JP7381374B2 - Mask blanks, phase shift masks, manufacturing methods - Google Patents

Description

The present invention relates to techniques suitable for use in mask blanks, phase shift masks, and manufacturing methods.

In recent years, the resolution of panels for both liquid crystal displays and organic EL displays has progressed significantly, and photomasks have also been miniaturized accordingly. Therefore, there is an increasing need for edge-enhancing phase shift masks in addition to conventionally used masks using light-shielding films.

Both line and space patterns and contact hole patterns are required to be made finer, and it has become necessary to form these fine patterns using a phase shift mask.

For example, in contact hole patterns, a large contrast is required during exposure, so a phase shift layer is formed using a silicide film such as a molybdenum silicide film, and a binary layer is formed on top of that using a metal film such as a chromium film. It is desirable to use a rim-type phase shift mask.

The phase shift layer is set to have a transmittance of 5% or 20% and a phase of 180° at, for example, i-line (wavelength: 365 nm). Therefore, it is necessary to adjust the optical constants and film thickness of the phase shift layer in advance. Therefore, when a phase shift layer is formed using a molybdenum silicide film, the molybdenum silicide film has a relatively thick film thickness of about 120 to 140 nm.

Display masks generally use wet etching for patterning. In other cases, the phase shift layer is formed using a silicide film such as a molybdenum silicide film, and an etchant (etching solution) containing hydrofluoric acid or the like is used.

Japanese Patent Application Publication No. 2018-040890

However, if the molybdenum silicide film has a relatively thick film thickness of about 120 to 140 nm, the wet etching time of the phase shift film becomes long. For this reason, when the wet etching time becomes long, the overetching time also inevitably becomes long.

Here, in order to wet-etch the molybdenum silicide film, it is necessary to use a chemical solution containing hydrofluoric acid in the etching solution. The glass substrate is etched by the etching solution.

In this way, a problem arises in that the transparent substrate such as glass is damaged during pattern formation, and the optical characteristics of the phase shift mask may deviate from a predetermined range.

Furthermore, when forming a pattern by wet etching, the cross-sectional shape of the phase shift mask becomes tapered, reducing the accuracy of the pattern shape, causing changes in the line width settings of the mask pattern, or changing the line width. It was found that problems such as increased variation occurred.

The present invention has been made in view of the above circumstances, and aims to achieve the following objects.
1. To enable manufacturing of a phase shift mask with accurately set optical characteristics.
2. To reduce the influence of etching on a substrate during pattern formation.
3. To improve the accuracy of the cross-sectional shape of a formed pattern.
4. To enable high definition of a phase shift mask.

The mask blank of the present invention is a mask blank having a layer serving as a phase shift mask,
a phase shift layer laminated on a transparent substrate;
a light shielding layer provided at a position farther from the transparent substrate than the phase shift layer;
has
The light shielding layer contains chromium,
The phase shift layer contains molybdenum silicide and carbon, and has a carbon concentration in a range of 5 atm% to 15 atm%,
In the phase shift layer, the carbon concentration at a surface close to the light shielding layer is lower than the carbon concentration at a position close to the transparent substrate,
In the phase shift layer, the carbon concentration on the surface adjacent to the light shielding layer is 20% or more lower than the carbon concentration on the surface adjacent to the transparent substrate,
The phase shift layer has a low carbon region in a position close to the light shielding layer in the thickness direction, the carbon concentration being lower than half the maximum value and the minimum value of the carbon concentration in the phase shift layer,
In the phase shift layer, the thickness of the low carbon region is relative to the thickness of the phase shift layer.
1/4 or less range
The above problem was solved by setting the
In the mask blank of the present invention, the phase shift layer may contain nitrogen and have a nitrogen concentration in a range of 30 atm % to 40 atm %.
In the mask blank of the present invention, the phase shift layer may contain oxygen and have an oxygen concentration in a range of 8 atm % to 15 atm %.
In the mask blank of the present invention, the phase shift layer may have a molybdenum concentration in a range of 20 atm % to 30 atm %.
In the mask blank of the present invention, the phase shift layer may have a silicon concentration in a range of 10 atm % to 25 atm %.
In the mask blank of the present invention, the phase shift layer has a resistivity of
It can have a range of 5.5×10 ⁻¹ Ωcm or less.
In the mask blank of the present invention, the composition ratio of molybdenum and silicon in the phase shift layer is
1≦Si/Mo
can be set to .
In the mask blank of the present invention, the phase shift layer has a film thickness of
The thickness can be set in a range of 100 nm to 200 nm .
In the mask blank of the present invention, the phase shift layer may have a concentration gradient in which the carbon concentration increases in a direction from the light shielding layer toward the transparent substrate in the film thickness direction .
The method for manufacturing mask blanks of the present invention is any of the methods for manufacturing mask blanks described above, comprising:
a phase shift layer forming step of laminating the phase shift layer containing molybdenum silicide and carbon on the transparent substrate by sputtering;
a light shielding layer forming step of laminating the light shielding layer containing chromium at a position farther from the transparent substrate than the phase shift layer;
has
In the phase shift layer forming step,
By setting the partial pressure of a carbon-containing gas as a supply gas in sputtering, the carbon concentration can be controlled in the film thickness direction.
In the method for manufacturing mask blanks of the present invention, in the phase shift layer forming step, the composition ratio of molybdenum and silicon is
2.3≦Si/Mo≦3.0
You can use a target set to .
The method for manufacturing mask blanks of the present invention includes, in the phase shift layer forming step,
By setting the partial pressure of the carbon-containing gas, the resistivity in the phase shift layer can be increased as the carbon concentration decreases.
The method for manufacturing mask blanks of the present invention includes, in the phase shift layer forming step,
By setting the partial pressure of the nitrogen-containing gas as the supply gas in sputtering, the resistivity in the phase shift layer can be increased or decreased as the nitrogen content increases or decreases.
The phase shift mask of the present invention can be manufactured from any of the mask blanks described above.
The method for manufacturing a phase shift mask of the present invention is the method for manufacturing the phase shift mask described above, comprising:
a phase shift pattern forming step of forming a pattern on the phase shift layer;
a light-shielding pattern forming step of forming a pattern on the light-shielding layer;
has
The etching solution used in the phase shift pattern forming step and the etching solution used in the light shielding pattern forming step can be different.

The mask blank of the present invention is a mask blank having a layer serving as a phase shift mask,
a phase shift layer laminated on a transparent substrate;
a light shielding layer provided at a position farther from the transparent substrate than the phase shift layer;
has
The light shielding layer contains chromium,
The phase shift layer contains molybdenum silicide and carbon, and has a carbon concentration in a range of 8 atm % to 15 atm %.
This increases the etching rate of the molybdenum silicide film that is the phase shift layer, making it possible to form a phase shift pattern by fast etching. As a result, when manufacturing a phase shift mask from a mask blank, when forming a phase shift pattern from a phase shift layer, even if a phase shift layer formed from a molybdenum silicide film is etched with an etching solution containing hydrofluoric acid, It is possible to reduce the required etching time, suppress over-etching, and reduce the influence of hydrofluoric acid etching on a transparent substrate, which is a glass substrate.

In the mask blank of the present invention, the phase shift layer contains nitrogen and has a nitrogen concentration in a range of 30 atm% to 40 atm%.
This makes it possible to form a phase shift layer with desired optical properties, and also increases the etching rate of the molybdenum silicide film, which is the phase shift layer, to form a phase shift pattern through fast etching, and to form a phase shift pattern on the glass substrate. This makes it possible to suppress the effects of etching on.

In the mask blank of the present invention, the phase shift layer contains oxygen and has an oxygen concentration in a range of 8 atm% to 15 atm%.
This makes it possible to form a phase shift layer with desired optical properties, and also increases the etching rate of the molybdenum silicide film, which is the phase shift layer, to form a phase shift pattern through fast etching, and to form a phase shift pattern on the glass substrate. This makes it possible to suppress the effects of etching on.

