JP6625692B2 - Photomask blank and method for manufacturing the same, photomask manufacturing method, and display device manufacturing method - Google Patents

Description

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

  In a display device such as an FPD (Flat Panel Display) represented by an LCD (Liquid Crystal Display), a large screen, a wide viewing angle, a high definition, and a high-speed display are rapidly progressing. One of the elements required for high definition and high-speed display is the production of electronic circuit patterns such as fine elements and wiring with high dimensional accuracy. Photolithography is often used for patterning the display device electronic circuit. For this reason, a photomask for manufacturing a display device on which a fine and high-precision pattern is formed is required.

  A photomask for manufacturing a display device is manufactured from a photomask blank. The photomask blank is configured by providing a light-shielding film made of a material opaque to exposure light on a transparent substrate made of synthetic quartz glass or the like. In a photomask blank or a photomask, a reflection suppressing layer is provided on both front and back surfaces of a light-shielding film in order to suppress light reflection upon exposure. The photomask blank is, for example, a first mask in order from a transparent substrate side. It has a film configuration in which a reflection suppressing layer, a light shielding layer and a second reflection suppressing layer are laminated. The photomask is manufactured by patterning a light shielding film of a photomask blank by wet etching or the like to form a predetermined mask pattern.

  Patent Document 1 discloses a photomask for manufacturing such a display device, a photomask blank as an original plate thereof, and a technique related to a method for manufacturing both of them.

Korean Registered Patent No. 10-147163

  In the manufacture of a display device (for example, a display panel for a TV), a predetermined pattern is transferred to a display device substrate using a photomask, and then the display device substrate is slid to transfer the predetermined pattern. Thus, pattern transfer is repeatedly performed. In this transfer, the reflected light on the back side of the photomask when the exposure light is incident on the photomask from the light source of the exposure apparatus, or the reflected light from the transfer target after the exposure light passes through the photomask is transferred to the front surface of the photomask. Due to the reflected light returning to the side, exposure light more than expected may be irradiated in the vicinity of the superposition of the display device. As a result, adjacent patterns are exposed so as to partially overlap each other, and display unevenness may occur in a manufactured display device.

  Therefore, in the photomask blank, the reflectance of the front and back surfaces of the light-shielding film is set to 10% or less (for example, 365 nm to 436 nm), and more preferably 5% or less (for example, 400 nm to 436 nm) in order to suppress display unevenness. Is required. Furthermore, from the viewpoint of improving the CD uniformity of the photomask, considering the surface reflection of the light-shielding film with respect to laser writing light, the reflectance of the light-shielding film surface is 5% or less (for example, a wavelength of 413 nm), and more preferably 3%. The following (for example, a wavelength of 413 nm) is required.

  In addition, as for photomasks for manufacturing display devices, in addition to demands for higher definition and higher speed display of display devices, the size of substrates has been increasing, and in recent years, a rectangular shape having a short side of 850 mm or more has been used. 2. Description of the Related Art An ultra-large photomask using a shape substrate is used for manufacturing a display device. Note that the above-described large-sized photomasks having a short side of 850 mm or more include 850 mm × 1200 mm size for G7, 1220 mm × 1400 mm size for G8, and 1620 mm × 1780 mm size for G10. There is a demand for a high-precision mask pattern of 100 nm or less as the CD uniformity (CD Uniformity) of the mask pattern in the photomask.

  In the conventionally proposed photomask blank of Patent Document 1, 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 is set to 10% or less with respect to the exposure wavelength, and The requirement that the CD uniformity of a mask pattern of a photomask manufactured using a mask blank be 100 nm or less could not be satisfied.

  The present invention provides a photomask blank that satisfies optical characteristics such that a high-precision mask pattern can be obtained when a photomask is manufactured by etching, and display unevenness can be suppressed when a display device is manufactured using the photomask. The purpose is to provide.

(Configuration 1)
A photomask blank used when manufacturing a photomask for manufacturing a display device,
A transparent substrate made of a material substantially transparent to exposure light,
Provided on the transparent substrate, a light-shielding film made of a material substantially opaque to the exposure light,
The light shielding film includes a first reflection suppression layer, a light shielding layer, and a second reflection suppression layer from the transparent substrate side,
The first reflection suppressing layer is a chromium-based material containing chromium, oxygen, and nitrogen, and has a chromium content of 25 to 75 atomic%, an oxygen content of 15 to 45 atomic%, and a nitrogen content. Has a composition of 10 to 30 atomic%,
The light-shielding layer is a chromium-based material containing chromium and nitrogen, and has a composition with a chromium content of 70 to 95 atomic% and a nitrogen content of 5 to 30 atomic%,
The second reflection suppressing layer is a chromium-based material containing chromium, oxygen, and nitrogen, and has a chromium content of 30 to 75 atomic%, an oxygen content of 20 to 50 atomic%, and a nitrogen content. Has a composition of 5 to 20 atomic%,
The first antireflection layer, the light-shielding layer, and the light-shielding film have a reflectance of 10% or less with respect to an exposure wavelength of the exposure light, and an optical density of 3.0 or more. And a film thickness of the second reflection suppressing layer is set.

(Configuration 2)
The first antireflection layer has a chromium content of 50 to 75 atomic%, an oxygen content of 15 to 35 atomic%, and a nitrogen content of 10 to 25 atomic%.
The second reflection suppressing layer has a chromium content of 50 to 75 atomic%, an oxygen content of 20 to 40 atomic%, and a nitrogen content of 5 to 20 atomic%. The photomask blank as described.

(Configuration 3)
The first antireflection layer and the second antireflection layer each have a region in which the content of at least one of oxygen and nitrogen changes in composition continuously or stepwise along the film thickness direction. 3. The photomask blank according to configuration 1 or 2, wherein

(Configuration 4)
The photomask blank according to any one of Configurations 1 to 3, wherein the second reflection suppressing layer has a region in which the oxygen content increases toward the light-shielding layer in the thickness direction.

(Configuration 5)
The photomask blank according to any one of Configurations 1 to 4, wherein the second reflection suppressing layer has a region where the nitrogen content decreases toward the light-shielding layer in the thickness direction.

(Configuration 6)
Any one of the constitutions 1 to 5, wherein the first reflection suppressing layer has a region in which the oxygen content increases and the nitrogen content decreases toward the transparent substrate in the film thickness direction. 2. The photomask blank according to 1.

(Configuration 7)
The photomask blank according to any one of Configurations 1 to 6, wherein the second antireflection layer has a higher oxygen content than the first antireflection layer.

(Configuration 8)
The photomask blank according to any one of Configurations 1 to 7, wherein the first reflection suppression layer is configured to have a higher nitrogen content than the second reflection suppression layer.

(Configuration 9)
The light shielding layer is chromium (Cr) and photomask blank of any one of configurations 1 to 8, characterized in that it comprises a nitride dichromate (Cr 2 _N).

(Configuration 10)
The first antireflection layer and the second antireflection layer, characterized in that it comprises a chromium nitride (CrN) and chromium oxide _{(III) (Cr 2 O 3} ) and chromium oxide (VI) (CrO ₃₎ The photomask blank according to any one of Configurations 1 to 9,

(Configuration 11)
The photomask blank according to any one of Configurations 1 to 10, wherein the transparent substrate is a rectangular substrate, and a length of a short side of the substrate is 850 mm or more and 1620 mm or less.

(Configuration 12)
12. The photolithography device according to claim 1, further comprising a semi-transmissive film having an optical density lower than an optical density of the light-shielding film between the transparent substrate and the light-shielding film. Mask blank.

(Configuration 13)
12. The photomask blank according to any one of Configurations 1 to 11, further comprising a phase shift film between the transparent substrate and the light shielding film.

(Configuration 14)
A photomask for manufacturing a display device is manufactured, in which a light-shielding film made of a material substantially opaque to exposure light is formed by a sputtering method on a transparent substrate made of a material substantially transparent to exposure light. It is a method for manufacturing a photomask blank used at the time,
On the transparent substrate, a sputtering target containing chromium, an oxygen-based gas, a reactive gas containing a nitrogen-based gas, and a sputtering gas containing a rare gas, by reactive sputtering using chromium, oxygen, and nitrogen. A first antireflection layer comprising a chromium-based material containing 25 to 75 atomic% of chromium, 15 to 45 atomic% of oxygen, and 10 to 30 atomic% of nitrogen. Forming a;
On the first reflection suppressing layer, chromium containing chromium and nitrogen by reactive sputtering using a sputter target containing chromium, and a sputtering gas containing a reactive gas containing a nitrogen-based gas and a rare gas. Forming a light-shielding layer which is a system material and has a composition in which the content of chromium is 70 to 95 atomic% and the content of nitrogen is 5 to 30 atomic%;
On the light-shielding layer, chromium, oxygen, and nitrogen were formed by reactive sputtering using a sputtering target containing chromium, an oxygen-based gas, a reactive gas containing a nitrogen-based gas, and a sputtering gas containing a rare gas. A second antireflection layer having a chromium content of 30 to 75 atomic%, an oxygen content of 20 to 50 atomic%, and a nitrogen content of 5 to 20 atomic%. Forming, and
In the reactive sputtering, the flow rate of the reactive gas included in the sputtering gas is selected to be a flow rate in the metal mode, and the reflectance of the front and back surfaces of the light shielding film with respect to the exposure wavelength of the exposure light is 10% or less. A thickness of the first antireflection layer, the light-shielding layer, and the second antireflection layer so as to have an optical density of 3.0 or more. .

