TW202141172A - Photomask blank and method of manufacturing photomask, and method of manufacturing display device - Google Patents

Abstract

The present invention provides a photomask blank capable of manufacturing a photomask having the following optical properties. The above-mentioned optical properties include an excellent precision in patterning a light-blocking film can realize a higher pattern accuracy when the pattern is transferred by exposure. The photomask blank of the present invention is used when manufacturing the photomask for manufacturing a display device and includes a transparent substrate and a light-blocking film disposed on the transparent substrate. The light-blocking film includes a first reflection-suppressing layer, a light-blocking layer, and a second reflection-suppressing layer in a sequence from the side of the transparent substrate. The first reflection-suppressing layer includes a first low chromium oxide layer having a relatively low ratio of oxygen to nitrogen and a first high chromium oxide layer having a relatively high ratio of oxygen to nitrogen in a sequence from the side of the transparent substrate. The second reflection-suppressing layer includes a second low chromium oxide layer having a relatively low ratio of oxygen to nitrogen and a second high chromium oxide layer having a relatively high ratio of oxygen to nitrogen in a sequence from the side of transparent substrate. The composition and film thickness of the first reflection-suppressing layer, the light-blocking layer, and the second reflection-suppressing layer are set so that the reflectance of the front and back surfaces of the light-blocking film with respect to the exposure wavelength of the exposure light from 300 nm to 436 nm is 15% or less and the optical density is 3.0 or more. The first reflection-suppressing layer and the second reflection-suppressing layer contain carbon, respectively. The method for manufacturing a photomask comprises the steps of preparing a photomask blank, forming a resist film on the light-blocking film, etching the light-blocking film by using the resist pattern formed by the resist film as a mask, and forming a light- blocking film pattern on the transparent substrate.

Description

Mask base and mask manufacturing method, and display device manufacturing method

The present invention relates to a manufacturing method of a photomask substrate and a photomask, and a manufacturing method of a display device.

In display devices such as FPD (Flat Panel Display) represented by LCD (Liquid Crystal Display), large screens, wide viewing angles, high-definition, and high-speed displays are rapidly developing. One of the elements necessary to realize this high-definition and high-speed display is the production of electronic circuit patterns such as components or wirings with fine and high dimensional accuracy. The patterning of the electronic circuit for the display device mostly uses the photolithography method. Therefore, there is a need for a mask for manufacturing display devices with fine and high-precision patterns formed.

The photomask for manufacturing the display device is made from the photomask substrate. The mask base is formed by arranging a light-shielding film made of a material that is opaque to exposure light on a transparent substrate including synthetic quartz glass and the like. For example, as shown in Patent Document 1, in a photomask base or a photomask, in order to suppress the use of the photomask to expose the panel of the transferee, the reflected light from the transferee is reflected on the surface of the photomask and reflected again to the surface of the photomask. To be transferred, anti-reflection films are provided on the front and back sides of the light-shielding film, and the mask base is composed of, for example, the following film composition, that is, a back anti-reflection film, a light-shielding film, and a reflection attenuation film are sequentially laminated from the transparent substrate side And anti-reflective film. The photomask is made by patterning each film constituting the photomask base by wet etching or the like to form a specific light-shielding film pattern. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Korean Registered Patent No. 10-1473163

[The problem to be solved by the invention]

Therefore, in the photomask substrate, when the photomask is patterned by etching to form the photomask, the precision of the photomask pattern is required to be high. The reason is that if the accuracy of the light-shielding film pattern is low, when the light-shielding film pattern is transferred to the transferred body using the mask, the line width of the transfer pattern or the size of the hole pattern becomes uneven, which is detrimental. CD (Critical Dimension) Uniformity of the pattern formed on the transferred body.

In addition, the reflectivity of the front surface of the light-shielding film of the mask substrate is also required to be low, so that the high-precision transfer pattern can be transferred when the mask is used to expose the transferred body. If the reflectivity of the front surface of the light-shielding film pattern formed on the mask is relatively high, there is a situation where the reflected light from the transferred body is reflected on the front side of the light-shielding film pattern of the mask during the exposure process, so the so-called The flare. In addition, for example, there is a situation in which the light from the exposure device is exposed to light reflected on the back surface of the light-shielding film pattern of the photomask. The reflected light is again reflected by the optical system of the exposure device (transfer device) and enters the photomask again. The so-called back to light. There are cases where the pattern accuracy of the transfer pattern formed by using the photomask is impaired due to the light spots or the back light.

Therefore, the object of the present invention is to provide a photomask substrate with the following optical characteristics: by patterning the light shielding film in the photomask substrate by etching, a high-precision light shielding film pattern can be obtained when the photomask is made, and the photomask is used When the transfer pattern is transferred to the transfer body, the pattern accuracy of the transfer body is improved. [Technical means to solve the problem]

(Structure 1) A photomask substrate, wherein: the production line which displays the mask when the user of device fabrication, and having: a transparent substrate, comprising the exposure of light of substantially transparent material; and a light shielding film, It is provided on the transparent substrate and includes a material that is substantially opaque to the light exposed to the exposure; the light-shielding film includes a first reflection suppression layer, a light-shielding layer, and a second reflection suppression layer from the transparent substrate side, and the first reflection The suppression layer is provided in order from the transparent substrate side: a first low chromium oxide layer containing chromium, oxygen, and nitrogen, and the ratio of oxygen to nitrogen is relatively small; and a first high chromium oxide layer containing chromium, Oxygen and nitrogen, and the ratio of oxygen to nitrogen is relatively high; the second reflection suppression layer is provided in order from the transparent substrate side: a second low chromium oxide layer containing chromium, oxygen and nitrogen, and oxygen relative to The ratio of nitrogen is relatively small; and the second high chromium oxide layer, which contains chromium, oxygen and nitrogen, and the ratio of oxygen to nitrogen is relatively large; Exposure to the light of the above exposure by the front and back of the light-shielding film The composition and film thickness of at least the first reflection suppression layer, the light shielding layer, and the second reflection suppression layer are set so that the reflectance at a wavelength of 300 nm to 436 nm is 15% or less and the optical density becomes 3.0 or more.

(Composition 2) The mask substrate of composition 1, characterized in that: the light-shielding layer is formed of a chromium-based material with a chromium content of 97 atomic% or more and 100 atomic% or less.

(Composition 3) For example, the mask substrate of 1 or 2 is characterized in that the ratio of oxygen to nitrogen in the second high chromium oxide layer is 2.5 or more and 10 or less.

(Composition 4) Such as constituting any one of 1 to 3 of the mask substrate, characterized in that the ratio of oxygen to nitrogen in the first high chromium oxide layer is 2.5 or more and 10 or less.

(Composition 5) The mask substrate of any one of components 1 to 4 is characterized in that the first reflection suppression layer contains carbon.

(Composition 6) The mask substrate of any one of components 1 to 5 is characterized in that the second reflection suppression layer contains carbon.

(Composition 7) For example, the mask substrate constituting any one of 1 to 6, characterized by: The chromium content of the above-mentioned first reflection suppression layer is 25 atomic% or more and 75 atomic% or less, the oxygen content is 15 atomic% or more and 45 atomic% or less, and the nitrogen content is 2 atomic% or more and 30 atomic% the following, The chromium content of the second reflection suppression layer is 25 atomic% or more and 75 atomic% or less, the oxygen content is 15 atomic% or more and 60 atomic% or less, and the nitrogen content is 2 atomic% or more and 30 atomic% the following.

(Composition 8) The mask substrate of any one of 1 to 7, characterized in that: the first reflection suppression layer and the second reflection suppression layer each have at least one of oxygen and nitrogen. The content of at least any element is along the film thickness direction. Consecutively or step by step constitute the area of change.

(Composition 9) The mask base of any one of 1 to 8, characterized in that it is located between the transparent substrate and the first reflection suppression layer, between the first reflection suppression layer and the light-shielding layer, and the light-shielding layer Between the second reflection suppression layer and the second reflection suppression layer, there is a gradient composition region in which the elements constituting the first reflection suppression layer, the light shielding layer, and the second reflection suppression layer continuously form a gradient change.

(Composition 10) For example, the mask substrate of any one of 1 to 9 is characterized in that the in-plane uniformity of the reflectance of the front surface of the light-shielding film to the exposure wavelength of the exposure light is 3% or less.

(Composition 11) For example, the mask base of any one of 1 to 10 is characterized in that it is further provided with a semi-transmissive film between the transparent substrate and the light-shielding film, and the semi-light-transmitting film has a lower optical density than the light-shielding film. The optical density.

(Composition 12) The mask base of any one of compositions 1 to 10 is characterized in that it further includes a phase shift film between the transparent substrate and the light-shielding film.

(Composition 13) A method for manufacturing a photomask is characterized by the following steps: Prepare the above-mentioned mask substrate as constituting any one of 1 to 12; and A step of forming a resist film on the light-shielding film, and etching the light-shielding film using the resist pattern formed of the resist film as a mask to form a light-shielding film pattern on the transparent substrate.

(Composition 14) A method for manufacturing a photomask is characterized by the following steps: Prepare the above-mentioned mask substrate as any one of 1 to 12; Forming a resist film on the light-shielding film, etching the light-shielding film using the resist pattern formed by the resist film as a mask to form a light-shielding film pattern on the transparent substrate; and The translucent film is etched using the light-shielding film pattern as a mask to form a translucent film pattern on the transparent substrate.

(Composition 15) A method for manufacturing a photomask, which is characterized in that it has the following steps: Prepare the above-mentioned mask substrate as any one of 1 to 12; Forming a resist film on the light-shielding film, etching the light-shielding film using the resist pattern formed by the resist film as a mask to form a light-shielding film pattern on the transparent substrate; and The phase shift film is etched using the light-shielding film pattern as a mask to form a phase shift film pattern on the transparent substrate.

(Composition 16) A method of manufacturing a display device, characterized by having: an exposure step, which places the photomask obtained by the manufacturing method of the photomask as configured in any one of 13 to 15 on the mask stage of the exposure device, and At least one of the light-shielding film pattern, the semi-transmissive film pattern, and the phase shift film pattern formed on the photomask is exposed and transferred to the resist formed on the substrate of the display device. [Effects of the invention]

According to the present invention, it is possible to obtain a mask substrate capable of manufacturing a mask with the following optical characteristics: patterning the light-shielding film in the mask substrate by etching to obtain a high-precision light-shielding film pattern when making the mask, and When using a photomask to transfer the transfer pattern to the transfer body, the pattern accuracy of the transfer body is improved.

<Research by the inventors and others> Regarding a mask base formed by laminating a first reflection suppressing layer, a light shielding layer, and a second reflection suppressing layer in order from the transparent substrate side of the light-shielding film, in order to improve the optical characteristics of the mask base, the inventors conducted research . However, it was confirmed that only by reducing the reflectivity of the front and back of the light-shielding film in the mask base, the accuracy of the transfer pattern transferred to the transferred body would not be improved.

