JP2021148826A - Mask blank, phase shift mask, and production method - Google Patents

Abstract

To provide a phase shift mask that is excellent in the accuracy of optical properties and can achieve improved accuracy of a pattern shape.SOLUTION: A mask blank 10B has a layer to be a phase shift mask 10, the mask blank having a phase shift layer 12 put on a transparent substrate 11, and a light-blocking layer 13 at a position more remote from the transparent substrate than the phase shift layer. The light-blocking layer has chromium, the phase shift layer has molybdenum silicide and carbon, and the carbon level is from 5 atm% to 15 atm%.SELECTED DRAWING: Figure 1

Description

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

In recent years, the miniaturization of panels for both liquid crystal displays and organic EL displays has greatly progressed, and along with this, the miniaturization of photomasks has also progressed. Therefore, there is an increasing need for an edge-enhanced phase-shift mask as well as a mask using a light-shielding film that has been conventionally used.

Both the line-and-space pattern and the contact hole pattern are required to be miniaturized, and it is becoming necessary to form these fine patterns using a phase shift mask.

For example, in a contact hole pattern, a large contrast is required during exposure, so a phase shift layer is formed with a silicide film such as a molybdenum silicide film, and a binary layer is formed on the phase shift layer with 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 so that the transmittance is 5% or 20% and the phase is 180 ° on the i-line (wavelength 365 nm), for example. Therefore, it is necessary to adjust the optical constant and the film thickness of the phase shift layer in advance. Therefore, when the phase shift layer is formed using the molybdenum silicide film, the film thickness of the molybdenum silicide film is relatively thick, about 120 to 140 nm.

A mask for a display generally uses wet etching at the time of patterning. A phase shift layer is formed of a silicide film such as a molybdenum silicide film, and in other cases, an etchant (etching solution) containing hydrofluoric acid or the like is used.

JP-A-2018-040890

However, if the film thickness of the molybdenum silicide film is relatively thick, such as about 120 to 140 nm, the wet etching time of the phase shift film wolf becomes long. Therefore, when the wet etching time becomes long, the over-etching time inevitably becomes long.

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

As described above, there is a problem that the transparent substrate such as glass is damaged at the time of pattern formation, and the optical characteristics of the phase shift mask may deviate from a predetermined range.

Further, when the pattern is formed by wet etching, the accuracy of the pattern shape is lowered, such as the cross-sectional shape of the phase shift mask becoming tapered, and the set value of the line width of the mask pattern changes, or the line width is changed. It was found that problems such as large variations occur.

The present invention has been made in view of the above circumstances, and an object of the present invention is to achieve the following objects.
1. 1. To enable the manufacture of phase shift masks with accurate optical characteristics.
2. To reduce the influence of etching on the substrate in pattern formation.
3. 3. To improve the accuracy of the cross-sectional shape in the formed pattern.
4. To enable high definition of the phase shift mask.

The mask blanks of the present invention are mask blanks having a layer serving as a phase shift mask.
The phase shift layer laminated on the transparent substrate and
A light-shielding layer provided at a position farther from the transparent substrate than the phase shift layer,
Have,
The light-shielding layer contains chromium and
The above problem was solved by the phase shift layer containing molybdenum silicide and carbon and having a carbon concentration in the range of 5 atm% to 15 atm%.
In the mask blanks of the present invention, the phase shift layer contains nitrogen and the nitrogen concentration can be in the range of 30 atm% to 40 atm%.
In the mask blanks of the present invention, the phase shift layer contains oxygen, and the oxygen concentration can be in the range of 8 atm% to 15 atm%.
The mask blanks of the present invention can have a molybdenum concentration in the range of 20 atm% to 30 atm% in the phase shift layer.
The mask blanks of the present invention can have a silicon concentration in the range of 10 atm% to 25 atm% in the phase shift layer.
The mask blanks of the present invention have a resistivity in the phase shift layer.
It can have a range of 5.5 × 10 ^{-1 Ωcm or less.}
The mask blanks of the present invention have a composition ratio of molybdenum and silicon in the phase shift layer.
1 ≤ Si / Mo
Can be set to.
In the mask blanks of the present invention, the phase shift layer has a film thickness.
It can be set in the range of 100 nm to 200 nm.
In the mask blanks of the present invention, in the phase shift layer, the carbon concentration on the surface close to the light-shielding layer can be lower than the carbon concentration at the position close to the transparent substrate.
The mask blanks of the present invention can have a concentration gradient in the phase shift layer in which the carbon concentration increases in the direction from the light-shielding layer to the transparent substrate in the film thickness direction.
In the mask blanks of the present invention, in the phase shift layer, the carbon concentration on the surface close to the light-shielding layer can be 20% or more lower than the carbon concentration on the surface close to the transparent substrate.
In the mask blanks of the present invention, the phase shift layer has a carbon concentration lower than half the maximum and minimum values of the carbon concentration in the phase shift layer at a position close to the light shielding layer in the film thickness direction. It can have a carbon region.
In the mask blanks of the present invention, in the phase shift layer, the film thickness of the low carbon region is larger than the film thickness of the phase shift layer.
It can be set in the range of 1/4 or less.
The method for producing a mask blank of the present invention is the method for producing a mask blank according to any one of the above.
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 separated from the transparent substrate by the phase shift layer, and a light-shielding layer forming step.
Have,
In the phase shift layer forming step,
By setting the partial pressure of the carbon-containing gas as the supply gas in sputtering, the carbon concentration can be controlled in the film thickness direction to form the gas.
In the method for producing mask blanks of the present invention, the composition ratio of molybdenum and silicon in the phase shift layer forming step is determined.
2.3 ≤ Si / Mo ≤ 3.0
The target set in can be used.
The method for producing mask blanks of the present invention is 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 producing mask blanks of the present invention is 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 the mask blanks described in any of the above.
The method for manufacturing a phase shift mask of the present invention is the above-mentioned method for manufacturing a phase shift mask.
A phase shift pattern forming step of forming a pattern on the phase shift layer and
A light-shielding pattern forming step of forming a pattern on the light-shielding layer,
Have,
The etching solution in the phase shift pattern forming step and the etching solution in the light-shielding pattern forming step can be different.

