JP2024106698A - Phase shift mask blanks, phase shift masks, and manufacturing methods - Google Patents

Abstract

To maintain chemical resistance, shortening of etching time and verticality of a cross-sectional shape, and suppress formation of an eaves.SOLUTION: A phase shift mask blank has a mask layer becoming a phase shift mask, has a phase shift layer stacked on a transparent substrate and a light-shielding layer which is stacked on the phase shift layer and contains chromium. The phase shift layer contains carbon, oxygen, nitrogen, molybdenum and silicon. An average value in a film thickness direction of a concentration ratio Si/Mo of silicon to molybdenum is smaller than 2.5. The phase shift layer has a surface layer which is on a surface side separated from the transparent substrate in the film thickness direction and has nitrogen concentration of 45 atm% or more, an intermediate layer which is closer to the transparent substrate than the surface layer in the film thickness direction and has lower nitrogen concentration than that of the surface layer, and an etching time shortening layer which is closer to the transparent substrate than the intermediate layer in the film thickness direction and has lower nitrogen concentration than that of the surface layer, and an eaves is not formed at an interface between the light-shielding layer and the phase shift layer by etching.SELECTED DRAWING: Figure 8

Description

The present invention relates to phase shift mask blanks, phase shift masks, and manufacturing methods.

2. Description of the Related Art In the manufacture of flat panel displays (FPDs) such as liquid crystal displays and organic EL displays, or in the manufacture of semiconductor devices, a photomask is used in a photoresist process (see Patent Document 1).
In this case, the photomask may be a mask blank having a quartz substrate and a mask layer made of a chromium compound.

In recent years, the trend toward higher resolution has progressed significantly, and photomasks have also become finer. This has led to an increased need for edge-emphasizing phase shift masks in addition to conventional masks using light-shielding films.
Conventionally, a phase shift mask may be formed by forming a phase shift layer of a silicide film as a mask layer on a quartz substrate, and forming a light-shielding layer (binary layer) of a metal film such as a chromium film on top of that (Patent Document 2).

When forming a phase shift mask with a light-shielding layer made of chromium and a phase shift layer made of metal silicide, wet etching with a specific etching solution (etchant) is used to form the desired pattern. In addition, a cleaning solution such as an alkali is used for cleaning.

JP 2019-090911 A JP 2021-148826 A

Here, the tolerance range of the optical characteristics of each layer in the photomask is extremely narrow. This reduces the degree of freedom in the optical density and film thickness of each layer. Furthermore, in order to accommodate narrower widths, stricter cross-sectional perpendicularity is required.
In addition, since even slight changes in thickness are undesirable in each layer of the mask layer, high chemical resistance against etching solutions or cleaning solutions is also required. However, layers with high chemical resistance take longer to etch, which can have adverse effects on exposed areas other than the target to be processed. For example, surface roughness on the glass substrate surface, unexpected changes in thickness, and deterioration of the cross-sectional shape due to poor etching can occur.
For this reason, there is also a demand for shortening the etching time.

In phase shift mask blanks for FPDs, when a silicide film containing molybdenum and silicon is used as the phase shift film, there is an issue that the wet etching time of the phase shift film is long. Normally, a solution containing hydrofluoric acid is used as the wet etching solution for the silicide film. This causes a problem that the quartz substrate is etched during the wet etching of the silicide film, changing the phase shift characteristics of the silicide film. Therefore, it is desirable to keep the wet etching time as short as possible.

Furthermore, there is a trade-off between shortening the wet etching time and chemical resistance, and using a phase shift film with a short wet etching time means that the chemical resistance to alkaline solutions will deteriorate. Since alkaline solutions are used in the cleaning process when making masks, there is an issue that poor chemical resistance will cause the phase shift mask characteristics to change during the cleaning process.

In particular, if the etching rate is increased to improve chemical resistance on the surface of the phase shift layer and to shorten the etching time in the area close to the glass substrate in order to achieve both chemical resistance and a shorter etching time, the silicide layer remains in the area away from the glass substrate, that is, near the boundary with the chromium-containing light-shielding layer, forming an overhang. This hinders the perpendicularity of the cross-sectional shape.

The present invention has been made in consideration of the above circumstances, and aims to provide phase shift mask blanks and phase shift masks having a phase shift layer that can achieve both chemical resistance and shortened etching time, while maintaining the verticality of the cross-sectional shape and suppressing the formation of eaves.

(1) A phase shift mask blank according to one aspect of the present invention,
A phase shift mask blank having a mask layer that serves as a phase shift mask,
a phase shift layer made of a metal silicide laminated on a transparent substrate;
a light-shielding layer containing chromium laminated on the phase shift layer;
having
the phase shift layer contains carbon, oxygen, nitrogen, molybdenum, and silicon, and the average concentration ratio of silicon to molybdenum, Si/Mo, in the thickness direction is smaller than 2.5;
a surface layer located on a surface side away from the transparent substrate in a film thickness direction and having a nitrogen concentration of 45 atm % or more;
an intermediate layer that is closer to the transparent substrate than the surface layer in a thickness direction and has a lower nitrogen concentration than the surface layer;
an etching time shortening layer that is closer to the transparent substrate than the intermediate layer in a thickness direction and has a lower nitrogen concentration than the surface layer;
With
Etching does not form an overhang at the interface with the light-shielding layer.
This has solved the above problem.
(2) The phase shift mask blank of the present invention, in the above (1), wherein the intermediate layer has a higher etching rate than the surface layer.
The etching time reducing layer has an etching rate greater than that of the intermediate layer.
It is possible.
(3) The phase shift mask blank of the present invention, in the above (2), further comprises an etching rate of the intermediate layer that is 1.4 times higher than an etching rate of the surface layer.
It is possible.
(4) The phase shift mask blank of the present invention, in the above (2), wherein an etching rate of the etching time shortening layer is more than 2.5 times that of the surface layer.
It is possible.
(5) The phase shift mask blank of the present invention, in the above (1), wherein the surface layer has a film thickness of 20 nm or less.
It is possible.
(6) The phase shift mask blank of the present invention, in the above (1), wherein the intermediate layer has an oxygen concentration of 7 atm % or less, a carbon concentration of 4 atm % or less, and a thickness of 30 nm or more.
It is possible.
(7) The phase shift mask blank of the present invention, in the above (1), wherein the etching time shortening layer has an oxygen concentration of 7 atm % or more, a carbon concentration of 4 atm % or more, and a film thickness of 30 nm or more.
It is possible.
(8) The phase shift mask blank of the present invention, in the above (1), wherein the phase shift layer has a thickness of 135 nm to 145 nm.
It is possible.
(9) The method for producing a phase shift mask blank of the present invention is the method for producing a phase shift mask blank according to any one of (1) to (8) above,
In forming the phase shift layer, the ratio of molybdenum to silicon is
2.2≦Si/Mo<2.5
Sputtering is performed using a target having a composition set to
It is possible.
(10) A phase shift mask of the present invention is manufactured from the phase shift mask blank according to any one of (1) to (8) above.
It is possible.

(1) A phase shift mask blank according to one aspect of the present invention,
A phase shift mask blank having a mask layer that serves as a phase shift mask,
a phase shift layer made of a metal silicide laminated on a transparent substrate;
a light-shielding layer containing chromium laminated on the phase shift layer;
having
the phase shift layer contains carbon, oxygen, nitrogen, molybdenum, and silicon, and the average concentration ratio of silicon to molybdenum, Si/Mo, in the thickness direction is smaller than 2.5;
a surface layer located on a surface side away from the transparent substrate in a film thickness direction and having a nitrogen concentration of 45 atm % or more;
an intermediate layer that is closer to the transparent substrate than the surface layer in a thickness direction and has a lower nitrogen concentration than the surface layer;
an etching time shortening layer that is closer to the transparent substrate than the intermediate layer in a thickness direction and has a lower nitrogen concentration than the surface layer;
With
Etching does not form an overhang at the interface with the light-shielding layer.

As a result, the chemical resistance of the surface of the molybdenum silicide film can be maintained. The etching time for the phase shift layer can be shortened. The formation of overhangs can be prevented, and the cross-sectional shape of the mask layer can be optimized. The variation in film thickness of the phase shift layer caused by hydrofluoric acid can be suppressed. The phase shift characteristics of the phase shift layer are not changed. All of these can be achieved simultaneously.
Also, the etching rate of the phase shift layer, which is a molybdenum silicide film, can be increased. A phase shift pattern can be formed by fast etching. As a result, even when the phase shift layer is etched with an etching solution containing hydrofluoric acid when manufacturing a phase shift mask from a mask blank, that is, when forming a phase shift pattern from the phase shift layer, the required etching time can be shortened. Even when the phase shift layer is etched with an etching solution containing hydrofluoric acid, overetching can be suppressed. The effect of etching with hydrofluoric acid on a transparent substrate, which is a glass substrate (quartz substrate), can be reduced. The phase shift characteristic due to etching of the glass substrate is not changed.
Furthermore, the surface of the phase shift layer maintains high chemical resistance, the film thickness can be prevented from fluctuating due to a cleaning solution such as an alkali in a cleaning process, and the phase shift characteristics of the phase shift layer are not changed.
These can be achieved simultaneously.

(2) The phase shift mask blank of the present invention, in the above (1), wherein the intermediate layer has a higher etching rate than the surface layer.
The etching time reducing layer has an etching rate greater than that of the intermediate layer.
It is possible.

As a result, the etching time for the phase shift layer can be shortened. The chemical resistance of the surface of the molybdenum silicide film can be maintained. The formation of overhangs can be prevented, and the cross-sectional shape of the mask layer can be optimized. Fluctuations in the film thickness of the phase shift layer caused by hydrofluoric acid can be suppressed. The phase shift characteristics of the phase shift layer are not changed. All of these can be achieved simultaneously.
Also, the etching rate of the phase shift layer, which is a molybdenum silicide film, can be increased. A phase shift pattern can be formed by fast etching. As a result, even when the phase shift layer is etched with an etching solution containing hydrofluoric acid when manufacturing a phase shift mask from a mask blank, that is, when forming a phase shift pattern from the phase shift layer, the required etching time can be shortened. Even when the phase shift layer is etched with an etching solution containing hydrofluoric acid, overetching can be suppressed. The effect of etching with hydrofluoric acid on a transparent substrate, which is a glass substrate, can be reduced. The phase shift characteristics due to etching of the glass substrate are not changed.
Furthermore, the surface of the phase shift layer maintains high chemical resistance, the film thickness can be prevented from fluctuating due to a cleaning solution such as an alkali in a cleaning process, and the phase shift characteristics of the phase shift layer are not changed.
These can be achieved simultaneously.

(3) The phase shift mask blank of the present invention, in the above (2), further comprises an etching rate of the intermediate layer that is 1.4 times higher than an etching rate of the surface layer.
It is possible.

