift film made of a silicon nitride material, there is a limit in transmittance of the ArF excimer laser light with respect to exposure light (hereinafter referred to as ArF exposure light), and it is difficult to make the transmittance higher than 18% in terms of optical characteristics.
When oxygen is introduced into silicon nitride, the transmittance can be improved. However, if a single-layer phase shift film made of a silicon nitride oxide material is used, there is a problem that etching selectivity with respect to a light-transmitting substrate formed of a material containing silicon oxide as a main component becomes small when image formation of the phase shift film is performed by dry etching.
As a method for solving the above problem, for example, a method of forming a phase shift film to have a 2-layer structure including a silicon nitride layer and a silicon oxide layer which are sequentially arranged from the light transmissive substrate side is considered. Patent document 1 discloses a halftone phase shift mask including a phase shift film having a 2-layer structure including a silicon nitride layer and a silicon oxide layer disposed in this order from a light-transmissive substrate side.
By providing the phase shift film with a 2-layer structure composed of a silicon nitride layer and a silicon oxide layer, the degree of freedom in refractive index, extinction coefficient, and film thickness with respect to ArF exposure light is increased, and the phase shift film having the 2-layer structure can have a desired transmittance and phase difference with respect to ArF exposure light. However, as a result of detailed studies, it has been found that the following problems are present in a halftone phase shift mask including a phase shift film having a 2-layer structure composed of a silicon nitride layer and a silicon oxide layer.
Both the silicon nitride layer and the silicon oxide layer have ArF light resistance much higher than that of the MoSi-based film. However, the ArF light resistance of the silicon nitride layer is lower than that of the silicon oxide layer. That is, when a phase shift mask is manufactured from a mask blank having the phase shift film, the phase shift mask is set in an exposure apparatus, and exposure transfer by ArF exposure light is repeated, the line width of the pattern of the phase shift film is more likely to be wider in the portion of the silicon nitride layer than in the portion of the silicon oxide layer. Therefore, although the portion of the silicon oxide layer is not easily widened by the repeated irradiation of the ArF exposure light, there is a problem that the pattern line width of the entire phase shift film is easily widened by the repeated irradiation of the ArF exposure light.
The silicon nitride layer and the silicon oxide layer each have a resistance (chemical resistance) to a chemical liquid used for cleaning or the like, which is much higher than that of the MoSi-based film. However, silicon nitride layers are less chemically resistant than silicon oxide layers. That is, in the process of manufacturing a phase shift mask from a mask blank having the phase shift film, when the phase shift mask is repeatedly cleaned with a chemical liquid after the manufacturing, the line width of the pattern of the phase shift film in the portion of the silicon nitride layer is more likely to be reduced than the line width of the portion of the silicon oxide layer. Therefore, even though the silicon oxide layer has high chemical resistance, there is a problem that the decrease in the pattern line width of the entire phase shift film becomes relatively large when cleaning with a chemical liquid is repeated.
On the other hand, in the phase shift film having a 2-layer structure described above, when the material for forming the high-transmittance layer is formed of silicon oxynitride instead of silicon oxide, optical characteristics similar to those in the case of forming the high-transmittance layer from silicon oxide can be obtained. However, the phase shift film having such a structure also has problems of ArF light resistance and chemical resistance.
The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a mask blank for a halftone-type phase shift mask, which has a phase shift film including at least a nitrogen-containing layer such as a silicon nitride layer and an oxygen-containing layer such as a silicon oxide layer on a light-transmissive substrate, and which has improved ArF light resistance and chemical resistance of the entire phase shift film.
Another object of the present invention is to provide a phase shift mask produced using the mask blank.
Further, it is an object of the present invention to provide a method of manufacturing such a phase shift mask.
Further, the present invention is directed to a method for manufacturing a semiconductor device using such a phase shift mask.
Means for solving the problems
In order to solve the above problems, the present invention has the following aspects.
(scheme 1)
A mask blank having a phase shift film on a light-transmitting substrate,
the phase shift film at least comprises a nitrogen-containing layer and an oxygen-containing layer,
the oxygen-containing layer is formed of a material containing silicon and oxygen, or a material containing 1 or more elements selected from the group consisting of semimetallic elements and nonmetallic elements, oxygen and silicon,
the nitrogen-containing layer is formed of a material containing silicon and nitrogen, or a material containing 1 or more elements selected from the group consisting of non-metal elements and semi-metal elements, nitrogen and silicon,
when the maximum peak PSi _ s of the photoelectron intensity of the narrow spectrum of Si2p in the light-transmitting substrate is obtained by performing X-ray photoelectron spectroscopy on the nitrogen-containing layer to obtain the maximum peak PSi _ f of the photoelectron intensity of the narrow spectrum of Si2p in the nitrogen-containing layer and performing X-ray photoelectron spectroscopy on the light-transmitting substrate, a value (PSi _ f)/(PSi _ s) obtained by dividing the maximum peak PSi _ s in the light-transmitting substrate by the maximum peak PSi _ f in the nitrogen-containing layer is 1.09 or less.
(scheme 2)
The mask blank according to claim 1, wherein,
the nitrogen content of the nitrogen-containing layer is 50 atomic% or more.
(scheme 3)
The mask blank according to claim 1 or 2, wherein,
the total content of nitrogen and oxygen in the oxygen-containing layer is 50 atomic% or more.
(scheme 4)
The mask blank according to any one of claims 1 to 3, wherein,
the oxygen content of the oxygen-containing layer is 15 atomic% or more.
(scheme 5)
The mask blank according to any one of claims 1 to 4, wherein,
the maximum peak of the photoelectron intensity of the narrow spectrum of Si2p is a maximum peak in the range of a bond energy of 96 eV or more and 106 eV or less.
(scheme 6)
The mask blank according to any one of claims 1 to 5, wherein,
in the X-ray photoelectron spectroscopy, the X-ray irradiated to the phase shift film is an AlK α -ray.
(scheme 7)
The mask blank according to any one of claims 1 to 6, wherein,
by Si in the above-mentioned nitrogen-containing layer3N4Number of bonds present divided by Si3N4Bond, SiaNbBond (wherein, b/[ a + b ]]< 4/7), the total number of Si-Si bonds, Si-O bonds and Si-ON bonds is 0.88 or more.
(scheme 8)
The mask blank according to any one of claims 1 to 7, wherein,
the phase shift film has a function of transmitting exposure light of an ArF excimer laser beam at a transmittance of 10% or more, and a function of generating a phase difference of 150 degrees or more and 200 degrees or less between the exposure light transmitted through the phase shift film and the exposure light transmitted only through the air at the same distance as the thickness of the phase shift film.
