JP7166975B2 - Photomask blank, photomask manufacturing method, and display device manufacturing method - Google Patents

Description

The present invention relates to mask blanks and photomasks, and more particularly to mask blanks (photomask blanks) for manufacturing FPD devices, photomasks (transfer masks) manufactured using such mask blanks, and the like.

In the field of FPD masks, attempts have been made to reduce the number of masks by using a gray-tone mask (also referred to as a multi-tone mask) having a semi-transparent film (so-called half-transparent film for gray-tone mask). (Non-Patent Document 1).
Here, as shown in FIG. 11(1), the gray-tone mask has a light-shielding portion 1, a transmitting portion 2, and a gray-tone portion 3 on a transparent substrate (translucent substrate). The gray-tone part 3 has a function of adjusting the amount of transmission. For example, as shown in FIG. By reducing the amount of light transmitted through these regions and reducing the amount of radiation through these regions, the reduced film thickness of the photoresist corresponding to such regions after development is reduced to a desired value. It is formed for the purpose of controlling

When a gray-tone mask is mounted on a large-scale exposure apparatus using a mirror projection method or a lens method, the amount of exposure light passing through the gray-tone portion 3 becomes insufficient as a whole. The positive photoresist exposed through 3 remains on the substrate only by thinning the film. In other words, the difference in the amount of light exposure causes a difference in the solubility of the resist in the developing solution between the portion corresponding to the normal light-shielding portion 1 and the portion corresponding to the gray-tone portion 3. Therefore, the shape of the resist after development is as shown in FIG. ), the portion 1′ corresponding to the normal light shielding portion 1 is, for example, about 1 μm, the portion 3′ corresponding to the gray tone portion 3 is, for example, about 0.4 to 0.5 μm, and the portion corresponding to the transmission portion 2 is about 1 μm. becomes a portion 2' where there is no resist. Then, the substrate to be processed is subjected to the first etching in the resist-free portion 2', the resist in the thin portion 3' corresponding to the gray tone portion 3 is removed by ashing or the like, and the second etching is performed in this portion. , the number of masks is reduced by performing the same process as two conventional masks with one mask.
Recently, the above gray-tone mask is installed in a large-scale exposure apparatus of the proximity exposure (projection exposure) method and used for forming photospacers for color filters.

The gray-tone mask shown in FIG. 11(1) is manufactured using a mask blank described in Patent Document 1, for example. The mask blank described in Patent Document 1 has at least a semi-transparent film having a function of adjusting the amount of transmission on a translucent substrate, and the semi-transparent film emits light from an ultra-high pressure mercury lamp. The transmissivity of the translucent film is controlled to be less than 5% in at least the wavelength band from the i-line to the g-line. As the semi-transparent film, specifically, materials such as CrN (film thickness 20 to 250 angstroms (2 to 25 nm), MoSi ₄ (film thickness 15 to 200 angstroms (1.5 to 20 nm)) and film thickness are selected. exemplified.

Monthly FPD Intelligence, p.31-35, May 1999

Japanese Patent Application Laid-Open No. 2007-199700

When forming a semi-translucent film having a desired transmittance using the materials exemplified in Patent Document 1, the film thickness of the semi-translucent film is controlled. When a large gray-tone mask is manufactured, a transmittance distribution occurs due to a film thickness distribution in the substrate plane, and it is becoming difficult to manufacture a gray-tone mask with good in-plane transmittance uniformity.
In addition, in the film formation process of the semi-transparent film in the mask blank, the film is formed according to the designed film thickness. It is difficult to form a film, and a film thickness difference of about 10% may occur with respect to the designed film thickness. If the semi-translucent film is designed without considering the fluctuation range of the transmittance due to the thickness, as described above, when the thickness of the semi-translucent film deviates from the design value, the transmittance There was a problem of changing

In particular, when a gray-tone mask is installed in a large proximity exposure type exposure apparatus and a pattern is transferred onto an object to be transferred, the distance between the gray-tone mask and the object to be transferred is small, so the surface of the gray-tone mask becomes A pellicle that prevents foreign matter from adhering cannot be used. Therefore, after using the gray-tone mask for a number of times, chemical cleaning using alkali or acid is usually performed to remove foreign matter adhering to the surface of the gray-tone mask. film reduction occurs, and the transmittance of the semitransparent film changes.

Therefore, the present invention relates to a photomask blank and a photomask for manufacturing an FPD device having at least a semi-transparent film having a function of adjusting the amount of transmission on a translucent substrate, and a film of the semi-translucent film An object of the present invention is to provide a photomask blank and a photomask having a semi-transparent film with a small change in transmittance with respect to a change in thickness.

Various aspects of the invention are described below.
(Configuration 1)
A photomask blank for manufacturing an FPD device having at least a semitransparent film having a function of adjusting the amount of transmission on a translucent substrate,
the semitransparent film is made of a transition metal silicide-based material containing a transition metal, silicon, and any of oxygen and nitrogen, or a chromium-based material containing chromium and any of oxygen and nitrogen;
The semi-translucent film has a transmittance of 10% or more and 60% or less and a phase difference of 0 degree or more and 120 degrees or less with respect to exposure light, and the film thickness of the semi-translucent film is the transmittance and When the set film thickness for obtaining the phase difference fluctuates in the range of ±3 nm, the transmittance at the exposure wavelength can be controlled so that the fluctuation range is within ±2%,
A photomask blank characterized by selecting a material for a semitransparent film having a refractive index n and an extinction coefficient k so as to obtain the above characteristics.

(Configuration 2)
The photomask blank according to Structure 1, wherein the semitransparent film has a thickness of 40 nm or more and 120 nm or less.
(Composition 3)
When the semi-translucent film fluctuates within a range of ±3 nm with respect to the set film thickness for obtaining the transmittance and phase difference, the rear surface 3. The photomask blank of construction 1 or 2, wherein the reflectance tends to decrease.

(Composition 4)
4. The photomask blank according to any one of Structures 1 to 3, further comprising a light shielding film on the semitransparent film.
(Composition 5)
The photomask blank according to any one of Structures 1 to 3, further comprising a light-shielding film pattern between the light-transmitting substrate and the semi-light-transmitting film.

(Composition 6)
A method for manufacturing a photomask using the photomask blank according to any one of Structures 1 to 5.
(Composition 7)
A display device manufacturing method for manufacturing a display device by transferring the pattern of the photomask according to Structure 6.

According to the photomask blank of the present invention, it is possible to provide a photomask blank having a semi-transparent film that can control the change in transmittance to be small with respect to the film thickness variation of the semi-transparent film.
Further, according to the method of manufacturing a photomask of the present invention, it is possible to provide a photomask having a semi-transparent film pattern that can control the change in transmittance to be small with respect to the film thickness variation of the semi-transparent film.
Further, according to the manufacturing method of the display device of the present invention, it is possible to provide a display device in which the CD error of pattern transfer due to the photomask does not occur.

