TW202125089A - Mask blank, transfer mask, and method for manufacturing a semiconductor device - Google Patents

Abstract

To provide a mask blank which is capable of improving an etching rate of a pattern-forming thin film as a whole for wet etching and increasing verticality of a pattern side wall when a pattern is formed on the thin film by wet etching. The mask blank includes a pattern-forming thin film formed on a substrate. The thin film is made of a material containing chromium. The thin film has an upper region on the side opposite to the substrate and the other region except the upper region. Herein, the upper region has a crystal size greater than that of the other region except the upper region.

Description

Photomask substrate, photomask for transfer printing, and manufacturing method of semiconductor device

The present invention relates to a photomask for transfer used in the manufacture of semiconductor devices, a photomask base for making the photomask for transfer, and a method for manufacturing a semiconductor device using the photomask for transfer.

Generally speaking, in the manufacturing steps of semiconductor devices, photolithography is used to form fine patterns. In the formation of this fine pattern, a substrate called a photomask (a photomask for transfer) is generally used. The photomask is usually provided with a light-shielding fine pattern formed of a metal thin film or the like on a light-transmitting glass substrate. The photolithography method is also used in the manufacture of the mask.

When manufacturing a photomask by photolithography, it is used for a photomask base having a light-shielding film on a translucent substrate (hereinafter, sometimes referred to as a substrate) such as a glass substrate. When using the photomask substrate to manufacture a photomask, the following steps are performed: a drawing step, which is to perform the required pattern drawing on the resist film formed on the photomask substrate; The film is developed to form a resist pattern; the etching step is to etch the above-mentioned light-shielding film using the resist pattern as a mask; and the peeling removal step is to peel off the remaining resist pattern. In the above-mentioned etching step, the resist pattern is used as a mask, and the exposed part of the light-shielding film without the resist pattern is dissolved by, for example, wet etching, thereby forming the required mask on the translucent substrate pattern. The photomask is completed in this way.

In Patent Document 1, as a photomask substrate suitable for wet etching, a photomask substrate provided with a light-shielding film of a chromium-based material is disclosed. It is disclosed that the light-shielding film is, for example, a laminated structure of a first light-shielding film (CrN)/second light-shielding film (CrC)/anti-reflection film (CrON) from the substrate side.

In addition, Patent Document 2 also discloses a photomask substrate provided with a light-shielding film of a laminated structure of chromium-based materials as a photomask base suitable for wet etching. It is disclosed that the light-shielding film is, for example, a laminated structure of the first layer (chromium film)/the second layer (chromium oxide and chromium nitride mixed film) from the substrate side, or the first layer (chromium oxide and chromium nitride mixed film). Composition film) / 2nd layer (chromium film) / 3rd layer (chromium oxide, chromium nitride mixed composition film) laminated structure. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 3276954 [Patent Document 2] Japanese Patent Publication No. 61-46821

[The problem to be solved by the invention]

When the chromium-based material film is patterned by wet etching (hereinafter referred to as "wet etching") using an etching solution with cerium ammonium nitrate as the main component, the etching rate of the chromium oxide film is relatively high. The tendency of chromium metal film to be slow.

When a chromium metal film is formed on a substrate by sputtering as a thin film for pattern formation to manufacture a mask base, in the subsequent manufacturing process, it is unavoidable that the thin film is formed from the surface opposite to the substrate side. Oxidation.

For example, after a thin film is formed on a substrate, it is generally washed with water to remove defects and other purposes. At this time, oxygen enters from the surface of the thin film (oxidation progresses in the upper region of the thin film). When using this photomask base to manufacture a photomask for transfer, the film is patterned by wet etching using a resist pattern as an etching mask. In the step of forming the resist film on the film, the following operations are performed, that is, after the resist solution is applied to the surface of the film, the entire photomask substrate is baked, thereby hardening the applied resist . During the baking process, oxygen enters from the surface of the film (the oxidation of the upper region of the film further progresses).

Generally speaking, for the pattern forming film of the photomask substrate, it is required to have a low surface reflectivity to the exposure light (the exposure light irradiated when the transfer mask made from the photomask substrate is set in the exposure device). . The surface layer (upper region) of the film contains nitrogen, which may reduce the surface reflectance of the exposed light to some extent, but the surface reflectance is often insufficient. If oxygen is contained in the upper region of the film, the surface reflectance to the exposed light can be greatly reduced. However, in order to obtain the effect of sufficiently reducing the surface reflectance, it is necessary to make the upper region of the film contain more oxygen. Since the upper region of the film contains a lot of oxygen, the structure becomes amorphized and becomes dense, and the etching rate for wet etching becomes slow, which becomes a problem when forming patterns on the film.

On the other hand, it is desirable that the etching rate of the substrate side area (lower area) of the patterning film for wet etching is faster than the etching rate of the inner area (middle area) of the film. Generally speaking, wet etching has a strong tendency to isotropic etching. Therefore, when wet etching is performed from the surface of the film on the opposite side to the substrate side to the surface of the substrate side, the sidewall of the film pattern tends to be tapered (the line width of the film pattern expands toward the substrate side). Therefore, generally speaking, after the thin film is wet-etched until the surface of the substrate is exposed, the etching (so-called over-etching) that is mainly used to advance the etching in the sidewall direction of the lower part of the thin film is also continued. However, in the isotropic wet etching, only the undercut becomes larger, and the verticality of the sidewall of the thin film pattern cannot be improved. Therefore, it is desirable to increase the etching rate in the lower region of the film. Here, improving the verticality of the sidewall of the thin film pattern means that the cross-sectional shape of the thin film pattern is processed to be close to vertical with respect to the film surface.

The present invention is completed in order to solve the previous problems, and its purpose is to provide a photomask substrate, which can increase the etching rate of the patterning film as a whole for wet etching, thereby improving the patterning of the film by wet etching. The verticality of the sidewall of the pattern at the time. In addition, the object of the present invention is also to provide a photomask for transfer with improved verticality of the sidewalls of the film pattern. Furthermore, the object of the present invention is also to provide a method of manufacturing a semiconductor device using the transfer mask. [Technical means to solve the problem]

As described above, in view of the previous difficulty in performing good final processing of the cross-sectional shape of the thin film pattern formed by the wet etching process, the inventors conducted intensive research and found that, for example, The substrate side is the upper area on the opposite side and the area other than the upper area. Adjusting the crystal size of the chromium-based material constituting the patterning film can increase the etching rate of the entire patterning film for wet etching, thereby increasing the The verticality of the sidewalls of the pattern when the film is patterned by wet etching.

That is, in order to solve the above-mentioned problems, the present invention has the following configuration. (Composition 1) A photomask base, characterized in that it is provided with a patterning film on a substrate, the film includes a material containing chromium, and the film includes an upper region on the side opposite to the substrate and a region other than the upper region , The crystal size of the upper region is larger than the crystal size of the regions other than the upper region.

(Composition 2) The mask substrate as described in Composition 1, characterized in that the upper region of the film and the regions other than the upper region are both polycrystalline structures. (Composition 3) The mask substrate as described in Composition 1 or 2, characterized in that the crystal plane spacing between the upper region of the thin film obtained by the electron diffraction method and the region other than the upper region is 0.2 nm or more.

(Composition 4) The mask substrate described in any one of compositions 1 to 3 is characterized in that both the upper region of the film and the region other than the upper region have a columnar structure. (Composition 5) The mask base described in any one of compositions 1 to 4 is characterized in that the area except the upper area of the film includes two areas from the substrate side, the lower area and the middle area, and the crystal size of the film It increases in the order of the middle area, lower area, and upper area.

(Composition 6) The mask substrate according to any one of compositions 1 to 5, wherein the thin film is a composition gradient film in which the content of the chromium varies in the thickness direction. (Composition 7) The mask base described in any one of compositions 1 to 6, characterized in that the above-mentioned film is a light-shielding film having an optical density of 3 or more with respect to exposure light.

(Composition 8) A photomask for transfer, characterized in that it is provided with a film with a transfer pattern on a substrate, and the film includes a material containing chromium, and the film includes an upper region on the opposite side of the substrate and except for the upper part In the area outside the area, the crystal size of the upper area is larger than the crystal size of the area except the upper area.

(Composition 9) The transfer mask as described in Composition 8, characterized in that the upper region of the film and the regions other than the upper region are both polycrystalline structures. (Composition 10) The transfer mask as described in Composition 8 or 9, characterized in that the distance between the crystal planes of the upper region of the film and the region other than the upper region obtained by the electron diffraction method is 0.2 nm or more.

(Composition 11) The transfer mask described in any one of compositions 8 to 10 is characterized in that both the upper region of the film and the region other than the upper region have a columnar structure. (Composition 12) The transfer mask described in any one of compositions 8 to 11 is characterized in that the area other than the upper area of the film includes two areas from the substrate side, the lower area and the middle area. The crystal size increases in the order of the middle region, the lower region, and the upper region.