In the mask blank of the present invention, the phase shift layer has a molybdenum concentration in a range of 20 atm% to 30 atm%.
This makes it possible to form a phase shift layer with desired optical properties, and also increases the etching rate of the molybdenum silicide film, which is the phase shift layer, to form a phase shift pattern through fast etching, and to form a phase shift pattern on the glass substrate. This makes it possible to suppress the effects of etching on.

In the mask blank of the present invention, the phase shift layer has a silicon concentration in a range of 10 atm% to 25 atm%.
This makes it possible to form a phase shift layer with desired optical properties, and also increases the etching rate of the molybdenum silicide film, which is the phase shift layer, to form a phase shift pattern through fast etching, and to form a phase shift pattern on the glass substrate. This makes it possible to suppress the effects of etching on.

In the mask blank of the present invention, the phase shift layer has a resistivity of
It has a range of 5.5×10 ⁻¹ Ωcm or less.
This makes it possible to form a phase shift layer with desired optical properties, and also increases the etching rate of the molybdenum silicide film, which is the phase shift layer, to form a phase shift pattern through fast etching, and to form a phase shift pattern on the glass substrate. This makes it possible to suppress the effects of etching on.

In the mask blank of the present invention, the composition ratio of molybdenum and silicon in the phase shift layer is
1≦Si/Mo
is set to
This makes it possible to form a phase shift layer with desired optical properties, and also increases the etching rate of the molybdenum silicide film, which is the phase shift layer, to form a phase shift pattern through fast etching, and to form a phase shift pattern on the glass substrate. This makes it possible to suppress the effects of etching on.

In the mask blank of the present invention, the phase shift layer has a film thickness of
It is set in the range of 100 nm to 200 nm.
This makes it possible to form a phase shift layer with desired optical properties, and also increases the etching rate of the molybdenum silicide film, which is the phase shift layer, to form a phase shift pattern through fast etching, and to form a phase shift pattern on the glass substrate. This makes it possible to suppress the effects of etching on.

In the mask blank of the present invention, in the phase shift layer, the carbon concentration at a surface close to the light shielding layer is lower than the carbon concentration at a position close to the transparent substrate.
This makes it possible to form a phase shift layer with desired optical properties, and also increases the etching rate of the molybdenum silicide film, which is the phase shift layer, to form a phase shift pattern through fast etching, and to form a phase shift pattern on the glass substrate. This makes it possible to suppress the effects of etching on.

In the mask blank of the present invention, the phase shift layer has a concentration gradient in which the carbon concentration increases in a direction from the light shielding layer toward the transparent substrate in the film thickness direction.
This makes it possible to form a phase shift layer with desired optical properties, and also increases the etching rate of the molybdenum silicide film, which is the phase shift layer, to form a phase shift pattern through fast etching. It is possible to accurately form the cross-sectional shape of the phase shift pattern, which is a film.

In the mask blank of the present invention, in the phase shift layer, the carbon concentration on the surface adjacent to the light shielding layer is 20% or more lower than the carbon concentration on the surface adjacent to the transparent substrate.
This makes it possible to form a phase shift layer with desired optical properties, and also increases the etching rate of the molybdenum silicide film, which is the phase shift layer, to form a phase shift pattern through fast etching. It is possible to accurately form the cross-sectional shape of the phase shift pattern, which is a film.

In the mask blank of the present invention, the phase shift layer has a carbon concentration lower than half of the maximum and minimum carbon concentrations in the phase shift layer at a position close to the light shielding layer in the film thickness direction. It has a carbon region.
This makes it possible to form a phase shift layer with desired optical properties, and also increases the etching rate of the molybdenum silicide film, which is the phase shift layer, to form a phase shift pattern through fast etching. It is possible to accurately form the cross-sectional shape of the phase shift pattern, which is a film.

In the mask blank of the present invention, in the phase shift layer, the thickness of the low carbon region is relative to the thickness of the phase shift layer.
The range is set to 1/4 or less.
This makes it possible to form a phase shift layer with desired optical properties, and also increases the etching rate of the molybdenum silicide film, which is the phase shift layer, to form a phase shift pattern through fast etching. It is possible to accurately form the cross-sectional shape of the phase shift pattern, which is a film.

The method for manufacturing mask blanks of the present invention is any of the methods for manufacturing mask blanks described above, comprising:
a phase shift layer forming step of laminating the phase shift layer containing molybdenum silicide and carbon on the transparent substrate by sputtering;
a light shielding layer forming step of laminating the light shielding layer containing chromium at a position farther from the transparent substrate than the phase shift layer;
has
In the phase shift layer forming step,
The carbon concentration is controlled in the film thickness direction by setting the partial pressure of a carbon-containing gas as a supply gas in sputtering.
This makes it possible to form a phase shift layer having the above-mentioned composition ratio and desired optical properties, and also increases the etching rate of the molybdenum silicide film, making it possible to form a phase shift pattern through fast etching. According to the present invention, it is possible to provide a mask blank which has a phase shift layer having a phase shift layer and can accurately form a cross-sectional shape of a phase shift pattern which is a molybdenum silicide film.

In the method for manufacturing mask blanks of the present invention, in the phase shift layer forming step, the composition ratio of molybdenum and silicon is
2.3≦Si/Mo≦3.0
Use the target set to .
This makes it possible to form a phase shift layer having the above-mentioned composition ratio and desired optical properties, and also increases the etching rate of the molybdenum silicide film, making it possible to form a phase shift pattern through fast etching. According to the present invention, it is possible to provide a mask blank which has a phase shift layer having a phase shift layer and can accurately form a cross-sectional shape of a phase shift pattern which is a molybdenum silicide film.

The method for manufacturing mask blanks of the present invention includes, in the phase shift layer forming step,
By setting the partial pressure of the carbon-containing gas, the resistivity in the phase shift layer increases as the carbon concentration decreases.
This makes it possible to form a phase shift layer having the above-mentioned composition ratio and desired optical properties, and also increases the etching rate of the molybdenum silicide film, making it possible to form a phase shift pattern through fast etching. According to the present invention, it is possible to provide a mask blank which has a phase shift layer having a phase shift layer and can accurately form a cross-sectional shape of a phase shift pattern which is a molybdenum silicide film.

The method for manufacturing mask blanks of the present invention includes, in the phase shift layer forming step,
By setting the partial pressure of a nitrogen-containing gas as a supply gas in sputtering, the resistivity in the phase shift layer is increased or decreased as the nitrogen content increases or decreases.
This makes it possible to form a phase shift layer having the above-mentioned composition ratio and desired optical properties, and also increases the etching rate of the molybdenum silicide film, making it possible to form a phase shift pattern through fast etching. According to the present invention, it is possible to provide a mask blank which has a phase shift layer having a phase shift layer and can accurately form a cross-sectional shape of a phase shift pattern which is a molybdenum silicide film.

The phase shift mask of the present invention can be manufactured from any of the mask blanks described above.

The method for manufacturing a phase shift mask of the present invention is the method for manufacturing the phase shift mask described above, comprising:
a phase shift pattern forming step of forming a pattern on the phase shift layer;
a light-shielding pattern forming step of forming a pattern on the light-shielding layer;
has
The etching solution used in the phase shift pattern forming step and the etching solution used in the light shielding pattern forming step are different.
This makes it possible to form a phase shift layer having the above-mentioned composition ratio and desired optical properties, and also increases the etching rate of the molybdenum silicide film, making it possible to form a phase shift pattern through fast etching. According to the present invention, it is possible to provide a mask blank which has a phase shift layer having a phase shift layer and can accurately form a cross-sectional shape of a phase shift pattern which is a molybdenum silicide film.

According to the present invention, it is possible to use a high-density target while suppressing etching of a glass substrate, and it is possible to manufacture a product suitable for production with reduced influence of defects. It is possible to achieve the effect that the cross-sectional shape of the phase shift pattern formed by the film can be improved and high definition can be achieved.