As a result, the chemical resistance of the surface of the molybdenum silicide film can be maintained. The etching time for the phase shift layer can be shortened. The formation of overhangs can be prevented, and the cross-sectional shape of the mask layer can be optimized. The variation in film thickness of the phase shift layer caused by hydrofluoric acid can be suppressed. The phase shift characteristics of the phase shift layer are not changed. All of these can be achieved simultaneously.
Also, the etching rate of the phase shift layer, which is a molybdenum silicide film, can be increased. A phase shift pattern can be formed by fast etching. As a result, even when the phase shift layer is etched with an etching solution containing hydrofluoric acid when manufacturing a phase shift mask from a mask blank, that is, when forming a phase shift pattern from the phase shift layer, the required etching time can be shortened. Even when the phase shift layer is etched with an etching solution containing hydrofluoric acid, overetching can be suppressed. The effect of etching with hydrofluoric acid on a transparent substrate, which is a glass substrate, can be reduced. The phase shift characteristics due to etching of the glass substrate are not changed.
Furthermore, the surface of the phase shift layer maintains high chemical resistance, the film thickness can be prevented from fluctuating due to a cleaning solution such as an alkali in a cleaning process, and the phase shift characteristics of the phase shift layer are not changed.
These can be achieved simultaneously.

(4) The phase shift mask blank of the present invention, in the above (2), wherein an etching rate of the etching time shortening layer is more than 2.5 times that of the surface layer.
It is possible.

As a result, the chemical resistance of the surface of the molybdenum silicide film can be maintained. The etching time for the phase shift layer can be shortened. The formation of overhangs can be prevented, and the cross-sectional shape of the mask layer can be optimized. The variation in film thickness of the phase shift layer caused by hydrofluoric acid can be suppressed. The phase shift characteristics of the phase shift layer are not changed. All of these can be achieved simultaneously.
Also, the etching rate of the phase shift layer, which is a molybdenum silicide film, can be increased. A phase shift pattern can be formed by fast etching. As a result, even when the phase shift layer is etched with an etching solution containing hydrofluoric acid when manufacturing a phase shift mask from a mask blank, that is, when forming a phase shift pattern from the phase shift layer, the required etching time can be shortened. Even when the phase shift layer is etched with an etching solution containing hydrofluoric acid, overetching can be suppressed. The effect of etching with hydrofluoric acid on a transparent substrate, which is a glass substrate, can be reduced. The phase shift characteristics due to etching of the glass substrate are not changed.
Furthermore, the surface of the phase shift layer maintains high chemical resistance, the film thickness can be prevented from fluctuating due to a cleaning solution such as an alkali in a cleaning process, and the phase shift characteristics of the phase shift layer are not changed.
These can be achieved simultaneously.

(5) The phase shift mask blank of the present invention, in the above (1), wherein the surface layer has a film thickness of 20 nm or less.
It is possible.

As a result, the chemical resistance of the surface of the molybdenum silicide film can be maintained. The etching time for the phase shift layer can be shortened. The formation of overhangs can be prevented, and the cross-sectional shape of the mask layer can be optimized. The variation in film thickness of the phase shift layer caused by hydrofluoric acid can be suppressed. The phase shift characteristics of the phase shift layer are not changed. All of these can be achieved simultaneously.
Also, the etching rate of the phase shift layer, which is a molybdenum silicide film, can be increased. A phase shift pattern can be formed by fast etching. As a result, even when the phase shift layer is etched with an etching solution containing hydrofluoric acid when manufacturing a phase shift mask from a mask blank, that is, when forming a phase shift pattern from the phase shift layer, the required etching time can be shortened. Even when the phase shift layer is etched with an etching solution containing hydrofluoric acid, overetching can be suppressed. The effect of etching with hydrofluoric acid on a transparent substrate, which is a glass substrate, can be reduced. The phase shift characteristics due to etching of the glass substrate are not changed.
Furthermore, the surface of the phase shift layer maintains high chemical resistance, the film thickness can be prevented from fluctuating due to a cleaning solution such as an alkali in a cleaning process, and the phase shift characteristics of the phase shift layer are not changed.
These can be achieved simultaneously.

(6) The phase shift mask blank of the present invention, in the above (1), wherein the intermediate layer has an oxygen concentration of 7 atm % or less, a carbon concentration of 4 atm % or less, and a thickness of 30 nm or more.
It is possible.

As a result, the chemical resistance of the surface of the molybdenum silicide film can be maintained. The etching time for the phase shift layer can be shortened. The formation of overhangs can be prevented, and the cross-sectional shape of the mask layer can be optimized. The variation in film thickness of the phase shift layer caused by hydrofluoric acid can be suppressed. The phase shift characteristics of the phase shift layer are not changed. All of these can be achieved simultaneously.
Also, the etching rate of the phase shift layer, which is a molybdenum silicide film, can be increased. A phase shift pattern can be formed by fast etching. As a result, even when the phase shift layer is etched with an etching solution containing hydrofluoric acid when manufacturing a phase shift mask from a mask blank, that is, when forming a phase shift pattern from the phase shift layer, the required etching time can be shortened. Even when the phase shift layer is etched with an etching solution containing hydrofluoric acid, overetching can be suppressed. The effect of etching with hydrofluoric acid on a transparent substrate, which is a glass substrate, can be reduced. The phase shift characteristics due to etching of the glass substrate are not changed.
Furthermore, the surface of the phase shift layer maintains high chemical resistance, the film thickness can be prevented from fluctuating due to a cleaning solution such as an alkali in a cleaning process, and the phase shift characteristics of the phase shift layer are not changed.
These can be achieved simultaneously.

(7) The phase shift mask blank of the present invention, in the above (1), wherein the etching time shortening layer has an oxygen concentration of 7 atm % or more, a carbon concentration of 4 atm % or more, and a film thickness of 30 nm or more.
It is possible.

As a result, the chemical resistance of the surface of the molybdenum silicide film can be maintained. The etching time for the phase shift layer can be shortened. The formation of overhangs can be prevented, and the cross-sectional shape of the mask layer can be optimized. The variation in film thickness of the phase shift layer caused by hydrofluoric acid can be suppressed. The phase shift characteristics of the phase shift layer are not changed. All of these can be achieved simultaneously.
Also, the etching rate of the phase shift layer, which is a molybdenum silicide film, can be increased. A phase shift pattern can be formed by fast etching. As a result, even when the phase shift layer is etched with an etching solution containing hydrofluoric acid when manufacturing a phase shift mask from a mask blank, that is, when forming a phase shift pattern from the phase shift layer, the required etching time can be shortened. Even when the phase shift layer is etched with an etching solution containing hydrofluoric acid, overetching can be suppressed. The effect of etching with hydrofluoric acid on a transparent substrate, which is a glass substrate, can be reduced. The phase shift characteristics due to etching of the glass substrate are not changed.
Furthermore, the surface of the phase shift layer maintains high chemical resistance, the film thickness can be prevented from fluctuating due to a cleaning solution such as an alkali in a cleaning process, and the phase shift characteristics of the phase shift layer are not changed.
These can be achieved simultaneously.

(8) The phase shift mask blank of the present invention, in the above (1), wherein the phase shift layer has a thickness of 135 nm to 145 nm.
It is possible.

As a result, the chemical resistance of the surface of the molybdenum silicide film can be maintained. The etching time for the phase shift layer can be shortened. The formation of overhangs can be prevented, and the cross-sectional shape of the mask layer can be optimized. The variation in film thickness of the phase shift layer caused by hydrofluoric acid can be suppressed. The phase shift characteristics of the phase shift layer are not changed. All of these can be achieved simultaneously.
Also, the etching rate of the phase shift layer, which is a molybdenum silicide film, can be increased. A phase shift pattern can be formed by fast etching. As a result, even when the phase shift layer is etched with an etching solution containing hydrofluoric acid when manufacturing a phase shift mask from a mask blank, that is, when forming a phase shift pattern from the phase shift layer, the required etching time can be shortened. Even when the phase shift layer is etched with an etching solution containing hydrofluoric acid, overetching can be suppressed. The effect of etching with hydrofluoric acid on a transparent substrate, which is a glass substrate, can be reduced. The phase shift characteristics due to etching of the glass substrate are not changed.
Furthermore, the surface of the phase shift layer maintains high chemical resistance, the film thickness can be prevented from fluctuating due to a cleaning solution such as an alkali in a cleaning process, and the phase shift characteristics of the phase shift layer are not changed.
These can be achieved simultaneously.

(9) The method for producing a phase shift mask blank of the present invention is a method for producing a phase shift mask blank according to any one of (1) to (8) above,
In forming the phase shift layer, the ratio of molybdenum to silicon is
2.2≦Si/Mo<2.5
Sputtering is performed using a target having a composition set to
It is possible.

This makes it possible to manufacture the above-mentioned phase shift mask blanks. In particular, by using a target with less silicon relative to molybdenum, it is possible to shorten the wet etching time, thereby reducing the effect of etching on the glass substrate during the etching process and allowing the phase of the phase shift layer to be controlled with high precision, making it possible to manufacture phase shift masks with little line width change even in fine patterns.

(10) A phase shift mask of the present invention is manufactured from the phase shift mask blank according to any one of (1) to (8) above.
It is possible.

This makes it possible to provide a phase shift mask that does not have overhangs.
Furthermore, since the wet etching time is short, it is possible to reduce the consumption of expensive etching liquid.

According to the phase shift mask blank of the present invention, since the phase shift layer has a thin film portion (surface layer) having a high nitrogen concentration layer on the outermost surface thereof, it is possible to improve the chemical resistance of the phase shift film formed of a silicide film while keeping the etching time short.
Since the oxygen concentration and carbon concentration of the bottom layer (etching time reducing layer) of the phase shift layer are higher than those of the intermediate layer, the etching time of the bottom layer is shorter than that of the intermediate layer, and the chemical resistance of the intermediate layer can be improved compared to that of the bottom layer.
Since it is possible to create an etching rate difference between the middle layer and the bottom layer and make the etching rate of the bottom layer larger than that of the middle layer, the cross-sectional shape of the phase shift mask after the photomask is formed approaches a vertical shape and no overhang is formed.
In order to shorten the etching time of the phase shift layer, it is preferable to reduce the value of Si/Mo, which is the ratio of silicon to molybdenum in the silicide film. It is preferable to set the Si/Mo, which is the concentration ratio of silicon to molybdenum in the phase shift layer, to 2.5 or less. To form this silicide film, a sputtering target with Si/Mo less than 2.5 can be used.

According to the present invention, the etching time of the phase shift layer can be shortened. According to the present invention, the phase shift characteristics are not changed by etching the transparent substrate with hydrofluoric acid. According to the present invention, chemical resistance to alkaline solutions can be maintained. According to the present invention, the film thickness fluctuation of the phase shift layer can be suppressed. According to the present invention, the fluctuation of the phase shift characteristics can be prevented. According to the present invention, it is possible to provide such phase shift mask blanks, phase shift masks, and manufacturing methods.