(scheme 9)
The mask blank according to any one of claims 1 to 8, wherein a light-shielding film is provided on the phase shift film.
(scheme 10)
A phase shift mask having a phase shift film on which a transfer pattern is formed on a light-transmissive substrate,
the phase shift film at least comprises a nitrogen-containing layer and an oxygen-containing layer,
the oxygen-containing layer is formed of a material containing silicon and oxygen, or a material containing 1 or more elements selected from the group consisting of semimetallic elements and nonmetallic elements, oxygen and silicon,
the nitrogen-containing layer is formed of a material containing silicon and nitrogen, or a material containing 1 or more elements selected from the group consisting of non-metal elements and semi-metal elements, nitrogen and silicon,
when the maximum peak PSi _ s of the photoelectron intensity of the narrow spectrum of Si2p in the light-transmitting substrate is obtained by performing X-ray photoelectron spectroscopy on the nitrogen-containing layer to obtain the maximum peak PSi _ f of the photoelectron intensity of the narrow spectrum of Si2p in the nitrogen-containing layer and performing X-ray photoelectron spectroscopy on the light-transmitting substrate, a value (PSi _ f)/(PSi _ s) obtained by dividing the maximum peak PSi _ s in the light-transmitting substrate by the maximum peak PSi _ f in the nitrogen-containing layer is 1.09 or less.
(scheme 11)
The phase shift mask according to scheme 10, wherein,
the nitrogen content of the nitrogen-containing layer is 50 atomic% or more.
(scheme 12)
The phase shift mask according to scheme 10 or 11, wherein,
the total content of nitrogen and oxygen in the oxygen-containing layer is 50 atomic% or more.
(scheme 13)
The phase shift mask according to any of schemes 10 to 12,
the oxygen content of the oxygen-containing layer is 15 atomic% or more.
(scheme 14)
The phase shift mask according to any of claims 10 to 13, wherein,
the maximum peak of the photoelectron intensity of the narrow spectrum of Si2p is a maximum peak in the range of a bond energy of 96 eV or more and 106 eV or less.
(scheme 15)
The phase shift mask according to any of claims 10 to 14, wherein,
the X-ray irradiated to the phase shift film in the X-ray photoelectron spectroscopy is an AlK alpha ray
(scheme 16)
The phase shift mask according to any of claims 10 to 15, wherein,
by Si in the above-mentioned nitrogen-containing layer3N4Number of bonds present divided by Si3N4Bond, SiaNbBond (wherein, b/[ a + b ]]< 4/7), the total number of Si-Si bonds, Si-O bonds and Si-ON bonds is 0.88 or more.
(scheme 17)
The phase shift mask according to any of claims 10 to 16, wherein,
the phase shift film has a function of transmitting exposure light of an ArF excimer laser beam at a transmittance of 10% or more, and a function of generating a phase difference of 150 degrees or more and 200 degrees or less between the exposure light transmitted through the phase shift film and the exposure light transmitted only through the air at the same distance as the thickness of the phase shift film.
(scheme 18)
The phase shift mask according to any of claims 10 to 17,
the phase shift film is provided with a light shielding film having a light shielding pattern formed thereon.
(scheme 19)
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 according to any one of claims 10 to 18.
ADVANTAGEOUS EFFECTS OF INVENTION
The mask blank of the present invention comprises a phase shift film on a light-transmitting substrate, wherein the phase shift film comprises at least a nitrogen-containing layer and an oxygen-containing layer, the oxygen-containing layer is formed of a material containing silicon and oxygen, or a material containing 1 or more elements selected from the group consisting of semimetallic elements and nonmetallic elements, oxygen, and silicon, the nitrogen-containing layer is formed of a material containing silicon and nitrogen, or a material containing 1 or more elements selected from non-metal elements and semimetal elements, nitrogen and silicon, carrying out X-ray photoelectron spectroscopy analysis on the nitrogen-containing layer to obtain a maximum peak PSi _ f of photoelectron intensity of Si2p narrow spectrum in the nitrogen-containing layer, and X-ray photoelectron spectroscopy is performed on the light-transmitting substrate to obtain a maximum peak PSi _ s of photoelectron intensity of narrow spectrum of Si2p in the light-transmitting substrate, a value (PSi _ f)/(PSi _ s) obtained by dividing the maximum peak PSi _ s in the light-transmitting substrate by the maximum peak PSi _ f in the nitrogen-containing layer is 1.09 or less. By forming a mask blank having such a structure, the ArF light resistance and chemical resistance of the entire phase shift film can be improved.
The phase shift mask of the present invention is characterized in that the phase shift film having the transfer pattern has the same configuration as the phase shift film of the mask blank of the present invention. By forming such a phase shift mask, the ArF light resistance and chemical resistance of the entire phase shift film can be improved. Therefore, the phase shift mask of the present invention has high transfer accuracy when performing exposure transfer to a transfer target such as a resist film on a semiconductor substrate.
The method for manufacturing a semiconductor device of the present invention includes a step of exposing and transferring a transfer pattern to a resist film on a semiconductor substrate using the phase shift mask of the present invention. Therefore, the method for manufacturing a semiconductor device of the present invention can perform exposure transfer of the transfer pattern to the resist film with high transfer accuracy.
Drawings
Fig. 1 is a sectional view showing a structure of a mask blank according to an embodiment of the present invention.
Fig. 2 is a sectional view showing a manufacturing process of a phase shift mask in the embodiment of the present invention.
Fig. 3 is a graph showing the results of X-ray photoelectron spectroscopy (narrow spectrum of Si2p) performed on the phase shift film and the light-transmitting substrate of the phase shift film of the mask blank of example 1 of the present invention.
Fig. 4 is a graph showing the results of X-ray photoelectron spectroscopy (narrow spectrum of Si2p) performed on the phase shift film and the light-transmitting substrate of the mask blank of comparative example 1 of 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 1 st resist pattern
6b No. 2 resist pattern
100 mask blank
200 phase shift mask
Detailed Description
First, the process of completing the present invention will be described. The present inventors have made studies with respect to a case where a phase shift film of a mask blank has a laminated structure including a silicon nitride-based material layer (nitrogen-containing layer) and a silicon oxide-based material layer (oxygen-containing layer), from the viewpoint of ArF light resistance and chemical resistance of the phase shift film.
The reason why the line width of the pattern of the silicon-based material layer becomes wider when irradiated with ArF exposure light is considered to be: the silicon atom in a state of being bonded to other elements (including other silicon atoms) is excited to cut the bond, and a reaction of being bonded to oxygen is performed, thereby causing volume expansion. Therefore, in the case where a silicon oxide-based material layer of silicon already bonded with oxygen exists in a large amount at a stage before being irradiated with ArF exposure light, the pattern line width due to volume expansion is not easily widened even when irradiated with ArF exposure light. In addition, silicon bonded to oxygen is less soluble in chemical liquids than silicon bonded to elements other than oxygen.