The mask blanks of the present invention are mask blanks having a layer serving as a phase shift mask.
The phase shift layer laminated on the transparent substrate and
A light-shielding layer provided at a position farther from the transparent substrate than the phase shift layer,
Have,
The light-shielding layer contains chromium and
The phase shift layer contains molybdenum silicide and carbon, and has a carbon concentration in the range of 8 atm% to 15 atm%.
As a result, the etching rate in the molybdenum silicide film which is the phase shift layer can be increased, and the phase shift pattern can be formed by fast etching. As a result, in the production of the phase shift mask from the mask blanks, when the phase shift pattern is formed from the phase shift layer, even when the phase shift layer formed from the molybdenum silicide film is etched by the etching solution containing hydrofluoric acid, even when the phase shift layer is etched. It is possible to shorten the required etching time, suppress over-etching, and reduce the influence of etching with hydrofluoric acid on a transparent substrate which is a glass substrate.

In the mask blanks of the present invention, the phase shift layer contains nitrogen and the nitrogen concentration ranges from 30 atm% to 40 atm%.
This makes it possible to form a phase shift layer having desired optical characteristics, increase the etching rate in the molybdenum silicide film which is the phase shift layer, form a phase shift pattern by fast etching, and form a glass substrate. It becomes possible to suppress the influence of etching in.

In the mask blanks of the present invention, the phase shift layer contains oxygen and the oxygen concentration ranges from 8 atm% to 15 atm%.
This makes it possible to form a phase shift layer having desired optical characteristics, increase the etching rate in the molybdenum silicide film which is the phase shift layer, form a phase shift pattern by fast etching, and form a glass substrate. It becomes possible to suppress the influence of etching in.

The mask blanks of the present invention have a molybdenum concentration in the range of 20 atm% to 30 atm% in the phase shift layer.
This makes it possible to form a phase shift layer having desired optical characteristics, increase the etching rate in the molybdenum silicide film which is the phase shift layer, form a phase shift pattern by fast etching, and form a glass substrate. It becomes possible to suppress the influence of etching in.

The mask blanks of the present invention have a silicon concentration in the range of 10 atm% to 25 atm% in the phase shift layer.
This makes it possible to form a phase shift layer having desired optical characteristics, increase the etching rate in the molybdenum silicide film which is the phase shift layer, form a phase shift pattern by fast etching, and form a glass substrate. It becomes possible to suppress the influence of etching in.

The mask blanks of the present invention have a resistivity in the phase shift layer.
It has a range of 5.5 × 10 ^{-1 Ωcm or less.}
This makes it possible to form a phase shift layer having desired optical characteristics, increase the etching rate in the molybdenum silicide film which is the phase shift layer, form a phase shift pattern by fast etching, and form a glass substrate. It becomes possible to suppress the influence of etching in.

The mask blanks of the present invention have a composition ratio of molybdenum and silicon in the phase shift layer.
1 ≤ Si / Mo
Is set to.
This makes it possible to form a phase shift layer having desired optical characteristics, increase the etching rate in the molybdenum silicide film which is the phase shift layer, form a phase shift pattern by fast etching, and form a glass substrate. It becomes possible to suppress the influence of etching in.

In the mask blanks of the present invention, the phase shift layer has a film thickness.
It is set in the range of 100 nm to 200 nm.
This makes it possible to form a phase shift layer having desired optical characteristics, increase the etching rate in the molybdenum silicide film which is the phase shift layer, form a phase shift pattern by fast etching, and form a glass substrate. It becomes possible to suppress the influence of etching in.

In the mask blanks of the present invention, in the phase shift layer, the carbon concentration on the surface close to the light-shielding layer is lower than the carbon concentration at the position close to the transparent substrate.
This makes it possible to form a phase shift layer having desired optical characteristics, increase the etching rate in the molybdenum silicide film which is the phase shift layer, form a phase shift pattern by fast etching, and form a glass substrate. It becomes possible to suppress the influence of etching in.

The mask blanks of the present invention have a concentration gradient in the phase shift layer in which the carbon concentration increases in the direction from the light-shielding layer to the transparent substrate in the film thickness direction.
This makes it possible to form a phase shift layer having desired optical characteristics, increase the etching rate of the molybdenum silicide film which is the phase shift layer, and form a phase shift pattern by fast etching to form a phase shift pattern. It is possible to accurately form the cross-sectional shape of the phase shift pattern, which is a film.

In the mask blanks of the present invention, in the phase shift layer, the carbon concentration on the surface close to the light-shielding layer is 20% or more lower than the carbon concentration on the surface close to the transparent substrate.
This makes it possible to form a phase shift layer having desired optical characteristics, increase the etching rate of the molybdenum silicide film which is the phase shift layer, and form a phase shift pattern by fast etching to form a phase shift pattern. It is possible to accurately form the cross-sectional shape of the phase shift pattern, which is a film.

In the mask blanks of the present invention, the phase shift layer has a carbon concentration lower than half the maximum and minimum values of the carbon concentration 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 having desired optical characteristics, increase the etching rate of the molybdenum silicide film which is the phase shift layer, and form a phase shift pattern by fast etching to form a phase shift pattern. It is possible to accurately form the cross-sectional shape of the phase shift pattern, which is a film.

In the mask blanks of the present invention, in the phase shift layer, the film thickness of the low carbon region is larger than the film thickness of the phase shift layer.
It is set in the range of 1/4 or less.
This makes it possible to form a phase shift layer having desired optical characteristics, increase the etching rate of the molybdenum silicide film which is the phase shift layer, and form a phase shift pattern by fast etching to form a phase shift pattern. It is possible to accurately form the cross-sectional shape of the phase shift pattern, which is a film.

