JP2019020712A - Photomask blank and method for manufacturing the same, method for manufacturing photomask, and method for manufacturing display device - Google Patents

Abstract

To provide a photomask blank having sufficient optical characteristics capable of suppressing display unevenness when a display device is manufactured.SOLUTION: The photomask blank includes a first reflection suppression layer 13, a light-shielding layer 14 and a second reflection suppression layer 15, successively from a transparent substrate 11 side, in which the first reflection suppression layer has a composition comprising chromium having a content percentage of 25 to 75 atom%, oxygen having a content percentage of 15 to 45 atom%, and nitrogen having a content percentage of 10 to 30 atom%; the light-shielding layer has a composition comprising chromium having a content percentage of 70 to 95 atom% and nitrogen having a content percentage of 5 to 30 atom%; and the second reflection suppression layer has a composition comprising chromium having a content percentage of 30 to 75 atom%, oxygen having a content percentage of 20 to 50 atom%, and nitrogen having a content percentage of 5 to 20 atom%. Each of the top surface and the back surface of the light-shielding film shows a reflectance of 10% or less with respect to an exposure wavelength of exposure light. Film thicknesses of the first reflection suppression layer, the light-shielding layer and the second reflection suppression layer are set to give an optical density of 3.0 or more.SELECTED DRAWING: Figure 1

Description

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

  In display devices such as an LCD (Flat Panel Display) such as an LCD (Liquid Crystal Display), the display is rapidly increasing in size, wide viewing angle, high definition, and high speed display. One of the elements necessary 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 electronic circuit for the display device. For this reason, a photomask for manufacturing a display device in which a fine and highly accurate pattern is formed is necessary.

  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 photomask blanks and photomasks, in order to suppress reflection of light when exposed, a reflection suppressing layer is provided on both the front and back sides of the light shielding film. The photomask blank is, for example, first in order from the 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 the light shielding film of the photomask blank by wet etching or the like to form a predetermined mask pattern.

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

Korean Registered Patent No. 10-1473163

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

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

  In addition to the demand for higher definition and higher speed display of display devices, photomasks for manufacturing display devices have been increasing in substrate size. In recent years, a rectangular with a short side length of 850 mm or more has been developed. An ultra-large photomask using a shape substrate is used for manufacturing a display device. The above-mentioned large photomask having a short side length of 850 mm or more includes 850 mm × 1200 mm size for G7, 1220 mm × 1400 mm size for G8, and 1620 mm × 1780 mm size for G10. A high-precision mask pattern of 100 nm or less is required 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 10% or less with respect to the exposure wavelength, and It was not possible to satisfy the requirement that the CD uniformity of the mask pattern in a photomask manufactured using a mask blank be 100 nm or less.

  The present invention provides a photomask blank that has a high-accuracy mask pattern when a photomask is manufactured by etching and that has optical characteristics that can suppress display unevenness when a display device is manufactured using the photomask. The purpose is to provide.

(Configuration 1)
A photomask blank used when producing a photomask for manufacturing a display device,
A transparent substrate made of a material substantially transparent to exposure light;
A light-shielding film provided on the transparent substrate and 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 suppression layer is a chromium-based material containing chromium, oxygen, and nitrogen, the chromium content is 25 to 75 atomic%, the oxygen content is 15 to 45 atomic%, and the nitrogen content is Has a composition of 10 to 30 atomic%,
The light shielding layer is a chromium-based material containing chromium and nitrogen, and has a chromium content of 70 to 95 atomic% and a nitrogen content of 5 to 30 atomic%,
The second antireflection layer is a chromium-based material containing chromium, oxygen, and nitrogen, and the chromium content is 30 to 75 atomic%, the oxygen content is 20 to 50 atomic%, and the nitrogen content is Has a composition of 5 to 20 atomic%,
The first antireflection layer, the light shielding layer, the reflectance of the exposure light on the front and back surfaces of the light shielding film with respect to the exposure wavelength of the exposure light is 10% or less and the optical density is 3.0 or more And the film thickness of the said 2nd reflection suppression layer is set, The photomask blank characterized by the above-mentioned.

(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%,
In the configuration 1, 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 described photomask blank.

(Configuration 3)
Each of the first antireflection layer and the second antireflection layer has a region in which the content of at least one element of oxygen and nitrogen changes in composition continuously or stepwise along the film thickness direction. 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 suppression layer has a region in which an oxygen content rate increases toward the light shielding layer side in the film thickness direction.

(Configuration 5)
5. The photomask blank according to claim 1, wherein the second reflection suppression layer has a region where the nitrogen content decreases toward the light shielding layer side in the film thickness direction.

(Configuration 6)
The first reflection suppressing layer has a region in which the content rate of oxygen increases toward the transparent substrate in the film thickness direction and the content rate of nitrogen decreases. The photomask blank described in 1.

(Configuration 7)
The photomask blank according to any one of configurations 1 to 6, wherein the second reflection suppression layer is configured to have a higher oxygen content than the first reflection suppression 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 photomask blank according to any one of Configurations 1 to 8, wherein the light shielding layer includes chromium (Cr) and dichromium nitride (Cr ₂ N).

(Configuration 10)
The first reflection suppression layer and the second reflection suppression layer include chromium mononitride (CrN), 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)
The photo according to any one of configurations 1 to 11, further comprising a semi-transparent film having an optical density lower than that of the light shielding film between the transparent substrate and the light shielding film. Mask blank.

(Configuration 13)
The photomask blank according to any one of Structures 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 produced by forming a light-shielding film made of a material substantially opaque to exposure light on a transparent substrate made of a material substantially transparent to exposure light by a sputtering method. A method of manufacturing a photomask blank used in the process,
On the transparent substrate, chromium, oxygen, and nitrogen are formed by reactive sputtering using a sputtering target containing chromium, a reactive gas containing an oxygen-based gas and a nitrogen-based gas, and a sputtering gas containing a rare gas. A first antireflection layer comprising a chromium-based material having a composition in which the chromium content is 25 to 75 atomic%, the oxygen content is 15 to 45 atomic%, and the nitrogen content is 10 to 30 atomic%. Forming a step;
Chromium containing chromium and nitrogen is formed on the first antireflection layer by reactive sputtering using a sputtering target containing chromium and a sputtering gas containing a reactive gas containing a nitrogen-based gas and a rare gas. A step of forming a light shielding layer having a composition of a chromium content of 70 to 95 atomic% and a nitrogen content of 5 to 30 atomic%,
On the light shielding layer, chromium, oxygen, and nitrogen are formed by reactive sputtering using a sputtering target containing chromium, a reactive gas containing an oxygen-based gas and a nitrogen-based gas, and a sputtering gas containing a rare gas. A second antireflection layer comprising a chromium-based material having a composition of 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 contained in the sputtering gas is selected to be a metal mode, and the reflectance of the exposure light on the front and back surfaces of the light shielding film with respect to the exposure wavelength is 10% or less, respectively. The film thicknesses of the first antireflection layer, the light shielding layer, and the second antireflection layer are formed so that the optical density is 3.0 or more. .

