JP7258717B2 - Photomask blank, method for manufacturing photomask blank, method for manufacturing photomask, and method for manufacturing display device - Google Patents

Description

The present invention relates to a photomask blank, a method for manufacturing a photomask blank, a method for manufacturing a photomask, and a display device.

2. Description of the Related Art In recent years, display devices such as FPDs (Flat Panel Displays) typified by LCDs (Liquid Crystal Displays) are rapidly increasing in screen size and viewing angle, as well as high definition and high speed display. One of the factors required for achieving high-definition and high-speed display is the fabrication of electronic circuit patterns such as fine elements and wiring with high dimensional accuracy. Photolithography is often used for patterning electronic circuits for display devices. Therefore, there is a need for photomasks for manufacturing display devices on which fine and highly accurate patterns are formed.

For example, in Patent Document 1, a semitransparent film (such as CrO), an etching stopper film (such as SiO ₂ ), a light shielding film (such as Cr), and a resist film are sequentially formed on a transparent substrate to form a transparent portion. The resist film on the portion (area C) is removed to remove the light shielding film and the etching stopper film on this portion, and then the resist on the portion where the semi-transmissive portion is to be formed is removed to remove the light shielding film on this portion. is removed to form a semi-transmissive portion, and the semi-transparent film on other areas is removed to form a transmissive portion, thereby manufacturing a gray-tone mask.

Japanese Patent Application Laid-Open No. 2002-189281

Photomasks used in recent years to manufacture high-definition (1000 ppi or more) panels require fine transfer patterns with a hole diameter of 6 µm or less and a line width of 4 µm or less to enable high-resolution pattern transfer. Formed photomasks are required. There is also a demand for a photomask having a semi-transmissive film and having a 3-gradation or 4-gradation transfer pattern formed thereon.
In order to realize such a photomask, a photomask blank has been proposed which has a semi-transmissive film, an etching stopper film, and a light shielding film in this order on a transparent substrate. Materials containing chromium are used for the light-shielding film and the semi-transmissive film from the viewpoint of light-shielding performance. Also, the etching stopper film is made of a material containing a transition metal and silicon from the viewpoint of etching selectivity.
However, when a transfer pattern is formed by wet etching on a photomask blank using these materials, there are areas where sufficient transmittance is not obtained in areas that should become transmissive areas, resulting in in-plane transmittance. In some cases, uniformity was reduced. Such a portion is not preferable because it affects the transfer performance.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to provide a semi-transmissive film having a good cross-sectional shape and sufficient transmission in the transmissive portion. It is an object of the present invention to provide a photomask blank, a method for manufacturing a photomask blank, a method for manufacturing a photomask, and a method for manufacturing a display device, capable of forming a transfer pattern having a high transmittance uniformity in the plane.

The inventor of the present invention has earnestly studied measures for solving these problems. First, in order to remove the semi-transmissive film remaining in places where sufficient transmittance cannot be obtained, the semi-transmissive film was subjected to over-etching with a greatly prolonged etching time. However, even with such overetching, the transmittance was not sufficiently improved. The present inventor conducted further investigations and found that not only the semi-transmissive film but also the etching stopper film remained in the region where sufficient transmittance was not obtained. They also found that by over-etching the etching stopper film, the etching stopper film can be removed from the transmissive portion region, and the light semi-transmissive film can also be removed.
However, if the over-etching time for the etching stopper film is long, the side etching of the pattern formed on the etching stopper film progresses, resulting in deterioration of the pattern shape. Therefore, it is desirable to shorten the overetching time.

Therefore, the present inventors changed the way of thinking and examined changing the film structure by adjusting the pressure of the sputtering gas in the film forming chamber. When forming the etching stopper film, the sputtering gas pressure in the film forming chamber is usually set to 0.1 to 0.5 Pa. However, the inventor intentionally set the sputtering gas pressure higher than 0.5 Pa to form the etching stopper film. Then, when an etching stopper film is formed at a sputtering pressure of 0.7 Pa or more and 3.0 Pa or less, preferably at a sputtering gas pressure of 0.8 Pa or more and 3.0 Pa or less, it has suitable characteristics as an etching stopper film. In addition, the present inventors have found that when a transfer pattern is formed on the etching stopper film by wet etching, the etching time can be significantly shortened, and a transfer pattern having a favorable cross-sectional shape can be formed. The etching stopper film formed in this manner had a columnar structure that is not found in ordinary etching stopper films. The present invention was made as a result of the above earnest studies, and has the following configurations.

(Configuration 1) A photomask blank having a semi-transmissive film, an etching stopper film, and a light shielding film in this order on a transparent substrate,
The photomask blank is an original plate for forming a photomask having a transfer pattern on a transparent substrate by wet etching,
the semi-transmissive film and the light-shielding film contain chromium,
The etching stopper film contains a transition metal and silicon,
A photomask blank, wherein the etching stopper film has a columnar structure.

(Arrangement 2) The photomask blank according to Arrangement 1, wherein the atomic ratio of the transition metal and the silicon contained in the etching stopper film is transition metal:silicon = 1:3 or more and 1:15 or less. .
(Structure 3) The photomask blank according to structure 1 or 2, wherein the transition metal is molybdenum.

(Configuration 4) A method for manufacturing a photomask blank having a semi-transmissive film, an etching stopper film, and a light shielding film in this order on a transparent substrate,
The semi-transmissive film and the light-shielding film are formed by sputtering using a target containing chromium in a deposition chamber,
The etching stopper film is formed by using a transition metal silicide target containing a transition metal and silicon in a deposition chamber, and forming the sputtering gas pressure in the deposition chamber to which the sputtering gas is supplied at a pressure of 0.7 Pa or more and 3.0 Pa or less. A method of manufacturing a photomask blank, characterized by:

(Structure 5) The method of manufacturing a photomask blank according to structure 4, wherein the atomic ratio of the transition metal and silicon in the transition metal silicide target is transition metal:silicon = 1:3 or more and 1:15 or less. .
(Structure 6) The method of manufacturing a photomask blank according to structure 4 or 5, wherein the semi-transmissive film, the etching stopper film, and the light-shielding film are formed using an in-line sputtering apparatus.
(Structure 7) A step of preparing the photomask blank according to any one of Structures 1 to 3 or the photomask blank manufactured by the method for manufacturing a photomask blank according to any one of Structures 4 to 6;
The semi-transmissive film, the etching stopper film, and the light-shielding film are each patterned by wet etching to form a transmissive portion that transmits exposure light, a semi-transmissive portion that partially transmits exposure light, and a light-blocking portion that blocks exposure light. and a step of forming a transfer pattern having a light-shielding portion.
(Structure 8) A photomask obtained by the method for manufacturing a photomask according to Structure 7 is placed on a mask stage of an exposure apparatus, and the transfer pattern formed on the photomask is formed on a display device substrate. A method of manufacturing a display device, comprising an exposure step of exposing and transferring a resist onto a coated resist.

According to the photomask blank or the method for manufacturing a photomask blank according to the present invention, excessive over-etching occurs when forming the required fine transfer pattern on the semi-transmissive film by wet etching using the etching stopper film pattern as a mask. It is possible to obtain a photomask blank capable of forming a transfer pattern with high in-plane uniformity of transmittance.