The main reason for this has been studied, and it was found that the main reason for the decrease in the accuracy of the transfer pattern of the transferred body is that the reflectivity of the front and back of the light-shielding film of the mask substrate is not uniform in the plane (the reflectivity in the plane) Larger unevenness). In the light-shielding film, the first and second reflection suppression layers are oxidized in order to reduce the reflectivity, but the degree of oxidation tends to be uneven in the plane. In addition, when nitriding the light-shielding layer, the degree of nitriding tends to be uneven in the plane. Because the degree of oxidation of the first and second reflection suppression layers or the degree of nitridation of the light-shielding layer is uneven in the plane, the reflectivity of the front and back sides of the light-shielding film becomes uneven in the plane.

In addition, in order to lower the reflectance of the front and back surfaces of the light-shielding film, the first reflection suppression layer or the second reflection suppression layer must be more strongly oxidized, but defects are likely to occur during film formation.

In the mask, because the reflectivity of the front and back of the light-shielding film pattern becomes uneven in the plane (the unevenness of the reflectance increases), it is impossible to accurately transfer the light-shielding film pattern of the mask to the transfer. The CD uniformity of the transfer pattern of the transferred body is impaired.

On the other hand, the main reason for the decrease in the pattern accuracy of the light-shielding film pattern obtained when the light-shielding film of the mask substrate is etched is that the etching rate or etching time of each layer constituting the light-shielding film is inconsistent. If there is a huge difference in the etching rate or etching time of each layer constituting the light-shielding film, when the light-shielding film is etched to form the light-shielding film pattern, etching residues are particularly likely to occur at the transparent substrate side of the first reflection suppression layer. If etching residue occurs, the cross-sectional shape of the light-shielding film pattern is not easy to be vertical, so the line width of the light-shielding film pattern becomes different on the front side and the back side, resulting in a decrease in the accuracy of the light-shielding film pattern of the mask.

Based on the above situation, the inventors of the present invention conducted research on a method for making the reflectance of the front and back of the light-shielding film in the mask substrate uniform in the plane. The first reflection suppression layer and the second reflection suppression layer in the previous photomask substrate are generally composed of a single layer of a high-oxidation layer. However, in a single layer that constitutes the high oxide case of first reflection suppressing layer and a second reflection suppressing layer, the surface of the substrate in the mask, the degree of reflection suppression of the second oxide layer of the first reflective layer does not inhibit the Both become more significant, which will have a greater impact on the in-plane unevenness of the reflectivity of the front and back of the shading film. In addition, it is considered that the first reflection suppression layer and the second reflection suppression layer are oxidized to a high degree, and defects are likely to occur.

Therefore, the inventors of the present invention focused on constructing the first and second reflection suppression layers with a two-layered structure in which the degree of oxidation of the low-oxidation layer and the high-oxidation layer were different, and studied. As a result, it was found that, compared with the case where the first and second reflection suppression layers are composed of only a single layer of a high-oxidation layer, the reflectivity of the front and back of the light-shielding film can be made more uniform in the base surface of the mask, or the light-shielding can be reduced Defects of the membrane. It was also found that by constructing the first reflection suppression layer with a low-oxidation layer and a high-oxidation layer in order from the transparent substrate side, the etching residue on the transparent substrate side of the first reflection suppression layer was suppressed. As a result, the light-shielding film pattern could be achieved. The cross-sectional shape is good, and a high-precision shading film pattern is obtained.

In addition, it has been found that from the viewpoint of making the reflectance of the front and back surfaces of the light-shielding film more uniform in the surface of the mask base, it is better to set the light-shielding layer in the light-shielding film as close as possible to one that does not oxidize or nitride. The state of the metal film. So far, from the viewpoint of controlling the etching rate (etching time) of the light-shielding film, the light-shielding layer is composed of a metal film (metal nitride film) containing nitrogen. However, if nitrogen is contained in the light-shielding layer, a non-uniformity (non-uniformity) of nitrogen content will occur in the base surface of the photomask. In addition, since the first and second reflection suppression layers located above and below the light-shielding layer contain oxygen, the first and second reflection suppression layers will also produce uneven oxygen content (unevenness) in the base surface of the mask. . The unevenness (unevenness) of the nitrogen content of the light-shielding layer in the surface of the mask substrate and the unevenness of the oxygen content of the first and second reflection suppression layers in the surface of the mask substrate are complementary to each other, resulting in the light-shielding film The in-plane unevenness (unevenness) of the reflectance of the front and back sides increases. In order to reduce the in-plane unevenness of the reflectivity of the front and back of the light-shielding film, it is more effective to reduce the nitrogen unevenness in the base surface of the mask contained in the light-shielding layer. Therefore, it is possible to reduce the unevenness in the light-shielding layer The contained nitrogen content rate (no nitrogen added) reduces the in-plane unevenness of the reflectance of the front and back surfaces of the light-shielding film.

The present invention is based on the above findings.

<One embodiment of the present invention> Hereinafter, an embodiment of the present invention will be described. In addition, the following embodiment is an aspect when the present invention is embodied, and the present invention is not limited to this scope. In addition, in the drawings, the same or equivalent parts may be denoted with the same reference numerals and their descriptions may be simplified or omitted. In addition, in this specification, the numerical range indicated by "～" means the range that includes the numerical values described before and after "～" as the lower limit and the upper limit.

(1) Mask base First, the photomask substrate of one embodiment of the present invention will be described. The photomask substrate of this embodiment is used for manufacturing light of a single wavelength selected from the wavelength band of 300 nm to 436 nm or light containing multiple wavelengths (for example, j-line (wavelength 313 nm), wavelength 334 nm, i-line (Wavelength 365 nm), h-line (405 nm), g-line (wavelength 436 nm)) composite light exposure for display device manufacturing masks.

FIG. 1 is a cross-sectional view showing a schematic configuration of a photomask substrate according to an embodiment of the present invention. The mask base 1 includes a transparent substrate 11 and a light-shielding film 12. Hereinafter, as a mask base of one embodiment of the present invention, a binary mask base in which the light-shielding film pattern (transfer pattern) of the light-shielding film is a light-shielding film pattern will be described.

(Transparent substrate) The transparent substrate 11 is formed of a material that is substantially transparent to exposure light, and is not particularly limited as long as it is a transparent substrate. Use a substrate material whose transmittance to the exposure wavelength is 85% or more, preferably 90% or more. Examples of the material forming the transparent substrate 11 include synthetic quartz glass, soda lime glass, alkali-free glass, and low thermal expansion glass.

The size of the transparent substrate 11 is not particularly limited, and can be appropriately changed according to the required size of the photomask. For example, in the case of a photomask for manufacturing a display device, a rectangular substrate and a transparent substrate 11 with a short side length of 330 mm or more and 1620 mm or less can be used as the transparent substrate 11. As the transparent substrate 11, for example, sizes of 330 mm × 450 mm, 390 mm × 610 mm, 500 mm × 750 mm, 520 mm × 610 mm, 520 mm × 800 mm, 800 × 920 mm, 850 mm × 1200 mm can be used. , 850 mm×1400 mm, 1220 mm×1400 mm, 1620 mm×1780 mm, etc. It is particularly preferable that the length of the short side of the substrate is 850 mm or more and 1620 mm or less. By using such a transparent substrate 11, a photomask for manufacturing display devices of G7 to G10 can be obtained.

(Shading film) The light-shielding film 12 is formed of a material that is substantially opaque to exposure light. The first reflection-inhibiting layer 13, the light-shielding layer 14, and the second reflection-inhibiting layer 15 are sequentially laminated from the transparent substrate 11 side. In addition, in this specification, the surface on the light-shielding film 12 side among the two surfaces of the mask base 1 is referred to as the front surface, and the surface on the transparent substrate 11 side is referred to as the back surface. In addition, at least the first reflection suppression layer 13 and the light-shielding layer are set so that the reflectance of the front and back surfaces of the light shielding film 12 to the exposure wavelength of the above-mentioned exposure light is 15% or less and the optical density becomes 3.0 or more. 14 and the composition and film thickness of the second reflection suppression layer 15. In addition, it is also possible to adjust at least the first low chromium oxide layer 13a in the first reflection suppression layer 13 and the first low chromium oxide layer 13a in the first reflection suppression layer 13 and the first low chromium oxide layer 13a and the second 1 Composition ratio and film thickness of the high chromium oxide layer 13b.

(The first reflection suppression layer) The first reflection suppression layer 13 is provided in the light-shielding film 12 on the side of the light-shielding layer 14 near the transparent substrate 11, and is arranged close to the exposure device when pattern transfer is performed using a photomask made using the photomask base 1 (Light source of exposure) side. In the case of exposure processing using a photomask, the exposure light is irradiated from the transparent substrate 11 side (rear side) of the photomask to transfer the pattern transfer image to the substrate formed on the display device as the transferred body Resist film. At this time, the reflected light after the exposure light is reflected on the back side of the light-shielding film pattern enters the optical system of the exposure device, and then enters from the transparent substrate 11 side of the mask again, so it becomes the stray light of the light-shielding film pattern and becomes the formation Deterioration of the transferred pattern such as ghosting or increased amount of flare. When a photomask is used for pattern transfer, the first reflection suppressing layer 13 can suppress the reflection of exposed light on the back side of the light shielding film 12, thereby suppressing the deterioration of the transferred pattern and improving the transfer characteristics.

As described above, in this embodiment, in order to reduce defects, and to reduce the reflectivity of the back surface of the light-shielding film 12, and to improve the uniformity of the reflectance in the surface of the mask base (in order to suppress the in-plane unevenness of the reflectance) ), the first reflection suppression layer 13 is formed by sequentially stacking a first low-chromium oxide layer 13a with relatively little oxidation and a first high-chromium oxide layer 13b with relatively high oxidation from the transparent substrate 11 side.

The first low chromium oxide layer 13a is formed in such a way that the degree of oxidation is reduced.

In addition, the first low chromium oxide layer 13a is as follows. Compared with the first high chromium oxide layer 13b, the ratio of oxygen (O) to nitrogen (N) is small, that is, the N content is increased, so it is compared with The first high chromium oxide layer 13b can shorten the etching time. Therefore, when the photomask base 1 is etched, the etching residue of the first low chromium oxide layer 13a can be prevented, and the cross-sectional shape of the light-shielding film pattern can be made closer to vertical.

In addition, since the degree of oxidation of the first low chromium oxide layer 13a decreases and the content of N increases, even when the light-shielding film 12 is etched to form a fine light-shielding film pattern, it is possible to ensure close contact with the transparent substrate 11 It can prevent the peeling of the film of the shading film pattern.

The first high chromium oxide layer 13b increases the degree of oxidation so that the back surface reflectance of the light shielding film 12 (the back surface reflectance of the first reflection suppression layer 13) becomes a specific characteristic.

(Shading layer) The light-shielding layer 14 is provided in the light-shielding film 12 between the first reflection suppression layer 13 and the second reflection suppression layer 15. The light-shielding layer 14 has a function of being adjusted so as to have an optical density for making the light-shielding film 12 substantially opaque to exposed light. Here, the term "substantially opaque to exposure light" means a light-shielding property of 3.0 or more in terms of optical density. From the viewpoint of transfer characteristics, the optical density is preferably 4.0 or more, and more preferably 4.5 or more.