1 is a cross-sectional view showing a first embodiment of a phase shift mask blank according to the present invention. FIG. 2 is a cross-sectional view showing a first embodiment of a phase shift mask blank according to the present invention, and is an enlarged cross-sectional view showing a portion indicated by reference symbol 12p in FIG. 1 is a schematic diagram showing a film formation apparatus in a first embodiment of a method for producing a phase shift mask blank according to the present invention. 1A to 1C are cross-sectional views showing process steps of a manufacturing method of a first embodiment of a phase shift mask according to the present invention. 1A to 1C are cross-sectional views showing process steps of a manufacturing method of a first embodiment of a phase shift mask according to the 1A to 1C are cross-sectional views showing process steps of a manufacturing method of a first embodiment of a phase shift mask according to the present invention. 1A to 1C are cross-sectional views showing process steps of a manufacturing method of a first embodiment of a phase shift mask according to the present invention. 1A to 1C are cross-sectional views showing process steps of a manufacturing method of a first embodiment of a phase shift mask according to the present invention. 1A to 1C are cross-sectional views showing process steps of a manufacturing method of a first embodiment of a phase shift mask according to the present invention. 1A to 1C are cross-sectional views showing process steps of a manufacturing method of a first embodiment of a phase shift mask according to the present invention. 1 is a cross-sectional view showing a first embodiment of a phase shift mask according to the present invention. 4 is a graph showing the relationship between the molybdenum to silicon ratio and the nitrogen concentration and the etching rate in an embodiment of a phase shift mask blank according to the present invention. 4 is a graph showing the relationship between the film thickness and the transmittance of a molybdenum silicide film in an embodiment of a phase shift mask blank according to the present invention. 4 is a graph showing the relationship between oxygen concentration/nitrogen concentration and etching rate ratio in an embodiment of a phase shift mask blank according to the present invention. 4 is a graph showing the relationship between the carbon concentration/nitrogen concentration and the etching rate ratio in an embodiment of a phase shift mask blank according to the present invention. In an embodiment of the phase shift mask blank according to the present invention, the film formation conditions, film thickness, oxygen concentration, carbon concentration, nitrogen concentration, etching rate, and etching rate ratio of the phase shift layer are shown. 1 is a graph showing the results of Auger analysis of a phase shift layer in an experimental example according to the present invention. 1 is an image of a cross section of a mask layer observed by SEM in an example. 1 is an image of a cross section of a mask layer observed by SEM in an example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a phase shift mask blank, a phase shift mask, and a manufacturing method thereof according to the present invention will be described below with reference to the drawings.
Fig. 1 is a cross-sectional view showing a phase shift mask blank in this embodiment. Fig. 2 is an enlarged cross-sectional view showing a portion indicated by reference numeral 12p in Fig. 1. In the figure, reference numeral 10B denotes a phase shift mask blank.

Phase shift mask blank 10B according to this embodiment is intended to be used as a phase shift mask (photomask) for use with exposure light having a wavelength in the range of approximately 365 nm to 436 nm, or exposure light having a wavelength in the range of approximately 290 to 380 nm.
As shown in FIG. 1, the phase shift mask blank 10B according to this embodiment is composed of a glass substrate (transparent substrate) 11, a phase shift layer 12 formed on this glass substrate 11, and a light-shielding layer 13 formed on the phase shift layer 12.

The phase shift layer 12 is formed directly on the surface of the glass substrate 11. The light-shielding layer 13 is provided at a position farther away from the glass substrate 11 than the phase shift layer 12. The light-shielding layer 13 is formed directly on the surface of the phase shift layer 12. The phase shift layer 12 is sandwiched between the glass substrate 11 and the light-shielding layer 13.
The phase shift layer 12 and the light-shielding layer 13 have optical properties required for a photomask. The phase shift layer 12 and the light-shielding layer 13 constitute a mask layer that is a phase shift film that can shift the phase of exposure light by approximately 180°.

The phase shift mask blank 10B according to this embodiment may have a configuration in which the photoresist layer 15 is pre-formed on the mask layer (see FIG. 4 described below).

In addition, in the phase shift mask blank 10B according to this embodiment, in addition to the phase shift layer 12 and the light-shielding layer 13, the mask layer may be configured by laminating an anti-reflection layer, an adhesion layer, a chemical-resistant layer, a protective layer, an etching stopper layer, etc. Furthermore, in the phase shift mask blank 10B according to this embodiment, a photoresist layer 15 may be formed on these laminated films (see FIG. 4 described later).

The glass substrate (transparent substrate) 11 is made of a material having excellent transparency and optical isotropy. For example, a quartz glass substrate is used as the glass substrate 11. The size of the glass substrate 11 is not particularly limited. The size of the glass substrate 11 is appropriately selected according to the substrate to be exposed using the phase shift mask. The substrate to be exposed using the phase shift mask is, for example, a substrate for an FPD such as an LCD (liquid crystal display), a plasma display, or an organic EL (electroluminescence) display.

The glass substrate 11 may be a rectangular substrate with each side being approximately 100 mm. The glass substrate 11 may be a rectangular substrate with each side being greater than 100 mm. The glass substrate 11 may be a rectangular substrate with each side being 2000 mm or more. The glass substrate 11 may be a substrate with a thickness of 1 mm or less. The glass substrate 11 may be a substrate with a thickness of more than 1 mm. The glass substrate 11 may be a substrate with a thickness of several mm. The glass substrate 11 may also be a substrate with a thickness of 10 mm or more.

The glass substrate 11 may also have its surface flatness reduced. The flatness of the glass substrate 11 is reduced by polishing its surface. The glass substrate 11 may have a flatness of, for example, 20 μm or less. Reducing the flatness of the surface of the glass substrate 11 increases the focal depth of the mask. Reducing the flatness of the surface of the glass substrate 11 can greatly contribute to the formation of fine and highly accurate patterns. Furthermore, the glass substrate 11 may have a surface flatness of 10 μm or less. It is preferable that the surface flatness of the glass substrate 11 is reduced.

The phase shift layer 12 is a metal silicide film that contains silicon and a metal such as Ta, Ti, W, Mo, or Zr, or an alloy of these metals.
The phase shift layer 12 is a molybdenum silicide film. The phase shift layer 12 contains O (oxygen). The phase shift layer 12 contains N (nitrogen). The phase shift layer 12 contains C (carbon). The phase shift layer 12 is a MoSi _x (X≧2) film. The phase shift layer 12 is a MoSi ₂ film. The phase shift layer 12 is a MoSi ₃ film. The phase shift layer 12 is a MoSi ₄ film.

The ratio of molybdenum to silicon contained in the phase shift layer 12 is set to a range of 1≦Si/Mo≦2.5. The phase shift layer 12 has an average concentration ratio of silicon to molybdenum, Si/Mo, in the thickness direction of the layer less than 2.5.
Here, the average value of the concentration ratio of silicon to molybdenum, Si/Mo, in the film thickness direction is calculated as the average value of the composition ratio of Si and Mo by measuring the composition in the film thickness direction.
The average value of the concentration ratio Si/Mo in the thickness direction is smaller than 2.5 means that the concentration ratio is set within the range of 1≦Si/Mo≦2.5 in the phase shift layer 12 excluding the surface layer 12 c described later.

The phase shift layer 12 has regions in the film thickness direction where the concentration ratio of silicon to molybdenum, Si/Mo, varies. The phase shift layer 12 has regions in the film thickness direction where the concentration of O (oxygen) varies. The phase shift layer 12 has regions in the film thickness direction where the concentration of N (nitrogen) varies. The phase shift layer 12 has regions in the film thickness direction where the concentration of C (carbon) varies.

The optical characteristics of phase shift layer 12 when used as a phase shift mask are set within a predetermined range. The optical characteristics of phase shift layer 12 are set to a refractive index of about 2.4 to 3.1, an extinction coefficient of 0.3 to 2.1, a phase shift change of 180°, etc., in a wavelength range of about 365 nm to 436 nm. In order to set the optical characteristics within the predetermined range, the composition and film thickness of phase shift layer 12 are set within predetermined ranges.
The composition ratio and film thickness of phase shift layer 12 are set in accordance with the optical characteristics required for phase shift mask 10 to be manufactured.

The phase shift layer 12 has a thickness set in the range of 100 nm to 200 nm. The phase shift layer 12 has a thickness set in the range of 120 nm to 150 nm. The phase shift layer 12 has a thickness set in the range of 135 nm to 145 nm.
The phase shift layer 12 is made up of portions having different compositions in the thickness direction. The phase shift layer 12 is made up of three layers in the thickness direction.

As shown in FIG. 2, the phase shift layer 12 has, in the thickness direction, an etching time reducing layer 12a, an intermediate layer 12b, and a surface layer 12c.
The etching time reducing layer 12a, the intermediate layer 12b, and the surface layer 12c are stacked one on top of the other, and are located at different positions in the thickness direction of the phase shift layer 12.
The etching time reducing layer 12a is in contact with the glass substrate 11. The etching time reducing layer 12a is laminated on the glass substrate 11. The intermediate layer 12b is laminated on the etching time reducing layer 12a. The surface layer 12c is laminated on the intermediate layer 12b. The light blocking layer 13 is laminated on the surface layer 12c.

The surface layer 12c is located on the surface side of the phase shift layer 12 that is farthest from the glass substrate 11 in the thickness direction of the phase shift layer 12. The surface layer 12c has the highest nitrogen concentration (nitrogen content) of all the layers in the phase shift layer 12. The surface layer 12c has a nitrogen concentration of 45 atm% or more.

The surface layer 12c has a carbon concentration (carbon content) in the range of 0.1 atm% to 1.5 atm%. The surface layer 12c has a nitrogen concentration in the range of 40 atm% to 60 atm%. The surface layer 12c has an oxygen concentration (oxygen content) in the range of 0.1 atm% to 4.0 atm%. The surface layer 12c has a silicon concentration (silicon content) in the range of 30.0 atm% to 40.0 atm%. The surface layer 12c has a molybdenum concentration (molybdenum content) in the range of 10.0 atm% to 20.0 atm%.
The surface layer 12c has a concentration ratio of silicon to molybdenum, Si/Mo, in the range of 2.5≦Si/Mo≦2.6.

The surface layer 12c is formed so that the composition ratio does not change in the film thickness direction. The surface layer 12c is formed so that the composition ratio is constant in the film thickness direction.
Here, forming a film with a constant composition ratio in the thickness direction means forming a film to a predetermined thickness without changing the film formation conditions during film formation. Forming a film with a constant composition ratio in the thickness direction means forming a film to a predetermined thickness while maintaining constant film formation conditions during film formation.

The surface layer 12c has a thickness of 20 nm or less. The thickness of the surface layer 12c is set in the range of ⅙ or less of the thickness of the phase shift layer 12. The surface layer 12c has a thickness in the range of 10.0 nm% to 20.0 nm%.
The surface layer 12c has the lowest etching rate among all layers of the phase shift layer 12. The surface layer 12c has an etching rate in the range of 1.0 nm/min to 6.0 nm/min.

The intermediate layer 12b is closer to the glass substrate 11 than the surface layer 12c is in the thickness direction of the phase shift layer 12. The intermediate layer 12b is in contact with the surface layer 12c. The intermediate layer 12b has a lower nitrogen concentration than the surface layer 12c.
The intermediate layer 12b has a higher silicon concentration than the surface layer 12c. The intermediate layer 12b has a higher molybdenum concentration than the surface layer 12c. The intermediate layer 12b has a higher carbon concentration than the surface layer 12c. The intermediate layer 12b has a higher oxygen concentration than the surface layer 12c.
The intermediate layer 12b has an oxygen concentration of 7 atm % or less, a carbon concentration of 4 atm % or less, and a thickness of 30 nm or more.

