JP2019117376A - Photomask blank and manufacturing method of photomask, manufacturing method of display device - Google Patents

Abstract

To provide a photomask blank providing a high accuracy mask pattern when a photomask is manufactured by etching, and satisfying optical properties to suppress display unevenness when a display device is manufactured by using the photomask.SOLUTION: There is provided a photomask blank used when a photomask for manufacturing a display device is manufactured, having a transparent substrate consisting of a practically transparent material to an exposed light, and a light shielding arranged on the transparent substrate and consisting of a material with practically opacity to the exposed light, in which the light shielding film has a first reflection suppressing layer, a light shielding layer and a second reflection suppressing layer from a transparent substrate side, when a surface in a side of the light shielding film is a front surface, and a surface in a side of the transparent substrate is a back surface in double surfaces of the photomask blank, front surface reflectivity and back reflectivity to the exposed light is 10% or less respectively at exposed wavelength in a range of 365 nm to 436 nm, and wavelength dependence of the back surface reflectivity in the wavelength range is 5% or less.SELECTED DRAWING: Figure 1

Description

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

  In display devices such as FPD (Flat Panel Display) represented by LCD (Liquid Crystal Display), high definition and high speed display are rapidly advancing along with enlargement of a screen and widening of a viewing angle. One of the necessary elements for achieving high definition and high speed display is the production of electronic circuit patterns such as fine elements with high dimensional accuracy and wiring. Photolithography is often used for the patterning of the display electronic circuit. For this reason, there is a need for a photomask for manufacturing a display device on which a fine and highly accurate pattern is formed.

  Photomasks for display manufacturing are made from photomask blanks. 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 the photomask blank and the photomask, in order to suppress the reflection of light when exposed, a reflection suppression layer is provided on both the front and back sides of the light shielding film, and the photomask blank is, for example, the first in order from the transparent substrate side. It has a film configuration in which the reflection suppression layer, the light shielding layer, and the second reflection suppression 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 a technique related to such a photomask for manufacturing a display device, a photomask blank serving as an original plate thereof, and a method for manufacturing both of them.

Korean Registered Patent No. 10-1473163

  In the manufacture of a display device (for example, a display panel for TV), for example, after a predetermined pattern is transferred to a display device substrate using a photomask, the display device substrate is slid to transfer the predetermined pattern. To repeat the pattern transfer. In this transfer, the reflected light from the back side of the photomask when the exposure light is incident on the photomask from the light source of the exposure device, or the reflected light from the transfer target after the exposure light passes through the photomask. Under the influence of the reflected light returned to the side, exposure light more than expected may be irradiated in the vicinity of the overlapping of the display devices. As a result, display unevenness may occur in a display device manufactured by exposing the adjacent patterns so as to partially overlap each other. In particular, in the manufacture of display devices, light with a wide wavelength band (composite light including a plurality of light with different wavelengths) may be used as exposure light as the photomask is enlarged, and display unevenness is more pronounced. Tends to be

  Therefore, in the photomask blank, in order to suppress display unevenness, the reflectance of the front and back 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) Is required. Furthermore, from the viewpoint of improving the CD uniformity of the photomask, in consideration of the surface reflection of the light shielding film in the laser drawing light, the reflectance of the light shielding film surface is 5% or less (for example, wavelength 413 nm), further Preferably, it is 3% or less (e.g., wavelength 413 nm).

  In addition to the demand for higher definition and higher speed display of display devices, photomasks for display device manufacturing are also increasing in substrate size, and in recent years, rectangles with a short side of 850 mm or more have been developed. Ultra-large photomasks using shaped substrates are used in the manufacture of displays. As the above-mentioned large-sized photomask having a short side length of 850 mm or more, there are 850 mm × 1200 mm size for G7, 1220 mm × 1400 mm size for G8, and 1620 mm × 1780 mm size for G10. As the CD uniformity of the mask pattern in the photomask of the present invention, a mask pattern with a high precision of 100 nm or less is required.

  In the photomask blank of Patent Document 1 that has been conventionally proposed, 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. It has not been possible to satisfy the requirement that the CD uniformity of the mask pattern in a photomask made using a mask blank be 100 nm or less.

  The present invention provides a photomask blank that achieves a mask pattern with high accuracy when a photomask is manufactured by etching, and optical characteristics that can suppress display unevenness when a display device is manufactured using a photomask. Intended to provide.