(Composition 13) The transfer mask according to any one of compositions 8 to 12, wherein the thin film is a composition gradient film in which the content of the chromium changes in the thickness direction. (Composition 14) The transfer mask described in any one of compositions 8 to 13, wherein the thin film is a light-shielding film having an optical density of 3 or more with respect to exposure light.

(Composition 15) A method of manufacturing a semiconductor device is characterized by comprising the step of exposing a transfer pattern to a resist film on a semiconductor substrate using the transfer mask as described in any one of Compositions 8 to 14. [Effects of Invention]

According to the present invention, a photomask substrate can be provided, which can increase the etching rate of the entire patterning film for wet etching, and further improve the verticality of the pattern sidewalls when the film is patterned by wet etching. Furthermore, according to the present invention, it is possible to provide a photomask for transfer with improved verticality of the side wall of the film pattern. Furthermore, according to the present invention, it is possible to provide a method of manufacturing a semiconductor device, which can form a good transfer pattern using the above-mentioned transfer mask.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Mask base] First, the photomask substrate of the present invention will be described. Fig. 1 is a cross-sectional view showing an embodiment of the photomask substrate of the present invention. The photomask base 10 shown in FIG. 1 is a photomask base in the form of a film 2 for pattern formation on a substrate 1.

The photomask substrate 10 of this embodiment is characterized in that the above-mentioned thin film 2 contains a material containing chromium. In addition, the thin film 2 includes two regions, an upper region on the opposite side to the substrate 1 side and a region other than the upper region. The crystal size of the upper region is larger than the crystal size of the regions other than the upper region.

Here, as the above-mentioned substrate 1, a translucent substrate is suitable. As this translucent substrate, a glass substrate is generally mentioned. The glass substrate is excellent in flatness and smoothness. Therefore, when pattern transfer is performed on the substrate to be transferred using a transfer mask, high-precision pattern transfer can be performed without distortion of the transferred pattern. As the translucent substrate, in addition to synthetic quartz glass, it can be formed of glass materials such as quartz glass, aluminosilicate glass, soda lime glass, low thermal expansion glass (SiO ₂ -TiO _{2 glass, etc.).} Among them, synthetic quartz glass, for example, has a relatively high transmittance for ArF excimer laser light (wavelength 193 nm) used as exposure light, and is particularly suitable as a material for the substrate 1 forming the mask base 10.

The thin film 2 for pattern formation includes a material containing chromium, for example, a light-shielding film. Specific examples of the material of the above-mentioned thin film 2 include chromium simple substance, or chromium compound materials containing elements such as oxygen, nitrogen, and carbon in chromium. The material constituting the film 2 preferably does not contain elements such as silicon that greatly reduce the wet etching rate. In the material constituting the thin film 2, the total content of chromium and non-metallic elements is preferably 95 atomic% or more, more preferably 98 atomic% or more, and still more preferably 99 atomic% or more. In addition, in the material constituting the thin film 2, the total content of chromium, oxygen, nitrogen, and carbon is preferably 95 atomic% or more, more preferably 98 atomic% or more, and still more preferably 99 atomic% or more. In this embodiment, the thickness of the film 2 is not particularly limited, but it is preferably in the range of 80 nm to 150 nm.

As described above, in this embodiment, the thin film 2 includes two regions, an upper region on the side opposite to the substrate 1 side and a region other than the upper region. For the pattern forming film 2 in the photomask substrate 10, it is required that the surface reflectance of the exposure light (the exposure light irradiated when the transfer mask manufactured by the photomask substrate 10 is set in the exposure device) is low . Therefore, in the present embodiment, it is preferable that the upper region has an anti-reflection function. By making the upper region of the film 2 contain, for example, nitrogen, the surface reflectance to the exposed light can be reduced to some extent. In addition, if oxygen is contained in the upper region of the thin film 2, the surface reflectance to the exposure light can be significantly reduced. Therefore, materials such as CrO, CrON, CrOC, CrOCN, etc. can be preferably used in the upper region of the above-mentioned film 2. In this case, the surface reflectivity of the above-mentioned film 2 to the exposed light can be considered, and the content of oxygen or nitrogen can be appropriately adjusted. In this embodiment, the thickness of the upper region of the thin film 2 is not particularly limited, but it is preferably in the range of 10 nm to 50 nm.

Furthermore, in order to improve the light-shielding performance of the entire film 2 against exposure light, the area of the film 2 except for the upper area preferably has a lower oxygen content than the upper area of the film 2, and more preferably contains substantially no oxygen. In addition, the chromium content of the regions other than the upper region of the film 2 is preferably more than the chromium content of the upper region of the film 2. The area of the film 2 except for the upper area may preferably use materials such as Cr, CrN, CrC, CrCN, and the like.

The photomask substrate 10 of this embodiment is characterized in that the crystal size of the upper region of the thin film 2 is larger than the crystal size of the region except the upper region. When the thin film 2 of chromium-based material is patterned by wet etching, the part with larger crystal size is easier for the wet etching solution to penetrate into the film, and the wet etching rate increases. The upper region of the film 2 is easy to oxidize and needs to contain oxygen in order to have the surface anti-reflection function. It is known that if oxygen is contained in chromium, the wet etching rate decreases. In the present invention, by making the crystal size of the upper region larger than the crystal size of regions other than the upper region, the wet etching rate of the upper region can be increased. That is, the crystal size of the upper region in the film 2 is made larger than the crystal size of the regions other than the upper region, thereby making the upper region of the pattern forming film 2 have a higher etching rate for wet etching. Areas other than the upper area are fast. The cross-sectional shape of the thin film pattern formed by wet etching is preferably as vertical as possible with respect to the film surface. With the above configuration, the overall etching rate of the thin film 2 can be increased, and the wetness of the thin film 2 can be improved. Verticality of the sidewalls of the pattern when the pattern is formed by the method of etching.

In this embodiment, it is preferable that the upper region of the thin film 2 and the regions other than the upper region have a polycrystalline structure. By setting each region of the above-mentioned thin film 2 to a polycrystalline structure in which various crystals of chromium metal or chromium compound are mixed, the crystal size is not likely to be too large. In addition, the line edge roughness of the pattern sidewall when the film 2 is patterned can be reduced.

Furthermore, in this embodiment, it is preferable that the upper region of the thin film 2 obtained by the electron diffraction method and the regions other than the upper region each have a crystal plane spacing of 0.2 nm or more. If the distance between the crystal planes is small, a tighter crystal structure will be formed, but the wet etching rate will be excessively reduced, making it difficult to increase the etching rate of the entire thin film 2.

Furthermore, in this embodiment, it is preferable that both the upper region of the film 2 and the regions other than the upper region have a columnar structure. Each area of the above-mentioned film 2 has a columnar structure, which makes it easier for the wet etching liquid to penetrate into the film 2, so that the wet etching rate is further improved.

When the thin film 2 is formed by, for example, sputtering, the crystal size of each region of the thin film 2 can be controlled by controlling the pressure of the sputtering gas introduced into the chamber, or the temperature in the chamber, the film formation rate, and the application The voltage and current value to the target can be adjusted.

The method for forming the above-mentioned thin film 2 does not need to be particularly limited, and a preferred method may be a sputtering film formation method. According to the sputtering film forming method, a film with uniform in-plane distribution and a fixed film thickness can be formed. When the thin film 2 is formed on the substrate 1 by sputtering, a chromium (Cr) target is used as the sputtering target, and the sputtering gas introduced into the chamber is an inert gas such as argon or helium. The gas is mixed with oxygen, nitrogen, carbon dioxide gas, nitric oxide gas, etc. If you use a sputtering gas made by mixing oxygen or carbon dioxide with an inert gas such as argon, a thin film containing oxygen in chromium can be formed. If you use a sputtering gas made by mixing nitrogen with an inert gas such as argon, it can be A thin film containing nitrogen in chromium is formed. In addition, if a sputtering gas formed by mixing nitric oxide gas with an inert gas such as argon gas is used, a thin film containing nitrogen and oxygen in chromium can be formed. Furthermore, if a sputtering gas formed by mixing methane gas with an inert gas such as argon gas is used, a thin film containing carbon in chromium can be formed.

In addition, in this embodiment, the above-mentioned thin film 2 is preferably a compositionally graded film in which the content of chromium changes in the thickness direction. Thereby, when a pattern is formed on the thin film 2 by wet etching, the sidewall shape of the pattern is not easy to produce a step difference. In order to make such a thin film 2 a compositionally graded film, for example, a method of appropriately changing the type (composition) of the sputtering gas during film formation during film formation is suitable.