1 is a sectional view showing a first embodiment of a mask blank according to the present invention. 1 is a cross-sectional view showing a first embodiment of a method for manufacturing mask blanks according to the present invention. 1A and 1B are process cross-sectional views showing a first embodiment of a method for manufacturing a phase shift mask according to the present invention. 1A and 1B are process cross-sectional views showing a first embodiment of a method for manufacturing a phase shift mask according to the present invention. 1A and 1B are process cross-sectional views showing a first embodiment of a method for manufacturing a phase shift mask according to the present invention. 1A and 1B are process cross-sectional views showing a first embodiment of a method for manufacturing a phase shift mask according to the present invention. 1A and 1B are process cross-sectional views showing a first embodiment of a method for manufacturing a phase shift mask according to the present invention. 1A and 1B are process cross-sectional views showing a first embodiment of a method for manufacturing 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. FIG. 1 is a schematic diagram showing a film forming apparatus in a first embodiment of a method for manufacturing mask blanks according to the present invention. It is a graph which shows the relationship between the etching rate (ER) and nitrogen concentration in the phase shift layer in the experimental example based on this invention. It is a graph which shows the Auger analysis result of the phase shift layer in the experimental example based on this invention. It is a graph which shows the Auger analysis result of the phase shift layer in the experimental example based on this invention. It is a graph showing molybdenum concentration and transmittance in a phase shift layer in an experimental example according to the present invention. It is a graph showing oxygen concentration and transmittance in a phase shift layer in an experimental example according to the present invention. It is a graph showing silicon concentration and transmittance in a phase shift layer in an experimental example according to the present invention. It is a SEM photograph which shows the phase shift layer in the experimental example based on this invention. It is a SEM photograph which shows the phase shift layer in the experimental example based on this invention.

Hereinafter, a first embodiment of a mask blank, a phase shift mask, and a manufacturing method according to the present invention will be described based on the drawings.
FIG. 1 is a cross-sectional view showing a mask blank in this embodiment, and FIG. 2 is a cross-sectional view showing a mask blank in this embodiment. In the figure, reference numeral 10B is a mask blank.

The mask blank 10B according to this embodiment is intended to be used as a phase shift mask (photomask) used when the wavelength of exposure light is in a range of about 365 nm to 436 nm.
As shown in FIG. 1, the mask blank 10B according to the present embodiment includes a glass substrate (transparent substrate) 11, a phase shift layer 12 formed on the glass substrate 11, and a phase shift layer 12 formed on the phase shift layer 12. It is composed of a light shielding layer 13.

That is, the light shielding layer 13 is provided at a position farther away from the glass substrate 11 than the phase shift layer 12 is.
These phase shift layer 12 and light shielding layer 13 constitute a mask layer which is a phase shift film that has optical properties necessary as a photomask and can change the phase of exposure light by approximately 180 degrees.

Further, in the mask blank 10B according to the present embodiment, as shown in FIG. 1, a photoresist layer 15 is formed in advance on a mask layer in which a phase shift layer 12 and a light shielding layer 13 are laminated, as shown in FIG. A structure in which a film is formed can also be used.

In addition, the mask blank 10B according to the present embodiment may have a structure in which an antireflection layer, an adhesion layer, a chemical resistant layer, a protective layer, an etching stopper layer, etc. are laminated in addition to the phase shift layer 12 and the light shielding layer 13. . Furthermore, as shown in FIG. 2, a photoresist layer 15 may be formed on these laminated films.

As the glass substrate (transparent substrate) 11, a material with excellent transparency and optical isotropy is used, and for example, a quartz glass substrate can be used. The size of the glass substrate 11 is not particularly limited, and is appropriately selected depending on the substrate to be exposed using the mask (for example, a substrate for FPD such as an LCD (liquid crystal display), a plasma display, an organic EL (electroluminescence) display, etc.). be done.

In this embodiment, as the glass substrate (transparent substrate) 11, a rectangular substrate with a side of about 100 mm to 2000 mm or more on a side can be applied, and a substrate with a thickness of 1 mm or less, a substrate with a thickness of several mm, or a substrate with a thickness of 10 mm or more can be applied. Substrates can also be used.

Further, the flatness of the glass substrate 11 may be reduced by polishing the surface of the glass substrate 11. The flatness of the glass substrate 11 can be, for example, 20 μm or less. This increases the depth of focus of the mask, making it possible to greatly contribute to the formation of fine and highly accurate patterns. Furthermore, the smaller the flatness is, 10 μm or less, the better.

The phase shift layer 12 can be a metal silicide film, for example, a film containing metals such as Ta, Ti, W, Mo, and Zr, or alloys of these metals, and silicon. In particular, it is preferable to use molybdenum silicide among metal silicides, and examples thereof include MoSi _x (X≧2) films (eg, MoSi ₂ film, MoSi ₃ film, MoSi ₄ film, etc.).

The phase shift layer 12 has optical properties set for use as a phase shift mask, such as a refractive index of about 2.4 to 3.1 and an extinction coefficient of 0.3 to 2.1 in the wavelength range of about 365 nm to 436 nm. There is a need to. Therefore, the composition and film thickness are set within predetermined ranges.
The composition ratio and film thickness in the phase shift layer 12 are not limited to the following values, which are set depending on the optical characteristics required of the phase shift mask 10 to be manufactured.

The phase shift layer 12 is preferably a molybdenum silicide film containing O (oxygen), N (nitrogen), and C (carbon).
In the phase shift layer 12, the carbon concentration (carbon content) has a range of 5 atm% to 15 atm%, the nitrogen concentration (nitrogen content) has a range of 30 atm% to 40 atm%, and the oxygen concentration (oxygen content ) has a range of 8 atm% to 15 atm%, a molybdenum concentration (molybdenum content) has a range of 20 atm% to 30 atm%, and a silicon concentration (silicon content) has a range of 10 atm% to 25 atm%. Can be set to .
The thickness of the phase shift layer 12 can be set in a range of 10 nm to 200 nm.

As for the phase shift layer 12, the composition ratio of molybdenum and silicon is set to 1≦Si/Mo.
The phase shift layer 12 has a resistivity of 5.5×10 ⁻¹ Ωcm or less.

Further, the phase shift layer 12 is set so that the carbon concentration at the surface close to the light shielding layer 13 is lower than the carbon concentration at a position close to the glass substrate 11.
The phase shift layer 12 can have a concentration gradient in which the carbon concentration increases in the direction from the light shielding layer 13 toward the glass substrate 11 in the film thickness direction.
In the phase shift layer 12, the carbon concentration at the surface adjacent to the light shielding layer 13, which is the interface, can be lower than the carbon concentration at the surface adjacent to the glass substrate 11 by 20% or more.
The phase shift layer 12 has a low carbon region 12a, which has a carbon concentration lower than a half value (intermediate value) between the maximum value and the minimum value of carbon concentration in the phase shift layer, at a position close to the light shielding layer 13 in the film thickness direction. can be formed.

The thickness of the low carbon region 12a is set to be 1/4 or less of the thickness of the phase shift layer 12.
That is, in the thickness direction of the phase shift layer 12, a low carbon region 12a having a carbon concentration lower than the half value is formed in about 1/4 of the phase shift layer 12 on the light shielding layer 13 side, and a low carbon region 12a with a carbon concentration lower than the half value is formed in about 3/4 of the phase shift layer 12 on the glass substrate 11 side. , a high carbon region 12b having a carbon concentration higher than the half value is formed. The low carbon region 12a is also a low oxygen region. The high carbon region 12b is also a high oxygen region.

The light shielding layer 13 mainly contains Cr (chromium) and O (oxygen), and further contains C (carbon) and N (nitrogen).
In this case, the light shielding layer 13 may be formed by laminating one or more selected from Cr oxides, nitrides, carbides, oxynitrides, carbonitrides, and oxycarbonitrides. can. Furthermore, the light shielding layer 13 can also have different compositions in the thickness direction. For example, the light shielding layer 13 may have a structure in which the nitrogen concentration, oxygen concentration, etc. are inclined in the film thickness direction.
The light shielding layer 13 has a thickness and a composition ratio (atm%) of Cr, N, C, O, Si, etc. so as to obtain predetermined adhesion (hydrophobicity) and predetermined optical properties, as will be described later. is set.