By containing oxygen in the silicon nitride material layer, the ArF light resistance and chemical resistance can be improved. However, if oxygen is contained in the silicon nitride material layer, it is difficult to avoid a decrease in the refractive index n and the extinction coefficient k, and the degree of freedom in designing the phase shift film is greatly reduced, so that it is difficult to apply this method.
As a result of intensive studies, the present inventors have found that when a silicon nitride material in which silicon is less likely to be excited when ArF exposure light is irradiated is used for a silicon nitride material layer of a phase shift film, the ArF light resistance of the entire phase shift film can be improved.
The present inventors have conceived to apply X-ray photoelectron spectroscopy (XPS) as an index of whether or not silicon in a silicon nitride material layer is in a state of being easily excited when the layer is irradiated with ArF exposure light. First, a narrow spectrum of Si2p was obtained by X-ray photoelectron spectroscopy of a silicon nitride material layer, and the difference in the maximum peak was used as an index. The maximum peak of the photoelectron intensity of the Si2p narrow spectrum in the silicon nitride-based material layer corresponds to the number of photoelectrons emitted from the bond between nitrogen and silicon per unit time. Photoelectrons are electrons that are excited by irradiation with X-rays and then fly out of an atomic orbit. A material which is likely to be excited in a large number of photoelectrons emitted when X-rays are irradiated is a material having a small work function. Such a silicon nitride-based material having a small work function can be said to be a material which is easily excited even when irradiated with ArF exposure light.
However, the number of photoelectrons detected by X-ray photoelectron spectroscopy varies depending on the measurement conditions (the type of X-ray used, the irradiation intensity, and the like) even in the same silicon nitride material layer, and therefore, cannot be directly used as an index. As a result of examining this problem, it was found that a value obtained by dividing the maximum peak of the photoelectron intensity of the Si2p narrow spectrum in the silicon nitride-based material layer by the maximum peak of the photoelectron intensity of the Si2p narrow spectrum in the transparent substrate was used as an index.
The light-transmitting substrate is made of SiO2A relatively stable material as a main component. The translucent substrate used for the mask blank is required to have very small material variation such as small variation in optical characteristics. Therefore, the work function unevenness of each material between the plurality of light-transmissive substrates is also very small. Under the same measurement conditions, the difference between the maximum peaks of the photoelectron intensities of the narrow Si2p spectra between the different light transmissive substrates is small, and therefore, the influence of the difference in the measurement conditions is reflected significantly on the maximum peak of the photoelectron intensities. The maximum peak of the photoelectron intensity of the narrow Si2p spectrum in the light-transmitting substrate is the number of photoelectrons emitted from the bond between oxygen and silicon per unit time, but it is also possible to use the peak as a peakThe reference value is suitable for correcting the difference between the maximum peaks of the photoelectron intensity of the narrow spectrum of Si2p in the silicon nitride material layer due to the difference in the measurement conditions.
The present inventors have further conducted intensive studies and, as a result, have reached the following conclusions: when a mask blank having a phase shift film comprising at least a silicon nitride material layer (nitrogen-containing layer) and a silicon oxide material layer (oxygen-containing layer) on a light-transmitting substrate is subjected to X-ray photoelectron spectroscopy on the silicon nitride material layer and the light-transmitting substrate, if the value (PSi _ f)/(PSi _ s) obtained by dividing the maximum peak PSi _ f of photoelectron intensity of Si2p narrow spectrum in the silicon nitride material layer by the maximum peak PSi _ s of photoelectron intensity of Si2p narrow spectrum in the light-transmitting substrate is 1.09 or less, the ArF light resistance can be improved.
On the other hand, the following conclusions were obtained: when the silicon nitride material layer having the above numerical value (PSi _ f)/(PSi _ s) of 1.09 or less is irradiated with ArF exposure light, silicon in the layer is not easily excited; in such a silicon nitride-based material layer, the ratio of the existence of the strong bond between nitrogen and silicon is high; when the chemical liquid is in contact with the silicon nitride-based material layer, the bond between nitrogen and silicon is not easily broken, and the chemical liquid is not easily dissolved therein.
As a result of the above intensive studies, the mask blank of the present invention was obtained. That is, the mask blank of the present invention is a mask blank comprising a phase shift film on a light-transmissive substrate, the phase shift film comprising at least a nitrogen-containing layer (silicon nitride-based material layer) and an oxygen-containing layer (silicon oxide-based material layer), the oxygen-containing layer being formed of a material containing silicon and oxygen or a material containing 1 or more elements selected from semimetal elements and nonmetal elements, oxygen and silicon, the nitrogen-containing layer being formed of a material containing silicon and nitrogen or a material containing 1 or more elements selected from nonmetal elements and semimetal elements, nitrogen and silicon, the nitrogen-containing layer being subjected to X-ray photoelectron spectroscopy to obtain a maximum peak PSi _ f of photoelectron intensity of Si2p narrow spectrum in the nitrogen-containing layer and the light-transmissive substrate being subjected to X-ray photoelectron spectroscopy to obtain a maximum peak PSi _ s of photoelectron intensity of Si2p narrow spectrum in the light-transmissive substrate, in this case, the value (PSi _ f)/(PSi _ s) obtained by dividing the maximum peak PSi _ f in the nitrogen-containing layer by the maximum peak PSi _ s in the transparent substrate is 1.09 or less.
Next, embodiments of the present invention will be explained. The mask blank of the present invention can be applied to a mask blank for fabricating a phase shift mask. Hereinafter, a mask blank for manufacturing a halftone phase shift mask will be described.
Fig. 1 is a sectional view showing a structure of a mask blank 100 according to an embodiment of the present invention. The mask blank 100 shown in fig. 1 has a structure in which a phase shift film 2, a light-shielding film 3, and a hard mask film 4 are sequentially stacked on a light-transmissive substrate 1.
The light-transmitting substrate 1 may be formed of synthetic quartz glass, or may be formed of quartz glass, aluminosilicate glass, soda-lime glass, or low thermal expansion glass (SiO)2-TiO2Glass, etc.). Among these, synthetic quartz glass has high transmittance for ArF excimer laser light (wavelength 193nm), and is particularly preferably used as a material for forming a light-transmitting substrate of a mask blank.
The phase shift film 2 is required to have a transmittance that can make the phase shift effect function effectively. The transmittance of the phase shift film 2 to ArF exposure light is required to be at least 1% or more. The transmittance of the phase shift film 2 to ArF exposure light is preferably 10% or more, more preferably 15% or more, and still more preferably 20% or more.