(Configuration 15)
15. The method for producing a photomask blank according to Configuration 14, wherein the oxygen-based gas is an oxygen (O ₂ ) gas.

(Configuration 16)
The first antireflection layer, the light-shielding layer, and the second antireflection layer are formed using an in-line sputtering apparatus that forms the light-shielding film while the transparent substrate moves relative to the sputter target. 16. The method for manufacturing a photomask blank according to configuration 14 or 15, wherein

(Configuration 17)
The photo according to any one of Configurations 14 to 16, wherein a semi-transparent film having an optical density lower than the optical density of the light-shielding film is formed between the transparent substrate and the light-shielding film. Manufacturing method of mask blank.

(Configuration 18)
The method for manufacturing a photomask blank according to any one of the constitutions 14 to 16, wherein a phase shift film is formed between the transparent substrate and the light shielding film.

(Configuration 19)
Preparing the photomask blank according to any one of configurations 1 to 11,
Forming a resist film on the light shielding film, forming a light shielding film pattern on the transparent substrate by etching the light shielding film using a resist pattern formed from the resist film as a mask,
A method for manufacturing a photomask, comprising:

(Configuration 20)
Providing the photomask blank described in Configuration 12;
Forming a resist film on the light shielding film, forming a light shielding film pattern on the transparent substrate by etching the light shielding film using a resist pattern formed from the resist film as a mask,
Forming a semi-transparent film pattern on the transparent substrate by etching the semi-transparent film using the light-shielding film pattern as a mask,
A method for manufacturing a photomask, comprising:

(Configuration 21)
Providing the photomask blank described in configuration 13;
Forming a resist film on the light shielding film, forming a light shielding film pattern on the transparent substrate by etching the light shielding film using a resist pattern formed from the resist film as a mask,
Forming a phase shift film pattern on the transparent substrate by etching the phase shift film using the light shielding film pattern as a mask,
A method for manufacturing a photomask, comprising:

(Configuration 22)
A photomask obtained by the method for manufacturing a photomask described in any one of the constitutions 19 to 21 is placed on a mask stage of an exposure apparatus, and the light-shielding film pattern formed on the photomask, A method of manufacturing a display device, comprising: exposing at least one mask pattern of a light-transmitting film pattern and the phase shift film pattern to a resist formed on a display device substrate.

  ADVANTAGE OF THE INVENTION According to this invention, the photomask blank which is excellent in pattern precision and can manufacture the photomask which has optical characteristics which can suppress display unevenness at the time of manufacture of a display apparatus is obtained.

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a photomask blank according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a composition analysis result in a film thickness direction of the photomask blank of Example 1. FIG. 3 is a diagram illustrating reflectance spectra of the front and back surfaces of the photomask blank of Example 1. FIG. 4 is a diagram for explaining the characteristics of the cross-sectional shape of a light-shielding film pattern of a photomask manufactured using the photomask blank of Example 1. FIG. 4 is a schematic diagram for explaining a film formation mode when a light shielding film is formed by reactive sputtering.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. Note that the following embodiment is one mode for embodying the present invention, and does not limit the present invention within its scope. In the drawings, the same or corresponding portions are denoted by the same reference characters, and description thereof may be simplified or omitted.

<Photomask blank>
A photomask blank according to one embodiment of the present invention will be described. The photomask blank of the present embodiment is, for example, light of a single wavelength selected from a wavelength range of 300 nm to 550 nm, or light of a plurality of wavelengths (for example, j-line (wavelength 313 nm), i-line (wavelength 365 nm), h-line). (405 nm) and a photomask for manufacturing a display device, which is exposed to composite light including g-line (wavelength: 436 nm). In this specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit and an upper limit.

  FIG. 1 is a sectional view showing a schematic configuration of a photomask blank according to one embodiment of the present invention. The photomask blank 1 includes a transparent substrate 11 and a light shielding film 12. Hereinafter, as a photomask blank according to an embodiment of the present invention, a binary photomask blank in which a mask pattern (transfer pattern) of the photomask 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 exposure light and has translucency. A substrate material having a transmittance for the 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, non-alkali glass, and low thermal expansion glass.

  The size of the transparent substrate 11 may be appropriately changed according to the size required for a photomask for manufacturing a display device. For example, the transparent substrate 11 may be a rectangular substrate having a short side length of 330 mm or more and 1620 mm or less. The transparent substrate 11 has a size of, for example, 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, 850 mm × 1400 mm, 1220 mm × 1400 mm, 1620 mm × 1780 mm Such a substrate can be used. In particular, the length of the short side of the substrate is preferably 850 mm or more and 1620 mm or less. By using such a transparent substrate 11, photomasks for manufacturing display devices G7 to G10 can be obtained.

(Light shielding film)
The light-shielding film 12 is configured by laminating a first reflection suppression layer 13, a light-shielding layer 14, and a second reflection suppression layer 15 in this order from the transparent substrate 11 side. In the following, the description will be made with the transparent substrate 11 side of the photomask blank 1 as the back side and the light shielding film 12 side as the front side.

  The first antireflection layer 13 is provided on the light-shielding layer 12 on the side of the light-shielding layer 14 close to the transparent substrate 11, and the pattern is transferred using a photomask manufactured using the photomask blank 1. At the side close to the exposure light source. When an exposure process is performed using a photomask, exposure light is irradiated from the transparent substrate 11 side (back surface side) of the photomask, and a pattern transfer image is formed on a resist film formed on a display device substrate as a transfer target. Will be transcribed. At this time, if the exposure light is reflected on the back surface side of the light-shielding film pattern, it becomes stray light of the mask pattern, which is the light-shielding film pattern, and the transfer image deteriorates, such as formation of a ghost image and an increase in the amount of flare. In the vicinity of the overlapping of the substrates, display exposure may occur due to irradiation with more exposure light than expected. The first reflection suppressing layer 13 can suppress the reflection of the exposure light on the back surface side of the light shielding film 12 when performing the pattern transfer using the photomask, thereby suppressing the deterioration of the transferred image and improving the transfer characteristics. And in the vicinity of the superposition of the display device substrates, it is possible to suppress the occurrence of display unevenness due to irradiation of exposure light more than expected.

  The light shielding layer 14 is provided between the first reflection suppressing layer 13 and the second reflection suppressing layer 15 in the light shielding film 12. The light-shielding layer 14 has a function of adjusting the light-shielding film 12 to have an optical density so as to be substantially opaque to exposure light. Here, “substantially opaque to exposure light” means a light-shielding property having an optical density of 3.0 or more, and from the viewpoint of transfer characteristics, the optical density is preferably 4.0 or more, and more preferably 4.5 or more. Is preferred.

  The second reflection suppressing layer 15 is provided on the light shielding film 12 on the surface of the light shielding layer 14 far from the transparent substrate 11. The second anti-reflection layer 15 forms a resist film thereon, and draws a predetermined pattern on the resist film using drawing light (laser light) from a drawing device (eg, a laser drawing device). Since reflection on the surface side can be suppressed, the CD uniformity (CD Uniformity) of the resist pattern and the mask pattern formed based on the resist pattern can be improved. When the second reflection suppressing layer 15 is used as a photomask, the second reflection suppressing layer 15 is disposed on the display device substrate side, which is the transfer target, and the light reflected by the transfer target is on the surface side of the light shielding film 12 of the photomask. In addition to suppressing the reflected light from returning to the transfer object, suppressing the deterioration of the transferred image and contributing to the improvement of the transfer characteristics, exposure light more than expected is irradiated near the superposition of the display device substrate. This can suppress the occurrence of display unevenness.

(Material of light shielding film)
Subsequently, the material of each layer in the light shielding film 12 will be described.
The first reflection suppression layer 13 is made of a chromium-based material containing chromium, oxygen, and nitrogen. Oxygen in the first reflection suppressing layer 13 has an effect of reducing the reflectance of exposure light from the back surface side. Nitrogen in the first antireflection layer 13 not only has the effect of reducing the reflectance of the exposure light from the rear surface side, but also has a cross-section of a light-shielding film pattern formed by etching (particularly wet etching) using a photomask blank. And the effect of increasing the CD uniformity. From the viewpoint of controlling the etching characteristics, carbon and fluorine may be further contained.
The light shielding layer 14 is made of a chromium-based material containing chromium and nitrogen. Nitrogen in the light-shielding layer 14 reduces the etching rate difference between the first reflection-suppressing layer 13 and the second reflection-suppressing layer 15 and reduces the cross section of the light-shielding film pattern formed by etching (especially wet etching) using a photomask blank. And the etching time in the light-shielding film 12 (entire) is shortened, thereby improving CD uniformity. From the viewpoint of controlling the etching characteristics, oxygen, carbon and fluorine may be further contained.
The second reflection suppressing layer 15 is made of a chromium-based material containing chromium, oxygen, and nitrogen. Oxygen in the second reflection suppressing layer 15 has an effect of reducing the reflectance of drawing light of the drawing device from the front side and the reflectance of exposure light from the front side. Further, the adhesiveness with the resist film is improved, and the effect of suppressing the side etching due to the penetration of the etchant from the interface between the resist film and the light-shielding film 12 is exerted. Nitrogen in the second antireflection layer 15 has the effect of reducing the reflectance of drawing light from the front side and the reflectance of exposure light from the front side, and also has the effect of etching using a photomask blank (particularly wet etching). ) Has the effect of making the cross section of the light-shielding film pattern formed close to vertical and improving the CD uniformity. From the viewpoint of controlling the etching characteristics, carbon and fluorine may be further contained.