(Second reflection suppression layer) The second reflection suppression layer 15 is provided in the light-shielding film 12 on the surface of the light-shielding layer 14 away from the transparent substrate 11. The second reflection suppression layer 15 has a function of forming a resist film thereon and suppressing the formation of a specific resist pattern by drawing light (laser light) from a drawing device (for example, a laser drawing device) on the resist film. The above-mentioned drawing light is reflected on the front side of the light-shielding film 12. Thereby, the CD uniformity of the resist pattern and the light-shielding film pattern formed therefrom can be improved. On the other hand, the second reflection suppression layer 15 is arranged on the side of the transfer object when the photomask is used, and suppresses the light reflected by the transfer object from being reflected again on the front side of the light shielding film 12 of the photomask and then returning to the transfer object. body. This suppresses the deterioration of the transfer pattern and contributes to the improvement of transfer characteristics.

The second reflection suppression layer 15 is, like the first reflection suppression layer 13, composed of two chromium oxide layers with different oxidation degrees. Specifically, in order to reduce defects, and to reduce the front reflectance of the light shielding film 12 and improve the uniformity of the front reflectance in the mask base surface (in order to suppress the in-plane unevenness of the front reflectance), the second reflection The suppression layer 15 is formed by sequentially stacking a second low-chromium oxide layer 15a with relatively little oxidation and a second high-chromium oxide layer 15b with relatively high oxidation from the light-shielding layer 14 side.

The second low chromium oxide layer 15a is the same as the first low chromium oxide layer 13a, and is formed in such a way that the degree of oxidation is reduced.

The second high chromium oxide layer 15b increases the degree of oxidation, so that the front surface reflectance of the light shielding film 12 (the front surface reflectance of the second reflection suppression layer 15) becomes a specific characteristic. In addition, the second high chromium oxide layer 15b has a higher degree of oxidation, which also contributes to improving the chemical resistance or resistance to cleaning solutions such as acid or alkali used when cleaning the photomask substrate or the photomask. When a resist film is formed on the second high chromium oxide layer 15b, the adhesion to the resist film is relatively high.

(Material of shading film) Next, the formation materials of each layer of the first reflection suppression layer 13, the light shielding layer 14, and the second reflection suppression layer in the light shielding film 12 will be described.

The material of each layer of the first reflection suppression layer 13, the light shielding layer 14, and the second reflection suppression layer is not particularly limited as long as the above-mentioned optical characteristics can be obtained in the photomask base 1. From the viewpoint of obtaining the above-mentioned optical characteristics For each layer, the following materials are preferably used.

The first reflection suppression layer 13 is preferably made of a chromium-based material containing chromium, oxygen, and nitrogen. Oxygen (O) mainly has a function of reducing the reflectance of the first reflection suppression layer 13. Nitrogen (N) mainly has the function of reducing the reflectance of the first reflection suppressing layer 13 and increasing the etching rate of the first reflection suppressing layer 13 to shorten the etching time. Furthermore, from the viewpoint of controlling the etching characteristics, the first reflection suppression layer 13 may further contain carbon (C) or fluorine (F), and it is particularly preferable to contain carbon (C). By including C in the first reflection suppression layer 13, the etching rates of the first reflection suppression layer 13 and the light-shielding layer 14 can be easily matched, and the cross-sectional shape of the light-shielding film pattern can be made better.

The first reflection suppression layer 13 is composed of a first low-chromium oxide layer 13a and a first high-chromium oxide layer 13b with different oxidation degrees. The degree of oxidation refers to the ratio of oxygen to nitrogen (hereinafter, also referred to as O/N ratio). The first low chromium oxide layer 13a is formed of a chromium-based material with a relatively small ratio of O to N, and the first high The chromium oxide layer 13b is formed of a chromium-based material with a relatively large ratio of O to N.

The light shielding layer 14 is made of a chromium-based material. The light shielding layer 14 may contain O, N, C, F, etc. in addition to chromium (Cr). From the viewpoint of making the front reflectance and back reflectance of the light-shielding film 12 more uniform in the surface of the mask base, it is preferable to set the light-shielding layer 14 as a chromium film that does not substantially contain O, N, and F. The fact that O, N, and F are not substantially included means that they will not be added deliberately, except in cases where they are unavoidably included. More specifically, the so-called chromium film that does not substantially contain O, N, and F refers to a chromium film in which the total content of these elements is 3 atomic% or less, and the total content of these elements is 2 atomic% or less . As described above, the nitrogen content in the light shielding layer 14 cannot be made uniform in the plane, and the refractive index difference with the first reflection suppression layer 13 and the second reflection suppression layer 15 will be too large or too small, so the presence of The in-plane unevenness of the back reflectance or the front reflectance in the mask substrate 1. In this case, the front reflectance and the back reflectance of the light shielding film 12 can be made more uniform in the surface of the mask base by forming a chromium film that does not substantially contain O, N, and F in the light shielding layer 14.

The second reflection suppression layer 15 is preferably made of a chromium-based material containing chromium, oxygen, and nitrogen. In the second reflection suppression layer 15, oxygen (O) has the following function: not only reduces the reflectance of exposure light or drawing light, but also improves the adhesion to the resist film, thereby suppressing the resist film and light shielding due to the etchant. The interfacial penetration of the membrane 12 causes undercutting. Nitrogen (N) reduces the reflectivity of the second reflection suppression layer 15 and increases the etching rate of the second reflection suppression layer 15 to shorten the etching time. Furthermore, from the viewpoint of controlling etching characteristics, carbon (C) or fluorine (F) may be further contained, and carbon (C) is particularly preferably contained. By making the second reflection suppression layer 15 contain C, it is easy to make the etching rates of the second reflection suppression layer 15 and the light shielding layer 14 equal, and the cross-sectional shape of the light shielding film pattern can be made better.

(Composition of shading film) Next, the composition of each layer in the light-shielding film 12 will be described in detail. In addition, the content rate of each of the following elements is the value measured by X-ray photoelectric spectroscopy (XPS).

The chromium-based material forming the first low chromium oxide layer 13a preferably contains chromium (Cr), oxygen (O), and nitrogen (N), and the ratio of O to N is 0.1 or more and less than 2.5. Furthermore, the first low chromium oxide layer 13a preferably contains chromium (Cr) at a content rate of 25 to 95 at%, oxygen (O) at a content rate of 5 to 45 at%, and 2 to 35 at%. The content rate includes nitrogen (N), and the ratio of O to N is 0.1 or more and less than 2.5. The chromium-based material forming the first high chromium oxide layer 13b preferably contains chromium (Cr), oxygen (O), and nitrogen (N), and the ratio of O to N is 2.5 or more and 10 or less. Furthermore, the first high chromium oxide layer 13b preferably contains chromium (Cr) at a content rate of 30 to 95 at%, oxygen (O) at a content rate of 7 to 50 at%, and 2 to 25 at%. The content rate includes nitrogen (N), and the ratio of O to N is 2.5 or more and 10 or less. The content of Cr contained in the first low chromium oxide layer 13 a and the first high chromium oxide layer 13 b is preferably lower than the Cr contained in the light shielding layer 14. In addition, the total content of O and N contained in the first low-chromium oxide layer 13a and the first high-chromium oxide layer 13b is preferably 7 to 75 atomic %.

The chromium material forming the light-shielding layer 14 preferably mainly contains Cr, and the Cr content is 97 atomic% or more and 100 atomic% or less. In addition to Cr, O, N, C, F, etc. may be included, and the total content of these is preferably 3 atomic% or less.

The chromium-based material forming the second low chromium oxide layer 15a preferably contains chromium (Cr), oxygen (O), and nitrogen (N), and the ratio of O to N is 0.1 or more and less than 2.5. Furthermore, the second low chromium oxide layer 15a preferably contains chromium (Cr) at a content rate of 25 to 95 at%, oxygen (O) at a content rate of 5 to 45 at%, and 2 to 35 at%. The content rate includes nitrogen (N), and the ratio of O to N is 0.1 or more and less than 2.5. The chromium-based material forming the second high chromium oxide layer 15b preferably contains chromium (Cr), oxygen (O), and nitrogen (N), and the ratio of O to N is 2.5 or more and 10 or less. Furthermore, the second high chromium oxide layer 15b preferably contains chromium (Cr) at a content rate of 30 to 70 at%, oxygen (O) at a content rate of 15 to 60 at%, and 2 to 30 at%. The content rate includes nitrogen (N), and the ratio of O to N is 2.5-10. The content of Cr contained in the second low chromium oxide layer 15 a and the second high chromium oxide layer 15 b is preferably lower than the Cr contained in the light shielding layer 14. In addition, the total content of O and N contained in the second low-chromium oxide layer 15a and the second high-chromium oxide layer 15b is preferably 7 to 75 atomic %.

The first reflection suppression layer 13 and the second reflection suppression layer 15 preferably have regions in which the content of at least any element of O and N changes continuously or stepwise along the film thickness direction.

In addition, it may be formed between the transparent substrate 11 and the first reflection suppression layer 13, between the first reflection suppression layer 13 and the light shielding layer 14, and between the light shielding layer 14 and the second reflection suppression layer 15. The elements of the layer 13, the light-shielding layer 14, and the second reflection suppression layer 15 continuously form a gradient composition area with a gradient change.

(About film thickness) In the light-shielding film 12, the thickness of each of the first reflection-inhibiting layer 13, the light-shielding layer 14, and the second reflection-inhibiting layer 15 is not particularly limited, and can be appropriately adjusted according to the optical density and reflectance required by the light-shielding film 12.

From the viewpoint of achieving both suppression of defects in the first reflection suppression layer 13 and reduction of back surface reflectance, the thickness of the first low-chromium oxide layer 13a and the first high-chromium oxide layer 13b is preferably set to 10 nm or more. And 35 nm or less, the thickness of the first reflection suppression layer 13 obtained by these sums is preferably 20 nm or more and 70 nm or less. In addition, it is expected that the ratio of the thickness of the first low chromium oxide layer 13a to the first high chromium oxide layer 13b is preferably the first high chromium oxide layer: the first low chromium oxide layer = 1:7 to 1:1, and more preferably It is the first high chromium oxide layer: the first low chromium oxide layer=1:5 to 1:2.

The thickness of the light-shielding layer 14 can be appropriately changed according to the optical density required by the light-shielding film 12. For example, if the optical density is set to 3 or more, the thickness of the light shielding layer 14 can be set to 50 nm to 200 nm.