Further, according to the photomask manufacturing method of the present invention, a photomask is manufactured using the photomask blank described above. Therefore, it is possible to manufacture a photomask having a transferred pattern with high in-plane uniformity of transmittance without excessive over-etching and sufficient transmittance in the transmissive portion. This photomask can be applied to miniaturization of line-and-space patterns and contact holes.

Further, according to the display device manufacturing method of the present invention, a display device is manufactured using a photomask manufactured using the above-described photomask blank or a photomask obtained by the above-described photomask manufacturing method. . Therefore, a display device having fine line-and-space patterns and contact holes can be manufactured.

1 is a schematic diagram showing a film configuration of a photomask blank according to Embodiment 1; FIG. FIG. 10 is a schematic diagram showing a manufacturing process of the photomask according to the second embodiment;

Embodiment 1
In Embodiment 1, a photomask blank will be described. The photomask blank of Embodiment 1 is an original plate for forming a photomask having a transflective portion, a transmissive portion and a light shielding portion on a transparent substrate by wet etching.

FIG. 1 is a schematic diagram showing the film structure of a photomask blank 10 according to the first embodiment.
The photomask blank 10 shown in FIG. 1 includes a semi-transmissive film 30, an etching stopper film 40, and a light shielding film 50 on a transparent substrate 20 in this order.
FIG. 2 is a schematic diagram showing the film structure of the photomask blank 10 according to the second embodiment.
The photomask blank 10 shown in FIG. 2 includes a transparent substrate 20 and a semi-transmissive film 30, an etching stopper film 40, and a light shielding film 50 on the transparent substrate 20 in this order.
The transparent substrate 20, the semi-transmissive film 30, the etching stopper film 40, and the light shielding film 50 that constitute the photomask blank 10 of the first embodiment will be described below.

The transparent substrate 20 is transparent to exposure light. The transparent 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 transparent substrate 20 is made of a material containing silicon and oxygen, and may be 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 be done. When the transparent substrate 20 is made of low-thermal-expansion glass, positional change of the semi-transmissive film pattern due to thermal deformation of the transparent substrate 20 can be suppressed. The transparent substrate 20 used for the display device is generally a rectangular substrate with a short side length of 300 mm or more. The present invention can stably transfer a fine transflective film pattern of, for example, less than 2.0 μm formed on a transparent substrate even if the short side of the transparent substrate has a large size of 300 mm or more. It is a photomask blank that can provide a photomask that can be used.

The semi-transmissive film 30 has a function of adjusting the reflectance of light incident from the transparent substrate 20 side (hereinafter sometimes referred to as back surface reflectance) and a function of adjusting the transmittance of exposure light. The semi-permeable film 30 is made of a chromium-based material containing chromium (Cr). More specifically, the chromium-based material is chromium (Cr), or a material containing chromium (Cr) and at least one of oxygen (O), nitrogen (N), and carbon (C). is mentioned. Alternatively, a material containing chromium (Cr) and at least one of oxygen (O), nitrogen (N), and carbon (C), and further containing fluorine (F) can be used. For example, Cr, CrO, CrN, CrF, CrCO, CrCN, CrON, CrCON, and CrCONF are examples of materials that constitute the semi-permeable film 30 .
The semi-transmissive film 30 can be formed by a sputtering method.

The transmittance of the semi-transmissive film 30 with respect to exposure light satisfies the required value for the semi-transmissive film 30 . The transmittance of the semi-transmissive film 30 is preferably 1% or more and 80% or less, more preferably 15% or more and 65%, with respect to light of a predetermined wavelength (hereinafter referred to as representative wavelength) contained in the exposure light. % or less, more preferably 20% or more and 60% or less. That is, when the exposure light is compound light including light in the wavelength range of 313 nm to 436 nm, the semi-transmissive film 30 has the above-described transmittance for light of representative wavelengths included in the wavelength range. For example, when the exposure light is compound light including i-line, h-line and g-line, semi-transmissive film 30 has the above-described transmittance for any one of i-line, h-line and g-line.
The transmittance can be measured using a phase shift amount measuring device or the like.

In order to maintain good transfer characteristics, the rear surface reflectance of the semi-transmissive film 30 is 15% or less, preferably 10% or less, in the wavelength range of 365 nm to 436 nm. Further, when the j-line is included in the exposure light, the rear surface reflectance of the semi-transmissive film 30 is preferably 20% or less, more preferably 17% or less, for light in the wavelength range from 313 nm to 436 nm. More preferably, it should be 15% or less. Further, the rear surface reflectance of the semi-transmissive film 30 is preferably 0.2% or more in the wavelength range of 365 nm to 436 nm, and preferably 0.2% or more for light in the wavelength range of 313 nm to 436 nm.
The back surface reflectance can be measured using a spectrophotometer or the like.

The semi-permeable membrane 30 may be composed of a plurality of layers, or may be composed of a single layer. The semi-permeable membrane 30 composed of a single layer is preferable in that an interface is less likely to be formed in the semi-permeable membrane 30 and the cross-sectional shape can be easily controlled. On the other hand, the semi-permeable film 30 composed of a plurality of layers is preferable in terms of ease of film formation.

The etching stopper film 40 is arranged above the semi-transmissive film 30 and is made of a material that has etching resistance to the etchant that etches the semi-transmissive film 30 (etching selectivity is different from that of the semi-transmissive film 30).
The etching stopper film 40 is composed of a transition metal silicide material containing a transition metal and silicon. Molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), zirconium (Zr), and the like are suitable as transition metals, and molybdenum (Mo) is particularly preferred.
Also, the etching stopper film 40 may contain a light element component such as nitrogen or oxygen. In the transition metal silicide-based material, nitrogen or oxygen, which is a light element component, has the effect of lowering the extinction coefficient, so that the reflectance of the front and back surfaces of the etching stopper film 40 can be effectively reduced. Moreover, the total content of light element components including oxygen and nitrogen contained in the etching stopper film 40 is preferably 15 atomic % or more. More preferably, it is 15 atomic % or more and 60 atomic % or less, and 25 atomic % or more and 50 atomic % or less. In addition, when the etching stopper film 40 contains oxygen, the oxygen content is preferably more than 0 atomic % and 30 atomic % or less in terms of defect quality and chemical resistance.
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.
In addition to oxygen and nitrogen described above, the etching stopper film 40 may contain other light element components such as carbon and helium for the purpose of reducing film stress and controlling the wet etching rate.
The etching stopper film 40 has a function of protecting the semi-transmissive film 30 .
The etching stopper film 40 can be formed by a sputtering method.