In addition, in this embodiment, the thin film 2 can be, for example, a light-shielding film that has an optical density of 3 or more with respect to exposure light and includes the chromium-based material. Furthermore, the exposure light to be irradiated to the transfer mask manufactured from the mask substrate of the present embodiment includes, for example, light containing g-ray (wavelength approximately 436 nm), and light containing i-ray (wavelength approximately 365 nm). Light, KrF excimer laser light (wavelength approximately 248 nm) and ArF excimer laser light (wavelength approximately 193 nm).

On the other hand, the thin film 2 of this embodiment can be used as a light-shielding film in a mask base having a structure in which a semi-transparent film and a light-shielding film are sequentially laminated on the substrate 1. In this case, it is preferable to use a laminated structure of a semi-transmissive film and a light-shielding film so that the optical density to the above-mentioned exposed light is 3 or more. In this case, the semi-transmissive film is preferably a phase shift film having the following functions, namely: the function of transmitting the exposed light with a specific transmittance (for example, a transmittance of 1% or more and 30% or less); and The function of generating a specific phase difference (for example, a phase difference of 150 degrees or more and 210 degrees or less) between the exposure light passing through the film and the exposure light passing through the air at a distance equal to the thickness of the film.

Next, other embodiments will be described. In other embodiments, the region other than the upper region of the thin film 2 of the above embodiment further includes two regions, the lower region and the middle region from the substrate 1 side. That is, in other embodiments, the above-mentioned thin film 2 including a material containing chromium includes three regions, namely, a lower region, a middle region, and an upper region from the side of the substrate 1. In this case, it is preferable that the crystal size of the above-mentioned thin film 2 increases in the order of the middle region, the lower region, and the upper region.

As described above, when the thin film 2 of chromium-based material is patterned by wet etching, the part with larger crystal size is easier for the wet etching solution to penetrate into the thin film, and the wet etching rate increases. The upper region of the film 2 is easy to oxidize and needs to contain oxygen in order to have the surface anti-reflection function. It is known that if oxygen is contained in chromium, the wet etching rate decreases. In other embodiments, by making the crystal size of the upper region the largest in the entire film 2, the wet etching rate in the upper region can be increased. In addition, previously, in the case of wet etching, the verticality of the sidewall shape of the pattern formed on the film 2 tends to be low. Therefore, it is desired to increase the wet etching rate of the area on the substrate 1 side of the film 2 (the above-mentioned lower area) . In other embodiments, by making the crystal size of the lower region of the film 2 larger than the crystal size of the inner portion of the film 2 except for the upper region and the lower region (the above-mentioned middle region), the wet etching rate of the lower region can be increased. In this way, by increasing the crystal size of the thin film 2 in the order of the middle region, the lower region, and the upper region, the verticality of the pattern sidewalls when the pattern is formed by wet etching can be improved.

As described above, by using the configuration of the mask base of other embodiments, the wet etching rate of each area in the patterning film 2 can be increased in the order of the middle area, the lower area, and the upper area. As a result, the overall etching rate of the film 2 of the photomask substrate 10 is increased, and the verticality of the pattern sidewalls when the film 2 is patterned by wet etching can be improved.

The upper region of the thin film 2 can be made of the same chromium-based material as in the case of the above-mentioned embodiment. In order to improve the light-shielding performance of the entire film 2 against exposure light, the middle region of the film 2 preferably has less oxygen content than the upper and lower regions of the film 2, and more preferably contains substantially no oxygen. In addition, the chromium content in the middle region of the film 2 is preferably more than the chromium content in the upper and lower regions of the film 2. The middle region of the film 2 can preferably use materials such as Cr, CrN, CrC, CrCN, and the like.

In order to improve the light-shielding performance of the film 2 as a whole to the exposure light, the lower region of the film 2 preferably has a lower oxygen content than the upper region of the film 2. In addition, in order to reduce the reflectance of the back side of the film 2 (the side that is in contact with the substrate), the lower region of the film 2 preferably has a higher nitrogen content than the upper and middle regions of the film 2. The lower region of the film 2 can preferably use materials such as CrN, CrCN, and CrON.

In other embodiments, the thickness of the upper region of the thin film 2 is not particularly limited, but it is preferably in the range of 10 nm to 50 nm. The thickness of the middle region of the above-mentioned film 2 is not particularly limited, but in order to improve the light shielding performance of the entire film 2 against exposure light, the range of 25 nm to 70 nm is appropriate. The thickness of the lower region of the film 2 is not particularly limited, but in order to reduce the reflectivity on the back side of the film 2, the range of 5 nm to 30 nm is preferable.

Regarding other embodiments, for the same reasons as in the above-mentioned embodiment, it is preferable that the lower region, the middle region, and the upper region of the thin film 2 are all polycrystalline structures.

Regarding the other embodiments, based on the same reason as the above-mentioned embodiment, it is preferable that the crystal plane spacing of the lower region, middle region, and upper region of the thin film 2 obtained by the electron diffraction method is 0.2 nm or more. .

Regarding other embodiments, for the same reasons as in the above-mentioned embodiment, it is preferable that the lower region, the middle region, and the upper region of the thin film 2 all have a columnar structure.

Regarding other embodiments, for the same reasons as in the above embodiment, it is preferable that the thin film 2 is a compositionally graded film in which the content of chromium changes in the thickness direction. Regarding other embodiments, the above-mentioned thin film 2 may also be a light-shielding film that has an optical density of 3 or more with respect to exposure light and includes a chromium-based material. The other matters regarding the mask substrate of the other embodiments are the same as the case of the mask substrate of the above-mentioned embodiment.

As explained by the above embodiments, according to the photomask substrate of the present invention, the etching rate of the entire patterning film for wet etching can be increased, thereby increasing the verticality of the pattern sidewalls when the film is patterned by wet etching. .

In each of the above embodiments, the mask base in the form in which the pattern forming film 2 is provided on the substrate 1 has been described, but the present invention is not limited to this embodiment. For example, the mask base of the present invention also includes the following aspects, that is, between the light-transmitting substrate 1 and the pattern forming film (light-shielding film) 2 and further having a specific transmittance (for example, 1 % Above 40% (transmittance below 40%)) a semi-transmissive film with the function of transmitting. The semi-transmissive film may also be a phase shift film that further has the following functions, namely, the exposure of light passing through the interior of the semi-transmissive film and exposure in the air through a distance equal to the thickness of the semi-transmissive film A specific phase difference (for example, a phase difference of 150 degrees or more and 210 degrees or less) is generated between the lights. In the case of these structures, it is preferable to use a laminated structure of a semi-transparent film (or a phase shift film) and a light-shielding film so that the optical density of the above-mentioned exposed light is 3 or more.

On the other hand, the photomask substrate of the present invention is not limited to the use of a transfer photomask used in the manufacture of semiconductor devices. For example, the photomask substrate of the present invention can also be applied to manufacture FPD (Flat Panel Display) represented by LCD (Liquid Crystal Display, liquid crystal display device), OLED (Organic Light Emitting Diode, organic light emitting diode), etc. Flat panel displays) and other display devices used for transfer masks.

[Photomask for Transfer] Next, the transfer mask of the present invention will be described. Fig. 2 is a cross-sectional view showing an embodiment of the transfer mask of the present invention. The transfer mask 20 according to one embodiment of the present invention shown in FIG. 2 is provided with a film 2 having a transfer pattern (a film pattern, hereinafter sometimes referred to as a pattern) 2a on a substrate 1. In this transfer mask 20, the film 2 contains a material containing chromium. In addition, the film 2 is characterized in that it includes an upper region on the side opposite to the substrate 1 side and a region other than the upper region, and the crystal size of the upper region is larger than the crystal size of the regions other than the upper region. The composition of the substrate 1 and the film 2 in this case is the same as the case of the above-mentioned mask base 10.

Such a photomask 20 for transfer of the present invention can be manufactured by using the above-mentioned photomask substrate 10 of the present invention, for example. The details of the manufacturing method of the transfer mask will be described below.

As described above, the mask base 10 according to one embodiment of the present invention shown in FIG. 1 is provided with the pattern forming film 2 on the substrate 1. The film 2 contains a material containing chromium. In addition, the thin film 2 has a structure including an upper region on the side opposite to the substrate 1 side and a region other than the upper region, and the crystal size of the upper region is larger than the crystal size of the regions other than the upper region. By setting the photomask substrate 10 to such a structure, the etching rate of the entire patterning film 2 for wet etching can be increased, and the verticality of the pattern sidewalls when the film 2 is patterned by wet etching can be improved. As a result, the transfer mask 20 made from the mask substrate 10 is a transfer mask in which a transfer pattern with improved verticality of the pattern sidewalls and a good cross-sectional shape is accurately formed. In addition, in the transfer mask 20, the film 2 having the transfer pattern 2a also includes a material containing chromium. In addition, the thin film 2 has a structure including an upper region on the side opposite to the substrate 1 side and a region other than the upper region, and the crystal size of the upper region is larger than the crystal size of the regions other than the upper region.