The transmittance of the phase shift film 2 with respect to ArF exposure light is preferably adjusted to 40% or less, more preferably 30% or less.
In recent years, NTD (Negative Tone Development) has been used as an exposure/Development process for a resist film on a semiconductor substrate (wafer). In the NTD, a bright field mask (a transfer mask having a high pattern aperture ratio) is often used. In the bright field phase shift mask, the transmittance of the phase shift film with respect to the exposure light is set to 10% or more, so that the balance between the zero-order light and the primary light of the light transmitted through the light transmission portion becomes favorable. When the balance is good, the exposure light transmitted through the phase shift film interferes with the zero-order light, the effect of attenuating the light intensity becomes large, and the pattern definition on the resist film improves. Therefore, the transmittance of the phase shift film 2 to ArF exposure light is preferably 10% or more. When the transmittance of ArF exposure light is 15% or more, the pattern edge enhancement effect of the transferred image (projected optical image) by the phase shift effect is further increased. On the other hand, if the transmittance of the phase shift film 2 for ArF exposure light exceeds 40%, the influence of the side lobe becomes stronger, which is not preferable.
In order to obtain an appropriate phase shift effect, the phase shift film 2 is required to have a function of generating a predetermined phase difference between the transmitted ArF exposure light and the light passing only in the air at the same distance as the thickness of the phase shift film 2. The phase difference is preferably adjusted to a range of 150 degrees or more and 200 degrees or less. The lower limit value of the retardation in the phase shift film 2 is more preferably 160 degrees or more, and still more preferably 170 degrees or more. On the other hand, the upper limit value of the phase difference in the phase shift film 2 is more preferably 190 degrees or less.
The thickness of the phase shift film 2 is preferably 90nm or less, more preferably 80nm or less. On the other hand, the thickness of the phase shift film 2 is preferably 40nm or more. When the thickness of the phase shift film 2 is less than 40nm, a given transmittance and a given phase difference required for the phase shift film may not be obtained.
The phase shift film 2 is a laminated film having at least 2 layers including a nitrogen-containing layer (silicon nitride-based material layer) and an oxygen-containing layer (silicon oxide-based material layer). The phase shift film 2 may have at least one nitrogen-containing layer and one oxygen-containing layer, and may further have 1 or more nitrogen-containing layers and oxygen-containing layers. For example, the phase shift film 2 may have a structure having a one-layer structure including 2 or more groups of nitrogen-containing layers and oxygen-containing layers (a 4-layer or more layer structure), or may have a structure in which an oxygen-containing layer is provided between 2 nitrogen-containing layers. The phase shift film 2 may have a material layer other than the nitrogen-containing layer and the oxygen-containing layer as long as the effect of the present invention is obtained.
The nitrogen-containing layer is preferably formed of a material containing silicon and nitrogen, or a material containing 1 or more elements selected from non-metal elements and semi-metal elements, nitrogen, and silicon. The nitrogen-containing layer may contain any semimetal element. When the semimetal element contains 1 or more elements selected from boron, germanium, antimony, and tellurium, the conductivity of silicon used as a sputtering target can be expected to be improved, and thus the semimetal element is preferable.
The nitrogen-containing layer may contain any non-metallic element. The nonmetal elements in this case include nonmetal elements (nitrogen, carbon, oxygen, phosphorus, sulfur, selenium) in a narrow sense, halogen, and rare gas. Among the nonmetal elements, 1 or more elements selected from carbon, fluorine and hydrogen are preferably contained. The nitrogen-containing layer preferably contains oxygen in an amount of 10 atomic% or less, more preferably 5 atomic% or less, and further preferably does not positively contain oxygen (lower limit of detection in composition analysis such as X-ray photoelectron spectroscopy). When the nitrogen-containing layer has a large oxygen content, the difference in optical characteristics between the nitrogen-containing layer and the oxygen-containing layer is small, and the degree of freedom in designing the phase shift film is small.
The nitrogen-containing layer may also contain a noble gas. The rare gas is an element which can improve the film formation rate and productivity by being present in the film formation chamber when the nitrogen-containing layer is formed by reactive sputtering. The rare gas is converted into plasma and collides with the target, whereby the target constituent element is ejected from the target, and the reactive gas is captured in the process, thereby forming a nitrogen-containing layer on the transparent substrate 1. During the time when the target constituent element flies out from the target and adheres to the transparent substrate 1, a small amount of the rare gas in the film forming chamber is trapped. As a rare gas necessary for the reactive sputtering, preferred elements include argon, krypton, and xenon. In addition, helium or neon having a small atomic weight can be positively trapped in the thin film in order to relax the stress of the nitrogen-containing layer.
The nitrogen content of the nitrogen-containing layer is preferably 50 atomic% or more. The refractive index n of the silicon-based film with respect to ArF exposure light is very small, and the extinction coefficient k with respect to ArF exposure light is large. Hereinafter, the refractive index n is simply referred to as the refractive index n with respect to ArF exposure light. The term "extinction coefficient k" refers to the extinction coefficient k for ArF exposure light. As the content of nitrogen in the silicon-based film increases, the refractive index n tends to increase and the extinction coefficient tends to decrease. In view of ensuring a given transmittance required for the phase shift film 2 while ensuring a retardation with a thinner thickness, the nitrogen content of the nitrogen-containing layer is preferably 50 atomic% or more, more preferably 51 atomic% or more, and still more preferably 52 atomic% or more. In addition, of nitrogen-containing layersThe content is preferably 57 at% or less, more preferably 56 at% or less. If the nitrogen content in the nitrogen-containing layer is made to be larger than that of Si3N4If the mixing ratio of (A) is too high, it is difficult to form the nitrogen-containing layer into an amorphous or microcrystalline structure. In addition, the surface roughness of the nitrogen-containing layer is greatly deteriorated.
The silicon content of the nitrogen-containing layer is preferably 35 atomic% or more, more preferably 40 atomic% or more, and further preferably 45 atomic% or more.
The nitrogen-containing layer is preferably formed of a material containing silicon and nitrogen. In this case, the material containing silicon and nitrogen is considered to include a material containing a rare gas.