This etching stopper film 40 preferably has a columnar structure. This columnar structure can be confirmed by cross-sectional SEM observation of the etching stopper film 40 . That is, in the columnar structure of the present invention, the particles of the transition metal silicide compound containing the transition metal and silicon forming the etching stopper film 40 are directed in the film thickness direction of the etching stopper film 40 (the direction in which the particles are deposited). It refers to the state of having a columnar grain structure that extends along the length of the grain. In the present application, particles whose length in the film thickness direction is longer than the length in the vertical direction are defined as columnar particles. That is, the etching stopper film 40 has columnar particles extending in the film thickness direction over the surface of the transparent substrate 20 . In addition, the etching stopper film 40 has a sparse portion having a relatively lower density than the columnar particles (hereinafter sometimes simply referred to as “sparse portion”) by adjusting film formation conditions (sputtering pressure, etc.). is also formed. The etching stopper film 40 effectively suppresses side etching during wet etching and further improves the cross-sectional shape of the pattern. It is preferable that the elongated columnar particles are formed irregularly in the film thickness direction. More preferably, the columnar particles of the etching stopper film 40 are not uniform in length in the film thickness direction. The sparse portions of the etching stopper film 40 are preferably formed continuously in the film thickness direction. Moreover, it is preferable that the sparse portions of the etching stopper film 40 are intermittently formed in the direction perpendicular to the film thickness direction. By forming the etching stopper film 40 into the above-described columnar structure, the wet etching solution can easily permeate the etching stopper film 40 in the film thickness direction during wet etching using a wet etching solution. It is faster, and the wet etching time can be greatly shortened. Since the etching stopper film 40 has a columnar structure extending in the film thickness direction, side etching during wet etching is suppressed, so that the cross-sectional shape of the pattern is improved.

The atomic ratio of the transition metal and silicon contained in the etching stopper film 40 is preferably transition metal:silicon=1:3 or more and 1:15 or less. Within this range, the effect of suppressing a decrease in the wet etching rate during pattern formation of the etching stopper film 40 by the columnar structure can be enhanced. Moreover, the cleaning resistance of the etching stopper film 40 can be improved, and the transmittance can be easily increased. From the viewpoint of increasing the cleaning resistance of the etching stopper film 40, the atomic ratio of the transition metal and silicon contained in the etching stopper film 40 is transition metal:silicon = 1:4 or more and 1:15 or less, more preferably transition metal: It is desirable that the silicon ratio is 1:5 or more and 1:15 or less.

When the semi-transmissive portion of a photomask is composed of a laminated film of the semi-transmissive film 30 and the etching stopper film 40, the transmittance of the etching stopper film 40 with respect to the exposure light is at a predetermined wavelength included in the exposure light. It is preferably 1% or more and 80% or less, more preferably 15% or more and 65% or less, and still more preferably 20% or more and 60% or less with respect to light (hereinafter referred to as representative wavelength). That is, when the exposure light is compound light including light in the wavelength range of 313 nm to 436 nm, the etching stopper film 40 has the above-described transmittance for light of representative wavelengths included in the wavelength range. For example, if the exposure light is compound light including i-line, h-line and g-line, etching stopper film 40 has the above-described transmittance for any one of i-line, h-line and g-line.
The transmittance can be measured using a phase shift amount measuring device or the like.
Further, when the semi-transmissive portion in the photomask is composed of the semi-transmissive film 30, the etching stopper film 40 functions as part of the light-shielding portion in the photomask. Therefore, in this case, the transmittance of the etching stopper film 40 with respect to the exposure light is preferably 10% or less with respect to light of a predetermined wavelength (hereinafter referred to as representative wavelength) contained in the exposure light. More preferably, it is 5% or less, still more preferably 1% or less.

This etching stopper film 40 may be composed of a plurality of layers, or may be composed of a single layer. The etching stopper film 40 composed of a single layer is preferable in that an interface is less likely to be formed in the etching stopper film 40 and the cross-sectional shape can be easily controlled. On the other hand, the etching stopper film 40 composed of a plurality of layers is preferable in terms of ease of film formation.
The thickness of the etching stopper film 40 is sufficient as long as it functions as an etching stopper, and is preferably 3 nm or more, more preferably 5 nm or more, in order to achieve a sufficient etching stopper function within the substrate surface. It is preferably 10 nm or more, and more preferably 10 nm or more. Further, when the etching stopper film is patterned by wet etching, it is preferably 100 nm or less, more preferably 60 nm or less, and 40 nm or less from the viewpoint of suppressing excessive over-etching in order to prevent the etching stopper film from remaining. is more preferable. That is, the thickness of the etching stopper film 40 is preferably 3 nm or more and 100 nm or less, more preferably 5 nm or more and 60 nm or less, and even more preferably 10 nm or more and 40 nm or less.

The light-shielding film 50 is arranged on the upper side of the etching stopper film 40 and is made of a material having etching resistance to the etching solution for etching the etching stopper film 40 (etching selectivity different from that of the etching stopper film 40). Further, the light shielding film 50 may have a function of blocking the transmission of the exposure light, and furthermore, the film surface reflectance of the etching stopper film 40 with respect to the light incident from the etching stopper film 40 side is 350 nm to 436 nm. It may have a function of reducing the film surface reflectance to 15% or less in the region. The light shielding film 50 is made of a chromium-based material containing chromium (Cr). More specifically, the chromium-based material is chromium (Cr), or a material containing chromium (Cr) and at least one of oxygen (O), nitrogen (N), and carbon (C). is mentioned. Alternatively, a material containing chromium (Cr) and at least one of oxygen (O), nitrogen (N), and carbon (C), and further containing fluorine (F) can be used. For example, Cr, CrO, CrN, CrF, CrCO, CrCN, CrON, CrCON, and CrCONF can be used as materials forming the light shielding film 50 .
The light shielding film 50 can be formed by a sputtering method.

The light-shielding film 50 has a function of blocking the transmission of exposure light, and the optical density to the exposure light in the portion where the semi-transmissive film 30, the etching stopper film 40, and the light-shielding film 50 are laminated is preferably 3 or more, and more preferably. is 3.5 or more, more preferably 4 or more.
Optical density can be measured using a spectrophotometer, an OD meter, or the like.

The light-shielding film 50 may be composed of a single film having a uniform composition according to its function, may be composed of a plurality of films having different compositions, or may be composed of films having a continuous composition in the thickness direction. It may also be a case of a single film that changes dynamically.

Note that the photomask blank 10 shown in FIG. The present invention can also be applied to blanks.

Next, a method for manufacturing the photomask blank 10 of the first embodiment will be described.
First, the transparent substrate 20 is prepared. The transparent substrate 20 is made of any glass material, such as synthetic quartz glass, quartz glass, aluminosilicate glass, soda lime glass, low thermal expansion glass (SiO ₂ —TiO ₂ glass, etc.), as long as it is transparent to exposure light. It may be

Next, a semitransparent film 30 is formed on the transparent substrate 20 by sputtering. Semi-transmissive film 30 is preferably formed using an in-line sputtering apparatus. When the sputtering apparatus is an in-line sputtering apparatus, the thickness of the semi-transmissive film 30 can also be controlled by the transport speed of the transparent substrate 20 .
The semi-transparent film 30 is formed using a sputtering target containing chromium or a chromium compound (chromium oxide, chromium nitride, chromium carbide, chromium oxynitride, chromium carbide oxide, chromium carbide oxynitride, etc.), for example, helium gas. , a sputtering gas atmosphere consisting of an inert gas containing at least one selected from the group consisting of neon gas, argon gas, krypton gas and xenon gas, or a group consisting of helium gas, neon gas, argon gas, krypton gas and xenon gas and an active gas containing at least one selected from the group consisting of oxygen gas, nitrogen gas, nitrogen monoxide gas, nitrogen dioxide gas, carbon dioxide gas, hydrocarbon-based gas, and fluorine-based gas is performed in a sputtering gas atmosphere consisting of a mixed gas of Hydrocarbon gases include, for example, methane gas, butane gas, propane gas, and styrene gas.