(Configuration 1)
A photomask blank for use in producing a photomask for display device manufacture, comprising:
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,
When the surface on the light shielding film side is the front surface and the surface on the transparent substrate side is the back surface of both sides of the photomask blank, the surface reflectance and the back surface reflection for the exposure light within the range of the exposure wavelength of 365 nm to 436 nm A photomask blank characterized in that the respective rates are 10% or less, and the wavelength dependency of the back surface reflectance in the wavelength range is 5% or less.

(Configuration 2)
The photomask blank according to Configuration 1, wherein the back surface reflectance is smaller than the surface reflectance over the entire area within an exposure wavelength range of 365 nm to 436 nm.

(Configuration 3)
The reflectance spectrum of the front surface and the back surface in a wavelength band covering wavelengths of 300 nm to 500 nm in a reflectance spectrum in which the horizontal axis represents the surface reflectance and the back surface reflectance of the photomask blank. Is a curve convex downward, and the wavelength corresponding to the minimum value (bottom peak) of the surface reflectance and the back surface reflectance is located at 350 nm to 450 nm, according to Configuration 1 or 2. Photo mask blank.

(Configuration 4)
In the exposure wavelength of 365 nm to 436 nm, the wavelength dependency of the back surface reflectance is smaller than the wavelength dependency of the surface reflectance, and the photomask blank according to any one of Configurations 1 to 3. .

(Configuration 5)
7. The photomask blank according to any one of Configurations 1 to 4, wherein the surface reflectance is 10% or more in a wavelength range of 530 nm or more.

(Configuration 6)
The first reflection suppressing layer is a chromium-based material containing chromium, oxygen and nitrogen, and the content of chromium is 25 to 75 atomic%, the content of oxygen is 15 to 45 atomic%, and the content of nitrogen Have a composition of 10 to 30 atomic percent,
The light shielding layer is a chromium-based material containing chromium and nitrogen, and has a composition having a chromium content of 70 to 95 atomic% and a nitrogen content of 5 to 30 atomic%.
The second reflection suppressing layer is a chromium-based material containing chromium, oxygen and nitrogen, and the chromium content is 30 to 75 atomic%, the oxygen content is 20 to 50 atomic%, and the nitrogen content 7. The photomask blank of any one of arrangements 1 to 5, wherein the composition has a composition of 5 to 20 at%.

(Configuration 7)
The first reflection suppressing layer has a chromium content of 50 to 75 atomic%, an oxygen content of 15 to 35 atomic%, and a nitrogen content of 10 to 25 atomic%.
The second reflection suppressing layer has a chromium content of 50 to 75 atomic%, an oxygen content of 20 to 40 atomic%, and a nitrogen content of 5 to 20 atomic%. Photomask blank as described.

(Configuration 8)
7. The photomask blank according to Configuration 6 or 7, wherein the second reflection suppression layer is configured to have a higher oxygen content than the first reflection suppression layer.

(Configuration 9)
7. The photomask blank according to Configuration 6 or 7, wherein the first reflection suppression layer is configured to have a nitrogen content higher than that of the second reflection suppression layer.

(Configuration 10)
7. The photomask blank according to any one of aspects 1 to 9, wherein the transparent substrate is a rectangular substrate, and the short side length of the substrate is 850 mm or more and 1620 mm or less.

(Configuration 11)
11. The photo according to any one of constitutions 1 to 10, further comprising a semi-transparent film having an optical density lower than the optical density of the light shielding film between the transparent substrate and the light shielding film. Mask blank.

(Configuration 12)
11. The photomask blank according to any one of the aspects 1 to 10, further comprising a phase shift film for shifting the phase of transmitted light between the transparent substrate and the light shielding film.

(Configuration 13)
Providing the photomask blank described in any one of configurations 1 to 10;
Forming a resist film on the light shielding film, etching the light shielding film using the resist pattern formed from the resist film as a mask, and forming a light shielding film pattern on the transparent substrate;
A method of manufacturing a photomask, comprising:

(Configuration 14)
Providing the photomask blank described in configuration 11;
Forming a resist film on the light shielding film, etching the light shielding film using the resist pattern formed from the resist film as a mask, and forming a light shielding film pattern on the transparent substrate;
Etching the semi-transparent film using the light shielding film pattern as a mask to form the semi-transparent film pattern on the transparent substrate;
A method of manufacturing a photomask, comprising:

(Configuration 15)
Providing the photomask blank as described in configuration 12;
Forming a resist film on the light shielding film, etching the light shielding film using the resist pattern formed from the resist film as a mask, and forming a light shielding film pattern on the transparent substrate;
Etching the phase shift film using the light shielding film pattern as a mask to form the phase shift film pattern on the transparent substrate;
A method of manufacturing a photomask, comprising:

(Configuration 16)
A photomask obtained by the method of manufacturing a photomask described in any one of constitutions 13 to 15 is mounted on a mask stage of an exposure apparatus, and the light shielding film pattern formed on the photomask, A method of manufacturing a display device, comprising: an exposure step of exposing and transferring at least one mask pattern of a light transmitting film pattern and the phase shift film pattern onto a resist formed on a display substrate.

