TW201932975A - Photomask blank and method of manufacturing photomask, and method of manufacturing display device capable of forming patterns with fine and high accuracy and suppressing display unevenness - Google Patents

Abstract

The present invention provides a photomask blank which satisfies the following optical characteristics, that is, a photomask pattern having high precision can be obtained when a photomask is produced by etching, and display unevenness can be suppressed when a display device is produced using a photomask. The present invention relates to a photomask blank which is characterized in that the photomask is for use in manufacturing a display device, and is composed of: a transparent blank that is made of a material substantially transparent to the exposed light; and a light shielding film disposed on the transparent blank and made of a material substantially opaque to the exposed light; and the light shielding film includes a first reflection suppressing layer, a light shielding layer, and a second reflection suppressing layer from the transparent blank side; if the surface on the light shielding film side of both surfaces of the photomask base is set as a front surface, and the surface on the transparent blank side is set as a back surface, within a exposure wavelength of 365 nm to 436 nm, the front reflectance and the back reflectance of the exposed light are each 10% or less, and the wavelength dependence of the back reflectance in the above wavelength range is 5% or less.

Description

Photomask substrate and method for manufacturing photomask, and method for manufacturing display device

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

In a display device such as an FPD (Flat Panel Display) represented by an LCD (Liquid Crystal Display), high-definition and high-speed display have been rapidly developed with a large screen and a wide viewing angle. One of the elements required for such high-definition and high-speed display is to produce an electronic circuit pattern such as a component or a wiring which is fine and has high dimensional accuracy. In the patterning of the electronic circuit of the display device, the photolithography method is often used. Therefore, there is a need for a photomask for manufacturing a display device having a fine and highly precise pattern.

A photomask for manufacturing a display device is fabricated from a photomask substrate. The mask base is formed by providing a light-shielding film made of a material opaque to the exposed light on a transparent substrate including synthetic quartz glass or the like. In the mask base or the reticle, in order to suppress reflection of light during exposure, a reflection suppressing layer is provided on both sides of the front surface and the back surface of the light shielding film, and the mask substrate is, for example, sequentially laminated with the first reflection from the transparent substrate side. A film structure comprising a suppression layer, a light shielding layer, and a second reflection suppressing layer. The mask is produced by patterning a light-shielding film of a mask base by wet etching or the like to form a specific mask pattern.

A technique relating to such a mask for manufacturing a display device, a mask base to be used as a master, and a method of manufacturing the same are disclosed in Patent Document 1.
[Previous Technical Literature]
[Patent Literature]

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

[The problem that the invention wants to solve]

In the manufacture of a display device (for example, a TV (Television) display panel), pattern transfer is repeated, for example, by transferring a specific pattern to a substrate for a display device using a photomask, and then displaying the image. The device slides with the substrate and transfers a specific pattern. In the transfer, there is a case where the reflected light of the back side of the mask or the light of the exposed light passes through the mask and returns from the reflected light of the transferred body due to the light from the exposure device being incident on the mask. The effect of the reflected light generated on the front side of the mask is irradiated to the vicinity of the overlapping portion of the display device by the above-mentioned exposure light. As a result, adjacent patterns are exposed so as to partially overlap each other, and display unevenness occurs in the display device manufactured. In particular, in the manufacture of a display device, as the size of the mask is increased, there is a case where light of a wide wavelength band (combined light including a plurality of lights having different wavelengths) is used as the light of exposure, and display unevenness is present. Become more prominent.

Therefore, in order to suppress display unevenness in the mask substrate, it is required to set the reflectance of the front surface and the back surface of the light shielding film to 10% or less (for example, a wavelength of 365 nm to 436 nm), and more preferably 5% or less (for example, , 400 nm to 436 nm). Further, in view of improving the CD uniformity (CD (Uniformity) Uniformity) of the photomask, if the front side reflection of the laser light from the light shielding film is considered, the reflectance of the front surface of the light shielding film is required. It is set to 5% or less (for example, a wavelength of 413 nm), and more preferably 3% or less (for example, a wavelength of 413 nm).

In addition to the demand for high definition and high-speed display of the display device, the size of the substrate has been increasing. In recent years, the length of the display device used in the manufacture of the short side is 850 mm. The super large reticle of the above rectangular substrate. Furthermore, as a large-sized mask having a short side length of 850 mm or more, there are 850 mm × 1200 mm size for G7, 1220 mm × 1400 mm size for G8, and 1620 mm × 1780 mm size for G10, especially As a CD uniformity of the mask pattern in such a large mask, a high-precision mask pattern of 100 nm or less is required.

In the case of the reticle substrate of the patent document 1 of the prior art, when the length of the short side of the substrate is 850 mm or more, the reflectance of the front and back surfaces of the light-shielding film cannot be set to 10% with respect to the exposure wavelength. Hereinafter, the CD uniformity of the mask pattern in the photomask formed using the photomask substrate is set to be 100 nm or less.

An object of the present invention is to provide a mask substrate which satisfies the following optical characteristics, that is, a mask pattern having high precision can be obtained when a photomask is formed by etching, and display unevenness can be suppressed when a display device is fabricated using a photomask.
[Technical means to solve the problem]

(Composition 1)
A reticle substrate, characterized in that it is used by a user who manufactures a reticle for manufacturing a display device, and has:
a transparent substrate formed of a material substantially transparent to exposed light; and a light shielding film disposed on the transparent substrate and formed of a material substantially opaque to the exposed light; and the light shielding film from the transparent substrate side Providing a first reflection suppressing layer, a light shielding layer, and a second reflection suppressing layer.
When the surface on the light-shielding film side of the both surfaces of the mask base is the front surface and the surface on the transparent substrate side is the back surface, the exposure light is in the range of 365 nm to 436 nm. The front reflectance and the back reflectance are each 10% or less, and the wavelength dependence of the back reflectance in the above wavelength range is 5% or less.

(constituent 2)
The mask base of the first aspect is characterized in that the back surface reflectance is smaller than the front surface reflectance in a range of an exposure wavelength of 365 nm to 436 nm.

(constitution 3)
The mask base according to the first or second aspect, wherein the front surface reflectance and the back surface reflectance of the mask base are set to a vertical axis, and a wavelength is a horizontal axis. In the wavelength band of 300 nm to 500 nm, the reflectance spectra of the front surface and the back surface are respectively downward convex curves, corresponding to the front reflection rate and the minimum value of the back surface reflectance (bottom peak) The wavelength is between 350 nm and 450 nm.

(construction 4)
The mask substrate according to any one of 1 to 3, wherein the wavelength dependence of the back surface reflectance is smaller than a wavelength dependency of the front surface reflectance in a range of an exposure wavelength of 365 nm to 436 nm.

(Constituent 5)
The mask base according to any one of 1 to 4, wherein the front side reflectance is 10% or more in a wavelength range of 530 nm or more.

(constituent 6)
The mask base according to any one of the first to fifth aspect, wherein the first reflection suppressing layer contains a chromium-based material of chromium, oxygen, and nitrogen, and has a chromium content of 25 to 75 atom%, and oxygen a composition having a content of 15 to 45 atom% and a nitrogen content of 10 to 30 atom%.
The light-shielding layer contains a chromium-based material of chromium and nitrogen, and has a composition in which the content of chromium is 70 to 95% by atom and the content of nitrogen is 5 to 30% by atom.
The second reflection suppressing layer is a chromium-based material containing chromium, oxygen, and nitrogen, and has a chromium content of 30 to 75 atom%, an oxygen content of 20 to 50 atom%, and a nitrogen content of 5 to 20 atoms. The composition of %.

(constituent 7)
In the photomask substrate of the sixth aspect, the content of chromium in the first reflection suppressing layer is 50 to 75 atom%, the oxygen content is 15 to 35 atom%, and the nitrogen content is 10 to 25. atom%,
In the second reflection suppressing layer, the content of chromium is 50 to 75 atom%, the content of oxygen is 20 to 40 atom%, and the content of nitrogen is 5 to 20 atom%.

(Composition 8)
In the mask base of the sixth or seventh aspect, the second reflection suppressing layer is configured to have a higher oxygen content than the first reflection suppressing layer.

(constituent 9)
In the mask base of the sixth or seventh aspect, the first reflection suppressing layer is configured to have a nitrogen content higher than that of the second reflection suppressing layer.

(construction 10)
The reticle substrate according to any one of 1 to 9, wherein the transparent substrate is a rectangular substrate, and a short side of the substrate has a length of 850 mm or more and 1620 mm or less.

(Structure 11)
The photomask substrate according to any one of 1 to 10, further comprising: a semi-transmissive film between the transparent substrate and the light shielding film, wherein the semi-transmissive film has an optical density lower than that of the light shielding film Optical concentration.

(construction 12)
The photomask substrate according to any one of 1 to 10, further comprising a phase shift film between the transparent substrate and the light shielding film, wherein the phase shift film shifts a phase of the transmitted light.

(construction 13)
A method of manufacturing a photomask, comprising the steps of:
The photomask substrate according to any one of the above 1 to 10, wherein a resist film is formed on the light shielding film, and the resist pattern formed by the resist film is used as a mask to etch the light shielding film. A light shielding film pattern is formed on the transparent substrate.

(construction 14)
A method of manufacturing a photomask, comprising the steps of:
Preparing the above-mentioned photomask substrate as in composition 11;
Forming a resist film on the light-shielding film, etching the light-shielding film by using a resist pattern formed by the resist film as a mask, and forming a light-shielding film pattern on the transparent substrate; and setting the light-shielding film pattern The mask etches the semi-transmissive film to form a semi-transmissive film pattern on the transparent substrate.

(construction 15)
A method of manufacturing a photomask, comprising the steps of:
Preparing the above-mentioned photomask substrate as in composition 12;
Forming a resist film on the light-shielding film, etching the light-shielding film by using a resist pattern formed by the resist film as a mask, and forming a light-shielding film pattern on the transparent substrate; and setting the light-shielding film pattern The mask etches the phase shift film to form a phase shift film pattern on the transparent substrate.

(construction 16)
A manufacturing method of a display device, characterized by having an exposure step of placing a photomask obtained by the manufacturing method of the photomask of any one of 13 to 15 on a masking station of an exposure apparatus And exposing at least one of the light shielding film pattern, the semi-transmissive film pattern, and the phase shift film pattern formed on the photomask to a resist formed on a substrate of the display device.
[Effects of the Invention]

According to the present invention, it is possible to obtain a photomask substrate which is excellent in pattern accuracy and which can suppress optical characteristics of display unevenness when manufacturing a display device.

The inventors of the present invention have focused on the surface of the mask on the side of the light-shielding film (hereinafter, also referred to as the front surface) and the surface on the transparent substrate side in order to suppress display unevenness in the production of the display device using the conventional mask (hereinafter also referred to as The reflectance spectra of each of the back sides were studied. The reflectance spectra of the front and back sides are such that the reflectances at different wavelengths are different, and the reflectance at a specific wavelength band becomes a very small downward convex curve. The relationship between the reflectance spectrum and the display unevenness was investigated. It was found that the front reflectance and the back reflectance were small in the range of 365 nm to 436 nm, and the wavelength dependence on the back reflectance was small. In the case of the case, display unevenness can be further suppressed.