(Composition of light shielding film)
Subsequently, the composition of each layer in the light shielding film 12 will be described. The content of each element described below is a value measured by X-ray photoelectric spectroscopy (XPS).

  In the light shielding film 12, the first antireflection layer 13 contains chromium (Cr) at 25 to 75 atomic%, oxygen (O) at 15 to 45 atomic%, and nitrogen (N) at 10 to 30 atomic%. The light-shielding layer 14 contains 70 to 95 atomic% of chromium (Cr) and 5 to 30 atomic% of nitrogen (N), and the second antireflection layer 15 contains 30 to 75 atomic% of chromium (Cr). , And oxygen (O) at a content of 20 to 50 atomic% and nitrogen (N) at a content of 5 to 20 atomic%. Preferably, the first anti-reflection layer 13 contains 50 to 75 atomic% of Cr, 15 to 35 atomic% of O, and 10 to 25 atomic% of N, and the second anti-reflection layer 15 contains 50 to 75 atomic% of Cr. ７５75 at%, O at 20２０40 at%, and N at 5２０20 at%.

  Each of the first antireflection layer 13 and the second antireflection layer 15 has a region in which the content of at least one of O and N changes in composition continuously or stepwise along the film thickness direction. Is preferred.

  The second reflection suppressing layer 15 preferably has a region where the O content (oxygen content) increases toward the light-shielding layer 14 in the thickness direction.

  The second reflection suppressing layer 15 preferably has a region where the N content (the content of nitrogen) decreases toward the light-shielding layer 14 in the thickness direction.

  Further, the first antireflection layer 13 preferably has a region in which the O content increases and the N content decreases toward the transparent substrate 11 in the film thickness direction.

  Further, in the photomask blank 1 and the photomask produced therefrom, from the viewpoint of further reducing the reflectance on the front and back surfaces of the light shielding film 12 and the light shielding film pattern and reducing the difference between these reflectances, the second reflection suppression is preferable. The layer 15 is preferably configured to have a higher O content than the first anti-reflection layer 13, and the first anti-reflection layer 13 has a higher N content than the second anti-reflection layer 15. It is preferable to be constituted. Specifically, it is preferable that the O content of the second antireflection layer 15 be higher than that of the first antireflection layer 13 by 5 atomic% or more, more preferably 10 atomic% or more. Further, it is preferable that the N content of the first reflection suppressing layer 13 be 5 atom% or more, more preferably 10 atom% or more, than that of the second reflection suppressing layer 15. When the first antireflection layer 13 and the second antireflection layer 15 have a composition gradient region, the O content and the N content indicate average concentrations in the film thickness direction.

  In the first antireflection layer 13, the light-shielding layer 14, and the second antireflection layer 15, the change in the content of each element may be continuous or stepwise, but is preferably continuous.

(About bonding state (chemical state))
The light-shielding layer 14 preferably contains chromium (Cr) and dichromium nitride (Cr ₂ N).
It is preferable that the first antireflection layer 13 and the second antireflection layer 15 contain chromium mononitride (CrN), chromium (III) oxide (Cr ₂ O ₃ ), and chromium oxide (VI) (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 appropriately adjusted according to the optical density and the reflectance required of the light shielding film 12. Good to do. The thickness of the first anti-reflection layer 13 is such that the light from the back surface side of the light-shielding film 12 is reflected on the surface of the first anti-reflection layer 13 and at the interface between the first anti-reflection layer 13 and the light-shielding layer 14. It is sufficient if the thickness is such that an optical interference effect due to reflection is exhibited. On the other hand, the thickness of the second antireflection layer 15 is such that the light from the surface side of the light-shielding film 12 reflects the light on the surface of the second antireflection layer 15 and the interface between the second antireflection layer 15 and the light-shielding layer 14. Any thickness may be used as long as the optical interference effect due to reflection at the surface is exhibited. The thickness of the light shielding layer 14 may be such that the optical density of the light shielding film 12 is 3 or more. Specifically, from the viewpoint of setting the optical density of the light-shielding film 12 to 10% or less and the optical density of 3.0 or more in the light-shielding film 12, for example, the thickness of the first antireflection layer 13 is set to 15 nm. Preferably, the thickness of the light-shielding layer 14 is 50 nm to 120 nm, and the thickness of the second antireflection layer 15 is 10 nm to 60 nm.

<Method of manufacturing photomask blank>
Subsequently, a method for manufacturing the above-described photomask blank 1 will be described.

(Preparation process)
A transparent substrate 11 substantially transparent to exposure light is prepared. Note that an arbitrary processing step such as a grinding step and a polishing step may be performed as necessary so that the transparent substrate 11 has a flat and smooth main surface. After the polishing, cleaning is preferably performed to remove foreign substances and contamination on the surface of the transparent substrate 11. As the cleaning, for example, sulfuric acid, sulfuric acid peroxide (SPM), ammonia, ammonia peroxide (APM), OH radical cleaning water, ozone water, hot water, or the like can be used.

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

  Here, the metal mode will be described with reference to FIG. FIG. 5 is a schematic diagram for explaining a film forming mode when a thin film is formed by reactive sputtering, and the horizontal axis is a partial pressure (flow rate) of a reactive gas in a mixed gas of a rare gas and a reactive gas. The vertical axis indicates the voltage applied to the target. In reactive sputtering, when the target is discharged while introducing a reactive gas such as an oxygen-based gas or a nitrogen-based gas, the state of the discharge plasma changes in accordance with the flow rate of the reactive gas, and the plasma is formed accordingly. The film speed changes. There are three modes depending on the difference in the film forming speed. Specifically, as shown in FIG. 5, a reaction mode in which the supply amount (ratio) of the reactive gas is larger than a certain threshold, a metal mode in which the supply amount (ratio) of the reactive gas is smaller than the reaction mode, There is a transition mode in which the supply amount (ratio) of the reactive gas is set between the reaction mode and the metal mode. In the metal mode, by reducing the ratio of the reactive gas, the deposition of the reactive gas on the target surface can be reduced, and the deposition rate can be increased. Moreover, in the metal mode, since the supply amount of the reactive gas is small, at least one of the O concentration (oxygen concentration) and the N concentration (nitrogen concentration) is lower than that of a film having a stoichiometric composition, for example. Can be formed. That is, a film having a relatively high Cr content and a low O content or N content can be formed.

  The metal mode conditions for forming the first antireflection layer 13 include, for example, an oxygen-based gas flow rate of 5 to 45 sccm, a nitrogen-based gas flow rate of 30 to 60 sccm, and a rare gas flow rate of 60 to 150 sccm. Good to do. The target applied power is preferably 2.0 to 6.0 kW, and the target applied voltage is preferably 420 to 430 V.

The sputtering target may be any as long as it contains Cr. For example, in addition to chromium metal, chromium-based materials such as chromium oxide, chromium nitride, and chromium oxynitride can 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 ) and the like can be used. Among them, it is preferable to use oxygen (O ₂ ) gas because of its high oxidizing power. In addition, nitrogen (N ₂ ) or the like can be used as the nitrogen-based gas. As the rare gas, for example, helium gas, neon gas, argon gas, krypton gas, xenon gas, or the like can be used. In addition, a hydrocarbon-based gas may be supplied in addition to the reactive gas, for example, methane gas, butane gas, or the like can be used.

  In the present embodiment, the flow rate of the reactive gas and the power applied to the sputter target are set to be in the metal mode, and a film is formed by reactive sputtering using a sputter target containing Cr. A first anti-reflection layer 13 containing 25 to 75 atomic% of Cr, 15 to 45 atomic% of O, and 10 to 30 atomic% of N is formed on 11.

  When the first antireflection layer 13 is formed as a single film having a uniform composition in the film thickness direction, the film may be formed without changing the type and flow rate of the reactive gas. When the composition is gradient so that the ratio or the N content changes, the type and 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 may be appropriately changed. Further, the arrangement of the gas supply ports and the gas supply method may be changed.

(Process of forming light-shielding layer)
Subsequently, a light shielding layer 14 is formed on the first reflection suppressing layer 13. In this formation, a film is formed 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, a flow rate at which the flow rate of the reactive gas contained in the sputtering gas is set to the metal mode is selected as the film forming condition.
Any target may be used as long as it contains Cr. For example, chromium-based materials such as chromium oxide, chromium nitride, and chromium oxynitride can be used in addition to chromium metal. Nitrogen (N ₂ ) or the like can be used as the nitrogen-based gas. As the rare gas, for example, helium gas, neon gas, argon gas, krypton gas, xenon gas, or the like can be used. Note that, other than the reactive gas, the oxygen-based gas and 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 sputter target are set to a condition such that the metal mode is set, and the reactive sputtering is performed using a sputter target containing Cr. Next, a light-shielding layer 14 containing Cr at a content of 70 to 95 atomic% and N at a content of 5 to 30 atomic% is formed.

  As the film forming conditions of the light-shielding layer 14, for example, the flow rate of the nitrogen-based gas may be 1 to 60 sccm, and the flow rate of the rare gas may be 60 to 200 sccm. Further, it is preferable that the power applied to the target is 3.0 to 7.0 kW and the voltage applied to the target is 370 to 380 V.