When the maximum peak PSi _ f of the photoelectron intensity of the Si2p narrow spectrum in the nitrogen-containing layer is obtained by X-ray photoelectron spectroscopy analysis of the nitrogen-containing layer and the maximum peak PSi _ s of the photoelectron intensity of the Si2p narrow spectrum in the light-transmitting substrate 1 is obtained by X-ray photoelectron spectroscopy analysis of the light-transmitting substrate 1, the value (PSi _ f)/(PSi _ s) obtained by dividing the maximum peak PSi _ f in the nitrogen-containing layer by the maximum peak PSi _ s in the light-transmitting substrate 1 is preferably 1.09 or less. The nitrogen-containing layer having a value (PSi _ f)/(PSi _ s) of 1.09 or less is less likely to be excited by irradiation with ArF exposure light, as described above. By forming such a nitrogen-containing layer, the ArF light resistance can be improved. As described above, the nitrogen-containing layer has a high ratio of the presence of a strong bond between nitrogen and silicon. Further, by providing such a nitrogen-containing layer, chemical resistance can be improved. The value (PSi _ f)/(PSi _ s) is preferably 1.085 or less, more preferably 1.08 or less.
On the other hand, SF is used when forming an image of the phase shift film 26In the case of dry etching with an isofluorine-based gas, the etching rate of the nitrogen-containing layer is higher than that of the oxygen-containing layer. Therefore, when the phase shift film 2 is patterned by dry etching, a level difference tends to be easily generated in the sidewall of the pattern.
In the case of forming a pattern on the nitrogen-containing layer by the above-described dry etching using a fluorine-based gas, the fluorine gas in an excited state cuts the bond between nitrogen and silicon, and generates and volatilizes a fluoride of silicon having a relatively low boiling point, thereby forming a pattern on the nitrogen-containing layer. A nitrogen-containing layer having a numerical value (PSi _ f)/(PSi _ s) of 1.09 or less is unlikely to break the bond between nitrogen and silicon, and therefore, it can be said that the etching rate for dry etching with a fluorine-based gas is slow. This reduces the difference in the etching rate between the nitrogen-containing layer and the oxygen-containing layer of the phase shift film 2, and thus can reduce the difference in the height of the sidewall of the pattern formed on the phase shift film 2 by dry etching.
On the other hand, as a mask defect correction technique of a halftone type phase shift mask, the following defect correction techniques are sometimes used: supplying xenon difluoride (XeF) to the black defect part of the phase shift film2) The black defect portion is changed to a volatile fluoride by irradiating the portion with an electron beam, and the portion is removed by etching. Hereinafter, the defect correction by irradiation with such charged particles such as electron beams is simply referred to as EB defect correction. When EB defect correction is performed on the phase shift film 2 after the transfer pattern is formed, the correction rate of the nitrogen-containing layer tends to be faster than the correction rate of the oxygen-containing layer. In addition, in the case of EB defect correction, since the pattern of the phase shift film 2 with the sidewalls exposed is etched, the etching performed in the direction of the sidewalls of the pattern, that is, the side etching, is particularly likely to enter the nitrogen-containing layer. Therefore, the pattern shape after EB defect correction tends to be a level difference shape in which a level difference is formed between the nitrogen-containing layer and the oxygen-containing layer.
XeF for use in EB defect correction2Gases are known as non-excited etching gases when isotropic etching is performed on a silicon-based material. The etching is through the unexcited XeF state2The gas adsorbs and separates Xe and F on the surface of the silicon-based material, and the process of generating and volatilizing a high fluoride of silicon is performed. In EB defect correction of a thin film pattern of a silicon-based material, XeF is supplied to a black defect portion of the thin film pattern2A fluorine-based gas in a non-excited state such as a gas is adsorbed on the surface of the black defect portion, and then the black defect portion is irradiated with an electron beam. Thus, silicon atoms in the black defect portion are excited to promote bonding with fluorine, and the high-fluoride formed as silicon is volatilized more rapidly than in the case where electron beams are not irradiated. The nitrogen-containing layer which emits a small number of photoelectrons upon X-ray irradiation and is not easily excited can be said to be a layer which is hardly excited when it receives an electron beamIs less likely to be excited by irradiation.
The nitrogen-containing layer having the above numerical value (PSi _ f)/(PSi _ s) of 1.09 or less is not easily excited by irradiation of electron beams, and can slow down the correction rate when EB defect correction is performed. This reduces the difference in correction rate between the EB defect correction of the nitrogen-containing layer and the oxygen-containing layer of the phase shift film 2, and can reduce the difference in height of the sidewall of the pattern at the portion of the phase shift film 2 where the EB defect correction is performed.
In the above-described X-ray photoelectron spectroscopy, as the X-ray to be irradiated to the nitrogen-containing layer of the transparent substrate 1 or the phase shift film 2, any of an AlK α ray and an MgK α ray can be used, but an AlK α ray is preferably used. In the present specification, a case where X-ray photoelectron spectroscopy using an X-ray of an AlK α ray is performed will be described.
The method of obtaining a narrow spectrum of Si2p by X-ray photoelectron spectroscopy of the light-transmissive substrate 1 and the nitrogen-containing layer is generally performed in the following order. That is, first, a broad scan is performed to obtain photoelectron intensity (the number of photoelectrons emitted from the measurement object after X-ray irradiation per unit time) with a broad band width of the bond energy, and a broad scan spectrum is obtained, and all peaks from the light-transmitting substrate 1 and the constituent elements of the nitrogen-containing layer are specified. Then, each narrow spectrum is obtained by performing with a bandwidth around the peak (Si2p) of a narrow scan focusing on the bandwidth of the bond energy which is high in resolution but can be obtained as compared with the wide scan. On the other hand, in the present invention, the constituent elements in the light-transmissive substrate 1 and the nitrogen-containing layer, which are the objects to be measured by the X-ray photoelectron spectroscopy, are known in advance. In addition, the narrow spectrum required in the present invention is limited to the narrow spectrum of Si2 p. Therefore, in the case of the present invention, the step of obtaining a broad scan spectrum can be omitted, and a narrow spectrum of Si2p can be obtained.
The maximum peaks (PSi _ s, PSi _ f) of the photoelectron intensity in the narrow Si2p spectrum obtained by X-ray photoelectron spectroscopy of the light-transmitting substrate 1 and the nitrogen-containing layer are preferably maximum peaks having a bond energy in the range of 96[ eV ] or more and 106[ eV ] or less. This is because a peak outside the range of the bond energy may not be a photoelectron emitted from an Si-N bond or an Si-O bond.
For nitrogen-containing layers, Si is preferred3N4Number of bonds present divided by Si3N4Bond, SiaNbBond (wherein, b/[ a + b ]]< 4/7), the total number of Si-Si bonds, Si-O bonds and Si-ON bonds is 0.88 or more. The nitrogen-containing layer having a high existence ratio of stable bonds has high ArF light resistance and chemical resistance. Among the above-mentioned bonds, the Si — O bond is the most stable bond, but it is difficult to contain a large amount of oxygen in the nitrogen-containing layer due to the above-mentioned limitations. In bonds with silicon other than oxygen, Si3N4The bond is the most stable bond, Si as described above3N4The nitrogen-containing layer having a high ratio of the presence of the bond has high ArF light resistance and chemical resistance.