FIG. 2 is a schematic diagram showing a film configuration of a photomask blank according to Embodiment 1-1; FIG. 2 is a schematic diagram showing a film structure of a photomask blank according to Embodiment 1-2; FIG. 3 is a schematic diagram showing the film structure of a photomask blank according to Embodiment 1-3; In Experimental Example 1-1, the transmittance of the semi-transparent film when the film thickness of the semi-transparent film is changed with respect to the set film thickness at which the transmittance of the semi-transparent film is 40%, It is a figure which shows the characteristic of a phase difference and a back surface reflectance. In Experimental Example 1-2, the transmittance of the semi-translucent film when the thickness of the semi-translucent film is changed with respect to the set film thickness at which the transmittance of the semi-translucent film is 40%, It is a figure which shows the characteristic of a phase difference and a back surface reflectance. In Experimental Example 1-3, the transmittance of the semi-translucent film when the thickness of the semi-translucent film is changed with respect to the set film thickness at which the transmittance of the semi-translucent film is 40%, It is a figure which shows the characteristic of a phase difference and a back surface reflectance. In Experimental Example 1-3, the transmittance of the semi-transparent film when the film thickness of the semi-transparent film is changed with respect to the set film thickness at which the transmittance of the semi-transparent film is 30%, It is a figure which shows the characteristic of a phase difference and a back surface reflectance. In Experimental Example 1-1, the transmittance of the semi-transparent film when the film thickness of the semi-transparent film is changed with respect to the set film thickness at which the transmittance of the semi-transparent film is 30%, It is a figure which shows the characteristic of a phase difference and a back surface reflectance. In Experimental Example 3-1, the transmittance of the semi-transparent film when the film thickness of the semi-transparent film is changed with respect to the set film thickness at which the transmittance of the semi-transparent film is 30%, It is a figure which shows the characteristic of a phase difference and a back surface reflectance. In Experimental Example 3-2, the transmittance of the semi-transparent film when the film thickness of the semi-transparent film is changed with respect to the set film thickness at which the transmittance of the semi-transparent film is 30%, It is a figure which shows the characteristic of a phase difference and a back surface reflectance. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the gray-tone mask which has a translucent film|membrane, (1) is a partial top view, (2) is a partial sectional view.

Embodiment 1 (Embodiments 1-1, 1-2, 1-3)
In Embodiment 1, a photomask blank having a translucent substrate and a semi-translucent film having a function of adjusting the amount of transmission will be described.
FIG. 1 is a schematic diagram showing the film structure of a photomask blank 10 according to Embodiment 1-1.
A photomask blank 10 shown in FIG. 1 includes a translucent substrate 20 and a semi-translucent film 30 formed on the translucent substrate 20 .

FIG. 2 is a schematic diagram showing the film structure of the photomask blank 10 according to the embodiment 1-2.
The photomask blank 10 shown in FIG. 2 is a photomask blank provided with a light-shielding film 40 on a semi-translucent film 30 in the photomask blank of the above-described embodiment 1-1.

FIG. 3 is a schematic diagram showing the film structure of the photomask blank 10 according to the embodiment 1-3.
The photomask blank 10 shown in FIG. 3 is the same as the photomask blank of the above-described embodiment 1-1, but a light-shielding film 40 is formed in a predetermined pattern by etching between the light-transmitting substrate 20 and the semi-light-transmitting film 30. It is a photomask blank provided with a formed light shielding film pattern 40a.

The translucent substrate 20, the semi-translucent film 30, the light shielding film 40 and the etching stopper film, which constitute the photomask blanks 10 of Embodiments 1-1 to 1-3, will be described below.

[Translucent substrate 20]
The translucent substrate 20 is transparent to exposure light. The translucent substrate 20 has a transmittance of 85% or more, preferably 90% or more, with respect to exposure light, assuming that there is no surface reflection loss. The translucent substrate 20 is made of a material containing silicon and oxygen, and is made of a glass material such as synthetic quartz glass, quartz glass, aluminosilicate glass, soda lime glass, low thermal expansion glass (SiO ₂ —TiO ₂ glass, etc.). can do. When the translucent substrate 20 is made of low thermal expansion glass, it is possible to suppress the positional change of the phase shift film pattern due to the thermal deformation of the translucent substrate 20 . Further, the translucent substrate 20 used for the display device is generally a rectangular substrate, and the length of the short side of the translucent substrate is 300 mm or more. According to the present invention, even if the length of the short side of the light-transmitting substrate is as large as 300 mm or more, a semi-transmissive film is formed that can control the transmittance change to be small with respect to the film thickness change of the semi-transparent film. It is a photomask blank.

[Semi-translucent film 30]
The semitransparent film 30 is composed of a transition metal, silicon, a transition metal silicide-based material containing either oxygen or nitrogen, or a chromium-based material containing chromium and either oxygen or nitrogen. Molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), zirconium (Zr) and the like are suitable as the transition metal in the transition metal silicide-based material.

In addition, the semitransparent film 30 contains either oxygen or nitrogen in order to adjust the optical characteristics (transmittance, transmittance characteristics with respect to film thickness change, phase difference) of the exposure light.
Nitrogen in the semitransparent film 30 has the effect of not lowering the refractive index and the extinction coefficient compared to oxygen, which is also a light element component. Therefore, the effect of reducing the film thickness of the semi-translucent film 30 can be obtained. The nitrogen content in the semitransparent film 30 is preferably 20 atomic % or more and 60 atomic % or less.
Oxygen in the semitransparent film 30 has the effect of lowering the refractive index and the extinction coefficient compared to nitrogen, which is also a light element component. Therefore, the semitransparent film 30 can be adjusted to obtain a desired transmittance. However, if too much oxygen is added to the semi-translucent film 30, the etching characteristics of the pattern are such that the interface with the translucent substrate is likely to be eroded. When the semitransparent film 30 contains oxygen, the oxygen content is preferably more than 0 atomic % and 30 atomic % or less.
In addition to oxygen and nitrogen described above, the semitransparent film 30 may contain rare gases such as carbon, helium, krypton, and xenon for the purpose of reducing film stress and controlling the wet etching rate. good.

Examples of transition metal silicide-based materials include nitrides of transition metal silicides, oxides of transition metal silicides, oxynitrides of transition metal silicides, and oxynitride carbides of transition metal silicides. In addition, when the transition metal silicide-based material is a molybdenum silicide-based material (MoSi-based material), a zirconium silicide-based material (ZrSi-based material), or a molybdenum zirconium silicide-based material (MoZrSi-based material), an excellent pattern cross section can be obtained by wet etching. A molybdenum silicide-based material (MoSi-based material) is particularly preferable because it is easy to obtain a shape.

The atomic ratio of the transition metal and silicon contained in the semitransparent film 30 is preferably transition metal:silicon=1:3 or more and 1:15 or less. Within this range, the washing resistance (chemical resistance) of the semitransparent film 30 can be enhanced. From the viewpoint of further improving washing resistance, the atomic ratio of the transition metal and silicon contained in the semitransparent film 30 is transition metal: silicon = 1:4 or more and 1:15 or less, more preferably transition metal: silicon = 1:5 or more and 1:15 or less is desirable.

Examples of chromium-based materials include chromium nitrides, chromium oxides, chromium oxynitrides, chromium oxycarbides, chromium oxynitrides, and chromium oxynitride carbides.

The transmittance of the semi-transparent film 30 with respect to exposure light satisfies the required value for the semi-transparent film 30 . Transmittance of the semitransparent film 30 is 10% or more and 60% or less, more preferably 20% or more and 60%, with respect to light of a predetermined wavelength (hereinafter referred to as representative wavelength) contained in the exposure light. or less, more preferably 30% or more and 50% or less. That is, when the exposure light is compound light including light in the wavelength range of 313 nm or more and 436 nm or less, the semi-transparent film 30 has the above-described transmittance with respect to the light of the representative wavelength included in the wavelength range. . For example, when the exposure light is compound light including i-line, h-line and g-line, the semi-transparent film 30 is i-line (wavelength: 365 nm), h-line (wavelength: 405 nm) and g-line (wavelength: 436 nm) has the above-mentioned transmittance.