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

(Configuration 16)
The first reflection suppression layer, the light shielding layer, and the second reflection suppression layer are formed using an in-line type sputtering apparatus that forms the light shielding film while the transparent substrate moves relative to the sputtering target. The manufacturing method of the photomask blank of the structure 14 or 15 characterized by performing.

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

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

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

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

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

(Configuration 22)
A photomask obtained by the photomask manufacturing method described in any one of Configurations 19 to 21 is placed on a mask stage of an exposure apparatus, and the light shielding film pattern formed on the photomask, the half A method of manufacturing a display device, comprising: an exposure step of exposing and transferring at least one mask pattern of a light transmissive film pattern and the phase shift film pattern onto 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 an optical characteristic which can suppress a display nonuniformity in the case of manufacture of a display apparatus is obtained.

It is sectional drawing which shows schematic structure of the photomask blank concerning one Embodiment of this invention. It is a figure which shows the compositional analysis result of the film thickness direction in the photomask blank of Example 1. It is a figure which shows the reflectance spectrum of front and back about the photomask blank of Example 1. FIG. It is a figure for demonstrating the characteristic of the cross-sectional shape of the light shielding film pattern of the photomask produced using the photomask blank of Example 1. FIG. It is a schematic diagram for demonstrating the film-forming mode in the case of forming a light shielding film by reactive sputtering.

  Embodiments of the present invention will be specifically described below with reference to the drawings. In addition, the following embodiment is one form at the time of actualizing this invention, Comprising: This invention is not limited within the range. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof may be simplified or omitted.

<Photomask blank>
A photomask blank according to an embodiment of the present invention will be described. The photomask blank of this embodiment is, for example, single-wavelength light selected from a wavelength range of 300 nm to 550 nm, or light having 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)) are used when producing a photomask for manufacturing a display device that exposes composite light. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  FIG. 1 is a cross-sectional view showing a schematic configuration of a photomask blank according to an 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 type photomask blank in which the 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 a light transmitting property. A substrate material having a transmittance with respect to 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, alkali-free glass, and low thermal expansion glass.

  The size of the transparent substrate 11 may be appropriately changed according to the size required for the photomask for manufacturing the display device. For example, as the transparent substrate 11, a transparent substrate 11 which is a rectangular substrate and has a short side length of 330 mm or more and 1620 mm or less can be used. As the transparent substrate 11, for example, the size is 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. A substrate such as 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, a photomask 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 order from the transparent substrate 11 side. In the following description, the transparent substrate 11 side of the photomask blank 1 is described as the back surface side, and the light shielding film 12 side is described as the front surface side.

  The first reflection suppression layer 13 is provided on the light shielding film 12 on the surface of the light shielding layer 14 near the transparent substrate 11, and pattern transfer is performed using a photomask manufactured using the photomask blank 1. In addition, it is arranged on the side close to the exposure light source. When performing exposure processing using a photomask, exposure light is irradiated from the transparent substrate 11 side (back side) of the photomask, and a pattern transfer image is formed on a resist film formed on a display device substrate that is a transfer target. It will be transcribed. At this time, if the exposure light is reflected on the back side of the light-shielding film pattern, it becomes stray light of the mask pattern that is the light-shielding film pattern, resulting in deterioration of the transferred image such as formation of a ghost image or increase in flare amount, or display device Display unevenness may occur when exposure light more than expected is irradiated in the vicinity of the overlapping of the substrates for use. The first reflection suppression layer 13 can suppress the reflection of exposure light on the back surface side of the light shielding film 12 when pattern transfer is performed using a photomask, thereby suppressing transfer image deterioration and improving transfer characteristics. In addition to the above, it is possible to suppress the occurrence of display unevenness due to irradiation of exposure light more than expected in the vicinity of the overlap of the display device substrate.

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

  The second reflection suppression layer 15 is provided on the surface of the light shielding film 12 on the side far from the transparent substrate 11 of the light shielding layer 14. The second antireflection layer 15 forms a resist film on the resist film 15 and draws a predetermined pattern on the resist film with drawing light (laser light) from a drawing device (for example, a laser drawing device). Since reflection on the surface side can be suppressed, CD uniformity (CD uniformity) of the resist pattern and a mask pattern formed based on the resist pattern can be improved. In addition, when used as a photomask, the second reflection suppressing layer 15 is disposed on the display device substrate side which is a 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 this way, it is possible to prevent the reflected light from returning to the transfer target and to prevent the transfer image from deteriorating, thereby contributing to the improvement of transfer characteristics. It is possible to suppress the occurrence of display unevenness due to this.

(Material for light shielding film)
Next, 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. The oxygen in the first reflection suppressing layer 13 has an effect of reducing the reflectance of the exposure light from the back surface side. In addition to the effect of reducing the reflectance of the exposure light from the back surface side, the nitrogen in the first reflection suppression layer 13 is a cross-section of the light shielding film pattern formed by etching (particularly wet etching) using a photomask blank. As a result, the CD uniformity is improved. Note that carbon or fluorine may be further contained from the viewpoint of controlling the etching characteristics.
The light shielding layer 14 is made of a chromium-based material containing chromium and nitrogen. Nitrogen in the light shielding layer 14 is a cross section of a light shielding film pattern formed by etching (particularly wet etching) using a photomask blank with a difference in etching rate between the first reflection suppressing layer 13 and the second reflection suppressing layer 15 being reduced. As well as shortening the etching time in the light shielding film 12 (whole) and improving the CD uniformity. Note that oxygen, carbon, and fluorine may be further contained from the viewpoint of controlling the etching characteristics.
The second reflection suppression layer 15 is made of a chromium-based material containing chromium, oxygen, and nitrogen. The oxygen in the second reflection suppressing layer 15 has an effect of reducing the reflectance of the drawing light of the drawing apparatus from the surface side and the reflectance of the exposure light from the front side. In addition, the adhesion with the resist film is improved, and the effect of suppressing side etching due to the penetration of the etchant from the interface between the resist film and the light shielding film 12 is achieved. Nitrogen in the second antireflection layer 15 is etched using a photomask blank (particularly wet etching) in addition to the effect of reducing the reflectance of the drawing light from the surface side and the reflectance of the exposure light from the surface side. ), The cross section of the light-shielding film pattern formed is brought close to vertical, and the CD uniformity is improved. Note that carbon or fluorine may be further contained from the viewpoint of controlling the etching characteristics.

(Composition of light shielding film)
Next, the composition of each layer in the light shielding film 12 will be described. In addition, let the content rate of each element mentioned later be the value measured by X-ray photoelectric spectroscopy (XPS).

  In the light shielding film 12, the first antireflection layer 13 includes chromium (Cr) in a content of 25 to 75 atomic%, oxygen (O) in a content of 15 to 45 atomic%, and nitrogen (N) in a content of 10 to 30 atomic%. The light shielding layer 14 includes 70 to 95 atomic% of chromium (Cr) and 5 to 30 atomic% of nitrogen (N), and the second antireflection layer 15 includes 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%, respectively. Preferably, the first antireflection layer 13 includes 50 to 75 atomic% of Cr, 15 to 35 atomic% of O, and 10 to 25 atomic% of N, and the second antireflection layer 15 includes 50 of Cr. -75 atomic%, O is contained in a content of 20-40 atomic%, and N is contained in a content of 5-20 atomic%, respectively.