When the semi-permeable film 30 is composed of a single film with a uniform composition, the film forming process described above is performed only once without changing the composition and flow rate of the sputtering gas. When the semi-permeable film 30 is composed of a plurality of films with different compositions, the film formation process described above is performed a plurality of times while changing the composition and flow rate of the sputtering gas for each film formation process. When the semi-permeable film 30 is composed of a single film whose composition changes continuously in the thickness direction, the film forming process described above is repeated while changing the composition and flow rate of the sputtering gas with the elapsed time of the film forming process. do it only once.

Next, an etching stopper film 40 is formed on the semitransparent film 30 by sputtering.
The etching stopper film 40 is formed using a transition metal silicide target containing a transition metal and silicon, which are the main components of the material constituting the etching stopper film 40, or a transition metal silicide target containing a transition metal, silicon, oxygen and/or nitrogen. is used as a sputtering target, for example, a sputtering gas atmosphere consisting of an inert gas containing at least one selected from the group consisting of helium gas, neon gas, argon gas, krypton gas and xenon gas, or the inert gas, The sputtering is performed in a sputtering gas atmosphere consisting of a mixed gas with an active gas containing at least oxygen and nitrogen selected from the group consisting of oxygen gas, nitrogen gas, carbon dioxide gas, nitrogen monoxide gas and nitrogen dioxide gas. The etching stopper film 40 is formed at a gas pressure of 0.7 Pa or more and 3.0 Pa or less in the film forming chamber during sputtering. Preferably, the etching stopper film 40 is formed at a gas pressure of 0.8 Pa or more and 3.0 Pa in the film forming chamber during sputtering. By setting the gas pressure range in this manner, the etching stopper film 40 can be formed with a columnar structure. This columnar structure can suppress side etching during pattern formation, which will be described later, and achieve a high etching rate. Here, the atomic ratio of the transition metal and silicon in the transition metal silicide target is transition metal:silicon = 1:3 or more and 1:15 or less. This is preferable in that the resistance to washing of the etching stopper film 40 can be increased and the transmittance can be easily increased.

The composition and thickness of the etching stopper film 40 are adjusted so that the etching stopper film 40 has the above functions. The composition of the etching stopper film 40 can be controlled by the content ratio of the elements constituting the sputtering target (for example, the ratio of the transition metal content to the silicon content), the composition and flow rate of the sputtering gas, and the like. The thickness of the etching stopper film 40 can be controlled by sputtering power, sputtering time, and the like. Also, the etching stopper film 40 is preferably formed using an in-line sputtering apparatus. When the sputtering apparatus is an in-line sputtering apparatus, the thickness of the etching stopper film 40 can also be controlled by the transport speed of the substrate. When the transition metal silicide-based material of the etching stopper film 40 contains a light element component containing at least one of nitrogen and oxygen, the etching stopper film 40 contains a light element component containing at least one of oxygen and nitrogen. is controlled to be 15 atomic % or more and 60 atomic % or less.

When the etching stopper film 40 is composed of a single film, the film formation process described above is performed only once by appropriately adjusting the composition and flow rate of the sputtering gas. When the etching stopper film 40 is composed of a plurality of films with different compositions, the film formation process described above is performed a plurality of times while appropriately adjusting the composition and flow rate of the sputtering gas. The etching stopper film 40 may be formed using targets having different content ratios of the elements constituting the sputtering target. When the film formation process is performed multiple times, the sputtering power applied to the sputtering target may be changed for each film formation process.

The etching stopper film 40 contains oxygen such as a transition metal silicide oxide containing a transition metal, silicon and oxygen, or a transition metal silicide oxynitride containing a transition metal, silicon, oxygen and nitrogen. When the etching stopper film 40 is made of a transition metal silicide material, the surface of the etching stopper film 40 is subjected to surface treatment for adjusting the state of surface oxidation of the etching stopper film 40 in order to suppress penetration of the etchant due to the presence of oxides of transition metals. You may make it carry out a process. When the etching stopper film 40 is composed of a transition metal, silicon, and a transition metal silicide nitride containing nitrogen, the transition metal oxide content is higher than that of the transition metal silicide material containing oxygen. is small. Therefore, when the material of the etching stopper film 40 is a transition metal silicide nitride, the above surface treatment process may or may not be performed.
Examples of the surface treatment process for adjusting the state of surface oxidation of the etching stopper film 40 include a method of surface treatment with an acidic aqueous solution, a method of surface treatment with an alkaline aqueous solution, and a method of dry treatment such as ashing. .

Surface treatment for adjusting the state of surface oxidation of the surface of the etching stopper film 40 is performed as necessary, and then the light shielding film 50 is formed on the etching stopper film 40 by sputtering. The light shielding film 50 is preferably formed using an in-line sputtering apparatus. When the sputtering apparatus is an in-line sputtering apparatus, the thickness of the light shielding film 50 can also be controlled by the transport speed of the transparent substrate 20 .
The light-shielding film 50 is formed using a sputtering target containing chromium or a chromium compound (chromium oxide, chromium nitride, chromium carbide, chromium oxynitride, chromium carbide oxide, chromium carbide oxynitride, etc.), for example, helium gas, A sputtering gas atmosphere composed of an inert gas containing at least one selected from the group consisting of neon gas, argon gas, krypton gas and xenon gas, or selected from the group consisting of helium gas, neon gas, argon gas, krypton gas and xenon gas An inert gas containing at least one type and an active gas containing at least one type selected from the group consisting of oxygen gas, nitrogen gas, nitrogen monoxide gas, nitrogen dioxide gas, carbon dioxide gas, hydrocarbon-based gas, and fluorine-based gas. It is carried out in a sputtering gas atmosphere consisting of a mixed gas. Hydrocarbon gases include, for example, methane gas, butane gas, propane gas, and styrene gas. By adjusting the gas pressure in the deposition chamber during sputtering, the light-shielding film 50 can be formed into a columnar structure like the etching stopper film 40 . As a result, side etching during pattern formation, which will be described later, can be suppressed, and a high etching rate can be achieved.

When the light-shielding film 50 is composed of a single film with a uniform composition, the above-described film formation process is performed only once without changing the composition and flow rate of the sputtering gas. When the light-shielding film 50 is composed of a plurality of films with different compositions, the film formation process described above is performed a plurality of times while changing the composition and flow rate of the sputtering gas for each film formation process. When the light-shielding film 50 is composed of a single film whose composition changes continuously in the thickness direction, the film formation process described above is repeated once while changing the composition and flow rate of the sputtering gas with the elapsed time of the film formation process. only do
Thus, the photomask blank 10 of Embodiment 1 is obtained.
When manufacturing a photomask blank having a resist film on the light shielding film 50 , the resist film is formed on the light shielding film 50 .

In the photomask blank 10 of Embodiment 1, the light shielding film 50 is formed on the etching stopper film 40, and at least the etching stopper film 40 has a columnar structure.
When the etching stopper film 40 is patterned by wet etching, the photomask blank 10 of the first embodiment promotes etching in the film thickness direction while suppressing side etching. Therefore, an etching stopper film pattern having a good cross-sectional shape and a desired transmittance (for example, a high transmittance) can be formed without excessive over-etching. Therefore, it is possible to obtain a photomask blank from which a photomask capable of accurately transferring a transfer pattern with high in-plane uniformity of transmittance can be manufactured.