The total thickness of all the nitrogen-containing layers provided on the phase shift film 2 is preferably 30nm or more. If the total film thickness of all the nitrogen-containing layers is less than 30nm, a given transmittance (40% or less) and a given retardation (150 degrees or more and 200 degrees or less) required for a phase shift film may not be obtained. The total film thickness of all the nitrogen-containing layers is preferably 35nm or more, and more preferably 40nm or more. On the other hand, the total thickness of all the nitrogen-containing layers provided in the phase shift film 2 is preferably 60nm or less, and more preferably 55nm or less.
The oxygen-containing layer is preferably formed of a material containing silicon and oxygen, or a material containing 1 or more elements selected from semimetal elements and nonmetallic elements, oxygen, and silicon. The oxygen-containing layer may contain any semimetallic element. It is preferable that the semimetal element contains 1 or more elements selected from boron, germanium, antimony, and tellurium because it is expected to improve the conductivity of silicon used as a sputtering target.
The oxygen-containing layer may contain any non-metallic element. The non-metal element in this case includes a non-metal element (nitrogen, carbon, oxygen, phosphorus, sulfur, selenium) in a narrow sense, a halogen, and a rare gas. Among the nonmetal elements, 1 or more elements selected from carbon, fluorine and hydrogen are preferably contained. The oxygen containing layer may contain a noble gas for the same reason as the nitrogen containing layer.
The total content of nitrogen and oxygen in the oxygen-containing layer is preferably 50 atomic% or more. Allowing for improved phase shiftThe degree of freedom in designing the film 2 (particularly, the transmittance) is preferably 50 atomic% or more, more preferably 55 atomic% or more, and still more preferably 60 atomic% or more of the total content of nitrogen and oxygen in the oxygen-containing layer. The total content of nitrogen and oxygen in the oxygen-containing layer is preferably 66 atomic% or less. If the nitrogen and oxygen contained in the nitrogen-containing layer are made to be SiO2、Si3N4When the mixing ratio of (A) is larger, it is difficult to form the oxygen-containing layer into an amorphous or microcrystalline structure. In addition, the surface roughness of the oxygen-containing layer is greatly deteriorated.
The oxygen-containing layer is preferably formed of a material containing silicon, nitrogen, and oxygen. In particular, when the degree of freedom of design of the phase shift film is increased in a region having high transmittance, the oxygen-containing layer may be formed of a material containing silicon and oxygen. In these cases, the material containing silicon, nitrogen, and oxygen, and the material containing silicon and oxygen are considered to include the material containing a rare gas.
The oxygen content of the oxygen-containing layer is preferably 15 atomic% or more. The extinction coefficient k of the silicon-based film is significantly reduced as compared with the case where the content of nitrogen is increased as the content of oxygen is increased. In the case of expanding the degree of freedom in designing the phase shift film in the region of high transmittance, the oxygen content of the oxygen-containing layer is preferably 15 atomic% or more, more preferably 20 atomic% or more, and still more preferably 25 atomic% or more.
The total thickness of all the oxygen-containing layers provided in the phase shift film 2 is preferably 10nm or more, more preferably 15nm or more, and still more preferably 20nm or more. On the other hand, the total thickness of all the oxygen-containing layers provided in the phase shift film 2 is preferably 50nm or less, and more preferably 45nm or less.
The nitrogen-containing layer and the oxygen-containing layer are most preferably amorphous structures for the reason that pattern edge roughness is good when a pattern is formed by etching. When the nitrogen-containing layer and the oxygen-containing layer have a composition in which an amorphous structure is difficult to form, the amorphous structure and the microcrystalline structure are preferably present in a mixed state.
The nitrogen-containing layer preferably has a refractive index n of 2.3 or more, more preferably 2.4 or more. The extinction coefficient k of the nitrogen-containing layer is preferably 0.5 or less, and more preferably 0.4 or less. On the other hand, the refractive index n of the nitrogen-containing layer is preferably 3.0 or less, more preferably 2.8 or less. The extinction coefficient k of the nitrogen-containing layer is preferably 0.16 or more, and more preferably 0.2 or more.
The refractive index n of the oxygen-containing layer is preferably 1.5 or more, more preferably 1.8 or more. The extinction coefficient k of the oxygen-containing layer is preferably 0.15 or less, and more preferably 0.1 or less. On the other hand, the refractive index n of the oxygen-containing layer is preferably 2.2 or less, more preferably 1.9 or less. The extinction coefficient k of the oxygen-containing layer is preferably 0 or more.
The refractive index n and the extinction coefficient k of the film are not determined solely by the composition of the film. The film density, the crystalline state, and the like of the thin film are also factors that affect the refractive index n and the extinction coefficient k. Therefore, the conditions for forming a thin film by reactive sputtering are adjusted so that the thin film has a desired refractive index n and an extinction coefficient k. In order to achieve the desired ranges of the refractive index n and the extinction coefficient k for the nitrogen-containing layer and the oxygen-containing layer, the ratio of the mixed gas of the rare gas and the reactive gas is not limited to the adjustment when the film is formed as a thin film by reactive sputtering. Further, the present invention relates to various aspects such as the pressure in the film forming chamber, the power applied to the target, and the positional relationship such as the distance between the target and the transparent substrate 1 when a thin film is formed by reactive sputtering. These film forming conditions are inherent in the film forming apparatus, and are appropriately adjusted so that the formed thin film has a desired refractive index n and an extinction coefficient k.
The nitrogen-containing layer and the oxygen-containing layer can be formed by sputtering, and any of DC sputtering, RF sputtering, ion beam sputtering, and the like can be applied. When a target having low conductivity (a silicon target, a silicon compound target containing no semimetal element or a small amount of semimetal element, or the like) is used, RF sputtering or ion beam sputtering is preferably used, but in view of the film formation rate, RF sputtering is more preferably used.
When the film stress of the phase shift film 2 is large, there is a problem that the positional shift of the transfer pattern formed on the phase shift film 2 becomes large when the phase shift mask is manufactured from the mask blank. The film stress of the phase shift film 2 is preferably 275MPa or less, more preferably 165MPa or less, and further preferably 110MPa or less. The phase shift film 2 formed by the sputtering described above has a relatively large film stress. Therefore, it is preferable to reduce the film stress of the phase shift film 2 by performing a heating process, a light irradiation process using a flash lamp or the like on the phase shift film 2 formed by sputtering, or the like.