The film thickness of the light-shielding layer 13 is set according to the conditions required for the light-shielding layer 13, that is, film properties such as adhesion (hydrophobicity) with the photoresist layer 15 (described later) and optical properties. The film characteristics of these light shielding layers 13 change depending on the composition ratio of Cr, N, C, O, 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.
By setting the film thickness and composition of the light shielding layer 13 as described above, the adhesion with the photoresist layer 15 used for, for example, a chromium-based material is improved during patterning in photolithography, and the photoresist layer 15 is Since the etching solution does not penetrate at the interface with the substrate, a good pattern shape can be obtained and a desired pattern can be formed.

Note that if the light shielding layer 13 is not set according to the above conditions, the adhesion with the photoresist layer 15 will not be in a predetermined state and the photoresist layer 15 will peel off, causing the etching solution to enter the interface. This is not preferable because the pattern formation becomes impossible. Furthermore, if the thickness of the light shielding layer 13 is not set as described above, it may be difficult to set the optical properties of the photomask to the desired conditions, or the cross-sectional shape of the mask pattern may not be as desired. This is not preferable because there is a possibility that the condition will not be reached.

The light shielding layer 13 can reduce hydrophilicity, improve hydrophobicity, and increase adhesion by increasing the oxygen and nitrogen concentrations in the chromium compound.
At the same time, the light shielding layer 13 can be made by increasing the oxygen and nitrogen concentrations in the chromium compound to lower the refractive index and extinction coefficient, or by decreasing the oxygen and nitrogen concentrations in the chromium compound to reduce the refractive index and extinction coefficient. It is possible to increase the values of the coefficient and extinction coefficient.

In the method for manufacturing mask blanks in this embodiment, a phase shift layer 12 is formed on a glass substrate (transparent substrate) 11, and then a light shielding layer 13 is formed.

When laminating an etching stop layer, a protective layer, an adhesion layer, a chemical resistant layer, an antireflection layer, etc. in addition to the phase shift layer 12 and the light shielding layer 13, the method for manufacturing mask blanks must include a lamination step for these layers. I can do it.
An example is an adhesive layer containing chromium.

FIG. 3 is a cross-sectional view showing the manufacturing process of the mask blank and phase shift mask in this embodiment. FIG. 4 is a cross-sectional view showing the manufacturing process of the mask blank and phase shift mask in this embodiment. FIG. 5 is a cross-sectional view showing the manufacturing process of the mask blank and phase shift mask in this embodiment. FIG. 6 is a cross-sectional view showing the manufacturing process of the mask blank and phase shift mask in this embodiment. FIG. 7 is a cross-sectional view showing the manufacturing process of the mask blank and phase shift mask in this embodiment. FIG. 8 is a cross-sectional view showing the manufacturing process of the mask blank and phase shift mask in this embodiment. FIG. 9 is a cross-sectional view showing the phase shift mask in this embodiment.
As shown in FIG. 9, the phase shift mask (photomask) 10 in this embodiment has a pattern formed on a phase shift layer 12 and a light shielding layer 13 that are laminated as a mask blank 10B.

Hereinafter, a manufacturing method for manufacturing the phase shift mask 10 from the mask blank 10B of this embodiment will be explained.

As a resist pattern forming step, as shown in FIG. 2, a photoresist layer 15 is formed on the outermost surface of the mask blank 10B. Alternatively, a mask blank 10B having the photoresist layer 15 formed on the outermost surface may be prepared in advance. The photoresist layer 15 may be of positive type or negative type. The photoresist layer 15 is designed to be compatible with etching of so-called chromium-based materials and etching of molybdenum silicide-based materials. As the photoresist layer 15, a liquid resist is used.

Subsequently, by exposing and developing the photoresist layer 15, a resist pattern 15P1 is formed outside the light shielding layer 13. The resist pattern 15P1 functions as an etching mask for the phase shift layer 12 and the light shielding layer 13.

The shape of the resist pattern 15P1 is determined as appropriate depending on the etching pattern of the phase shift layer 12 and the light shielding layer 13. As an example, the shape is set to have an opening width corresponding to the opening width dimension of the transparent region 10L (see FIGS. 4 to 9) to be formed.

Next, as a light-shielding pattern forming step, the light-shielding layer 13 is wet-etched using an etching solution through the resist pattern 15P1 to form a light-shielding pattern 13P1 as shown in FIG.

As an etching solution in the light-shielding pattern forming step, an etching solution containing ceric ammonium nitrate can be used as an etching solution for a chromium-based material. For example, an etching solution containing ceric ammonium nitrate containing an acid such as nitric acid or perchloric acid Preference is given to using ammonium.
In the light-shielding pattern forming step, the phase shift layer 12 made of molybdenum silicide is hardly etched by the above-mentioned chromium-based etching solution.

Next, as a phase shift pattern forming step, the phase shift layer 12 is wet-etched using an etching solution through the light shielding pattern 13P1 and the resist pattern 15P1 to form a phase shift pattern 12P1 as shown in FIG.

The etching solution in the phase shift pattern forming step is at least one fluorine compound selected from hydrofluoric acid, hydrofluorosilicic acid, ammonium hydrogen fluoride, and is capable of etching the phase shift layer 12 made of molybdenum silicide. , hydrogen peroxide, nitric acid, and at least one oxidizing agent selected from sulfuric acid.

At this time, since the phase shift layer 12 is provided with the low carbon region 12a, the etching rate (ER) for molybdenum silicide-based etching solution becomes high, but the film thickness of the low carbon region 12a is set small. This prevents the etching time from becoming so long. Furthermore, in the phase shift layer 12, since the high carbon region 12b is set to have a high carbon concentration below the low carbon region 12a, that is, at a position close to the glass substrate 11, The etching rate (ER) is reduced, and the etching time for the entire phase shift layer 12 can be shortened.

Thereby, it becomes possible to shorten the etching time and suppress the influence on the glass substrate 11 that is affected by the above etching solution.
Thereby, as shown in FIG. 4, a light-transmitting region 10L in which the surface of the glass substrate 11 is exposed can be formed.

The molybdenum silicide compound constituting the phase shift layer 12 can be etched using, for example, a mixed solution of ammonium hydrogen fluoride and hydrogen peroxide. On the other hand, the chromium compound forming the light shielding layer 14 can be etched using, for example, a mixed solution of ceric ammonium nitrate and perchloric acid.

Therefore, the selection ratio during each wet etching becomes very large. Therefore, after forming the light shielding pattern 13P1 and the phase shift pattern 12P1 by etching, it is possible to obtain a good nearly vertical cross-sectional shape of the phase shift mask 10.

In the phase shift pattern forming step, the carbon concentration and oxygen concentration in the low carbon region 12a of the phase shift layer 12 near the light shielding layer 13 are lower than the carbon concentration and oxygen concentration in the high carbon region 12b of the phase shift layer 12 near the glass substrate 11. It is set lower than the oxygen concentration and oxygen concentration. This reduces the etching rate in the low carbon region 12a of the phase shift layer 12 near the light shielding layer 13. Therefore, in the phase shift layer 12, the progress of etching of the low carbon region 12a is delayed compared to the etching of the high carbon region 12b.

As a result, the angle (taper angle) θ that the wall surface formed by etching the light shielding pattern 13P1 and the phase shift pattern 12P1 makes with the surface of the glass substrate 11 becomes close to a right angle, and can be approximately 90°, for example.

Moreover, since the low carbon region 12a is formed in the phase shift pattern 12P1 in contact with the light shielding pattern 13P1, the adhesion between the light shielding pattern 13P1 and the phase shift pattern 12P1 is improved. Thereby, in the phase shift pattern forming step, the etching solution does not enter the interface with the light shielding pattern 13P1. Therefore, reliable pattern formation can be performed.