  The first reflection suppression layer 13 and the second reflection suppression layer 15 each have a region in which the content of at least one element of O and N changes in composition continuously or stepwise along the film thickness direction. It is preferable.

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

  Moreover, it is preferable that the 2nd reflection suppression layer 15 has an area | region where N content rate (nitrogen content rate) falls toward the light shielding layer 14 side of a film thickness direction.

  Moreover, it is preferable that the 1st reflection suppression layer 13 has an area | region where N content rate falls while O content rate increases toward the transparent substrate 11 of a film thickness direction.

  Further, in the photomask blank 1 and a photomask manufactured therefrom, the second reflection suppression is performed from the viewpoint of further reducing the reflectance of the light shielding film 12 and the light shielding film pattern on the front and back surfaces and reducing the difference in reflectance. The layer 15 is preferably configured to have a higher O content than the first reflection suppression layer 13, and the first reflection suppression layer 13 has a higher N content than the second reflection suppression layer 15. Preferably it is comprised. Specifically, the O content of the second reflection suppression layer 15 is preferably 5 atomic percent or more, more preferably 10 atomic percent or more, higher than that of the first reflection suppression layer 13. Furthermore, the N content of the first reflection suppression layer 13 is preferably greater than that of the second reflection suppression layer 15 by 5 atomic% or more, more preferably 10 atomic% or more. In addition, if the 1st reflection suppression layer 13 and the 2nd reflection suppression layer 15 have a composition inclination area | region, the O content rate and N content rate show the average density | concentration in a film thickness direction.

  Moreover, in the 1st reflection suppression layer 13, the light shielding layer 14, and the 2nd reflection suppression layer 15, although the change of the content rate of each element may be either continuous or stepwise, it is preferable that it is continuous.

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

(About film thickness)
In the light shielding film 12, the thicknesses of the first reflection suppression layer 13, the light shielding layer 14, and the second reflection suppression layer 15 are not particularly limited, and are appropriately adjusted according to the optical density and reflectance required for the light shielding film 12. Good. The thickness of the first reflection suppression layer 13 is such that light from the back side of the light shielding film 12 is reflected on the surface of the first reflection suppression layer 13 and at the interface between the first reflection suppression layer 13 and the light shielding layer 14. The thickness may be any thickness that can exhibit the light interference effect due to reflection. On the other hand, the thickness of the second reflection suppression layer 15 is such that reflection from the surface of the second reflection suppression layer 15 and the interface between the second reflection suppression layer 15 and the light shielding layer 14 with respect to light from the surface side of the light shielding film 12. It is sufficient that the thickness be such that an 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 to 3.0 or more while setting the reflectance with respect to the exposure wavelength of the front and back surfaces of the light shielding film 12 to be 10% or less, for example, the film thickness of the first reflection suppression layer 13 is 15 nm. It is preferable that the film thickness of the light shielding layer 14 is 50 nm to 120 nm, and the film thickness of the second reflection suppressing layer 15 is 10 nm to 60 nm.

<Method for producing photomask blank>
Then, the manufacturing method of the photomask blank 1 mentioned above is demonstrated.

(Preparation process)
A transparent substrate 11 that is substantially transparent to exposure light is prepared. In addition, it is good to perform arbitrary processing processes, such as a grinding process and a grinding | polishing process, as needed so that the transparent substrate 11 may become a flat and smooth main surface. After polishing, cleaning may be performed to remove foreign matters and contamination on the surface of the transparent substrate 11. As the cleaning, for example, sulfuric acid, sulfuric acid / hydrogen peroxide (SPM), ammonia, ammonia hydrogen peroxide (APM), OH radical cleaning water, ozone water, warm water and the like can be used.

(Formation process of a 1st reflection suppression layer)
Subsequently, the first antireflection layer 13 is formed on the transparent substrate 11. This formation is performed by reactive sputtering using a sputtering target containing Cr and a sputtering gas containing a reactive gas containing an oxygen-based gas and 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 in 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 formation mode when a thin film is formed by reactive sputtering, and the horizontal axis represents the partial pressure (flow rate) of the reactive gas in the mixed gas of the rare gas and the reactive gas. ) Ratio, the vertical axis indicates the voltage applied to the target. In reactive sputtering, when a 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 according to the flow rate of the reactive gas, and accordingly, The film speed changes. There are three modes depending on the difference in 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 that in 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, adhesion of the reactive gas to the target surface can be reduced, and the film formation rate can be increased. In addition, in the metal mode, since the supply amount of the reactive gas is small, for example, at least one of the O concentration (oxygen concentration) and the N concentration (nitrogen concentration) is lower than the film having the stoichiometric composition. 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 reflection suppression 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. The target applied power is preferably 2.0 to 6.0 kW, and the target applied voltage is 420 to 430V.

Any sputtering target may be used as long as it contains Cr. For example, in addition to chromium metal, a chromium-based material such as chromium oxide, chromium nitride, or 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 ) or the like can be used. Among these, it is preferable to use oxygen (O ₂ ) gas because of its high oxidizing power. Further, 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, and xenon gas can be used. In addition to the reactive gas, a hydrocarbon-based gas may be supplied. For example, methane gas or butane gas can be used.

  In this embodiment, the flow rate of the reactive gas and the power applied to the sputtering target are set to be in a metal mode, and a film is formed by reactive sputtering using a sputtering target containing Cr, whereby a transparent substrate is obtained. 11 is formed with a first antireflection layer 13 containing 25 to 75 atomic percent of Cr, 15 to 45 atomic percent of O, and 10 to 30 atomic percent of N.

  In addition, when forming the 1st reflection suppression layer 13 as a single film | membrane with a uniform composition in a film thickness direction, what is necessary is just to form into a film, without changing the kind and flow volume of reactive gas, but it contains O in a film thickness direction. When the composition is tilted so that the rate and N content change, 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. Further, the arrangement of the gas supply ports, the gas supply method, and the like may be changed.

(Shading layer forming process)
Subsequently, the light shielding layer 14 is formed on the first antireflection layer 13. This formation is performed by reactive sputtering using a sputtering target containing Cr and a sputtering gas containing a nitrogen-based gas and a rare gas. At this time, a flow rate at which the flow rate of the reactive gas contained in the sputtering gas is in the metal mode is selected as the film forming condition.
Any target may be used as long as it contains Cr. For example, in addition to chromium metal, a chromium-based material such as chromium oxide, chromium nitride, or chromium oxynitride can be used. 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, and xenon gas can be used. In addition to 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 sputtering target applied power are set to be in a metal mode, and reactive sputtering is performed using a sputtering target containing Cr, whereby the first reflection suppression layer 13 is formed. In addition, the light shielding layer 14 containing Cr in a content of 70 to 95 atomic% and N in a content of 5 to 30 atomic% is formed.