The wavelength dependence of the reflectance indicates that the reflectance changes depending on the exposure wavelength, and the smaller the wavelength dependence means that the difference between the maximum value and the minimum value of the reflectance is small, that is, the amount of change (variation range) of the reflectance is small. .

Heretofore, when pattern transfer is performed by irradiating the substrate to be transferred with light by using a photomask, it is only considered that the light which is re-reflected by the front surface of the light-shielding film is prevented from being transferred to the substrate to be transferred. The pattern accuracy is deteriorated. Therefore, only the front reflectance is considered, and the back reflectance is not considered.
However, according to the study by the present inventors, it is known that in the projection exposure using the photomask, the reflection from the front surface of the light-shielding film pattern of the photomask is reversed by the reflected light from the substrate on which the photoresist is formed. Compared with the influence of the spot, the reflected light from the back surface of the light-shielding film pattern is reflected to the optical system of the exposure device (transfer device) and the return light incident on the photomask again has a greater influence on the accuracy of the transfer pattern, and is easier. Produce uneven display. The reason for this is that, as the size of the mask is increased, the pattern is made finer, and the pattern is made finer, the reflection from the back surface of the light-shielding film pattern is larger than before, and this problem is recognized for the first time. In particular, in a mask (for example, an ITO (Indium Tin Oxides) pattern, a slit-like pattern) in which the aperture ratio of the light-shielding film pattern used in the production of the display panel is less than 50%, from the mask The influence of the reflected light on the back surface of the light-shielding film pattern becomes large, and display unevenness is likely to occur in the display panel produced using the photomask.

Since the back surface reflectance has a large influence on the display unevenness, the inventors of the present invention have studied the viewpoints of the front reflectance and the back reflectance with respect to the mask substrate. During the research, it was found that not only the reflectance of the front side and the back side, but also the wavelength dependence of the back reflectance also affected the accuracy and display unevenness of the transfer pattern. Further, as a result of further research, the front reflectance and the back reflectance of the light to be exposed are set to 10% or less and the wavelength of the back reflectance is set in the range of 365 nm to 436 nm. The mask base is configured to have a dependency of 5% or less, and the reflective light from the back surface of the light-shielding film pattern can be effectively reduced to the optical system of the exposure device (transfer device) and incident on the light again when the photomask is produced. The return light of the cover can suppress display unevenness as compared with the case where the display device is manufactured using the conventional photomask.

The present invention has been completed based on the above findings.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. In addition, the following embodiment is an embodiment of the present invention, and the present invention is not limited to the scope. In the drawings, the same or corresponding components are denoted by the same reference numerals, and the description is simplified or omitted.

<mask base>
A reticle base according to an embodiment of the present invention will be described. The mask substrate of the present embodiment is formed by, for example, producing a single wavelength of light selected from a wavelength band of 365 nm to 436 nm, or a plurality of wavelengths (for example, I-ray (wavelength 365 nm), H-ray). A user who uses a composite light of (405 nm) and G-ray (wavelength 436 nm) to expose a photomask for display device manufacturing. In the present specification, the numerical range expressed by "~" means a range including the numerical values before and after "~" as the lower limit and the upper limit.

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

(transparent substrate)
The transparent substrate 11 is not particularly limited as long as it is formed of a material that is substantially transparent to light to be exposed and has transparency. A substrate material having a transmittance for an exposure wavelength of 85% or more, preferably 90% or more is used. Examples of the material for 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 appropriately changed depending on the size required for the photomask for manufacturing the display device. For example, as the transparent substrate 11, a transparent substrate 11 having a rectangular shape and a short side length of 330 mm or more and 1620 mm or less can be used. As the transparent substrate 11, for example, a size 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. Substrate, 850 mm × 1400 mm, 1220 mm × 1400 mm, 1620 mm × 1780 mm. In particular, it is 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 a display device of G7 to G10 can be obtained.

(shading film)
The light shielding film 12 is formed by sequentially laminating the first reflection suppressing layer 13 , the light shielding layer 14 , and the second reflection suppressing layer 15 from the transparent substrate 11 side. In the following, the surface on the side of the light shielding film 12 on both surfaces of the mask base 1 will be referred to as a front surface, and the surface on the side of the transparent substrate 11 will be referred to as a back surface.

The first reflection suppressing layer 13 is provided on the surface of the light-shielding layer 14 on the side close to the transparent substrate 11 in the light-shielding film 12, and is disposed adjacent to the exposure device when patterning is performed by the photomask formed using the mask substrate 1. The side of the (exposure source). When the exposure process is performed using a photomask, the exposed light is irradiated from the transparent substrate 11 side (back surface side) of the mask, and the pattern transfer image is transferred onto the substrate for the display device as the transfer target. Resist film. In this case, the reflected light which is reflected by the light on the back side of the light-shielding film pattern is incident on the optical system of the exposure apparatus, and is incident again from the side of the transparent substrate 11 of the mask, thereby becoming a light-shielding film pattern. The stray light of the mask pattern causes deterioration of the transferred image such as the formation of a ghost image or an increase in the amount of the spot, or is caused by exposure of the light of the above-mentioned overlapping portion of the substrate for the display device. Display uneven. When pattern transfer is performed using a photomask, the first reflection suppression layer 13 can suppress reflection of light that is exposed on the back side of the light shielding film 12, so that deterioration of the transfer image can be suppressed and the transfer characteristics can be improved. Further, it is suppressed that display unevenness is caused by exposure of light in the vicinity of the overlapping portion of the substrate for the display device to the above-mentioned exposure light.

The light shielding layer 14 is provided between the first reflection suppression layer 13 and the second reflection suppression layer 15 in the light shielding film 12 . The light shielding layer 14 has a function of being adjusted in such a manner that the light shielding film 12 has an optical density such that the exposed light becomes substantially opaque. Here, the light opaque to the exposure light is a light-shielding property of 3.0 or more in terms of optical density, and from the viewpoint of transfer characteristics, the optical density is preferably 4.0 or more, and more preferably 4.5 or more. .

The second reflection suppressing layer 15 is provided on the surface of the light shielding layer 12 on the side away from the transparent substrate 11 in the light shielding film 12. The second reflection suppressing layer 15 can suppress the light shielding film 12 when a resist film is formed thereon and a specific pattern is drawn by the drawing light (laser light) of the resist film by a drawing device (for example, a laser drawing device). The reflection on the front side makes it possible to increase the CD uniformity of the resist pattern and the mask pattern formed therefrom. Further, when the second reflection suppressing layer 15 is used as a photomask, it is disposed on the substrate side of the display device as the transfer target, and suppresses light reflected by the transfer target from the front side of the light shielding film 12 of the photomask. It is reflected again and returned to the object to be transferred, and the deterioration of the transfer image is suppressed to contribute to the improvement of the transfer characteristics, and it is possible to suppress the display of the light that is exposed to the exposure of the substrate in the vicinity of the overlapping portion of the substrate for the display device. All.

(optical characteristics of the reticle base)
As described above, the mask substrate 1 has an exposure wavelength in the range of 365 nm to 436 nm, and the front reflectance and the back reflectance of the exposed light are each 10% or less, and the wavelength dependence of the back reflectance is 5%. The following optical characteristics. Here, the wavelength dependence of the back surface reflectance refers to the difference between the maximum value and the minimum value of the back surface reflectance in the range of the exposure wavelength of 365 nm to 436 nm. Specifically, the reflectance spectrum of the front surface obtained by irradiating light to the front surface of the mask base 1 is in the range of 365 nm to 436 nm in the exposure wavelength, and the front reflectance is set to 10% or less. The front side reflectance is preferably 7.5% or less, more preferably 5% or less, in the range of the exposure wavelength of 365 nm to 436 nm. Further, similarly, the reflectance spectrum of the back surface obtained by irradiating light to the back surface is in the range of 365 nm to 436 nm in the exposure wavelength, and the back reflectance is set to 10% or less. It is preferable that the back surface reflectance is 7.5% or less in the wavelength range of the exposure wavelength of 365 nm to 436 nm, and more preferably 5% or less. Further, the wavelength dependence of the back surface reflectance is 5% or less in the range of the exposure wavelength of 365 nm to 436 nm. In particular, in order to reduce the display unevenness in the case of producing a display device using a photomask, it is important to set the wavelength dependence of the back surface reflectance to 5% or less in the range of the exposure wavelength of 365 nm to 436 nm. It is preferable that the wavelength dependence of the back surface reflectance is 3% or less in the wavelength range of the exposure wavelength of 365 nm to 436 nm.

The mask base 1 is preferably a region having a reflectance spectrum of the front side and the back surface in the range of 365 nm to 436 nm in the exposure wavelength, and the back reflectance is smaller than the front reflectance.
Moreover, in order to manufacture a plurality of reticle bases capable of suppressing display unevenness, it is stable and high-yield, and the reticle base 1 preferably has a front surface reflectance and a back surface reflectance of the reticle base as a vertical axis. In the reflectance spectrum obtained by setting the wavelength to the horizontal axis, the reflectance spectrum is a downward convex curve in a wavelength band of 300 nm to 500 nm, corresponding to the minimum of the front reflectance and the back reflectance (bottom) The peak wavelength is between 350 nm and 450 nm.
Further, the mask base 1 is preferably in the range of 365 nm to 436 nm in exposure wavelength, and the wavelength dependency of the back surface reflectance is smaller than the wavelength dependence of the front reflectance. Further, from the viewpoint of the detection accuracy in the dimensional measurement of the light-shielding film pattern in the photomask produced by the photomask substrate 1, the photomask substrate 1 is preferably in the wavelength range of 530 nm or more, and the front surface of the light-shielding film The reflectance is 10% or more.

(Material of the light shielding film)
Next, the materials of the respective layers in the light shielding film 12 will be described.
The material of each layer is not particularly limited as long as the optical characteristics are obtained in the mask substrate 1. However, from the viewpoint of obtaining the above optical characteristics, it is preferred to use the following materials for each layer.
The first reflection suppressing layer 13 is preferably made of a chromium-based material containing chromium, oxygen, and nitrogen. The oxygen in the first reflection suppressing layer 13 exerts an effect of lowering the reflectance of the light from the back side. In addition, the nitrogen in the first reflection suppressing layer 13 exhibits a light-shielding film formed by etching (especially wet etching) using a mask base in addition to the effect of lowering the reflectance of the light from the back side. The profile of the pattern is nearly vertical and enhances the effect of CD uniformity. Further, in terms of controlling the etching characteristics, carbon or fluorine may be further contained.
The light shielding layer 14 is preferably made of a chromium-based material containing chromium and nitrogen. The nitrogen in the light shielding layer 14 has an effect of reducing the etching rate difference from the first reflection suppression layer 13 and the second reflection suppression layer 15 and forming the mask base by etching (especially wet etching). The cross section of the light shielding film pattern is nearly vertical, and the etching time of the light shielding film 12 (integral) is shortened to improve CD uniformity. Further, in view of controlling the etching characteristics, oxygen, carbon, and fluorine may be further contained.
The second reflection suppressing layer 15 is preferably made of a chromium-based material containing chromium, oxygen, and nitrogen. The oxygen in the second reflection suppressing layer 15 exerts an effect of lowering the reflectance of the drawing light from the drawing device on the front side or the reflectance of the light from the front side. Moreover, the effect of improving the adhesion to the resist film and suppressing the side etching caused by the penetration of the etchant from the interface between the resist film and the light-shielding film 12 is suppressed. In addition, the nitrogen in the second reflection suppressing layer 15 exhibits an effect of lowering the reflectance of the drawing light from the front side and the reflectance of the light from the front side, and etching the substrate by the mask ( In particular, the pattern of the light-shielding film pattern formed by wet etching is close to vertical and the effect of CD uniformity is improved. Further, in terms of controlling the etching characteristics, carbon or fluorine may be further contained.