(Step of forming second reflection suppressing layer)
Subsequently, the second reflection suppressing layer 15 is formed on the light shielding layer 14. This formation is performed by setting the flow rate of the reactive gas and the power applied to the target to the metal mode in the same manner as the first reflection suppression layer 13, and forming the film by reactive sputtering using a sputter target containing Cr. I do. Thus, the second antireflection layer 15 containing 30 to 75 atomic% of Cr, 20 to 50 atomic% of O, and 5 to 20 atomic% of N is formed on the light shielding layer 14.

  The metal mode conditions for forming the second reflection suppressing layer 15 include, for example, an oxygen-based gas flow rate of 8 to 45 sccm, a nitrogen-based gas flow rate of 30 to 60 sccm, and a rare gas flow rate of 60 to 150 sccm. Good to do. The target applied power is preferably 2.0 to 6.0 kW, and the target applied voltage is preferably 420 to 430 V.

  When the composition of the second antireflection layer is inclined, as described above, the type and flow rate of the reactive gas, the ratio of the oxygen-based gas and the nitrogen-based gas in the reactive gas, and the like may be appropriately changed.

  As described above, the photomask blank 1 of the present embodiment is obtained.

  Note that the formation of each layer in the light-shielding film 12 may be performed in-situ using an in-line type sputtering apparatus. If the apparatus is not an in-line type sputtering apparatus, it is necessary to take the transparent substrate 11 out of the apparatus after the formation of each layer, and the transparent substrate 11 may be exposed to the atmosphere, and the layers may be oxidized or carbonized. As a result, the reflectance and the etching rate of the light shielding film 12 with respect to the exposure light may be changed. In this regard, in the case of an in-line type sputtering apparatus, each layer can be continuously formed without taking out the transparent substrate 11 out of the apparatus and exposing it to the atmosphere. Can be.

  When the light-shielding film 12 is formed using an in-line type sputtering apparatus, a composition gradient region in which the composition of each of the first reflection suppression layer 13, the light-shielding layer 14, and the second reflection suppression layer 15 is continuously graded ( (Transition layer), which is preferable because the cross section of the light-shielding film pattern formed by etching (particularly wet etching) using a photomask blank can be made smooth and nearly vertical.

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

(Step of forming resist film)
First, a resist is applied on the second reflection suppressing layer 15 in the light shielding film 12 of the photomask blank 1 and dried to form a resist film. As the resist, it is necessary to select an appropriate resist according to the drawing apparatus to be used, but a positive or negative resist can be used.

(Step of forming resist pattern)
Subsequently, a predetermined pattern is drawn on the resist film using a drawing apparatus. Usually, when a photomask for manufacturing a display device is manufactured, a laser drawing device is used. After drawing, the resist film is developed and rinsed to form a predetermined resist pattern.

  In the present embodiment, since the reflectance of the second reflection suppressing layer 15 is configured to be low, when drawing a pattern on the resist film, reflection of drawing light (laser light) can be reduced. As a result, a resist pattern with high pattern accuracy can be formed, and a mask pattern with high dimensional accuracy can be formed accordingly.

(Mask pattern forming process)
Subsequently, the mask pattern composed of the light-shielding film pattern is formed by etching the light-shielding film 12 using the resist pattern as a mask. The etching may be wet etching or dry etching. Usually, in a photomask for manufacturing a display device, wet etching is performed. As an etching solution (etchant) used in the wet etching, for example, a chromium etching solution containing ceric ammonium nitrate and perchloric acid is used. be able to.

  In the present embodiment, since the composition of each layer is adjusted so that the etching rates of the first reflection suppressing layer 13, the light shielding layer 14, and the second reflection suppressing layer 15 are uniform in the thickness direction of the light shielding film 12, wet etching is performed. In this case, the cross-sectional shape of the light-shielding film pattern (mask pattern) can be made close to perpendicular to the transparent substrate 11, and high CD uniformity (CD Uniformity) can be obtained.

(Peeling process)
Subsequently, the resist pattern is stripped to obtain a photomask in which a light-shielding film pattern (mask pattern) is formed on the transparent substrate 11.

  As described above, the photomask according to the present embodiment is obtained.

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

(Preparation process)
First, a photomask obtained by the above-described photomask manufacturing method is formed on a substrate with a resist film having a resist film formed on a substrate of a display device via the projection optical system of the exposure device. The resist film is placed on a mask stage of an exposure apparatus so as to face the resist film thus formed.

(Exposure step (pattern transfer step))
Next, a resist exposure step of irradiating a photomask with exposure light to transfer a pattern to a resist film formed on a substrate of the display device is performed.
The exposure light is, for example, light of a single wavelength selected from a wavelength range of 300 nm to 550 nm (j-line (wavelength 313 nm), i-line (wavelength 365 nm), h-line (wavelength 405 nm), g-line (wavelength 436 nm), and the like). Alternatively, a composite light including light of a plurality of wavelengths (for example, j-line (wavelength 313 nm), i-line (wavelength 365 nm), h-line (405 nm), and g-line (wavelength 436 nm)) is used. In the present embodiment, since the display device (display panel) is manufactured using a photomask in which the reflectance of the front and back surfaces of the light-shielding film pattern (mask pattern) is reduced, a display device (display panel) having no display unevenness is manufactured. Obtainable.

<Effects according to the present embodiment>
According to the present embodiment, one or more of the following effects can be obtained.

(A) In the photomask blank 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 the first reflection suppressing layer 13 A chromium-based material containing chromium, oxygen, and nitrogen, having a composition having a Cr content of 25 to 75 atomic%, an O content of 15 to 45 atomic%, and a N content of 10 to 30 atomic%. The light-shielding layer 14 is a chromium-based material containing chromium and nitrogen, has a composition with a Cr content of 70 to 95 atomic% and a N content of 5 to 30 atomic%, and has a second reflection suppressing property. The layer 15 is a chromium-based material containing chromium, oxygen, and nitrogen, and has a Cr content of 30 to 75 atomic%, an O content of 20 to 50 atomic%, and an N content of 5 to 20 atomic%. It is configured to have a composition. The thicknesses of the first reflection suppression layer 13 and the second reflection suppression layer 15 are set so that the light interference effect can be maximized or nearly maximized. Thereby, the reflectance with respect to the exposure wavelength on the front and back surfaces of the photomask blank 1 can be reduced to 10% or less, respectively. Specifically, in the reflectance spectra of the front and back surfaces, the wavelength of the bottom peak at which the reflectance is minimum is 380 nm to 480 nm on the relatively high wavelength side, and the reflectance of light having a wavelength of 380 nm to 480 nm is 10% or less, preferably. Can be 7.5% or less. On the other hand, by setting the light-shielding layer 14 to a predetermined thickness, the optical density of the light-shielding film 12 can be set to 3.0 or more.

(B) In the present embodiment, the composition of the first reflection suppression layer 13 and the second reflection suppression layer 15 is appropriately changed within the above-described range, so that the rear surface side (the transparent substrate 11 side) of the photomask blank 1 is formed. The reflectance and the reflectance on the surface side (light-shielding film 12 side) can be adjusted. For example, it is possible to adjust the reflectance of the photomask blank 1 so that the front side is higher than the back side, the front side and the back side are the same, or the back side is higher than the front side. it can. From the viewpoint of suppressing the influence of the reflection of the exposure light from the photomask to the light source side (such as generation of a ghost) when the transfer target is exposed using the manufactured photomask, the reflectance on the back side is considered. Is preferably higher than the surface side. In other words, it is preferable that the reflectance on the front side (the light shielding film 12 side) of the photomask blank 1 be lower than the reflectance on the back side (the transparent substrate 11 side). Specifically, when a wiring pattern of a gate electrode or a source electrode / drain electrode in a TFT array is transferred to a resist film formed on a substrate of a display device, which is a transfer target, a light shielding film pattern of a photomask is transferred. Since the aperture ratio is 50% or more, the amount of exposure light passing through the photomask increases, so that flare is likely to occur due to the return light of the exposure light from the transfer object side. Therefore, the reflectance of the front and back surfaces of the light shielding film 12 of the photomask blank 1 with respect to the exposure wavelength is 10% or less, respectively, and the reflectance of the front surface side of the light shielding film 12 is lower than the reflectance of the back surface side. Thus, the influence of flare can be reduced, and a CD error when a display device is manufactured using a photomask can be prevented.

(C) Further, in the present embodiment, the first reflection suppressing layer 13, the light shielding layer 14, and the second reflection suppressing layer 15 constituting the light shielding film 12 have the respective composition ranges described above, so that O, which lowers the etching rate, In addition, the concentration of N that increases the etching rate can be reduced, and the difference between the etching rates of the respective layers can be suppressed and uniform. Thereby, the cross-sectional shape when the light-shielding film 12 of the photomask blank 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, assuming that the angle between the side surface formed by etching and the transparent substrate 11 is θ, θ can be within a range of 90 ° ± 30 °. In addition, the cross-sectional shape of the mask pattern is made nearly vertical, and the first reflection suppression layer 13 is left unetched, or the first reflection suppression layer 13 and the second reflection suppression layer 15 are etched (so-called undercut) and side-etched. Can be suppressed. As a result, CD uniformity in the mask pattern (light shielding film pattern) can be improved, and a highly accurate mask pattern of 100 nm or less can be formed.