In addition, the phase difference of the semitransparent film 30 is 0 degrees or more and 120 degrees or less, more preferably 0 degrees or more, with respect to light of a predetermined wavelength (hereinafter referred to as representative wavelength) contained in the exposure light. 110 degrees or less, more preferably 0 degrees or more and 100 degrees or less, more preferably 0 degrees or more and 90 degrees or less. That is, when the exposure light is compound light including light in the wavelength range of 313 nm or more and 436 nm or less, the semi-transparent film 30 has the above-described phase difference with respect to the light of the representative wavelength included in the wavelength range. . For example, when the exposure light is compound light including i-line, h-line and g-line, the semi-transparent film 30 is i-line (wavelength: 365 nm), h-line (wavelength: 405 nm) and g-line (wavelength: 436 nm) has the above-mentioned retardation.

Furthermore, the thickness of the semi-translucent film 30 in the present invention (Embodiments 1 to 3) is set to obtain the transmittance (10% or more and 60% or less) and the phase difference (0 degrees or more and 120 degrees or less). In the case where the set film thickness varies in the range of ± 3 nm, the semi-translucent film has the characteristic that the transmittance at the exposure wavelength can be controlled so that the variation range is within ± 2%. A photomask blank and a photomask having a semitransparent film with small transmittance variation with respect to thickness variation are obtained.

As for the material of the semi-translucent film 30, when the set film thickness for obtaining the transmittance (10% or more and 60% or less) and the phase difference (0 degrees or more and 120 degrees or less) fluctuates within a range of ±3 nm. 3, select a material having a refractive index n and an extinction coefficient k that can control the transmittance at the exposure wavelength so that the fluctuation range is within ±2%.

The design concept of the refractive index n and the extinction coefficient k as described above is based on the conventional semitransparent film in a predetermined wavelength band (for example, a wavelength range of 313 nm or more and 436 nm or less, a wider wavelength range including this range). This is different from the design concept of material design, refractive index n, and extinction coefficient k, in which emphasis is placed on keeping the fluctuation range of transmittance within a predetermined range.
The present invention is a design concept that eliminates the restrictions on the predetermined wavelength band. A design concept of material design, refractive index n, and extinction coefficient k may be used.

In addition, the design concept of the refractive index n and the extinction coefficient k as described above is based on the fluctuation of the transmittance of the semi-transparent film with respect to the major wavelengths (for example, i-line, h-line, and g-line) that contribute to conventional exposure. It is different from the conventional material design, the refractive index n, and the extinction coefficient k design concept, which focuses on keeping the width within a predetermined range.
The present invention is a design concept that eliminates restrictions corresponding to major wavelengths (e.g., i-line, h-line, g-line) that contribute to exposure. For example, material design for one representative wavelength, refractive index n, extinction coefficient The design concept of k may be used.

Basically, the film thickness and transmittance of the semi-transparent film are inversely proportional (inversely proportional). become) relationship.
In the present invention, the phenomenon that the transmittance does not change even if the thickness of the semi-transparent film increases is that before and after the target transmittance (set film thickness), as the film thickness increases, the transmittance decreases. Although it should be, the decrease in back surface reflectance compensates for the decrease in transmittance. Therefore, the transmittance and the rear surface reflectance are balanced, and a phenomenon occurs in which the change in transmittance becomes gentle with respect to the change in film thickness, and the change in transmittance with respect to the change in film thickness becomes small. In the present invention, a phenomenon occurs in which the transmittance stays close to the target in the region where the back surface reflectance decreases.
On the other hand, before and after the target transmittance (set film thickness), when there is a relationship in which the back surface reflectance increases as the film thickness increases, the transmittance simply decreases as the film thickness increases, Transmittance changes sensitively to changes in film thickness due to the double effect that the amount of loss due to back surface reflection increases and the amount of transmitted light decreases accordingly. becomes larger.
In the present invention, even in an aspect in which the back surface reflectance bottoms out in the vicinity of the target transmittance (an aspect in which the back surface reflectance does not decrease when the back surface reflectance changes from a decrease to an increase), the film thickness The change in transmittance with respect to the change in film thickness is smaller than in the case where the reflectance on the rear surface increases as . Similarly, even in the case where the back surface reflectance does not decrease in the vicinity of the target transmittance, compared to the case where the back surface reflectance increases as the film thickness increases, the change in transmittance with respect to the change in film thickness becomes smaller.

When the film thickness of the translucent film 30 fluctuates within a range of ±3 nm with respect to the set film thickness for obtaining the transmittance (10% or more and 60% or less) and the phase difference (0 degrees or more and 120 degrees or less) , any film thickness can be set such that the fluctuation range of the transmittance at the exposure wavelength is within ±2%.
However, for example, in the case of a thin film of 30 nm or less, it is difficult to form a film according to the designed film thickness.
Considering the cross-sectional shape when patterning the semi-transparent film 30 and the etching time when patterning the semi-transparent film 30, the thickness is preferably 120 nm or less.
From the above points, the thickness of the semi-translucent film 30 is preferably 40 nm or more and 120 nm or less, more preferably 45 nm or more and 110 nm or less, further preferably 50 nm or more and 100 nm or less.

Preferably, the set film thickness of the semi-translucent film 30 can be arbitrarily determined within the above film thickness range. For example, the film thickness of the semi-translucent film 30 may be set as a median value, the film thickness may be set as an upper limit value in consideration of film thickness reduction, or the film thickness error may be taken into consideration and a film formation error may be considered as a lower limit value from the upper limit value. It can be set on the value side.

In the graphs showing the relationship between the thickness of the semi-translucent film 30 and the transmittance and phase difference (and the group of graphs obtained by changing n and k), the semi-translucent film 30 has a predetermined transmittance. (10% or more and 60% or less), a phase difference (0 degree or more and 120 degrees or less), and a portion (film thickness range) where the change in transmittance with respect to the film thickness change of the semi-translucent film 30 is small, visually is the set transmittance (horizontal axis) in the above graph, the film thickness of the semi-translucent film 30 corresponding to the portion where the angle formed by the film thickness-transmittance curve is small (flat portion), the refractive index n, and the extinction Set and use the factor k.

For example, when the semi-transparent film 30 is made of a metal silicide-based material, has a transmittance of 30% or more and 50% or less with respect to exposure light (h-line: wavelength 405 nm), and a phase difference of 0 degrees or more and 120 degrees or less. , the semitransparent film 30 should have a refractive index n of 2.35 or more and 2.55 or less and an extinction coefficient of 0.2 or more and 0.45 or less.
When the semitransparent film 30 is made of a chromium-based material, has a transmittance of 30% or more and 50% or less with respect to exposure light (h-line: wavelength 405 nm), and a phase difference of 0 degree or more and 120 degrees or less, , the semi-transparent film 30 should have a refractive index n of 2.20 or more and 2.55 or less and an extinction coefficient of 0.45 or more and 0.50 or less.
The semitransparent film 30 can be formed by a sputtering method.

[Light shielding film 40]
The photomask blank 10 of Embodiment 1-2 has a light shielding film 40 having a function of blocking transmission of exposure light on the semitransparent film 30 . In the embodiment 1-2, the light shielding film 40 preferably has an optical density of 3 or more, more preferably 3.0, with respect to the exposure light at the portion where the semitransparent film 30 and the light shielding film 40 are laminated. It is 5 or more, more preferably 4 or more.

The material of the light shielding film 40 is not particularly limited as long as it has a function of blocking transmission of exposure light. For example, as the material of the light shielding film 40, a chromium-based material or a transition metal silicide-based material can be used.