The method for producing a mask blank of the present invention is the method for producing a mask blank according to any one of the above.
A phase shift layer forming step of laminating the phase shift layer containing molybdenum silicide and carbon on the transparent substrate by sputtering, and
A light-shielding layer forming step of laminating the light-shielding layer containing chromium at a position separated from the transparent substrate by the phase shift layer, and a light-shielding layer forming step.
Have,
In the phase shift layer forming step,
As the supply gas in sputtering, the carbon concentration is controlled in the film thickness direction by setting the partial pressure of the carbon-containing gas.
This makes it possible to form a phase shift layer having the above-mentioned composition ratio and having desired optical characteristics, and it is possible to increase the etching rate in the molybdenum silicide film and form a phase shift pattern by fast etching. It is possible to provide mask blanks which have 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 producing mask blanks of the present invention, the composition ratio of molybdenum and silicon in the phase shift layer forming step is determined.
2.3 ≤ Si / Mo ≤ 3.0
Use the target set in.
As a result, it is possible to form a phase shift layer having the above-mentioned composition ratio and having desired optical characteristics, and it is possible to increase the etching rate in the molybdenum silicide film and form a phase shift pattern by fast etching. It is possible to provide mask blanks which have 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 producing mask blanks of the present invention is in the phase shift layer forming step.
By setting the partial pressure of the carbon-containing gas, the resistivity in the phase shift layer is increased as the carbon concentration decreases.
As a result, it is possible to form a phase shift layer having the above-mentioned composition ratio and having desired optical characteristics, and it is possible to increase the etching rate in the molybdenum silicide film and form a phase shift pattern by fast etching. It is possible to provide mask blanks which have 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 producing mask blanks of the present invention is 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 is increased or decreased as the nitrogen content is increased or decreased.
This makes it possible to form a phase shift layer having the above-mentioned composition ratio and having desired optical characteristics, and it is possible to increase the etching rate in the molybdenum silicide film and form a phase shift pattern by fast etching. It is possible to provide mask blanks which have 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 the mask blanks described in any of the above.

The method for manufacturing a phase shift mask of the present invention is the above-mentioned method for manufacturing a phase shift mask.
A phase shift pattern forming step of forming a pattern on the phase shift layer and
A light-shielding pattern forming step of forming a pattern on the light-shielding layer,
Have,
The etching solution in the phase shift pattern forming step and the etching solution 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 having desired optical characteristics, and it is possible to increase the etching rate in the molybdenum silicide film and form a phase shift pattern by fast etching. It is possible to provide mask blanks which have 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 effects of defects, and molybdenum silicide. It is possible to achieve the effect that the cross-sectional shape of the phase shift pattern formed by the film can be improved to enable high definition.

It is sectional drawing which shows 1st Embodiment of the mask blanks which concerns on this invention. It is sectional drawing which shows 1st Embodiment of the manufacturing method of the mask blanks which concerns on this invention. It is a process sectional view which shows 1st Embodiment of the manufacturing method of the phase shift mask which concerns on this invention. It is a process sectional view which shows 1st Embodiment of the manufacturing method of the phase shift mask which concerns on this invention. It is a process sectional view which shows 1st Embodiment of the manufacturing method of the phase shift mask which concerns on this invention. It is a process sectional view which shows 1st Embodiment of the manufacturing method of the phase shift mask which concerns on this invention. It is a process sectional view which shows 1st Embodiment of the manufacturing method of the phase shift mask which concerns on this invention. It is a process sectional view which shows 1st Embodiment of the manufacturing method of the phase shift mask which concerns on this invention. It is sectional drawing which shows 1st Embodiment of the phase shift mask which concerns on this invention. It is a schematic diagram which shows the film forming apparatus in 1st Embodiment of the manufacturing method of the mask blanks which concerns on this invention. It is a graph which shows the relationship between the etching rate (ER) in the phase shift layer and nitrogen concentration in the experimental example which concerns on this invention. It is a graph which shows the Auger analysis result in the phase shift layer in the experimental example which concerns on this invention. It is a graph which shows the Auger analysis result in the phase shift layer in the experimental example which concerns on this invention. It is a graph which shows the molybdenum concentration and the transmittance in the phase shift layer in the experimental example which concerns on this invention. It is a graph which shows the oxygen concentration and the transmittance in the phase shift layer in the experimental example which concerns on this invention. It is a graph which shows the silicon concentration and the transmittance in the phase shift layer in the experimental example which concerns on this invention. It is an SEM photograph which shows the phase shift layer in the experimental example which concerns on this invention. It is an SEM photograph which shows the phase shift layer in the experimental example which concerns on this invention.

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

The mask blanks 10B according to the present embodiment are used for a phase shift mask (photomask) used in a wavelength range of the exposure light of about 365 nm to 436 nm.
As shown in FIG. 1, the mask blanks 10B according to the present embodiment are formed on a glass substrate (transparent substrate) 11, a phase shift layer 12 formed on the glass substrate 11, and a 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 from the glass substrate 11 than the phase shift layer 12.
The phase shift layer 12 and the light shielding layer 13 form a mask layer which is a phase shift film having optical characteristics necessary for a photomask and capable of changing the phase of exposure light by approximately 180 °.

Further, in the mask blanks 10B according to the present embodiment, as shown in FIG. 1, the photoresist layer 15 is previously provided with respect to the mask layer in which the phase shift layer 12 and the light shielding layer 13 are laminated, as shown in FIG. It is also possible to have a film-formed structure.

The mask blank 10B according to the present embodiment may have a configuration in which an antireflection layer, an adhesion layer, a chemical resistant layer, a protective layer, an etching stopper layer, and the like are laminated in addition to the phase shift layer 12 and the light shielding layer 13. .. Further, 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 having excellent transparency and optical isotropic properties 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 according to the substrate to be exposed using the mask (for example, an FPD substrate such as an LCD (liquid crystal display), a plasma display, or an organic EL (electroluminescence) display). Will be done.