The intermediate layer 12b has a carbon concentration in the range of 1.5 atm% to 5.0 atm%. The intermediate layer 12b has a nitrogen concentration in the range of 30.0 atm% to 40.0 atm%. The intermediate layer 12b has an oxygen concentration in the range of 4.0 atm% to 8.0 atm%. The intermediate layer 12b has a silicon concentration in the range of 30.0 atm% to 40.0 atm%. The intermediate layer 12b has a molybdenum concentration in the range of 15.0 atm% to 21.0 atm%.
In the intermediate layer 12b, the concentration ratio of silicon to molybdenum, Si/Mo, is set in the range of 1≦Si/Mo≦2.5.

The intermediate layer 12b is formed so that the composition ratio does not change in the film thickness direction. The intermediate layer 12b is formed so that the composition ratio is constant in the film thickness direction.
Here, forming a film with a constant composition ratio in the thickness direction means forming a film to a predetermined thickness without changing the film formation conditions during film formation. Forming a film with a constant composition ratio in the thickness direction means forming a film to a predetermined thickness while maintaining constant film formation conditions during film formation.

The intermediate layer 12b has a thickness greater than that of the surface layer 12c. The intermediate layer 12b has a thickness in the range of 30.0 nm% to 60.0 nm%.
The intermediate layer 12b has a higher etching rate than the surface layer 12c. The etching rate of the intermediate layer 12b is more than 1.4 times the etching rate of the surface layer 12c. The etching rate of the intermediate layer 12b is less than 2.0 times the etching rate of the surface layer 12c. The etching rate of the intermediate layer 12b is in the range of 6.0 nm/min to 9.0 nm/min.

The etching time shortening layer 12a is closer to the glass substrate 11 than the intermediate layer 12b in the thickness direction of the phase shift layer 12. The etching time shortening layer 12a is in contact with the intermediate layer 12b. The etching time shortening layer 12a has a lower nitrogen concentration than the surface layer 12c.

The etching time shortening layer 12a has a lower silicon concentration than the surface layer 12c. The etching time shortening layer 12a has a higher molybdenum concentration than the surface layer 12c. The etching time shortening layer 12a has a higher carbon concentration than the surface layer 12c. The etching time shortening layer 12a has a higher oxygen concentration than the surface layer 12c.

The etching time reducing layer 12a has a lower silicon concentration than the intermediate layer 12b. The etching time reducing layer 12a has a higher molybdenum concentration than the intermediate layer 12b. The etching time reducing layer 12a has a higher carbon concentration than the intermediate layer 12b. The etching time reducing layer 12a has a higher oxygen concentration than the intermediate layer 12b.
The etching time reducing layer 12a has an oxygen concentration of 7 atm % or more, a carbon concentration of 4 atm % or more, and a thickness of 30 nm or more.

The etching time reducing layer 12a has a carbon concentration in the range of 5.0 atm% to 20.0 atm%. The etching time reducing layer 12a has a nitrogen concentration in the range of 30.0 atm% to 40.0 atm%. The etching time reducing layer 12a has an oxygen concentration in the range of 8.0 atm% to 20.0 atm%. The etching time reducing layer 12a has a silicon concentration in the range of 15.0 atm% to 25.5 atm%. The etching time reducing layer 12a has a molybdenum concentration in the range of 21.0 atm% to 25.0 atm%.
The etching time reducing layer 12a has a concentration ratio of silicon to molybdenum, Si/Mo, set in the range of 1≦Si/Mo≦2.5.

The etching time shortening layer 12a is formed so that the composition ratio does not change in the film thickness direction. The etching time shortening layer 12a is formed so that the composition ratio is constant in the film thickness direction.
Here, forming a film with a constant composition ratio in the thickness direction means forming a film to a predetermined thickness without changing the film formation conditions during film formation. Forming a film with a constant composition ratio in the thickness direction means forming a film to a predetermined thickness while maintaining constant film formation conditions during film formation.

The etching time shortening layer 12a has a thickness greater than that of the surface layer 12c. The etching time shortening layer 12a has a thickness greater than that of the intermediate layer 12b. The etching time shortening layer 12a has a thickness in the range of 30.0 nm% to 100.0 nm%.

The etching time reducing layer 12a has a lower nitrogen concentration than the intermediate layer 12b. The etching time reducing layer 12a has a higher etching rate than the intermediate layer 12b. The etching rate of the etching time reducing layer 12a is more than 1.5 times the etching rate of the intermediate layer 12b. The etching rate of the etching time reducing layer 12a is less than 2.0 times the etching rate of the intermediate layer 12b.
The etching time reducing layer 12a has an etching rate greater than that of the surface layer 12c. The etching rate of the etching time reducing layer 12a is greater than 2.5 times that of the surface layer 12c. The etching rate of the etching time reducing layer 12a is less than 5.0 times that of the surface layer 12c. The etching rate of the etching time reducing layer 12a is in the range of 10.0 nm/min to 20.0 nm/min.

The light-shielding layer 13 is laminated on the surface layer 12c. The light-shielding layer 13 is farther away from the glass substrate 11 than the phase shift layer 12. The light-shielding layer 13 is in contact with the surface layer 12c.
The light-shielding layer 13 is mainly composed of Cr (chromium). The light-shielding layer 13 is mainly composed of O (oxygen). The light-shielding layer 13 contains C (carbon). The light-shielding layer 13 contains N (nitrogen).
The light-shielding layer 13 can also be formed by laminating one or more types selected from chromium oxide, chromium nitride, chromium carbide, chromium oxynitride, chromium carbonitride, and chromium oxycarbonitride.

Furthermore, the light-shielding layer 13 may have a composition that varies in the thickness direction. For example, the light-shielding layer 13 may have a nitrogen concentration that is graded in the thickness direction. The light-shielding layer 13 may have an oxygen concentration that is graded in the thickness direction. The light-shielding layer 13 may have a carbon concentration that is graded in the thickness direction.

As described below, the concentrations (composition ratio; atm %) of chromium, nitrogen, carbon, oxygen, etc. of the light-shielding layer 13 are set so as to obtain predetermined optical characteristics. The thickness of the light-shielding layer 13 is set so as to obtain predetermined optical characteristics. The film characteristics of the light-shielding layer 13 vary depending on the composition ratio of chromium, nitrogen, carbon, oxygen, etc. The thickness of the light-shielding layer 13 can be set depending on the optical characteristics required for the phase shift mask 10 in particular.

If the light-shielding layer 13 is not set according to the above conditions, it is not preferable because overhangs are formed at the interface between the phase shift layer 12 and the light-shielding layer 13 by etching in forming the mask pattern. If the light-shielding layer 13 is not set according to the above conditions, it is not preferable because the mask pattern has a non-vertical cross-sectional shape. In addition, if the light-shielding layer 13 is not set according to the above conditions, it is difficult to set the optical characteristics as a photomask to the desired conditions, which is also not preferable.

The light-shielding layer 13 can have a lower refractive index by increasing the oxygen concentration in the chromium compound. The light-shielding layer 13 can have a lower extinction coefficient by increasing the oxygen concentration in the chromium compound. The light-shielding layer 13 can have a lower refractive index by increasing the nitrogen concentration in the chromium compound. The light-shielding layer 13 can have a lower extinction coefficient by increasing the nitrogen concentration in the chromium compound.
The light-shielding layer 13 can have a high refractive index by lowering the oxygen concentration in the chromium compound. The light-shielding layer 13 can have a high extinction coefficient by lowering the oxygen concentration in the chromium compound. The light-shielding layer 13 can have a high refractive index by lowering the nitrogen concentration in the chromium compound. The light-shielding layer 13 can have a high extinction coefficient by lowering the nitrogen concentration in the chromium compound.

In the phase shift mask blank 10B of this embodiment, the etching during patterning does not form an eaves at the interface between the phase shift layer 12 and the light-shielding layer 13. In the phase shift mask blank 10B, the etching during patterning does not cause a change in the film thickness of the phase shift layer 12. In the phase shift mask blank 10B, the etching during patterning does not cause a change in the phase of the set phase shift layer 12. In the phase shift mask blank 10B, the etching during patterning does not cause a change in the surface state of the glass substrate 11.

The manufacturing method of the phase shift mask blank in this embodiment will be described below with reference to the drawings.

FIG. 3 is a schematic diagram showing a manufacturing apparatus for producing a phase shift mask blank in this embodiment.
The phase shift mask blank 10B in this embodiment is manufactured by a manufacturing apparatus shown in FIG.

As shown in FIG. 3, the manufacturing apparatus S10 is an inter-back sputtering apparatus. The manufacturing apparatus S10 has a load chamber S11, an unload chamber S16, and a film forming chamber (vacuum processing chamber) S12.

The load chamber S11 has a transport mechanism S11a and an exhaust mechanism S11f. The transport mechanism S11a transports the glass substrate 11 brought in from the outside to the film formation chamber S12. The exhaust mechanism S11f roughly evacuates the inside of the load chamber S11. The exhaust mechanism S11f is a rotary pump or the like. The load chamber S11 is connected to the film formation chamber S12 via a sealing mechanism S17.

The unloading chamber S16 has a transport mechanism S16a and an exhaust mechanism S16f. The transport mechanism S16a transports the glass substrate 11, which has been transported from the deposition chamber S12 and on which deposition has been completed, to the outside. The exhaust mechanism S16f roughly evacuates the inside of the unloading chamber S16. The exhaust mechanism S16f is a rotary pump or the like. The unloading chamber S16 is connected to the deposition chamber S12 via a sealing mechanism S18.

The deposition chamber S12 has a substrate holding mechanism S12a, a deposition mechanism S13, a deposition mechanism S14, and a gas barrier S12g. The deposition chamber S12 is a mechanism capable of performing two-stage deposition processing with the two deposition mechanisms S13 and S14.

The substrate holding mechanism S12a receives the glass substrate 11 transported by the transport mechanism S11a. The substrate holding mechanism S12a holds the glass substrate 11 inside the film formation chamber S12. The substrate holding mechanism S12a holds the glass substrate 11 so as to face the targets S13b and S14b during film formation. The substrate holding mechanism S12a transports the glass substrate 11 inside the film formation chamber S12. The substrate holding mechanism S12a passes the glass substrate 11 to the transport mechanism S16a.
The substrate holding mechanism S12a is capable of applying bias power to the glass substrate 11 during film formation.

The film formation mechanism S13 is disposed in the film formation chamber S12 at a position adjacent to the load chamber S11. The film formation mechanism S13 performs a first stage of a two-stage film formation process. The film formation mechanism S13 supplies a film formation material for the first stage of the film formation process.
The film forming mechanism S13 has a target S13b, a cathode electrode (backing plate) S13c, a power source S13d, a gas introduction mechanism S13e, and a high vacuum exhaust mechanism S13f.

The target S13b supplies a film forming material for the first step. The target S13b is attached to a cathode electrode S13c. The power source S13d applies a negative sputtering voltage to the backing plate S13c.
The gas introduction mechanism S13e introduces the first-stage film formation gas into the film formation chamber S12. The gas introduction mechanism S13e introduces the first-stage film formation gas into the film formation mechanism S13. The gas introduction mechanism S13e introduces the film formation gas mainly to the vicinity of the cathode electrode S13c. The high vacuum exhaust mechanism S13f exhausts the inside of the film formation chamber S12. The high vacuum exhaust mechanism S13f draws a high vacuum mainly to the vicinity of the cathode electrode S13c. The high vacuum exhaust mechanism S13f is a turbo molecular pump or the like.
The deposition mechanism S13 may include a magnetron magnetic circuit that forms a predetermined magnetic field on the target S13b.