  According to the present invention, it is possible to obtain a photomask blank which is excellent in pattern accuracy and can manufacture a photomask having an optical characteristic that can suppress display unevenness in manufacturing a display device.

It is sectional drawing which shows schematic structure of the photomask blank concerning one Embodiment of this invention. 5 is a diagram showing the composition analysis result in the film thickness direction in the photomask blank of Example 1. FIG. FIG. 6 is a view showing reflectance spectra of front and back surfaces of the photomask blank of Example 1; 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, when forming a light shielding film by reactive sputtering.

  The inventors of the present invention have made it possible to suppress unevenness in display when manufacturing a display using a conventional photomask, the surface on the light shielding film side (hereinafter also referred to as the surface) of the photomask and the surface on the transparent substrate side (hereinafter We also focused on the reflectance spectrum of each of Each reflectance spectrum of front and back is a convex curve which differs in reflectance for every wavelength, and the reflectance becomes minimum in a specific wavelength zone. When the correlation between the reflectance spectrum and the display unevenness was examined, when both the surface reflectance and the back surface reflectance were small within the exposure wavelength range of 365 nm to 436 nm and the wavelength dependency of the back surface reflectance was small, display It has been found that the unevenness can be further suppressed.

  The wavelength dependency of the reflectance indicates that the reflectance varies depending on the exposure wavelength, and that the wavelength dependency is small means that the difference between the maximum value and the minimum value of the reflectance is small, that is, the reflectance Indicates that the amount of change (the range of fluctuation) is small.

So far, when pattern transfer is performed by irradiating exposure light onto the transfer substrate using a photomask, pattern accuracy is degraded due to the re-reflection exposure light from the light shielding film surface being transferred to the transfer substrate It was only considered to suppress the Therefore, only the surface reflectance was considered, but the back surface reflectance was not considered.
However, according to the study of the present inventor, in projection exposure using a photomask, the reflected light from the transferred substrate on which the photoresist is formed repeats reflection with the light shielding film pattern surface of the photomask. Light reflected from the back surface of the light-shielding film pattern is reflected by the optical system of the exposure apparatus (transfer apparatus) more than the influence of flare, and the return light that is incident again on the photomask has a large influence on the transfer pattern accuracy. Was found to occur easily. This is considered to be due to the fact that the reflection from the back surface of the light-shielding film pattern is larger than in the past due to the increase in size of the photo mask, the miniaturization of the pattern, and the high definition, and it has been recognized for the first time. In particular, in a photomask (for example, an ITO pattern, a slit pattern) in which the aperture ratio of the light shielding film pattern used in display panel fabrication is less than 50%, the influence of reflected light from the back surface of the light shielding film pattern in the photomask Becomes large, and display unevenness is likely to occur in a display panel manufactured using a photomask.

  As described above, since the back surface reflectance largely affects the display unevenness, the present inventors examined the mask blank from the viewpoint of the surface reflectance and the back surface reflectance. In the process, it was found that not only the reflectance of the front and back surfaces but also the wavelength dependency of the back surface reflectance affects the accuracy of the transfer pattern and the display unevenness. As a result of further examination, the surface reflectance and the back surface reflectance to exposure light are respectively 10% or less and the wavelength dependency of the back surface reflectance is 5% or less in the exposure wavelength range of 365 nm to 436 nm. When a photomask is manufactured by forming a mask blank, the reflected light from the back surface of the light shielding film pattern is reflected by the optical system of the exposure device (transfer device), and the return light is again incident on the photomask. It has been found that the display unevenness can be suppressed as compared with the case where a display device is manufactured using a conventional photomask.

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

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. The following embodiment is an embodiment for embodying the present invention, and the present invention is not limited to the scope. In the drawings, the same or corresponding parts will be denoted by the same reference numerals, and the description thereof may be simplified or omitted.

<Photo mask blank>
A photomask blank according to an embodiment of the present invention will be described. The photomask blank of this embodiment is, for example, light of a single wavelength selected from the wavelength band of 365 nm to 436 nm, or light of a plurality of wavelengths (for example, i ray (365 nm wavelength), h ray (405 nm), g ray (g ray) It is used when producing the photomask for display apparatus manufacture which exposes the composite light containing wavelength (436 nm). In addition, the numerical range represented using "-" in this specification means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit.