In the present embodiment, as the glass substrate (transparent substrate) 11, a rectangular substrate having a side of about 100 mm to a side of 2000 mm or more can be applied, and further, a substrate having a thickness of 1 mm or less, a substrate having a thickness of several mm, or a thickness of 10 mm or more. A substrate 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. As a result, the depth of focus of the mask becomes deeper, and it becomes possible to greatly contribute to the formation of fine and highly accurate patterns. Further, the flatness is as small as 10 μm or less, which is 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 an alloy of these metals and silicon. In particular, it is preferable to use molybdenum silicide among the metal silicides, and _{examples thereof include MoSi X} (X ≧ 2) films (for example, MoSi ₂ films, MoSi ₃ films, MoSi ₄ films, etc.).

The phase shift layer 12 sets optical characteristics when used 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 a wavelength range of about 365 nm to 436 nm. There is a need to. Therefore, the composition and the film thickness are set in a predetermined range.
The composition ratio and film thickness of the phase shift layer 12 are not limited to the following values set by the optical characteristics required for 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 film thickness of the phase shift layer 12 can be set in the range of 10 nm to 200 nm.

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 in ^{the range of 5.5 × 10 -1} Ωcm or less.

Further, the phase shift layer 12 is set so that the carbon concentration on the surface close to the light-shielding layer 13 is lower than the carbon concentration at the 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 on the surface close to the light-shielding layer 13 can be 20% or more lower than the carbon concentration on the surface close to the glass substrate 11.
The phase shift layer 12 has a low carbon region 12a at a position close to the light shielding layer 13 in the film thickness direction, which has a carbon concentration lower than the half value (intermediate value) of the maximum and minimum carbon concentrations in the phase shift layer. Can be formed.

The film thickness of the low carbon region 12a is set in the range of 1/4 or less with respect to the film thickness of the phase shift layer 12.
That is, in the film thickness direction of the phase shift layer 12, a low carbon region 12a having a carbon concentration lower than the half value is formed at about 1/4 of the light shielding layer 13 side, and about 3/4 of the glass substrate 11 side. , A high carbon region 12b having a carbon concentration higher than the above 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 contains Cr (chromium) and O (oxygen) as main components, and further contains C (carbon) and N (nitrogen).
In this case, as the light-shielding layer 13, one or two or more selected from Cr oxides, nitrides, carbides, oxide nitrides, carbides and oxide carbides may be laminated. can. Further, the light-shielding layer 13 may have different compositions in the thickness direction. For example, as the light-shielding layer 13, a configuration in which the nitrogen concentration, the oxygen concentration, or the like is inclined in the film thickness direction can be exemplified.
As will be described later, the light-shielding layer 13 has a predetermined adhesion (hydrophobicity), a thickness thereof so as to obtain a predetermined optical characteristic, and a composition ratio (atm%) of Cr, N, C, O, Si and the like. 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 characteristics such as adhesion (hydrophobicity) to the photoresist layer 15 and optical characteristics described later. The film characteristics of these light-shielding layers 13 change depending on the composition ratio of Cr, N, C, O and the like. The film thickness of the light-shielding layer 13 can be set particularly according to the optical characteristics required for the phase shift mask 10.
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 a chromium system, for example, is improved at the time of pattern formation in the photolithography method, and the photoresist layer 15 is formed. Since the infiltration of the etching solution does not occur at the interface with, a good pattern shape can be obtained and a desired pattern can be formed.

If the light-shielding layer 13 is not set as in the above conditions, the photoresist layer 15 is peeled off without the adhesion to the photoresist layer 15 being in a predetermined state, and the etching solution invades the interface. This is not preferable because pattern formation cannot be performed. Further, when the film thickness of the light-shielding layer 13 is not set as in the above conditions, it becomes difficult to set the optical characteristics of the photomask to desired conditions, or the cross-sectional shape of the mask pattern is desired. It is not preferable because it may not be in the state of.

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

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

The mask blank manufacturing method includes, in the case of 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, these laminating steps. Can be done.
As an example, an adhesion layer containing chromium can be mentioned.

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

Hereinafter, a manufacturing method for manufacturing the phase shift mask 10 from the mask blanks 10B of the present embodiment will be described.

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

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

The shape of the resist pattern 15P1 is appropriately determined according to 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 translucent 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 through the resist pattern 15P1 with an etching solution to form the light-shielding pattern 13P1 as shown in FIG.

As the etching solution in the light-shielding pattern forming step, an etching solution containing diammonium cerium nitrate can be used as the etching solution for the chromium-based material. For example, the second cerium nitrate containing an acid such as nitric acid or perchloric acid can be used. It is preferable to use 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 through the light-shielding pattern 13P1 and the resist pattern 15P1 with an etching solution to form the phase shift pattern 12P1 as shown in FIG.

As the etching solution in the phase shift pattern forming step, the phase shift layer 12 made of molybdenum silicide can be etched, and the etching solution is composed of at least one fluorine compound selected from hydrofluoric acid, silicate hydrofluoric acid, and ammonium hydrogen fluoride. , It is preferable to use one containing at least one oxidizing agent selected from hydrogen peroxide, nitric acid and sulfuric acid.

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

This makes it possible to shorten the etching time and suppress the influence of the etching solution on the glass substrate 11.
As a result, as shown in FIG. 4, it is possible to form the translucent region 10L in which the surface of the glass substrate 11 is exposed.

The molybdenum silicide compound constituting the phase shift layer 12 can be etched with, 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 with, for example, a mixed solution of dicerium ammonium nitrate and perchloric acid.

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

Further, 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 close to the light shielding layer 13 are the carbon in the high carbon region 12b of the phase shift layer 12 close to the glass substrate 11. It is set lower than the concentration and oxygen concentration. As a result, the etching rate in the low carbon region 12a of the phase shift layer 12 close to the light shielding layer 13 becomes low. Therefore, in the phase shift layer 12, the progress of etching in the low carbon region 12a is delayed as compared with the etching in the high carbon region 12b.

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

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. As a result, in the phase shift pattern forming step, the etching solution does not infiltrate the interface with the light-shielding pattern 13P1. Therefore, reliable pattern formation can be performed.