(D) In the present embodiment, the light-shielding film 12 has the same etching rate as 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 verticality of the cross-sectional shape can be stably ensured regardless of the length, the concentration of the etching solution, and the temperature of the etching solution. For example, when the just-etching time of the light-shielding film 12 is T, even when the etching time is 1.5 × T and the over-etching is performed, the same verticality as when the etching time is T can be obtained. . 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 overetching is performed by setting the etching time to 1.5 × T is 10 ° or less. Can be Similarly, when the concentration of the etching solution is increased and the concentration of the etching solution is decreased, the difference between the angles formed by the cross sections of the light-shielding film patterns can be made 10 ° or less. Similarly, when the temperature of the etching solution is increased (for example, 42 ° C.) and when the temperature of the etching solution is decreased (for example, 23 ° C., which is room temperature), the etching rate increases as the temperature of the etching solution increases. In addition, the difference in angle between the cross sections of the light-shielding film patterns can be made 10 ° or less. The just etching time indicates an etching time from when the light shielding film 12 is etched in the thickness direction until the surface of the transparent substrate 11 starts to be exposed.

(E) In the light-shielding film 12, the first reflection suppression layer 13 and the second reflection suppression layer 15 are chromium-based materials containing chromium, oxygen, and nitrogen. ７５75 at%, O at 15Ｃｒ35 at%, N at 10２５25 at%, and the second antireflection layer 15 contains 50５０75 at% Cr and 20〜40 at% O. , N at a content of 5 to 20 atomic%.

  By further reducing the O content in the first reflection suppression layer 13 and the second reflection suppression layer 15, an excessive increase in the etching rate due to the inclusion of O in these layers can be suppressed. Therefore, the content of carbon (C) blended in the light shielding layer 14 for the purpose of making the etching rates 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 uniform is reduced. Alternatively, the light-shielding layer 14 can be made not containing carbon without containing C. As a result, the Cr content in the light-shielding layer 14 can be increased, and the optical density (OD) can be kept high.

  On the other hand, in the first reflection suppression layer 13 and the second reflection suppression 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 these layers. Therefore, it is possible to reduce the content of N contained in the light shielding layer 14 for the purpose of making the etching rates 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 uniform. it can. As a result, the Cr content in the light-shielding layer 14 can be increased, and the optical density (OD) can be kept high.

(F) In the first antireflection layer 13 and the second antireflection layer 15, the composition of at least one element of O and N changes continuously or stepwise in the film thickness direction. It is preferable to have a region. By changing the composition of each layer of the first antireflection layer 13 and the second antireflection layer 15, an average of O or N in each layer can be locally introduced while locally introducing a region having a high O or N content in each layer. Content rate can be kept low. Thereby, the reflectance on the front side and the back side of the photomask blank 1 can be kept low.

  Further, in each 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 increases, the etching rate increases excessively, and when the N content increases, the etching rate increases. Although the etching rate may be excessively increased, the difference in the etching rate of each layer due to the inclusion of these elements can be suppressed by reducing the content of O or N. That is, it is possible to suppress the difference in the etching rate between the first reflection suppression layer 13 and the second reflection suppression layer 15 and the light shielding layer 14. As a result, in order to make the etching rates 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 equal to each other, N or carbon contained in the light shielding layer 14 is reduced, 14 can be made carbon-free without carbon. As a result, the Cr content in the light-shielding layer 14 can be increased, and the optical density (OD) can be kept high.

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

(H) The second reflection suppressing layer 15 preferably has a region in which the N content decreases toward the light-shielding layer 14 in the thickness direction. Thereby, in the second reflection suppressing layer 15, the N content at the interface with the light shielding layer 14 is locally reduced while the average N content in the film thickness direction is maintained to some extent. As a result, erosion due to excessive etching at the interface between the second reflection suppressing layer 15 and the light shielding layer 14 can be suppressed.

(I) The first antireflection layer 13 preferably has a region where the O content increases and the N content decreases toward the transparent substrate 11 in the film thickness direction. In the first reflection suppressing layer 13, the etching rate can be gradually reduced toward the transparent substrate 11 by increasing the O content and decreasing the N content toward the transparent substrate 11 in the film thickness direction. . Thereby, 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.

(J) The second reflection suppressing layer 15 is preferably configured to have a higher O content than the first reflection suppressing layer 13. Specifically, the O content of the second antireflection layer 15 is preferably higher than that of the first antireflection layer 13 by 5 atomic% or more, more preferably 10 atomic% or more. Further, it is preferable that the first reflection suppressing layer 13 is configured to have a higher N content than the second reflection suppressing layer 15. Specifically, the N content of the first antireflection layer 13 is preferably higher than that of the second antireflection layer 15 by 5 atomic% or more, more preferably 10 atomic% or more. According to the study of the present inventors, when the first reflection suppressing layer 13 and the second reflection suppressing layer 15 are formed of the same material, the reflectance on the front surface side is higher than that on the rear surface side, despite the same composition. It turns out that it tends to be high. Then, when the composition ratio (O content, N content) of each layer of the first reflection suppression layer 13 and the second reflection suppression layer 15 was further examined, the composition ratio of the first reflection suppression layer 13 and the second reflection suppression layer 15 was determined. It has been found that by setting the (O content, N content) as described above, the reflectance on the rear surface side can be made equal to or lower than that on the front surface side. By changing the composition ratio (O content, N content) of each layer in this way, the reflectance on the front and back surfaces can be controlled.

(K) According to the present embodiment, the light-shielding layer 14 is preferably a chromium-based material in a bonded state (chemical state) containing chromium (Cr) and dichromium nitride (Cr ₂ N). By forming the light-shielding layer 14 from a chromium-based material in a bonded state (chemical state) containing Cr and Cr ₂ N, excessive progress of the etching rate when the light-shielding layer 14 contains a predetermined amount of N can be suppressed, The cross-sectional shape of the light-shielding film pattern can be made nearly vertical.

(L) According to the present embodiment, the first reflection suppression layer 13 and the second reflection suppression layer 15 are made of chromium mononitride (CrN), chromium (III) oxide (Cr ₂ O ₃ ), and chromium oxide (VI). It is preferable to use a chromium-based material in a bonded state (chemical state) containing (CrO ₃ ). Since the first antireflection layer 13 and the second antireflection layer 15 contain a plurality of chromium oxides of Cr ₂ O ₃ and CrO ₃ , the reflectance of the front and back surfaces of the light shielding film 12 can be effectively reduced. it can. In addition, since the first reflection suppression layer 13 and the second reflection suppression layer 15 contain chromium nitride of CrN, it is possible to suppress the above-described excessive decrease in the etching rate due to chromium oxide. The shape can be made nearly vertical.

(M) According to the present embodiment, the first reflection suppression layer 13 and the second reflection suppression layer 15 are formed by using a sputtering target containing Cr and a sputtering gas containing an oxygen-based gas, a nitrogen-based gas, and a rare gas. 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. Then, as a film forming condition of the reactive sputtering, a flow rate at which the flow rate of the reactive gas included in the sputtering gas is set to the metal mode is selected. Thereby, 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 easily adjusted to the above composition range, and the reflectance of the front and back surfaces of the light shielding film 12 can be effectively reduced. The cross-sectional shape of the light-shielding film pattern when the light-shielding film 12 is patterned can be made closer to the vertical while the light-shielding film 12 is patterned.

(N) When forming each of the first reflection suppression layer 13 and the second reflection suppression layer 15 by reactive sputtering, it is preferable to use oxygen (O ₂ gas) as an oxygen-based gas. According to the O ₂ gas, the oxidizing power is higher than that of other oxygen-based gases. Therefore, even when the metal mode is selected for film formation, each layer can be surely adjusted to the above composition range. This makes it possible to make the cross-sectional shape of the light-shielding film pattern when the light-shielding film 12 is patterned closer to vertical while effectively reducing the reflectance on the front and back surfaces of the light-shielding film 12.

(O) According to the photomask blank 1 of the present embodiment, since the reflectance on the front side is low, a resist film is provided on the light-shielding film 12, and when a resist pattern is formed by the drawing / developing process, the drawing light The reflection on the surface of the light shielding film 12 can be reduced. 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 therefrom can be improved.

(P) In the photomask manufactured from the photomask blank 1 of the present embodiment, the light-shielding film pattern has a high precision and the reflectance of the front and back surfaces of the light-shielding film pattern is reduced, so that the photomask to the transfer target is reduced. During pattern transfer, high transfer characteristics can be obtained.

(Q) In the present embodiment, even when the photomask blank 1 is enlarged using a rectangular substrate having a short side length of 850 mm to 1620 mm as the transparent substrate 11, Since the light-shielding film 12 is configured to have 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 kept high.

(R) Further, the photomask of the present embodiment has a reflectance of 10% or less, preferably 7.5% or less, on both the front and back surfaces of the light-shielding film pattern with respect to light selected from the wavelength range of 300 nm to 550 nm. Since it can be preferably 5% or less, even when the exposure light intensity is increased, for example, when exposing composite light including i-line, h-line and g-line, it is high with respect to the transfer target. An accurate transfer pattern can be formed. Further, in the vicinity of the superimposition of the transfer target (for example, the display panel), it is possible to prevent display unevenness caused by irradiating exposure light more than expected. The exposure light may be a composite light including a plurality of wavelengths selected from a wavelength range of 300 nm to 550 nm, or a monochromatic light selected by cutting a wavelength range from a wavelength range of 300 nm to 550 nm with a filter or the like. For example, there are composite light including a j-line having a wavelength of 313 nm, an i-line having a wavelength of 365 nm, an h-line having a wavelength of 405 nm, and a g-line having a wavelength of 436 nm, and monochromatic light having an i-line.