As described above, in the photomask substrate 10, it is preferable that the upper region of the film 2 and the regions other than the upper region are both polycrystalline structures. In addition, in the transfer mask 20 made from the mask substrate 10, it is also preferable that the upper region of the film 2 and the regions other than the upper region are all polycrystalline structures. Thereby, the line edge roughness of the side wall of the formed transfer pattern is reduced.

Also, as in the case of the above-mentioned photomask base 10, in the transfer photomask 20, it is also preferable to obtain the respective crystal surfaces of the upper region of the film 2 and the regions other than the upper region obtained by the electron diffraction method. The intervals are all 0.2 nm or more.

Also, as in the case of the above-mentioned photomask base 10, in the transfer photomask 20, it is also preferable that both the upper region of the film 2 and the regions other than the upper region have a columnar structure. Thereby, the etching rate of the thin film 2 in the photomask substrate 10 for wet etching is increased, and the verticality of the sidewall of the transfer pattern formed in the transfer photomask 20 is improved.

Also, as in the case of the above-mentioned photomask base 10, in the transfer photomask 20, it is also preferable that the above-mentioned thin film 2 is a composition gradient film in which the content of chromium changes in the thickness direction. Thereby, the sidewall shape of the formed transfer pattern does not produce a step difference.

In addition, as in the case of the above-mentioned photomask base 10, in the transfer photomask 20, the above-mentioned thin film 2 can be, for example, a light-shielding film containing a chromium-based material having an optical density of 3 or more with respect to exposure light. The light-shielding film in this case is the same as the case of the above-mentioned mask substrate 10.

Next, another embodiment of the above-mentioned transfer mask 20 will be described. In this other embodiment, the region other than the upper region of the above-mentioned film 2 further includes two regions, the lower region and the middle region from the substrate side. That is, in the transfer mask 20 of another embodiment, the thin film 2 containing a material containing chromium includes three regions, namely, a lower region, a middle region, and an upper region from the substrate 1 side. In this case, it is assumed that the crystal size of the thin film 2 becomes larger in the order of the middle region, the lower region, and the upper region.

The transfer photomask 20 of this other embodiment can be manufactured using, for example, the photomask substrate 10 of the other embodiment described above. As described above, in the mask substrate of another embodiment, by increasing the crystal size of the film 2 in the order of the middle region, the lower region, and the upper region, the etching rate of each region in the film 2 for wet etching can be increased It becomes faster in the order of the middle area, the lower area, and the upper area. As a result, the overall etching rate of the film 2 of the photomask substrate 10 is increased, and the verticality of the pattern sidewalls when the film 2 is patterned by wet etching can be improved. As a result, the transfer mask 20 manufactured from the mask base 10 of another embodiment is a transfer mask in which a transfer pattern with improved verticality of the pattern sidewalls and a good cross-sectional shape is accurately formed.

The photomask for transfer of the present invention is preferably manufactured using the above-mentioned photomask substrate of the present invention. Next, a method of manufacturing a photomask 20 for transfer using the photomask substrate 10 of the present invention shown in FIG. 1 will be described.

The manufacturing method of the transfer photomask 20 using the photomask substrate 10 has, for example, the following steps: drawing a desired pattern on the resist film formed on the photomask substrate 10; applying the resist film after the pattern drawing Developing to form a resist pattern; using the above resist pattern as a photomask, patterning the patterning film 2 of the photomask base 10 using wet etching; and stripping and removing the remaining resist pattern.

Fig. 3 is a cross-sectional view showing the manufacturing steps of a photomask for transfer using the photomask substrate of the present invention. FIG. 3(a) shows a state in which a resist film 3 is formed on the pattern forming film 2 of the photomask base 10 of FIG. 1. FIG. Furthermore, as the resist material, either positive type resist material or negative type resist material can be used. However, in the production of transfer masks used in the manufacture of semiconductor devices, positive type resist materials are usually used as should.

Next, FIG. 3(b) shows the step of performing the required pattern drawing on the resist film 3 formed on the photomask substrate 10. The pattern drawing can be performed using a laser plotting device, an electron beam plotting device, and the like. Next, FIG. 3(c) shows a step of developing the above-mentioned resist film 3 to form a resist pattern 3a after the desired pattern is drawn.

Next, FIG. 3(d) shows an etching step in which the patterning film 2 of the photomask base 10 is patterned by wet etching using the above-mentioned resist pattern 3a as a photomask. Through this etching step, a required transfer pattern (film pattern) 2a is formed on the film 2.

As an etching solution used in wet etching, an aqueous solution of perchloric acid added to cerium ammonium nitrate is generally used. The wet etching conditions such as the concentration, temperature, and processing time of the etching solution can be appropriately set according to the etching characteristics of the film 2 and the like.

FIG. 3(e) shows the transfer mask 20 obtained by peeling and removing the remaining resist pattern 3a.

In this way, the transfer mask 20 provided with the film 2 having the transfer pattern 2a on the substrate 1 is produced. According to the present invention, a transfer mask 20 with a transfer pattern having an improved verticality of the pattern sidewall and a good cross-sectional shape is formed accurately.

In each of the above embodiments, the transfer mask and the manufacturing method thereof having the film 2 having the transfer pattern (film pattern) 2a on the substrate 1 have been described, but the present invention is not limited to this embodiment. As in the case of the above-mentioned photomask base, the transfer photomask of the present invention also includes, for example, the following aspect, that is, between the translucent substrate 1 and the thin film pattern (light-shielding pattern) 2a, there is a light for exposing A semi-transmissive pattern (pattern of a semi-transparent film) that transmits a specific transmittance (for example, a transmittance above 1% and below 40%). The semi-transmissive pattern can also be a phase shift pattern (pattern of a phase shift film) that further has the following function, that is, the light that passes through the exposure inside the pattern is equivalent to the pattern when passing through the air (translucent) A specific phase difference (for example, a phase difference of 150 degrees or more and 210 degrees or less) occurs between the exposure light at the distance of the thickness of the light film. In the case of these structures, it is preferable to use a laminated structure of a semi-transmissive pattern (or a phase shift pattern) and a light-shielding pattern so that the optical density of the above-mentioned exposed light is 3 or more.

On the other hand, the transfer mask of the present invention is not limited to the use of the transfer mask used in the manufacture of semiconductor devices. For example, the transfer mask of the present invention can also be applied to manufacture FPD (Flat Panel Display) represented by LCD (Liquid Crystal Display), OLED (Organic Light Emitting Diode, Organic Light Emitting Diode), etc. Flat-panel displays) and other display devices used for transfer masks.

[Method of Manufacturing Semiconductor Device] In addition, the present invention also provides a method of manufacturing a semiconductor device. The manufacturing method of the semiconductor device of the present invention is characterized by including the step of exposing and transferring the transfer pattern to the resist film on the semiconductor substrate using the above-mentioned transfer mask 20.

The above-mentioned transfer mask 20 of the present invention is formed with a transfer pattern in which the verticality of the pattern side wall is improved. As a result, for example, when the transfer mask 20 is set on the mask stage of an exposure device that uses light of i-ray as the light for exposure, and the transfer pattern is exposed and transferred to the resist film on the semiconductor substrate , It can also transfer the pattern to the resist film on the semiconductor substrate with the precision that fully meets the design specifications. According to the present invention, a semiconductor device in which a high-definition transfer pattern is formed using the transfer mask of the present invention can be manufactured.

As explained in detail above, according to the present invention, a photomask substrate can be provided, which can increase the etching rate of the patterning film as a whole for wet etching, thereby increasing the verticality of the pattern sidewalls when the film is patterned by wet etching. sex. Furthermore, according to the present invention, it is possible to provide a photomask for transfer with improved verticality of the side wall of the film pattern. Furthermore, according to the present invention, it is possible to provide a method for manufacturing a semiconductor device, which can use the transfer mask of the present invention to form a good transfer pattern. [Example]

Hereinafter, the embodiments of the present invention will be explained in more detail with examples. (Example 1) The photomask base 10 of Example 1 has a structure provided with a thin film (light-shielding film) 2 for pattern formation on a translucent substrate 1. The photomask substrate 10 is manufactured in the following manner.

Prepare 3 translucent substrates 1 (about 152 mm×152 mm×thickness about 6.35 mm) containing synthetic quartz glass. The main surface and the end surface of the translucent substrate 1 are polished to a specific surface roughness (for example, the main surface is 0.2 nm or less in terms of root mean square roughness Rq).