Further, in the present embodiment, as a resist pattern forming step, as shown in FIG. 5, the photoresist layer 15 is exposed and developed, so that the resist pattern 15P2 is outside the light-shielding pattern 14P1 as shown in FIG. Is formed. The resist pattern 15P2 functions as an etching mask with the light-shielding pattern 13P1.

The shape of the resist pattern 15P2 is appropriately determined according to the etching pattern with the light-shielding pattern 14P1. As an example, the shape is set to have an aperture width corresponding to the aperture width dimension 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 through the resist pattern 15P2 with an etching solution to form the light-shielding pattern 13P2 as shown in FIG.
As a result, the light-shielding pattern 13P2 corresponding to the exposed region 10P1 and the phase shift region 10P2 where the surface of the phase shift pattern 12P1 is exposed can be formed.

Similarly, as the etching solution in the light-shielding pattern forming step, an etching solution containing cerium nitrate diammonium nitrate can be used as the etching solution for the chromium-based material, and for example, nitric acid containing an acid such as nitric acid or perchloric acid. It is preferable to use diammonium cerium.
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 to the 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 to 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 through the resist pattern 15P2 and the light-shielding pattern 13P2 with an etching solution to form the phase shift pattern 12P2 as shown in FIG.

As the etching solution in the phase shift pattern forming step, the phase shift pattern 12P2 made of molybdenum silicide can be etched with at least one fluorine compound selected from hydrofluoric acid, silicate hydrofluoric acid, and ammonium hydrogen fluoride. , It is preferable to use one containing at least one oxidizing agent selected from hydrogen peroxide, nitric acid and sulfuric acid.

At this time, since the phase shift pattern 12P1 is provided with the low carbon region 12a, the etching rate (ER) with respect to the molybdenum silicide-based etching solution is high, but the film thickness of the low carbon region 12a is set small. Therefore, it is possible to prevent the etching time from becoming so long. Further, in the phase shift pattern 12P1, 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, so that the molybdenum silicide-based etching solution is used. The etching rate (ER) is reduced, and the etching time can be shortened for the entire phase shift pattern 12P1.

This makes it possible to shorten the etching time and suppress the influence of the etching solution on the glass substrate 11 in the light-transmitting region 10L exposed to the etching solution.

The molybdenum silicide compound constituting the phase shift layer 12 can be etched with, 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 with, for example, a mixed solution of dicerium ammonium nitrate and perchloric acid.

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

Further, 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 close to the light shielding layer 13 are the carbon in the high carbon region 12b of the phase shift layer 12 close to the glass substrate 11. It is set lower than the concentration and oxygen concentration. As a result, the etching rate in the low carbon region 12a of the phase shift layer 12 close to the light shielding layer 13 becomes low. Therefore, in the phase shift layer 12, the progress of etching in the low carbon region 12a is delayed as compared with the etching in 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) with respect to the molybdenum silicide-based etching solution is high, but the film thickness of the low carbon region 12a is set small. Therefore, it is possible to prevent the etching time from becoming so long. Further, in the phase shift pattern 12P1, a high carbon region 12b having a high carbon concentration is provided below the low carbon region 12a, that is, at a position close to the glass substrate 11, so that the molybdenum silicide-based etching solution is provided. The etching rate (ER) 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 translucent region 10L.
As a result, as shown in FIG. 8, an exposed 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 are exposed can be formed.

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

Hereinafter, the method for manufacturing the mask blanks in the present embodiment will be described with reference to the drawings.

FIG. 10 is a schematic view showing a mask blank manufacturing apparatus according to the present embodiment.
The mask blanks 10B in this embodiment are manufactured by the manufacturing apparatus shown in FIG.

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

The load chamber S11 is provided with a transport mechanism S11a for transporting 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 draws a rough vacuum in the chamber.

The unload chamber S16 is provided with a transport mechanism S16a for transporting the glass substrate 11 having been film-formed from the film-forming chamber S12 to the outside, and an exhaust mechanism S16f such as a rotary pump that draws a rough vacuum in 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 the two film forming processes.

The substrate holding mechanism S12a holds the glass substrate 11 conveyed by the conveying mechanism S11a so as to face the targets S13b and S14b during film formation, and carries the glass substrate 11 from the loading chamber S11. And it can be carried out to the unload room S16.

At the position on the load chamber S11 side of the film forming chamber S12, a film forming mechanism S13 for supplying the first-stage film forming material among the two-stage film forming mechanisms S13 and S14 is provided.
The film forming mechanism S13 includes a cathode electrode (backing plate) S13c having a target S13b, and a power supply S13d for applying a negative potential sputtering voltage to the backing plate S13c.

The film forming mechanism S13 focuses on the gas introduction mechanism S13e that mainly introduces gas into the vicinity of the cathode electrode (backing plate) S13c in the film forming chamber S12 and the vicinity of the cathode electrode (backing plate) S13c in the film forming chamber S12. It has a high vacuum exhaust mechanism S13f such as a turbo molecular pump that draws a high vacuum.

Further, at an intermediate position between the load chamber S11 and the unload chamber S16 in the film formation chamber S12, a film formation mechanism S14 for supplying the second-stage film-forming material among the two-stage film-forming mechanisms S13 and S14 is provided. ing.
The film forming mechanism S14 includes a cathode electrode (backing plate) S14c having a target S14b, and a power supply S14d for applying a negative potential sputtering voltage to the backing plate S14c.

The film forming mechanism S14 focuses on the gas introduction mechanism S14e that mainly introduces gas into the vicinity of the cathode electrode (backing plate) S14c in the film forming chamber S12 and the vicinity of the cathode electrode (backing plate) S14c in the film forming chamber S12. It has a high vacuum exhaust mechanism S14f such as a turbo molecular pump that draws a high vacuum.

In the film forming chamber S12, gas flows in the vicinity of the cathode electrodes (backing plates) S13c and S14c so that the gas supplied from the gas introduction mechanisms S13e and S14e does not mix with the adjacent film forming mechanisms S13 and S14, respectively. A gas barrier S12g is provided to suppress the above. These gas barriers S12g are configured so that the substrate holding mechanism S12a can move between the film forming mechanisms S13 and S14 adjacent to each other.