Embodiment 2.
In Embodiment 2, a method for manufacturing a photomask will be described.

FIG. 2 is a schematic diagram showing a method of manufacturing a photomask according to the second embodiment.
The photomask manufacturing method shown in FIG. 2 is a method of manufacturing a photomask 100 using the photomask blank 10 shown in FIG.
Each step of the photomask manufacturing process according to the second embodiment will be described in detail below.

1. First Resist Film Pattern Forming Step In the first resist film pattern forming step, first, a first resist film is formed on the light shielding film 50 of the photomask blank 10 of the first embodiment. The resist film material to be used is not particularly limited. For example, in the case of drawing on a resist film with a laser drawing device, any laser light having a wavelength selected from a wavelength range of 350 nm to 436 nm, which will be described later, may be used. Also, the first resist film may be either positive type or negative type. The same applies to the second resist film 70, which will be described later.
After that, a desired pattern is drawn on the first resist film using a laser beam having a wavelength selected from a wavelength range of 350 nm to 436 nm. The pattern to be drawn on the first resist film is the pattern that will later become the transmissive portion and the light shielding portion, and is the pattern to be formed on the light shielding film 50 , the etching stopper film 40 and the semi-transmissive film 30 . The pattern to be drawn on the second resist film 70 to be described later is the pattern of the semi-transmissive portion and the light shielding portion, which is the pattern to be formed on the light shielding film 50 and the etching stopper film 40 . Examples of patterns to be drawn on the first resist film and the second resist film 70 include a line-and-space pattern and a hole pattern.
Thereafter, the resist film is developed with a predetermined developer to form a first resist film pattern 60a on the light shielding film 50 as shown in FIG. 2(a).

2. First Light-Shielding Film Pattern Forming Step In the first light-shielding film pattern forming step, first, the light-shielding film 50 is etched using the first resist film pattern 60a as a mask to form the first light-shielding film pattern 50a. The light shielding film 50 is made of a chromium-based material containing chromium (Cr). When the light shielding film 50 has a columnar structure, the etching rate is high and side etching can be suppressed, which is preferable. The etchant for etching the light shielding film 50 is not particularly limited as long as it can selectively etch the light shielding film 50 . Specifically, an etchant containing ceric ammonium nitrate and perchloric acid is mentioned.

3. First etching stopper film pattern forming process In the first etching stopper film pattern forming process, the etching stopper film 40 is wet-etched using the first resist film pattern 60a as a mask, as shown in FIG. 2(c). Then, a first etching stopper film pattern 40a is formed. The etchant for etching the etching stopper film 40 is not particularly limited as long as it can selectively etch the etching stopper film 40 . For example, an etchant containing ammonium fluoride, phosphoric acid and hydrogen peroxide, and an etchant containing ammonium hydrogen fluoride and hydrogen peroxide can be used.
The wet etching is performed for a time longer than the time (just etching time) until the semitransparent film 30 is exposed in the first etching stopper film pattern 40a in order to improve the cross-sectional shape of the first etching stopper film pattern 40a. (over-etching time) is preferable. The over-etching time is preferably within the just etching time plus 20% of the just etching time in consideration of suppression of side etching, etc., and 10% of the just etching time is added. It is more preferable to set it within the specified time.

4. Semi-transmissive Film Pattern Forming Step In the semi-transmissive film pattern forming step, the semi-transmissive film 30 is wet-etched using the first etching stopper film pattern 40a as a mask to form a semi-transmissive film as shown in FIG. A pattern 30a is formed. The semi-transmissive film 30 is made of a chromium-based material containing chromium (Cr). If the semitransparent film 30 has a columnar structure, the etching rate is high and side etching can be suppressed, which is preferable. The etchant for etching the semi-transmissive film 30 is not particularly limited as long as it can selectively etch the semi-transmissive film 30 . Specifically, an etchant containing ceric ammonium nitrate and perchloric acid is mentioned.

5. Step of Stripping First Resist Film Pattern After that, as shown in FIG. 2E, the first resist film pattern 60a is stripped using a resist stripper or by ashing.
Through the steps shown in FIGS. 2(a) to 2(e), a pattern to be a transmission portion is formed.

6. Second Resist Film Pattern Forming Step In the second resist film pattern forming step, first, as shown in FIG. 2(f), a second resist film 70 is formed to cover the first light shielding film pattern 50a. As with the first resist film, the resist film material to be used is not particularly limited.
After that, a desired pattern is drawn on the second resist film 70 using laser light having a wavelength selected from a wavelength range of 350 nm to 436 nm. The pattern drawn on the second resist film 70 is a pattern consisting of a semi-transmissive portion and a light-shielding portion.
Thereafter, the resist film is developed with a predetermined developer to form a second resist film pattern 70b on the first light shielding film pattern 50a, as shown in FIG. 2(g).

7. Second light shielding film pattern forming process In the second light shielding film pattern forming process, the first light shielding film pattern 50a is etched using the second resist film pattern 70b as a mask, as shown in FIG. 2(h). Then, a second light shielding film pattern 50b is formed. The etchant for etching the second light shielding film pattern 50b is the same as that described in the first light shielding film pattern forming step.

8. Second Etching Stopper Film Pattern Forming Step In the second etching stopper film pattern forming step, the first etching stopper film pattern 40a is wet-etched using the second light shielding film pattern 50b as a mask, thereby forming the pattern shown in FIG. , a second etching stopper film pattern 40b is formed. The etchant for etching the etching stopper film 40 is the same as that described in the first etching stopper film pattern forming step. Also, the over-etching time is the same as that described in the first etching stopper film pattern forming step.

9. Step of Stripping First Resist Film Pattern After that, as shown in FIG. 2(j), the second resist film pattern 70b is stripped using a resist stripper or by ashing.
Through the steps shown in FIGS. 2(f) to 2(i), a pattern to be a semi-transmissive portion is formed. A region other than the transmissive portion and the semi-transmissive portion becomes a light shielding portion.
Thus, a photomask 100 is obtained.
In the above description, among the transfer patterns, the pattern to be the transmissive portion was formed first (FIGS. 2(a) to 2(e)), and then the pattern to be the semi-transmissive portion and the light shielding portion was formed. (FIGS. 2(f) to 2(j)) are not limited to this. For example, a pattern to be a semi-transmissive portion may be formed first, and then a pattern to be a transmissive portion or a light-shielding portion may be formed. Further, in the above description, the resist film is formed twice, but the thickness of the resist film at the position corresponding to the transmissive part is made thicker than the position corresponding to the semi-transmissive part, and the resist film is formed once. A pattern to be a semi-transmissive portion and a pattern to be a transmissive portion may be formed at the same time.

According to the photomask manufacturing method of the second embodiment, since the photomask blank of the first embodiment is used, the transmissive portion has a sufficient transmittance, and the surface of the transmittance can be obtained without excessive over-etching. A highly uniform transfer pattern can be formed. A photomask manufactured in this way can correspond to miniaturization of line-and-space patterns and contact holes.

Embodiment 3.
In Embodiment 3, a method for manufacturing a display device will be described. The display device uses the photomask 100 manufactured using the photomask blank 10 described above, or uses the photomask 100 manufactured by the method for manufacturing the photomask 100 described above (mask placement step); A process (exposure process) of exposing and transferring a transfer pattern onto a resist film on a device is performed.
Each step will be described in detail below.