  As the film forming conditions for 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. The target applied power is preferably 3.0 to 7.0 kW and the target applied voltage is 370 to 380V.

(Formation process of 2nd reflection suppression layer)
Subsequently, the second antireflection layer 15 is formed on the light shielding layer 14. This formation is performed by reactive sputtering using a sputtering target containing Cr, with the reactive gas flow rate and target applied power being set to a metal mode, as in the case of the first antireflection layer 13. I do. Thereby, on the light shielding layer 14, the 2nd reflection suppression layer 15 which respectively contains Cr by 30-75 atomic%, O by 20-50 atomic%, and N by 5-20 atomic% is formed.

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

  When the composition of the second antireflection layer is tilted, 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 each layer in the light-shielding film 12 is preferably formed in-situ using an in-line sputtering apparatus. In the case of not being an in-line type sputtering apparatus, it is necessary to take the transparent substrate 11 out of the apparatus after forming each layer, and the transparent substrate 11 may be exposed to the atmosphere, and each layer may be oxidized or carbonized. As a result, the reflectance and etching rate of the light shielding film 12 with respect to the exposure light may be changed. In this regard, with an inline-type sputtering apparatus, each layer can be continuously formed without taking the transparent substrate 11 out of the apparatus and exposing it to the atmosphere, thereby suppressing unintentional incorporation of elements into the light shielding film 12. Can do.

  Moreover, when forming the light shielding film 12 using an in-line type sputtering apparatus, the composition inclination area | region (the composition inclination area | region (A) between each layer of the 1st reflection suppression layer 13, the light shielding layer 14, and the 2nd reflection suppression layer 15 is continuously inclined. Therefore, the light-shielding film pattern formed by etching (especially wet etching) using a photomask blank can have a smooth cross section and can be brought close to vertical.

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

(Resist film formation process)
First, a resist is applied on the second antireflection 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.

(Resist pattern formation process)
Subsequently, a predetermined pattern is drawn on the resist film using a drawing apparatus. Usually, when producing a photomask for manufacturing a display device, 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 suppression layer 15 is configured to be low, reflection of drawing light (laser light) can be reduced when a pattern is drawn on the resist film. Thereby, a resist pattern with high pattern accuracy can be formed, and accordingly, a mask pattern with high dimensional accuracy can be formed.

(Mask pattern formation process)
Subsequently, the light shielding film 12 is etched using the resist pattern as a mask to form a mask pattern made of the light shielding film pattern. Etching may be wet etching or dry etching. Usually, in a photomask for manufacturing a display device, wet etching is performed. As an etchant used in the wet etching, for example, a chromium etchant 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 suppression layer 13, the light shielding layer 14, and the second reflection suppression layer 15 are aligned in the thickness direction of the light shielding film 12, wet etching is performed. Thus, the cross-sectional shape of the light-shielding film pattern (mask pattern) can be made perpendicular to the transparent substrate 11, and high CD uniformity (CD uniformity) can be obtained.

(Peeling process)
Subsequently, the resist pattern is peeled off 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.

<Manufacturing method of 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 formed on the substrate of the display device via the projection optical system of the exposure device. It is placed on the mask stage of the exposure apparatus so as to face the resist film.

(Exposure process (pattern transfer process))
Next, a resist exposure process is performed in which the photomask is irradiated with exposure light to transfer the pattern to a resist film formed on the substrate of the display device.
The exposure light is, for example, single wavelength light 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), etc.) Or 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), g-line (wavelength 436 nm)). In this embodiment, a display device (display panel) is manufactured using a photomask with reduced reflectance on the front and back surfaces of the light-shielding film pattern (mask pattern). Can be obtained.

<Effect according to this embodiment>
According to the present embodiment, the following one or more effects are achieved.

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

(B) Moreover, in this 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 back side (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 respectively. For example, the reflectance of the photomask blank 1 can be adjusted 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 exposure light from the photomask to the light source side (ghosting, etc.) when exposing the transfer object using the produced photomask, the reflectance on the back side Is preferably higher than the surface side. In other words, it is preferable that the reflectance on the front surface side (light shielding film 12 side) of the photomask blank 1 is lower than the reflectance on the back surface side (transparent substrate 11 side). Specifically, when the wiring pattern of the gate electrode or source / drain electrode in the TFT array is transferred to the resist film formed on the substrate of the display device that is the transfer target, the light shielding film pattern of the photomask is changed. Since the aperture ratio is 50% or more, the amount of exposure light passing through the photomask increases, and flare due to the return light of the exposure light from the transfer target is likely to occur. Therefore, the reflectance with respect to the exposure wavelength of the front and back surfaces of the light shielding film 12 of the photomask blank 1 is 10% or less, respectively, and the reflectance on the front surface side of the light shielding film 12 is made lower than the reflectance on the back surface side. As a result, the influence of flare can be reduced, and a CD error when a display device is manufactured using a photomask can be prevented.

(C) In the present embodiment, the first reflection suppression layer 13, the light shielding layer 14, and the second reflection suppression layer 15 constituting the light shielding film 12 are within the above composition range, thereby reducing the etching rate. By increasing the etching rate, the concentration of N can be reduced, and the difference in etching rate between the layers can be suppressed. 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 perpendicular to the transparent substrate 11. Specifically, in the cross-sectional shape of the mask pattern, when the angle between the side surface formed by etching and the transparent substrate 11 is θ, θ can be in the range of 90 ° ± 30 °. Further, the cross-sectional shape of the mask pattern is made close to vertical, and the etching residue of the first reflection suppression layer 13 or the biting (so-called undercut) and side etching of the first reflection suppression layer 13 and the second reflection suppression layer 15 is performed. 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) Further, in the present embodiment, the light shielding film 12 has a reduced etching time by aligning the etching rates of the first reflection suppression layer 13, the light shielding layer 14, and the second reflection suppression layer 15 constituting the light shielding film 12. Regardless of the length, the density of the etching solution, and the temperature of the etching solution, the perpendicularity of the cross-sectional shape can be stably secured. For example, when the just etching time of the light shielding film 12 is T, even if the etching time is 1.5 × T and overetching 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 etching time is 1.5 × T is 10 ° or less. Can be. Similarly, when the concentration of the etching solution is increased and when the concentration of the etching solution is decreased, the difference in angle between the cross-sections of the light shielding film pattern 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. The difference in angle between the cross-sections of the light shielding film pattern can be made 10 ° or less. Note that the just etching time indicates an etching time from when the light shielding film 12 is etched in the film thickness direction until the surface of the transparent substrate 11 begins 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, and the first reflection suppression layer 13 includes 50 Cr. -75 atomic%, O is included in a content of 15-35 atomic%, and N is included in a content of 10-25 atomic%. The second antireflection layer 15 is 50-75 atomic% in Cr and 20-40 atomic% in O. , N is preferably included at a content of 5 to 20 atomic%.