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

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 to this. For example, a photomask blank in which a semi-transmissive film having an optical density lower than that of the light-shielding film 12 is provided between the transparent substrate and the light-shielding film 12 may be used. The photomask blank can be used as a photomask blank for a gray-tone mask or a gradation mask that has an effect of reducing the number of photomasks used in manufacturing a display device. The mask pattern in this gray-tone mask or gradation mask is a semi-transparent film pattern and / or a light-shielding film pattern.
Further, instead of the semi-transparent film, a photomask blank in which a phase shift film for shifting the phase of transmitted light is provided between the transparent substrate 11 and the light-shielding film 12 may be used. This photomask blank can be used as a phase shift mask having a high pattern resolution effect by the phase shift effect. The mask pattern in this phase shift mask is a phase shift film pattern, or a phase shift film pattern and a light shielding film pattern.
For the above-mentioned semi-transmissive film and phase shift film, a material having etching selectivity with respect to a chromium-based material which is a material forming the light shielding film 12 is suitable. As such a material, a metal silicide-based material containing molybdenum (Mo), zirconium (Zr), titanium (Ti), tantalum (Ta) and silicon (Si) can be used. Materials containing at least one of carbon and fluorine are suitable. For example, metal silicide such as MoSi, ZrSi, TiSi, TaSi, etc., oxide of metal silicide, nitride of metal silicide, oxynitride of metal silicide, carbonitride of metal silicide, oxycarbide of metal silicide, carbonization of metal silicide Oxynitrides are suitable. Incidentally, these semi-transparent films and phase shift films may be laminated films composed of the above-mentioned films mentioned as the functional films.
The transmittance of the above-mentioned semi-transmissive film and phase shift film with respect to the exposure wavelength of the exposure light can be appropriately adjusted within the range of 1 to 80%. In the combination with the light-shielding film of the present invention, the transmittance of the above-described semi-transparent film and phase shift film with respect to the exposure wavelength of the exposure light is preferably 20 to 80%. A laminated film in which a semi-transparent film and a light-shielding film are formed by selecting a semi-transparent film and a phase shift film having a transmittance of 20 to 80% with respect to the exposure wavelength of the exposure light and combining the light-shielding film of the present invention. Alternatively, the reflectance of the back surface of the laminated film in which the phase shift film and the light shielding film are formed with respect to the exposure wavelength can be set to 40% or less, more preferably 30% or less.

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

  In the above embodiment, an etching mask film made of a material having an etching selectivity with the light shielding film 12 may be formed on the light shielding film 12.

In the above-described embodiment, an etching stopper film made of 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 are made of a material having an etching selectivity with respect to a chromium-based material constituting the light shielding film 12. Examples of such a material include molybdenum (Mo), zirconium (Zr), titanium (Ti), metal silicide-based materials containing tantalum (Ta) and silicon (Si), Si, SiO, SiO ₂ , SiON, and Si. silicon-based material ₃ N ₄ and the like.

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

<Example 1>
(Preparation of photomask blank)
In this example, the first antireflection layer, the light-shielding layer and the first light-shielding layer were formed on a transparent substrate having a size of 1220 mm × 1400 mm as shown in FIG. A photomask blank having a light-shielding film was manufactured by laminating two antireflection layers.

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

Conditions for forming the light-shielding layer, the sputter target and Cr sputter target, the flow rate of the reactive gas, so that the metal mode, the flow rate of nitrogen _{(N 2)} gas 1～60Sccm, argon (Ar) gas flow rate Was selected from the range of 60 to 200 sccm, the target applied power was set in the range of 3.0 to 7.0 kW, and the applied voltage was set in the range of 370 to 380 V. In addition, the substrate transfer speed at the time of forming the light shielding layer was set to 200 mm / min.

Conditions for forming the second antireflection layer, a sputter target and Cr sputter target, the flow rate of the reactive gas, so that the metal mode, oxygen _{(O 2)} 8~45sccm the flow rate of the gas, nitrogen _{(N 2} ) The gas flow rate is selected from the range of 30 to 60 sccm, the argon (Ar) gas flow rate is selected from the range of 60 to 150 sccm, the target applied power is set to 2.0 to 6.0 kW, and the target applied voltage is set to the range of 420 to 430 V. Set. In addition, the substrate transfer speed at the time of forming the second reflection suppressing layer was set to 300 mm / min.

  When the composition in the thickness direction of the obtained light shielding film of the photomask blank was measured by X-ray photoelectron spectroscopy (XPS), it was confirmed that each layer in the light shielding film had the composition distribution shown in FIG. FIG. 2 is a diagram illustrating a composition analysis result in the film thickness direction of the photomask blank of Example 1, in which the horizontal axis indicates sputtering time, and the vertical axis indicates element content [atomic%]. The sputtering time indicates the depth from the surface of the light shielding film.

In FIG. 2, the region from the surface to a depth of about 5 min (min) is the surface native oxide layer, and the region from the depth of about 5 min (min) to a depth of about 16 min (min) is the second antireflection layer. A region from a depth of about 16 min (min) to a depth of about 40 min (min) is a transition layer, and a region from a depth of about 40 min (min) to a depth of about 97 min (min) is a light-shielding layer. The region from about 97 min (min) to about 124 min (min) in depth is the transition layer, the area from about 124 min (min) to about 132 min (min) is the first antireflection layer, A region from a depth of about 132 min (minute) is a transparent substrate.
The thickness of the light-shielding film measured by the film thickness meter was 198 nm, and the thicknesses of the surface natural oxide layer, the second antireflection layer, the transition layer, the light-shielding layer, the transition layer, and the first antireflection layer were as follows: The surface natural oxide layer was about 4 nm, the second antireflection layer was about 21 nm, the transition layer was about 35 nm, the light shielding layer was about 88 nm, the transition layer was about 39 nm, and the first reflection suppression layer was about 11 nm.

  As shown in FIG. 2, the first reflection suppressing layer is a CrON film, and contains 55.4 atomic% of Cr, 20.8 atomic% of N, and 23.8 atomic% of O. The contents of these elements are measured at the portion where N peaks in the first antireflection layer (sputtering time is 123 min (minute)). The first antireflection layer has a gradient composition as shown in FIG. 2 and has a portion where the O content increases and the N content decreases toward the transparent substrate in the film thickness direction. In the first antireflection layer, the average content of each element in the thickness direction was 57 at% for Cr, 18 at% for N, and 25 at% for O.

  The light shielding layer is a CrN film and contains 92.0 atomic% of Cr and 8.0 atomic% of N. The contents of these elements are measured at the center of the light-shielding layer in the thickness direction (a region where the sputtering time is 69 min (minute)). In the light-shielding layer, the average content of each element in the film thickness direction was 91 atomic% for Cr and 9 atomic% for N.

  The second anti-reflection layer is a CrON film and contains 50.7 at% of Cr, 12.2 at% of N, and 37.1 at% of O. The contents of these elements are measured at the center of the region where O is increasing (the region where the sputtering time is 16 min (minute)) in the second reflection suppressing layer. The second antireflection layer has a gradient composition as shown in FIG. 2 and has a portion where the O content increases and the N content decreases toward the light-shielding layer side in the film thickness direction. In the second antireflection layer, the average content of each element in the thickness direction was 52 atomic% for Cr, 17 atomic% for N, and 31 atomic% for O. On the surface of the second antireflection layer, a surface natural oxide layer is formed by exposure to the atmosphere, and this layer is oxidized or carbonized, so that the O content and the C content are detected to be high. it is conceivable that.

In addition, a spectrum analysis was performed on the bonding state (chemical state) of each of the first reflection suppressing layer, the light shielding layer, and the second reflection suppressing layer constituting the light shielding film based on the XPS measurement result. As a result, the first antireflection layer and the second antireflection layer comprises chromium nitride (CrN) and chromium oxide _{(III) (Cr 2 O 3} ) and chromium oxide (VI) (CrO _3), chromium and oxygen And a chromium-based material (chromium compound) containing nitrogen. The light-shielding layer was a chromium-based material (chromium compound) containing chromium (Cr) and dichromium nitride (Cr ₂ N), and containing chromium and nitrogen.

(Evaluation of photomask blank)
For the photomask blank of Example 1, the optical density of the light-shielding film and the reflectance of the front and back surfaces of the light-shielding film were evaluated by the following methods.

  The optical density of the light-shielding film of the photomask blank of Example 1 was measured with a spectrophotometer (“SolidSpec-3700” manufactured by Shimadzu Corporation). 5.0. The reflectance of the front and back surfaces of the light-shielding film was measured with a spectrophotometer (“SolidSpec-3700” manufactured by Shimadzu Corporation). Specifically, the reflectance of the light-shielding film on the side of the second reflection suppressing layer (front surface reflectance) and the reflectance of the light-shielding film on the side of the transparent substrate (rear surface reflectance) were measured with a spectrophotometer. As a result, a reflectance spectrum as shown in FIG. 3 was obtained. FIG. 3 shows the reflectance spectra of the front and back surfaces of the photomask blank of Example 1, where the horizontal axis represents the wavelength [nm] and the vertical axis represents the reflectance [%]. As shown in FIG. 3, in the photomask blank of Example 1, the bottom peak wavelength of the reflectance spectrum on the front and back surfaces can be set to around 436 nm, and the reflectance can be greatly reduced for light of a wide wavelength range. confirmed. Specifically, at a wavelength of 365 nm to 436 nm, the 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), and the backside reflectance of the light-shielding film is 7.5% or less (6.2% (wavelength 365 nm), 4.7% (wavelength 405 nm), 4.8% (wavelength). 436 nm)). At wavelengths of 365 nm to 436 nm, the reflectance of the front and back surfaces of the light-shielding film can be reduced to 10% or less. In particular, with respect to the reflectance at 436 nm, the surface reflectance is 0.3% and the back surface reflectance is 4.8%. It was confirmed that it was possible.