(composition of light-shielding film)
Next, the composition of each layer in the light shielding film 12 will be described. Further, the content ratio of each of the following elements is a value measured by X-ray photoelectron spectroscopy (XPS).

The light-shielding film 12 is preferably configured to contain chromium (Cr) at a content ratio of 25 to 75 atom% and oxygen (O) at a content of 15 to 45 atom%, in a case where the first reflection suppression layer 13 is contained. The content ratio of 10 to 30 atom% includes nitrogen (N), and the light shielding layer 14 contains chromium (Cr) at a content ratio of 70 to 95 atom%, and contains nitrogen (N) at a content ratio of 5 to 30 atom%, and the second reflection The suppression layer 15 contains chromium (Cr) at a content of 30 to 75 atom%, oxygen (O) at a content of 20 to 50 atom%, and nitrogen (N) at a content of 5 to 20 atom%. More preferably, the first reflection suppressing layer 13 contains Cr in a content ratio of 50 to 75 atom%, O in a content ratio of 15 to 35 atom%, and N in a content ratio of 5 to 25 atom%, and second reflection suppression. The layer 15 contains Cr at a content of 50 to 75 at%, contains O at a content of 5 to 40 at%, and contains N at a content of 5 to 20 at%.

It is preferable that the first reflection suppressing layer 13 and the second reflection suppressing layer 15 each have a region in which the content ratio of at least one of O and N changes continuously or in a stepwise manner in the film thickness direction.

The second reflection suppressing layer 15 preferably has a region in which the O content is increased toward the side of the light shielding layer 14 in the film thickness direction.

Moreover, it is preferable that the second reflection suppressing layer 15 has a region in which the N content is lowered toward the side of the light shielding layer 14 in the film thickness direction.

In addition, it is preferable that the first reflection suppressing layer 13 has a region in which the O content rate is increased and the N content is lowered in the transparent substrate 11 in the film thickness direction.

Further, in the mask base 1 and the mask produced thereby, the second reflection suppression layer 15 is preferably configured from the viewpoint of further reducing the reflectance of the front surface and the back surface and reducing the difference in reflectance between the mask base 1 and the mask. The O content is higher than that of the first reflection suppression layer 13 , and the first reflection suppression layer 13 is preferably configured such that the N content is higher than that of the second reflection suppression layer 15 . Specifically, it is preferable that the O content of the second reflection suppressing layer 15 is 5 atom% to 10 atom% or more larger than that of the first reflection suppressing layer 13, and it is preferable that the N of the first reflection suppressing layer 13 is contained. The rate is 5 atom% to 10 atom% or more larger than that of the second reflection suppressing layer 15. In the case where the first reflection suppressing layer 13 or the second reflection suppressing layer 15 has a composition gradient region, the O content ratio or the N content ratio indicates the average concentration in the film thickness direction.

Further, in the first reflection suppressing layer 13, the light shielding layer 14, and the second reflection suppressing layer 15, the change in the content ratio of each element may be either continuous or stepwise, but is preferably continuous.

(About the combined state (chemical state))
The light shielding layer 14 preferably contains chromium (Cr) and chromium nitride (Cr ₂ N).
The first reflection suppressing layer 13 and the second reflection suppressing layer 15 preferably contain chromium nitride (CrN), chromium (III) oxide (Cr ₂ O ₃ ), and chromium (VI) oxide (CrO ₃ ).

(about film thickness)
In the light-shielding film 12, the thickness of each of the first reflection suppressing layer 13, the light-shielding layer 14, and the second reflection suppressing layer 15 is not particularly limited, and is preferably adjusted according to the optical density or reflectance required for the light-shielding film 12. The thickness of the first reflection suppressing layer 13 is reflected on the surface of the first reflection suppressing layer 13 by the light from the back side of the light shielding film 12, and the first reflection suppressing layer 13 and the light shielding layer 14 are provided. The light generated by the reflection of the interface can be as thick as the interference effect. On the other hand, the thickness of the second reflection suppressing layer 15 is reflected on the surface of the second reflection suppressing layer 15 and the second reflection suppressing layer 15 as long as the light from the front side of the light shielding film 12 is exerted. The thickness of the interference generated by the reflection of the interface with the light shielding layer 14 may be as large as the thickness. The thickness of the light shielding layer 14 may be a thickness such that the optical density of the light shielding film 12 is three or more. Specifically, in the light-shielding film 12, the reflectance of the front surface and the back surface is set to 10% or less, and the optical density is set to 3.0 or more. For example, the film thickness of the first reflection suppressing layer 13 is preferably set. The film thickness of the light shielding layer 14 is set to 50 nm to 120 nm from 15 nm to 60 nm, and the film thickness of the second reflection suppressing layer 15 is set to 10 nm to 60 nm.

<Method of Manufacturing Photomask Base>
Next, a method of manufacturing the above-described mask substrate 1 will be described.

(preparation step)
A transparent substrate 11 that is substantially transparent to the exposed light is prepared. Further, the transparent substrate 11 should be subjected to any processing steps such as a grinding step and a polishing step as needed to form a flat and smooth main surface. After the polishing, it is preferable to perform washing to remove foreign matter or contamination on the surface of the transparent substrate 11. As the washing, for example, sulfuric acid, sulfuric acid hydrogen peroxide mixture (SPM), ammonia, aqueous ammonia hydrogen peroxide mixture (APM), OH radical (hydroxyl radical) washing water, ozone water, and temperature can be used. Water, etc.

(Step of forming the first reflection suppressing layer)
Then, the first reflection suppressing layer 13 is formed on the transparent substrate 11. This formation is performed by reactive sputtering using a sputtering target containing Cr and a sputtering gas containing a reactive gas containing an oxygen-based gas, a nitrogen-based gas, and a rare gas. At this time, as the film formation conditions, the flow rate of the reactive gas contained in the sputtering gas is selected to be the flow rate in the metal mode.

Here, the metal mode will be described using FIG. 5. 5 is a schematic view for explaining a film formation mode in the case where a thin film is formed by reactive sputtering, and the horizontal axis represents a partial pressure (flow rate) ratio of a reactive gas in a mixed gas of a rare gas and a reactive gas, The vertical axis represents the voltage applied to the target. In the reactive sputtering, when a target gas is discharged while introducing a reactive gas such as an oxygen gas or a nitrogen gas, the state of the discharge plasma changes depending on the flow rate of the reactive gas, and the film formation rate changes. There are three modes depending on the difference in film formation speed. Specifically, as shown in FIG. 5, there is a reaction mode in which the supply amount (ratio) of the reactive gas is greater than a certain threshold value; and the metal mode is such that the supply amount (ratio) of the reactive gas is less than the reaction amount. a mode; and a transition mode in which a supply amount (ratio) of a reactive gas is set between a reaction mode and a metal mode. In the metal mode, by reducing the ratio of the reactive gas, the adhesion of the reactive gas to the target surface can be reduced, and the film formation speed can be increased. Further, in the metal mode, since the amount of supply of the reactive gas is small, for example, a film having a lower concentration of at least one of the O concentration and the N concentration than the film having the stoichiometric composition can be formed. That is, a film having a relatively high content of Cr and a low O content or N content can be formed.

As a condition for forming the metal mode of the first reflection suppressing layer 13, for example, the flow rate of the oxygen-based gas is preferably 5 to 45 sccm, and the flow rate of the nitrogen-based gas is 30 to 60 sccm, and the flow rate of the rare gas is used. Set to 60 to 150 sccm. Further, it is preferable to set the target application power to 2.0 to 6.0 kW and the target application voltage to 360 to 460 V.

The sputtering target may be any one containing Cr. For example, in addition to the chromium metal, a chromium-based material such as chromium oxide, chromium nitride or chromium oxynitride may 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. Among them, oxygen (O ₂ ) is preferably used in terms of a higher oxidizing power. Further, as the nitrogen-based gas, nitrogen (N ₂ ) or the like can be used. As the rare gas, for example, helium, neon, argon, helium, and xenon may be used. Further, in addition to the above reactive gas, a hydrocarbon-based gas may be supplied, and for example, methane gas or butane gas may be used.

In the present embodiment, the flow rate of the reactive gas and the power applied to the sputtering target are set to a metal mode, and a sputtering target containing Cr is used to form a film by reactive sputtering. On the transparent substrate 11, a first reflection suppressing layer 13 containing Cr at a content of 25 to 75 at%, O at a content of 15 to 45 at%, and N at a content of 10 to 30 at% is formed.

In the case where the first reflection suppressing layer 13 is formed as a single film having a uniform thickness in the film thickness direction, the film formation may be performed without changing the type and flow rate of the reactive gas, but in the film thickness direction. When the composition of the upper O content or the N content has a composition gradient, it is preferable to appropriately change the type or flow rate of the reactive gas and the ratio of the oxygen-based gas or the nitrogen-based gas in the reactive gas. Further, the arrangement of the gas supply ports, the gas supply method, and the like may be changed.

(Step of forming the light shielding layer)
Then, the light shielding layer 14 is formed on the first reflection suppressing layer 13. This formation is performed by reactive sputtering using a sputtering target containing Cr and a sputtering gas containing a nitrogen-based gas and a rare gas. At this time, as the film formation conditions, the flow rate of the reactive gas contained in the sputtering gas is selected to be the flow rate in the metal mode.
The target may be any one containing Cr. For example, in addition to the chromium metal, a chromium-based material such as chromium oxide, chromium nitride or chromium oxynitride may be used. As the nitrogen-based gas, nitrogen (N ₂ ) or the like can be used. As the rare gas, for example, helium, neon, argon, helium, and xenon may be used. Further, in addition to the above reactive gas, the oxygen-based gas or the hydrocarbon-based gas described above may be supplied.
In the present embodiment, the flow rate of the reactive gas and the power applied to the sputtering target are set to be in a metal mode, and reactive sputtering is performed using a sputtering target containing Cr to suppress the first reflection. On the layer 13, a light-shielding layer 14 containing Cr at a content of 70 to 95% by atom and containing N at a content of 5 to 30 atom% is formed.

In addition, as a film formation condition of the light shielding layer 14, for example, the flow rate of the nitrogen-based gas is preferably 1 to 60 sccm, and the flow rate of the rare gas is 60 to 200 sccm. Further, it is preferable to set the target application power to 3.0 to 7.0 kW and the target application voltage to 370 to 380 V.