In the film forming chamber S12, the two-stage film forming mechanisms S13 and S14 have the composition and conditions necessary for sequentially forming a film on the glass substrate 11.
In the present embodiment, the film forming mechanism S13 corresponds to the film formation of the phase shift layer 12, and the film forming mechanism S14 corresponds to the film formation of 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, as the gas supplied from the gas introduction mechanism S13e, the process gas contains carbon, nitrogen, oxygen, etc., corresponding to the film formation of the phase shift layer 12, and argon, nitrogen gas, etc. Conditions are set as a predetermined gas partial pressure together with the sputter gas of.
Further, in the gas supplied by the gas introduction mechanism S13e, the partial pressure of the gas such as carbon-containing gas, oxygen-containing gas, nitrogen-containing gas, etc. is set to a predetermined amount of change according to the film thickness of the phase shift layer 12 to be formed, and the carbon content is high. The configuration can be adjusted so as to form the region 12b and the low carbon region 12a, respectively.

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

Further, in the film forming mechanism S14, the target S14b is made of a material having 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 the gas supplied from the gas introduction mechanism S14e, the process gas contains carbon, nitrogen, oxygen and the like corresponding to the film formation of the light shielding layer 13, argon, an inert gas and the like. It is set as a predetermined gas partial pressure together with the sputter gas of.
Further, in the gas supplied by the gas introduction mechanism S14e, the partial pressures of gases such as oxygen-containing gas and nitrogen-containing gas can be adjusted so as to have a predetermined amount of change according to the film thickness of the light-shielding layer 13 to be formed. It is a possible configuration.

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

In the manufacturing apparatus S10 shown in FIG. 10, the glass substrate 11 carried in from the load chamber S11 by the conveying mechanism S11a is subjected to two-stage sputtering while being conveyed by the substrate holding mechanism S12a in the film forming chamber (vacuum processing chamber) S12. After the film is formed, the glass substrate 11 having been formed into a film 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, the sputter gas and the reaction gas are supplied as supply gas 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. Further, a predetermined magnetic field may be formed on the target S13b by the magnetron magnetic circuit.

Sputter gas ions excited by plasma near the backing plate S13c in the film forming chamber S12 collide with the target S13b of the cathode electrode S13c to eject particles of the film forming material. Then, after the ejected particles and the reaction gas are combined and then adhered to the glass substrate 11, the phase shift layer 12 is formed on the surface of the glass substrate 11 with a predetermined composition.

Similarly, in the light-shielding layer forming step, in the film forming mechanism S14, the sputter gas and the reaction gas are supplied as supply gas 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. Further, a predetermined magnetic field may be formed on the target S14b by the magnetron magnetic circuit.

Sputter gas ions excited by plasma near the backing plate S14c in the film forming chamber S12 collide with the target S14b of the cathode electrode S14c to eject particles of the film forming material. Then, after the ejected particles and the reaction gas are combined and then adhered to the glass substrate 11, the light-shielding layer 13 is laminated on the surface of the glass substrate 11 with a predetermined composition and formed on the phase shift layer 12.

At this time, in the film formation of the phase shift layer 12, sputter gas, carbon-containing gas, nitrogen-containing gas, oxygen-containing gas, etc., which have a predetermined partial pressure, are supplied from the gas introduction mechanism S13e to control the respective partial pressures. Switch to and keep the 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 individual gas partial pressures in the atmospheric gas can be changed according to the film thickness 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 close to the other glass substrate 11 having a higher carbon dioxide content than the low carbon region 12a are formed. As described above, the partial pressure ratios of the carbon-containing gas, the nitrogen-containing gas, etc. are controlled respectively.

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

Further, in the film formation of the light-shielding layer 13, the gas introduction mechanism S14e supplies a nitrogen-containing gas, an oxygen-containing gas, a carbon-containing gas, etc., which have a predetermined partial pressure, and switches to control the partial pressure, and the composition thereof. Within the set range.

Here, examples of the oxygen-containing gas include CO ₂ (carbon dioxide), O ₂ (oxygen), N ₂ O (nitrous oxide), NO (nitric oxide), CO (carbon monoxide) and the like. can.
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 (nitrous oxide), NO (nitric oxide), N ₂ O (nitrous oxide), NH ₃ (ammonia) and the like. be able to.
In the film formation of the phase shift layer 12 and the light shielding layer 13, the targets S13b and S14b can be replaced as appropriate if necessary.

Further, in addition to the film formation of the phase shift layer 12 and the light-shielding layer 13, when another film is laminated, the film formation is performed by sputtering as the sputtering conditions of the corresponding target, gas, etc., or by another film formation method. The corresponding films can also be laminated to form the mask blanks 10B of the present embodiment.

Hereinafter, the film characteristics of the phase shift layer 12 and the light shielding layer 13 in the present embodiment, particularly the film characteristics of the phase shift layer will be described.

A molybdenum silicide compound is formed on the glass substrate 11 for forming the mask by a sputtering method or the like to form the phase shift layer 12. The molybdenum silicide compound formed here is preferably a film containing molybdenum, silicon, oxygen, nitrogen, carbon and the like. 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 a desired transmittance and phase.

Subsequently, a chromium compound film to be the light-shielding layer 13 is formed by a sputtering method or the like. The chromium compound formed here is preferably a film containing chromium, oxygen, nitrogen, carbon and the like.
By forming the mask blanks 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 the molybdenum silicide compound and the light shielding layer 13 is formed of the chromium compound.

As a result of diligent studies by the present inventors, in order to form the phase shift layer 12 using the molybdenum silicide film and increase the etching rate of the phase shift layer 12, it is possible to appropriately control the composition of the molybdenum silicide film. It turned out to be important.
When the phase shift mask 10 for a flat display is formed using a molybdenum silicide film, a target having a molybdenum to silicon ratio of 1: 3 or less is used, and the nitrogen concentration in the molybdenum silicide film is 30% or more. The silicon concentration should be 25% or less, the oxygen concentration should be 8% or more, and the carbon concentration should be 8% or more. This makes it possible to form a molybdenum silicide film having a high etching rate and being less affected by etching of the glass substrate. Further, the resistivity of the molybdenum silicide film ^{can be 5.5 × 10 -1} Ωcm or less.