The thickness of the second reflection suppression layer 15 is adjusted in such a way that specific optical characteristics (frontal reflectance) can be obtained for exposure light or drawing light from the front side of the light-shielding film 12. Specifically, the second low chromium oxide layer 15a in the second reflection suppression layer 15 is adjusted so that the representative wavelength (for example, 365 nm to 436 nm) of the light exposed from the back side of the light shielding film 12 becomes 10% or less , And the film thickness of the second high chromium oxide layer 15b. From the viewpoint of achieving both suppression of defects in the second reflection suppression layer 15 and reduction of the frontal reflectance, the thickness of the second low chromium oxide layer 15a and the thickness of the second high chromium oxide layer 15b are preferably set to 10 respectively. nm or more and 35 nm or less, the thickness of the second reflection suppression layer 15 obtained by these totals is preferably 20 nm or more and 70 nm or less. In addition, it is expected that the thickness ratio of the second low chromium oxide layer 15a to the second high chromium oxide layer 15b is preferably the second high chromium oxide layer: the second low chromium oxide layer = 1:7 to 1:1, and more preferably It is the second high chromium oxide layer: the second low chromium oxide layer=1:5 to 1:2.

(Optical characteristics of the mask substrate) The mask substrate 1 has the following optical characteristics.

The reflectance spectrum of the front side of the light-shielding film 12 obtained by irradiating the front side of the light-shielding film 12 of the mask substrate 1 with exposure light or drawing light is at a representative wavelength within the exposure wavelength range of 300 nm to 436 nm, and front reflection The rate is preferably 15% or less, more preferably 12% or less, and still more preferably 10% or less. More preferably, the front reflection spectrum of the light-shielding film 12 is within the exposure wavelength range of 300 nm to 436 nm, and the front reflection rate is preferably 15% or less, more preferably 12% or less, and even more preferably 10% or less. Or the front reflectance spectrum of the light-shielding film 12 is at a representative wavelength in the exposure wavelength range of 365 nm to 436 nm. The front reflectance is preferably 10% or less, more preferably 7.5% or less, and more preferably 5% or less . More preferably, the reflectance spectrum of the front surface of the light shielding film 12 is within the range of the exposure wavelength from 365 nm to 436 nm, and the front reflectance is preferably 10% or less, more preferably 7.5% or less, and even more preferably 5% or less. Moreover, the reflectance spectrum of the back surface of the light-shielding film 12 obtained when the back surface of the light-shielding film 12 of the mask substrate 1 is irradiated with exposure light is at a representative wavelength in the range of exposure wavelength from 300 nm to 436 nm. It is preferably 15% or less, more preferably 12% or less, and still more preferably 10% or less. More preferably, the reflectance spectrum of the back surface of the light shielding film 12 is within the range of exposure wavelength 300 nm to 436 nm, and the back surface reflectance is preferably 15% or less, more preferably 12% or less, and still more preferably 10% or less. In addition, the reflectance spectrum of the back surface of the light-shielding film 12 is at a representative wavelength in the exposure wavelength range of 365 nm to 436 nm. The back surface reflectance is preferably 10% or less, more preferably 7.5% or less, and still more preferably 5% the following. More preferably, the reflectance spectrum of the back surface of the light-shielding film 12 is within the range of the exposure wavelength from 365 nm to 436 nm, and the back surface reflectance is preferably 10% or less, more preferably 7.5% or less, and still more preferably 5% or less.

In addition, the reflectivity of the front and back surfaces of the light shielding film 12 of the mask substrate 1 is within the range of exposure wavelength 300 nm-436 nm or within the range of 365 nm-436 nm, and the wavelength dependence is relatively small. The wavelength dependence means that the reflectance changes depending on the exposure wavelength. The smaller wavelength dependence means that the difference between the maximum value and the minimum value of the reflectance is small, that is, the change in reflectance (variation range) is small. Specifically, the wavelength dependence of the reflectance of the front and back of the light-shielding film 12 is within the range of the exposure wavelength from 300 nm to 436 nm, preferably 12% or less, more preferably 10% or less. Or the wavelength dependence of the reflectance of the front and back of the light-shielding film 12 is within the range of the exposure wavelength from 365 nm to 436 nm, preferably 5% or less, more preferably 3% or less.

In addition, the mask substrate 1 can suppress the in-plane unevenness of the reflectance (front reflectance, back reflectance) of the front and back of the light-shielding film 12, thereby improving the in-plane uniformity of the reflectance of the front and back. Specifically, the front reflectance of the light-shielding film 12 can be suppressed to 3% or less (range). The in-plane uniformity of the front surface reflectance of the light-shielding film 12 is based on the measurement of 11×11=121 points on the front surface of the mask substrate 1 excluding the 50 mm peripheral edge of the mask substrate using a reflectance meter. Calculated from the result of frontal reflectivity. Moreover, the back surface reflectance of the light-shielding film 12 can be suppressed to 5% or less (range). The in-plane uniformity of the back surface reflectance of the light-shielding film 12 is calculated based on the following: instead of the mask base 1, instead of covering the surface of the mask base 1 with a plurality of dummy substrates (for example, 6 inches × 6 Inch size), the first reflection suppression layer 13, the light blocking layer 14, and the second reflection suppression layer 15 constituting the light shielding film 12 are formed, and the reflectance of the back surface of the light shielding film 12 formed on the dummy substrate is measured with a reflectometer. The result of back reflectivity. Furthermore, the so-called in-plane uniformity of reflectance refers to the difference between the maximum value and the minimum value of the reflectance at any plural points of the mask substrate.

＜Manufacturing method of mask substrate＞ Next, the manufacturing method of the above-mentioned photomask substrate 1 is demonstrated.

(Preparatory steps) A transparent substrate 11 that is substantially transparent to the light to be exposed is prepared. Furthermore, the transparent substrate 11 may be subjected to any processing steps such as a grinding step and a polishing step as necessary to become a flat and smooth main surface. It can be cleaned after polishing to remove foreign matter and contamination on the surface of the transparent substrate 11. As washing, for example, sulfuric acid, sulfuric acid hydrogen peroxide mixture (SPM), ammonia, ammonia water hydrogen peroxide mixture (APM), OH radical washing water, ozone water, warm water, etc. can be used.

(Steps of forming the first reflection suppression layer) Then, the first reflection suppression layer 13 is formed on the transparent substrate 11. In this embodiment, the first low-chromium oxide layer 13a and the first high-chromium oxide layer 13b are sequentially stacked from the transparent substrate 11 side to form the first reflection suppression layer 13.

In the formation of the first reflection suppression layer 13, a sputtering target containing Cr, a reactive gas containing oxygen-based gas and nitrogen-based gas, and a sputtering gas containing rare gas are used to form a film by reactive sputtering. At this time, as the film forming condition, the flow rate of the reactive gas contained in the sputtering gas selects the flow rate of the metal mode.

In reactive sputtering, when a reactive gas such as an oxygen-based gas or a nitrogen-based gas is introduced into the sputtering target while the sputtering target is discharged, the state of the discharge plasma changes according to the flow rate of the reactive gas, and the film formation speed follows Variety. In the metal mode, by reducing the ratio of the reactive gas, the adhesion of the reactive gas to the surface of the sputtering target can be reduced, and the film formation speed can be accelerated. Moreover, in the metal mode, since the supply amount of the reactive gas is small, it is possible to form, for example, an oxygen content (O content) or a nitrogen content (N content) compared to a film with a stoichiometric composition. At least any film with reduced content.

From the viewpoint of suppressing defects in the first reflection suppressing layer 13, it is preferable to reduce the power applied to the sputtering target in the film forming conditions. If the power applied to the sputtering target is reduced, the micro-arc or abnormal discharge of the sputtering target can be suppressed during reactive sputtering with oxygen-based gas or nitrogen-based gas introduced, thereby suppressing the defects of the first reflection suppression layer 13 produce. As the conditions for the metal mode for forming the first reflection suppression layer 13, for example, the flow rate of the oxygen-based gas is set to 1 to 45 sccm, the flow rate of the nitrogen-based gas is set to 30 to 60 sccm, and the flow rate of the hydrocarbon-based gas is set to The flow rate is set to 1-15 sccm, and the flow rate of the rare gas is set to 20-100 sccm. In addition, the target applied power can be set to 1.0 to 6.0 kW.

As the sputtering target, any one containing chromium may be used. For example, in addition to chromium, chromium-based materials such as chromium oxide, chromium nitride, and chromium oxynitride may also be used. As the oxygen-based gas, for example, oxygen (O ₂ ), carbon dioxide (CO ₂ ), nitrogen oxide gas (N ₂ O, NO, NO ₂ ), or the like can be used. As the nitrogen-based gas, nitrogen (N ₂ ) or the like can be used. For example, helium, neon, argon, krypton, xenon, etc. can also be used as rare gases. Furthermore, in addition to the above-mentioned reactive gas, a hydrocarbon-based gas may be supplied. For example, methane gas or butane gas may be used.

In this embodiment, the flow rate of the reactive gas and the power applied to the sputtering target are set to the conditions such as the metal mode, and the sputtering target containing Cr is used to perform the film forming process based on the reactive sputtering. Thereby, a first low-chromium oxide layer 13a with a relatively small ratio of O to N is first formed on the transparent substrate 11, and a first high-chromium oxide layer 13a with a relatively large ratio of O to N is formed thereon The layer 13b thereby forms the first reflection suppression layer 13. The first low chromium oxide layer 13a is formed in a metal mode with low power and a lower O content than the first high chromium oxide layer 13b. The first high chromium oxide layer 13b is formed in a metal mode, low power, and so that the O content is higher than that of the first low chromium oxide layer 13a. Furthermore, the film formation conditions in the metal mode can be set with reference to Japanese Patent Laid-Open No. 2019-20712, etc., for example.

In addition, when switching from the first low chromium oxide layer 13a to the first high chromium oxide layer 13b for film formation, in order to change the O content and N content, the type, flow rate, and reactivity of the reactive gas can be appropriately changed The ratio of oxygen-based gas or nitrogen-based gas in the gas, etc. In addition, it is also possible to change the arrangement of the gas supply port or the gas supply method. In addition, the film formation time can be appropriately changed in accordance with the thickness of each layer.

(Steps of forming the light-shielding layer) Then, a light-shielding layer 14 is formed on the first reflection suppression layer 13. The light-shielding layer 14 is formed by sputtering using a sputtering target containing Cr and a sputtering gas containing a rare gas. At this time, as the film forming condition, the flow rate of the reactive gas contained in the sputtering gas selects the flow rate of the metal mode.

As a sputtering target, what is necessary is just to contain chromium. From the viewpoint of making the in-plane uniformity of the reflectance of the front and back of the light-shielding film 12 good, it is preferable to use a sputtering target containing chromium. As the rare gas, for example, helium, neon, argon, krypton, xenon, etc. can also be used. Furthermore, it is also possible to supply oxygen-based gas, nitrogen-based gas, and hydrocarbon-based gas in addition to the above-mentioned rare gas without departing from the effect of the present invention.

In this embodiment, the flow rate of the reactive gas and the applied power of the sputtering target are set to the conditions of the metal mode, and the sputtering target containing Cr is used for sputtering. Thereby, the light-shielding layer 14 mainly containing Cr is formed on the first reflection suppression layer 13.

In addition, as the film forming condition of the light shielding layer 14, the flow rate of the rare gas may be 60 to 200 sccm, for example. In addition, the target applied power can be set to 3.0 to 10.0 kW.