The mask blank 100 preferably includes a light shielding film 3 on the phase shift film 2. In general, in the phase shift mask 200 (see fig. 2F), it is required that the outer peripheral region of the region where the transfer pattern is to be formed (transfer pattern forming region) ensure an Optical Density (OD) of a predetermined value or more so that the resist film is not affected by exposure light transmitted through the outer peripheral region when the resist film transferred onto the semiconductor wafer is exposed by an exposure apparatus. It is also required for the peripheral region of the phase shift mask 200 to have an optical density of at least more than 2.0. As described above, the phase shift film 2 has a function of transmitting the exposure light at a predetermined transmittance, and it is difficult to ensure the above-described optical density only by the phase shift film 2. Therefore, it is desirable to laminate the light shielding film 3 on the phase shift film 2 in advance at the stage of manufacturing the mask blank 100 to ensure insufficient optical density. By adopting such a configuration of the mask blank 100, if the light shielding film 3 in the region where the phase shift effect is used (substantially, the transfer pattern forming region) is removed in the process of manufacturing the phase shift film 2, the phase shift mask 200 in which the above-described optical density is secured in the peripheral region can be manufactured. In the mask blank 100, the optical density in the laminated structure of the phase shift film 2 and the light shielding film 3 is preferably 2.5 or more, and more preferably 2.8 or more. In order to reduce the thickness of the light-shielding film 3, the optical density in the laminated structure of the phase shift film 2 and the light-shielding film 3 is preferably 4.0 or less.
The light-shielding film 3 may have a single-layer structure or a laminated structure of 2 or more layers. Each layer of the light-shielding film 3 having a single-layer structure and the light-shielding film 3 having a laminated structure of 2 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 layer.
In the case where no other film is interposed between the light-shielding film 3 and the phase-shift film 2, it is necessary to use a material having sufficient etching selectivity to the etching gas used in patterning the phase-shift film 2. In this case, the light-shielding film 3 is preferably formed of a material containing chromium. As a material containing chromium for forming the light-shielding film 3, in addition to chromium metal, a material containing chromium and at least one element selected from oxygen, nitrogen, carbon, boron, and fluorine is cited.
In general, a mixed gas of a chlorine-based gas and an oxygen gas is used to etch a chromium-based material, 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 etching gas with respect to the mixed gas of the chlorine-based gas and the oxygen gas, it is preferable to use a material containing chromium and one or more elements selected from oxygen, nitrogen, carbon, boron, and fluorine as the material for forming the light-shielding film 3. Further, the material containing chromium which forms the light-shielding film 3 may contain one or more elements selected from molybdenum and tin. By containing one or more elements of molybdenum, indium, and tin in the material containing chromium, the etching rate with respect to a mixed gas of a chlorine-based gas and oxygen can be further increased.
On the other hand, when the
The material containing silicon for forming the light-shielding film 3 may contain a transition metal or may contain a metal element other than a transition metal. This is because, when the phase shift mask 200 is produced from the mask blank 100, the pattern formed by the light-shielding film 3 is basically a light-shielding band pattern in the outer peripheral region, and the accumulation amount of ArF exposure light to be irradiated is small compared to the transfer pattern formation region, or the light-shielding film 3 remains in a fine pattern is small, and even if ArF light resistance is low, a substantial problem is not easily caused. Further, if the light-shielding film 3 contains a transition metal, the light-shielding performance is greatly improved as compared with the case where the transition metal is not contained, and the thickness of the light-shielding film can be reduced. The transition metal contained in the light-shielding film 3 may be any one of molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), chromium (Cr), hafnium (Hf), nickel (Ni), vanadium (V), zirconium (Zr), ruthenium (Ru), rhodium (Rh), niobium (Nb), palladium (Pd), or an alloy of these metals.
On the other hand, as a material containing silicon which forms the light-shielding film 3, a material containing silicon and nitrogen, or a material containing 1 or more elements selected from semimetallic elements and nonmetallic elements in the material containing silicon and nitrogen can be applied.
More preferably, the following structure is adopted: in the mask blank 100 including the light-shielding film 3 laminated on the phase shift film 2, the hard mask film 4 is further laminated on the light-shielding film 3, and the hard mask film 4 is formed of a material having etching selectivity to an etching gas used for etching the light-shielding film 3. The light-shielding film 3 must have a function of ensuring a given optical density, and therefore, there is a limit to thinning the thickness thereof. The hard mask film 4 is not limited to optical characteristics, as long as it has a film thickness capable of functioning as an etching mask until the dry etching for forming a pattern on the light-shielding film 3 immediately below the hard mask film is completed. Therefore, the thickness of the hard mask film 4 can be made much smaller than the thickness of the light-shielding film 3. Further, since it is sufficient that the resist film of an organic material has a film thickness that functions only as an etching mask until the dry etching for forming a pattern on the hard mask film 4 is completed, the resist film can be made thinner than before.
When the light-shielding film 3 is formed of a material containing chromium, the hard mask film 4 is preferably formed of a material containing silicon as described above. In this case, since the hard mask film 4 tends to have low adhesion to a resist film made of an organic material, it is preferable to perform hmds (hexamethyldisilazane) treatment on the surface of the hard mask film 4 to improve the adhesion on the surface. In this case, the hard mask film4 is more preferably made of SiO2SiN, SiON, etc. In addition, as the material of the hard mask film 4 in the case where the light-shielding film 3 is formed of a material containing chromium, a material containing tantalum may be used in addition to the above-described materials. In this case, the material containing tantalum includes, in addition to tantalum metal, a material in which tantalum contains one or more elements selected from nitrogen, oxygen, boron, and carbon. Examples of such materials include: ta, TaN, TaON, TaBN, TaBON, TaCN, TaCON, TaBCN, TaBOCN, etc. On the other hand, when the light-shielding film 3 is formed of a material containing silicon, the hard mask film 4 is preferably formed of the material containing chromium.
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 DRAM hp32nm generation, SRAF (Sub-Resolution assist feature) having a line width of 40nm may be provided in a transfer pattern (phase shift pattern) to be formed on the hard mask film 4. However, even in this case, the cross-sectional aspect ratio of the resist pattern can be as low as 1:2.5, and therefore, the resist pattern can be suppressed from being damaged or detached at the time of development of the resist film, at the time of rinsing, or the like. The thickness of the resist film is more preferably 80nm or less.
Fig. 2 is a schematic cross-sectional view illustrating a process of manufacturing a phase shift mask 200 from the mask blank 100 according to the embodiment of the present invention.