(Step of forming the second reflection suppressing layer)
Then, the second reflection suppressing layer 15 is formed on the light shielding layer 14. In the same manner as the first reflection suppressing layer 13, the flow rate of the reactive gas and the target applied electric power are set to a metal mode, and the sputtering target containing Cr is used for reactive sputtering. membrane. By this, a second reflection suppressing layer containing Cr in a content ratio of 30 to 75 atomic %, O in a content of 20 to 50 atom%, and N in a content ratio of 5 to 20 atomic % is formed on the light shielding layer 14 . 15.

As a condition for forming the metal mode of the second reflection suppressing layer 15, for example, the flow rate of the oxygen-based gas is preferably 8 to 45 sccm, and the flow rate of the nitrogen-based gas is 30 to 60 sccm, and the flow rate of the rare gas is used. Set to 60 to 150 sccm. Further, it is preferable to set the target application power to 2.0 to 8.0 kW and the target application voltage to 420 to 460 V.

In the case where the second reflection suppressing layer has a composition gradient, as described above, it is preferable to appropriately change the type or flow rate of the reactive gas, the ratio of the oxygen-based gas or the nitrogen-based gas in the reactive gas, and the like.

From the above, the mask base 1 of the present embodiment was obtained.

Further, the film formation of each layer in the light-shielding film 12 is preferably carried out in-situ using an inline type sputtering apparatus. In the case of an in-line type, after the film formation of each layer, the transparent substrate 11 must be extracted outside the apparatus, and the transparent substrate 11 is exposed to the atmosphere, and the layers are oxidized or surface-carbonized. As a result, there is a case where the reflectance or etching rate of the light-shielding film 12 with respect to the exposed light is changed. In this respect, in the case of the in-line type, it is possible to continuously form the respective layers without exposing the transparent substrate 11 to the outside of the apparatus and exposing it to the atmosphere, so that it is possible to suppress the extraction of the unintended elements of the light-shielding film 12.

In the case where the light-shielding film 12 is formed by using the in-line type sputtering apparatus, the composition of the first reflection suppression layer 13, the light-shielding layer 14, and the second reflection suppression layer 15 has a composition gradient region which forms a continuous gradient. Since the (transition layer) is used, the cross-section of the light-shielding film pattern formed by etching (especially wet etching) using the mask base can be made smooth and close to vertical, which is preferable.

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

(Step of forming a resist film)
First, a resist is applied onto the second reflection suppressing layer 15 of the light shielding film 12 of the mask substrate 1, and dried to form a resist film. As the resist, it is necessary to select an appropriate one depending on the drawing device to be used, and a positive or negative resist can be used.

(Step of forming a resist pattern)
Then, a specific pattern is drawn on the resist film using a drawing device. Generally, a laser drawing device is used in the production of a photomask for manufacturing a display device. After the drawing, the resist film is developed and rinsed, thereby forming a specific resist pattern.

In the present embodiment, since the reflectance of the second reflection suppressing layer 15 is lowered, the reflection of the drawing light (laser light) can be reduced when the resist pattern is drawn. Thereby, a resist pattern having a high pattern accuracy can be formed, and accordingly, a mask pattern having a high dimensional accuracy can be formed.

(Step of forming a mask pattern)
Then, the light shielding film 12 is etched by using a resist pattern as a mask to form a mask pattern. The etching may be a wet etching or a dry etching. Usually, if it is a photomask for manufacturing a display device, wet etching is performed, and as an etching liquid (etching agent) used for wet etching, for example, a chromium etching liquid containing cerium ammonium nitrate and perchloric acid can be used.

In the present embodiment, the composition of each layer is adjusted such that the etching rates of the first reflection suppressing layer 13, the light shielding layer 14, and the second reflection suppressing layer 15 are aligned in the thickness direction of the light shielding film 12, so that the wetness can be performed. The cross-sectional shape at the time of etching, that is, the cross-sectional shape of the light-shielding film pattern (mask pattern) is nearly perpendicular to the transparent substrate 11, and high CD uniformity can be obtained.

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

According to the above, the photomask of the embodiment can be obtained.

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

(preparation step)
First, with respect to the substrate on which the resist film is formed on the substrate of the display device, the photomask obtained by the above-described method of manufacturing the photomask is separated by the projection optical system of the exposure device (by projection The exposure mode is placed on the reticle stage of the exposure apparatus in a direction opposite to the resist film formed on the substrate.

(exposure step (pattern transfer step))
Next, a resist exposure step of irradiating the exposed light to the photomask and transferring the pattern to the resist film formed on the substrate of the display device is performed.
The light to be exposed is, for example, a single wavelength light (I-ray (wavelength 365 nm), H-ray (wavelength 405 nm), G-ray (wavelength 436 nm), etc.) selected from a wavelength band of 365 nm to 436 nm. Or a composite light containing a plurality of wavelengths of light (for example, I-ray (wavelength 365 nm), H-ray (405 nm), G-ray (wavelength 436 nm). In the case of using a large photomask, it is preferable to use composite light from the viewpoint of the amount of light as the light for exposure.
In the present embodiment, a photomask manufacturing display device (display panel) having reduced reflectance of the front and back surfaces of the light-shielding film pattern (mask pattern) and having reduced reflectance dependence of the back surface reflectance can be obtained. There is no display device (display panel) with uneven display.

<Effects of the embodiment>
According to this embodiment, one or a plurality of effects shown below are exhibited.

(a) In the mask base 1 of the present embodiment, the first reflection suppressing layer 13, the light shielding layer 14, and the second reflection suppressing layer 15 are laminated to form the light shielding film 12, and have an exposure wavelength in the range of 365 nm to 436 nm. The reflectance of the front and back surfaces is 10% or less, and the wavelength dependence of the back surface reflectance in the above wavelength range is 5% or less. According to the mask base 1, when the light is irradiated and exposed by the mask, the reflection of the front and back light can be suppressed over the entire wavelength band of the exposure wavelength of 365 nm to 436 nm, so that the front and back sides can be reduced. The total amount of light reflected. In particular, since the wavelength dependence of the back surface reflectance can be made 5% or less, the back surface reflectance is made to be low over the entire range of the wavelength range, so that it is possible to suppress the back surface of the mask which has a large influence on display unevenness. Return light. As a result, it is possible to suppress display unevenness due to reflection of light on the front and back surfaces of the reticle when the display device is manufactured using the photomask.

(b) The mask substrate 1 is preferably in the entire range of the exposure wavelength of 365 nm to 436 nm, and the back surface reflectance is smaller than the front reflectance. Thereby, the reflection of light can be suppressed over a wide wavelength band, and the total amount of light reflected can be further reduced.

(c) The mask substrate 1 is preferably a reflection spectrum obtained by setting the front reflectance and the back reflectance of the mask base 1 to the vertical axis and the wavelength to the horizontal axis, and the wavelength is 300 nm to 500 nm. In the wavelength band, the reflectance spectrum is a downward convex curve, and the wavelength corresponding to the minimum of the front reflectance and the back reflectance (bottom peak) is located at 350 nm to 450 nm. Thereby, it is possible to manufacture a plurality of sheets stably and at a high yield to suppress the unevenness of the display.

(d) The mask substrate 1 is preferably in the range of 365 nm to 436 nm in exposure wavelength, and the wavelength dependence of the back surface reflectance is smaller than the wavelength dependence of the front reflectance. That is, it is preferable that the amount of change in the back reflectance is smaller than the amount of change in the front reflectance in the above wavelength range. Thereby, the return light of the back surface of the photomask can be further suppressed, and display unevenness can be further reduced.

(e) The mask substrate 1 is preferably in a wavelength range of 530 nm or more, and the front surface reflectance is 10% or more. Thereby, the detection accuracy in the dimensional measurement of the light-shielding film pattern in the photomask manufactured using the mask base 1 can be improved.

(f) The mask base 1 is preferably configured to contain a chromium-based material of chromium, oxygen, and nitrogen, and has a Cr content of 25 to 75 atom% and an O content. The composition is 15 to 45 atom%, and the N content is 10 to 30 atom%. The light shielding layer 14 is a chromium-based material containing chromium and nitrogen, and has a Cr content of 70 to 95 atom% and an N content of 5 ～30 atom% of the composition, the second reflection suppressing layer 15 is a chromium-based material containing chromium, oxygen, and nitrogen, and has a Cr content of 30 to 75 atom%, an O content of 20 to 50 atom%, and a N content ratio. It is composed of 5 to 20 atom%. By setting each layer as the above-described composition, the reflectance of the front surface and the back surface of the mask base 1 can be reduced, and it is easy to set each of them to 10% or less.

(g) In the present embodiment, each layer of the first reflection suppressing layer 13, the light shielding layer 14, and the second reflection suppressing layer 15 constituting the light shielding film 12 can be reduced in the composition range shown in (d). The concentration of O which reduces the etching rate or the N which increases the etching rate suppresses the difference in etching rates of the respective layers to be uniform. Thereby, the cross-sectional shape when the light-shielding film 12 of the mask base 1 is etched, that is, the cross-sectional shape of the mask pattern can be made nearly perpendicular to the transparent substrate 11. Specifically, in the cross-sectional shape of the mask pattern, when the angle formed by the side surface formed by etching and the transparent substrate 11 is θ, θ can be set within a range of 90°±30°. In addition, the cross-sectional shape can be made nearly vertical, and the etching residue of the first reflection suppressing layer 13 or the etching of the first reflection suppressing layer 13 and the second reflection suppressing layer 15 (so-called undercut) can be suppressed. As a result, the CD uniformity in the mask pattern (light-shielding film pattern) can be improved, and a highly precise mask pattern of 100 nm or less can be formed.

(h) In the present embodiment, the light-shielding film 12 can be made free of etching time by matching the etching rates of the respective layers of the first reflection suppressing layer 13, the light-shielding layer 14, and the second reflection suppressing layer 15 constituting the light-shielding film 12. The length of the cross-sectional shape is stabilized by the length of the etching liquid or the temperature of the etching liquid and the temperature of the etching liquid. For example, when the appropriate etching time of the light-shielding film 12 is T, even if the etching time is 1.5×T and the over-etching is performed, the etching time can be obtained as T. Equal verticality. Specifically, the difference between the angle θ1 formed by the cross section of the light-shielding film pattern when the etching time is T and the angle θ2 formed by the cross-section when the etching time is 1.5×T can be made. 10° or less. In the same manner, when the concentration of the etching liquid is increased and the concentration of the etching liquid is lowered, the difference in the angle formed by the cross section of the light shielding film pattern can be made 10 or less. Further, similarly, when the temperature of the etching liquid is increased (for example, 42 ° C) and when the temperature of the etching liquid is lowered (for example, room temperature, that is, 23 ° C), the etching temperature is higher as the etching liquid is etched. The higher the rate, the difference in the angle formed by the cross section of the light-shielding film pattern can be set to 10 or less. In addition, the appropriate etching time represents an etching time in which the light shielding film 12 is etched in the film thickness direction until the surface of the transparent substrate 11 starts to be exposed.