(Evaluation of light-shielding film pattern)
Using the photomask blank of Example 1, a light-shielding film pattern was formed on a transparent substrate. Specifically, after a novolak-based positive resist film was formed on the light-shielding film on the transparent substrate, laser resist drawing (wavelength 413 nm) and development were performed to form a resist pattern. Thereafter, wet etching was performed with a chromium etching solution using the resist pattern as a mask to form a light-shielding film pattern on the transparent substrate. The light-shielding film pattern was evaluated by forming a 1.9 μm line-and-space pattern and observing the cross-sectional shape of the light-shielding film pattern with a scanning electron microscope (SEM). As a result, as shown in FIG. 4, it was confirmed that the cross-sectional shape was made almost vertical. FIG. 4 is a diagram for explaining the perpendicularity of the cross-sectional shape of the light-shielding film pattern by wet etching with respect to the photomask blank of Example 1, and the etching time is set based on the just etching time (JET) (100%). Are 110%, 130%, and 150%, respectively. In FIG. 4, a light-shielding film pattern and a resist film pattern are laminated on a transparent substrate, and it has been confirmed that the side surface of the light-shielding film pattern forms an angle of 70 ° with the transparent substrate when the JET is 100%. . This angle is in the range of 60 ° to 80 ° even when the etching time is 110%, 130%, and 150% of JET, and the cross-sectional shape of the light-shielding film pattern does not depend on the etching time. It was confirmed that it could be formed vertically stably.

  As in Example 1 above, for the light shielding film of the photomask blank, the first reflection suppressing layer, the light shielding layer, and the second reflection suppressing layer are laminated from the transparent substrate side, and each layer has a predetermined composition. As a result, the reflectance of the front and back surfaces was reduced in a wide wavelength range, and the light-shielding film pattern formed by wet etching could be formed to have a vertical cross-sectional shape.

(Preparation of photomask)
Next, a photomask was manufactured using the photomask blank of Example 1.
First, a novolak-based positive resist was formed on the light-shielding film of the photomask blank. Then, using a laser drawing apparatus, a pattern of a circuit pattern for a TFT panel is drawn on this resist film, and further developed and rinsed to form a predetermined resist pattern (the minimum line width of the above-mentioned circuit pattern is 0.75 μm).
After that, using the 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 stripped with a resist stripping solution, so that a light-shielding film pattern (mask pattern) is formed on the transparent substrate. The formed photomask was obtained.
The CD uniformity of the light-shielding film pattern of the photomask was measured by “SIR8000” manufactured by Seiko Instruments Nanotechnology. The CD uniformity was measured at 11 × 11 points in a 1100 mm × 1300 mm area excluding the peripheral area 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 manufactured in Example 1 is set on a mask stage of an exposure apparatus, and pattern transfer is performed on a transfer target having a resist film formed on a substrate for a display device (TFT) to manufacture a TFT array. did. As exposure light, composite light having a wavelength of 300 nm or more and 550 nm or less including an i-line having a wavelength of 365 nm, an h-line having a wavelength of 405 nm, and a g-line having a wavelength of 436 nm was used.
A TFT-LCD panel was manufactured by combining the manufactured TFT array with a color filter, a polarizing plate, and a backlight. As a result, a TFT-LCD panel having no display unevenness was obtained.

<Example 2>
(Preparation of photomask blank)
In this example, a photomask blank was manufactured in the same manner as in Example 1, except that a semi-transparent film was formed between the transparent substrate and the light-shielding film. Specifically, after forming a semi-transparent film on a transparent substrate of 1220 mm × 1400 mm, the first reflection suppressing layer, the light shielding layer, and the second reflection suppressing layer are laminated under the same conditions as in Example 1. Example 2 A photomask blank of Example 2 was manufactured.
In forming the semi-transparent film, a molybdenum silicide nitride film (MoSiN) was formed by reactive sputtering using a mixed gas of an argon (Ar) gas and a nitrogen (N ₂ ) gas with a sputtering target of a MoSi sputtering target. The composition ratio and the film thickness of this semi-translucent film were appropriately adjusted so that the transmittance at i-line (365 nm) was 40%.
Next, a photomask blank of Example 2 was manufactured by forming a light-shielding film composed of a first antireflection layer, a light-shielding layer, and a second antireflection layer on the above-mentioned semi-translucent film in the same manner as in Example 1. .

(Evaluation of photomask blank)
With respect to the photomask blank of Example 2, the optical density and the reflectance of the front and back surfaces of the laminated film including the semi-transparent film and the light-shielding film were evaluated by the same method as in Example 1 described above. As a result, the optical density of the laminated film at the g-line (wavelength: 436 nm), which is the wavelength range of the exposure light, was 5.0 or more. In the wavelength range of 365 nm to 436 nm, the reflectance (surface reflectance) of the laminated film on the light-shielding film side is 10.0% or less (7.7% (wavelength: 365 nm), 1.8% (wavelength: 405 nm), 1.0%). 1% (wavelength 413 nm) and 0.3% (wavelength 436 nm), and the reflectance on the semi-transparent film side (backside reflectance) is 30.0% or less (27.4% (wavelength 365 nm), 22 0.5% (wavelength 405 nm) and 20.1% (wavelength 436 nm).

(Preparation of photomask)
Next, a photomask was manufactured using the photomask blank of Example 2. This photomask includes a semi-transparent film pattern on a transparent substrate, and a light-shielding film pattern formed on the semi-transparent film pattern, and includes a transfer pattern including a light-transmitting part, a light-shielding part, and a semi-light-transmitting part. The photomask of Example 2 was manufactured by the method for manufacturing a gray-tone mask described in Japanese Patent No. 4934236. The CD uniformity of the semi-transparent film pattern and the light-shielding film pattern of the obtained photomask was good.

(Production of LCD panel)
An LCD panel was manufactured in the same manner as in Example 1 using the photomask manufactured in Example 2. As a result, a TFT-LCD panel having no display unevenness was obtained. The method of manufacturing the photomask of Example 2 can be manufactured by the method of manufacturing a photomask described in Japanese Patent No. 5605917. The semi-transparent film pattern and the light shielding of the photomask obtained by this method can be manufactured. The CD uniformity of the film pattern is also improved. Then, a TFT-LCD panel with less display unevenness can be obtained.

<Comparative Example 1>
As a comparative example, a photomask blank including a light-shielding film was manufactured by laminating a first antireflection layer, a light-shielding layer, and a second antireflection layer on a transparent substrate having a substrate size of 1220 mm x 1400 mm.

The film formation conditions of the first reflection suppression layer are such that the sputtering target is a Cr sputtering target, the flow rate of the reactive gas is 150 to 300 sccm, and the flow rate of the oxygen (O ₂ ) gas is nitrogen (N _2). ) The flow rate of the gas is selected from the range of 150 to 300 sccm, the flow rate of the methane (CH ₄ ) gas is selected from the range of 5 to 15 sccm, and the flow rate of the argon (Ar) gas is selected from the range of 100 to 150 sccm. It was set in the range of 0.0 kW. In addition, the substrate transfer speed at the time of forming the first reflection suppressing layer was set to 200 mm / min, and the film was formed three times.

Conditions for forming the light-shielding layer, the sputter target and Cr sputter target, the flow rate of the reactive gas, so that the metal mode, the flow rate of nitrogen _{(N 2)} gas 1～60Sccm, argon (Ar) gas flow rate Was selected from the range of 60 to 200 sccm, and the target applied power was set in the range of 5.0 to 8.0 kW. In addition, the substrate transfer speed at the time of forming the light shielding layer was set to 200 mm / min.

The film formation conditions of the second reflection suppressing layer are such that the sputtering target is a Cr sputtering target, the flow rate of the reactive gas is 150 to 300, and the flow rate of the oxygen (O ₂ ) gas is nitrogen (N _2). ) The flow rate of the gas is selected from the range of 150 to 300 sccm, the flow rate of the methane (CH ₄ ) gas is selected from the range of 5 to 15 sccm, and the flow rate of the argon (Ar) gas is selected from the range of 100 to 150 sccm. It was set in the range of 0.0 kW. In addition, the substrate conveyance speed at the time of film-forming of a 2nd reflection suppression layer was 200 mm / min, and film-forming was performed 3 times.
The thickness of the light-shielding film measured by a film thickness meter was 206 nm. The thickness of each of the surface natural oxide layer, the second antireflection layer, the light-shielding layer, and the first antireflection layer is about 3 nm, the second antireflection layer is about 51 nm, the lightproof layer is about 101 nm, and the first antireflection layer. Was about 51 nm. Further, a transition layer in which the composition of each element is continuously inclined was formed between the second reflection suppressing layer and the light blocking layer, and between the light blocking layer and the first reflection suppressing layer.

With respect to the light-shielding film of the photomask blank of Comparative Example 1, the contents of the elements contained in the respective layers were measured, and the results were as follows. The content of each layer shown below indicates the average content of each element in the thickness direction.
The first anti-reflection layer is a CrON film and contains 45 atomic% of Cr, 3 atomic% of N, and 52 atomic% of O.
The light-shielding layer is a CrN film and contains 78 atomic% of Cr and 22 atomic% of N.
The second anti-reflection layer is a CrON film and contains 45 atomic% of Cr, 3 atomic% of N, and 52 atomic% of O.