Furthermore, in this embodiment, as shown in FIG. 5, in the resist pattern forming step, the photoresist layer 15 is exposed and developed, so that a resist pattern 15P2 is formed on the outside of the light shielding pattern 14P1, as shown in FIG. is formed. The resist pattern 15P2 functions as an etching mask for the light shielding pattern 13P1.

The shape of the resist pattern 15P2 is determined as appropriate depending on the etching pattern with the light shielding pattern 14P1. As an example, the shape is set to have an opening width corresponding to the opening width dimensions of the exposure region 10P1 and the phase shift region 10P2 (see FIGS. 7 to 9) to be formed.

Next, as a light-shielding pattern forming step, the light-shielding pattern 13P1 is wet-etched using an etching solution through the resist pattern 15P2 to form a light-shielding pattern 13P2 as shown in FIG.
Thereby, it is possible to form a light shielding pattern 13P2 corresponding to the exposure region 10P1 and the phase shift region 10P2 in which the surface of the phase shift pattern 12P1 is exposed.

Similarly, as an etching solution in the light-shielding pattern forming step, an etching solution containing ceric ammonium nitrate can be used as an etching solution for chromium-based materials, for example, nitric acid containing an acid such as nitric acid or perchloric acid. Preferably, ceric ammonium is used.
In the light-shielding pattern forming step, the phase shift pattern 12P1 made of molybdenum silicide is hardly etched by the above-mentioned chromium-based etching solution.

At this time, since the phase shift pattern 12P1 is provided with the low carbon region 12a, the etching resistance against a chromium-based etching solution can be improved. At the same time, since the phase shift pattern 12P1 is provided with the low carbon region 12a, it is possible to improve the adhesion with the light shielding pattern 13P2 and prevent the etched shape from collapsing.

Next, as a phase shift pattern forming step, the phase shift pattern 12P1 is wet-etched using an etching solution through the resist pattern 15P2 and the light shielding pattern 13P2 to form a phase shift pattern 12P2 as shown in FIG.

The etching solution in the phase shift pattern forming step is one that can etch the phase shift pattern 12P2 made of molybdenum silicide, and includes at least one fluorine compound selected from hydrofluoric acid, hydrofluorosilicic acid, and ammonium hydrogen fluoride. , hydrogen peroxide, nitric acid, and at least one oxidizing agent selected from sulfuric acid.

At this time, since the phase shift pattern 12P1 is provided with the low carbon region 12a, the etching rate (ER) for molybdenum silicide based etching solution becomes high, but the film thickness of the low carbon region 12a is set small. This prevents the etching time from becoming so long. Furthermore, in the phase shift pattern 12P1, since the high carbon region 12b is set to have a high carbon concentration below the low carbon region 12a, that is, at a position close to the glass substrate 11, The etching rate (ER) is reduced, and the etching time for the entire phase shift pattern 12P1 can be shortened.

This makes it possible to shorten the etching time and suppress the influence of the etching liquid on the glass substrate 11 in the transparent region 10L exposed to the etching liquid.

The molybdenum silicide compound constituting the phase shift layer 12 can be etched using, for example, a mixed solution of ammonium hydrogen fluoride and hydrogen peroxide. On the other hand, the chromium compound forming the light shielding layer 14 can be etched using, for example, a mixed solution of ceric ammonium nitrate and perchloric acid.

Therefore, the selection ratio during each wet etching becomes very large. Therefore, after forming the light shielding pattern 13P1 and the phase shift pattern 12P1 by etching, it is possible to obtain a good nearly vertical cross-sectional shape of the phase shift mask 10.

In the phase shift pattern forming step, the carbon concentration and oxygen concentration in the low carbon region 12a of the phase shift layer 12 near the light shielding layer 13 are lower than the carbon concentration and oxygen concentration in the high carbon region 12b of the phase shift layer 12 near the glass substrate 11. It is set lower than the oxygen concentration and oxygen concentration. This reduces the etching rate in the low carbon region 12a of the phase shift layer 12 near the light shielding layer 13. Therefore, in the phase shift layer 12, the progress of etching of the low carbon region 12a is delayed compared to the etching of the high carbon region 12b.

At this time, since the phase shift pattern 12P1 is provided with the low carbon region 12a, the etching rate (ER) for molybdenum silicide based etching solution becomes high, but the film thickness of the low carbon region 12a is set small. This prevents the etching time from becoming so long. Furthermore, in the phase shift pattern 12P1, a high carbon region 12b with a high carbon concentration is provided below the low carbon region 12a, that is, in a position close to the glass substrate 11. The etching rate (E.R.) is reduced, and the etching time can be shortened.

This makes it possible to shorten the etching time and suppress the influence of the etching solution on the glass substrate 11 exposed in the light-transmitting region 10L.
Thereby, as shown in FIG. 8, an exposure region 10P1 in which the surface of the glass substrate 11 is exposed and a phase shift region 10P2 in which the phase shift pattern 12P2 remains and is exposed can be formed.

Next, as a resist removal step, the resist pattern 15P2 is removed to manufacture the phase shift mask 10 as shown in FIG.

Hereinafter, a method for manufacturing mask blanks in this embodiment will be described based on the drawings.

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

The manufacturing apparatus S10 shown in FIG. 10 is an inter-back type sputtering apparatus, and is connected to a load chamber S11, an unload chamber S16, and a sealing mechanism S17 to the load chamber S11, and a sealing mechanism to the unload chamber S16. It has a film forming chamber (vacuum processing chamber) S12 connected via S18.

The load chamber S11 is provided with a transport mechanism S11a that transports the glass substrate 11 carried in from the outside to the film forming chamber S12, and an exhaust mechanism S11f such as a rotary pump that roughly evacuates this chamber.

The unload chamber S16 is provided with a transport mechanism S16a that transports the glass substrate 11 on which film formation has been completed from the film formation chamber S12 to the outside, and an exhaust mechanism S16f such as a rotary pump that roughly evacuates the chamber.

The film forming chamber S12 is provided with a substrate holding mechanism S12a and two-stage film forming mechanisms S13 and S14 as mechanisms corresponding to two film forming processes.

The substrate holding mechanism S12a holds the glass substrate 11 transported by the transport mechanism S11a so as to face the targets S13b and S14b during film formation, and also transports the glass substrate 11 from the load chamber S11. and can be carried out to the unloading chamber S16.

A film forming mechanism S13 that supplies film forming material to the first stage of the two stage film forming mechanisms S13 and S14 is provided at a position on the load chamber S11 side of the film forming chamber S12.
The film forming mechanism S13 includes a cathode electrode (backing plate) S13c having a target S13b, and a power source S13d that applies a negative sputtering voltage to the backing plate S13c.

The film forming mechanism S13 includes a gas introduction mechanism S13e that mainly introduces gas near the cathode electrode (backing plate) S13c in the film forming chamber S12, and a gas introduction mechanism S13e that mainly introduces gas near the cathode electrode (backing plate) S13c in the film forming chamber S12. It has a high vacuum evacuation mechanism S13f such as a turbo molecular pump that draws a high vacuum.

Furthermore, a film forming mechanism S14 is provided at an intermediate position between the loading chamber S11 and the unloading chamber S16 in the film forming chamber S12, and supplies the film forming material to the second stage of the two stage film forming mechanisms S13 and S14. ing.
The film forming mechanism S14 includes a cathode electrode (backing plate) S14c having a target S14b, and a power source S14d that applies a negative sputtering voltage to the backing plate S14c.

The film forming mechanism S14 includes a gas introduction mechanism S14e that mainly introduces gas near the cathode electrode (backing plate) S14c in the film forming chamber S12, and a gas introduction mechanism S14e that mainly introduces gas near the cathode electrode (backing plate) S14c in the film forming chamber S12. It has a high vacuum evacuation mechanism S14f such as a turbo molecular pump that draws a high vacuum.

The film forming chamber S12 has a gas flow in the vicinity of the cathode electrodes (backing plates) S13c and S14c so that the gases supplied from the gas introduction mechanisms S13e and S14e, respectively, do not mix into the adjacent film forming mechanisms S13 and S14. A gas barrier S12g is provided to suppress this. These gas barriers S12g are configured so that the substrate holding mechanism S12a can move between adjacent film forming mechanisms S13 and S14, respectively.