The film formation mechanism S14 is disposed in the film formation chamber S12 at a position adjacent to the unload chamber S16. The film formation mechanism S14 performs a second-stage film formation process of the two-stage film formation process. The film formation mechanism S14 supplies a film formation material for the second-stage film formation process.
The film forming mechanism S14 has a target S14b, a cathode electrode (backing plate) S14c, a power source S14d, a gas introduction mechanism S14e, and a high vacuum exhaust mechanism S14f.

The target S14b supplies a film forming material for the second step. The target S14b is attached to a cathode electrode S14c. The power source S14d applies a negative sputtering voltage to the backing plate S14c.
The gas introduction mechanism S14e introduces the second-stage film formation gas into the film formation chamber S12. The gas introduction mechanism S14e introduces the second-stage film formation gas into the film formation mechanism S14. The gas introduction mechanism S14e introduces the film formation gas mainly to the vicinity of the cathode electrode S14c. The high vacuum exhaust mechanism S14f exhausts the inside of the film formation chamber S12. The high vacuum exhaust mechanism S14f draws a high vacuum mainly to the vicinity of the cathode electrode S14c. The high vacuum exhaust mechanism S14f is a turbo molecular pump or the like.
The film forming mechanism S14 may include a magnetron magnetic circuit that forms a predetermined magnetic field on the target S14b.

The film formation mechanism S13 and the film formation mechanism S14 are adjacent to each other inside the film formation chamber S12.
The gas barrier S12g is disposed inside the film formation chamber S12. The gas barrier S12g is disposed between the film formation mechanism S13 and the film formation mechanism S14. The gas barrier S12g separates the film formation gas in the film formation mechanism S13 and the film formation mechanism S14. The gas barrier S12g is disposed so that the film formation gas is not mixed in the film formation mechanism S13 and the film formation mechanism S14. The gas barrier S12g suppresses the flow of the film formation gas between the film formation mechanism S13 and the film formation mechanism S14. The gas barrier S12g is configured so that the substrate holding mechanism S12a can move between the film formation mechanism S13 and the film formation mechanism S14.

The film-forming mechanism S13 and the film-forming mechanism S14 each have the necessary configurations to perform a two-stage film-forming process. The film-forming mechanism S13 and the film-forming mechanism S14 can implement the necessary conditions to perform a two-stage film-forming process. The film-forming mechanism S13 corresponds to the film-forming of the phase shift layer 12. The film-forming mechanism S14 corresponds to the film-forming of the light-shielding layer 13.

In the film forming mechanism S13, the target S13b has a composition necessary for forming the phase shift layer 12. The material of the target S13b is molybdenum silicide.
In the film formation mechanism S13, a gas introduction mechanism S13e supplies gases necessary for forming the phase shift layer 12. The gas introduction mechanism S13e can supply process gases containing carbon, nitrogen, oxygen, etc. The gas introduction mechanism S13e can supply sputtering gases such as argon gas, nitrogen gas, etc.

The gas introduction mechanism S13e and the high vacuum exhaust mechanism S13f set the gas partial pressure required to form the phase shift layer 12. The gas introduction mechanism S13e and the high vacuum exhaust mechanism S13f can change the supply gas conditions in the film thickness direction of the phase shift layer 12. The gas introduction mechanism S13e and the high vacuum exhaust mechanism S13f set the conditions required to form the etching time reduction layer 12a, the intermediate layer 12b, and the surface layer 12c, respectively.

In the deposition mechanism S13, the power source S13d sets a sputtering voltage corresponding to the deposition of the phase shift layer 12. The power source S13d sets the conditions required for depositing the etching time shortening layer 12a, the intermediate layer 12b, and the surface layer 12c.

In the film forming mechanism S14, the target S14b has a composition necessary for forming the light blocking layer 13. The target S14b is made of a material containing chromium.
In the film formation mechanism S14, the gas introduction mechanism S14e supplies gases necessary for forming the light-shielding layer 13. The gas introduction mechanism S14e is capable of supplying a process gas containing carbon, nitrogen, oxygen, etc. The gas introduction mechanism S14e is capable of supplying a sputtering gas such as argon gas or nitrogen gas.

The gas introduction mechanism S14e and the high vacuum exhaust mechanism S14f set gas partial pressures necessary for forming the light-shielding layer 13. The gas introduction mechanism S14e and the high vacuum exhaust mechanism S14f can change the supply gas conditions in the thickness direction of the light-shielding layer 13.
In the film forming mechanism S14, the power source S14d sets a sputtering voltage corresponding to the formation of the light blocking layer 13.

When manufacturing phase shift mask blank 10B in manufacturing apparatus S10, glass substrate 11 is carried into load chamber S11 as a preparation step.
The glass substrate 11 is transported from the load chamber S11 to the film formation chamber S12 by the transport mechanism S11a. The glass substrate 11 is transported inside the film formation chamber S12 by the substrate holding mechanism S12a. Inside the film formation chamber S12, the glass substrate 11 undergoes two-stage sputtering film formation as a film formation process. After film formation is completed, the glass substrate 11 is transported from the film formation chamber S12 to the unload chamber S16 by the substrate holding mechanism S12a. The glass substrate 11 is taken out to the outside by the transport mechanism S16a.

The method for manufacturing phase shift mask blanks in this embodiment includes a deposition process for forming a mask layer on a glass substrate 11. In the deposition process, a phase shift layer 12 is deposited on the glass substrate 11, and then a light-shielding layer 13 is deposited.

The film formation process includes a phase shift layer formation process and a light-shielding layer formation process.

In the phase shift layer forming step, a phase shift layer 12 is formed on a glass substrate 11. The phase shift layer forming step is performed in a film forming mechanism S13.
In the phase shift layer forming step, the film forming mechanism S13 supplies a process gas and a sputtering gas from the gas introduction mechanism S13e. In the phase shift layer forming step, the film forming mechanism S13 applies a sputtering voltage from the power source S13d. In the phase shift layer forming step, the magnetron magnetic circuit may form a predetermined magnetic field on the target S13b.

In the phase shift layer formation process, the film formation mechanism S13 generates plasma near the target S13b. The plasma excites ions of the sputtering gas. The ions of the sputtering gas collide with the target S13b, ejecting particles of the film formation material. The particles of the film formation material ejected from the target S13b combine with the reactive gas and then adhere to the glass substrate 11. This forms a phase shift layer 12 on the surface of the glass substrate 11.

In the phase shift layer formation process, gas is supplied from the gas introduction mechanism S13e. The supplied gases are sputtering gas, carbon-containing gas, nitrogen-containing gas, oxygen-containing gas, etc. The gas introduction mechanism S13e supplies each gas at a predetermined partial pressure as the film thickness increases. The gas introduction mechanism S13e also switches to control each gas partial pressure as the film thickness increases. In this way, the phase shift layer formation process controls the gas partial pressure to set the composition of the phase shift layer 12 to a set concentration range in the film thickness direction.

The phase shift layer formation process changes the composition of the phase shift layer 12 in the film thickness direction. The phase shift layer formation process varies the partial pressure of each gas in the atmospheric gas according to the film thickness of the formed film. The phase shift layer formation process forms an etching time shortening layer 12a, an intermediate layer 12b, and a surface layer 12c. The phase shift layer formation process includes an etching time shortening layer formation process, an intermediate layer formation process, and a surface layer formation process.

The phase shift layer forming process uses a target S13b with a molybdenum to silicon ratio in a predetermined range. The phase shift layer forming process uses a target S13b with a molybdenum to silicon ratio in a predetermined range. The phase shift layer forming process may use a target S13b with the composition of inclusions other than molybdenum and silicon set to a predetermined state. It is also preferable to appropriately select targets S13b with different compositions.

The phase shift layer forming step comprises a step of forming a phase shift layer having a molybdenum to silicon ratio of:
2.2≦Si/Mo<2.5
Sputtering is performed using a target having a composition set at

In the phase shift layer forming step, the power source S13d applies a plasma forming power to the cathode electrode S13c within a predetermined range.In the phase shift layer forming step, the power source S13d applies a plasma forming power to the cathode electrode S13c within a predetermined range.
In the phase shift layer forming step, the substrate holding mechanism S12 a may apply bias power to the glass substrate 11 .
In the phase shift layer forming step, the sputtering power applied from the power source S13d and the bias power applied from the substrate holding mechanism S12a are switched between the etching time reducing layer forming step, the intermediate layer forming step, and the surface layer forming step.

The etching time reducing layer forming process maintains a constant gas partial pressure during this time. When the etching time reducing layer 12a reaches a predetermined thickness, the etching time reducing layer forming process ends. When the etching time reducing layer forming process ends, the intermediate layer forming process begins. The intermediate layer forming process switches to a gas partial pressure state corresponding to the formation of the intermediate layer 12b.

During the intermediate layer formation process, the gas partial pressure is maintained at a constant level. The intermediate layer formation process ends when the intermediate layer 12b has reached a predetermined film thickness. When the intermediate layer formation process ends, the surface layer formation process begins. The surface layer formation process switches to a gas partial pressure state corresponding to the formation of the surface layer 12c.

During the surface layer forming process, the gas partial pressure is maintained constant. The surface layer forming process ends when the surface layer 12c reaches a predetermined thickness. When the surface layer forming process ends, the phase shift layer forming process ends.
The etching time reducing layer forming step, the intermediate layer forming step, and the surface layer forming step use the same target S13b. The etching time reducing layer forming step, the intermediate layer forming step, and the surface layer forming step may use different targets by replacing the target S13b. In forming the phase shift layer 12, the target S13b may be appropriately replaced if necessary.

Examples of oxygen-containing gases include _CO2 (carbon dioxide), _O2 (oxygen), _N2O (dinitrogen monoxide), NO (nitric oxide), _and CO (carbon monoxide). Examples of carbon-containing gases include _CO2 (carbon dioxide), _CH4 (methane), _C2H6 (ethane), and CO (carbon monoxide). Examples of nitrogen-containing gases include _N2 (nitrogen gas), _N2O (dinitrogen monoxide), NO (nitric oxide), _N2O (dinitrogen monoxide), and _NH3 (ammonia).

In the light-shielding layer forming step, the light-shielding layer 13 is formed on the glass substrate 11. In the light-shielding layer forming step, the light-shielding layer 13 is laminated on the phase shift layer 12. The light-shielding layer forming step is performed in a film forming mechanism S14.
In the light shielding layer forming process, the film forming mechanism S14 supplies a process gas and a sputtering gas from the gas introduction mechanism S14e. In the light shielding layer forming process, the film forming mechanism S14 applies a sputtering voltage from the power source 14d. In the light shielding layer forming process, the magnetron magnetic circuit may form a predetermined magnetic field on the target S14b.

In the light-shielding layer formation process, the film-forming mechanism S14 generates plasma near the target S14b. The plasma excites ions of the sputtering gas. The ions of the sputtering gas collide with the target S14b, ejecting particles of the film-forming material. The particles of the film-forming material ejected from the target S14b combine with the reactive gas and then adhere to the surface of the phase shift layer 12. This causes the light-shielding layer 13 to be laminated on the surface of the phase shift layer 12.