(i) In the light shielding film 12, it is preferable that the first reflection suppression layer 13 and the second reflection suppression layer 15 contain a chromium-based material of chromium, oxygen, and nitrogen, and the first reflection suppression layer 13 is 50 to 75 atom%. The content includes Cr, contains O at a content of 15 to 35 atom%, and contains N at a content of 10 to 25 atom%, and the second reflection suppression layer 15 contains Cr at a content of 50 to 75 atom%, and 20 to The content of 40 atom% includes O, and N is contained at a content ratio of 5 to 20 atom%.

In the first reflection suppressing layer 13 and the second reflection suppressing layer 15, by further reducing the O content, it is possible to suppress an excessive decrease in the etching rate due to the inclusion of O in the layers. Therefore, in order to match the etching rates of the respective layers of the first reflection suppressing layer 13, the light shielding layer 14, and the second reflection suppressing layer 15 constituting the light shielding film 12, the content ratio of the carbon (C) to be blended in the light shielding layer 14 can be reduced. Alternatively, the light shielding layer 14 does not contain C and is made to contain no carbon. As a result, the content ratio of Cr in the light shielding layer 14 can be increased, and the optical density (OD) can be maintained high.

On the other hand, in the first reflection suppressing layer 13 and the second reflection suppressing layer 15, by further reducing the N content, it is possible to suppress an excessive increase in the etching rate due to the inclusion of N in the layers. Therefore, in order to match the etching rates of the respective layers of the first reflection suppressing layer 13, the light shielding layer 14, and the second reflection suppressing layer 15 constituting the light shielding film 12, the content ratio of N contained in the light shielding layer 14 can be reduced. As a result, the content ratio of Cr in the light shielding layer 14 can be increased, and the optical density (OD) can be maintained high.

(j) The second reflection suppressing layer 15 is preferably configured such that the O content is higher than that of the first reflection suppressing layer 13. Specifically, the O content of the second reflection suppressing layer 15 is preferably 5 atom% to 10 atom% or more larger than that of the first reflection suppressing layer 13. Further, the first reflection suppressing layer 13 is preferably configured to have a higher N content than the second reflection suppressing layer 15. Specifically, it is preferable that the N content of the first reflection suppressing layer 13 is 5 atom% to 10 atom% or more larger than that of the second reflection suppressing layer 15. According to the study by the inventors of the present invention, it is known that when the first reflection suppressing layer 13 and the second reflection suppressing layer 15 are formed of the same material, the reflectance of the front side becomes higher than that of the back surface, although the composition is the same. Side tendency. Therefore, the composition ratio (O content ratio, N content ratio) of each layer of the first reflection suppression layer 13 and the second reflection suppression layer 15 was further studied, and it was found that the first reflection suppression layer 13 and the second reflection were obtained. As described above, the composition ratio (O content and N content) of the suppression layer 15 can be such that the reflectance on the back side is equal to or lower than the front side. By changing the composition ratio (O content rate, N content rate) of each layer in this manner, the reflectances of the front side and the back side can be controlled.

(k) The first reflection suppressing layer 13 and the second reflection suppressing layer 15 preferably have regions in which the content ratio of at least one of O and N changes continuously or in a stepwise manner in the film thickness direction. By changing the composition of each layer of the first reflection suppressing layer 13 and the second reflection suppressing layer 15 , it is possible to locally introduce O or N into a region having a high content ratio in each layer, and to maintain the layers in a low level. The average content of O or N. Thereby, the reflectance of the front side and the back side of the mask base 1 can be maintained low.

In the respective layers of the first reflection suppressing layer 13, the light shielding layer 14, and the second reflection suppressing layer 15 constituting the light shielding film 12, when the O content rate is high, the etching rate is excessively lowered, and when the N content rate is high, the etching rate is increased. Excessively increasing, by lowering the content ratio of O or N, it is possible to suppress the difference in etching rate of each layer due to the inclusion of the elements. In other words, it is possible to suppress the deviation of the etching rate between the first reflection suppressing layer 13 and the second reflection suppressing layer 15 and the light shielding layer 14. As a result, in order to match the etching rates of the respective layers of the first reflection suppressing layer 13, the light shielding layer 14, and the second reflection suppressing layer 15 constituting the light shielding film 12, it is possible to reduce N or carbon contained in the light shielding layer 14 or to shield the light. The layer 14 does not contain carbon and is made free of carbon. As a result, the content ratio of Cr in the light shielding layer 14 can be increased, and the optical density (OD) can be maintained high.

(1) The second reflection suppressing layer 15 preferably has a region in which the O content is increased toward the side of the light shielding layer 14 in the film thickness direction. As a result, in the second reflection suppressing layer 15, the O content of the interface portion with the light shielding layer 14 is locally increased, and the average O content in the film thickness direction is lowered. As a result, a desired reflectance can be obtained on the front side (second reflection suppressing layer 15) of the light shielding film 12, and erosion due to excessive etching at the interface can be suppressed.

(m) The second reflection suppressing layer 15 preferably has a region in which the N content is lowered toward the side of the light shielding layer 14 in the film thickness direction. In this way, in the second reflection suppressing layer 15, while maintaining the average N content in the film thickness direction to some extent, the N content ratio of the interface portion with the light shielding layer 14 is locally lowered. As a result, it is possible to suppress the erosion due to excessive etching at the interface between the second reflection suppressing layer 15 and the light shielding layer 14.

(n) The first reflection suppressing layer 13 is preferably a region having a transparent substrate 11 facing the film thickness direction and having an O content ratio and a decrease in the N content. In the first reflection suppressing layer 13, the O content ratio is increased and the N content is lowered by the transparent substrate 11 in the film thickness direction, whereby the etching rate can be gradually lowered toward the transparent substrate 11. Thereby, the erosion at the interface between the first reflection suppressing layer 13 and the transparent substrate 11 can be suppressed, and the CD uniformity of the mask pattern can be further improved.

(o) Further, according to the present embodiment, the light shielding layer 14 is preferably a chromium-based material containing a bonding state (chemical state) of chromium (Cr) and chromium nitride (Cr ₂ N). By setting the light-shielding layer 14 to a chromium-based material containing a bonding state (chemical state) of Cr and Cr ₂ N, it is possible to suppress an excessive etching rate when a specific amount of N is contained in the light shielding layer 14, and it is possible to prevent light shielding. The cross-sectional shape of the film pattern is nearly vertical.

(p) Further, according to the present embodiment, the first reflection suppressing layer 13 and the second reflection suppressing layer 15 preferably contain chromium nitride (CrN), chromium (III) oxide (Cr ₂ O ₃ ), and chromium oxide. (VI) A chromium-based material in a bonded state (chemical state) of (CrO ₃ ). When the first reflection suppressing layer 13 and the second reflection suppressing layer 15 contain a plurality of chromium oxides of Cr ₂ O ₃ and CrO ₃ , the reflectances of the front and back surfaces of the light shielding film 12 can be effectively reduced. Further, since the first reflection suppressing layer 13 and the second reflection suppressing layer 15 contain chromium nitride of CrN, it is possible to suppress an excessive decrease in the etching rate due to the chromium oxide, so that the cross-sectional shape of the light-shielding film pattern can be made nearly vertical. .

(q) Further, according to the present embodiment, it is preferable that the first reflection suppressing layer 13 and the second reflection suppressing layer 15 use a sputtering target containing Cr and an oxygen-based gas, a nitrogen-based gas, and a rare gas. The film is formed by reactive sputtering of a sputtering gas, and the light shielding layer 14 is formed by reactive sputtering using a sputtering target containing Cr and a sputtering gas containing a nitrogen-based gas and a rare gas. The film formation conditions of the reactive sputtering, and the flow rate of the reactive gas contained in the sputtering gas are selected to be the flow rate in the metal mode. By this, it is easy to adjust the respective layers of the first reflection suppressing layer 13, the light shielding layer 14, and the second reflection suppressing layer 15 constituting the light shielding film 12 to the above-described composition range, and it is possible to effectively reduce the front and back surfaces of the light shielding film 12. The reflectance is such that the cross-sectional shape of the light-shielding film pattern when the light-shielding film 12 is patterned is nearly vertical.

(r) When each layer of the first reflection suppressing layer 13 and the second reflection suppressing layer 15 is formed by reactive sputtering, oxygen (O ₂ gas) is preferably used as the oxygen-based gas. Since the O ₂ gas has a higher oxidizing power than other oxygen-based gases, even when the film formation is performed in the selective metal mode, the layers can be more reliably adjusted to the above composition range. Thereby, the cross-sectional shape of the light-shielding film pattern when the light-shielding film 12 is patterned can be made close to vertical while the reflectance of the front surface and the back surface of the light-shielding film 12 can be effectively reduced.

(s) According to the mask base 1 of the present embodiment, since the reflectance on the front side is low, when a resist film is provided on the light-shielding film 12, and a resist pattern is formed by a drawing and development step, drawing can be reduced. Light is reflected from the front side of the light shielding 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 formed thereby can be improved.

(t) In the mask produced by the mask base 1 of the present embodiment, since the light shielding film pattern is highly accurate, and the reflectance of the front surface and the back surface of the light shielding film pattern is lowered, when the pattern is transferred to the transfer target, A higher transfer characteristic can be obtained.

(u) In the present embodiment, even if a substrate having a rectangular shape and a short side length of 850 mm or more and 1620 mm or less is used as the transparent substrate 11, the mask base 1 is enlarged. Since the film 12 has the same etching rate in the film thickness direction, the CD uniformity of the mask pattern obtained by etching the light shielding film 12 can be maintained high.

<Other Embodiments>
The embodiment of the present invention has been specifically described above, but the present invention is not limited to the embodiment described above, and may be appropriately modified without departing from the scope of the invention.

In the above 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 thereto. For example, a photomask substrate having a semi-transmissive film having an optical density lower than that of the light shielding film 12 may be disposed between the transparent substrate 11 and the light shielding film 12. The mask substrate on which the semi-transmissive film and the light-shielding film 12 are formed on the transparent substrate 11 is also preferably in the range of 365 nm to 436 nm, and the back surface of the semi-transparent film for the exposed light. The reflectance is 10% or less, the front surface reflectance of the light-shielding film is 10% or less, and the wavelength dependence of the back surface reflectance of the semi-transmissive film in the above wavelength range is 5% or less. The reticle substrate can be used as a reticle substrate having a gray scale mask or a gradation mask which is reduced in the number of reticle to be used in manufacturing the display device. The reticle pattern in the gray scale mask or the grading mask becomes a semi-transmissive film pattern and/or a light shielding film pattern.
Further, a photomask substrate in which a phase shifting film that shifts the phase of transmitted light is provided between the transparent substrate 11 and the light shielding film 12 instead of the semitransparent film may be provided. The photomask substrate having the phase shift film and the light shielding film 12 formed on the transparent substrate 11 is preferably in the range of 365 nm to 436 nm, and the phase shift film for the exposed light is The back surface reflectance is 10% or less, the front surface reflectance of the light-shielding film is 10% or less, and the wavelength dependence of the back surface reflectance of the semi-transmissive film in the above wavelength range is 5% or less. The reticle substrate can be used as a phase shift mask having the effect of high pattern resolution produced by the phase shift effect. The mask pattern in the phase shift mask is a phase shift film pattern, or a phase shift film pattern and a light shielding film pattern.
The semi-transmissive film and the phase-shift film are preferably materials having an etching selectivity to a chromium-based material which is a material constituting the light-shielding film 12. As such a material, a metal telluride-based material containing molybdenum (Mo), zirconium (Zr), titanium (Ti), tantalum (Ta), and bismuth (Si) can be used, and further, it is suitable to contain oxygen, nitrogen, carbon, or fluorine. At least one of the materials. For example, it is applicable to metal telluride such as MoSi, ZrSi, TiSi, TaSi, oxide of metal telluride, nitride of metal telluride, nitrogen oxide of metal telluride, carbonitride of metal telluride, carbon of metal telluride A carbon oxynitride of an oxide or a metal halide. Further, the semi-transmissive film or the phase-shift film may be a laminated film including the above-described film as a functional film.