1. Mounting Step In the mounting step, the photomask manufactured in the second embodiment is 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 100 is irradiated with exposure light to transfer the transfer pattern to the resist film formed on the display device substrate. The exposure light is compound light containing light of a plurality of wavelengths selected from a wavelength range of 365 nm to 436 nm, or monochromatic light selected by cutting a certain wavelength range from the wavelength range of 365 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, 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, it is possible to manufacture a high-definition display device having high resolution and fine line-and-space patterns and contact holes.
In the above embodiments, the case of using a photomask having a semi-transmissive film as a photomask having a transfer pattern has been described, but the present invention is not limited to this. For example, the present invention can be applied to a phase shift mask blank in which a semi-transmissive film has a phase shift function and a phase shift mask having a phase shift mask film pattern.

Example 1.
A. Photomask Blank and Manufacturing Method Thereof To manufacture the photomask blank of Example 1, first, a synthetic quartz glass substrate of 1214 size (1220 mm×1400 mm) was prepared as the transparent substrate 20 .

After that, the synthetic quartz glass substrate was placed on a tray (not shown) with the main surface facing downward, and carried into the chamber of an in-line sputtering apparatus.
In order to form the semi-transmissive film 30 on the main surface of the transparent substrate 20, first, the transparent substrate 20 is carried into the first chamber, and argon (Ar) gas and nitrogen (N ₂ ) gas are introduced into the first chamber. A mixed gas (Ar: 40 sccm, N ₂ : 35 sccm) was introduced. The sputtering gas pressure in the first chamber was 0.4 Pa. Then, by applying a sputtering power of 1.5 kW to the first sputtering target made of chromium, chromium and nitrogen are contained on the transparent substrate 20 by reactive sputtering so that the transmittance at a wavelength of 405 nm becomes 30%. Chromium nitride (CrN) was deposited to form a semitransparent film 30 with a thickness of 10.6 nm.

Next, the transparent substrate 20 with the semi-transmissive film 30 was carried into the second chamber, and with the sputtering gas pressure in the second chamber set to 1.6 Pa, argon (Ar) gas and nitrogen (N ₂ ) were discharged. A gas and an inert gas composed of helium (He) gas (Ar: 18 sccm, N ₂ : 13 sccm, He: 50 sccm) were introduced. Then, a second sputtering target containing molybdenum and silicon (molybdenum:silicon=1:9) was applied with a sputtering power of 7.6 kW, and molybdenum, silicon and nitrogen were contained on the semitransparent film 30 by reactive sputtering. A nitride of molybdenum silicide was deposited to form an etching stopper film 40 having a thickness of 40 nm.

Next, the transparent substrate 20 with the etching stopper film 40 is carried into the third chamber, and mixed gas of argon (Ar) gas and nitrogen (N ₂ ) gas (Ar: 65 sccm, N ₂ : 15 sccm) was introduced. Then, a chromium nitride (CrN) containing chromium and nitrogen was formed on the etching stopper film 40 by reactive sputtering by applying a sputtering power of 1.5 kW to a third sputtering target made of chromium (thickness: 15 nm). Next, a mixed gas (30 sccm) of argon (Ar) gas and methane (CH ₄ : 4.9%) gas was introduced into the fourth chamber with a predetermined degree of vacuum, and a fourth sputtering made of chromium was introduced. A sputtering power of 8.5 kW was applied to the target to form chromium carbide (CrC) containing chromium and carbon on CrN by reactive sputtering (thickness: 60 nm). Finally, with the inside of the fifth chamber having a predetermined degree of vacuum, mixed gas of argon (Ar) gas and methane (CH ₄ : 5.5%) gas, nitrogen (N ₂ ) gas, and oxygen (O ₂ ) were mixed. A mixed gas (Ar + CH ₄ : 30 sccm, N ₂ : 8 sccm, O ₂ : 3 sccm) was introduced, and a sputtering power of 2.0 kW was applied to the fifth sputtering target made of chromium to form a film on CrC by reactive sputtering. A chromium carbooxynitride (CrCON) containing chromium, carbon, oxygen and nitrogen was formed on the substrate (thickness: 30 nm). As described above, the light-shielding film 50 having a laminated structure of the CrN layer, the CrC layer, and the CrCON layer was formed on the etching stopper film 40 . The gas pressure in the third chamber, the fourth chamber, and the fifth chamber was adjusted from 0.3 Pa to 0.5 Pa to form the films.
Thus, a photomask blank 10 was obtained in which the semi-transmissive film 30, the etching stopper film 40, and the light shielding film 50 were formed on the transparent substrate 20 in this order.
Regarding the photomask blank 10 thus obtained, the optical density of the laminated film of the semi-transmissive film 30, the etching stopper film 40, and the light shielding film 50 was measured and found to be 5.0 at a wavelength of 365 nm.

Further, the obtained photomask blank 10 was subjected to composition analysis in the depth direction by X-ray photoelectron spectroscopy (XPS).
In the composition analysis results in the depth direction of the photomask blank 10 by XPS, the etching stopper film 40 has a substantially constant content of each constituent element in the depth direction, with Mo being 8 atomic % and Si being 40 atomic %. atomic %, N was 48 atomic %, and O was 4 atomic %. Also, the atomic ratio of molybdenum and silicon was 1:5, which was in the range of 1:3 or more and 1:15 or less. Also, the total content of oxygen and nitrogen, which are light elements, was 52 atomic %, which was within the range of 50 atomic % or more and 65 atomic % or less. The reason why the etching stopper film 40 contains oxygen is considered to be that the sputtering gas pressure was as high as 0.8 Pa or higher, and a very small amount of oxygen was present in the chamber during film formation.

Next, a cross-sectional SEM (scanning electron microscope) observation was performed at a magnification of 80000 times at the central position of the transfer pattern formation region of the obtained photomask blank 10. As a result, the etching stopper film 40 had a columnar structure. It was confirmed that That is, it was confirmed that the particles of the molybdenum silicide compound forming the etching stopper film 40 had a columnar particle structure extending in the film thickness direction of the etching stopper film 40 . In the columnar grain structure of the etching stopper film 40, it was confirmed that the columnar grains in the film thickness direction were formed irregularly, and the lengths of the columnar grains in the film thickness direction were also irregular. . It was also confirmed that the sparse portions of the etching stopper film 40 were formed continuously in the film thickness direction.

B. Photomask and its Manufacturing Method In order to manufacture the photomask 100 using the photomask blank 10 manufactured as described above, first, a photoresist is applied onto the light-shielding film 50 of the photomask blank 10 using a resist coating apparatus. A membrane was applied.
Thereafter, a photoresist film having a film thickness of 520 nm was formed through heating and cooling steps.
After that, the photoresist film was drawn using a laser drawing device, developed and rinsed, and a first resist film pattern 60a having a hole pattern with a hole diameter of 1.5 μm was formed on the light shielding film 50 .

Thereafter, using the first resist film pattern 60a as a mask, the light shielding film 50 was wet-etched with a chromium etchant containing ceric ammonium nitrate and perchloric acid to form the first light shielding film pattern 50a.