In the light-shielding layer forming step, a target S14b containing chromium is used. In the light-shielding layer forming step, a target S14b made of chromium is used. In the formation of the light-shielding layer 13, the target S14b can be appropriately replaced if necessary.
In the light-shielding layer forming step, the power source S14d sets the plasma-forming power applied to the cathode electrode S14c within a predetermined range.In the light-shielding layer forming step, the power source S14d sets the plasma-forming power applied to the cathode electrode S14c within a predetermined range.
In the light-shielding layer forming step, the substrate holding mechanism S12 a may apply bias power to the glass substrate 11 .
In the light-shielding layer forming step, the sputtering power applied from the power source S14d and the bias power applied from the substrate holding mechanism S12a may be changed according to the film thickness of the light-shielding layer 13.

In the light-shielding layer formation process, gas is supplied from the gas introduction mechanism S14e. The supplied gases are sputtering gas, carbon-containing gas, nitrogen-containing gas, oxygen-containing gas, etc. The gas introduction mechanism S14e supplies each gas at a predetermined partial pressure as the film thickness increases. The gas introduction mechanism S14e also switches to control the partial pressure of each gas as the film thickness increases. In this way, the light-shielding layer formation process controls the gas partial pressure to set the composition of the light-shielding layer 13 to a set concentration range in the film thickness direction.

The light-shielding layer forming process may vary the composition of the light-shielding layer 13 in the film thickness direction. In this case, the light-shielding layer forming process varies the partial pressure of each gas in the atmospheric gas according to the thickness of the film formed. The light-shielding layer forming process may keep the composition of the light-shielding layer 13 constant in the film thickness direction. In this case, the light-shielding layer forming process keeps the partial pressure of each gas in the atmospheric gas constant according to the thickness of the film formed.

The manufacturing method of the phase shift mask blank may include, in addition to the phase shift layer forming step and the light-shielding layer forming step, a lamination step of an etching stop layer, a protective layer, an adhesion layer, a chemical-resistant layer, an anti-reflection layer, etc., when the phase shift mask blank 10B is laminated with these layers.
In this case, the film can be formed by sputtering under sputtering conditions such as corresponding targets and gases, or the film can be laminated by other film forming methods to form phase shift mask blank 10B of this embodiment.

The following describes a manufacturing method for producing a phase shift mask 10 from the phase shift mask blank 10B of this embodiment.

FIG. 4 is a cross-sectional view showing the steps of a method for manufacturing a phase shift mask according to the present embodiment. FIG. 5 is a cross-sectional view showing the steps of a method for manufacturing a phase shift mask according to the present embodiment. FIG. 6 is a cross-sectional view showing the steps of a method for manufacturing a phase shift mask according to the present embodiment. FIG. 7 is a cross-sectional view showing the steps of a method for manufacturing a phase shift mask according to the present embodiment. FIG. 8 is a cross-sectional view showing the steps of a method for manufacturing a phase shift mask according to the present embodiment. FIG. 9 is a cross-sectional view showing the steps of a method for manufacturing a phase shift mask according to the present embodiment. FIG. 10 is a cross-sectional view showing the steps of a method for manufacturing a phase shift mask according to the present embodiment. FIG. 11 is a cross-sectional view showing a phase shift mask according to the present embodiment.
Phase shift mask (photomask) 10 in this embodiment is manufactured from phase shift mask blank 10 B. Phase shift mask 10 has a pattern formed in phase shift layer 12 and light-shielding layer 13, as shown in FIG.

The method for manufacturing the phase shift mask 10 includes a first resist pattern forming process, a first light-shielding pattern forming process, a first cleaning process, a phase shift pattern forming process, a second cleaning process, a second resist pattern forming process, a second light-shielding pattern forming process, and a third cleaning process.

In the first resist pattern forming step, first, a first photoresist layer 15 is formed on the outermost surface of phase shift mask blank 10B, as shown in Fig. 4. In the first resist pattern forming step, phase shift mask blank 10B having first photoresist layer 15 formed on its outermost surface in advance may be prepared.
The first photoresist layer 15 may be a positive type or a negative type. The first photoresist layer 15 is compatible with etching of so-called chromium-based materials and molybdenum silicide-based materials. The first photoresist layer 15 is a liquid resist. The first photoresist layer 15 is applied by a coating process.

The first resist pattern formation process exposes and develops the first photoresist layer 15. As a result, the first resist pattern formation process forms a first resist pattern 15P1 on the surface of the light-shielding layer 13 that is farther away from the glass substrate 11 than the phase shift layer 12, as shown in FIG. 5. The first resist pattern 15P1 functions as an etching mask for the light-shielding layer 13 and the phase shift layer 12.

In the first resist pattern formation process, the shape of the first resist pattern 15P1 is appropriately determined according to the etching pattern of the light-shielding layer 13 and the phase shift layer 12. In the first resist pattern formation process, a shape having an opening width corresponding to the opening width dimension of the light-transmitting region 10L is set (see Figures 7 to 11).

After the first resist pattern forming process is completed, the first light-shielding pattern forming process is performed. In the first light-shielding pattern forming process, the light-shielding layer 13 is etched through the first resist pattern 15P1. In the first light-shielding pattern forming process, the light-shielding layer 13 is wet-etched using an etching solution. In the first light-shielding pattern forming process, the first light-shielding pattern 13P1 is formed as shown in FIG. 6.

In the first light-shielding pattern forming step, an etching solution for a chromium-based material is used as an etching solution. The etching solution for the chromium-based material may be an etching solution containing diammonium cerium nitrate. The etching solution for the chromium-based material is preferably, for example, diammonium cerium nitrate containing an acid such as nitric acid or perchloric acid.
In the light-shielding pattern forming step, since the phase shift layer 12 is made of molybdenum silicide, the phase shift layer 12 is hardly etched by a chromium-based etching solution.

After the first light-shielding pattern forming step is completed, a first cleaning step is carried out as necessary.
In the first cleaning step, an alkaline liquid is used as a cleaning liquid. The alkaline liquid may be a sodium hydroxide solution or a mixture of ammonia and hydrogen peroxide. Since the phase shift layer 12 has a surface layer 12c, the thickness of the phase shift layer 12 is not changed by cleaning with an alkaline liquid in the first cleaning step. In addition, since the surface of the glass substrate 11 is not exposed, the surface of the glass substrate 11 is not roughened by cleaning with an alkaline liquid.

Next, a phase shift pattern forming process is performed. In the phase shift pattern forming process, the phase shift layer 12 is etched. In the phase shift pattern forming process, the phase shift layer 12 is etched through the first light-shielding pattern 13P1 and the first resist pattern 15P1. In the phase shift pattern forming process, wet etching is performed using an etching solution. In the phase shift pattern forming process, as shown in FIG. 7, a phase shift pattern 12P1 is formed. The phase shift pattern 12P1 has a shape that is hollowed out more than the first light-shielding pattern 13P1.

The phase shift pattern formation process uses an etching solution capable of etching the phase shift layer 12 made of molybdenum silicide. The phase shift pattern formation process uses an etching solution containing a fluorine compound and an oxidizing agent. The phase shift pattern formation process uses an etching solution containing at least one fluorine compound selected from hydrofluoric acid, hydrosilicic acid, and ammonium hydrogen fluoride. The phase shift pattern formation process uses an etching solution containing at least one oxidizing agent selected from hydrogen peroxide, nitric acid, and sulfuric acid.

The phase shift layer 12 is composed of a molybdenum silicide compound. The molybdenum silicide compound can be etched, for example, with a mixture of ammonium hydrogen fluoride and hydrogen peroxide. In contrast, the chromium compound forming the light-shielding layer 13 can be etched, for example, with a mixture of ammonium cerium nitrate and perchloric acid.

During each wet etching, the selection ratio between the light-shielding layer 13 and the phase shift layer 12 becomes very large. Therefore, after the first light-shielding pattern 13P1 and the phase shift pattern 12P1 are formed by etching, it is possible to obtain a good cross-sectional shape of the phase shift mask 10 that is close to vertical.

Here, the phase shift layer 12 has a surface layer 12c. The surface layer 12c has a high nitrogen concentration. Therefore, the surface layer 12c has a low etching rate (ER) with respect to a molybdenum silicide-based etching solution. The surface layer 12c has high chemical resistance to alkaline solutions.

The phase shift layer 12 includes an intermediate layer 12b and an etching time shortening layer 12a.
The intermediate layer 12b and the etching time reducing layer 12a have a lower nitrogen concentration than the surface layer 12c. The intermediate layer 12b and the etching time reducing layer 12a have oxygen and carbon concentrations set within the above-mentioned ranges, unlike the surface layer 12c. Therefore, the intermediate layer 12b and the etching time reducing layer 12a have a higher etching rate (ER) with respect to a molybdenum silicide-based etching solution than the surface layer 12c.

The intermediate layer 12b and the etching time shortening layer 12a are different from the surface layer 12c in that the nitrogen concentration, oxygen concentration, and carbon concentration are set within the above-mentioned ranges. Therefore, the intermediate layer 12b has a higher etching rate (ER) for a molybdenum silicide-based etching solution than the surface layer 12c. The etching time shortening layer 12a has a higher etching rate (ER) for a molybdenum silicide-based etching solution than the intermediate layer 12b.

Therefore, the etching time for the entire phase shift layer 12 is shorter than when the total thickness is the surface layer 12c.
This makes it possible to shorten the etching time and suppress the influence of the etching solution on the glass substrate 11 .

The surface layer 12c, intermediate layer 12b, and etching time-reducing layer 12a have the above-mentioned compositions, and their respective film thicknesses are set as described above.

The nitrogen concentration, carbon concentration, and oxygen concentration of the surface layer 12c close to the light-shielding layer 13 are set within the above-mentioned ranges. As a result, in the phase shift pattern formation process, the etching rate of the surface layer 12c in the phase shift layer 12 close to the light-shielding layer 13 is lower. Therefore, in the phase shift layer 12, the progress of etching of the surface layer 12c is delayed compared to the etching of the intermediate layer 12b and the etching time shortening layer 12a.

The nitrogen concentration, carbon concentration, and oxygen concentration of the phase shift layer 12 close to the glass substrate 11 are set in the above-mentioned ranges, unlike those of the surface layer 12c. In the phase shift pattern formation process, the etching rate of the phase shift layer 12 close to the glass substrate 11 is higher than that of the surface layer 12c.

Moreover, the intermediate layer 12b and the etching time reducing layer 12a are formed so that the etching rate gradually increases as the etching proceeds.
As a result, the phase shift pattern 12P1 has a shape hollowed out more than the first light blocking pattern 13P1.

The surface layer 12c is exposed to the etching solution for a long time. However, the surface layer 12c has a small etching rate. In contrast, the intermediate layer 12b and the etching time reducing layer 12a are exposed to the etching solution for a shorter time than the surface layer 12c. The intermediate layer 12b and the etching time reducing layer 12a have a larger etching rate than the surface layer 12c. The etching of the surface layer 12c of the phase shift layer 12 progresses more slowly than the etching of the intermediate layer 12b and the etching time reducing layer 12a.