Further, in the above-described embodiment, the case where the first reflection suppression layer 13 and the second reflection suppression layer 15 are each provided in one layer has been described, but the present invention is not limited thereto. For example, each layer may be a plurality of layers of two or more layers.

Further, in the above embodiment, an etching mask film including a material having an etching selectivity with the light shielding film 12 may be formed on the light shielding film 12.

Further, in the above embodiment, an etching stopper film including a material having an etching selectivity with the light shielding film may be formed between the transparent substrate 11 and the light shielding film 12. The etching mask film and the etching stopper film include a material having an etching selectivity with respect to a chromium-based material which is a material constituting the light shielding film 12. Examples of such a material include a metal telluride-based material containing molybdenum (Mo), zirconium (Zr), titanium (Ti), tantalum (Ta), and cerium (Si), or Si, SiO, SiO ₂ , or SiON. A lanthanide material such as Si ₃ N ₄ .
[Examples]

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

<Example 1>
In the present embodiment, the first reflection suppressing layer and the light shielding are laminated on the transparent substrate having a substrate size of 1220 mm × 1400 mm as shown in FIG. 1 by using the in-line sputtering apparatus in the order shown in the above embodiment. A mask base having a light shielding film is produced by the layer and the second reflection suppressing layer.

The film formation condition of the first reflection suppressing layer is that the sputtering target is a Cr sputtering target, and the flow rate of the reactive gas is selected to be in a metal mode, and the flow rate of oxygen (O ₂ ) is selected from the range of 5 to 45 sccm. The flow rate of nitrogen (N ₂ ) is selected from the range of 30 to 60 sccm, the flow rate of argon gas (Ar) is selected from the range of 60 to 150 sccm, and the target application power is set to 2.0 to 6.0 kW, and the applied voltage of the target is set. It is in the range of 420 to 430 V. In addition, the substrate conveyance speed at the time of film formation of the first reflection suppression layer was 350 mm/min.

The film formation condition of the light shielding layer is such that the sputtering target is a Cr sputtering target, and the flow rate of the reactive gas is a metal mode, and the flow rate of nitrogen (N ₂ ) is selected from the range of 1 to 60 sccm, from 60 to The flow rate of argon gas (Ar) was selected in the range of 200 sccm, and the target application power was set to 3.0 to 7.0 kW, and the applied voltage was set to the range of 370 to 380 V. Further, the substrate transport speed at the time of film formation of the light shielding layer was set to 200 mm/min.

The film formation condition of the second reflection suppressing layer is that the sputtering target is a Cr sputtering target, and the flow rate of the reactive gas is selected to be in a metal mode, and the flow rate of oxygen (O ₂ ) is selected from the range of 8 to 45 sccm. The flow rate of nitrogen (N ₂ ) is selected from the range of 30 to 60 sccm, the flow rate of argon gas (Ar) is selected from the range of 60 to 150 sccm, and the target application power is set to 2.0 to 6.0 kW, and the target application voltage is set to 420 ~ 430 V range. In addition, the substrate conveyance speed at the time of film formation of the second reflection suppression layer was set to 300 mm/min.

The composition of the film thickness direction of the obtained light-shielding film of the reticle base 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 is a view showing the results of composition analysis of the film thickness direction in the mask base of Example 1. The horizontal axis represents the sputtering time, and the vertical axis represents the content of the element [atomic %]. The sputtering time indicates the depth from the front side of the light shielding film.

In Fig. 2, the area from the front to the depth of about 5 min is the front natural oxide layer, and the area from the depth of about 5 min to the depth of about 16 min is the second reflection suppression layer, from about 16 min in depth to about 40 min in depth. The area to the end is a transition layer. The area from about 40 min to a depth of about 97 min is a light-shielding layer. The area from about 97 min to a depth of about 124 min is a transition layer, from about 124 min to a depth of about 132. The region up to min is the first reflection suppressing layer, and the region from the depth of about 132 min is a transparent substrate.
Further, the film thickness of the light-shielding film measured by the film thickness meter is 198 nm, and the film thicknesses of the front surface natural oxide layer, the second reflection suppression layer, the transition layer, the light shielding layer, the transition layer, and the first reflection suppression layer are The front natural oxide layer is about 4 nm, the second reflection suppression layer is about 21 nm, the transition layer is about 35 nm, the light shielding layer is about 88 nm, the transition layer is about 39 nm, and the first reflection suppression layer is about 11 nm. .

As shown in FIG. 2, the first reflection suppressing layer-based CrON film contains 55.4 atom% of Cr, 20.8 atom% of N, and 23.8 atom% of O. The content ratio of these elements is measured in the portion of the first reflection suppressing layer where N becomes a peak (the region where the sputtering time is 123 min). The first reflection suppressing layer has a gradient composition as shown in FIG. 2, and has a transparent substrate facing the film thickness direction, and the O content is increased and the N content is lowered. Further, in the first reflection suppressing layer, the average content ratio of each element in the film thickness direction is 57 atom%, N is 18 atom%, and O is 25 atom%.

The light shielding layer is a CrN film and contains 92.0 atom% of Cr and 8.0 atom% of N. The content of these elements was measured in the center portion of the light-shielding layer in the film thickness direction (the region where the sputtering time was 69 min). Further, in the light shielding layer, the average content ratio of each element in the film thickness direction was 91 atom%, and N was 9 atom%.

The second reflection suppressing layer-based CrON film contains 50.7 atom% of Cr, 12.2 atom% of N, and 37.1 atom% of O. The content ratio of these elements is measured in the central portion of the second reflection suppressing layer in the region where O is increased (the region where the sputtering time is 16 min). The second reflection suppressing layer has a gradient composition as shown in FIG. 2, and has a portion in which the O content rate increases toward the film thickness direction and the N content rate decreases. Further, in the second reflection suppressing layer, the average content ratio of each element in the film thickness direction is 52 atom%, N is 17 atom%, and O is 31 atom%. Further, on the front surface of the second reflection suppressing layer, a front natural oxide layer is formed by exposure to the atmosphere, and it is considered that a high O content and a C content are detected by oxidation or carbonization of the layer.

In addition, the state of bonding (chemical state) of each layer of the first reflection suppressing layer, the light shielding layer, and the second reflection suppressing layer constituting the light shielding film is subjected to spectral analysis based on the XPS measurement result. As a result, the first reflection suppressing layer and the second reflection suppressing layer include chromium nitride (CrN), chromium (III) oxide (Cr ₂ O ₃ ), and chromium (VI) oxide (CrO ₃ ), and contain chromium, oxygen, and Nitrogen chromium material (chromium compound). Further, the light shielding layer contains chromium (Cr) and chromium nitride (Cr ₂ N), and is a chromium-based material (chromium compound) containing chromium and nitrogen.

(evaluation of the reticle base)
With respect to the mask substrate of Example 1, the optical density of the light-shielding film and the reflectance of the front surface and the back surface of the light-shielding film were evaluated by the method shown below.

For the reticle substrate of Example 1, the optical density of the light-shielding film was measured by a spectrophotometer ("SolidSpec-3700" manufactured by Shimadzu Corporation), and the result was G-ray (wavelength) in the wavelength band of the light to be exposed. 5.0 at 436 nm). In addition, the reflectance of the front surface and the back surface of the light-shielding film was measured by a spectrophotometer ("SolidSpec-3700" manufactured by Shimadzu Corporation). Specifically, the reflectance (front reflectance) of the second reflection suppressing layer side of the light-shielding film and the reflectance (back surface reflectance) of the light-shielding film on the transparent substrate side were measured by a spectrophotometer. As a result, a reflectance spectrum as shown in Fig. 3 was obtained. 3 shows the reflectance spectra of the front and back surfaces of the mask base 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 mask base of the first embodiment can set the peak wavelength of the reflectance spectrum of the front surface and the back surface to be around 436 nm, and it is possible to greatly reduce the reflectance for light of a wide wavelength. Specifically, at a wavelength of 365 nm to 436 nm, the front surface reflectance of the light-shielding film is 10.0% or less (7.7% (wavelength 365 nm), 1.8% (wavelength 405 nm), 1.1% (wavelength 413 nm), 0.3%. (wavelength 436 nm)), the back surface reflectance of the light-shielding film was 7.5% or less (6.2% (wavelength 365 nm), 4.7% (wavelength 405 nm), 4.8% (wavelength 436 nm)). It has been confirmed that the reflectance of the front surface and the back surface of the light-shielding film can be reduced to 10% or less at a wavelength of 365 nm to 436 nm, and in particular, the front reflectance can be set to 0.3% with respect to the reflectance of light having a wavelength of 436 nm. The back reflectance was set to 4.8%.
Further, the dependence of the front reflectance of the light-shielding film in the range of the exposure wavelength of 365 nm to 436 nm was 7.4%, and the dependence of the back surface reflectance was 1.6%.
Further, the front reflectance of the light-shielding film at a wavelength of 530 nm was 11.8%.
In the wavelength band of 300 nm to 500 nm, the wavelength (bottom peak wavelength) corresponding to the minimum (bottom peak) of the front reflectance and the back reflectance is 436 nm, and the back reflectance is 415.5 nm.

(Evaluation of shading film pattern)
Using the photomask substrate of Example 1, a light shielding film pattern was formed on the transparent substrate. Specifically, after forming a phenolic positive resist film on a light-shielding film on a transparent substrate, laser patterning (wavelength 413 nm) and development processing are performed to form a resist pattern. Thereafter, the resist pattern is used as a mask for wet etching using a chromium etching solution, and a light shielding film pattern is formed on the transparent substrate. The evaluation of the light-shielding film pattern was performed by forming a line and gap pattern of 1.9 μm, and observing the cross-sectional shape of the light-shielding film pattern by a scanning electron microscope (SEM). As a result, as shown in FIG. 4, it was confirmed that the cross-sectional shape was nearly vertical. 4 is a view for explaining the perpendicularity of the cross-sectional shape of the light-shielding film pattern formed by the wet etching of the photomask substrate of Example 1, respectively, showing that the appropriate etching time (JET) is used as a reference (100%). The etching time was set to 110%, 130%, and 150%, and the cross-sectional shape at the time of over-etching was performed. In Fig. 4, a light-shielding film pattern and a resist film pattern were laminated on a transparent substrate, and it was confirmed that the side surface of the light-shielding film pattern was 70° with respect to the transparent substrate when JET was 100%. Even if the etching time is in the range of 60° to 80° when the etching time is 110%, 130%, and 150% of JET, it has been confirmed that the light shielding film pattern can be stably formed vertically without being affected by the etching time. The shape of the section.