When the material of the light shielding film 40 is a chromium-based material, chromium (Cr) or a chromium-based material containing chromium (Cr) and at least one of nitrogen (N), oxygen (O), and carbon (C) is used. mentioned. Specifically, Cr, CrN, CrO, CrC, CrON, CrCN, CrCO, and CrCON materials can be used.

When the material of the light shielding film 40 is a transition metal silicide-based material, transition metal silicide, nitride of transition metal silicide, oxide of transition metal silicide, carbide of transition metal silicide, oxynitride of transition metal silicide, transition metal Materials such as oxycarbides of silicides, oxycarbides of transition metal silicides, and oxynitride carbides of transition metal silicides can be used. Molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), zirconium (Zr) and the like are suitable as transition metals.

When the photomask blank 10 of Embodiment 1-2 is formed by forming the semi-transparent film 30 and the light-shielding film 40 in contact with each other on the light-transmitting substrate 20, the semi-transparent film 30 and the light-shielding film 40 are , it is desirable to select materials with different etch selectivities. Here, the difference in etching selectivity means that the semi-transparent film 30 is not substantially etched with an etchant capable of patterning the light-shielding film 40, and the light-shielding film 40 is not etched with an etchant capable of patterning the semi-transparent film 30. Refers to a relationship that is not substantially etched.

For example, if the semi-transparent film 30 is a transition metal silicide-based material that does not contain chromium, a chromium-based material is selected for the light shielding film 40 . If the semi-translucent film 30 is made of a chromium-based material, the light-shielding film 40 should be made of a transition metal silicide-based material that does not contain chromium.

Further, in the photomask blank 10 of the embodiment 1-2, materials having the same etching selectivity can be selected for the semitransparent film 30 and the light shielding film 40 . For example, the translucent film 30 and the light shielding film 40 can be made of a chromium-free transition metal silicide-based material, or the semi-translucent film 30 and the light shielding film 40 can be made of a chromium-based material. In this case, between the semi-transparent film 30 and the light-shielding film 40, it is preferable to provide an etching stop film made of a material with different etching selectivity.
In this case, the etching stopper film is an etching stopper film and a semi-translucent film, so that there are four shades (black, gray 1, 2, and white) having two kinds of semi-translucent films. of photomask blanks can be manufactured. For example, a four-gradation photomask blank having, on a substrate, a semi-transparent film made of a chromium-based material, an etching-stopping film and semi-translucent film made of a MoSi-based material, and a chromium light-shielding film in this order is manufactured. can be done. In this case, as the semi-transparent film made of a chromium-based material, a semi-transparent film having the same characteristics and film thickness as the semi-transparent film of Example 3, which will be described later, is used. By using a semi-translucent film having the same characteristics and film thickness as the semi-translucent film of Example 1, which will be described later, as the film and semi-translucent film, the two types of semi-translucent films are It is possible to manufacture a photomask blank having a semi-transparent film that can control the change in transmittance with respect to the film thickness variation of the semi-transparent film.
In the above case, the light-shielding film 40 preferably has an optical density of 3 or more, more preferably 3 or more, in the portion where the semi-transparent film 30, the etching stopper film, and the light-shielding film 40 are laminated. 0.5 or more, more preferably 4 or more.

Further, the surface of the light shielding film 40 opposite to the translucent substrate 20 may have a function of reducing the reflectance in the wavelength band of the exposure light. In this case, the light-shielding film 40 can have a laminated structure including a light-shielding layer mainly having a function of blocking exposure light and a front-surface antireflection layer having a function of reducing reflectance.
The light shielding film 40 can be formed by a sputtering method.

[Light shielding film pattern 40a]
The photomask blank 10 of Embodiment 1-3 has a light-shielding film pattern 40a between the translucent substrate 20 and the semi-translucent film 30. As shown in FIG. In Embodiment 1-3, the light-shielding film pattern 40a preferably has an optical density of 3 or more, more preferably It is 3.5 or more, more preferably 4 or more.

As the material of the light shielding film pattern 40a, the same material as the light shielding film 40 can be used. For example, the light shielding film pattern 40a and the semitransparent film 30 can be made of the same chromium-based material, or can be made of the same transition metal silicide-based material. Alternatively, the light-shielding film pattern 40a may be made of a chromium-based material and the semi-transparent film 30 may be made of a transition metal silicide-based material that does not contain chromium, or the light-shielding film pattern 40a is made of a transition-metal silicide-based material that does not contain chromium and is semi-transparent. Membrane 30 can also be a chromium-based material.
The light shielding film pattern 40a can be formed by patterning the light shielding film 40 formed by the sputtering method by etching.

The photomask blanks 10 of Embodiments 1-1, 1-2, and 1-3 may have a resist film on the semitransparent film 30 and the light shielding film 40. FIG. Further, the uppermost layer of the photomask blanks 10 of Embodiments 1-2, 1-2, and 1-3 is the semi-translucent film 30 and the light shielding film 40, and the etching mask functions as a mask layer when patterning these. A film may be formed. In this case, the etching mask film uses a material having etching selectivity different from that of the semi-translucent film 30 and the light shielding film 40 .

According to the photomask blanks of the above-described embodiments 1-1, 1-2, and 1-3, a photo mask having a semi-transparent film capable of controlling the transmittance fluctuation with respect to the film thickness fluctuation of the semi-translucent film to be small. A mask blank can be manufactured. In addition, it is possible to manufacture a photomask having a semi-transmissive film pattern with better transmittance uniformity in the substrate plane by controlling the transmittance variation with respect to the film thickness variation of the semi-transmissive film to be small. .

Embodiment 2 (Embodiments 2-1 and 2-2)
In Embodiment 2, a method for manufacturing a photomask will be described. Embodiment 2-1 is a method of manufacturing a photomask using the photomask blank of Embodiment 1-2. Embodiment 2-2 is a method of manufacturing a photomask using the photomask blank of Embodiment 1-3.

Each step of the photomask manufacturing method of Embodiments 2-1 and 2-2 will be described below.

Embodiment 2-1
1. First Resist Film Pattern Forming Step In the first resist film pattern forming step, first, a resist film is formed on the light shielding film 40 of the photomask blank 10 of Embodiment 1-2. However, when the photomask blank 10 has a resist film on the light shielding film 40, the resist film is not formed.
After that, the resist film is developed with a predetermined developer to form a first resist film pattern on the light shielding film 40 .

2. Mask pattern forming step for semi-translucent film pattern formation (first light shielding film pattern forming step)
In the mask pattern forming step, the light shielding film 40 is etched using the first resist film pattern as a mask to form a mask pattern for forming a semi-translucent film pattern. The etching medium (etching solution, etching gas) for etching the light shielding film 40 is not particularly limited as long as it can etch the light shielding film 40 . For example, when the material of the light shielding film 40 is composed of a chromium-based material, an etching solution containing ceric ammonium nitrate and perchloric acid, or an etching gas composed of a mixed gas of chlorine gas and oxygen gas can be used. Further, when the light-shielding film 40 is made of a transition metal silicide-based material, at least one fluorine compound selected from hydrofluoric acid, hydrosilicofluoric acid, and ammonium hydrogen fluoride, hydrogen peroxide, nitric acid, and Etching solutions containing at least one oxidizing agent selected from sulfuric acid, fluorine-based gases such as CF ₄ gas, CHF ₃ gas and SF ₆ gas, and etching gases obtained by mixing these gases with O ₂ gas can be used.
After that, the first resist film pattern is removed using a resist remover or by ashing. The first resist film pattern may be peeled off after the semi-translucent film pattern forming step, which will be described later.