When a silicide compound such as molybdenum silicide is used, it is common to form a light-shielding layer 13 formed of a chromium compound on the top of the phase shift layer 12.
Therefore, by forming the chromiumnium compound to be the light-shielding layer 13 after the phase shift layer 12 is formed, it is possible to form the mask blanks 10B for forming the phase shift mask 10.
When forming the phase shift mask 10, the phase shift mask can be formed by forming the resist pattern and etching the mask blanks after forming the mask blanks 12B.

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

FIG. 11 shows the relationship between the nitrogen concentration in the film and the etching rate when a molybdenum silicide film is formed by using molybdenum silicide targets having different target compositions. From the results shown in the figure, it can be seen that a molybdenum silicide film having a high etching rate can be formed by using a molybdenum silicide target having a low silicon composition in the target composition.

Further, as for the target of molybdenum silicide, it is possible to form a target having a desired composition ratio by mixing the materials of _{MoSi 2 and Si, which are crystals of molybdenum silicon.} For that purpose, it is difficult to form a target having a stable composition unless a certain amount of silicon is _{present in excess of MoSi 2.} Therefore, it was found that when the composition ratio of molybdenum and silicon increases to 1: 2.3, a target having a high relative density can be stably formed.

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

A molybdenum silicide film was formed using a target having a composition ratio of molybdenum and silicon of 1: 2.3, and a molybdenum silicide film was formed by changing the flow rates of argon and nitrogen at the time of film formation.
As a manufacturing process of the phase shift mask 10, a chemical solution such as an acid or an alkali is usually used in pattern formation, but it is necessary to suppress a change in transmittance during these processes.

It was found that increasing the nitrogen concentration of the molybdenum silicide film improves the resistance of the chemical solution to acids and alkalis.
From this, it can be seen that it is important to increase the nitrogen concentration of the molybdenum silicide film in order to enhance the chemical resistance.

When a molybdenum silicide film was formed using a target having a composition ratio of molybdenum and silicon of 1: 2.3, the amount of carbon dioxide gas added was changed to form the film.
Further, 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 °.

From these results, it can be seen that the transmittance increases by increasing the oxygen concentration. Here, as the phase shift mask used for the 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) was increased by lowering the silicon concentration in the molybdenum silicide film and increasing the oxygen concentration and the carbon concentration.

From this, it can be seen that it is important to lower the silicon concentration in the molybdenum silicide film and increase the oxygen concentration and the carbon concentration in order to increase the etching rate of the molybdenum silicide film.
When the etching rate is increased, the etching time required for etching the molybdenum silicide film is reduced, and the etching amount for the glass substrate is reduced. Therefore, it is possible to suppress the amount of change in the optical characteristics in the production of the phase shift mask. Become.

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

From these results, when a molybdenum silicide film is used as a phase shift mask for a flat display, a target having a molybdenum to silicon ratio of 1: 3 or less is used to determine 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 having a high etching rate and less influence on etching to a glass substrate can be formed. Becomes possible. Further, the resistivity of the molybdenum silicide film is 5.5 × 10 ^-1 Ωcm or less.

Further, the relationship between the film characteristics of the phase shift layer 12 and the carbon concentration in the present embodiment will be described.

A phase shift mask having a transmittance of about 5% on i-line (365 nm) using a molybdenum silicide film requires the phase shift layer 12 to have a relatively thick film thickness of about 100 to 150 nm. Further, in a large-area photomask for a flat display, since it is necessary to process it by using wet etching at the time of pattern formation, the pattern of the phase shift mask often has a tapered shape.

Therefore, 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 was found that this makes it possible to bring the cross-sectional shape of the phase shift mask closer to vertical.

Specifically, the carbon concentration in the film thickness direction of the molybdenum silicide film is set low on the surface of the molybdenum silicide film and the interface of the glass substrate is set high, so that the etching rate near the surface of the molybdenum silicide film is slowed down. It was found that the etching rate near the interface of the glass substrate can be increased. As a result, the cross-sectional shape of the phase shift mask can be made closer to vertical.

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

Hereinafter, examples of the present invention will be described.

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.

<Experimental example>
As Experimental Example 1, a film of a molybdenum silicide compound is formed on a glass substrate as a phase shift layer by 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 the sputtering for forming a film of the molybdenum silicide compound, a target having a ratio of molybdenum to silicon of 1: 2.3 was used.
As the atmospheric gas in sputtering, carbon dioxide and argon were used in addition to nitrogen gas. Further, the carbon dioxide gas partial pressure was changed from 0 to 100%, and the nitrogen gas partial pressure was changed from 0 to 100% to form a film.

Using these as Experimental Examples 1 to 5, the composition ratio of each molybdenum silicide film, the etching rate of the molybdenum silicon film, and the etching rate 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 Example 1 and Experimental Example 2 shown in Table 1 are samples prepared for cross-sectional evaluation by setting the transmittance to be about 5.2% and actually adjusting the characteristics as a mask layer. The etching time was actually evaluated while using the condition that the composition changed in the vertical direction.
Further, Experimental Examples 3 to 5 shown in Table 2 are all 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 at the time of film formation was changed, and the relationship between the oxygen concentration in the film, the carbon concentration, and the etching rate was investigated.

In particular, FIG. 12 shows the composition evaluation results using Auger electron spectroscopy as Experimental Example 2.
In addition, the composition evaluation result is shown in FIG. 13 using Auger electron spectroscopy as Experimental Example 5.

As shown in FIG. 12, in Experimental Example 2, the nitrogen concentration, silicon concentration, and molybdenum concentration are substantially uniform in the film thickness direction, whereas in Experimental Example 2, the carbon concentration is on the left side of the figure. It was confirmed that a region with a high carbon concentration was formed on the right side of the figure. As described above, it can be seen that the region having a high carbon concentration is formed on the right side of the figure on the glass substrate side, and the region having a low carbon concentration is formed on the left side of the figure on the light-shielding layer side.