In the film forming chamber S12, each of the two-stage film forming mechanisms S13 and S14 has the composition and conditions necessary to sequentially form a film on the glass substrate 11.
In this embodiment, the film forming mechanism S13 corresponds to forming the phase shift layer 12, and the film forming mechanism S14 corresponds to forming the light shielding layer 13.

Specifically, in the film forming mechanism S13, the target S13b is made of a material having molybdenum silicide as a composition necessary for forming the phase shift layer 12 on the glass substrate 11.

At the same time, in the film forming mechanism S13, a process gas containing carbon, nitrogen, oxygen, etc., as a gas supplied from the gas introduction mechanism S13e, corresponds to the film forming of the phase shift layer 12, and contains argon, nitrogen gas, etc. The conditions are set as a predetermined gas partial pressure along with the sputtering gas.
In addition, in the gas supplied in the gas introduction mechanism S13e, the partial pressure of a carbon-containing gas, an oxygen-containing gas, a nitrogen-containing gas, etc. is adjusted to a predetermined amount of change according to the thickness of the phase shift layer 12 to be formed. The structure can be adjusted to form the region 12b and the low carbon region 12a.

Further, exhaust from the high vacuum exhaust mechanism S13f is performed in accordance with the film forming conditions.
Further, in the film forming mechanism S13, the sputtering voltage applied from the power source S13d to the backing plate S13c is set corresponding to the film forming of the phase shift layer 12.

Further, in the film forming mechanism S14, the target S14b is made of a material containing chromium as a composition necessary for forming the light shielding layer 13 on the phase shift layer 12.

At the same time, in the film forming mechanism S14, as a gas supplied from the gas introduction mechanism S14e, a process gas containing carbon, nitrogen, oxygen, etc., and argon, an inert gas, etc. corresponds to the film forming of the light shielding layer 13. A predetermined gas partial pressure is set together with the sputtering gas.
Further, in the gas supplied in the gas introduction mechanism S14e, the partial pressure of the oxygen-containing gas, nitrogen-containing gas, etc. may be adjusted to a predetermined amount of change according to the thickness of the light-shielding layer 13 to be formed. It is considered a possible configuration.

Further, exhaust from the high vacuum exhaust mechanism S14f is performed in accordance with the film forming conditions.
Further, in the film forming mechanism S14, the sputtering voltage applied from the power source S14d to the backing plate S14c is set in accordance with the film forming of the light shielding layer 13.

In the manufacturing apparatus S10 shown in FIG. 10, a glass substrate 11 carried in from a load chamber S11 by a transport mechanism S11a is subjected to two-stage sputtering while being transported by a substrate holding mechanism S12a in a film forming chamber (vacuum processing chamber) S12. After the film has been formed, the glass substrate 11 on which the film has been formed is carried out from the unload chamber S16 by the transport mechanism S16a.

In the phase shift layer forming step, in the film forming mechanism S13, sputtering gas and reaction gas are supplied as supply gases from the gas introduction mechanism S13e to the vicinity of the backing plate S13c of the film forming chamber S12. In this state, a sputtering voltage is applied to the backing plate (cathode electrode) S13c from an external power source. Alternatively, a predetermined magnetic field may be formed on the target S13b by a magnetron magnetic circuit.

Ions of the sputtering gas excited by the plasma near the backing plate S13c in the film forming chamber S12 collide with the target S13b of the cathode electrode S13c, causing particles of the film forming material to fly out. Then, the ejected particles and the reaction gas are combined and then attached to the glass substrate 11, thereby forming a phase shift layer 12 with a predetermined composition on the surface of the glass substrate 11.

Similarly, in the light shielding layer forming step, in the film forming mechanism S14, sputtering gas and reaction gas are supplied as supply gases from the gas introduction mechanism S14e to the vicinity of the backing plate S14c of the film forming chamber S12. In this state, a sputtering voltage is applied to the backing plate (cathode electrode) S14c from an external power source. Alternatively, a predetermined magnetic field may be formed on the target S14b by a magnetron magnetic circuit.

Ions of the sputtering gas excited by the plasma near the backing plate S14c in the film forming chamber S12 collide with the target S14b of the cathode electrode S14c, causing particles of the film forming material to fly out. Then, the ejected particles and the reactive gas are combined and then attached to the glass substrate 11, whereby a light shielding layer 13 having a predetermined composition is laminated on the phase shift layer 12 on the surface of the glass substrate 11.

At this time, in forming the phase shift layer 12, sputtering gas, carbon-containing gas, nitrogen-containing gas, oxygen-containing gas, etc. are supplied from the gas introduction mechanism S13e to control the respective partial pressures. to keep its composition within the set range. At the same time, when the phase shift layer 12 is formed by changing the composition in the film thickness direction, the partial pressure of each gas in the atmospheric gas can be varied depending on the thickness of the film formed.
In particular, as described above, a low carbon region 12a having a low carbon concentration in the film thickness direction and a high carbon region 12b adjacent to the glass substrate 11 having a higher nitrogen carbon content than the low carbon region 12a are formed. Thus, the partial pressure ratios of carbon-containing gas, nitrogen-containing gas, etc. are controlled respectively.

Specifically, when forming a molybdenum silicide compound film, as the film thickness increases, a predetermined amount of carbon is added to a predetermined film thickness that is 3/4 of the film thickness of the phase shift layer 12. The high carbon region 12b and the low carbon region 12a can be formed by reducing the partial pressure of the carbon-containing gas from the time when the film is formed at a higher partial pressure than the partial pressure of the carbon-containing gas.
At the same time, in order to set the etching stop ability in the phase shift layer 12 to a predetermined state, the composition ratio of molybdenum and silicon in the target S13b and the composition ratio of molybdenum and other contents other than silicon are set to a predetermined state. can do. Further, it is preferable to appropriately select targets S13b having different composition ratios.

In addition, in forming the light-shielding layer 13, the gas introduction mechanism S14e supplies a nitrogen-containing gas, an oxygen-containing gas, a carbon-containing gas, etc. at a predetermined partial pressure, and switches to control the partial pressure. within the set range.

Here, examples of the oxygen-containing gas include CO ₂ (carbon dioxide), O ₂ (oxygen), N ₂ O (dinitrogen monoxide), NO (nitrogen monoxide), CO (carbon monoxide), etc. can.
Further, examples of the carbon-containing gas include CO ₂ (carbon dioxide), CH ₄ (methane), C ₂ H ₆ (ethane), and CO (carbon monoxide).
Further, examples of the nitrogen-containing gas include N ₂ (nitrogen gas), N ₂ O (dinitrogen monoxide), NO (nitrogen monoxide), N ₂ O (dinitrogen monoxide), NH ₃ (ammonia), etc. be able to.
Note that in forming the phase shift layer 12 and the light shielding layer 13, the targets S13b and S14b can be replaced as appropriate, if necessary.

Furthermore, in addition to forming the phase shift layer 12 and the light shielding layer 13, if other films are to be laminated, they may be formed by sputtering using the corresponding target, gas, etc., or by other film forming methods. The mask blank 10B of this embodiment can also be obtained by stacking the corresponding films.

Hereinafter, 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, will be explained.

A molybdenum silicide compound is formed on a glass substrate 11 for forming a mask using a sputtering method or the like to form a phase shift layer 12 . The molybdenum silicide compound formed here is preferably a film containing molybdenum, silicon, oxygen, nitrogen, carbon, etc. At this time, by controlling the composition and film thickness of molybdenum, silicon, oxygen, nitrogen, and carbon contained in the film, it is possible to form the phase shift layer 12 having desired transmittance and phase.

Subsequently, a chromium compound film that will become the light shielding layer 13 is formed using a sputtering method or the like. The chromium compound formed here is preferably a film containing chromium, oxygen, nitrogen, carbon, etc.
By forming the mask blank 10B having such a film structure, it becomes possible to form the phase shift mask 10 in which the phase shift layer 12 is formed of a molybdenum silicide compound and the light shielding layer 13 is formed of a chromium compound.