Moreover, the intermediate layer 12b is exposed to the etching solution for a shorter period of time than the surface layer 12c, and the intermediate layer 12b has a higher etching rate than the surface layer 12c.
Furthermore, the etching time reducing layer 12a is exposed to the etching solution for a shorter period of time than the intermediate layer 12b. The etching time reducing layer 12a has a higher etching rate than the intermediate layer 12b. In the phase shift layer 12, the etching of the intermediate layer 12b proceeds more slowly than the etching of the etching time reducing layer 12a.

As a result, the surface layer 12c, the intermediate layer 12b, and the etching time-reducing layer 12a are each etched appropriately. The phase shift pattern 12P1 does not create an overhang at the interface with the first light-shielding pattern 13P1. In addition, the cross-sectional shape of the phase shift layer 12 is perpendicular to the surface of the glass substrate 11.

The phase shift pattern 12P1 has a wall surface formed by etching using the first light-shielding pattern 13P1, which has an angle (taper angle) θ that is close to a right angle with the surface of the glass substrate 11. The angle between the wall surface of the phase shift pattern 12P1 and the surface of the glass substrate 11 can be approximately 90°. The angle between the wall surface of the phase shift pattern 12P1 and the surface of the glass substrate 11 can be constant in the thickness direction.

The phase shift pattern 12P1 has a surface layer 12c in contact with the first light-shielding pattern 13P1. The surface layer 12c has a high nitrogen concentration. However, the surface layer 12c is etched simultaneously with the etching of the intermediate layer 12b and the etching time-reducing layer 12a. This ensures that the phase shift pattern 12P1 can be etched reliably at the interface with the first light-shielding pattern 13P1 in the phase shift pattern formation process. No portion of the first light-shielding pattern 13P1 remains unetched at the interface with the phase shift pattern 12P1. This ensures reliable pattern formation.

The phase shift layer 12 is formed by a process in which the ratio of molybdenum to silicon is:
2.2≦Si/Mo<2.5
The phase shift mask is formed by sputtering using a target having a composition set to 0.01% by weight. This allows the etching rate during wet etching to be increased as a film characteristic, thereby making it possible to speed up etching. This allows the effect of glass etching to be reduced in the patterning process used to fabricate the phase shift mask to be reduced. This makes it possible to fabricate a phase shift mask in which the phase in the phase shift layer is controlled with high precision. Furthermore, it is possible to reduce the consumption of expensive wet etching liquid, thereby achieving the effect of reducing costs.

After the phase shift pattern forming process is completed, a second cleaning process is performed as necessary. The second cleaning process is a resist removing process. In the second cleaning process, the first resist pattern 15P1 is removed as shown in FIG.
In the second cleaning step, a sodium hydroxide solution, a potassium hydroxide solution, and a tetramethylammonium hydroxide (TMAH) solution are used as cleaning liquids. Since the phase shift pattern 12P1 has the surface layer 12c, the film thickness of the phase shift pattern 12P1 does not change due to cleaning with an alkaline liquid in the second cleaning step.

After the second cleaning step is completed, a second resist pattern forming step is carried out, if necessary.
In the second resist pattern forming step, first, a second photoresist layer is formed on the surface of the first light-shielding pattern 13P1. In the second resist pattern forming step, a second photoresist layer similar to the first photoresist layer 15 is formed.
The second photoresist layer may be a positive type or a negative type. The second photoresist layer is compatible with etching of so-called chromium-based materials and molybdenum silicide-based materials. The second photoresist layer is a liquid resist. The second photoresist layer is applied by a coating process.

The second resist pattern formation process exposes and develops the second photoresist layer. As a result, the second resist pattern formation process forms a second resist pattern 15P2 on the surface of the first light-shielding pattern 13P1 that is farther away from the glass substrate 11 than the phase shift pattern 12P1, as shown in FIG. 9. The second resist pattern 15P2 functions as an etching mask for the first light-shielding pattern 13P1.

In the second resist pattern formation process, the shape of the second resist pattern 15P2 is appropriately determined according to the etching pattern of the first light-shielding pattern 13P1. In the second resist pattern formation process, the shape is set to have an opening width corresponding to the opening width dimension of the phase shift region 10P (see FIG. 11).

After the second resist pattern forming process is completed, the second light-shielding pattern forming process is performed. In the second light-shielding pattern forming process, the first light-shielding pattern 13P1 is etched through the second resist pattern 15P2. In the second light-shielding pattern forming process, the first light-shielding pattern 13P1 is wet-etched using an etching solution. In the second light-shielding pattern forming process, as shown in FIG. 10, the second light-shielding pattern 13P2 is formed.
In the second light-shielding pattern forming step, a phase shift region 10P is formed. In the phase shift region 10P, the surface of the phase shift pattern 12P1 is exposed. In the second light-shielding pattern forming step, a second light-shielding pattern 13P2 is formed in correspondence with the phase shift region 10P.

In the second light-shielding pattern formation process, an etching solution made of a chromium-based material is used as the etching solution, as in the first light-shielding pattern formation process. In the second light-shielding pattern formation process, an etching solution containing diammonium cerium nitrate is used as the etching solution. In the second light-shielding pattern formation process, diammonium cerium nitrate containing an acid such as nitric acid or perchloric acid is used as the etching solution.

The phase shift pattern 12P1 has a surface layer 12c. This improves the etching resistance of the phase shift pattern 12P1 to chromium-based etching solutions. At the same time, because the phase shift layer 12 has the surface layer 12c, the film thickness of the phase shift pattern 12P1 can be prevented from fluctuating. Because the phase shift layer 12 has the surface layer 12c, the adhesion with the light-shielding layer 13 is improved, and the etched shape can be prevented from collapsing. By preventing film thickness fluctuations, the phase shift pattern 12P1 can be prevented from fluctuating in phase shift characteristics.

After the second light-shielding pattern forming step is completed, a third cleaning step is carried out as necessary.
The third cleaning step is a resist removal step for removing the second resist pattern 15P2.
In the third cleaning step, an alkaline liquid is used as a cleaning liquid. The alkaline liquid used is the same as that used in the first or second cleaning step. Since the phase shift layer 12 has a surface layer 12c, the thickness of the phase shift layer 12 does not change due to cleaning with an alkaline liquid in the third cleaning step. Since the thickness of the phase shift pattern 12P1 does not change in the phase shift region 10P, it is possible to prevent the phase shift characteristics from fluctuating.
In addition, since the processing time is short, the surface of the glass substrate 11 is not roughened by cleaning with an alkaline solution in the light-transmitting region 10L. Since the surface of the glass substrate 11 is not roughened in the light-transmitting region 10L, it is possible to prevent the phase shift characteristics from fluctuating.

The third cleaning process shortens the processing time. The third cleaning process makes it possible to suppress the effect of the cleaning solution on the phase shift pattern 12P1 and the glass substrate 11 in the light-transmitting region 10L and the phase shift region 10P that are exposed to the cleaning solution.

A light-transmitting region 10L is formed where the surface of the glass substrate 11 is exposed, and a phase shift region 10P is formed where the phase shift pattern 12P1 remains and is exposed. This produces a phase shift mask 10, as shown in FIG. 11.

The film characteristics of the phase shift layer 12 and the light-shielding layer 13 in this embodiment, particularly the film characteristics of the phase shift layer 12, are described below.

In the phase shift mask blanks 10B, a mask layer is formed on a glass substrate 11. The mask layer is formed by using a sputtering method or the like. The mask layer is first formed as a phase shift layer 12. The phase shift layer 12 is formed of a molybdenum silicide compound. The molybdenum silicide compound formed here is a film containing molybdenum, silicon, oxygen, nitrogen, carbon, and the like. At this time, the composition of molybdenum, silicon, oxygen, nitrogen, and carbon contained in the film and the film thickness corresponding to the composition are controlled. This allows the phase shift layer 12 to have the desired transmittance and phase.

The mask layer is then used to form the light-shielding layer 13. The light-shielding layer 13 is a chromium compound film. The light-shielding layer 13 is formed by using a sputtering method or the like. The chromium compound formed here is a film containing chromium, oxygen, nitrogen, carbon, and the like.
When molybdenum silicide is used for the phase shift layer 12 , a light shielding layer 13 made of a chromium compound is laminated on the phase shift layer 12 .

After the formation of phase shift layer 12, a chromium compound that will become light-shielding layer 13 is formed, whereby phase shift mask blank 10B for forming phase shift mask 10 can be constructed.
A phase shift mask 10 is formed from this phase shift mask blank 10B.
A resist pattern is formed on the formed phase shift mask blank 10B, and then the phase shift mask blank 10B is etched, whereby the phase shift mask 10 can be formed.

As a result of intensive research by the inventors, it was found that in order to increase the chemical resistance and etching rate of the phase shift layer 12 and prevent the formation of eaves, it is important to form the phase shift layer 12 from a molybdenum silicide film and to appropriately control the composition (concentration) of the molybdenum silicide film and the composition distribution in the film thickness direction.

When the phase shift layer 12 is formed from a molybdenum silicide film, it is necessary to etch it with an etching solution containing hydrofluoric acid when forming the phase shift mask 10. For this reason, it is desirable to use a molybdenum silicide film with as fast an etching rate as possible in order to reduce the effects of etching the glass substrate 11.

Figure 12 shows the relationship between the nitrogen concentration in the film and the etching rate when a molybdenum silicide film is formed using molybdenum silicide targets with different target compositions. The results shown in Figure 12 show that by using molybdenum silicide with a low silicon content as the target composition, a molybdenum silicide film with a fast etching rate can be formed.

Furthermore, for the molybdenum silicide target, it is possible to form a target with a desired composition ratio by mixing the material MoSi ₂ , which is a crystal of molybdenum silicon, and Si. For this purpose, it is difficult to form a target with a stable composition unless a certain amount of silicon is present in excess of MoSi _2. For this reason, it was found that a target with a high relative density can be stably formed by increasing the silicon composition to a molybdenum to silicon composition ratio of Mo:Si = 1:2.3.

For this reason, a high-density target with a molybdenum to silicon composition ratio of 1:2.3 to 1:2.5 is used as the molybdenum silicide composition ratio, thereby lowering the silicon concentration in the molybdenum silicide film. It has been found that this increases the etching rate (ER) of the molybdenum silicide film. It is possible to form a molybdenum silicide film with an etching rate that keeps the etching of the glass substrate 11 in a suppressed state. This makes it possible to manufacture phase shift mask blanks 10B that are suitable for production and have reduced effects of defects.

A target having a molybdenum to silicon composition ratio of 1:2.3 is used when forming the molybdenum silicide film as the phase shift layer 12. At the same time, when forming the molybdenum silicide film as the phase shift layer 12, the flow rates of argon and nitrogen during film formation are changed.
Chemicals such as acids and alkalis are usually used in forming patterns as part of the manufacturing process for phase shift mask 10. During these processes, it is necessary to suppress changes in phase shift angle, film thickness, and transmittance.

It was found that increasing the nitrogen concentration in the molybdenum silicide film improved its resistance to acids and alkalis. This shows that it is important to increase the nitrogen concentration in the molybdenum silicide film in order to improve its resistance to chemicals.