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

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

FIG. 17 shows an SEM image obtained by wet-etching the molybdenum silicide film formed in Experimental Example 3 and photographing the cross section thereof.
FIG. 18 shows an SEM image obtained by wet-etching the molybdenum silicide film formed in Experimental Example 5 and photographing the cross section thereof.

From these results, it was found that the etching rate was increased by increasing the carbon concentration of the molybdenum silicide film. As a result of investigating the relationship between the etching rate of the molybdenum silicide film and the resistivity (sheet resistance), it was found that the etching rate of the molybdenum silicide film becomes faster when the carbon concentration is increased and the resistivity is lowered. As a result, it was found that the molybdenum silicide film having an inclined carbon concentration did not incline the cross-sectional shape after etching and was good.

Furthermore, from these results, it was found that increasing the nitrogen concentration of the molybdenum silicide film improves the chemical resistance to acids and alkalis. It was found that the molybdenum silicide film having a high nitrogen concentration has a high etching stop function with less penetration of the etching solution 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.
As a result of investigating the relationship between the etching rate of the molybdenum silicide film having an increased nitrogen concentration and the resistivity, it was found that the etching rate of the molybdenum silicide film increased as the resistivity decreased. Furthermore, it was also found that electrostatic breakdown can be suppressed by using a molybdenum silicide film having a low resistivity.

It can be seen that the nitrogen concentration in the molybdenum silicide film can be controlled by the partial pressure of nitrogen gas at the time of film formation. Further, it can be seen that a molybdenum silicide film having a lower resistivity can be formed by sputtering using a MoSi2.3 target having a composition ratio of Si / Mo = 2.3. From this, it can be seen that the influence of electrostatic breakdown can be reduced.
Further, by using a laminated structure of a molybdenum silicide film having a high nitrogen concentration and a molybdenum silicide film having a low nitrogen concentration, the cross-sectional shape is good and the etching time can be shortened, and molybdenum suitable for use in a phase shift mask. It was found that a silicide film can be formed.

The inventors of the present application have completed the present invention by these means. This makes it possible to form a mask having a good cross-sectional shape with little influence from etching of the glass substrate.

10 ... Phase shift mask 10B ... Mask blanks 10L ... Translucent 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-shielding layer 13P1, 13P2 ... Light-shielding pattern 15 ... Photoresist layer 15P1, 15P2 ... Resist pattern

Claims (19)

A mask blank having a layer that serves as a phase shift mask.
The phase shift layer laminated on the transparent substrate and
A light-shielding layer provided at a position farther from the transparent substrate than the phase shift layer,
Have,
The light-shielding layer contains chromium and
A mask blank in which the phase shift layer contains molybdenum silicide and carbon and has a carbon concentration in the range of 5 atm% to 15 atm%. The mask blank according to claim 1, wherein the phase shift layer contains nitrogen and the nitrogen concentration ranges from 30 atm% to 40 atm%. The mask blank according to claim 1 or 2, wherein the phase shift layer contains oxygen and the oxygen concentration ranges from 8 atm% to 15 atm%. The mask blank according to any one of claims 1 to 3, wherein the phase shift layer has a molybdenum concentration in the range of 20 atm% to 30 atm%. The mask blank according to any one of claims 1 to 4, wherein the phase shift layer has a silicon concentration in the range of 10 atm% to 25 atm%. In the phase shift layer, the resistivity is
5. The mask blank according to any one of claims 1 to 5, wherein the mask blank has 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 thickness of the phase shift layer is
The mask blank according to any one of claims 1 to 7, wherein the mask blank is set in the range of 100 nm to 200 nm. The mask blank according to any one of claims 1 to 8, wherein in the phase shift layer, the carbon concentration on the surface close to the light-shielding layer is lower than the carbon concentration at the position close to the transparent substrate. The mask blank according to claim 9, wherein the phase shift layer has a concentration gradient in which the carbon concentration increases in the direction from the light-shielding layer to the transparent substrate in the film thickness direction. The mask blank according to claim 9 or 10, wherein in the phase shift layer, the carbon concentration of the surface close to the light-shielding layer is 20% or more lower than the carbon concentration of the surface close to the transparent substrate. The phase shift layer is characterized by having a low carbon region having a carbon concentration lower than half of the maximum and minimum values of the carbon concentration in the phase shift layer at a position close to the light shielding layer in the film thickness direction. The mask blanks according to claim 11. In the phase shift layer, the film thickness of the low carbon region is relative to the film thickness of the phase shift layer.
The mask blanks according to claim 12, wherein the mask blanks are set in a range of 1/4 or less. The method for producing a mask blank according to any one of claims 1 to 13.
A phase shift layer forming step of laminating the phase shift layer containing molybdenum silicide and carbon on the transparent substrate by sputtering, and
A light-shielding layer forming step of laminating the light-shielding layer containing chromium at a position separated from the transparent substrate by the phase shift layer, and a light-shielding layer forming step.
Have,
In the phase shift layer forming step,
A method for producing mask blanks, which comprises controlling the carbon concentration in the film thickness direction by setting a 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
The method for manufacturing a mask blank according to claim 14, wherein the target set in the above is used. In the phase shift layer forming step,
The method for producing a mask blank according to claim 14 or 15, wherein the resistivity in 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,
The production of the mask blank according to claim 16, wherein the resistivity in the phase shift layer is increased or decreased as the nitrogen content is increased or decreased by setting the partial pressure of the nitrogen-containing gas as the supply gas in sputtering. Method. A phase shift mask manufactured from the mask blank according to any one of claims 1 to 13. The method for manufacturing a phase shift mask according to claim 18.
A phase shift pattern forming step of forming a pattern on the phase shift layer and
A light-shielding pattern forming step of forming a pattern on the light-shielding layer,
Have,
A method for manufacturing a phase shift mask, characterized in that the etching solution in the phase shift pattern forming step and the etching solution in the light shielding pattern forming step are different.

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