As a result of intensive studies by the present inventors, in order to form the phase shift layer 12 using a molybdenum silicide film and increase the etching rate of the phase shift layer 12, it is necessary to appropriately control the composition of the molybdenum silicide film. It turned out to be important.
When forming the phase shift mask 10 for flat displays using a molybdenum silicide film, use a target with a molybdenum to silicon ratio of 1:3 or less, and increase the nitrogen concentration in the molybdenum silicide film to 30% or more. The silicon concentration is 25% or less, the oxygen concentration is 8% or more, and the carbon concentration is 8% or more. This makes it possible to form a molybdenum silicide film that has a high etching rate and is less affected by etching of the glass substrate. Furthermore, the resistivity of the molybdenum silicide film can be 5.5×10 ⁻¹ Ωcm or less.

When using a silicide compound such as molybdenum silicide, a light shielding layer 13 made of a chromium compound is generally formed on top of the phase shift layer 12.
Therefore, by forming a chromium compound that becomes the light shielding layer 13 after forming the phase shift layer 12, it becomes possible to configure the mask blank 10B for forming the phase shift mask 10.
When forming the phase shift mask 10, the phase shift mask can be formed by forming a resist pattern and etching the mask blank after forming the mask blank 12B.

When the phase shift layer 12 is formed of a molybdenum silicide film, it is necessary to perform etching with an etching solution containing hydrofluoric acid when forming the phase shift mask 10. Therefore, in order to reduce the influence of etching on the glass substrate 11, it is desirable to use a molybdenum silicide film with the highest possible etching rate.

FIG. 11 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 having different target compositions. The results shown in the figure show that a molybdenum silicide film with a high etching rate can be formed by using a molybdenum silicide target with a low silicon content in the target composition.

Furthermore, for a molybdenum silicide target, by mixing materials of MoSi ₂ , which is a crystal of molybdenum silicon, and Si, it is possible to form a target with a desired composition ratio. 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 . Therefore, it has been found that when the silicon composition increases to a molybdenum to silicon composition ratio of 1:2.3, a target with a high relative density can be stably formed.

Therefore, by using a target in which the molybdenum silicide composition ratio is from 1:2.3 to 1:3, an etching rate that maintains a state in which etching of the glass substrate 11 is suppressed can be achieved. It is possible to use a high-density target while forming a film. Therefore, it has become possible to manufacture the mask blank 10B as a product, which is suitable for production with reduced influence of defects.

A molybdenum silicide film was formed using a target with a composition ratio of molybdenum and silicon of 1:2.3, and the flow rates of argon and nitrogen during film formation were varied to form a molybdenum silicide film.
In the manufacturing process of the phase shift mask 10, chemical solutions such as acids and alkalis are usually used in pattern formation, but it is necessary to suppress changes in transmittance during these processes.

It has been found that increasing the nitrogen concentration of the molybdenum silicide film improves its resistance to acids and alkalis.
This shows that it is important to increase the nitrogen concentration of the molybdenum silicide film in order to improve the chemical resistance.

A molybdenum silicide film was formed using a target having a composition ratio of molybdenum and silicon of 1:2.3 while varying the amount of carbon dioxide gas added.
Furthermore, the relationship between the oxygen concentration in the molybdenum silicide film and the transmittance at a wavelength of 365 nm, and the relationship between the carbon concentration in the molybdenum silicide film and the transmittance at a wavelength of 365 nm were investigated.
Here, the transmittance (%) is the transmittance of the molybdenum silicide film at a film thickness adjusted so that the phase at a wavelength of 365 nm is 180°.

These results show that increasing the oxygen concentration increases the transmittance. Here, as a phase shift mask used for a display, a phase shift mask having a transmittance of 5% or more at a phase of 180° at a wavelength of 365 nm is used.

Furthermore, the relationship between the silicon concentration, oxygen concentration, and carbon concentration in the molybdenum silicide film and the etching rate of the molybdenum silicide film was investigated by changing the gas conditions when forming the molybdenum silicide film.

From this result, it was found that the etching rate (ER) can be increased by lowering the silicon concentration and increasing the oxygen and carbon concentrations in the molybdenum silicide film.

This shows that it is important to lower the silicon concentration and increase the oxygen and carbon concentrations in the molybdenum silicide film in order to increase the etching rate of the molybdenum silicide film.
When the etching rate is faster, the required etching time is reduced when etching the molybdenum silicide film, and the amount of etching on the glass substrate is reduced, making it possible to suppress the amount of change in optical properties during the manufacture of phase shift masks. Become.

Furthermore, the relationship between the etching rate and resistivity of the molybdenum silicide film was investigated. From this result, it was found that the etching rate of the molybdenum silicide film becomes faster as the resistivity decreases.

From these results, when forming a molybdenum silicide film as a phase shift mask for flat displays, it is necessary to use a target with a molybdenum to silicon ratio of 1:3 or less and to reduce the nitrogen concentration in the molybdenum silicide film. By setting the silicon concentration to 30% or more, the silicon concentration to 25% or less, the oxygen concentration to 8% or more, and the carbon concentration to 8% or more, a molybdenum silicide film can be formed that has a fast etching rate and has little effect on etching the glass substrate. becomes possible. Furthermore, the resistivity of the molybdenum silicide film is 5.5×10 ⁻¹ Ωcm or less.

Furthermore, the relationship between the film characteristics of the phase shift layer 12 and the carbon concentration in this embodiment will be explained.

A phase shift mask using a molybdenum silicide film and having a transmittance of about 5% at the i-line (365 nm) requires the phase shift layer 12 to have a relatively thick film thickness of about 100 to 150 nm. Further, since large-area photomasks for flat displays must be processed using wet etching during pattern formation, the pattern of the phase shift mask often has a tapered shape.

For this purpose, the wet etching rate in the film thickness direction is changed by controlling the film forming conditions of the molybdenum silicide film in the film thickness direction. It has been found that this makes it possible to make the cross-sectional shape of the phase shift mask close to vertical.

Specifically, by setting the carbon concentration in the thickness direction of the molybdenum silicide film to be low on the surface of the molybdenum silicide film and increasing the interface with the glass substrate, the etching rate near the surface of the molybdenum silicide film is slowed down. It was found that it is possible to increase the etching rate near the glass substrate interface. As a result, it becomes possible to make the cross-sectional shape of the phase shift mask close to perpendicular.

Furthermore, by making the carbon concentration at the glass substrate interface 20% or more higher than the carbon concentration at the film surface, a good cross-sectional shape can be obtained.

Examples according to the present invention will be described below.

A confirmation test will be described as a specific example of the phase shift layer 12 of the molybdenum silicide film in the present invention.

<Experiment example>
As Experimental Example 1, a film of a molybdenum silicide compound is formed as a phase shift layer on a glass substrate using a sputtering method or the like. The molybdenum silicide compound film formed here is a film containing molybdenum, silicon, oxygen, nitrogen, carbon, and the like. The composition of this molybdenum silicide compound film was evaluated using Auger electron spectroscopy.

Here, in sputtering to form a film of a molybdenum silicide compound, a target having a molybdenum to silicon ratio of 1:2.3 was used.
In addition to nitrogen gas, carbon dioxide and argon were used as atmospheric gases during sputtering. In addition, films were formed while varying the partial pressure of carbon dioxide gas from 0 to 100% and the partial pressure of nitrogen gas from 0 to 100%.

Using these as Experimental Examples 1 to 5, the composition ratio in each molybdenum silicide film, the etching rate of the molybdenum silicon film, and the transmittance and resistivity (measured as sheet resistance) of this etching rate and the molybdenum silicide film were measured. .
The results are shown in Tables 1 and 2.