3. Semi-Translucent Film Pattern Forming Step In the semi-translucent film pattern forming step, the semi-translucent film 30 is etched using the aforementioned mask pattern (first light shielding film pattern) as a mask to form a semi-translucent film pattern. to form The etching medium (etching solution, etching gas) for etching the semi-permeable film 30 is not particularly limited as long as it can etch the semi-transparent film 30 . Since the etching medium is the same as that of the light shielding film 40, the explanation is omitted.

4. Second resist film pattern forming process The second resist film pattern forming process is a process for forming a predetermined light shielding film pattern on the semi-transparent film pattern. This is the step of forming a second resist film pattern. A resist film is formed so as to cover the translucent film pattern and the first light shielding film pattern obtained in the above steps.
After that, a predetermined pattern is drawn on the resist film using a laser beam having a wavelength selected from a wavelength range of 350 nm to 436 nm. Patterns drawn on the resist film include line-and-space patterns and hole patterns.
After that, the resist film is developed with a predetermined developer to form a second resist film pattern on the first light-shielding film pattern.

5. Light-Shielding Film Pattern Forming Step Using the second resist film pattern as a mask, the first light-shielding film pattern is etched to form a light-shielding film pattern on the semi-transparent film pattern. The etching medium (etching solution, etching gas) for etching the first light shielding film pattern is the same as the etching medium for etching the light shielding film 40 described above, so the description thereof will be omitted.
Thereafter, the second resist film pattern is removed using a resist remover or by ashing to obtain the photomask of Embodiment 2-1. In the photomask of the embodiment 2-1, the region where the semi-transparent film pattern and the light-shielding film pattern 40a are not formed on the translucent substrate 20 is the translucent portion, and only the semi-translucent film pattern is formed. The area where the semi-transparent film pattern and the light-shielding film pattern 40a are laminated serves as a light-shielding part.

According to the photomask manufacturing method of the embodiment 2-1, it is possible to manufacture a photomask having a semi-translucent film pattern that can control the transmittance fluctuation with respect to the film thickness variation of the semi-translucent film to be small. can. In addition, it is possible to manufacture a photomask having a semi-transmissive film pattern with better transmittance uniformity in the substrate plane by controlling the transmittance variation with respect to the film thickness variation of the semi-transmissive film to be small. .

Embodiment 2-2
1. Resist Film Pattern Forming Process In the resist film pattern forming process, first. A resist film is formed on the semitransparent film 30 of the photomask blank 10 of Embodiment 1-3. However, if the photomask blank 10 has a resist film on the semitransparent film 30, the resist film is not formed. The resist film material to be used is not particularly limited. Any material may be used as long as it is sensitive to a laser beam having a wavelength selected from the wavelength range of 350 nm to 436 nm, which will be described later. Moreover, the resist film may be either positive type or negative type.
After that, a predetermined pattern is drawn on the resist film using a laser beam having a wavelength selected from a wavelength range of 350 nm to 436 nm. Patterns drawn on the resist film include line-and-space patterns and hole patterns.
After that, the resist film is developed with a predetermined developer to form a resist film pattern on the semitransparent film 30 .

2. Semi-Translucent Film Pattern Forming Step In the semi-translucent film pattern forming step, the semi-translucent film 30 is etched using the resist film pattern as a mask to form a semi-translucent film pattern. The semi-translucent film pattern is formed, for example, so as to straddle the adjacent light-shielding film patterns 40a. The etching medium (etching solution, etching gas) for etching the semi-translucent film is not particularly limited as long as it can etch the semi-translucent film 30 . Since the etching medium is the same as in Embodiment 2-1, the description is omitted.
Thereafter, the resist film pattern is removed using a resist remover or by ashing to obtain the photomask of Embodiment 2-2. In the photomask of the embodiment 2-2, the region where the light shielding film pattern 40a and the semi-transparent film pattern are not formed on the translucent substrate 20 is the light-transmitting portion, and only the semi-transparent film pattern is formed. The region where the light-shielding film pattern 40a and the semi-light-transmitting film pattern are laminated serves as a light-shielding portion.

According to the photomask manufacturing method of the embodiment 2-2, it is possible to manufacture a photomask having a semi-transparent film pattern that can control the change in transmittance with respect to the film thickness variation of the semi-transparent film to be small. can. In addition, it is possible to manufacture a photomask having a semi-transmissive film pattern with better transmittance uniformity in the substrate plane by controlling the transmittance variation with respect to the film thickness variation of the semi-transmissive film to be small. .

Embodiment 3
In Embodiment 3, a method for manufacturing a display device will be described. The display device is manufactured by performing the following mask placement process and pattern transfer process.
Each step will be described in detail below.
1. Mounting Step In the mounting step, the photomasks manufactured in Embodiments 2-1 and 2-2 are mounted on the mask stage of the exposure apparatus. Here, the photomask is arranged so as to face the resist film formed on the display device substrate via the projection optical system of the exposure device.

2. Pattern transfer process In the pattern transfer process, the photomask manufactured in Embodiments 2-1 and 2-2 is irradiated with exposure light to form a light shielding film pattern on the resist film formed on the display device substrate. The pattern is transferred by the light shielding portion, the semi-transparent portion having the semi-transparent film pattern, and the transparent portion having no semi-transparent film pattern. The exposure light is compound light containing light of a plurality of wavelengths selected from a wavelength range of 313 nm to 436 nm, or monochromatic light selected by cutting a certain wavelength range from the wavelength range of 313 nm to 436 nm with a filter or the like. For example, the exposure light is compound light including i-line, h-line and g-line, mixed light including j-line, i-line, h-line and g-line, or i-line monochromatic light. When compound light is used as the exposure light, the intensity of the exposure light can be increased and the throughput can be increased, so that the manufacturing cost of the display device can be reduced.

According to the manufacturing method of the display device of the third embodiment, after the pattern transfer is performed using the photomask, even if the photomask is repeatedly washed, the fluctuation of the optical characteristics (transmittance with respect to the exposure light) can be reduced. In other words, a display device can be manufactured in which the CD error of pattern transfer caused by the photomask does not occur because the transmittance fluctuation with respect to the film thickness fluctuation of the semi-transparent film pattern is small.

Note that the photomask blanks of the above-described Embodiments 1-1, 1-2, and 1-3 and the photomasks manufactured by the photomask manufacturing methods of Embodiments 2-1 and 2-2 are the same size. It can be used in photomask blanks and photomasks for projection exposure of exposure, and can also be used in photomask blanks and photomasks for proximity exposure of proximity exposure. In particular, the present invention has the maximum effect in photomask blanks and photomasks for proximity exposure of proximity exposure because the variation in optical characteristics (transmittance to exposure light) is small even when the photomask is repeatedly washed. can be demonstrated.

Examples of the present invention and comparative examples are shown below. The semi-translucent film and the light-shielding film of each example and comparative example were formed by a sputtering method using an in-line sputtering apparatus as a film forming apparatus. However, in carrying out the present invention, the film forming method and film forming apparatus are not particularly limited.
(Example 1)
(Experimental Examples 1-1, 1-2, 1-3)
In Experimental Examples 1-1 to 1-3, the material of the semitransparent film is a molybdenum silicide-based material, and the transmittance is set to 40% at the h-line (wavelength 405 nm), which is the representative wavelength of the exposure light. This is an experimental example for selecting a semi-transparent film having a predetermined refractive index n and extinction coefficient k that reduces the change in transmittance with respect to the film thickness of the semi-transparent film.