  In the 1st reflection suppression layer 13 and the 2nd reflection suppression layer 15, the excessive increase in the etching rate by containing O in these layers can be suppressed by reducing O content rate more. Therefore, the content ratio of carbon (C) blended in the light shielding layer 14 is reduced 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. Alternatively, the light shielding layer 14 can be made carbon-free 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 maintained high.

  On the other hand, in the 1st reflection suppression layer 13 and the 2nd reflection suppression layer 15, the excessive increase in the etching rate by containing N in these layers can be suppressed by reducing N content rate more. Therefore, the content rate of N contained in the light shielding layer 14 may be reduced 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 maintained high.

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

  Further, in each of the first reflection suppression layer 13, the light shielding layer 14, and the second reflection suppression layer 15 constituting the light shielding film 12, when the O content increases, the etching rate increases excessively or the N content increases. Although an etching rate will increase excessively, the difference in the etching rate of each layer by containing these elements can be suppressed by making the content rate of O and N low. That is, the difference in etching rate between the first reflection suppression layer 13 and the second reflection suppression layer 15 and the light shielding layer 14 can be suppressed. As a result, N or carbon contained in the light shielding layer 14 is reduced 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, or the light shielding layer. 14 can be made carbon-free without containing carbon. As a result, the Cr content in the light shielding layer 14 can be increased and the optical density (OD) can be maintained high.

(G) It is preferable that the 2nd reflection suppression layer 15 has an area | region where O content rate increases toward the light shielding layer 14 side of a film thickness direction. Thereby, in the 2nd reflection suppression layer 15, O content rate of the interface part with the light shielding layer 14 is made high locally, and the average O content rate in the film thickness direction is made low. As a result, a desired reflectance can be obtained on the surface side (second reflection suppression layer 15) of the light shielding film 12, and biting due to excessive etching at the interface can be suppressed.

(H) It is preferable that the 2nd reflection suppression layer 15 has an area | region where N content rate falls toward the light shielding layer 14 side of a film thickness direction. Thereby, in the 2nd reflection suppression layer 15, the N content rate of the interface part with the light shielding layer 14 is made low locally, maintaining the average N content rate in the film thickness direction 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) It is preferable that the 1st reflection suppression layer 13 has an area | region where N content rate falls while O content rate increases toward the transparent substrate 11 of a film thickness direction. In the first reflection suppression layer 13, the etching rate can be gradually lowered toward the transparent substrate 11 by increasing the O content toward the transparent substrate 11 in the film thickness direction and decreasing the N content. . Thereby, the biting 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 suppression layer 15 is preferably configured to have an O content higher than that of the first reflection suppression layer 13. Specifically, the O content of the second reflection suppression layer 15 is preferably 5 atomic% or more higher than that of the first reflection suppression layer 13, and more preferably 10 atomic% or more. Moreover, it is preferable that the 1st reflection suppression layer 13 is comprised so that N content rate may become higher than the 2nd reflection suppression layer 15. FIG. Specifically, the N content of the first reflection suppression layer 13 is preferably greater than that of the second reflection suppression layer 15 by 5 atomic% or more, more preferably 10 atomic% or more. According to the study by the present inventors, when the first reflection suppression layer 13 and the second reflection suppression layer 15 are formed of the same material, the reflectance on the front surface side is higher than that on the back surface side although the composition is the same. It turns out that it tends to be higher. Then, when the composition ratio (O content rate, N content rate) of each layer of the 1st reflection suppression layer 13 and the 2nd reflection suppression layer 15 was further examined, the composition ratio of the 1st reflection suppression layer 13 and the 2nd reflection suppression layer 15 was demonstrated. It has been found that by making (O content, N content) as described above, the reflectance on the back surface side can be reduced to the same level as the front surface side or lower than the front surface side. Thus, the reflectance of the front and back surfaces can be controlled by changing the composition ratio (O content, N content) of each layer.

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

According to (l) In the first embodiment, the first antireflection layer 13 and the second antireflection layer 15, chromium nitride (CrN) and chromium oxide _{(III) (Cr 2 O 3} ) and chromium (VI) oxide It is preferable to use a chromium-based material in a bonded state (chemical state) containing (CrO ₃ ). When the first reflection suppression layer 13 and the second reflection suppression 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. Further, since the first reflection suppressing layer 13 and the second reflection suppressing layer 15 contain CrN chromium nitride, it is possible to suppress an excessive decrease in the etching rate due to the above-described chromium oxide. The shape can be close to vertical.

(M) According to the present embodiment, the first antireflection layer 13 and the second antireflection layer 15 are formed by adding a sputtering target containing Cr, and a sputtering gas containing an oxygen-based gas, a nitrogen-based gas, and a rare gas. Film formation by reactive sputtering is performed, and the light shielding layer 14 is formed by reactive sputtering using a sputtering target containing Cr and a sputtering gas containing a nitrogen-based gas and a rare gas. Then, a flow rate at which the flow rate of the reactive gas contained in the sputtering gas is in the metal mode is selected as the film forming condition for the reactive sputtering. Thereby, each layer of the 1st reflection suppression layer 13, the light shielding layer 14, and the 2nd reflection suppression layer 15 which comprises the light shielding film 12 is easy to adjust to the said composition range, and the reflectance of the front and back of the light shielding film 12 is effective. The cross-sectional shape of the light-shielding film pattern when the light-shielding film 12 is patterned can be made close to vertical while reducing the amount of the light.

(N) When forming each layer of the first antireflection layer 13 and the second antireflection layer 15 by reactive sputtering, it is preferable to use oxygen (O ₂ gas) as the oxygen-based gas. Since O ₂ gas has higher oxidizing power than other oxygen-based gases, each layer can be reliably adjusted by the above composition range even when the metal mode is selected for film formation. Thereby, the cross-sectional shape of the light shielding film pattern when patterning the light shielding film 12 can be made close to vertical while effectively reducing the reflectance of 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 surface side is low, a resist film is provided on the light shielding film 12, and when the resist pattern is formed by the drawing / development process, Reflection on the surface of the light shielding film 12 can be reduced. Thereby, the dimensional accuracy of the resist pattern can be increased, and the dimensional accuracy of the light shielding film pattern of the photomask formed therefrom can be increased.

(P) The photomask manufactured from the photomask blank 1 of this embodiment has a highly accurate light-shielding film pattern and a reduced reflectance on the front and back surfaces of the light-shielding film pattern. High transfer characteristics can be obtained during pattern transfer.

(Q) Moreover, in this embodiment, even if it is a case where the photomask blank 1 is enlarged using the board | substrate which is rectangular shape and the length of a short side is 850 mm or more and 1620 mm or less 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 maintained high.