After that, using the first light shielding film pattern 50a as a mask, the etching stopper film 40 is wet-etched with a molybdenum silicide etching solution obtained by diluting a mixed solution of ammonium hydrogen fluoride and hydrogen peroxide with pure water to form a first mask. An etching stopper film pattern 40a was formed. This wet etching was performed with an over-etching time of 110% in order to make the cross-sectional shape vertical and to form the required fine pattern. The just etching time in Example 1 was 0.2 times as long as the just etching time in Comparative Example described later, and the etching time could be significantly shortened.
Thereafter, using the first etching stopper film pattern 40a as a mask, the semi-transmissive film 30 was wet-etched with a chromium etchant containing ceric ammonium nitrate and perchloric acid to form a semi-transmissive film pattern 30a.
After that, the first resist film pattern 60a is removed.

After that, a second resist film 70 was applied using a resist coating device so as to cover the first light shielding film pattern 50a.
Thereafter, a second resist film 70 having a film thickness of 520 nm is formed through heating and cooling steps.
After that, a second resist film 70 is drawn using a laser lithography device, developed and rinsed, and a second resist for forming a semi-transmissive portion and a light shielding portion is formed on the first light shielding film pattern 50a. A film pattern 70b was formed.

Thereafter, using the second resist film pattern 70b as a mask, the first light shielding film pattern 50a formed in the transfer pattern forming region is wet-etched with a chromium etchant containing ceric ammonium nitrate and perchloric acid. to form a second light shielding film pattern 50b.
Thereafter, using the second light shielding film pattern 50b as a mask, the first etching stopper film pattern 40a is wet-etched with a molybdenum silicide etching solution obtained by diluting a mixed solution of ammonium hydrogen fluoride and hydrogen peroxide with pure water. , a second etching stopper film pattern 40b is formed. This wet etching was also performed with an over-etching time of 110% in order to make the cross-sectional shape vertical and to form the required fine pattern. This just etching time was also 0.2 times as long as the just etching time in the comparative example described later, and the etching time could be greatly shortened.
After that, the second resist film pattern 70b is removed.

In this manner, on the transparent substrate 20, a transmissive portion formed by the semi-transmissive film pattern 30a having a hole diameter of 1.5 μm in the transfer pattern forming region, and a second semi-transmissive film pattern 30a formed on the semi-transmissive film pattern 30a. A photomask 100 having a semi-transmissive portion formed of an etching stopper film pattern 40b and a light-shielding portion having a laminated structure of a semi-transmissive film pattern 30a, a second etching stopper film pattern 40b, and a second light-shielding film pattern 50b. got

In the photomask manufacturing process described above, the etching stopper film pattern and the semi-transmissive film pattern were evaluated.
[Evaluation of etching stopper film pattern]
The cross-sectional shape of the etching stopper film pattern is obtained by wet-etching (110 % over-etching) to form the second etching stopper film pattern 40b, and the cross section of the etching stopper film pattern after the second resist film pattern 70b was peeled off was observed with a cross-sectional SEM photograph.
The cross section of the etching stopper film pattern is composed of the upper surface, lower surface and side surfaces of the etching stopper film pattern. The angle of the cross section of the etching stopper film pattern refers to the angle formed by the portion (upper side) where the upper surface and the side surface of the etching stopper film pattern contact and the portion (lower side) where the side surface and the lower surface contact. The obtained etching stopper film pattern 40b had a cross section with an angle of 74°, and had a cross section shape close to vertical. The reason why the second etching stopper film pattern 40b has a favorable cross-sectional shape by forming the etching stopper film 40 into a columnar structure is considered to be due to the following mechanism. From the observation result of the cross-sectional SEM photograph, the etching stopper film 40 has a columnar grain structure (columnar structure), and the columnar grains extending in the film thickness direction are irregularly formed. Further, from the observation result of the cross-sectional SEM photograph, the etching stopper film 40 is formed of columnar particle portions with relatively high density and sparse portions with relatively low density. From these facts, when the etching stopper film 40 is patterned by wet etching, the etchant permeates the sparse portions of the etching stopper film 40, which facilitates etching in the film thickness direction. In the direction perpendicular to the surface of the substrate (the direction within the substrate surface), columnar particles are irregularly formed, and the sparse portions in this direction are intermittently formed, so etching in this direction is difficult to proceed. It is considered that the second etching stopper film pattern 40b has a good cross-sectional shape that is nearly vertical because the side etching is suppressed by this. In addition, the second etching stopper film pattern 40b did not seep into either the interface with the second light shielding film pattern 50b or the interface with the semi-transmissive film pattern 30a.
Further, from the cross-sectional SEM photograph, no etching stopper film residue was observed on the semitransparent film after etching the etching stopper film by wet etching.
[Evaluation of Semitransparent Film Pattern]
The cross-sectional shape of the etching stopper film pattern is obtained by wet-etching the semi-transmissive film 30 with a chromium etchant using the first etching stopper film pattern 40a as a mask in the photomask manufacturing process of Example 1, thereby forming a semi-transmissive film. After forming the pattern 30a, the cross section of the semi-transmissive film pattern after peeling off the first resist film pattern 60a was observed with a cross-sectional SEM photograph.
As a result, the cross-sectional angle of the semi-transmissive film pattern was 78°, and the cross-sectional shape was nearly vertical.
Further, from the cross-sectional SEM photograph, no semi-transmissive film residue or etching stopper film residue was observed on the transparent substrate 20 serving as the light-transmitting portion. When the transmittance of this light-transmitting portion was measured, it was 100.0% (based on the synthetic quartz glass substrate), which was good. Therefore, the obtained photomask has sufficient transmittance in the light-transmitting portion, does not have semi-transmissive film residue or etching stopper film residue in the light-transmitting portion, and has a transfer pattern with high in-plane uniformity of transmittance. A formable photomask was obtained.
Therefore, when the photomask of Example 1 is set on the mask stage of the exposure apparatus and is exposed and transferred to the resist film on the display device, it can be said that a fine pattern of less than 2.0 μm can be transferred with high accuracy.

Although molybdenum is used as the transition metal in the above-described embodiments, the same effects as those described above can be obtained with other transition metals.
In addition, in the above-described embodiments, examples of photomask blanks for manufacturing display devices and photomasks for manufacturing display devices have been described, but the present invention is not limited to these. The photomask blanks and photomasks of the present invention can also be applied to semiconductor device manufacturing, MEMS manufacturing, printed circuit boards, and the like. The present invention can also be applied to a binary mask blank having a light shielding film or a binary mask having a light shielding film pattern.
Also, in the above embodiment, the size of the transparent substrate is 1214 size (1220 mm×1400 mm×13 mm), but it is not limited to this. In the case of photomask blanks for manufacturing display devices, a large size transparent substrate is used, and the size of the transparent substrate has a side length of 300 mm or more. The size of the transparent substrate used for photomask blanks for manufacturing display devices is, for example, 330 mm×450 mm or more and 2280 mm×3130 mm or less.
In the case of photomask blanks for semiconductor device manufacturing, MEMS manufacturing, and printed circuit board use, a small size transparent substrate is used, and the size of the transparent substrate is 9 inches or less on one side. . The size of the transparent substrate used for the photomask blank for the above application is, for example, 63.1 mm×63.1 mm or more and 228.6 mm×228.6 mm or less. Normally, 6025 size (152 mm x 152 mm) and 5009 size (126.6 mm x 126.6 mm) are used for semiconductor manufacturing and MEMS manufacturing, and 7012 size (177.4 mm x 177.4 mm) is used for printed circuit boards. Alternatively, the 9012 size (228.6 mm×228.6 mm) is used.