  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 is configured to include 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 formed of a material substantially transparent to exposure light, and is not particularly limited as long as it is a light transmitting substrate. As the transmittance for the exposure wavelength, a substrate material 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 a photomask for manufacturing a display device. For example, as the transparent substrate 11, it is a rectangular-shaped board | substrate, Comprising: The transparent substrate 11 whose magnitude | size of the short side is 330 mm-1620 mm can be used. For example, the transparent substrate 11 has a size of 330 mm × 450 mm, 390 mm × 610 mm, 500 mm × 750 mm, 520 mm × 610 mm, 520 mm × 800 mm, 800 × 920 mm, 850 mm × 1200 mm, 850 mm × 1400 mm, 1220 mm × 1400 mm, 1620 mm × 1780 mm And the like 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 a display device of G7 to G10 can be obtained.

(Light shielding film)
The light shielding film 12 is configured by laminating the first reflection suppression layer 13, the light shielding layer 14, and the second reflection suppression layer 15 in order from the transparent substrate 11 side. In the following, among the both sides of the photomask blank 1, the surface on the light shielding film 12 side is referred to as the front surface, and the surface on the transparent substrate 11 side is referred to as the back surface.

  When the first reflection suppressing layer 13 is provided on the surface of the light shielding film 12 on the side closer to the transparent substrate 11 in the light shielding film 12 and the pattern transfer is performed using a photomask manufactured using the photomask blank 1 And the side closer to the exposure device (exposure light source). When an exposure process is performed using a photomask, exposure light is irradiated from the transparent substrate 11 side (rear surface side) of the photomask, and a pattern transfer image is formed on a resist film formed on a display device substrate which is a transfer target. It will be transferred. At this time, the exposure light reflected on the back side of the light shielding film pattern is incident on the optical system of the exposure apparatus and is again incident from the side of the transparent substrate 11 of the photomask to form a light shielding film pattern. It becomes stray light of the mask pattern and causes deterioration of the transferred image such as formation of ghost image and increase of flare amount, and display unevenness is caused by irradiation of exposure light more than expected in the vicinity of overlay of display device substrates. You may The first reflection suppressing layer 13 can suppress reflection of exposure light on the back surface side of the light shielding film 12 when pattern transfer is performed using a photomask, so that deterioration of the transferred image is suppressed to improve transfer characteristics. As a result, it is possible to suppress the occurrence of display unevenness due to irradiation of exposure light more than expected in the vicinity of the overlapping of the display device substrates.

  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 so that the light shielding film 12 has an optical density to be 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 suppressing layer 15 is provided on the surface of the light shielding layer 12 on the side far from the transparent substrate 11 in the light shielding film 12. The second reflection suppression layer 15 has a resist film formed thereon, and when a predetermined pattern is drawn on the resist film by drawing light (laser light) of a drawing device (for example, a laser drawing device), the second reflection suppression layer 15 Since reflection on the surface side can be suppressed, CD uniformity of a resist pattern and a mask pattern formed based thereon can be enhanced. When the second reflection suppression layer 15 is used as a photomask, the second reflection suppression layer 15 is disposed on the display device substrate side, which is a transfer target, and the light reflected by the transfer target is the surface side of the light shielding film 12 of the photomask. Is suppressed again to be returned to the transfer target, and the deterioration of the transferred image is suppressed to contribute to the improvement of the transfer characteristics, and in the vicinity of the overlapping of the display device substrates, exposure light more than expected is irradiated. It is possible to suppress the occurrence of display unevenness due to

(Optical characteristics of photomask blank)
As described above, in the photomask blank 1, the surface reflectance and the back surface reflectance to exposure light are each 10% or less and the wavelength dependency of the back surface reflectance is 5% within the range of the exposure wavelength of 365 nm to 436 nm. It has the following optical characteristics. Here, the wavelength dependency of the back surface reflectance means the difference between the maximum value and the minimum value of the back surface reflectance within the range of the exposure wavelength of 365 nm to 436 nm. Specifically, the reflectance spectrum of the surface obtained by irradiating the surface of the photomask blank 1 with light has a surface reflectance of 10% or less within the range of the exposure wavelength of 365 nm to 436 nm. Preferably, the surface reflectance is 7.5% or less, more preferably 5% or less, in the range of the exposure wavelength of 365 nm to 436 nm. Similarly, in the reflectance spectrum of the back surface obtained by irradiating light to the back surface, the back surface reflectance is 10% or less within the range of the exposure wavelength of 365 nm to 436 nm. Preferably, in the wavelength range of the exposure wavelength of 365 nm to 436 nm, the back surface reflectance is preferably 7.5% or less, more preferably 5% or less. And the wavelength dependency of back surface reflectance is 5% or less in the range of exposure wavelength 365 nm-436 nm. In particular, in order to reduce display unevenness in the case of manufacturing a display device using a photomask, the wavelength dependency of the back surface reflectance may be 5% or less within the range of the exposure wavelength of 365 nm to 436 nm. is important. Preferably, the wavelength dependency of the back surface reflectance is 3% or less in the wavelength range of the exposure wavelength of 365 nm to 436 nm.