Nitrogen was added when forming a molybdenum silicide film using a target with a molybdenum to silicon composition ratio of 1:2.3. The relationship between the thickness of the molybdenum silicide film and the transmittance at a wavelength of 365 nm was examined by changing the thickness of the molybdenum silicide film. The nitrogen concentration of the molybdenum silicide film was 48.1% (45 atm% or more). The results are shown in FIG.
Here, the transmittance (%) was normalized to 1 when the film thickness was 10 nm.

These results show that in a high nitrogen concentration molybdenum silicide film, by making the film thickness greater than 10 nm, the transmittance does not change even if the film thickness changes. Therefore, in the etching process, cleaning process, etc., it is preferable to make the film thickness of the high nitrogen concentration molybdenum silicide film greater than 10 nm. In order to have sufficient chemical resistance, it is preferable to make the film thickness of the surface layer 12c greater than 10 nm.

Furthermore, the gas conditions used when forming the molybdenum silicide film were changed to change the nitrogen concentration and oxygen concentration in the molybdenum silicide film. For this molybdenum silicide film, the relationship between the etch rate ratio and the ratio of the nitrogen concentration (N concentration) and the oxygen concentration (O concentration) was investigated. The results are shown in Figure 14.

From these results, it can be seen that the etching rate of the molybdenum silicide film changes by changing the ratio of the oxygen concentration to the nitrogen concentration. It can be seen that the etching rate increases by lowering the nitrogen concentration of the molybdenum silicide film. It can be seen that the etching rate increases by increasing the oxygen concentration of the molybdenum silicide film.

Furthermore, the nitrogen concentration and carbon concentration in the molybdenum silicide film were changed by changing the gas conditions when forming the molybdenum silicide film. The relationship between the etching rate and the ratio of the nitrogen concentration and the carbon concentration (C concentration) for this molybdenum silicide film was investigated. The results are shown in Figure 15.

From these results, it can be seen that the etching rate of the molybdenum silicide film changes by changing the ratio of the carbon concentration to the nitrogen concentration. It can be seen that the etching rate increases by lowering the nitrogen concentration of the molybdenum silicide film. It can be seen that the etching rate increases by increasing the carbon concentration of the molybdenum silicide film.

Based on these results, the concentration distribution in the film thickness direction of the phase shift layer 12 is set. In other words, the composition of each of the surface layer 12c, the intermediate layer 12b, and the etching time shortening layer 12a, as well as their respective film thicknesses and etching rates (Etch Rates) are set.

As a phase shift mask used for a display, a phase shift mask 10 having a transmittance of 5% or more at a phase of 180° at a wavelength of 365 nm is used.
Phase shift mask 10 requires phase shift layer 12 to be relatively thick, about 100 to 150 nm. In addition, large-area photomasks for flat displays are processed using wet etching when forming patterns. For this reason, it is necessary to prevent the pattern formed in phase shift mask 10 from becoming tapered.

For this purpose, the wet etching rate in the thickness direction is changed by controlling the deposition conditions of the molybdenum silicide film in the thickness direction, which makes it possible to make the cross-sectional shape of the phase shift mask closer to vertical and to prevent the formation of eaves.
Specifically, when the phase shift layer 12 was formed, the gas partial pressure was set as shown in Fig. 16. In Fig. 16, A is the surface layer 12c, B is the intermediate layer 12b, and C is the etching time reducing layer 12a.

The phase shift layer 12 is a silicide film having a laminated structure of three or more layers, which is formed by using a target having a molybdenum to silicon composition ratio of Mo:Si=1:2.3 or less.
The surface layer 12c is formed to have a nitrogen concentration of 45% or more and a thickness of 20 nm or less.
The intermediate layer 12b is formed to have an oxygen concentration of 7 atm % or less, a carbon concentration of 4% or less, and a thickness of 30 nm or more.
The etching time shortening layer 12a is formed to have an oxygen concentration of 7 atm % or more, a carbon concentration of 4 atm % or more, and a thickness of 30 nm or more.
The intermediate layer 12b and the etching time reducing layer 12a are formed with a silicon to molybdenum concentration ratio Si/Mo of 2 or less.

The phase shift layer 12 has a thin film with a high nitrogen concentration layer on its outermost surface. This makes it possible to improve the chemical resistance of the phase shift layer 12 formed from a silicide film while keeping the etching time short.

The oxygen concentration and carbon concentration of the etching time shortening layer 12a are higher than those of the intermediate layer 12b. Therefore, the etching time of the etching time shortening layer 12a is shorter than that of the intermediate layer 12b. Furthermore, the chemical resistance characteristics of the intermediate layer 12b can be improved compared to that of the etching time shortening layer 12a.

The intermediate layer 12b and the etching time reducing layer 12a are formed so that there is a difference between the etching rate of the intermediate layer 12b and the etching rate of the etching time reducing layer 12a. This makes it possible to make the etching rate of the etching time reducing layer 12a smaller than the etching rate of the intermediate layer 12b. Therefore, after the phase shift mask 10 is formed, the cross-sectional shape of the phase shift layer 12 can be made closer to a vertical shape.

To shorten the total etching time of the phase shift layer 12, which is a silicide film, it is desirable to reduce the Si/Mo ratio. The Si/Mo ratio should be 2.5 or less. The ratio of silicon to molybdenum in the phase shift layer 12 can be achieved by using a sputtering target with a Si/Mo ratio of 2.5 or less.

The following describes an embodiment of the present invention.

<Experimental Example 1>
In Experimental Example 1, a three-layered film of a molybdenum silicide compound was formed as a phase shift layer 12 on a glass substrate by using a sputtering method or the like. The molybdenum silicide compound film formed here is a film containing molybdenum, silicon, oxygen, nitrogen, carbon, etc. The three-layered film of the molybdenum silicide compound is a surface layer 12c, an intermediate layer 12b, and an etching time shortening layer 12a. The three-layered film of the molybdenum silicide compound has a nitrogen concentration distribution in the film thickness direction.

In the sputtering for forming the film of the molybdenum silicide compound, a target having a molybdenum to silicon ratio of 1:2.3 was used.
The atmospheric gas in the sputtering was nitrogen gas, carbon dioxide, and argon. The partial pressure of the carbon dioxide gas was changed from 0 to 100%, and the partial pressure of the nitrogen gas was changed from 0 to 100%.

The deposition conditions for the surface layer 12c, intermediate layer 12b, and etching time shortening layer 12a, which are phase shift layers, are shown in Fig. 16. In Fig. 16, A is the surface layer 12c, B is the intermediate layer 12b, and C is the etching time shortening layer 12a. These results were obtained by depositing each single layer film on a glass substrate under preset deposition conditions, and using Auger electron spectroscopy to evaluate the composition of each sample on the separate glass substrate.
Furthermore, for the mask layers of the actual mask blanks, successive film formation was performed for each corresponding layer under the same conditions as the sample film formation to form a laminated film, and the composition of this laminated film was evaluated using Auger electron spectroscopy. The results are shown in FIG.

In FIG. 17, the oxygen concentration in the portion corresponding to surface layer 12c has increased due to the effects of surface oxidation. The value A shown in FIG. 16 was obtained by analyzing a molybdenum silicide compound film that was formed under the same conditions as surface layer 12c, but with a larger thickness, in order to eliminate the effects of surface oxidation.

Furthermore, a light-shielding layer 13 made of chromium was formed on the phase shift layer 12. A first resist layer 15 was formed on this mask layer and on the light-shielding layer 13. A first photoresist pattern 15P1 was formed from the first photoresist layer 15. A first light-shielding pattern 13P1 was formed by wet etching. A phase shift pattern 12P1 was formed by wet etching. This phase shift pattern 12P1 was formed. A cross section of the patterned mask layer was observed by SEM. The results are shown in Figure 18.

<Experimental Example 2>
In Experimental Example 2, a molybdenum silicide compound film having no nitrogen concentration distribution was formed on a glass substrate in the same manner as in Experimental Example 1. Similarly, a light-shielding layer containing chromium was formed to form a mask layer. This mask layer was similarly subjected to wet etching to form a similar pattern. A cross section of the patterned mask layer was observed by SEM. The results are shown in FIG. 19.

18 and 19, it can be seen that the taper of the molybdenum silicide film in Experimental Example 2 is more inclined than that in Experimental Example 1.
18 and 19, it can be seen that no overhangs are formed near the boundary between the molybdenum silicide film and the chromium film as indicated by the arrow NH in Experimental Example 2. In contrast, overhangs are formed as indicated by the arrow H in Experimental Example 1.

Furthermore, when masks are produced using these mask blanks, it is possible to achieve the effect of reducing the variation in mask line width.

10... Phase shift mask 10B... Phase shift mask blank 10L... Light transmitting region 10P... Phase shift region 11... Glass substrate (transparent substrate)
12...phase shift layer 12P1...phase shift pattern 12a...etching time shortening layer 12b...intermediate layer 12c...surface layer 13...light shielding layer 13P1...first light shielding pattern 13P2...second light shielding pattern 15...photoresist layer 15P1...first resist pattern 15P2...second resist pattern

Claims (10)

A phase shift mask blank having a mask layer that serves as a phase shift mask,
a phase shift layer made of a metal silicide laminated on a transparent substrate;
a light-shielding layer containing chromium laminated on the phase shift layer;
having
the phase shift layer contains carbon, oxygen, nitrogen, molybdenum, and silicon, and the average concentration ratio of silicon to molybdenum, Si/Mo, in the thickness direction is smaller than 2.5;
a surface layer located on a surface side away from the transparent substrate in a film thickness direction and having a nitrogen concentration of 45 atm % or more;
an intermediate layer that is closer to the transparent substrate than the surface layer in a thickness direction and has a lower nitrogen concentration than the surface layer;
an etching time shortening layer that is closer to the transparent substrate than the intermediate layer in a thickness direction and has a lower nitrogen concentration than the surface layer;
With
Etching does not form an overhang at the interface with the light-shielding layer.
A phase shift mask blank comprising: The intermediate layer has an etching rate greater than that of the surface layer.
The etching time reducing layer has an etching rate greater than that of the intermediate layer.
2. The phase shift mask blank according to claim 1. The etching rate of the intermediate layer is greater than 1.4 times the etching rate of the surface layer.
3. The phase shift mask blank according to claim 2. The etching rate of the etching time reducing layer is more than 2.5 times the etching rate of the surface layer.
3. The phase shift mask blank according to claim 2. The surface layer has a thickness of 20 nm or less.
2. The phase shift mask blank according to claim 1. The intermediate layer has an oxygen concentration of 7 atm % or less, a carbon concentration of 4 atm % or less, and a thickness of 30 nm or more.
2. The phase shift mask blank according to claim 1. The etching time shortening layer has an oxygen concentration of 7 atm% or more, a carbon concentration of 4 atm% or more, and a thickness of 30 nm or more.
2. The phase shift mask blank according to claim 1. The thickness of the phase shift layer is 135 nm to 145 nm.
2. The phase shift mask blank according to claim 1. A method for producing a phase shift mask blank according to any one of claims 1 to 8, comprising the steps of:
In forming the phase shift layer, the ratio of molybdenum to silicon is
2.2≦Si/Mo<2.5
Sputtering is performed using a target having a composition set to
2. A method for producing a phase shift mask blank comprising the steps of: Manufactured from the phase shift mask blank according to any one of claims 1 to 8.
1. A phase shift mask comprising:

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