Next, on the three light-transmitting substrates 1 described above, the light-shielding film 2 including the three regions of the lower region, the middle region, and the upper region are respectively formed in the following steps. First, in the sputtering chamber, a continuous sputtering device in which a plurality of chromium (Cr) targets are installed along the conveying direction of the translucent substrate 1 is prepared. In the sputtering chamber, the translucent substrate 1 is transported on one side, and _{the mixed gas of argon (Ar) and nitrogen (N 2} ) on the other side (flow ratio Ar:N ₂ =22:4, pressure =3.0×10 ^-4 Pa ) In a gas atmosphere, a voltage is applied to the Cr target under constant current control with a current value of 0.8 A, and reactive sputtering (DC (direct current, direct current) sputtering) is performed, thereby forming the above-mentioned translucent substrate 1 The lower area of the light-shielding film 2.

Then, in the sputtering chamber, the translucent substrate 1 for film formation is transported to the lower area, _{and the mixed gas of argon (Ar), methane (CH 4} ) and helium (He) (flow ratio Ar:CH) ₄ :He=10:1:20, pressure=3.0×10 ^-4 Pa), apply voltage to the Cr target under constant current control with a current value of 3.6 A, and perform reactive sputtering (DC sputtering) , Thereby forming a middle area in contact with the lower area of the light-shielding film 2.

Then, in the sputtering chamber, the transparent substrate 1 formed to the middle area is transported on one side, and the mixed gas of argon (Ar) and nitric oxide (NO) (flow ratio Ar:NO=100:7, pressure =3.0×10 ^-4 Pa) in a gas atmosphere, a voltage is applied to the Cr target under constant current control with a current value of 0 A, and reactive sputtering (DC sputtering) is performed, thereby being in contact with the middle area of the light-shielding film 2 Grounding forms the upper area. According to the above steps, the photomask base 10 of Example 1 provided with the light-shielding film 2 including the three regions of the lower region, the middle region, and the upper region on the translucent substrate 1 was fabricated.

Furthermore, the optical density of the light-shielding film 2 of the embodiment 1 is 3.0 or more under the light of the wavelength of i-ray (365 nm), for example.

Next, X-ray Photoelectron Spectroscopy (XPS) was used to analyze the first light-shielding film of the mask substrate 10 of Example 1. As a result, the film thickness of the light-shielding film 2 is 100 nm, and the film thickness and composition of each region: the lower region (the film thickness is about 9 nm, the composition Cr:C:O:N=76atom%:2atom%:2atom %: 20 atomic %), the middle region (the film thickness is about 54 nm, the composition Cr:C:O:N=85 atomic%: 4 atomic%: 1 atomic%: 10 atomic%), the upper region (the film thickness is about 37 nm , Composition Cr:O:N=55 at%:28 at%:17 at%).

Then, on the second sheet of the light-shielding film 2 of the mask substrate 10 of Example 1, the cross-sectional TEM (Transmission Electron Microscope: Transmission Electron Microscope) image was observed, and the crystallinity observation by the electron diffraction method was performed. 4 is the electron beam diffraction image of the upper region of the light-shielding film 2 in the mask substrate 10 of Embodiment 1. FIG. FIG. 5 is an electron beam diffraction image of the middle region of the light-shielding film 2 in the mask substrate 10 of Embodiment 1. FIG. In addition, FIG. 6 is the electron beam diffraction image of the lower region of the light shielding film 2 in the mask substrate 10 of the first embodiment. In addition, FIG. 7 is a cross-sectional TEM image of the light-shielding film 2 in the mask substrate 10 of Example 1.

In the electron beam diffraction image of the upper region of the light-shielding film 2 shown in FIG. 4, the crystallinity is good, and the diffraction image is clear. In the upper region, due to the larger crystal grains, the diffraction pattern clearly appears. Among the three regions, the upper region has the largest crystal grains. In the electron beam diffraction image of the central region of the light-shielding film 2 shown in FIG. 5, the crystallinity is small, and the diffraction image is not clear. Among the three regions, the crystal grains in the middle region are the smallest. In the electron beam diffraction image of the lower region of the light-shielding film 2 shown in FIG. 6, compared with the middle region of FIG. 5, lattice points are visible, and it can be seen that the crystal grains are slightly larger than the middle region.

Based on the above, it is confirmed that the crystal size of the light-shielding film in the mask substrate 10 of the first embodiment increases in the order of the middle region, the lower region, and the upper region. Thereby, the wet etching rate of each area in the light-shielding film 2 can be increased in the order of the middle area, the lower area, and the upper area. As a result, the overall etching rate of the light-shielding film 2 of the mask substrate 10 of the first embodiment is increased, and the verticality of the pattern sidewalls when the light-shielding film 2 is patterned by wet etching can be improved.

In addition, based on the results of the electron beam diffraction image, it was confirmed that the lower, middle, and upper regions of the light shielding film 2 of Example 1 were all polycrystalline structures. In addition, based on the respective results of the electron beam diffraction image and the cross-sectional TEM image, it was confirmed that the lower, middle, and upper regions of the light-shielding film 2 of Example 1 all have a columnar structure.

The crystal plane spacing d in the lower region of the light-shielding film 2 of this embodiment 1 obtained by the electron diffraction method is 0.220 nm, the crystal plane spacing d in the middle region is 0.219 nm, and the crystal plane spacing d in the upper region is d = 0.216 nm. Both are above 0.2 nm.

Next, using the remaining third photomask substrate 10 of Example 1, the photomask 20 for transfer was manufactured according to the manufacturing steps shown in FIG. 3 described above. Firstly, a positive resist (TMHR-iP3500 manufactured by Tokyo Ohka Kogyo Co., Ltd.) is coated on the upper surface of the above-mentioned photomask substrate 10 by spin coating method, and a specific baking process is performed. Then, a resist film 3 with a thickness of 300 nm is formed (see FIG. 3(a)).

Next, using a laser plotter, draw a specific device pattern (a pattern corresponding to the transfer pattern to be formed on the light-shielding film 2) on the above-mentioned resist film 3, and then develop the resist film to form a resist pattern 3a (refer to Figure 3 (b), (c)).

Next, the light-shielding film 2 is wet-etched using the above-mentioned resist pattern 3a as a mask, and a light-shielding film pattern (transfer pattern) 2a is formed on the light-shielding film 2 (see FIG. 3(d)). As an etching solution for wet etching, an aqueous solution in which perchloric acid is added to cerium ammonium nitrate is used. Furthermore, when the light-shielding film 2 is subjected to wet etching, the etching rate of each region of the light-shielding film 2 is measured. As a result, the lower region was 1.7 nm/sec, the middle region was 1.5 nm/sec, and the upper region was 2.3 nm/sec. That is, it can be seen that the light-shielding film 2 of Example 1 has a structure in which the wet etching rate becomes faster in the order of the middle region, the lower region, and the upper region.

Finally, by removing the remaining resist pattern 3a, the transfer mask 20 of Example 1 equipped with a light-shielding film pattern 2a as a transfer pattern on the translucent substrate 1 is produced (see FIG. 3(e)) .

As described above, in the mask substrate of the first embodiment, by making the crystal size of the light-shielding film 2 larger in the order of the middle region, the lower region, and the upper region, the regions in the light-shielding film 2 can be more effective for wet etching. The etching rate becomes faster in the order of the middle area, the lower area, and the upper area. Thereby, the verticality of the pattern sidewalls when the light-shielding film 2 is patterned by wet etching can be improved. As a result, in the above-mentioned transfer mask 20 manufactured from the mask substrate of the first embodiment, a transfer pattern with improved verticality of the pattern sidewall and a good cross-sectional shape is formed.

Furthermore, the transfer mask 20 of Example 1 was set on the mask stage of the exposure device using the light of the i-ray as the exposure light, and the transfer mask 20 was irradiated and exposed from the translucent substrate 1 side. Light exposes and transfers the pattern to the resist film of the semiconductor device. Then, a specific treatment is performed on the resist film after exposure and transfer to form a resist pattern, and the resist pattern is observed by CD-SEM (Critical Dimension-Scanning Electron Microscope). As a result, it was confirmed that the resist pattern was formed with high CD (Critical Dimension) accuracy. Based on the foregoing, it can be said that the above-mentioned transfer photomask 20 manufactured from the photomask substrate 10 of the first embodiment can perform high-precision exposure and transfer of the resist film on the semiconductor device.

(Example 2) The mask substrate 10 of Example 2 was fabricated in the following manner. In the same manner as in Example 1, three translucent substrates 1 (size approximately 152 mm×152 mm×thickness approximately 6.35 mm) containing synthetic quartz glass were prepared. The main surface and end surface of the translucent substrate are polished to a specific surface roughness (for example, the main surface is 0.2 nm or less in terms of root mean square roughness Rq).