When the reflectance spectrum of front and back is compared with the photomask blank 1, it is preferable that back surface reflectance is smaller than surface reflectance over the whole range within the exposure wavelength of 365 nm-436 nm.
In addition, when manufacturing a plurality of photomask blanks capable of suppressing display unevenness, the photomask blank 1 has the surface reflectance and the back surface reflectance of the photomask blank as the vertical axis in order to stably produce a high yield. In the reflectance spectrum with the horizontal axis of wavelength, the reflectance spectrum is a downward convex curve in the wavelength band ranging from 300 nm to 500 nm, and corresponds to the minimum value (bottom peak) of surface reflectance and back surface reflectance It is preferable that the wavelength to be used is located at 350 nm to 450 nm.
Further, in the photomask blank 1, it is preferable that the wavelength dependency of the back surface reflectance be smaller than the wavelength dependency of the surface reflectance within the range of the exposure wavelength of 365 nm to 436 nm. Furthermore, from the viewpoint of detection accuracy in dimension measurement of the light-shielding film pattern in a photomask manufactured using the photomask blank 1, the photomask blank 1 has a surface reflectance of the light-shielding film in a wavelength range of 530 nm or more It is preferably 10% or more.

(Material of shading film)
Subsequently, materials of the respective layers in the light shielding film 12 will be described.
The material of each layer is not particularly limited as long as the above-mentioned optical properties can be obtained in the photomask blank 1, but from the viewpoint of obtaining the above-mentioned optical properties, the following materials are preferably used.
The first reflection suppressing layer 13 is preferably made of a chromium-based material containing chromium, oxygen and nitrogen. The oxygen in the first reflection suppression layer 13 has an effect of reducing the reflectance of the exposure light from the back surface side. Further, nitrogen in the first reflection suppression layer 13 has a cross section of a light shielding film pattern formed by etching (particularly wet etching) using a photomask blank, in addition to the effect of reducing the reflectance of exposure light from the back surface side. It brings the effect of improving the CD uniformity while bringing the Carbon or fluorine may be further contained from the viewpoint of controlling the etching characteristics.
The light shielding layer 14 is preferably 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 (in particular, wet etching) using a photomask blank to make the etching rate difference between the first reflection suppression layer 13 and the second reflection suppression layer 15 small. And the etching time of the light shielding film 12 (overall) is shortened, thereby improving the CD uniformity. Oxygen, carbon, and fluorine may be further contained from the viewpoint of controlling the etching characteristics.
The second reflection suppressing layer 15 is preferably made of a chromium-based material containing chromium, oxygen and nitrogen. The oxygen in the second reflection suppression layer 15 has an effect of reducing the reflectance of drawing light of the drawing device from the front side and the reflectance of exposure light from the front side. Further, the adhesion to the resist film is improved, and the side etching suppression effect by the penetration of the etchant from the interface between the resist film and the light shielding film 12 is exhibited. In addition, nitrogen in the second reflection suppression layer 15 is etched using a photomask blank (especially wet etching), in addition to the effect of reducing the reflectance of drawing light from the surface side and the reflectance of exposure light from the surface side. And the cross-section of the light-shielding film pattern formed by Carbon or fluorine may be further contained from the viewpoint of controlling the etching characteristics.

(Composition of shading film)
Subsequently, 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 a value measured by X-ray photoelectric spectroscopy (XPS).

  In the light shielding film 12, the first reflection suppressing layer 13 contains 25 to 75 atomic% of chromium (Cr), 15 to 45 atomic% of oxygen (O), and 10 to 30 atomic% of nitrogen (N). The light shielding layer 14 contains 70 to 95 atomic% of chromium (Cr) and 5 to 30 atomic% of nitrogen (N), and the second reflection suppression layer 15 has 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%. More preferably, the first reflection suppressing layer 13 contains 50 to 75 atomic percent of Cr, 15 to 35 atomic percent of O, and 5 to 25 atomic percent of N, respectively, and the second reflection suppressing layer 15 includes Cr. It contains 50 to 75 atomic percent, 5 to 40 atomic percent of O, and 5 to 20 atomic percent of N, respectively.