In the light-shielding film of the reticle base, the first reflection suppressing layer, the light-shielding layer, and the second reflection suppressing layer are laminated from the transparent substrate side, and the layers are formed so as to have a specific composition. The reflectance of the front and back surfaces can be reduced over a wide wavelength range, and the cross-sectional shape of the light-shielding film pattern when patterned by wet etching can be formed vertically.

(production of photomask)
Next, a photomask was produced using the reticle substrate of Example 1.
First, a phenolic positive resist is formed on the light shielding film of the photomask base. Then, using a laser drawing device, a pattern of a circuit pattern for a TFT (thin-film transistor) panel is drawn on the resist film, and further developed and washed to form a specific resist pattern (the above-described circuit pattern) The minimum line width is 0.75 μm).
Thereafter, using a resist pattern as a mask, the light-shielding film is patterned by wet etching using a chromium etching solution, and finally, the resist pattern is peeled off by a resist stripping solution to obtain a light-shielding formed on the transparent substrate. A mask of a film pattern (mask pattern). In the reticle, the aperture ratio of the light-shielding film pattern (mask pattern) formed on the transparent substrate, that is, the exposure of the transparent substrate on which the light-shielding film pattern is not formed, is formed in the entire surface of the mask in which the light-shielding film pattern is formed. The ratio is 45%.
The CD uniformity of the light-shielding film pattern of the photomask was measured using "SIR8000" manufactured by Seiko Instruments Nano Technology Co., Ltd. The measurement of CD uniformity was carried out at 11 × 11 sites in a region of 1100 mm × 1300 mm excluding the peripheral region of the substrate.
As a result, the CD uniformity was 100 nm, and the CD uniformity of the obtained photomask was good.

(production of LCD panel)
The photomask produced in the first embodiment was placed on a mask stage of an exposure apparatus, and a TFT array was produced by pattern-exposed a transfer target on which a resist film was formed on a substrate for a display device (TFT). As the light for exposure, a composite light including an I-ray having a wavelength of 365 nm, an H-ray having a wavelength of 405 nm, and a G-ray having a wavelength of 436 nm is used.
A TFT-LCD (thin film transistor liquid crystal display) panel was produced by combining the fabricated TFT array with a color filter, a polarizing plate, and a backlight. As a result, a TFT-LCD panel without display unevenness was obtained. The reason for this is considered to be that when pattern exposure is performed using a photomask, reflection of light on the front and back surfaces can be suppressed, and the total amount of reflected light can be reduced.

(Example 2)
In the present embodiment, the film formation conditions of the first reflection suppression layer and the film formation conditions of the second reflection suppression layer in the first embodiment were changed as follows, and the first reflection was deposited on a transparent substrate having a substrate size of 1220 mm × 1400 mm. The suppression layer, the light shielding layer, and the second reflection suppressing layer were used to form a mask base having a light shielding film.

The film formation condition of the first reflection suppressing film is that the sputtering target is a Cr sputtering target, and the flow rate of the reactive gas is a metal mode, and the flow rate of oxygen (O ₂ ) is selected from the range of 25 to 45 sccm. The flow rate of nitrogen (N ₂ ) is selected from the range of 40 to 60 sccm, the flow rate of argon (Ar) is selected from the range of 80 to 120 sccm, and the target application power is set to 1.5 to 5.0 kW, and the applied voltage of the target is set. It is in the range of 380 to 400 V. In addition, the substrate conveyance speed at the time of film formation of the first reflection suppression layer was set to 300 mm/min.

Further, the second reflection suppressing film of the film formation conditions of the sputtering target to sputtering Cr target, and the flow rate of the reactive gases as to be a pattern of metal, from the range of 8 ~ 25 sccm of oxygen gas selected (O ₂₎ of For the flow rate, the flow rate of nitrogen (N ₂ ) is selected from the range of 30 to 40 sccm, the flow rate of argon gas (Ar) is selected from the range of 90 to 120 sccm, and the target application power is set to 3.5 to 8.0 kW, and the target is applied with a voltage. Set to a range of 435 to 455 V. In addition, the substrate conveyance speed at the time of film formation of the 2nd reflection suppression layer was 250 mm/min.

(evaluation of the reticle base)
With respect to the mask base of Example 2, the optical density of the light-shielding film and the reflectance of the front surface and the back surface of the light-shielding film were evaluated in the same manner as in Example 1.
With respect to the reticle substrate of Example 2, the optical density of the light-shielding film was 5.1 at the G-ray (wavelength 436 nm) of the wavelength band of the light to be exposed. Further, it has been confirmed that the peak wavelength of the reflectance spectrum of the front side and the back side can be set to be around 400 nm, and the reflectance can be greatly reduced with respect to light of a wide wavelength. Specifically, at a wavelength of 365 nm to 436 nm, the front surface reflectance of the light-shielding film is 7.5% or less (7.5% (wavelength 365 nm), 4.9% (wavelength 405 nm), 4.9% (wavelength 413 nm), 6.3%). (wavelength 436 nm)), the back surface reflectance of the light-shielding film is 5% or less (2.8% (wavelength 365 nm), 1.6% (wavelength 405 nm), 3.9% (wavelength 436 nm)). It has been confirmed that the reflectance of the front surface and the back surface of the light-shielding film can be reduced to 7.5% or less at a wavelength of 365 nm to 436 nm, and in particular, the front reflectance can be set to 4.9% with respect to the reflectance of light having a wavelength of 405 nm. The back reflectance was set to 1.6%.
Further, the dependence of the front reflectance of the light-shielding film in the range of the exposure wavelength of 365 nm to 436 nm was 2.6%, and the dependence of the back surface reflectance was 2.5%.
Further, the front surface reflectance of the light-shielding film at a wavelength of 530 nm was 22.8%.
In the wavelength band from 200 nm to 500 nm, the wavelength (bottom peak wavelength) corresponding to the minimum (bottom peak) of the front reflectance and the back reflectance is 404 nm and the back reflectance is 394 nm.

(production of photomask)
Next, in the same manner as in Example 1, a photomask was produced using the mask base of Example 2, and as a result, the CD uniformity was 92 nm, and the obtained mask had good CD uniformity.

(production of LCD panel)
The photomask produced in the second embodiment was placed on a mask stage of an exposure apparatus, and a transfer target having a resist film formed on a substrate for a display device (TFT) was subjected to pattern exposure to fabricate a TFT array. As the light for exposure, a composite light including an I-ray having a wavelength of 365 nm, an H-ray having a wavelength of 405 nm, and a G-ray having a wavelength of 436 nm is used. A TFT-LCD panel was produced by combining the fabricated TFT array with a color filter, a polarizing plate, and a backlight. As a result, a TFT-LCD panel without display unevenness was obtained. The reason for this is considered to be that when pattern exposure is performed using a photomask, reflection of light on the front and back surfaces can be suppressed, and the total amount of reflected light can be reduced.

(Example 3)
A photomask was produced in the same manner as in Example 1 except that the photomask substrate of Example 1 was used, and a photomask having a slit pattern having a line width of 1.2 μm was produced. Further, the aperture ratio of the mask formed on the transparent substrate was 38%.
The film uniformity of the light-shielding film pattern of the photomask was 82 nm, and the obtained film mask had good CD uniformity.
The photomask produced in Example 3 was placed on a mask stage of an exposure apparatus, and a TFT array was produced by pattern-exposed a transfer target on which a resist film was formed on a substrate for a display device (TFT). As the light for exposure, a composite light including an I-ray having a wavelength of 365 nm, an H-ray having a wavelength of 405 nm, and a G-ray having a wavelength of 436 nm is used. A TFT-LCD panel was produced by combining the fabricated TFT array with a color filter, a polarizing plate, and a backlight. As a result, a TFT-LCD panel without display unevenness was obtained. The reason for this is considered to be that when pattern exposure is performed using a photomask, reflection of light on the front and back surfaces can be suppressed, and the total amount of reflected light can be reduced.

(Example 4)
A photomask substrate was produced in the same manner as in Example 1 except that a phase shift film was formed between the transparent substrate and the light-shielding film in the photomask substrate of Example 1.
The phase shift film is formed into a film in the following manner.
The film formation condition of the phase shift film is to set the sputtering target to a MoSi sputtering target (Mo: Si = 1:4) by using a mixture of argon gas, nitrogen gas (N ₂ ), and nitric oxide gas (NO). The reactive sputtering of the gas was carried out to form a phase shift film containing MoSiON having a film thickness of 183 nm. Further, the gas flow rate of the mixed gas was set to Ar gas: 40 sccm, N ₂ gas: 34 sccm, and NO gas: 34.5 sccm. Further, the phase shift film had a transmittance of 27% (wavelength: 405 nm) and a phase difference of 173 (wavelength: 405 nm).
Next, a light-shielding film including a first reflection suppressing layer, a light-shielding layer, and a second reflection suppressing layer was formed on the phase-shift film in the same manner as in Example 1 to produce a mask base.

(evaluation of the reticle base)
The back surface reflectance of the phase shift film in the photomask substrate of Example 4 was 10.0% or less (4.2% (wavelength 365 nm), 6.2% (wavelength 405 nm), and 9.2% (wavelength 436 nm)). Further, the front surface reflectance of the light-shielding film was 10.0% or less (7.7% (wavelength 365 nm), 1.8% (wavelength 405 nm), 1.1% (wavelength 413 nm), and 0.3% (wavelength 436 nm)). The mask base of Example 4 can reduce the back reflectance of the phase shift film to 10% or less and the front reflectance of the light-shielding film to 10% or less at a wavelength of 365 nm to 436 nm, and further the phase shift film. The wavelength dependence of the back reflectance is 5% or less.

(Mask production, and LCD panel production)
Next, a photomask was fabricated using the photomask substrate of Example 4.
First, a phenolic positive resist is formed on the light shielding film of the photomask base. Then, using a laser drawing device, a pattern of a hole having a hole diameter of 1.2 μm was drawn on the resist film, and further development and rinsing were performed to form a first resist pattern.
Thereafter, the light-shielding film is patterned by wet etching using the first resist pattern as a mask, and a light-shielding film pattern is formed on the phase shift film by using a chromium etching solution.
Next, the light-shielding film pattern was used as a mask, and the phase-shift film was patterned by wet etching using a molybdenum-molybdenum etching liquid to form a phase-shift film pattern. Thereafter, the first resist pattern is peeled off.
Thereafter, a resist film is formed so as to cover the light shielding film pattern, and a pattern is drawn using a laser drawing device, and further development and rinsing are performed to form a second resist for forming a light shielding tape on the phase shift film pattern. pattern.
Thereafter, the second resist pattern is used as a mask, and the light-shielding film is patterned by wet etching using a chromium etching solution, and a light-shielding film pattern for the light-shielding tape is formed on the phase-shift film, and finally 2 The resist pattern was peeled off to produce a photomask.
In this manner, a phase shift film pattern having a hole diameter of 1.2 μm and a photomask including a light-shielding tape having a laminated structure of a phase shift film pattern and a light-shielding film pattern were obtained on the transparent substrate.
The phase uniformity film pattern of the mask has a CD uniformity of 90 nm, and the obtained mask has good CD uniformity.
Further, a TFT-CLD panel was produced by using the photomask produced in Example 4, and as a result, a TFT-LCD panel having no display unevenness was obtained. The reason for this is considered to be that when pattern exposure is performed using a photomask, reflection of light on the front and back surfaces can be suppressed, and the total amount of reflected light can be reduced.