Next, on the three light-transmitting substrates 1 described above, the light-shielding film 2 including the three regions of the lower region, the middle region, and the upper region are respectively formed in the following steps. First, in the sputtering chamber, a continuous sputtering device in which a plurality of chromium (Cr) targets are installed along the conveying direction of the translucent substrate 1 is prepared. In the sputtering chamber, the translucent substrate 1 is transported on one side, and _{the mixed gas of argon (Ar) and nitrogen (N 2} ) on the other side (flow ratio Ar:N ₂ =9:4, pressure =3.0×10 ^-4 Pa In a gas atmosphere of ), a voltage is applied to the Cr target under constant current control with a current value of 1.6 A, and reactive sputtering (DC sputtering) is performed to form the lower region of the light-shielding film 2 on the translucent substrate 1.

Then, in the sputtering chamber, the translucent substrate 1 for film formation is transported to the lower area, and _{the mixed gas of argon (Ar) and methane (CH 4} ) (flow ratio Ar:CH ₄ =30:1, In a gas atmosphere of pressure=3.0×10 ^-4 Pa), a voltage is applied to the Cr target under constant current control with a current value of 2.5 A, and reactive sputtering (DC sputtering) is performed, thereby interacting with the lower area of the light-shielding film 2 Grounding to form the middle area.

Then, in the sputtering chamber, the transparent substrate 1 formed to the middle area is transported on one side, and the mixed gas of argon (Ar) and nitric oxide (NO) (flow ratio Ar:NO=100:4, pressure =3.0×10 ^-4 Pa) in a gas atmosphere, a voltage is applied to the Cr target under constant current control with a current value of 0 A, and reactive sputtering (DC sputtering) is performed, thereby being in contact with the middle area of the light-shielding film 2 Grounding forms the upper area. According to the above steps, the photomask base 10 of Example 2 provided with the light-shielding film 2 including the three regions of the lower region, the middle region and the upper region on the translucent substrate 1 was fabricated.

Furthermore, the optical density of the light-shielding film 2 of the embodiment 2 is 3.0 or more under the light of the wavelength of i-ray (365 nm), for example.

Next, X-ray photoelectron spectroscopy (XPS) was used to analyze the first light-shielding film 2 of the mask substrate 10 of Example 2. As a result, the film thickness of the light-shielding film 2 is 71 nm, and the film thickness and composition of each region: the lower region (the film thickness is about 21 nm, the composition Cr:C:N=72atom%:2atom%:26atom% ), the middle region (the film thickness is about 32 nm, the composition Cr:C:O:N=82 atomic%: 6 atomic%: 1 atomic%: 11 atomic%), the upper region (the film thickness is about 18 nm, the composition Cr:O :N=55 atomic %: 25 atomic %: 20 atomic %).

Then, observation of the cross-sectional TEM image of the light-shielding film 2 of the mask base 10 of Example 2 and the crystallinity observation by the electron diffraction method were performed on the second sheet. FIG. 8 shows the electron beam diffraction image of the upper region of the light-shielding film 2 in the mask substrate 10 of the second embodiment. 9 shows the electron beam diffraction image of the middle region of the light-shielding film 2 in the mask substrate 10 of the second embodiment. In addition, FIG. 10 shows the electron beam diffraction image of the lower region of the light-shielding film 2 in the mask substrate 10 of the second embodiment. In addition, FIG. 11 shows a cross-sectional TEM image of the light-shielding film in the mask substrate of Example 2.

In the electron beam diffraction image of the upper region of the light-shielding film 2 shown in FIG. 8, the crystallinity is good, and the diffraction image is clear. Due to the large crystal grains, the diffraction pattern appears clearly. Among the three regions, the upper region has the largest crystal grains. In the electron beam diffraction image of the central region of the light shielding film 2 shown in FIG. 9, the crystallinity is small, and the diffraction image is not clear. Among the three regions, the crystal grains in the middle region are the smallest. In the electron beam diffraction image of the lower region of the light-shielding film 2 shown in FIG. 10, compared with the middle region of FIG. 9, the lattice points are clearly visible, and it can be seen that the crystal grains are larger than the middle region.

Based on the above, it is confirmed that the crystal size of the light-shielding film 2 in the mask substrate 10 of the second embodiment increases in the order of the middle region, the lower region, and the upper region. Thereby, the wet etching rate of each area in the light-shielding film 2 can be increased in the order of the middle area, the lower area, and the upper area. As a result, the overall etching rate of the light-shielding film 2 of the mask substrate of the second embodiment is increased, and the verticality of the pattern sidewalls when the light-shielding film 2 is patterned by wet etching can be improved.

In addition, based on the results of the electron beam diffraction image, it was confirmed that the lower, middle, and upper regions of the light-shielding film 2 of Example 2 were all polycrystalline structures. Furthermore, based on the respective results of the electron beam diffraction image and the cross-sectional TEM image, it was confirmed that the lower, middle, and upper regions of the light-shielding film 2 of Example 2 all have a columnar structure.

In addition, the crystal plane spacing d in the lower region of the light-shielding film 2 of this embodiment 2 obtained by the electron diffraction method is 0.212 nm, the crystal plane spacing in the middle region d=0.220 nm, and the crystal plane spacing in the upper region d=0.248 nm, both are above 0.2 nm.

Next, using a third sheet of the mask base 10 of this embodiment 2, and following the manufacturing steps shown in FIG. 3 in the same manner as in the above-mentioned embodiment 1, a light-shielding film pattern 2a that becomes a transfer pattern is manufactured on a translucent substrate 1 The transfer mask 20. Furthermore, when the light-shielding film 2 is subjected to wet etching, the etching rate of each area of the light-shielding film 2 is measured. As a result, the lower region was 1.3 nm/sec, the middle region was 1.2 nm/sec, and the upper region was 1.8 nm/sec. That is, it can be seen that the light-shielding film of Example 2 has a structure in which the wet etching rate becomes faster in the order of the middle region, the lower region, and the upper region.

In the mask substrate 10 of the second embodiment, by making the crystal size of the light-shielding film 2 larger in the order of the middle region, the lower region, and the upper region, the etching rate of each region in the light-shielding film 2 for wet etching can be adjusted to The order of the middle area, lower area, and upper area becomes faster. Therefore, in the above-mentioned transfer mask 20 manufactured from the mask substrate 10 of the second embodiment, a transfer pattern with improved verticality of the pattern sidewall and a good cross-sectional shape is formed.

Furthermore, the transfer mask 20 of Example 2 was set on the mask stage of the exposure device using the light of the i-ray as the exposure light, and the transfer mask 20 was irradiated and exposed from the translucent substrate 1 side. Light exposes and transfers the pattern to the resist film of the semiconductor device. Then, a specific treatment is performed on the resist film after exposure and transfer to form a resist pattern, and the resist pattern is observed by CD-SEM. As a result, it was confirmed that the resist pattern was formed with high CD accuracy. Based on the above, it can be said that the above-mentioned transfer photomask 20 manufactured from the photomask substrate 10 of the second embodiment can perform high-precision exposure and transfer of the resist film on the semiconductor device.

(Example 3) The mask substrate of the embodiment was fabricated in the following manner. In the same manner as in Example 1, three translucent substrates 1 (size approximately 152 mm×152 mm×thickness approximately 6.35 mm) containing synthetic quartz glass were prepared. The main surface and the end surface of the translucent substrate 1 are polished to a specific surface roughness (for example, the main surface is 0.2 nm or less in terms of Rq).

Next, on the three light-transmitting substrates 1 described above, the light-shielding film 2 including the three regions of the lower region, the middle region, and the upper region are respectively formed in the following steps. First, in the sputtering chamber, a continuous sputtering device in which a plurality of chromium (Cr) targets are installed along the conveying direction of the translucent substrate 1 is prepared. In the sputtering chamber, the translucent substrate 1 is transported on one side, and _{the mixed gas of argon (Ar) and nitrogen (N 2} ) on the other side (flow ratio Ar:N ₂ =4:1, pressure =4.0×10 ^-4 Pa ) In a gas atmosphere, a voltage is applied to the Cr target under constant voltage control with a power value of 0.5 W, and reactive sputtering (DC sputtering) is performed, thereby forming the lower region of the light-shielding film 2 on the translucent substrate 1 .

Then, in the sputtering chamber, the translucent substrate 1 for film formation is transported to the lower area, and _{the mixed gas of argon (Ar) and methane (CH 4} ) (flow ratio Ar:CH ₄ =17:1, Pressure = 4.0×10 ^-4 Pa) in a gas atmosphere, voltage is applied to the Cr target under constant current control with a current value of 5 A, and reactive sputtering (DC sputtering) is performed, thereby interacting with the lower area of the light-shielding film 2 Grounding to form the middle area.