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

  The second reflection suppression layer 15 preferably has a region in which the O content rate increases toward the light shielding layer 14 in the film thickness direction.

  The second reflection suppression layer 15 preferably has a region in which the N content decreases toward the light shielding layer 14 in the film thickness direction.

  Further, it is preferable that the first reflection suppressing layer 13 have a region in which the N content rate decreases as the O content rate increases toward the transparent substrate 11 in the film thickness direction.

  In addition, in the photomask blank 1 and the photomask manufactured therefrom, the second reflection suppressing layer 15 is the first reflection suppressing layer from the viewpoint of further reducing the reflectance of the front and back surfaces and reducing the difference between the reflectances. It is preferable to be comprised so that O content rate may become higher than the layer 13, and 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. Specifically, it is preferable to make the O content of the second reflection suppression layer 15 larger than that of the first reflection suppression layer 13 by 5 atomic% to 10 atomic% or more, and the N content of the first reflection suppression layer 13 It is preferable that the second reflection suppressing layer 15 be larger by 5 atomic% to 10 atomic% or more. In the case where the first reflection suppressing layer 13 and the second reflection suppressing layer 15 have a composition inclination region, the O content and the N content indicate the average concentration in the film thickness direction.

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

(About the bonding state (chemical state))
The light shielding layer 14 preferably contains chromium (Cr) and dichromium nitride (Cr ₂ N).
The first reflection suppressing layer 13 and the second reflection suppressing layer 15 preferably contain chromium mononitride (CrN), chromium (III) oxide (Cr ₂ O ₃ ) and chromium (VI) oxide (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 may be appropriately adjusted according to the optical density and reflectance required of the light shielding film 12. It is good to do. The thickness of the first reflection suppression layer 13 corresponds to the reflection of light from the back surface side of the light shielding film 12 on the surface of the first reflection suppression layer 13 and the interface between the first reflection suppression layer 13 and the light shielding layer 14. The thickness may be such that the light interference effect due to the reflection is exhibited. On the other hand, the thickness of the second reflection suppression layer 15 is the reflection of light from the surface side of the light shielding film 12 on 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 It is sufficient that the thickness is such that the light interference effect due to the reflection of light 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, for example, the film thickness of the first reflection suppressing layer 13 is 15 nm to 60 nm from the viewpoint of setting the optical density to 3.0 or more while setting the reflectance of the front and back surfaces to 10% or less in the light shielding film 12. The thickness of the light shielding layer 14 may be 50 nm to 120 nm, and the thickness of the second reflection suppression layer 15 may be 10 nm to 60 nm.

<Method of Manufacturing Photomask Blank>
Then, the manufacturing method of the photomask blank 1 mentioned above is demonstrated.

(Preparation process)
A transparent substrate 11 substantially transparent to exposure light is prepared. The transparent substrate 11 may be subjected to an optional processing step such as a grinding step and a polishing step as necessary so as to have a flat and smooth main surface. After polishing, cleaning may be performed to remove foreign matter and contamination on the surface of the transparent substrate 11. As the washing, for example, sulfuric acid, sulfuric acid-hydrogen peroxide (SPM), ammonia, ammonia-hydrogen peroxide (APM), OH radical washing water, ozone water, warm water or the like can be used.

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

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

  As the metal mode conditions for forming the first reflection suppression layer 13, for example, the flow rate of oxygen-based gas is 5 to 45 sccm, the flow rate of nitrogen-based gas is 30 to 60 sccm, and the flow rate of rare gas is 60 to 150 sccm. It is good to do. In addition, the target applied power may be 2.0 to 6.0 kW, and the target applied voltage may be 360 to 460 V.

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

  In the present embodiment, the flow rate of the reactive gas and the power applied to the sputtering target are set to the conditions for the metal mode, and the film formation process by reactive sputtering is performed using the sputtering target containing Cr, thereby the transparent substrate A first reflection suppressing layer 13 is formed on each of 11 at a content of 25 to 75 atomic percent of Cr, 15 to 45 atomic percent of O, and 10 to 30 atomic percent of N, respectively.

  When the first reflection suppression layer 13 is formed as a single film whose composition is uniform in the film thickness direction, the film may be formed without changing the type or flow rate of the reactive gas, but the O content in the film thickness direction When making composition inclination so that a rate and N content rate change, it is good to change suitably a kind and flow rate of reactive gas, a ratio of oxygen system gas in nitrogen, reactive gas, etc., etc. In addition, the arrangement of the gas supply ports, the gas supply method, and the like may be changed.