(Steps of forming the second reflection suppression layer) Then, the second reflection suppression layer 15 is formed on the light shielding layer 14. The formation of the second reflection suppression layer 15 is the same as that of the first reflection suppression layer 13. The flow rate of the reactive gas and the power applied to the sputtering target are set to the conditions of the metal mode, and the sputtering target containing Cr is used. Reactive sputtering performs film formation. Thereby, a second low chromium oxide layer 15a with a relatively small ratio of O to N is formed on the light shielding layer 14, and a second high chromium oxide layer with a relatively large ratio of O to N is formed on it 15b is formed into a film, thereby forming the second reflection suppression layer 15. The second low chromium oxide layer 15a is formed in a metallic mode and low power, so that the O content is lower than that of the second high chromium oxide layer 15b. The second high chromium oxide layer 15b is formed in a metal mode with low power, and is formed so that the O content rate is higher than that of the second low chromium oxide layer 15a.

As the conditions of the metal mode for forming the second reflection suppression layer 15, for example, the flow rate of the oxygen-based gas is set to 1 to 45 sccm, the flow rate of the nitrogen-based gas is set to 30 to 60 sccm, and the hydrocarbon-based gas The flow rate is set to 1-15 sccm, and the flow rate of rare gas is set to 20-100 sccm. In addition, the target applied power can be set to 1.0 to 6.0 kW.

Furthermore, when switching from the second low chromium oxide layer 15a to the first high chromium oxide layer 13b for film formation, similarly to the first reflection suppression layer 13, the type or flow rate of the reactive gas and the reactive gas can be appropriately changed The ratio of oxygen-based gas or nitrogen-based gas, etc. In addition, it is also possible to change the arrangement of the gas supply port or the gas supply method.

Through the above, the photomask substrate 1 of this embodiment is obtained.

Furthermore, the film formation of each layer in the light-shielding film 12 can be performed in-situ using an in-line sputtering device. In the case of non-in-line type, after the formation of each layer, the transparent substrate 11 must be disassembled to the outside of the device. The transparent substrate 11 is exposed to the atmosphere and sometimes each layer may undergo surface oxidation or surface carbonization. As a result, sometimes the reflectance of the light shielding film 12 to the exposed light or the etching rate may change. In this case, if it is an in-line type, each layer can be continuously formed without removing the transparent substrate 11 to the outside of the device and exposing to the atmosphere. Therefore, it is possible to suppress unintentional infiltration of elements into the light-shielding film 12.

In addition, when the light-shielding film 12 is formed using an in-line sputtering device, the first reflection-inhibiting layer 13, the light-shielding layer 14, and the second reflection-inhibiting layer 15 have a gradient composition area with a continuous composition gradient among the layers. (Transition layer), so that the cross-section of the light-shielding film pattern formed by etching (especially wet etching) using a photomask substrate can be smooth and close to vertical, which is preferable.

＜Manufacturing method of photomask＞ Next, a method of manufacturing a photomask will be described using the above-mentioned photomask substrate 1.

(Steps of forming resist film) First, a resist is coated on the second reflection suppression layer 15 in the light-shielding film 12 of the photomask base 1, and dried to form a resist film. As the resist, an appropriate one must be selected corresponding to the drawing device used, and either a positive type or a negative type resist can be used.

(Steps of forming resist pattern) Then, a drawing device is used to draw a specific pattern on the resist film. Generally, a laser drawing device is used when making a mask for manufacturing a display device. After drawing, the resist film is developed and cleaned to form a specific resist pattern.

The present embodiment is configured to reduce the reflectance of the second reflection suppression layer 15, so when the pattern is drawn on the resist film, the reflection of drawing light (laser light) can be reduced. Thereby, a resist pattern with higher pattern accuracy can be formed, and accordingly, a light-shielding film pattern with higher dimensional accuracy can be formed.

(Steps of forming shading film pattern) Then, the light-shielding film 12 is etched using the resist pattern as a mask, thereby forming a light-shielding film pattern. The etching may be wet etching or dry etching. Generally, wet etching is performed in a photomask for manufacturing a display device. As an etching solution (etchant) used in wet etching, for example, a chromium etching solution containing cerium ammonium nitrate and perchloric acid can be used.

In this embodiment, the composition of each layer is adjusted so that the etching rates of the first reflection suppression layer 13, the light shielding layer 14, and the second reflection suppression layer 15 are consistent in the thickness direction of the light shielding film 12. The cross-sectional shape, that is, the cross-sectional shape of the light-shielding film pattern is nearly perpendicular to the transparent substrate 11, so that a high CD uniformity can be obtained.

(Peeling step) Then, the resist pattern is peeled off, and a mask having a light-shielding film pattern (light-shielding film pattern) formed on the transparent substrate 11 is obtained.

Through the above, the photomask of this embodiment is obtained.

＜Manufacturing method of display device＞ Next, a method of manufacturing a display device using the above-mentioned photomask will be described.

(Preparatory steps) First, a substrate with a resist film in which a resist film is formed on the substrate of the display device is prepared. Then, the photomask obtained by the above-mentioned manufacturing method is placed on the mask stage of the exposure apparatus so that the projection optical system of the exposure apparatus and the resist film of the substrate with the resist film are opposed to each other.

(Exposure step (pattern transfer step)) Then, a resist exposure step of irradiating the photomask with exposure light to transfer the pattern to the resist film formed on the substrate of the display device is performed. The light for exposure is, for example, light of a single wavelength selected from the wavelength band of 300 nm to 436 nm (j-line (wavelength 313 nm), wavelength 334 nm, i-line (wavelength 365 nm), h-line (wavelength 405 nm), g-line (wavelength 436 nm), etc.) or light containing multiple wavelengths (e.g. j-line (wavelength 313 nm), wavelength 334 nm, i-line (wavelength 365 nm), h-line (405 nm), g-line (wavelength 436 nm)) of composite light. In the case of using a large mask, from the viewpoint of the amount of light, composite light can be used as the light for exposure. In this embodiment, a display device (display panel) is manufactured using a mask with a lower reflectivity of the front and back surfaces of the light-shielding film pattern (light-shielding film pattern) and high in-plane uniformity of the reflectance. Therefore, a high-precision transfer can be formed. Printed patterns.

<Effects of this embodiment> According to this embodiment, one or more of the following effects are achieved.

(a) In the mask base 1 of this embodiment, in the light-shielding film 12, a first low-chromium oxide layer 13a with relatively little oxidation and a first high-chromium oxide layer 13b with relatively high oxidation are laminated to form a first reflection suppression Layer 13. Thereby, the defects in the first reflection suppression layer 13 can be reduced, and the reflectivity of the back surface of the light-shielding film 12 can be reduced. In addition, the in-plane unevenness of the back surface reflectance can be suppressed in the mask substrate 1, and the uniformity of the back surface reflectance can be improved.

(b) In addition, the second low chromium oxide layer 15a, which is relatively less oxidized, and the second high chromium oxide layer 15b, which is relatively more oxidized, are laminated to form the second reflection suppression layer 15. Thereby, the defects in the second reflection suppression layer 15 can be reduced, and the reflectivity of the front surface of the light-shielding film 12 can be reduced. In addition, the in-plane unevenness of the front reflectance can be suppressed in the mask substrate 1 and the uniformity of the front reflectance can be improved.

(c) It is preferable that the first low chromium oxide layer 13a contains Cr at a content rate of 25 to 95 at%, O at a content rate of 5 to 45 at%, and N at a content rate of 2 to 35 at%. And the ratio of O to N is less than 2.5, and the first high chromium oxide layer 13b contains Cr at a content rate of 30 to 95 at%, and O at a content rate of 7 to 50 at%, and 2 to 25 at%. The content rate includes N, and the ratio of O to N is 2.5-10. In addition, it is preferable that the second low chromium oxide layer 15a contains Cr at a content rate of 25 to 95 at%, O at a content rate of 5 to 45 at%, and N at a content rate of 2 to 35 at%, and The ratio of O to N is less than 2.5, and the second high chromium oxide layer 15b contains Cr at a content rate of 30 to 70 at%, O at a content rate of 15 to 60 at%, and a content of 2 to 30 at%. The rate includes N, and the ratio of O to N is 2.5-10. By forming each layer with such a composition, the reflectivity of the front and back of the light-shielding film 12 can be reduced (the representative wavelength of the exposure light is less than 10%) and defects can be reduced. In addition, the etching rate of each layer of the light-shielding film 12 can be made uniform, so that the cross-sectional shape of the light-shielding film pattern can be closer to vertical.

(d) The first reflection suppression layer 13 and the second reflection suppression layer 15 preferably have regions in which the content of at least any element of O and N changes continuously or stepwise along the film thickness direction. By changing the composition of each layer of the first reflection suppression layer 13 and the second reflection suppression layer 15, the difference in the etching rate in each layer can be reduced, and the cross-sectional shape of the light-shielding film pattern can be closer to vertical.

(e) The light-shielding layer 14 preferably has a chromium content of 97 atomic% to 100 atomic %. By forming the light-shielding layer 14 with chromium that does not substantially contain O, N, and F, the unevenness of the in-plane composition due to the inclusion of O, N, and F can be suppressed. Thereby, the front reflectivity and the back reflectivity of the light shielding film 12 can be made more uniform in the base surface of the photomask.

(f) Preferably, in the first reflection suppression layer 13, the ratio of O to N in the first high chromium oxide layer 13b is 2.5-10. By forming the above-mentioned O/N ratio, the reflectance of the first reflection suppression layer 13 can be reduced, and the etching with other layers (light-shielding layer: especially the content of chromium is 97-100 atomic%) can be reduced. The difference in speed.

(g) Preferably, in the second reflection suppression layer 15, the ratio of O to N in the second high chromium oxide layer 15b is 2.5-10. By configuring to achieve the above-mentioned O/N ratio, the reflectance of the second reflection suppression layer 15 can be reduced. In addition, the adhesion with the resist film formed on the front surface of the second low chromium oxide layer 15a can be improved, so that the cross-sectional shape of the light-shielding film pattern can be more stably close to vertical.

(h) It is preferable that at least one of the first reflection suppression layer 13 and the second reflection suppression layer 15 further includes C. Thereby, the difference in the etching rate between the first reflection suppression layer 13 and the second reflection suppression layer 15 and the light shielding layer 14 can be reduced. Especially when the chromium content of the light-shielding layer 14 is 97 atomic% to 100 atomic %, the difference can be made smaller.