(R) In the photomask of this embodiment, the reflectance of 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 is 10% or less, preferably 7.5% or less. Since it can be preferably 5% or less, for example, even when the exposure light intensity is increased such as exposure of composite light including i-line, h-line, and g-line, it is higher than the transfer target. An accurate transfer pattern can be formed. Further, it is possible to prevent display unevenness that occurs when exposure light more than expected is irradiated in the vicinity of an overlap of a transfer target (for example, a display panel). As the exposure light, composite light including light of a plurality of wavelengths selected from the wavelength range of 300 nm to 550 nm, or monochromatic light selected by cutting a wavelength range from the wavelength range of 300 nm to 550 nm with a filter or the like is used. For example, there are composite light including a j-line with a wavelength of 313 nm, an i-line with a wavelength of 365 nm, an h-line with a wavelength of 405 nm, and a g-line with a wavelength of 436 nm, and monochromatic light of i-line.

<Other embodiments>
As mentioned above, although one Embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the summary, it can change suitably.

In the above-described 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-transparent 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. This 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 the 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 due to the phase shift effect. The mask pattern in this phase shift mask is a phase shift film pattern, a phase shift film pattern, and a light shielding film pattern.
As the above-described semi-transparent film and phase shift film, a material having etching selectivity with respect to a chromium-based material that is a material constituting 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, and oxygen, nitrogen, A material containing at least one of carbon and fluorine is suitable. For example, metal silicide such as MoSi, ZrSi, TiSi, TaSi, metal silicide oxide, metal silicide nitride, metal silicide oxynitride, metal silicide carbonitride, metal silicide oxycarbide, metal silicide carbonization Oxynitrides are suitable. The semi-transparent film and the phase shift film may be a laminated film composed of the above-described films as the functional film.
In the above-described semi-transparent film and phase shift film, the transmittance of the exposure light with respect to the exposure wavelength can be appropriately adjusted within a range of 1 to 80%. In the combination with the light-shielding film of the present invention, the transmittance of the above-mentioned 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 exposure light and combining the light-shielding film of the present invention Alternatively, the reflectance with respect to the exposure wavelength of the back surface in the laminated film in which the phase shift film and the light shielding film are formed can be 40% or less, more preferably 30% or less.

  Moreover, although the above-mentioned embodiment demonstrated the case where the 1st reflection suppression layer 13 and the 2nd reflection suppression layer 15 were one layer each, this 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 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 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 etching selectivity with respect to a chromium-based material that is a material constituting the light shielding film 12. Such materials include molybdenum (Mo), zirconium (Zr), titanium (Ti), metal silicide-based materials containing tantalum (Ta) and silicon (Si), Si, SiO, SiO ₂ , SiON, Si silicon-based material ₃ N ₄ and the like.

  EXAMPLES Next, although this invention is demonstrated in detail based on an Example, this invention is not limited to these Examples.

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

The film formation conditions of the first antireflection layer are such that the sputter target is a Cr sputter target, and the flow rate of the reactive gas is 5 to 45 sccm for oxygen (O ₂ ) gas and nitrogen (N ₂ ) so as to be in the metal mode. ) The gas flow rate is selected in the range of 30-60 sccm and the argon (Ar) gas flow rate in the range of 60-150 sccm, the target applied power is in the range of 2.0-6.0 kW, and the target applied voltage is in the range of 420-430 V. Set in. In addition, the board | substrate conveyance speed at the time of film-forming of a 1st reflection suppression layer was 350 mm / min.

The light-shielding layer is formed by using a sputtering target as a Cr sputtering target, and a reactive gas flow rate of 1-60 sccm for nitrogen (N ₂ ) gas and a flow rate for argon (Ar) gas so as to be in a metal mode. Was selected from the range of 60 to 200 sccm, the target applied power was set to 3.0 to 7.0 kW, and the applied voltage was set to the range of 370 to 380 V. In addition, the board | substrate conveyance speed at the time of film-forming of a light shielding layer was 200 mm / min.

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

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

In FIG. 2, the region from the surface to the depth of about 5 min (min) is the surface natural oxidation layer, and the region from the depth of about 5 min (min) to the 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 the depth of about 124 min (min) is the transition layer, and the region from the depth of about 124 min (min) to the depth of about 132 min (min) is the first antireflection layer. A region from a depth of about 132 min (min) is a transparent substrate.
In addition, the film thickness of the light shielding film measured by the film thickness meter is 198 nm, and each film thickness of the surface natural oxidation layer, the second reflection suppression layer, the transition layer, the light shielding layer, the transition layer, and the first reflection suppression layer is The surface natural oxide layer was about 4 nm, the second reflection suppression 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 suppression layer is a CrON film, and includes 55.4 atomic% of Cr, 20.8 atomic% of N, and 23.8 atomic% of O. The content ratios of these elements are measured at a portion where N peaks in the first antireflection layer (region where the sputtering time is 123 min (minutes)). The first antireflection layer has a gradient composition as shown in FIG. 2, and has a portion where the N content decreases while the O content increases toward the transparent substrate in the film thickness direction. In the first antireflection layer, the average content of each element in the film thickness direction was 57 atomic% for Cr, 18 atomic% for N, and 25 atomic% for O.

  The light shielding layer is a CrN film and contains 92.0 atomic% of Cr and 8.0 atomic% of N. The content ratios of these elements are measured at the central portion in the film thickness direction of the light shielding layer (the region where the sputtering time is 69 min (min)). 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 antireflection layer is a CrON film and contains 50.7 atomic% of Cr, 12.2 atomic% of N, and 37.1 atomic% of O. The content ratios of these elements are measured at the central portion (region where the sputtering time is 16 min (min)) where O is increasing in the second antireflection 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 film thickness direction was 52 atomic% for Cr, 17 atomic% for N, and 31 atomic% for O. Also, a surface natural oxidation layer is formed on the surface of the second antireflection layer 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.

Moreover, the spectrum analysis was performed based on the XPS measurement result about the coupling | bonding state (chemical state) of each layer of the 1st reflection suppression layer which comprises a light shielding film, a light shielding layer, and a 2nd reflection suppression layer. As a result, the first antireflection layer and the second antireflection layer include chromium mononitride (CrN), chromium oxide (III) (Cr ₂ O ₃ ), and chromium oxide (VI) (CrO ₃ ), and chromium and oxygen And a chromium-based material (chromium compound) containing nitrogen. Moreover, 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.

  For the photomask blank of Example 1, the optical density of the light-shielding film was measured with a spectrophotometer (“SolidSpec-3700” manufactured by Shimadzu Corporation). As a result, the g-line (wavelength 436 nm), which is the wavelength region of exposure light. 5.0. Moreover, 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 (front surface reflectance) on the second reflection suppression layer side of the light shielding film and the reflectance (back surface reflectance) on the transparent substrate side of the light shielding film 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, the horizontal axis indicates the wavelength [nm], and the vertical axis indicates the reflectance [%]. As shown in FIG. 3, the photomask blank of Example 1 can make the bottom peak wavelength of the reflectance spectrum on the front and back surfaces close to 436 nm, and can greatly reduce the reflectance for light of a wide range of wavelengths. 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 back surface 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)). The reflectance of the front and back surfaces of the light-shielding film can be reduced to 10% or less at wavelengths of 365 nm to 436 nm. In particular, with respect to the reflectance with respect to light having a wavelength of 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 shading film pattern)
Using the photomask blank of Example 1, a light shielding film pattern was formed on the transparent substrate. Specifically, a novolac positive resist film was formed on the light-shielding film on the transparent substrate, and then a resist pattern was formed by laser drawing (wavelength 413 nm) and development treatment. Thereafter, the resist pattern was used as a mask and wet etching was performed with a chromium etching solution 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 brought close to vertical. FIG. 4 is a diagram for explaining the perpendicularity of the cross-sectional shape of the light-shielding film pattern by wet etching for the photomask blank of Example 1, and the etching time based on the just etching time (JET) as a reference (100%). The cross-sectional shapes when over-etching with 110%, 130%, and 150% are shown. In FIG. 4, it was confirmed that the light shielding film pattern and the resist film pattern were laminated on the transparent substrate, and the angle between the side surface of the light shielding film pattern and the transparent substrate was 70 ° when JET was 100%. . This angle is within 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 is independent of the etching time. It was confirmed that the film can be formed stably and vertically.