(Step of forming the light shielding layer)
Subsequently, the light shielding layer 14 is formed on the first reflection suppression layer 13. In this formation, film formation is performed by reactive sputtering using a sputtering target containing Cr and a sputtering gas containing a nitrogen-based gas and a rare gas. At this time, as the film forming condition, the flow rate at which the flow rate of the reactive gas contained in the sputtering gas is in the metal mode is selected.
The target may be any one containing Cr. For example, in addition to chromium metal, chromium-based materials such as chromium oxide, chromium nitride, and chromium oxynitride can be used. Nitrogen (N ₂ ) or the like can be used as the nitrogen-based gas. As the noble gas, for example, helium gas, neon gas, argon gas, krypton gas, xenon gas, or the like can also be used. In addition to the reactive gas, the above-described oxygen-based gas and hydrocarbon-based gas may be supplied.
In the present embodiment, the flow rate of the reactive gas and the power applied to the sputtering target are set to the conditions to be the metal mode, and reactive sputtering is performed using the sputtering target containing Cr, whereby the first reflection suppressing layer 13 is formed. The light shielding layer 14 is formed to contain 70 to 95 atomic percent of Cr and 5 to 30 atomic percent of N, respectively.

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

(Step of forming second reflection suppressing layer)
Subsequently, the second reflection suppression layer 15 is formed on the light shielding layer 14. In this formation, similarly to the first reflection suppression layer 13, the flow rate of the reactive gas and the power applied to the target are set to such conditions as to be the metal mode, and a film is formed by reactive sputtering using a sputtering target containing Cr. I do. As a result, the second reflection suppressing layer 15 is formed on the light shielding layer 14 containing 30 to 75 atomic percent of Cr, 20 to 50 atomic percent of O, and 5 to 20 atomic percent of N, respectively.

  As conditions of the metal mode for forming the second reflection suppressing layer 15, for example, the flow rate of oxygen-based gas is 8 to 45 sccm, the flow rate of nitrogen-based gas is 30 to 60 sccm, and the flow rate of rare gas is 60 to 150 sccm. It is good to do. In addition, the target applied power may be 2.0 to 8.0 kW, and the target applied voltage may be 420 to 460 V.

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

  Thus, the photomask blank 1 of the present embodiment is obtained.

  Note that the film formation of each layer in the light shielding film 12 may be performed in-situ using an in-line sputtering apparatus. If it is not the in-line type, it is necessary to take out the transparent substrate 11 out of the apparatus after film formation of each layer, and the transparent substrate 11 may be exposed to the atmosphere to cause surface oxidation and surface carbonization of each layer. As a result, the reflectance to the exposure light of the light shielding film 12 and the etching rate may be changed. In this point, in the case of the in-line type, since it is possible to form the layers continuously without taking the transparent substrate 11 out of the apparatus and exposing it to the air, it is possible to suppress unintended uptake of elements into the light shielding film 12 .

  In the case of forming the light shielding film 12 using an in-line sputtering apparatus, a composition inclination region (in which the composition inclination is continuously performed between the first reflection suppression layer 13, the light shielding layer 14, and the second reflection suppression layer 15) Since it has a transition layer, it is preferable because the cross section of the light shielding film pattern formed by etching (particularly wet etching) using a photomask blank can be made smooth and close to vertical.

<Method of manufacturing photo mask>
Then, the method to manufacture a photomask using the photomask blank 1 mentioned above is demonstrated.

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

(Step of forming resist pattern)
Subsequently, a predetermined pattern is drawn on the resist film using a drawing apparatus. Usually, a laser drawing apparatus is used when producing a photomask for display device manufacture. 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 reduced, the reflection of drawing light (laser light) can be reduced when drawing a pattern on a resist film. As a result, 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. The etching may be wet etching or dry etching. Usually, in a photomask for manufacturing a display device, wet etching is performed, and as an etching solution (etchant) used in the wet etching, for example, a chromium etching solution containing ceric ammonium nitrate and perchloric acid is used be able to.

  In the present embodiment, 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 uniform in the thickness direction of the light shielding film 12. Therefore, the cross-sectional shape of the light shielding film pattern (mask pattern) can be made close to perpendicular to the transparent substrate 11, and high CD uniformity can be obtained.

(Peeling process)
Subsequently, the resist pattern is peeled off to obtain a photomask having a light shielding film pattern (mask pattern) formed on the transparent substrate 11.