(i) The photomask substrate 1 has the following optical characteristics: by providing the above-mentioned light-shielding film 12, the reflectivity of the front and back surfaces in the exposure wavelength range of 300 nm to 436 nm are both 15% or less, and the front surface reflection in the above-mentioned wavelength range The wavelength dependence of each of the reflectance and the back reflectance is 12% or less. In addition, the photomask substrate 1 has the following optical characteristics: by providing the above-mentioned light-shielding film 12, the reflectance of the front and back surfaces in the exposure wavelength range of 365 nm to 436 nm is 10% or less, and the reflectance of the front surface in the above-mentioned wavelength range The wavelength dependence of each of and the back reflectance is 5% or less. According to this photomask substrate 1, when irradiating exposure light as a photomask, the light-shielding film 12 can cover all wavelength bands with an exposure wavelength of 300 nm to 436 nm or all wavelength bands with an exposure wavelength of 365 nm to 436 nm. Suppress the front and back sides The reflection of light can reduce the total amount of reflected light on the front and back. In particular, the wavelength dependence of the back surface reflectance of the light shielding film 12 can be set to 5% or less, and the back surface reflectance can be averagely reduced in the entire frequency band of the above-mentioned wavelength range, so that the back light toward the back surface of the mask can be suppressed. As a result, it is possible to suppress the reduction in the accuracy of the transfer pattern caused by the reflection of light on the front and back of the mask when the display device is manufactured using the mask.

(j) It is preferable that the back reflectance of the photomask substrate 1 is lower than the front reflectance in the entire frequency band of the exposure wavelength range of 300 nm to 436 nm. Or preferably, the back reflectance of the photomask substrate 1 is lower than the front reflectance in the entire frequency band of the exposure wavelength range of 365 nm to 436 nm. As a result, the reflection of the exposed light can be suppressed over a wide range of wavelength bands, and the total amount of the reflected light of the exposure can be further reduced.

(k) It is preferable that the wavelength dependence of the back reflectance of the mask substrate 1 is within the range of 300 nm to 436 nm of exposure wavelength than the wavelength dependence of the front reflectance. Or it is preferable that the wavelength dependence of the back reflectance of the mask substrate 1 in the entire frequency band of the exposure wavelength range of 365 nm to 436 nm is smaller than the wavelength dependence of the front reflectance. That is, it is preferable that within the above-mentioned wavelength range, the amount of change in back reflectance is smaller than the amount of change in front reflectance. Thereby, the return light on the back of the photomask can be further suppressed, so that the reduction in the accuracy of the transfer pattern can be further reduced.

(l) According to the photomask base 1, since the front surface reflectance of the light-shielding film 12 is low, when a resist film is provided on the light-shielding film 12 and the resist pattern is formed by the drawing and development steps, the drawing light can be reduced Reflection on the front side of the shading film 12. Thereby, the dimensional accuracy of the resist pattern can be improved, and the dimensional accuracy of the light-shielding film pattern of the photomask thus formed can be improved. Specifically, the CD uniformity of the light-shielding film pattern can be improved, so that a high-precision light-shielding film pattern below 75 nm can be formed.

(m) The photomask made from the photomask substrate 1 is highly accurate due to the high precision of the light-shielding film pattern, and the reflectivity of the front and back of the light-shielding film pattern is small, and the in-plane uniformity of the reflectivity is relatively high. When the transfer body transfers the pattern, higher transfer characteristics can be obtained.

<Other embodiments> As mentioned above, one embodiment of the present invention has been described in detail, but the present invention is not limited to the above-mentioned embodiment, and can be appropriately changed without departing from the gist of the present invention.

In the above-mentioned embodiment, the case where the light-shielding film 12 is directly provided on the transparent substrate 11 has been described, but the present invention is not limited to this. For example, it may also be a mask base provided with a semi-transmissive film having an optical density lower than that of the light-shielding film 12 between the transparent substrate 11 and the light-shielding film 12. In the mask base on which the semi-transmissive film and the light-shielding film 12 are formed on the transparent substrate 11, it is also preferable that the semi-transparent film is in the range of the exposure wavelength of 300 nm to 436 nm. The reflectivity is below 15%, and the frontal reflectivity of the shading film is below 15%. In addition, in the mask base on which the semi-transparent film and the light-shielding film 12 are formed on the transparent substrate 11, it is preferable that the semi-transparent film faces the back of the exposed light within the range of the exposure wavelength of 365 nm to 436 nm. The reflectivity is below 10%, and the front reflectivity of the shading film is below 10%. The mask substrate can be used as a gray-scale mask (or graytone mask) with the effect of reducing the number of mask sheets used in manufacturing the display device. The light-shielding film pattern in the gray-scale mask (or graytone mask) becomes a semi-transmissive film pattern and/or a light-shielding film pattern.

In addition, a phase shift film that shifts the phase of transmitted light may be provided between the transparent substrate 11 and the light-shielding film 12 instead of the photomask base of the semi-transparent film. In the mask base on which the phase shift film and the light-shielding film 12 are formed on the transparent substrate 11, it is also preferable that the phase shift film is in the range of the exposure wavelength of 300 nm to 436 nm. The reflectivity is below 15%, and the frontal reflectivity of the shading film is below 15%. In addition, in the photomask base on which the phase shift film and the light shielding film 12 are formed on the transparent substrate 11, it is preferable that the phase shift film is in the range of the exposure wavelength of 365 nm to 436 nm. The reflectivity is below 10%, and the front reflectivity of the shading film is below 10%. The photomask substrate can be used as a phase shift photomask with a higher pattern resolution effect brought by the phase shift effect. The light shielding film pattern in the phase shift mask becomes a phase shift film pattern or a phase shift film pattern and a light shielding film pattern.

Regarding the above-mentioned semi-transmissive film and phase shift film, a material having etching selectivity to the chromium-based material constituting the light-shielding film 12 is suitable. As such materials, metal silicide-based materials containing molybdenum (Mo), zirconium (Zr), titanium (Ti), tantalum (Ta), and silicon (Si) can be used, and further containing oxygen, nitrogen, carbon, or fluorine At least one of the materials is more suitable. For example, MoSi, ZrSi, TiSi, TaSi, MoZrSi, MoTiSi, MoTaSi and other metal silicides, oxides of metal silicides, nitrides of metal silicides, oxynitrides of metal silicides, carbonitrides of metal silicides, Oxycarbide of metal silicide and carbonitride of metal silicide are more suitable. In addition, these semi-light transmissive films or phase shift films may also be laminated films composed of the above-mentioned films exemplified as functional films.

Furthermore, in the above-mentioned embodiment, an etching mask film made of a material having an etching selectivity with the light-shielding film 12 may also be formed on the light-shielding film 12.

In addition, in the above-mentioned embodiment, an etching stopper film made of a material having an etching selectivity with the light shielding film may also be formed between the transparent substrate 11 and the light shielding film 12. The above-mentioned etching mask film and etching stopper film are composed of a material having an etching selectivity to a chromium-based material constituting the light-shielding film 12. Examples of such materials include metal silicide-based materials containing molybdenum (Mo), zirconium (Zr), titanium (Ti), tantalum (Ta), and silicon (Si), or Si, SiO, SiO ₂ , SiON, and Si ₃ N ₄ and other silicon-based materials. [Example]

Next, the present invention will be further described in detail based on examples, but the present invention is not limited to these examples.

<Example 1> In this embodiment, an in-line sputtering device is used, and the first low chromium oxide layer is produced on a transparent substrate with a substrate size of 1220 mm×1400 mm as shown in FIG. 1 according to the sequence shown in the above embodiment. , The first high chromium oxide layer, the light-shielding layer, the second low chromium oxide layer, and the second high chromium oxide layer are sequentially laminated to form a mask base with a light-shielding film.

Regarding the film forming conditions of the first low chromium oxide layer and the second high chromium oxide layer, the first low chromium oxide layer with a relatively small ratio of O to N and the first low chromium oxide layer with a relatively large ratio of O to N For the method of high chromium oxide layer, the sputtering target is set as the Cr sputtering target. Regarding the flow rate of the reactive gas, select the flow rate of the oxygen-based gas from the range of 1 to 45 sccm in a metal mode, from 30 to 60 sccm The range selects the flow rate of nitrogen-based gas, the flow rate of hydrocarbon-based gas is selected from the range of 1-15 sccm, the flow rate of rare gas is selected from the range of 20-100 sccm, and the target applied power is set in the range of 1.0-6.0 kW.

Regarding the film forming conditions of the light-shielding layer, the sputtering target is set as the Cr sputtering target, the flow rate of the rare gas is set in the range of 60-200 sccm, and the target application power is set in the range of 3.0-10.0 kW.

Regarding the film formation conditions of the second low chromium oxide layer and the second high chromium oxide layer, the second low chromium oxide layer has a relatively small ratio of O to N, and the second low chromium oxide layer has a relatively large ratio of O to N. For the method of high chromium oxide layer, the sputtering target is set as the Cr sputtering target. Regarding the flow rate of the reactive gas, select the flow rate of the oxygen-based gas from the range of 1 to 45 sccm in a metal mode, from 30 to 60 sccm The range selects the flow rate of nitrogen-based gas, the flow rate of hydrocarbon-based gas is selected from the range of 1-15 sccm, the flow rate of rare gas is selected from the range of 20-100 sccm, and the target applied power is set in the range of 1.0-6.0 kW.

Regarding the obtained light-shielding film of the mask base, the composition in the film thickness direction was measured by X-ray photoelectron spectroscopy (XPS). As a result, it was confirmed that each layer in the light-shielding film had the composition distribution shown in FIG. 2. 2 is a graph showing the results of composition analysis in the film thickness direction in the mask substrate of Example 1. The horizontal axis represents the film thickness, and the vertical axis represents the element content [atom %]. The film thickness represents the depth [nm] from the front surface of the light-shielding film.

In Fig. 2, the area containing about 15 atomic% of carbon (C) near the front surface of the light-shielding film is the front natural oxide layer. The area from the front surface of the light-shielding film (excluding the front natural oxide layer) with a depth of about 1.3 nm to about 14 nm is the second high chromium oxide layer, and the ratio of oxygen (O) to nitrogen (N) is 2.5 or more. The area from the front side of the light-shielding film (except the natural oxide layer on the front side) with a depth of about 15 nm to about 43 nm is the second low chromium oxide layer, and the ratio of oxygen (O) to nitrogen (N) is less than 2.5. The area from the front side of the shading film (except the natural oxide layer on the front side) with a depth of about 44 nm to about 66 nm is the transition layer. The area from the front surface of the light-shielding film (except the natural oxide layer on the front side) with a depth of about 67 nm to about 156 nm is the light-shielding layer, and the content of chromium (Cr) is more than 97 atomic%. The area from the front side of the shading film (except the natural oxide layer on the front side) with a depth of about 157 nm to about 164 nm is the transition layer. The area from about 165 nm to about 188 nm deep from the front surface of the light-shielding film (except the natural oxide layer on the front side) is the first high chromium oxide layer, and the ratio of oxygen (O) to nitrogen (N) is 2.5 or more. The area from the front side of the shading film (except the natural oxide layer on the front side) with a depth of about 189 nm to a depth of 195 nm is the first low chromium oxide layer, and the ratio of oxygen (O) to nitrogen (N) is less than 2.5. The area where the ratio of oxygen (O) to silicon (Si) is about 2 is the transparent substrate, and the area between the transparent substrate and the first low chromium oxide layer is the transition layer.

As shown in Figure 2, the first low chromium oxide layer is a CrCON film, which contains 54.2-56.5 atomic% of Cr, 12.0-14.2 atomic% of N, 14.8-15.1 atomic% of O, and 2.7 to 4.3 atomic% of C. The ratio of O to N (O/N ratio) is 1.9 to 2.4.