  As described in Example 1 above, the light-shielding film of the photomask blank is configured such that the first reflection suppression layer, the light-shielding layer, and the second reflection suppression layer are laminated from the transparent substrate side, and each layer has a predetermined composition. Thus, the reflectance of the front and back surfaces was reduced in a wide wavelength range, and the cross-sectional shape of the light shielding film pattern when patterned by wet etching could be formed vertically.

(Production of photomask)
Next, a photomask was manufactured using the photomask blank of Example 1.
First, a novolac positive resist was formed on the light shielding film of the photomask blank. Then, using a laser drawing device, a pattern of a circuit pattern for the TFT panel was drawn on this resist film, and further developed and rinsed to form a predetermined resist pattern (the minimum line width of the above circuit pattern is 0.75 μm).
Then, using the resist pattern as a mask, the light shielding film is patterned by wet etching using a chrome etching solution, and finally the resist pattern is peeled off by the resist stripping solution, and the light shielding film pattern (mask pattern) is formed on the transparent substrate. A formed photomask was obtained.
The CD uniformity of the light-shielding film pattern of this photomask was measured by “SIR8000” manufactured by Seiko Instruments Nano Technology Co., Ltd. The CD uniformity was measured at a point of 11 × 11 in a 1100 mm × 1300 mm region excluding the peripheral region of the substrate.
As a result, the CD uniformity was 100 nm, and the CD uniformity of the obtained photomask was good.

(Production of LCD panel)
The photomask produced in Example 1 is set on a mask stage of an exposure apparatus, and a pattern exposure is performed on a transfer object having a resist film formed on a substrate for a display device (TFT) to produce 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 produced by combining the produced TFT array with a color filter, a polarizing plate and a backlight. As a result, a TFT-LCD panel without display unevenness was obtained.

<Example 2>
(Production 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 1220 mm × 1400 mm transparent substrate, the first reflection suppression layer, the light shielding layer, and the second reflection suppression layer are laminated under the same conditions as in Example 1. The photomask blank of Example 2 was manufactured.
For the formation of the semi-transparent film, a molybdenum silicide nitride film (MoSiN) was formed by reactive sputtering using a mixed gas of argon (Ar) gas and nitrogen (N ₂ ) gas with a sputtering target as a MoSi sputtering target. This semi-transparent film was appropriately adjusted in composition ratio and film thickness so that the transmittance was 40% at i-line (wavelength 365 nm).
Next, similarly to Example 1, a photomask blank of Example 2 was produced by forming a light-shielding film comprising a first antireflection layer, a light-shielding layer, and a second antireflection layer on the above-described semi-transparent film. .

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

(Production of photomask)
Next, a photomask was produced using the photomask blank of Example 2. The photomask includes a translucent film pattern on a transparent substrate, a light-shielding film pattern formed on the semi-transparent film pattern, and a transfer pattern including a translucent part, a light-shielding part, and a semi-translucent part. The photomask of Example 2 was manufactured by the gray tone mask manufacturing method 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)
Using the photomask produced in this Example 2, an LCD panel was produced in the same manner as in Example 1. As a result, a TFT-LCD panel without display unevenness was obtained. In addition, as a manufacturing method of the photomask of Example 2, it can produce with the manufacturing method of the photomask described in patent 56051717, and the semi-transparent film pattern and light shielding of the photomask obtained by this method The CD uniformity of the film pattern is also good. A TFT-LCD panel with little display unevenness can be obtained.

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

The film formation conditions of the first antireflection layer are as follows. The sputtering target is a Cr sputtering target, and the flow rate of the reactive gas is 150 to 300 sccm for oxygen (O ₂ ) gas and nitrogen (N ₂ ) so that the reaction mode is set. ) A gas flow rate of 150 to 300 sccm, a methane (CH ₄ ) gas flow rate of 5 to 15 sccm, and an argon (Ar) gas flow rate of 100 to 150 sccm, respectively, and a target applied power of 2.0 to 7 are selected. It was set in the range of 0.0 kW. In addition, the board | substrate conveyance speed at the time of film-forming of a 1st reflection suppression layer was 200 mm / min, and film-forming was performed 3 times.

The light-shielding layer is formed by using a sputtering target as a Cr sputtering target, and a reactive gas flow rate of 1-60 sccm for nitrogen (N ₂ ) gas and a flow rate for argon (Ar) gas so as to be in a metal mode. 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 board | substrate conveyance speed at the time of film-forming of a light shielding layer was 200 mm / min.

The film formation condition of the second antireflection layer is such that the sputtering target is a Cr sputtering target, and the flow rate of the reactive gas is 150 to 300, and the nitrogen (N ₂ ) flow rate of oxygen (O ₂ ) gas is set to the reaction mode. ) A gas flow rate of 150 to 300 sccm, a methane (CH ₄ ) gas flow rate of 5 to 15 sccm, and an argon (Ar) gas flow rate of 100 to 150 sccm, respectively, and a target applied power of 2.0 to 7 are selected. It was set in the range of 0.0 kW. In addition, the board | 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 film thickness of the surface natural oxidation layer, the second reflection suppression layer, the light shielding layer, and the first reflection suppression layer is about 3 nm, the second reflection suppression layer is about 51 nm, the light shielding layer is about 101 nm, and the first reflection suppression layer. Was about 51 nm. In addition, a transition layer in which the composition of each element is continuously inclined is formed between the second reflection suppressing layer and the light blocking layer and between the light blocking layer and the first reflection suppressing layer.

About the light shielding film of the photomask blank of Comparative Example 1, the content ratios of the elements contained in each layer were measured, and the results were as follows. In addition, the content rate of each layer shown below shows the content rate averaged in the film thickness direction of each element.
The first antireflection 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 antireflection layer is a CrON film and contains 45 atomic% of Cr, 3 atomic% of N, and 52 atomic% of O.

Similarly to 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% for g-line (wavelength 436 nm), which is the wavelength region of exposure light, and 4.5% for i-line (wavelength 365 nm). In addition, 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 has a tapered shape near the transparent substrate and a reverse tapered shape near the resist film, and the cross-sectional shape is very bad. It was confirmed that the angle formed with the transparent substrate when JET was 100% was 150 °.