Then, in the sputtering chamber, the transparent substrate 1 formed to the middle area is transported on one side, and the mixed gas of argon (Ar) and nitric oxide (NO) (flow ratio Ar:NO=11:2, pressure =4.0×10 ^-4 Pa) in a gas atmosphere, voltage is applied to the Cr target under constant current control, and reactive sputtering (DC sputtering) is performed to form an upper area in contact with the middle area of the light-shielding film 2 . According to the above steps, the photomask base 10 of Example 3 provided with the light-shielding film 2 including the three regions of the lower region, the middle region and the upper region on the above-mentioned translucent substrate was fabricated.

Furthermore, the optical density of the light-shielding film 2 of Example 3 is 3.0 or more under the light of the wavelength of i-ray (365 nm), for example.

Next, X-ray photoelectron spectroscopy (XPS) was used to analyze the first light-shielding film of the mask base 10 of Example 3. As a result, the film thickness of the light-shielding film 2 is 100 nm, and the film thickness and composition of each region: the lower region (the film thickness is about 12 nm, the composition Cr:C:N=78atom%:10atom%:12atom% ), the middle region (the film thickness is about 58 nm, the composition Cr:C:O:N=65 atomic%: 10 atomic%: 5 atomic%: 20 atomic%), the upper region (the film thickness is about 30 nm, the composition Cr:C :O:N=50 atomic %: 5 atomic %: 20 atomic %: 25 atomic %).

Then, observation of the cross-sectional TEM image of the light-shielding film of the mask base 10 of the present Example 3 and the crystallinity observation by the electron diffraction method were performed on the second sheet. 12 shows the electron beam diffraction image of the upper region of the light-shielding film 2 in the mask substrate 10 of the third embodiment. FIG. 13 shows the electron beam diffraction image of the middle region of the light-shielding film 2 in the mask substrate 10 of the third embodiment. 14 shows the electron beam diffraction image of the lower region of the light shielding film 2 in the mask substrate 10 of the third embodiment. In addition, FIG. 15 shows a cross-sectional TEM (transmission electron microscope) image of the light-shielding film 2 in the mask substrate 10 of Example 3.

In the electron beam diffraction image of the upper region of the light-shielding film 2 shown in FIG. 12, the crystallinity is good, and the diffraction image is clear. Due to the large crystal grains, the diffraction pattern appears clearly. Among the three regions, the upper region has the largest crystal grains. In the electron beam diffraction image of the middle region of the light-shielding film 2 shown in FIG. 13, compared with the lower region of FIG. 14, the lattice points can be clearly seen, and it can be seen that the crystal grains are slightly larger than the lower region. In the electron beam diffraction image of the lower region of the light-shielding film 2 shown in FIG. 14, the crystallinity is small, and the diffraction image is not clear. There is also the possibility that the crystal grains in the lower region are the smallest among the 3 regions, but it is considered that the difference is small from the middle region in FIG. 13.

Based on the above content, it is confirmed that regarding the crystal size of the light-shielding film 2 in the mask substrate 10 of the third embodiment, the crystal size of the upper region is larger than the crystal size of the other middle and lower regions. Thereby, regarding the wet etching rate of each area in the light-shielding film 2, the upper area can be made faster than the middle area and the lower area. As a result, the overall etching rate of the light-shielding film 2 of the mask substrate of the third embodiment can be increased, and the verticality of the pattern sidewalls when the light-shielding film 2 is patterned by wet etching can be improved.

In addition, based on the results of the electron beam diffraction image, it was confirmed that the lower, middle, and upper regions of the light-shielding film 2 of Example 3 were all polycrystalline structures. Furthermore, based on the respective results of the electron beam diffraction image and the cross-sectional TEM image, it was confirmed that the lower, middle, and upper regions of the light-shielding film 2 of Example 3 all have a columnar structure.

In addition, the crystal plane spacing d in the lower region of the light-shielding film 2 of the third embodiment obtained by the electron diffraction method d=0.233 nm, the crystal plane spacing d in the middle region d=0.223 nm, and the crystal plane spacing d in the upper region d=0.208 nm, both are above 0.2 nm.

Next, using a third sheet of the mask base 10 of this embodiment 3, in the same manner as in the above-mentioned embodiment 1, according to the manufacturing steps shown in FIG. The transfer mask 20. Furthermore, when the light-shielding film 2 is wet-etched, the etching rate of each area of the light-shielding film 2 is measured. As a result, the lower region was 1.4 nm/sec, the middle region was 1.7 nm/sec, and the upper region was 2.3 nm/sec. That is, it can be seen that the light-shielding film of Example 3 has a structure in which the wet etching rate becomes faster in the order of the lower region, the middle region, and the upper region.

In the mask substrate 10 of the third embodiment, by making the crystal size of the upper region of the light-shielding film 2 larger than the crystal size of the other middle and lower regions, the upper region of each region in the light-shielding film The etching rate for wet etching is faster than the middle area and the lower area. Therefore, in the above-mentioned transfer mask 20 manufactured from the mask substrate 10 of the third embodiment, a transfer pattern with improved verticality of the pattern sidewall and a good cross-sectional shape is formed.

Furthermore, the transfer mask 20 of Example 3 was set on the mask stage of the exposure device using the light of the i-ray as the exposure light, and the transfer mask 20 was irradiated and exposed from the translucent substrate 1 side. Light exposes and transfers the pattern to the resist film of the semiconductor device. Then, a specific treatment is performed on the resist film after exposure and transfer to form a resist pattern, and the resist pattern is observed by CD-SEM. As a result, it was confirmed that the resist pattern was formed with high CD accuracy. Based on the foregoing, it can be said that the above-mentioned transfer photomask 20 manufactured from the photomask substrate 10 of the third embodiment can perform high-precision exposure and transfer of the resist film on the semiconductor device.

(Comparative example 1) The photomask substrate of Comparative Example 1 was produced in the following manner. In the same manner as in Example 1, three translucent substrates (size approximately 152 mm × 152 mm × thickness approximately 6.35 mm) containing synthetic quartz glass were prepared. The main surface and end surface of the translucent substrate are polished to a specific surface roughness (for example, the main surface is 0.2 nm or less in terms of Rq).

Next, on the above three light-transmitting substrates, a light-shielding film including three regions, a lower region, a middle region, and an upper region, is formed in the following steps. First, a rotating table on which the translucent substrate 1 is placed and a single-chip sputtering device equipped with a chromium (Cr) target are prepared in the sputtering chamber. The above-mentioned translucent substrate is set on the rotating table in the sputtering chamber, _{and the mixed gas of argon (Ar), nitrogen (N 2} ), carbon dioxide (CO ₂ ) and helium (He) (flow ratio Ar:N ₂ :CO ₂ :He=4:3:6:8, pressure=1.0×10 ^-4 Pa) in a gas atmosphere, set the DC power applied to the Cr target to 2.0 kW (constant current control) to perform reactive sputtering Plating (DC sputtering), thereby forming the lower region of the light-shielding film on the translucent substrate.

Second, stop applying DC power to the Cr target, and change the sputtering gas atmosphere in the sputtering chamber to a mixed gas of argon (Ar), nitric oxide (NO) and helium (He) (flow ratio Ar:NO:He) =1:1:2, pressure=1.0×10 ^-4 Pa), start to apply DC power (power: 2.0 kW, constant current control) to the Cr target, perform reactive sputtering (DC sputtering), and The above-mentioned lower regions are connected to form a middle region.

Then, the application of DC power to the Cr target was stopped, and the sputtering chamber was changed to a _{mixed gas of argon (Ar), nitrogen (N 2} ), carbon dioxide (CO ₂ ) and helium (He) (flow ratio Ar:N ₂ : After CO ₂ :He=4:3:8:8, pressure=1.0×10 ^-4 Pa), start to apply DC power (power: 2.0 kW, constant current control) to the Cr target to perform reactive sputtering (DC sputtering), thereby forming the upper region in contact with the above-mentioned middle region. The mask base of Comparative Example 1 provided with a light-shielding film including three regions of a lower region, a middle region, and an upper region on the above-mentioned translucent substrate was fabricated in the above steps.

Furthermore, the optical density of the light-shielding film of Comparative Example 1 is 3.0 or more at the wavelength of i-ray (365 nm), for example.

Next, X-ray photoelectron spectroscopy (XPS) was used to analyze the first light-shielding film of the mask substrate of Comparative Example 1. As a result, the film thickness of the light-shielding film is 86 nm, and the film thickness and composition of each region: the lower region (the film thickness is about 41 nm, the composition Cr:C:O:N=56atom%:11atom%:22atom %: 11 atomic %), the middle region (the film thickness is about 31 nm, the composition Cr:O:N=85 atomic%: 7 atomic%: 8 atomic%), the upper region (the film thickness is about 14 nm, the composition Cr:C: O:N=47 atomic %: 9 atomic %: 34 atomic %: 10 atomic %).