A phase shift mask 200 of the present invention is a phase shift mask 200 comprising a phase shift film 2 (phase shift pattern 2a) having a transfer pattern formed on a transparent substrate 1, wherein the phase shift film 2 (phase shift pattern 2a) comprises at least a nitrogen-containing layer and an oxygen-containing layer, the oxygen-containing layer is formed of a material containing silicon and oxygen or a material containing 1 or more elements selected from the group consisting of semimetallic elements and nonmetallic elements, oxygen and silicon, the nitrogen-containing layer is formed of a material containing silicon and nitrogen or a material containing 1 or more elements selected from the group consisting of nonmetallic elements and semimetallic elements, nitrogen and silicon, the nitrogen-containing layer is subjected to X-ray photoelectron spectroscopy to obtain a maximum peak PSi _ f of photoelectron intensity of narrow spectrum Si2p in the nitrogen-containing layer, the transparent substrate 1 is subjected to X-ray photoelectron spectroscopy to obtain a maximum peak PSi _ s of photoelectron intensity of narrow spectrum Si2p in the transparent substrate 1, in this case, the value (PSi _ f)/(PSi _ s) obtained by dividing the maximum peak PSi _ f in the nitrogen-containing layer by the maximum peak PSi _ s in the transparent substrate is 1.09 or less.
The phase shift mask 200 has the same technical features as the
An example of a method for manufacturing the phase shift mask 200 will be described below according to the manufacturing process shown in fig. 2. In this example, a material containing chromium is used for the light-shielding film 3, and a material containing silicon is used for the hard mask film 4.
First, a resist film is formed by spin coating in contact with the hard mask film 4 in the
Next, after removing the resist pattern 5a, dry etching using a mixed gas of a chlorine-based gas and an oxygen gas is performed using the hard mask pattern 4a as a mask, thereby forming a 1 st pattern (light-shielding pattern 3a) in the light-shielding film 3 (see fig. 2C). Next, dry etching using a fluorine-based gas is performed using the light-shielding pattern 3a as a mask to form the 1 st pattern (phase shift pattern 2a) on the phase shift film 2 and remove the hard mask pattern 4a (see fig. 2D).
Next, a resist film is formed on the mask blank 100 by a spin coating method. Next, a 2 nd pattern as a pattern (light shielding pattern) to be formed on the light shielding film 3 is drawn against resist exposure, and a given process such as a development process is further performed, and a 2 nd resist pattern 6b having a light shielding pattern is formed. Next, dry etching using a mixed gas of a chlorine-based gas and an oxygen gas is performed using the 2 nd resist pattern 6b as a mask, and the 2 nd pattern (light-shielding pattern 3b) is formed on the light-shielding film 3 (see fig. 2E). Further, the 2 nd resist pattern 6b is removed and subjected to a predetermined process such as cleaning, thereby obtaining a phase shift mask 200 (see fig. 2F).
The chlorine-based gas used in the dry etching is not particularly limited as long as it contains Cl. Examples of the chlorine-based gas include: cl2、SiCl2、CHCl3、CH2Cl2、CCl4、BCl3And the like. The fluorine-based gas used in the dry etching is not particularly limited as long as it contains F. Examples thereof include: CHF3、CF4、C2F6、C4F8、SF6And the like. In particular, since the etching rate of the fluorine-based gas containing no C with respect to the transparent substrate 1 made of a glass material is relatively low, damage to the transparent substrate 1 can be further reduced.
The method for manufacturing a semiconductor device according to the present invention is characterized in that a pattern is exposed and transferred to a resist film on a semiconductor substrate by using the phase shift mask 200 manufactured using the
On the other hand, another embodiment of the present invention includes a mask blank having the following configuration. That is, the mask blank according to the other embodiment is characterized in that: a phase shift film is provided on a light-transmitting substrate, the phase shift film being a single layer film having a composition gradient portion in which the oxygen content increases in a region on the surface opposite to the light-transmitting substrate and in the vicinity thereof, the phase shift film being formed of a material containing silicon and nitrogen, or a material containing 1 or more elements selected from nonmetallic elements and semimetallic elements, nitrogen, and silicon, and X-ray photoelectron spectroscopy is performed on the phase shift film to obtain a maximum peak PSi _ f of photoelectron intensity of a narrow spectrum of Si2p in the phase shift film, and X-ray photoelectron spectroscopy is performed on the light-transmitting substrate to obtain a maximum peak PSi _ s of photoelectron intensity of a narrow spectrum of Si2p in the light-transmitting substrate, and when a value (PSi _ f)/(PSi _ s) obtained by dividing the maximum peak PSi _ f in the phase shift film by the maximum peak PSi _ s in the light-transmitting substrate is 1.09 or less.
The region other than the composition gradient portion of the phase shift film has the same characteristics as the nitrogen-containing layer of the phase shift film of the present invention. In addition, the composition gradient portion of the phase shift film has a large oxygen content, and thus ArF light resistance and chemical resistance are also increased. Therefore, the mask blank according to the other embodiment has high ArF light resistance and chemical resistance as a whole of the phase shift film, as compared with a conventional mask blank having a single-layer phase shift film made of a silicon nitride material. Other implementations of the phase-shift film according to the other embodiment are the same as those of the nitrogen-containing layer in the phase-shift film according to the embodiment of the present invention.
Further, a phase shift mask according to another embodiment having the same features as those of the mask blank according to the above-described another embodiment can be exemplified. That is, the phase shift mask according to the other embodiment is characterized by comprising a phase shift film having a transfer pattern formed thereon, the phase shift film being a single layer film having a composition gradient portion in which the oxygen content increases in a region on the surface opposite to the transparent substrate and in the vicinity thereof, the phase shift film being formed of a material containing silicon and nitrogen, or a material containing 1 or more elements selected from non-metal elements and semimetal elements, nitrogen and silicon, performing X-ray photoelectron spectroscopy analysis on the phase shift film to obtain a maximum peak PSi _ f of photoelectron intensity of Si2p narrow spectrum in the phase shift film, and X-ray photoelectron spectroscopy is performed on the light-transmitting substrate to obtain a maximum peak PSi _ s of photoelectron intensity of narrow spectrum of Si2p in the light-transmitting substrate, the value (PSi _ f)/(PSi _ s) obtained by dividing the maximum peak PSi _ f in the phase shift film by the maximum peak PSi _ s in the light-transmitting substrate is 1.09 or less.
As in the case of the mask blank of the above-described another embodiment, the phase shift mask of the another embodiment has high ArF light resistance and chemical resistance as a whole of the phase shift film as compared with a conventional phase shift mask having a single-layer phase shift film made of a silicon nitride-based material. In addition, even when the phase shift mask according to the other embodiment is disposed on the mask stage of the exposure apparatus using ArF excimer laser light as exposure light to expose and transfer the phase shift pattern to the resist film on the semiconductor device, the pattern can be transferred to the resist film on the semiconductor device with a precision that sufficiently satisfies the design specification.
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