Experimental examples 1 and 2 shown in Table 1 are samples created for cross-sectional evaluation by setting the transmittance to about 5.2% and adjusting the characteristics as a mask layer. The etching time was actually evaluated using conditions in which the composition changed in the horizontal direction.
Furthermore, Experimental Examples 3 to 5 shown in Table 2 are molybdenum silicide films formed under the same film forming conditions. In these Experimental Examples 3 to 5, only the amount of carbon dioxide gas added during film formation was changed to investigate the relationship between the oxygen concentration, carbon concentration, and etching rate in the film.

In particular, the composition evaluation results using Auger electron spectroscopy as Experimental Example 2 are shown in FIG.
Moreover, the composition evaluation results using Auger electron spectroscopy as Experimental Example 5 are shown in FIG.

As shown in Figure 12, in Experimental Example 2, the nitrogen concentration, silicon concentration, and molybdenum concentration are almost uniform in the film thickness direction; It was confirmed that a region with high carbon concentration was formed on the right side of the figure. In this way, it can be seen that a region with a high carbon concentration is formed on the right side of the figure, which is the glass substrate side, and a region with a low carbon concentration is formed on the left side of the figure, which is the light shielding layer side.

On the other hand, as shown in FIG. 13, in Experimental Example 5, in addition to the nitrogen concentration, silicon concentration, and molybdenum concentration, the carbon concentration is almost uniform in the film thickness direction.

Further, FIG. 14 shows the relationship between molybdenum concentration and transmittance in a film of a molybdenum silicide compound.
Similarly, FIG. 15 shows the relationship between oxygen concentration and transmittance in a film of a molybdenum silicide compound.
Similarly, FIG. 16 shows the relationship between silicon concentration and transmittance in a molybdenum silicide compound film.

FIG. 17 shows an SEM image of a cross section of the molybdenum silicide film formed in Experimental Example 3 after wet etching.
The molybdenum silicide film formed in Experimental Example 5 was wet-etched, and a SEM image of a cross section thereof is shown in FIG.

These results revealed that the etching rate can be increased by increasing the carbon concentration of the molybdenum silicide film. When we investigated the relationship between the etching rate and resistivity (sheet resistance) of molybdenum silicide films, we found that the etching rate of molybdenum silicide films becomes faster when the resistivity is lowered by increasing the carbon concentration. As a result, it was found that the cross-sectional shape of the molybdenum silicide film having a gradient of carbon concentration was not tilted after etching and was good.

Furthermore, these results revealed that increasing the nitrogen concentration of the molybdenum silicide film improves chemical resistance against acids and alkalis. It has been found that a molybdenum silicide film with a high nitrogen concentration has a high etching stop function that prevents the etching solution from seeping into the interface when etching a chromium film such as a light shielding layer. It was found that the etching rate and resistivity of the molybdenum silicide film can be controlled by increasing or decreasing the nitrogen concentration.
When investigating the relationship between the etching rate and resistivity of a molybdenum silicide film with increased nitrogen concentration, it was found that the etching rate of the molybdenum silicide film becomes faster as the resistivity decreases. Furthermore, it has been found that electrostatic damage can be suppressed by using a molybdenum silicide film with low resistivity.

It can be seen that the nitrogen concentration in the molybdenum silicide film can be controlled by the nitrogen gas partial pressure during film formation. Furthermore, it is found that it is possible to form a molybdenum silicide film with even lower resistivity by sputtering using a MoSi2.3 target with a composition ratio of Si/Mo=2.3. It can be seen that this makes it possible to reduce the effects of electrostatic damage.
Furthermore, by using a laminated structure of a molybdenum silicide film with a high nitrogen concentration and a molybdenum silicide film with a low nitrogen concentration, it is possible to obtain a good cross-sectional shape and shorten the etching time, making molybdenum suitable for use in phase shift masks. It was found that it was possible to form a silicide film.

The inventors of the present application have completed the present invention through these methods. This makes it possible to form a mask with a good cross-sectional shape and less influence from etching of the glass substrate.

10...Phase shift mask 10B...Mask blank 10L...Transparent area 10P1...Exposure area 10P2...Phase shift area 11...Glass substrate (transparent substrate)
12... Phase shift layer 12P1... Phase shift pattern 12a... Low carbon region 12b... High carbon region 13... Light blocking layer 13P1, 13P2... Light blocking pattern 15... Photoresist layer 15P1, 15P2... Resist pattern

Claims (15)

A mask blank having a layer serving as a phase shift mask,
a phase shift layer laminated on a transparent substrate;
a light shielding layer provided at a position farther from the transparent substrate than the phase shift layer;
has
The light shielding layer contains chromium,
The phase shift layer contains molybdenum silicide and carbon, and has a carbon concentration in a range of 5 atm% to 15 atm%,
In the phase shift layer, the carbon concentration at a surface close to the light shielding layer is lower than the carbon concentration at a position close to the transparent substrate,
In the phase shift layer, the carbon concentration on the surface adjacent to the light shielding layer is 20% or more lower than the carbon concentration on the surface adjacent to the transparent substrate,
The phase shift layer has a low carbon region in a position close to the light shielding layer in the thickness direction, the carbon concentration being lower than half the maximum value and the minimum value of the carbon concentration in the phase shift layer,
In the phase shift layer, the thickness of the low carbon region is relative to the thickness of the phase shift layer.
1/4 or less range
Mask blanks characterized by being set to . The mask blank according to claim 1, wherein the phase shift layer contains nitrogen and has a nitrogen concentration in a range of 30 atm% to 40 atm%. The mask blank according to claim 1 or 2, wherein the phase shift layer contains oxygen and has an oxygen concentration in a range of 8 atm% to 15 atm%. 4. The mask blank according to claim 1, wherein the phase shift layer has a molybdenum concentration in a range of 20 atm% to 30 atm%. 5. The mask blank according to claim 1, wherein the phase shift layer has a silicon concentration in a range of 10 atm% to 25 atm%. In the phase shift layer, the resistivity is
The mask blank according to any one of claims 1 to 5, having a range of 5.5×10 ⁻¹ Ωcm or less. In the phase shift layer, the composition ratio of molybdenum and silicon is
1≦Si/Mo
The mask blank according to any one of claims 1 to 6, wherein the mask blank is set to . The phase shift layer has a film thickness of
The mask blank according to any one of claims 1 to 7, characterized in that the thickness is set in a range of 100 nm to 200 nm. 9. The mask blank according to claim 1 , wherein the phase shift layer has a concentration gradient in which carbon concentration increases in a direction from the light shielding layer toward the transparent substrate in the film thickness direction. A method for manufacturing a mask blank according to any one of claims 1 to 9 , comprising:
a phase shift layer forming step of laminating the phase shift layer containing molybdenum silicide and carbon on the transparent substrate by sputtering;
a light shielding layer forming step of laminating the light shielding layer containing chromium at a position farther from the transparent substrate than the phase shift layer;
has
In the phase shift layer forming step,
1. A method for manufacturing mask blanks, characterized in that carbon concentration is controlled in the film thickness direction by setting the partial pressure of a carbon-containing gas as a supply gas in sputtering. In the phase shift layer forming step, the composition ratio of molybdenum and silicon is
2.3≦Si/Mo≦3.0
11. The method for manufacturing mask blanks according to claim 10 , characterized in that a target set to a target is used. In the phase shift layer forming step,
12. The method for manufacturing mask blanks according to claim 10, wherein the resistivity of the phase shift layer is increased as the carbon concentration decreases by setting the partial pressure of the carbon-containing gas. In the phase shift layer forming step,
13. The production of mask blanks according to claim 12 , wherein the resistivity in the phase shift layer is increased or decreased as the nitrogen content increases or decreases by setting the partial pressure of a nitrogen-containing gas as a supply gas in sputtering. Method. A phase shift mask manufactured from the mask blank according to any one of claims 1 to 9 . A method for manufacturing a phase shift mask according to claim 14 , comprising:
a phase shift pattern forming step of forming a pattern on the phase shift layer;
a light-shielding pattern forming step of forming a pattern on the light-shielding layer;
has
A method for manufacturing a phase shift mask, characterized in that an etching solution used in the phase shift pattern forming step and an etching solution used in the light shielding pattern forming step are different.

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