(Comparative Example 1)
As a comparative example, a first masking suppression layer, a light shielding layer, and a second reflection suppressing layer were laminated on a transparent substrate having a substrate size of 1220 mm × 1400 mm to produce a mask substrate having a light shielding film.

The film formation condition of the first reflection suppression layer is that the sputtering target is a Cr sputtering target, and the flow rate of the reactive gas is a reaction mode, and the flow rate of carbon dioxide (CO ₂ ) is selected from the range of 100 to 250 sccm. The flow rate of nitrogen (N ₂ ) is selected from the range of 150 to 350 sccm, the flow rate of methane (CH ₄ ) gas is selected from the range of 0 to 15 sccm, and the flow rate of argon (Ar) is selected from the range of 150 to 300 sccm, and The target application power is set to a range of 2.0 to 7.0 kW. In addition, the substrate transfer speed at the time of film formation of the first reflection suppression layer was set to 200 mm/min, and film formation was performed three times.

The film formation condition of the light shielding layer is such that the sputtering target is a Cr sputtering target, and the flow rate of the reactive gas is a metal mode, and the flow rate of nitrogen (N ₂ ) is selected from the range of 1 to 60 sccm, from 60 to The flow rate of argon gas (Ar) was selected in the range of 200 sccm, and the target application power was set in the range of 5.0 to 8.0 kW. Further, the substrate transport speed at the time of film formation of the light shielding layer was set to 200 mm/min.

The film formation condition of the second reflection suppressing layer is that the sputtering target is a Cr sputtering target, and the flow rate of the reactive gas is a reaction mode, and the flow rate of carbon dioxide (CO ₂ ) is selected from the range of 100 to 300. The flow rate of nitrogen (N ₂ ) is selected in the range of 150 to 350 sccm, the flow rate of methane (CH ₄ ) gas is selected from the range of 0 to 15 sccm, and the flow rate of argon (Ar) is selected from the range of 150 to 300 sccm, and The target application power is set in the range of 2.0 to 7.0 kW. In addition, the substrate transport speed at the time of film formation of the second reflection suppression layer was set to 200 mm/min, and film formation was performed three times.

In the same manner as in the above-described first embodiment, the optical density of the light-shielding film and the reflectance of the front surface and the back surface of the light-shielding film were measured for the mask base of Comparative Example 1. As a result, the optical density of the light-shielding film was 5.1 at the G-ray (wavelength 436 nm) in the wavelength band of the light to be exposed. Further, at a wavelength of 365 nm to 436 nm, the front surface reflectance of the light-shielding film is 5.0% or less (2.8% (wavelength 365 nm), 3.5% (wavelength 405 nm), 3.9% (wavelength 413 nm), 4.8% (wavelength). 436 nm)), the back surface reflectance of the light-shielding film is 12% or less (11.2% (wavelength 365 nm), 7.1% (wavelength 405 nm), 4.9% (wavelength 436 nm)). The front surface reflectance of the light-shielding film at a wavelength of 365 nm to 436 nm is 5% or less, but the back surface reflectance exceeds 10%, and becomes 11.2% at a wavelength of 365 nm.
Further, the front surface reflectance dependence of the light-shielding film in the range of the exposure wavelength of 365 nm to 436 nm was 2.0%, and the back surface reflectance dependency was 6.3%.
In the wavelength band of 300 nm to 500 nm, the wavelength (bottom peak wavelength) corresponding to the minimum (bottom peak) of the front reflectance and the back reflectance is 337 nm, and the back reflectance is 474 nm.

(production of photomask)
Next, a photomask was produced in the same manner as in Example 1 using the mask base of Comparative Example 1. The CD uniformity of the light-shielding film pattern of the obtained photomask was measured and found to be 155 nm, which was inferior to Examples 1 and 2.
(production of LCD panel)
The photomask produced in Comparative Example 1 was placed on a mask stage of an exposure apparatus, and a TFT array was produced by pattern-exposed a transfer target on which a resist film was formed on a substrate for a display device (TFT). As the light for exposure, a composite light including an I-ray having a wavelength of 365 nm, an H-ray having a wavelength of 405 nm, and a G-ray having a wavelength of 436 nm is used. A TFT-LCD panel was produced by combining the fabricated TFT array with a color filter, a polarizing plate, and a backlight. As a result, in the TFT-LCD panel produced by using the photomask of Comparative Example 1, it was confirmed that display unevenness occurred. The reason for this is considered to be that, in the mask of Comparative Example 1, when pattern exposure is performed, reflection of light at the exposure wavelength (365 nm to 436 nm), particularly the back surface of the light-shielding film, cannot be sufficiently suppressed, and as a result, reflection is caused. The total amount of light increases.

1‧‧‧Photomask base

11‧‧‧Transparent substrate

12‧‧‧Shade film

13‧‧‧1st reflection suppression layer

14‧‧‧Lighting layer

15‧‧‧2nd reflection suppression layer

Fig. 1 is a cross-sectional view showing a schematic configuration of a mask base according to an embodiment of the present invention.

Fig. 2 is a view showing the results of composition analysis of the film thickness direction in the photomask substrate of Example 1.

Fig. 3 is a view showing the reflectance spectra of the front side and the back side of the reticle base of Example 1.

Fig. 4 is a view for explaining the characteristics of the cross-sectional shape of the light-shielding film pattern of the photomask produced by using the photomask substrate of the first embodiment.

Fig. 5 is a schematic view for explaining a film formation mode in a case where a light shielding film is formed by reactive sputtering.

Claims (16)

A reticle substrate, characterized in that it is used by a user who manufactures a reticle for manufacturing a display device, and has: a transparent substrate constructed of a material that is substantially transparent to exposed light; and a light shielding film disposed on the transparent substrate and formed of a material substantially opaque to the exposed light; The light shielding film includes a first reflection suppressing layer, a light shielding layer, and a second reflection suppressing layer from the side of the transparent substrate. When the surface on the light-shielding film side of the both surfaces of the mask base is the front surface and the surface on the transparent substrate side is the back surface, the exposure light is in the range of 365 nm to 436 nm. The front reflectance and the back reflectance are each 10% or less, and the wavelength dependence of the back reflectance in the above wavelength range is 5% or less. The reticle substrate of claim 1, wherein the back surface reflectance is smaller than the front surface reflectance in a range of exposure wavelengths from 365 nm to 436 nm. The reticle substrate of claim 1 or 2, wherein the front surface reflectance and the back surface reflectance of the reticle base are set to a vertical axis, and the wavelength is set to a horizontal axis to obtain a reflectance spectrum over the wavelength 300. In the wavelength band of nm to 500 nm, the reflectance spectra of the front surface and the back surface are respectively downward convex curves, and the wavelengths corresponding to the front surface reflectance and the minimum value of the back surface reflectance (bottom peak) are located at 350 nm. ~450 nm. The reticle substrate of claim 1 or 2, wherein the wavelength dependence of the back surface reflectance is less than the wavelength dependence of the front side reflectance in the range of the exposure wavelength of 365 nm to 436 nm. The reticle substrate of claim 1 or 2, wherein the front side reflectance is 10% or more in a wavelength range of 530 nm or more. The photomask substrate according to claim 1 or 2, wherein the first reflection suppressing layer contains a chromium-based material of chromium, oxygen and nitrogen, and has a chromium content of 25 to 75 at% and an oxygen content of 15 to 45. A composition of atomic % and nitrogen content of 10 to 30 atom%, The light-shielding layer contains a chromium-based material of chromium and nitrogen, and has a composition in which the content of chromium is 70 to 95% by atom and the content of nitrogen is 5 to 30% by atom. The second reflection suppressing layer is a chromium-based material containing chromium, oxygen, and nitrogen, and has a chromium content of 30 to 75 atom%, an oxygen content of 20 to 50 atom%, and a nitrogen content of 5 to 20 atoms. The composition of %. The photomask substrate according to claim 6, wherein the first reflection suppressing layer has a chromium content of 50 to 75 atom%, an oxygen content of 15 to 35 atom%, and a nitrogen content of 10 to 25 atom%. , In the second reflection suppressing layer, the content of chromium is 50 to 75 atom%, the content of oxygen is 20 to 40 atom%, and the content of nitrogen is 5 to 20 atom%. The mask base of claim 6, wherein the second reflection suppressing layer is configured to have a higher oxygen content than the first reflection suppressing layer. The mask base of claim 6, wherein the first reflection suppressing layer is configured to have a higher nitrogen content than the second reflection suppressing layer. The reticle substrate of claim 1 or 2, wherein the transparent substrate is a rectangular substrate, and a short side of the substrate has a length of 850 mm or more and 1620 mm or less. The reticle substrate of claim 1 or 2, further comprising a semi-transmissive film between the transparent substrate and the light-shielding film, the semi-transmissive film having an optical density lower than an optical density of the light-shielding film. The reticle substrate of claim 1 or 2, further comprising a phase shifting film for shifting a phase of the transmitted light between the transparent substrate and the light shielding film. A method of manufacturing a photomask, comprising the steps of: Preparing the above-described reticle substrate as claimed in claim 1 or 2; A resist film is formed on the light-shielding film, and the light-shielding film is etched by using a resist pattern formed of the resist film as a mask, and a light-shielding film pattern is formed on the transparent substrate. A method of manufacturing a photomask, comprising the steps of: Preparing the above-mentioned photomask substrate as claimed in claim 11; Forming a resist film on the light-shielding film, etching the light-shielding film by using a resist pattern formed by the resist film as a mask, and forming a light-shielding film pattern on the transparent substrate; The semi-transmissive film is etched by using the light-shielding film pattern as a mask, and a semi-transmissive film pattern is formed on the transparent substrate. A method of manufacturing a photomask, comprising the steps of: Preparing the above-described photomask substrate as claimed in claim 12; Forming a resist film on the light-shielding film, etching the light-shielding film by using a resist pattern formed by the resist film as a mask, and forming a light-shielding film pattern on the transparent substrate; The phase shift film is etched by using the light shielding film pattern as a mask, and a phase shift film pattern is formed on the transparent substrate. A manufacturing method of a display device, characterized by having an exposure step of placing a photomask obtained by the manufacturing method of the photomask of claim 13 on a photomask stage of an exposure device, which is formed in the above At least one of the light shielding film pattern, the semi-transmissive film pattern, and the phase shift film pattern on the photomask is exposed and transferred to a resist formed on a substrate of the display device.