(Optical simulation and selection of semi-translucent film)
First, in order to select a semi-transparent film having a predetermined refractive index n and extinction coefficient k, which has a small change in transmittance with respect to a change in film thickness, a film is formed on a light-transmitting substrate under different film formation conditions. A plurality of types of semitransparent films having different refractive indices n and extinction coefficients k were formed.
The formation of the semi-transparent film is performed using an in-line sputtering apparatus used when manufacturing a photomask blank for FPD, and the refractive index n and the extinction coefficient of the formed semi-transparent film are In order to measure k with an n&k analyzer, a translucent substrate (dummy substrate) made of a synthetic quartz glass material with a size of 152 mm×152 mm was used.

The conditions for forming the semi-transparent films, the refractive index n and the extinction coefficient k of the semi-transparent films in Experimental Examples 1-1 to 1-3 are as follows. The film thickness of the semitransparent film in Experimental Examples 1-1 to 1-3 was set to 100 nm. The refractive index n and the extinction coefficient k are values of h-line (wavelength 405 nm), which is a representative wavelength of exposure light.
[Experimental example 1-1]
Sputtering target: molybdenum silicide target (Mo:Si=11:89)
Deposition gas: mixed gas of argon gas, nitrogen gas and helium gas (Ar:N ₂ :He=18:12:50)
Gas pressure: 1.6 Pa
Refractive index n of semitransparent film: 2.431, extinction coefficient k: 0.315

[Experimental example 1-2]
Sputtering target: molybdenum silicide target (Mo:Si=8:92)
Film-forming gas: mixed gas of argon gas, nitrogen gas, helium gas and nitric oxide gas (Ar:N ₂ :He:NO=18:13:50:4)
Gas pressure: 1.6 Pa
Refractive index of semitransparent film n: 2.300, extinction coefficient k: 0.157

[Experimental example 1-3]
Sputtering target: molybdenum silicide target (Mo:Si=20:80)
Deposition gas: mixed gas of argon gas and nitrogen gas (Ar:N ₂ =18:11)
Gas pressure: 0.6 Pa
Refractive index of semitransparent film n: 2.650, extinction coefficient k: 0.530

Next, based on the refractive index n and the extinction coefficient k of the semi-transparent films in Experimental Examples 1-1 to 1-3, the film thickness was set so that the transmittance of the semi-transparent film was 40%. On the other hand, a simulation was performed for the transmittance, phase difference, and rear surface reflectance of the semi-transparent film when the film thickness of the semi-transparent film was changed.

Table 1 and FIG. 4 show the simulation results of the transmittance, phase difference, and rear surface reflectance of the semitransparent film in Experimental Example 1-1.

As shown in the above results, the semi-transparent film of Experimental Example 1-1 has a transmittance of 40% (0.40) with respect to the set film thickness within a range of ±3.5 nm. , the change in transmittance at 405 nm, which is a representative wavelength of the exposure wavelength, was suppressed to ±2.0%. This is because the rear surface reflectance increases as the thickness of the semi-transparent film increases in the range of ±3.5 nm with respect to the set film thickness at which the transmittance of the semi-translucent film is 40%. The tendency to decrease is considered to be one of the reasons why the variation in transmittance at 405 nm, which is a typical exposure wavelength, is suppressed to ±2.0%.
In addition, in FIG. 4, the transmittance at the film thickness of 85.5 nm is 38.0% (0.38).

Next, Table 2 and FIG. 5 show simulation results of the transmittance, phase difference, and rear surface reflectance of the semitransparent film in Experimental Example 1-2.

As the above results show, the semi-transparent film of Experimental Example 1-2 fluctuates within a range of ±20 nm with respect to the set film thickness at which the transmittance of the semi-transparent film is 40% (0.40). In this case, the transmittance fluctuation at 405 nm, which is the representative wavelength of the exposure wavelength, could be suppressed to ±2.0%, but the phase difference of the semitransparent film exceeded 120 degrees. .

Next, Table 3 and FIG. 6 show simulation results of the transmittance, phase difference, and rear surface reflectance of the semitransparent film in Experimental Example 1-3.

As the above results show, the semi-transparent film of Experimental Example 1-3 has a transmittance of 40% (0.40) with respect to the set film thickness within a range of ±1.0 nm. , the change in transmittance at 405 nm, which is a representative wavelength of the exposure wavelength, was suppressed to ±2.0%. As compared with the semi-transparent film of Experimental Example 1-1, the results showed that the change in transmittance with respect to the film thickness variation of the semi-transparent film was large. With respect to the set film thickness at which the transmittance of the semi-translucent film is 40%, the rear surface reflectance increases as the thickness of the semi-translucent film increases within a range of ±3.5 nm. The tendency to increase is considered to be one of the reasons why the transmittance fluctuation with respect to the film thickness fluctuation of the semi-translucent film has increased.

(Example 1)
Next, the photomask blank 10 of Example 1 will be described. As the semi-transparent film 30 in the photomask blank 10 of Example 1, the semi-transparent film of Experimental Example 1-1 was selected.
The photomask blank of Example 1 includes a translucent substrate 20 , a semi-translucent film 30 disposed on the translucent substrate 20 , and a light shielding film 40 . A synthetic quartz glass substrate having a size of 800 mm×920 mm and a thickness of 10 mm was used as the translucent substrate 20 .

A photomass blank of Example 1 was manufactured by the following method.
First, a synthetic quartz glass substrate, which is the translucent substrate 20, was prepared. Both main surfaces of the synthetic quartz glass substrate are mirror-polished.
Next, the synthetic quartz glass substrate was carried into an in-line sputtering apparatus, and under the film forming conditions of Experimental Example 1-1, a semi-crystalline film made of molybdenum silicide nitride containing molybdenum, silicon, and nitrogen was formed on the synthetic quartz glass substrate. A translucent film 30 was formed. The film thickness of the semitransparent film 30 was set to 82 nm so that the transmittance at 405 nm, which is the representative wavelength of the exposure light, would be 40%. When the transmittance at a wavelength of 405 nm was measured at 11×11 measurement points within the substrate plane, the transmittance variation was ±0.4%, which was a very good value. One of the reasons for this is thought to be that the transmittance fluctuation with respect to the film thickness fluctuation of the semi-translucent film is within ±2.0%, which is a very small value.

Further, the resulting semi-translucent film 30 was washed with alkali (ammonia permeate water (APM), 30° C., 5 minutes) six times, and the transmission due to the film thickness variation of the semi-translucent film 30 was washed. rate change was evaluated. As a result, the change in transmittance of the semitransparent film 30 was as small as 0.5% compared to before the alkali cleaning treatment. This evaluation was performed on the semitransparent film 30 (dummy substrate) formed on the synthetic quartz glass substrate under the same film formation conditions. From the above results, it can be said that the semi-transparent film 30 of Example 1 is a semi-transparent film in which the change in transmittance with respect to the change in film thickness is extremely small.

Next, a light shielding film 40 was formed on the semitransparent film 30 under the following conditions. First, a chromium nitride layer (CrN layer) containing chromium and nitrogen was formed on the translucent film 30 by reactive sputtering using a mixed gas of argon gas and nitrogen gas (thickness: 15 nm). ). Next, a chromium carbide layer (CrC layer) containing chromium and carbon was formed on the chromium nitride layer by reactive sputtering with a mixed gas of argon gas and methane gas (thickness: 60 nm). Next, a chromium oxynitride layer (CrON layer) containing chromium, oxygen, and nitrogen was formed on the chromium carbide layer by reactive sputtering using argon gas and nitrogen monoxide gas (thickness: 25 nm). . As described above, the photomask blank 10 was obtained by forming the light shielding film 40 having a laminated structure of the CrN layer, the CrC layer and the CrON layer on the semitransparent film 30 . The CrON layer has a surface antireflection function that reduces the reflectance with respect to the exposure wavelength and the laser drawing wavelength.