The first high chromium oxide layer is a CrCON film, which contains 57.1-90.7 atomic% of Cr, 2.0-11.3 atomic% of N, 7.3-28.3 atomic% of O, and 0-3.3 atomic% of C. The ratio of O to N (O/N ratio) is 2.5 to 3.6.

The light-shielding layer is a CrO film, which contains 97.4-99.1 at% of Cr and 0.9-2.6 at% of O.

The second low chromium oxide layer is a CrCON film, containing 49.3-76.9 atomic% of Cr, 6.2-18.9 atomic% of N, 24.4-32.5 atomic% of O, and 2.9-5.2 atomic% of C. The ratio of O to N (O/N ratio) is 1.3 to 2.4.

The second high chromium oxide layer is a CrCON film, which contains 42.3 to 49.0 atomic% of Cr, 8.7 to 12.4 atomic% of N, 35.3 to 44.8 atomic% of O, and 2.2 to 4.2 atomic% of C. The ratio of O to N (O/N ratio) is 2.9 to 5.2.

(Evaluation of mask substrate) Regarding the photomask substrate of Example 1, the optical density of the light-shielding film and the reflectance of the front and back surfaces of the light-shielding film were evaluated by the methods shown below.

For the mask substrate of Example 1, the optical density of the light-shielding film was measured by a spectrophotometer ("SolidSpec-3700" manufactured by Shimadzu Corporation). The result was that the g-line (wavelength 436 nm) is 5.0 or more. In addition, the reflectance of the front and back of the light-shielding film was measured by a spectrophotometer ("SolidSpec-3700" manufactured by Shimadzu Corporation). Specifically, the reflectance on the second reflection suppression layer side of the light-shielding film (front reflectance) and the reflectance on the transparent substrate side of the light-shielding film (back reflectance) were measured by a spectrophotometer. As a result, the reflectance spectrum shown in Figure 3 is obtained. Fig. 3 shows the reflectance spectra of the front and back of the photomask substrate of Example 1. The horizontal axis represents the wavelength [nm], and the vertical axis represents the reflectance [%]. As shown in FIG. 3, it was confirmed that the photomask substrate of Example 1 can greatly reduce the reflectance for light of a wide range of wavelengths. Specifically, at a wavelength of 300 nm to 436 nm, the front reflectance of the shading film is below 15.0% (12.2% (wavelength 300 nm), 10.9 nm (wavelength 313 nm), 8.2% (wavelength 334 nm), 4.3% (Wavelength 365 nm), 1.8% (wavelength 405 nm), 1.7% (wavelength 413 nm), 2.0% (wavelength 436 nm)), under the wavelength of 365 nm ~ 436 nm, the front reflectivity of the shading film is below 10.0% (4.3% (wavelength 365 nm), 1.8% (wavelength 405 nm), 1.7% (wavelength 413 nm), 2.0% (wavelength 436 nm)). In addition, the back surface reflectance of the light-shielding film is 7.5% or less (7.4% (wavelength 300 nm), 6.2% (wavelength 313 nm), 3.9% (wavelength 334 nm) at wavelengths of 350 nm to 436 nm and wavelengths of 365 nm to 436 nm ), 1.7% (wavelength 365 nm), 0.9% (wavelength 405 nm), 2.1% (wavelength 436 nm)). In addition, the dependence of the front reflectance of the light-shielding film within the exposure wavelength range of 300 nm to 436 nm is 10.6%, and the dependence of the back reflectance is 6.6%. In addition, the dependence of the front reflectance of the light-shielding film in the exposure wavelength range of 365 nm to 436 nm is 2.7%, and the dependence of the back reflectance is 1.3%, which is good. In the wavelength band spanning from 300 nm to 500 nm, the wavelength (peak-valley wavelength) corresponding to the minimum value (peak-valley) of the front reflectance and the back reflectance is the front reflectance of 436 nm, and the back reflectance of 415.5 nm.

(Evaluation of shading film pattern) The mask base of Example 1 is used to form a light-shielding film pattern on a transparent substrate. Specifically, after forming a novolak-based positive resist film on a light-shielding film on a transparent substrate, laser drawing (wavelength 413 nm) and development are performed to form a resist pattern. After that, the resist pattern is used as a mask and wet etching is performed with a chromium etching solution to form a light-shielding film pattern on the transparent substrate. The evaluation of the light-shielding film pattern was performed by observing the cross-sectional shape of the light-shielding film pattern by a scanning electron microscope (SEM) after forming a 2.5 μm line and gap pattern. As a result, it was confirmed that the angle formed by the side surface of the light-shielding film pattern and the transparent substrate was 77°. Based on this situation, it was confirmed that the cross-sectional shape of the light-shielding film pattern can be formed in a nearly vertical state.

(In-plane uniformity of reflectance) The in-plane uniformity of the front reflectance of the light-shielding film of the obtained mask substrate was measured. The in-plane uniformity of the front reflectance was calculated based on the evaluation result of the front reflectance measured at 11×11=121 points in the substrate surface excluding the 50 mm periphery of the substrate with a reflectance meter, and the result was 2.0% (Scope). In addition, the back surface reflectance was calculated as described above for the in-plane uniformity of the back surface reflectance of the light-shielding film using the dummy substrate, and the result was 3.5% (range).

As in Example 1 above, with regard to the light-shielding film of the mask base, the first reflection-inhibiting layer, the light-shielding layer, and the second reflection-inhibiting layer are laminated from the transparent substrate side, and each layer is formed into a specific composition. When patterned by wet etching, the cross-sectional shape of the light-shielding film pattern is formed to be vertical. In addition, it was confirmed that the first reflection suppression layer and the second reflection suppression layer were formed into a laminated structure of a low chromium oxide layer and a high chromium oxide layer from the transparent substrate side, respectively, so that defects could be reduced, and a specific composition could be obtained. Each layer is constructed by the method, so the in-plane uniformity of the reflectivity of the front and back of the light-shielding film is relatively high.

(Making of Mask) Then, the mask substrate of Example 1 was used to make a mask. First, a novolak-based positive resist is formed on the light-shielding film of the mask substrate. Next, a laser drawing device is used to draw a pattern of a circuit pattern for a TFT (thin-film transistor) panel on the resist film, and then a specific resist pattern (the above-mentioned circuit pattern is formed by developing and cleaning). The minimum line width is 0.75 μm). After that, the resist pattern is used as a mask, and the light shielding film is patterned by wet etching using a chromium etching solution, and finally the resist pattern is peeled off with a resist stripping solution to obtain a light shielding film formed on a transparent substrate Pattern (shading film pattern) mask. The aperture ratio of the light-shielding film pattern (light-shielding film pattern) formed on the transparent substrate of the mask, that is, the exposure ratio of the transparent substrate without the light-shielding film pattern in the area of the entire surface of the mask with the light-shielding film pattern formed Is 45%. The light-shielding film pattern of the mask was observed by a scanning electron microscope (SEM), and as a result, the cross-sectional shape of the light-shielding film pattern was 77°, which was good. The CD uniformity of the light-shielding film pattern of the mask was measured by "SIR8000" manufactured by Seiko Instruments Nano Technologies Co., Ltd. The CD uniformity is measured at 11×11 locations in an area of 1100 mm×1300 mm excluding the peripheral area of the substrate. As a result, the CD uniformity is less than 60 nm, and the CD uniformity of the obtained photomask is good.

(Production of LCD panel) The photomask produced in this Example 1 was set on the mask stage of the exposure device, and the transferred body on which the resist film was formed on the substrate for the display device (TFT) was subjected to pattern exposure to produce a TFT array. As the exposure light, composite light including i-line with a wavelength of 365 nm, h-line with a wavelength of 405 nm, and g-line with a wavelength of 436 nm is used. The fabricated TFT array is combined with color filters, polarizing plates, and backlight devices to fabricate TFT-LCD panels. As a result, a TFT-LCD panel without display unevenness was obtained. It is believed that the reason is that when a photomask is used for pattern exposure, the reflection of light on the front and back surfaces can be suppressed to reduce the total amount of reflected light, and the in-plane uniformity of reflectance can be improved.

(Reference example 1) In Reference Example 1, the first reflection suppression layer is a single-layer chromium oxide layer, the second reflection suppression layer is a multilayer structure of a high chromium oxide layer and a low chromium oxide layer from the transparent substrate side, and the light-shielding layer is provided Except for CrON, the mask substrate was produced in the same manner as in Example 1.

Regarding the film formation conditions of the first reflection suppression layer, the sputtering target is set as the Cr sputtering target, and the flow rate of the reactive gas is selected from the range of 5 to 45 sccm so that the flow rate of the reactive gas becomes the metal mode. Select the flow rate of nitrogen-based gas from the range of 30-60 sccm, select the flow rate of the rare gas from the range of 60-150 sccm, and set the target applied power in the range of 2.0-6.0 kW.

Regarding the film forming conditions of the light-shielding layer, the sputtering target was set as the Cr sputtering target. Regarding the flow rate of the reactive gas, the flow rate of the nitrogen-based gas was selected from the range of 1 to 60 sccm so as to become the metal mode, from 60 to 60 sccm. Select the flow rate of the rare gas in the range of 200 sccm, and set the target applied power in the range of 3.0 to 7.0 kW.

Regarding the film formation conditions of the second reflection suppression layer, the sputtering target is set as the Cr sputtering target, and the flow rate of the reactive gas is selected from the range of 8 to 45 sccm so that the flow rate of the reactive gas becomes the metal mode. Select the flow rate of nitrogen-based gas from the range of 30-60 sccm, select the flow rate of the rare gas from the range of 60-150 sccm, and set the target applied power in the range of 2.0-6.0 kW.

Regarding the obtained light-shielding film of the mask base, the composition in the film thickness direction was measured by XPS in the same manner as in Example 1. As a result, it was confirmed that each layer in the light-shielding film had the composition distribution shown in FIG. 4. 4 is a graph showing the result of composition analysis in the film thickness direction in the mask substrate of Reference Example 1. The horizontal axis represents the film thickness, and the vertical axis represents the element content [atom %]. The film thickness represents the depth [nm] from the front surface of the light-shielding film.

In FIG. 4, the area containing about 21 atomic% of carbon (C) near the front surface of the light-shielding film is the front natural oxide layer. Except for the front side natural oxide layer where the ratio of oxygen (O) to nitrogen (N) is less than 2.5, the area with a depth of about 5 nm to a depth of about 15 nm from the front of the shading film is a low chromium oxide layer. Except for the natural oxide layer on the front surface where the ratio of oxygen (O) to nitrogen (N) is 2.5 or more, the high chromium oxide layer is the area with a depth of about 16 nm to a depth of about 34 nm from the front surface of the light-shielding film. Except for the natural oxide layer on the front side, the region from the depth of about 35 nm to the depth of about 89 nm from the front surface of the shading film is the transition layer. The area with a depth of about 90 nm to about 208 nm from the front surface of the light-shielding film except the natural oxide layer on the front side is the light-shielding layer. Except for the natural oxide layer on the front side, the region from the depth of about 209 nm to the depth of about 227 nm from the front side of the shading film is the transition layer. Except for the natural oxide layer on the front side, the area from the depth of about 228 nm to the depth of about 251 nm from the front surface of the shading film is the first reflection suppression layer. The area where the ratio of oxygen (O) to silicon (Si) is approximately 2 is the transparent substrate, and the area between the transparent substrate and the first reflection suppression layer is the transition layer.