Comparative example 1.
A. Photomask Blank and its Manufacturing Method In order to manufacture the photomask blank of Comparative Example 1, as in Example 1, a synthetic quartz glass substrate of 1214 size (1220 mm×1400 mm) was prepared as a transparent substrate.
By the same method as in Example 1, the synthetic quartz glass substrate was carried into the chamber of the in-line sputtering apparatus, and mixed gas of argon (Ar) gas and nitrogen (N ₂ ) gas (Ar: 40 sccm) was introduced into the first chamber. , N ₂ : 35 sccm) were introduced. The sputtering gas pressure in the first chamber was 0.4 Pa. Then, a sputtering power of 1.5 kW was applied to the first sputtering target made of chromium, and a chromium containing chromium and nitrogen was deposited on the transparent substrate by reactive sputtering so that the transmittance at a wavelength of 405 nm was 30%. Nitride (CrN) was deposited to form a semi-transparent film with a thickness of 10.6 nm in the same manner as in Example 1.
Next, a mixed gas of argon (Ar) gas and nitrogen (N ₂ ) gas (Ar: 30 sccm, N ₂ : 30 sccm) was introduced while the sputtering gas pressure in the second chamber was set to 0.5 Pa. Then, a second sputtering target containing molybdenum and silicon (molybdenum:silicon=1:9) was applied with a sputtering power of 7.6 kW to form molybdenum, silicon and nitrogen on the main surface of the transparent substrate by reactive sputtering. A nitride containing molybdenum silicide was deposited. Thus, an etching stopper film having a thickness of 40 nm was formed.
After that, the same method as in Example 1 was used to form a light shielding film.
Thus, a photomask blank was obtained in which a semi-transmissive film, an etching stopper film, and a light shielding film were formed in this order on a transparent substrate.
Regarding the photomask blank thus obtained, the optical density of the laminated film of the semi-transmissive film, the etching stopper film and the light shielding film was measured and found to be 5.0 at a wavelength of 365 nm.

Further, the obtained photomask blank was subjected to composition analysis in the depth direction by X-ray photoelectron spectroscopy (XPS). As a result, in the etching stopper film, the content rate of each constituent element is almost constant in the depth direction, and Mo is 8 atomic %, Si is 39 atomic %, N is 52 atomic %, and O is 1 atomic %. Met. Also, the atomic ratio of molybdenum and silicon was 1:4.9, which was within the range of 1:3 or more and 1:15 or less. In addition, the total content of light elements such as oxygen, nitrogen and carbon was 53 atomic %, which was within the range of 50 atomic % or more and 65 atomic % or less.

Next, cross-sectional SEM observation was performed at a magnification of 80,000 times at the center position of the transfer pattern forming region of the obtained photomask blank. Alternatively, it was confirmed that it had an amorphous structure.

B. Photomask and its Manufacturing Method A photomask was manufactured in the same manner as in Example 1 using the photomask blank manufactured as described above. Wet etching to the etching stopper film was performed with an over-etching time of 110% in order to make the cross-sectional shape vertical and to form a required fine pattern. The just etching time in Comparative Example 1 was 40 minutes, which was a long time.
As in Example 1 described above, the etching stopper film pattern and the semi-transmissive film pattern were evaluated in the photomask manufacturing process.
[Evaluation of etching stopper film pattern]
The cross section of the etching stopper film pattern had an angle of 55°, and the pattern cross section was worse than in Example 1.
Further, from the cross-sectional SEM photograph, clear film residues of the etching stopper were observed on the semi-transmissive film in a plurality of regions.
[Evaluation of Semitransparent Film Pattern]
The cross-sectional angle of the semitransparent film pattern was 78°, which was almost the same as in Example 1.
Further, from the cross-sectional SEM photograph, clear film residues of the semi-transmissive film and the etching stopper film were observed in a plurality of regions on the transparent substrate 20 that will be the light-transmitting portions. When the transmittance of this light-transmitting portion was measured, it was 87% (based on the synthetic quartz glass substrate), and a region where the transmittance was remarkably lowered was observed. Therefore, in the obtained photomask, there was a region having insufficient transmittance in the light-transmitting portion, resulting in a transferred pattern with low in-plane uniformity of transmittance.
Therefore, when the photomask of Comparative Example 1 is set on the mask stage of an exposure apparatus and is exposed and transferred to a resist film on a display device, it is expected that a fine pattern of less than 2.0 μm cannot be transferred.

DESCRIPTION OF SYMBOLS 10... Photomask blank, 20... Transparent substrate, 30... Semi-transmissive film,
30a... Semitransparent film pattern, 40... Etching stopper film,
40a... First etching stopper film pattern,
40b... second etching stopper film pattern, 50... light shielding film,
50a... first light shielding film pattern, 50b... second light shielding film pattern,
60a... first resist film pattern, 70... second resist film,
70b... second resist film pattern, 100... photomask

Claims (8)

A photomask blank having a semi-transmissive film, an etching stopper film, and a light shielding film in this order on a transparent substrate,
The photomask blank is an original plate for forming a photomask having a transfer pattern on a transparent substrate by wet etching,
the semi-transmissive film and the light-shielding film contain chromium,
The etching stopper film contains a transition metal and silicon,
A photomask blank, wherein the etching stopper film has a columnar structure. 2. The photomask blank according to claim 1, wherein an atomic ratio of said transition metal and said silicon contained in said etching stopper film is transition metal:silicon=1:3 or more and 1:15 or less. 3. The photomask blank of claim 1, wherein the transition metal is molybdenum. A method for manufacturing a photomask blank having a semi-transmissive film, an etching stopper film, and a light shielding film in this order on a transparent substrate,
The semi-transmissive film and the light-shielding film are formed by sputtering using a target containing chromium in a deposition chamber,
The etching stopper film is formed by using a transition metal silicide target containing a transition metal and silicon in a deposition chamber, and forming the sputtering gas pressure in the deposition chamber to which the sputtering gas is supplied at a pressure of 0.7 Pa or more and 3.0 Pa or less. A method of manufacturing a photomask blank, characterized by: 5. The method of manufacturing a photomask blank according to claim 4, wherein the atomic ratio of said transition metal and silicon in said transition metal silicide target is transition metal:silicon=1:3 or more and 1:15 or less. 6. The method of manufacturing a photomask blank according to claim 4, wherein the semi-transmissive film, the etching stopper film, and the light shielding film are formed using an in-line sputtering apparatus. preparing the photomask blank according to any one of claims 1 to 3 or the photomask blank manufactured by the method for manufacturing a photomask blank according to any one of claims 4 to 6;
The semi-transmissive film, the etching stopper film, and the light-shielding film are each patterned by wet etching to form a transmissive portion that transmits exposure light, a semi-transmissive portion that partially transmits exposure light, and a light-blocking portion that blocks exposure light. and a step of forming a transfer pattern having a light-shielding portion. A photomask obtained by the photomask manufacturing method according to claim 7 is placed on a mask stage of an exposure apparatus, and the transfer pattern formed on the photomask is transferred to a resist formed on a display device substrate. A method of manufacturing a display device, comprising an exposure step of exposing and transferring the substrate to the substrate.

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