Next, using the photomask blank 10 described above, a photomask was produced by the method described in Embodiment 2-1. As a result, the semi-transparent portion in the region where only the semi-transparent film pattern made of molybdenum silicide nitride is formed, the semi-transparent film pattern, and the light-shielding film made of a chromium-based material on the semi-transparent film pattern. A photomask having a light-shielding portion in the region where the pattern 40a is laminated and a light-transmitting portion in the region where the semi-transparent film pattern and the light-shielding film pattern are not formed was obtained.

The photomask of Example 1 obtained as described above has good transmittance uniformity in the substrate surface and a semi-transparent film 30 having a small change in transmittance with respect to a change in film thickness. Therefore, even if the film thickness of the semi-translucent film pattern decreases after repeated cleaning of the photomask, the transmittance of the semi-translucent film pattern does not fluctuate. can be made smaller.
Therefore, even when the photomask of Example 1 is used to fabricate a display device, the pattern transfer CD error due to the photomask does not occur.

(Comparative example 1)
As the semi-transparent film in the photomask blank of Comparative Example 1, the semi-transparent film of Experimental Example 1-3 was selected. The semi-transparent film was formed by forming a semi-transparent film made of molybdenum silicide nitride containing molybdenum, silicon and nitrogen on a synthetic quartz substrate under the film formation conditions of Experimental Example 1-3. . The film thickness of this semitransparent film was set to 29 nm so that the transmittance at 405 nm, which is the representative wavelength of the exposure light, would be 40%.
When the transmittance at a wavelength of 405 nm was measured at 11×11 measurement points within the substrate surface, the transmittance variation was ±0.7%, which was a large value compared to Example 1.
Further, the resulting semi-translucent film 30 was washed with alkali (ammonia permeate water (APM), 30° C., 5 minutes) six times, and the transmission due to the film thickness variation of the semi-translucent film 30 was washed. rate change was evaluated. As a result, the change in transmittance of the semitransparent film 30 was 1.6%, which is a large value, compared to before the alkali cleaning treatment. From the above results, the semi-transparent film of Comparative Example 1 is a semi-transparent film with a large change in transmittance with respect to the change in film thickness.

Next, similarly to Example 1, a light-shielding film was formed on the semitransparent film to prepare a photomask blank.
The photomask of Comparative Example 1 obtained as described above was produced using a photomask blank having poor transmittance uniformity in the substrate surface and large transmittance fluctuations with respect to film thickness fluctuations of the semi-translucent film. Therefore, if the film thickness of the semi-translucent film pattern is reduced when the photomask is repeatedly washed, the transmittance of the semi-translucent film pattern varies greatly. A CD error in pattern transfer due to the photomask will occur.

(Example 2)
(Experimental Examples 2-1 and 2-2)
Based on the refractive index n and the extinction coefficient k of the semitransparent films of Experimental Examples 1-3 and 1-1, the transmittance of the semitransparent film is 30% (0.30). A simulation was performed for the refractive index, phase difference, and rear surface reflectance of the semi-transparent film when the film thickness of the semi-transparent film was changed with respect to the set film thickness.

Table 4 and FIG. 7 show the simulation results (Experimental Example 2-1) of the transmittance, phase difference, and rear surface reflectance of the semitransparent film in Experimental Example 1-3.

As described above, the semi-transparent film of Experimental Example 1-3 (Experimental Example 2-1) had a transmittance of ±6.5 nm with respect to the set film thickness at which the transmittance of the semi-transparent film was 30%. When the transmittance fluctuated within the range, the transmittance fluctuation width at 405 nm, which is the representative wavelength of the exposure wavelength, was suppressed to ±2.0%. With respect to the set film thickness at which the transmissivity of the translucent film is 30%, the rear surface It is considered that the fact that the reflectance tends to decrease is one of the reasons why the fluctuation of the transmittance at 405 nm, which is the representative wavelength of the exposure wavelength, is suppressed to ±2.0%.

Next, Table 5 and FIG. 8 show simulation results (Experimental Example 2-2) of the transmissivity, phase difference, and rear surface reflectance of the semitransparent film in Experimental Example 1-1.

As the above results show, the semi-transparent film of Experimental Example 1-1 (Experimental Example 2-2) has a transmittance of 30% (0.30) for the set film thickness. , when it fluctuates in the range of ±4.5 nm, the transmittance fluctuation range at 405 nm, which is the representative wavelength of the exposure wavelength, is ±2.0%, and the phase difference of the semi-translucent film exceeds 120 degrees. It has become Compared to Experimental Example 1-3 above, the reason why the change in transmittance with respect to the film thickness of the semi-translucent film was large was that as the film thickness of the semi-translucent film increased, the back surface The fact that the reflectance also tends to increase is considered to be one of the reasons why the change in the transmittance with respect to the change in the film thickness of the semi-transparent film has increased.

(Example 2)
Next, the photomask blank 10 of Example 2 will be described. As the semi-transparent film 30 in the photomask blank 10 of Example 2, the semi-transparent film of Experimental Example 1-3 was selected.
The semi-transparent film 30 is formed on a synthetic quartz substrate under the film formation conditions of Experimental Example 1-3, and is made of molybdenum silicide nitride containing molybdenum, silicon, and nitrogen. did. The film thickness of the semitransparent film 30 was set to 60 nm so that the transmittance at 405 nm, which is the representative wavelength of the exposure light, would be 30%.
When the transmittance at a wavelength of 405 nm was measured at 11×11 measurement points in the plane of the substrate, the transmittance variation was ±0.5%, which was a very good value.
Further, the resulting semi-translucent film 30 was washed with alkali (ammonia permeate water (APM), 30° C., 5 minutes) six times, and the transmission due to the film thickness variation of the semi-translucent film 30 was washed. rate change was evaluated. As a result, the change in transmittance of the semitransparent film 30 was as small as 0.5% compared to before the alkali cleaning treatment. This evaluation was performed on the semitransparent film 30 (dummy substrate) formed on the synthetic quartz glass substrate under the same film formation conditions. From the above results, it can be said that the semi-transparent film 30 of Example 1 is a semi-transparent film in which the change in transmittance with respect to the change in film thickness is extremely small.

Next, in the same manner as in Example 1, a light-shielding film was formed on the semitransparent film to prepare a photomask blank. As a result, the semi-transparent portion in the region where only the semi-transparent film pattern made of molybdenum silicide nitride is formed, the semi-transparent film pattern, and the light-shielding film made of a chromium-based material on the semi-transparent film pattern. A photomask having a light-shielding portion in the region where the pattern 40a is laminated and a light-transmitting portion in the region where the semi-transparent film pattern and the light-shielding film pattern are not formed was obtained.

The photomask of Example 2 obtained as described above has good transmittance uniformity in the substrate surface and a semi-transparent film 30 having a small change in transmittance with respect to a change in film thickness. Therefore, even if the film thickness of the semi-translucent film pattern decreases after repeated cleaning of the photomask, the transmittance of the semi-translucent film pattern does not fluctuate. can be made smaller.
Therefore, even when the photomask of Example 2 is used to manufacture a display device, the pattern transfer CD error caused by the photomask does not occur.