As in Example 1 described above, the optical density of the light-shielding film and the reflectance of the front and back surfaces of the light-shielding film were measured for the photomask blank of Comparative Example 1. As a result, the optical density of the light-shielding film was 3.5% at the g-line (wavelength 436 nm) and 4.5% at the i-line (wavelength 365 nm), which are the wavelength regions of the exposure light. Further, at a wavelength of 365 nm to 436 nm, the surface reflectance of the light-shielding film is 5.0% or less (4.5% (wavelength 365 nm), 4.0% (wavelength 405 nm), 3.5% (wavelength 436 nm)), The back surface reflectance of the light-shielding film was 7.5% or less (5.5% (wavelength: 365 nm), 6.5% (wavelength: 405 nm), 7.5% (wavelength: 436 nm)).
Further, the light-shielding film pattern was evaluated in the same manner as in Example 1. As a result, the side surface of the light-shielding film pattern had a tapered shape near the transparent substrate and an inversely tapered shape near the resist film, resulting in a very poor cross-sectional shape. In addition, it was confirmed that the angle between the transparent substrate and JET at 100% was 150 °.

  Next, using the photomask blank of Comparative Example 1, a photomask was manufactured in the same manner as in Example 1. The CD uniformity of the light-shielding film pattern of the obtained photomask was measured to be 200 nm, which was a bad result. As described above, in the mask blank of Comparative Example 1, the reflectance on the front and back surfaces could be reduced, but a highly accurate mask pattern could not be formed.

  As described above, in the light-shielding film of the photomask blank, each of the first antireflection layer, the light-shielding layer, and the second antireflection layer is formed of a material having a predetermined composition. By setting the reflectivity of each of the front and back surfaces to be 10% or less and the optical density to be 3.0 or more and forming a photomask blank, CD uniformity is good when a photomask is manufactured by etching. And a highly accurate mask pattern can be obtained. According to such a photomask, a display device with less display unevenness can be manufactured.

DESCRIPTION OF SYMBOLS 1 Photomask blank 11 Transparent substrate 12 Light shielding film 13 First reflection suppressing layer 14 Light shielding layer 15 Second reflection suppressing layer

Claims (22)

A photomask blank used when manufacturing a photomask for manufacturing a display device,
A transparent substrate made of a material substantially transparent to exposure light,
Provided on the transparent substrate, a light-shielding film made of a material substantially opaque to the exposure light,
The light shielding film includes a first reflection suppression layer, a light shielding layer, and a second reflection suppression layer from the transparent substrate side,
The first reflection suppressing layer is a chromium-based material containing chromium, oxygen, and nitrogen, and has a chromium content of 25 to 75 atomic%, an oxygen content of 15 to 45 atomic%, and a nitrogen content. Has a composition of 10 to 30 atomic%,
The light-shielding layer is a chromium-based material containing chromium and nitrogen, and has a composition with a chromium content of 70 to 95 atomic% and a nitrogen content of 5 to 30 atomic%,
The second reflection suppressing layer is a chromium-based material containing chromium, oxygen, and nitrogen, and has a chromium content of 30 to 75 atomic%, an oxygen content of 20 to 50 atomic%, and a nitrogen content. Has a composition of 5 to 20 atomic%,
The first antireflection layer, the light-shielding layer, and the light-shielding film have a reflectance of 10% or less with respect to an exposure wavelength of the exposure light, and an optical density of 3.0 or more. And a film thickness of the second reflection suppressing layer is set. The first antireflection layer has a chromium content of 50 to 75 atomic%, an oxygen content of 15 to 35 atomic%, and a nitrogen content of 10 to 25 atomic%.
2. The second reflection suppressing layer according to claim 1, wherein the chromium content is 50 to 75 atomic%, the oxygen content is 20 to 40 atomic%, and the nitrogen content is 5 to 20 atomic%. 2. The photomask blank according to 1.   The first antireflection layer and the second antireflection layer each have a region in which the content of at least one of oxygen and nitrogen changes in composition continuously or stepwise along the film thickness direction. The photomask blank according to claim 1, wherein:   The photomask blank according to any one of claims 1 to 3, wherein the second reflection suppressing layer has a region where the oxygen content increases toward the light-shielding layer in the thickness direction. .   The photomask blank according to any one of claims 1 to 4, wherein the second reflection suppressing layer has a region in which the nitrogen content decreases toward the light-shielding layer in the thickness direction. .   The said 1st reflection suppression layer has the area | region where oxygen content increases and nitrogen content falls toward the said transparent substrate of a film thickness direction, The Claim 1 characterized by the above-mentioned. A photomask blank according to the item.   The photomask blank according to any one of claims 1 to 6, wherein the second antireflection layer has a higher oxygen content than the first antireflection layer. .   8. The photomask blank according to claim 1, wherein the first reflection suppression layer is configured to have a higher nitrogen content than the second reflection suppression layer. 9. . The light-shielding layer, the photomask blank according to any one of claims 1-8, characterized in that it comprises chromium (Cr) and nitride dichromate (Cr 2 _N). The first antireflection layer and the second antireflection layer, characterized in that it comprises a chromium nitride (CrN) and chromium oxide _{(III) (Cr 2 O 3} ) and chromium oxide (VI) (CrO ₃₎ The photomask blank according to claim 1.   The photomask blank according to any one of claims 1 to 10, wherein the transparent substrate is a rectangular substrate, and a length of a short side of the substrate is 850 mm or more and 1620 mm or less.   The translucent film according to claim 1, further comprising a semi-transmissive film having an optical density lower than an optical density of the light-shielding film, between the transparent substrate and the light-shielding film. Photomask blank.   The photomask blank according to any one of claims 1 to 11, further comprising a phase shift film between the transparent substrate and the light shielding film. A photomask for manufacturing a display device is manufactured, in which a light-shielding film made of a material substantially opaque to exposure light is formed by a sputtering method on a transparent substrate made of a material substantially transparent to exposure light. It is a method for manufacturing a photomask blank used at the time,
On the transparent substrate, a sputtering target containing chromium, an oxygen-based gas, a reactive gas containing a nitrogen-based gas, and a sputtering gas containing a rare gas, by reactive sputtering using chromium, oxygen, and nitrogen. A first antireflection layer comprising a chromium-based material containing 25 to 75 atomic% of chromium, 15 to 45 atomic% of oxygen, and 10 to 30 atomic% of nitrogen. Forming a;
On the first reflection suppressing layer, chromium containing chromium and nitrogen by reactive sputtering using a sputter target containing chromium, and a sputtering gas containing a reactive gas containing a nitrogen-based gas and a rare gas. Forming a light-shielding layer which is a system material and has a composition in which the content of chromium is 70 to 95 atomic% and the content of nitrogen is 5 to 30 atomic%;
On the light-shielding layer, chromium, oxygen, and nitrogen were formed by reactive sputtering using a sputtering target containing chromium, an oxygen-based gas, a reactive gas containing a nitrogen-based gas, and a sputtering gas containing a rare gas. A second antireflection layer having a chromium content of 30 to 75 atomic%, an oxygen content of 20 to 50 atomic%, and a nitrogen content of 5 to 20 atomic%. Forming, and
In the reactive sputtering, the flow rate of the reactive gas included in the sputtering gas is selected to be a flow rate in the metal mode, and the reflectance of the front and back surfaces of the light shielding film with respect to the exposure wavelength of the exposure light is 10% or less. A thickness of the first antireflection layer, the light-shielding layer, and the second antireflection layer so as to have an optical density of 3.0 or more. . Manufacturing method of a photomask blank according to claim 14, wherein the oxygen-containing gas is oxygen gas (O _2).   The first antireflection layer, the light-shielding layer, and the second antireflection layer are formed using an in-line sputtering apparatus that forms the light-shielding film while the transparent substrate moves relative to the sputter target. The method for manufacturing a photomask blank according to claim 14 or 15, wherein   The semi-transmissive film having an optical density lower than the optical density of the light shielding film is formed between the transparent substrate and the light shielding film, according to any one of claims 14 to 16, A method for manufacturing a photomask blank.   The method according to any one of claims 14 to 16, wherein a phase shift film is formed between the transparent substrate and the light shielding film. A step of preparing the photomask blank according to any one of claims 1 to 11,
Forming a resist film on the light shielding film, forming a light shielding film pattern on the transparent substrate by etching the light shielding film using a resist pattern formed from the resist film as a mask,
A method for manufacturing a photomask, comprising: Preparing the photomask blank according to claim 12,
Forming a resist film on the light shielding film, forming a light shielding film pattern on the transparent substrate by etching the light shielding film using a resist pattern formed from the resist film as a mask,
Forming a semi-transparent film pattern on the transparent substrate by etching the semi-transparent film using the light-shielding film pattern as a mask,
A method for manufacturing a photomask, comprising: Preparing the photomask blank according to claim 13;
Forming a resist film on the light shielding film, forming a light shielding film pattern on the transparent substrate by etching the light shielding film using a resist pattern formed from the resist film as a mask,
Forming a phase shift film pattern on the transparent substrate by etching the phase shift film using the light shielding film pattern as a mask,
A method for manufacturing a photomask, comprising: A photomask obtained by the method for manufacturing a photomask according to claim 19, mounted on a mask stage of an exposure apparatus, wherein the light-shielding film pattern formed on the photomask, A method for manufacturing a display device, comprising: exposing at least one mask pattern of a semi-transparent film pattern and the phase shift film pattern to a resist formed on a display device substrate.