Then, the second sheet of the light-shielding film of the mask base of this comparative example 1 was observed for the cross-sectional TEM image and the crystallinity observation by the electron diffraction method. FIG. 16 shows the electron beam diffraction image of the upper region of the light-shielding film in the mask substrate of Comparative Example 1. FIG. FIG. 17 shows the electron beam diffraction image of the middle region of the light-shielding film in the mask substrate of Comparative Example 1. FIG. In addition, FIG. 18 shows the electron beam diffraction image of the lower region of the light-shielding film in the mask base of Comparative Example 1. In addition, FIG. 19 shows a cross-sectional TEM image of the light-shielding film in the mask base of Comparative Example 1.

In the electron beam diffraction image of the upper region of the light-shielding film shown in FIG. 16, no diffraction image derived from the crystalline structure is seen, and it can be seen that the upper region has an amorphous structure. In the electron beam diffraction image in the middle region of the light-shielding film shown in Fig. 17, the crystallinity is small and the diffraction image is not clear. In the electron beam diffraction image of the lower region of the light-shielding film shown in FIG. 18, compared with the middle region of FIG. 17, the lattice points can be clearly seen, and it can be seen that the crystal grains are slightly larger than the middle region.

In addition, based on the results of the electron beam diffraction image, it was confirmed that the upper region of the light shielding film of this Comparative Example 1 had an amorphous structure, but the lower region and the middle region were both polycrystalline structures. In addition, based on the results of the electron beam diffraction image and the cross-sectional TEM image, it was confirmed that the light-shielding film of Comparative Example 1 did not have a columnar structure in any region.

In addition, the crystal plane spacing d in the lower region of the light-shielding film of this comparative example 1 obtained by the electron diffraction method was d=0.217 nm, and the crystal plane spacing d in the middle region was d=0.218 nm.

Next, using the third photomask base of this comparative example 1, and following the manufacturing steps shown in Figure 3 in the same manner as in the above-mentioned Example 1, it was fabricated on a translucent substrate with a light-shielding film pattern as a transfer pattern. Use a photomask. Furthermore, when the light-shielding film is wet-etched, the etching rate of each area of the light-shielding film is measured. As a result, the lower region was 1.0 nm/sec, the middle region was 0.6 nm/sec, and the upper region was 0.9 nm/sec. That is, it can be seen that the light-shielding film of Comparative Example 1 has a structure in which the wet etching rate becomes faster in the order of the middle region, the upper region, and the lower region. However, it can be seen that the wet etching rate of all regions is significantly slower than that of the light-shielding film 2 of the above-mentioned Examples 1 to 3.

The mask substrate of Comparative Example 1, especially the upper region of the light-shielding film has an amorphous structure. Therefore, compared with the upper region of the light-shielding film 2 of Examples 1 to 3, the etching rate for wet etching is significantly slower. Therefore, using the above-mentioned transfer mask manufactured from the mask substrate of this comparative example 1, the verticality of the pattern sidewalls cannot be improved, and it is difficult to form a transfer pattern with a good cross-sectional shape.

Furthermore, the transfer photomask of Comparative Example 1 was set on the photomask stage of the exposure device using the light of i-ray as the exposure light, and the exposure light was irradiated from the translucent substrate side of the transfer photomask. The pattern is exposed and transferred to the resist film of the semiconductor device. Then, a specific treatment is performed on the resist film after exposure and transfer to form a resist pattern, and the resist pattern is observed by CD-SEM. As a result, it was confirmed that the CD accuracy of the resist pattern was low. According to this result, it can be said that when the above-mentioned transfer photomask made from the photomask substrate of this comparative example 1 is set on the photomask stage of the exposure device, and the resist film transferred onto the semiconductor device is exposed, it is difficult to finally A circuit pattern is formed on a semiconductor device with high precision.

1: substrate 2: Film for pattern formation 2a: Film pattern (transfer pattern, shading film pattern) 3: resist film 3a: resist pattern 10: Mask base 20: Mask for transfer

Fig. 1 is a cross-sectional view showing an embodiment of the photomask substrate of the present invention. Fig. 2 is a cross-sectional view showing an embodiment of the transfer mask of the present invention. 3(a) to (e) are cross-sectional views showing the manufacturing steps of a photomask for transfer using the photomask substrate of the present invention. 4 shows the electron beam diffraction image of the upper region of the light-shielding film in the mask substrate of Example 1 of the present invention. Fig. 5 shows the electron beam diffraction image of the middle region of the light-shielding film in the mask substrate of Example 1 of the present invention. Fig. 6 shows the electron beam diffraction image of the lower region of the light-shielding film in the mask substrate of Example 1 of the present invention. FIG. 7 shows a cross-sectional TEM image of the light-shielding film in the mask substrate of Example 1 of the present invention. Fig. 8 shows the electron beam diffraction image of the upper region of the light-shielding film in the mask substrate of Example 2 of the present invention. 9 shows the electron beam diffraction image of the middle region of the light-shielding film in the mask substrate of Example 2 of the present invention. FIG. 10 shows the electron beam diffraction image of the lower region of the light-shielding film in the mask substrate of Example 2 of the present invention. FIG. 11 shows a cross-sectional TEM image of the light-shielding film in the mask substrate of Example 2 of the present invention. FIG. 12 shows the electron beam diffraction image of the upper region of the light-shielding film in the mask substrate of Example 3 of the present invention. FIG. 13 shows the electron beam diffraction image of the middle region of the light-shielding film in the mask substrate of Example 3 of the present invention. Fig. 14 shows the electron beam diffraction image of the area under the light-shielding film in the mask substrate of Example 3 of the present invention. FIG. 15 shows a cross-sectional TEM image of the light-shielding film in the mask substrate of Example 3 of the present invention. 16 is a diagram showing the electron beam diffraction image of the upper region of the light-shielding film in the mask substrate of the comparative example. FIG. 17 shows the electron beam diffraction image of the middle region of the light-shielding film in the mask substrate of the comparative example. FIG. 18 shows the electron beam diffraction image of the area under the light-shielding film in the mask substrate of the comparative example. Fig. 19 shows a cross-sectional TEM image of the light-shielding film in the mask substrate of the comparative example.

1: substrate

2: Film for pattern formation

10: Mask base

Claims (15)

A photomask base, characterized in that it is provided with a film for pattern formation on a substrate, and The above-mentioned film contains chromium-containing materials, The above-mentioned film includes an upper region on the side opposite to the substrate side and a region other than the upper region, The crystal size of the upper region is larger than the crystal size of regions other than the upper region. Such as the photomask substrate of claim 1, wherein the upper region of the film and the regions other than the upper region are all polycrystalline structures. Such as the photomask substrate of claim 1 or 2, wherein the distance between the crystal planes of the upper region of the film and the region other than the upper region obtained by the electron diffraction method is 0.2 nm or more. The mask substrate of claim 1 or 2, wherein the upper region of the film and the region other than the upper region have a columnar structure. Such as the mask base of claim 1 or 2, wherein the area except the upper area of the above-mentioned film includes two areas, the lower area and the middle area from the side of the substrate, The crystal size of the above-mentioned film increases in the order of the middle region, the lower region, and the upper region. The photomask substrate of claim 1 or 2, wherein the above-mentioned thin film is a composition gradient film in which the content of the above-mentioned chromium varies in the thickness direction. The photomask substrate of claim 1 or 2, wherein the above-mentioned film is a light-shielding film having an optical density of 3 or more to exposed light. A photomask for transfer, characterized in that it is provided with a film with a transfer pattern on a substrate, and The above-mentioned film contains chromium-containing materials, The above-mentioned film includes an upper region on the side opposite to the substrate side and a region other than the upper region, The crystal size of the upper region is larger than the crystal size of regions other than the upper region. Such as the transfer mask of claim 8, wherein the upper region of the film and the region other than the upper region are all polycrystalline structures. The transfer mask of claim 8 or 9, wherein the distance between the crystal planes of the upper region of the film and the region other than the upper region obtained by the electronic diffraction method is 0.2 nm or more. The transfer mask of claim 8 or 9, wherein the upper region of the film and the region other than the upper region have a columnar structure. Such as the transfer mask of claim 8 or 9, wherein the area except the upper area of the above-mentioned film includes two areas, the lower area and the middle area from the side of the substrate, The crystal size of the above-mentioned film increases in the order of the middle region, the lower region, and the upper region. The transfer mask of claim 8 or 9, wherein the thin film is a composition gradient film in which the content of chromium changes in the thickness direction. The transfer mask of claim 8 or 9, wherein the above-mentioned film is a light-shielding film having an optical density of 3 or more with respect to exposure light. A method for manufacturing a semiconductor device is characterized by comprising the steps of exposing and transferring a transfer pattern to a resist film on a semiconductor substrate using the transfer mask as claimed in any one of claims 8 to 14.

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