  Next, using the photomask blank of Comparative Example 1, a photomask was produced in the same manner as in Example 1. As a result of measuring the CD uniformity of the light-shielding film pattern of the obtained photomask, the result was bad at 200 nm. Thus, in the mask blank of Comparative Example 1, the reflectance of 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 reflection suppression layer, the light shielding layer, and the second reflection suppression layer is formed of a material having a predetermined composition, and the thickness of each layer is set to CD uniformity is good when a photomask is produced by etching by forming a photomask blank by setting the reflectance of the front and back surfaces to 10% or less and the optical density to be 3.0 or more. Thus, a highly accurate mask pattern can be obtained. According to such a photomask, a display device with little display unevenness can be manufactured.

DESCRIPTION OF SYMBOLS 1 Photomask blank 11 Transparent substrate 12 Light shielding film 13 1st reflection suppression layer 14 Light shielding layer 15 2nd reflection suppression layer

Claims (22)

A photomask blank used when producing a photomask for manufacturing a display device,
A transparent substrate made of a material substantially transparent to exposure light;
A light-shielding film provided on the transparent substrate and 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 suppression layer is a chromium-based material containing chromium, oxygen, and nitrogen, the chromium content is 25 to 75 atomic%, the oxygen content is 15 to 45 atomic%, and the nitrogen content is Has a composition of 10 to 30 atomic%,
The light shielding layer is a chromium-based material containing chromium and nitrogen, and has a chromium content of 70 to 95 atomic% and a nitrogen content of 5 to 30 atomic%,
The second antireflection layer is a chromium-based material containing chromium, oxygen, and nitrogen, and the chromium content is 30 to 75 atomic%, the oxygen content is 20 to 50 atomic%, and the nitrogen content is Has a composition of 5 to 20 atomic%,
The first antireflection layer, the light shielding layer, the reflectance of the exposure light on the front surface and the back surface of the light shielding film with respect to the exposure wavelength of the exposure light is 10% or less and the optical density is 3.0 or more. And the film thickness of the said 2nd reflection suppression layer is set, The photomask blank characterized by the above-mentioned. 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 antireflection 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 described in 1.   Each of the first antireflection layer and the second antireflection layer has a region in which the content of at least one element 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 is a photomask blank.   4. The photomask blank according to claim 1, wherein the second reflection suppression layer has a region in which an oxygen content rate increases toward the light shielding layer in the film thickness direction. .   5. The photomask blank according to claim 1, wherein the second reflection suppression layer has a region in which a nitrogen content decreases toward the light shielding layer side in a film thickness direction. .   The said 1st reflection suppression layer has an area | region where the content rate of nitrogen increases and the content rate of nitrogen falls toward the said transparent substrate of a film thickness direction, The any one of Claims 1-5 characterized by the above-mentioned. The photomask blank according to item.   The photomask blank according to any one of claims 1 to 6, wherein the second antireflection layer is configured to have a higher oxygen content than the first antireflection layer. .   The photomask blank according to any one of claims 1 to 7, wherein the first reflection suppression layer is configured to have a higher nitrogen content than the second reflection suppression layer. . The photomask blank according to claim 1, wherein the light shielding layer includes chromium (Cr) and dichromium nitride (Cr ₂ N). The first reflection suppression layer and the second reflection suppression layer include chromium mononitride (CrN), chromium oxide (III) (Cr ₂ O ₃ ), and chromium oxide (VI) (CrO ₃ ). The photomask blank according to any one of claims 1 to 9.   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 | membrane which has an optical density lower than the optical density of the said light shielding film is further provided between the said transparent substrate and the said light shielding film, The Claim 1 characterized by the above-mentioned. 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 produced by forming a light-shielding film made of a material substantially opaque to exposure light on a transparent substrate made of a material substantially transparent to exposure light by a sputtering method. A method of manufacturing a photomask blank used in the process,
On the transparent substrate, chromium, oxygen, and nitrogen are formed by reactive sputtering using a sputtering target containing chromium, a reactive gas containing an oxygen-based gas and a nitrogen-based gas, and a sputtering gas containing a rare gas. A first antireflection layer comprising a chromium-based material having a composition in which the chromium content is 25 to 75 atomic%, the oxygen content is 15 to 45 atomic%, and the nitrogen content is 10 to 30 atomic%. Forming a step;
Chromium containing chromium and nitrogen is formed on the first antireflection layer by reactive sputtering using a sputtering target containing chromium and a sputtering gas containing a reactive gas containing a nitrogen-based gas and a rare gas. A step of forming a light shielding layer having a composition of a chromium content of 70 to 95 atomic% and a nitrogen content of 5 to 30 atomic%,
On the light shielding layer, chromium, oxygen, and nitrogen are formed by reactive sputtering using a sputtering target containing chromium, a reactive gas containing an oxygen-based gas and a nitrogen-based gas, and a sputtering gas containing a rare gas. A second antireflection layer comprising a chromium-based material having a composition of 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 contained in the sputtering gas is selected to be a metal mode, and the reflectance of the exposure light on the front and back surfaces of the light shielding film with respect to the exposure wavelength is 10% or less, respectively. The film thicknesses of the first antireflection layer, the light shielding layer, and the second antireflection layer are formed so that the optical density is 3.0 or more. . The method for producing a photomask blank according to claim 14, wherein the oxygen-based gas is oxygen (O ₂ ) gas.   The first reflection suppression layer, the light shielding layer, and the second reflection suppression layer are formed using an in-line type sputtering apparatus that forms the light shielding film while the transparent substrate moves relative to the sputtering target. 16. The method for producing a photomask blank according to claim 14 or 15, wherein:   17. The translucent 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. Photomask blank manufacturing method.   The method of manufacturing a photomask blank 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. Preparing the photomask blank according to any one of claims 1 to 11,
Forming a light shielding film pattern on the transparent substrate by forming a resist film on the light shielding film, etching the light shielding film using a resist pattern formed from the resist film as a mask;
A method for producing a photomask, comprising: Preparing the photomask blank according to claim 12;
Forming a light shielding film pattern on the transparent substrate by forming a resist film on the light shielding film, etching the light shielding film using a resist pattern formed from the resist film as a mask;
Etching the semi-transparent film using the light-shielding film pattern as a mask to form a semi-transparent film pattern on the transparent substrate;
A method for producing a photomask, comprising: Preparing the photomask blank according to claim 13;
Forming a light shielding film pattern on the transparent substrate by forming a resist film on the light shielding film, etching the light shielding film using a resist pattern formed from the resist film as a mask;
Etching the phase shift film using the light shielding film pattern as a mask to form a phase shift film pattern on the transparent substrate;
A method for producing a photomask, comprising: A photomask obtained by the photomask manufacturing method according to any one of claims 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 for manufacturing a display device, comprising: an exposure step of exposing and transferring at least one mask pattern of a semi-transparent film pattern and the phase shift film pattern onto a resist formed on a display device substrate.