As shown in FIG. 4, the first reflection suppression layer is a CrCON film, which contains 51.4 to 57 atomic% of Cr, 13.5-18.2 atomic% of N, 22.6 to 31.6 atomic% of O, and 2.8 to 4.8 atomic% of C. The light-shielding layer is a CrON film, which contains 85.4-91.9 atomic% of Cr, 7.4-9.3 atomic% of N, and 0.5-6.0 atomic% of O. The second reflection suppression layer is composed of a high chromium oxide layer and a low chromium oxide layer. The high chromium oxide layer is a CrCON film, containing 49.0-50.6 atomic% of Cr, 9.1-13.0 atomic% of N, 33.7-39.4 atomic% of O, and 2.2-2.9 atomic% of C. The low chromium oxide layer is a CrCON film, containing 50.0-51.1 atomic% of Cr, 13.5-14.1 atomic% of N, 31.8-33.4 atomic% of O, and 2.5 to 3.5 atomic% of C.

(Evaluation of mask substrate) Regarding the mask substrate of Reference Example 1, the optical density of the light-shielding film was measured in the same manner as in Example 1. As a result, the g-line (wavelength: 436 nm), which is the wavelength region of the exposure light, was 5.0 or more. In addition, the reflectance of the front and back of the light-shielding film was measured by a spectrophotometer, and as a result, the reflectance spectrum shown in FIG. 5 was obtained. Figure 5 shows the reflectance spectra of the front and back of the photomask substrate of Comparative Example 1. The horizontal axis represents the wavelength [nm], and the vertical axis represents the reflectance [%]. As shown in FIG. 5, it was confirmed that the mask substrate of Reference Example 1 can greatly reduce the reflectance of light of a wide range of wavelengths, similarly to Example 1. Specifically, at a wavelength of 300 nm to 436 nm, the front reflectance of the shading film is 15.0% or less (15.0% (wavelength 300 nm), 13.3% (wavelength 313 nm), 7.7% (wavelength 365 nm), 1.8% (Wavelength 405 nm), 1.1% (wavelength 413 nm), 0.3% (wavelength 436 nm)), at a wavelength of 365 nm to 436 nm, the front reflectance of the shading film is below 10.0% (7.7% (wavelength 365 nm) , 1.8% (wavelength 405 nm), 1.1% (wavelength 413 nm), 0.3% (wavelength 436 nm)). In addition, it was confirmed that the back surface reflectance of the light-shielding film is 15.0% or less (12.2% (wavelength 300 nm), 10.4% (wavelength 313 nm), 6.2% (wavelength 365 nm), 4.7% at a wavelength of 300 nm to 436 nm (Wavelength 405 nm), 4.8% (wavelength 436 nm)), at a wavelength of 365 nm to 436 nm, the back reflectance of the shading film is below 7.5% (6.2% (wavelength 365 nm), 4.7% (wavelength 405 nm) , 4.8% (wavelength 436 nm)). At a wavelength of 350 nm to 436 nm, the reflectivity of the front and back of the shading film can be reduced to less than 15%, or at a wavelength of 365 nm to 436 nm, the reflectivity of the front and back of the shading film can be reduced to 10 % Or less, especially for the reflectance of light with a wavelength of 436 nm, the front reflectance can be 0.3%, and the back reflectance can be 4.8%.

The in-plane uniformity of the front reflectance of the light-shielding film of the obtained mask base was measured. Using a reflectance meter, measure 11×11=121 points in the surface of the substrate except 50 mm of the peripheral edge of the substrate to obtain the evaluation result of the front reflectance, and calculate the in-plane uniformity of the front reflectance based on the evaluation result. 3.9% (range). In addition, the back surface reflectance was calculated as described above, and the in-plane uniformity of the back surface reflectance of the light-shielding film using the dummy substrate was calculated. As a result, it exceeded 5.0% (range), and the unevenness of the reflectance was visually confirmed.

(Evaluation of shading film pattern) Regarding the mask substrate of the reference example, the light-shielding film pattern was formed and evaluated in the same manner as in Example 1. The light-shielding film pattern was observed by SEM, and as a result, it was confirmed that the cross-sectional shape of the light-shielding film pattern was continuously inclined from vertical to a tapered shape. The angle formed by the side surface of the light-shielding film pattern and the transparent substrate was measured, and the result was confirmed to be 54°.

Then, using the mask base of the reference example, a mask was produced in the same manner as in Example 1. The CD uniformity of the light-shielding film pattern of the obtained mask was measured, and the result was poor, which was 100 nm. As mentioned above, although the mask substrate of the reference example can reduce the reflectivity of the front and back surfaces, it fails to form a high-precision mask pattern.

1: Mask base 11: Transparent substrate 12: Shading film 13: The first reflection suppression layer 13a: The first low chromium oxide layer 13b: The first high chromium oxide layer 14: shading layer 15: The second reflection suppression layer 15a: The second low chromium oxide layer 15b: The second high chromium oxide layer

FIG. 1 is a cross-sectional view showing a schematic configuration of a photomask substrate according to an embodiment of the present invention. FIG. 2 is a diagram showing the result of composition analysis in the film thickness direction in the mask substrate of Example 1. FIG. 3 is a graph showing the reflectance spectra of the front and back of the photomask substrate of Example 1. FIG. 4 is a diagram showing the result of composition analysis in the film thickness direction in the mask substrate of Reference Example 1. FIG. FIG. 5 is a graph showing the reflectance spectra of the front and back surfaces of the photomask substrate of Reference Example 1. FIG.

1: Mask base

11: Transparent substrate

12: Shading film

13: The first reflection suppression layer

13a: The first low chromium oxide layer

13b: The first high chromium oxide layer

14: shading layer

15: The second reflection suppression layer

15a: The second low chromium oxide layer

15b: The second high chromium oxide layer

Claims (16)

A photomask substrate, which is characterized in that it is used when manufacturing the photomask for display device manufacturing, and has: A transparent substrate, which includes a material that is substantially transparent to exposed light; and A light-shielding film, which is disposed on the above-mentioned transparent substrate and includes a material that is substantially opaque to the above-mentioned exposed light; The light-shielding film includes a first reflection-inhibiting layer, a light-shielding layer, and a second reflection-inhibiting layer from the transparent substrate side, and The first reflection suppression layer includes in order from the transparent substrate side: a first low chromium oxide layer containing chromium, oxygen, and nitrogen, and the ratio of oxygen to nitrogen is relatively small; and a first high chromium oxide layer, It contains chromium, oxygen and nitrogen, and the ratio of oxygen to nitrogen is relatively high; The second reflection suppression layer includes in order from the transparent substrate side: a second low chromium oxide layer containing chromium, oxygen, and nitrogen, and the ratio of oxygen to nitrogen is relatively small; and a second high chromium oxide layer, It contains chromium, oxygen and nitrogen, and the ratio of oxygen to nitrogen is relatively high; At least the first reflection suppression layer, the light-shielding layer, the light-shielding layer, the light-shielding layer, the light-shielding layer, And the composition and film thickness of the above-mentioned second reflection suppression layer. The photomask substrate of claim 1, wherein the light-shielding layer is formed of a chromium-based material with a chromium content of 97 atomic% or more and 100 atomic% or less. The photomask substrate of claim 1 or 2, wherein the ratio of oxygen to nitrogen in the second high chromium oxide layer is 2.5 or more and 10 or less. The photomask substrate of claim 1 or 2, wherein the ratio of oxygen to nitrogen in the first high chromium oxide layer is 2.5 or more and 10 or less. The photomask substrate of claim 1 or 2, wherein the first reflection suppression layer contains carbon. The photomask substrate of claim 1 or 2, wherein the second reflection suppression layer contains carbon. For the photomask substrate of claim 1 or 2, wherein the chromium content of the first reflection suppression layer is 25 at% or more and 75 at% or less, the oxygen content is 15 at% or more and 45 at% or less, and nitrogen The content rate is 2 atomic% or more and 30 atomic% or less, The chromium content of the second reflection suppression layer is 25 atomic% or more and 75 atomic% or less, the oxygen content is 15 atomic% or more and 60 atomic% or less, and the nitrogen content is 2 atomic% or more and 30 atomic% the following. The mask substrate of claim 1 or 2, wherein the first reflection suppressing layer and the second reflection suppressing layer respectively have a content ratio of at least any element of oxygen and nitrogen continuously or stepwise along the film thickness direction The area of composition change. The photomask base of claim 1 or 2, which is between the transparent substrate and the first reflection suppressing layer, between the first reflection suppressing layer and the light shielding layer, and between the light shielding layer and the second reflection suppressing layer There is a gradient composition region in which the elements constituting the first reflection suppression layer, the light shielding layer, and the second reflection suppression layer continuously constitute a gradient change. The mask substrate of claim 1 or 2, wherein the in-plane uniformity of the reflectance of the front surface of the light-shielding film to the exposure wavelength of the light to be exposed is 3% or less. According to claim 1 or 2, the photomask base further includes between the transparent substrate and the light-shielding film: a semi-transparent film having an optical density lower than that of the light-shielding film. The photomask base of claim 1 or 2 further includes a phase shift film between the transparent substrate and the light shielding film. A method for manufacturing a photomask is characterized by the following steps: Prepare the above-mentioned mask substrate as in any one of Claims 1 to 12; and A resist film is formed on the light-shielding film, and the light-shielding film is etched using the resist pattern formed of the resist film as a mask to form a light-shielding film pattern on the transparent substrate. A method for manufacturing a photomask is characterized by the following steps: Prepare the above-mentioned mask substrate as in any one of claims 1 to 12; Forming a resist film on the light-shielding film, etching the light-shielding film using the resist pattern formed by the resist film as a mask to form a light-shielding film pattern on the transparent substrate; and The translucent film is etched using the light-shielding film pattern as a mask to form a translucent film pattern on the transparent substrate. A method for manufacturing a photomask is characterized by the following steps: Prepare the above-mentioned mask substrate as in any one of claims 1 to 12; Forming a resist film on the light-shielding film, etching the light-shielding film using the resist pattern formed by the resist film as a mask to form a light-shielding film pattern on the transparent substrate; and The phase shift film is etched using the light-shielding film pattern as a mask to form a phase shift film pattern on the transparent substrate. A method of manufacturing a display device, characterized by having: an exposure step, which places the photomask obtained by the manufacturing method of the photomask according to any one of claims 13 to 15 on the mask stage of the exposure device, At least one of the light-shielding film pattern formed on the photomask, the semi-transparent film pattern, and the phase shift film pattern is exposed and transferred to the resist formed on the substrate of the display device.

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