(Example 3)
(Experimental Examples 3-1 and 3-2)
In Experimental Examples 3-1 and 3-2, the material of the semi-translucent film is a chromium-based material, and the transmittance is 30% (0.30 ), an experiment for selecting a semi-transparent film having a predetermined refractive index n and extinction coefficient k that reduces the change in transmittance with respect to the film thickness variation of the semi-transparent film For example.
The film formation conditions of the semi-translucent films, the refractive index n and the extinction coefficient k of the semi-translucent films in Experimental Examples 3-1 and 3-2 are as follows. The film thickness of the semitransparent film in Experimental Examples 3-1 and 3-2 was set to 100 nm. The refractive index n and the extinction coefficient k are values of h-line (wavelength 405 nm), which is a representative wavelength of exposure light.

[Experimental example 3-1]
Sputtering target: Chromium Film formation gas: Mixed gas of argon gas and carbon dioxide gas (Ar:CO ₂ =20:90)
Gas pressure: 0.3 Pa
Semitransparent film refractive index n: 2.36, extinction coefficient k: 0.49

[Experimental example 3-2]
Sputtering target: Chromium Film forming gas: Mixed gas of argon gas and carbon dioxide gas (Ar:CO ₂ =20:30)
Gas pressure: 0.3 Pa
Refractive index of semitransparent film n: 2.64, extinction coefficient k: 0.39

Next, based on the refractive index n and the extinction coefficient k of the semi-transparent films in Experimental Examples 3-1 and 3-2, the transmittance of the semi-transparent film is 30% (0.30). A simulation was performed for the transmittance, the phase difference, and the rear surface reflectance of the semi-transparent film when the film thickness of the semi-transparent film was changed with respect to the set film thickness.
Table 6 and FIG. 9 show the simulation results of the transmittance, phase difference, and rear surface reflectance of the semitransparent film in Experimental Example 3-1.

As shown in the above results, the semi-transparent film of Experimental Example 3-1 was changed in the range of ±4.0 nm with respect to the set film thickness at which the transmittance of the semi-transparent film was 30%. , the change in transmittance at 405 nm, which is a representative wavelength of the exposure wavelength, was suppressed to ±2.0%. This is because the back surface reflectance increases as the film thickness of the semi-transparent film increases in the range of ±3.5 nm with respect to the set film thickness at which the transmittance of the semi-transparent film is 30%. The tendency to decrease is considered to be one of the reasons why the variation in transmittance at 405 nm, which is a typical exposure wavelength, is suppressed to ±2.0%.

Next, Table 7 and FIG. 10 show simulation results of the transmittance, phase difference, and rear surface reflectance of the semitransparent film in Experimental Example 3-2.

As shown in the above results, the semi-transparent film of Experimental Example 3-2 has a transmittance of 30% (0.30) with respect to the set thickness of the semi-transparent film within a range of ±2.5 nm. , the transmittance fluctuation range at 405 nm, which is a typical exposure wavelength, was ±2.0%, and the phase difference of the semitransparent film exceeded 120 degrees. Compared to Experimental Example 3-1 above, the reason why the change in transmittance with respect to the film thickness of the semi-transparent film was large was that as the film thickness of the semi-transparent film increased, the back surface The fact that the reflectance also tends to increase is considered to be one of the reasons why the change in the transmittance with respect to the change in the film thickness of the semi-transparent film has increased.

(Example 3)
Next, the photomask blank 10 of Example 3 will be described. As the semi-transparent film 30 in the photomask blank 10 of Example 3, the semi-transparent film of Experimental Example 3-1 was selected.
A photomask blank of Example 3 was manufactured by the following method.
First, a synthetic quartz glass substrate, which is the translucent substrate 20, was prepared. Both main surfaces of the synthetic quartz glass substrate are mirror-polished.

Next, the synthetic quartz glass substrate was loaded into an in-line sputtering apparatus, and the light shielding film 40 was formed on the synthetic quartz glass substrate under the same film forming conditions as in the first embodiment. Next, a resist film was formed on the light-shielding film 40, and in order to form a light-shielding film pattern 40a serving as a light-shielding portion, drawing and development were performed using a laser drawing machine to form a resist film pattern. Next, using the resist film pattern as a mask, the light shielding film was etched using an etching solution to form a light shielding film pattern 40a.

Next, the resist film pattern was peeled off, and a light shielding film pattern 40a was formed on the synthetic quartz glass substrate to obtain a substrate with a light shielding film pattern. Next, under the film formation conditions of Experimental Example 3-1, a semi-transparent film 30 made of chromium carbide containing chromium, carbon, and oxygen was formed on the substrate with the light-shielding film pattern. The film thickness of the semitransparent film 30 was set to 74 nm so that the transmittance at 405 nm, which is the representative wavelength of the exposure light, would be 30%.
When the transmittance at a wavelength of 405 nm was measured at 11×11 measurement points in the plane of the substrate, the transmittance variation was ±0.5%, which was a very good value. Further, the resulting semi-translucent film 30 was washed with alkali (ammonia permeate water (APM), 30° C., 5 minutes) six times, and the transmission due to the film thickness variation of the semi-translucent film 30 was washed. rate change was evaluated. As a result, the change in transmittance of the semitransparent film 30 was as small as 0.1% compared to before the alkali cleaning treatment.

Next, a photomask was produced by the method described in the above embodiment 2-2. As a result, the semi-transparent portion in the region where only the semi-transparent film pattern made of chromium carbide oxide is formed, and the region where the light-shielding film pattern 40a made of the chromium-based material and the semi-transparent film pattern are laminated are shaded. A photomask having a light-transmitting portion in a region where the semi-light-transmitting film pattern and the light-shielding film pattern were not formed was obtained.

The photomask of Example 3 obtained as described above has good transmittance uniformity in the substrate surface and a semitransparent film 30 having a small change in transmittance with respect to a change in film thickness. Therefore, even if the film thickness of the semi-translucent film pattern decreases after repeated cleaning of the photomask, the transmittance of the semi-translucent film pattern does not fluctuate. can be made smaller.
Therefore, even when the photomask of Example 3 is used to fabricate a display device, the pattern transfer CD error due to the photomask does not occur.

As described above, the present invention has been described in detail based on the embodiments and examples, but the present invention is not limited thereto. It is obvious that those skilled in the art can make modifications and improvements within the technical spirit of the present invention.

Reference Signs List 10 photomask blank 20 translucent substrate 30 semi-translucent film 40 light shielding film 40a light shielding film pattern

Claims (7)

A photomask blank for manufacturing an FPD device having at least a semitransparent film having a function of adjusting the amount of transmission on a translucent substrate,
the semitransparent film is made of a transition metal silicide-based material containing a transition metal, silicon, and any of oxygen and nitrogen, or a chromium-based material containing chromium and any of oxygen and nitrogen;
The semi-transparent film has a transmittance of 10% or more and 60% or less and a phase difference of 0 degrees or more and 120 degrees or less with respect to exposure light, and the film thickness of the semi-transparent film is the transmittance and the phase difference. In the case where the set film thickness for obtaining
A photomask blank characterized by selecting a material for a semitransparent film having a refractive index n and an extinction coefficient k so as to obtain the above characteristics. 2. The photomask blank according to claim 1, wherein the semitransparent film has a film thickness of 40 nm or more and 120 nm or less. When the semi-translucent film fluctuates within a range of ±3 nm with respect to the set film thickness for obtaining the transmittance and phase difference, the rear surface 3. The photomask blank of claim 1 or 2, wherein reflectance tends to decrease. 4. The photomask blank according to any one of claims 1 to 3, further comprising a light shielding film on the semitransparent film. 4. The photomask blank according to claim 1, further comprising a light-shielding film pattern between said translucent substrate and said semi-translucent film. A method of manufacturing a photomask using the photomask blank according to any one of claims 1 to 5. A display device manufacturing method for manufacturing a display device by transferring the pattern of the photomask according to claim 6 .

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