  Thus, the photomask according to the present embodiment is obtained.

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

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

(Exposure process (pattern transfer process))
Next, a resist exposure step of transferring a pattern onto a resist film formed on a substrate of a display device by irradiating exposure light onto a photomask is performed.
The exposure light is, for example, light of a single wavelength (i-line (wavelength 365 nm), h-line (wavelength 405 nm), g-line (wavelength 436 nm), etc.) selected from the wavelength band of 365 nm to 436 nm, or light of a plurality of wavelengths For example, composite light including i-line (wavelength 365 nm), h-line (405 nm), g-line (wavelength 436 nm) is used. If a large photomask is used, it is preferable to use complex light as the exposure light from the viewpoint of the light amount.
In this embodiment, a display device (display panel) is manufactured using a photomask in which the reflectance of the front and back surfaces of the light shielding film pattern (mask pattern) is reduced and the reflectance dependence of the back surface reflectance is reduced. Therefore, a display device (display panel) without display unevenness can be obtained.

<Effect of this embodiment>
According to this embodiment, one or more of the following effects can be obtained.

(A) In the photomask blank 1 of the present embodiment, the light shielding film 12 is formed by laminating the first reflection suppression layer 13, the light shielding layer 14 and the second reflection suppression layer 15, and the exposure wavelength range of 365 nm to 436 nm Both of the reflectances of the front and back surfaces are 10% or less, and the optical characteristics are such that the wavelength dependency of the back surface reflectance in the above wavelength range is 5% or less. According to such a photomask blank 1, when irradiating exposure light as a photomask, reflection of light on the front and back surfaces can be suppressed over the entire wavelength range of the exposure wavelength of 365 nm to 436 nm. The total amount of light can be reduced. In particular, since the back surface reflectance can be averaged low over the entire wavelength range with the back surface reflectance having a wavelength dependency of 5% or less, suppressing return light to the back surface of the photomask that greatly affects display unevenness. Can. As a result, it is possible to suppress display unevenness caused by the reflection of light on the front and back surfaces of the photomask when manufacturing a display device using the photomask.

(B) It is preferable that the back surface reflectance is smaller than the surface reflectance over the whole range of exposure wavelength 365 nm-436 nm of the photomask blank 1. Thereby, reflection of light can be suppressed over a wide wavelength band, and the total amount of light reflection can be further reduced.

(C) The reflectance spectrum of the photomask blank 1 is a reflectance spectrum in the wavelength band ranging from 300 nm to 500 nm in the reflectance spectrum with the surface reflectance and the back surface reflectance of the photomask blank 1 as the ordinate and the wavelength as the abscissa. Is a curve convex downward, and the wavelength corresponding to the minimum value (bottom peak) of the surface reflectance and the back surface reflectance is preferably located at 350 nm to 450 nm. Thereby, a plurality of photomask blanks capable of suppressing display unevenness can be stably manufactured with high yield.

(D) In the photomask blank 1, it is preferable that the wavelength dependency of the back surface reflectance is smaller than the wavelength dependency of the surface reflectance within the range of the exposure wavelength of 365 nm to 436 nm. That is, in the above wavelength range, it is preferable that the amount of change in back surface reflectance be smaller than the amount of change in surface reflectance. Thereby, it is possible to further suppress the return light on the back surface of the photomask, and to further reduce the display unevenness.

(E) The photomask blank 1 preferably has a surface reflectance of 10% or more in a wavelength range of 530 nm or more. Thereby, the detection accuracy in the dimension measurement of the light-shielding film pattern in the photomask produced using the photomask blank 1 can be improved.

(F) In the photomask blank 1, the first reflection suppressing layer 13 is a chromium-based material containing chromium, oxygen and nitrogen, and has a Cr content of 25 to 75 atomic% and an O content of 15 to 45 The light shielding layer 14 is a chromium-based material containing chromium and nitrogen and having a composition of 10% to 30% by atom and an N content of 70% to 95% by atom, and an N content Has a composition of 5 to 30 atomic percent, and the second reflection suppressing layer 15 is a chromium-based material containing chromium, oxygen and nitrogen, and has a Cr content of 30 to 75 atomic percent and an O content of It is preferable to be configured to have a composition of 20 to 50 atomic percent and an N content of 5 to 20 atomic percent. By making each layer into the above-mentioned composition, the reflectance of front and back of photomask blank 1 can be reduced, and each can be made easy to be 10% or less.

(G) Further, in the present embodiment, the etching rate is set by setting the layers 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 to the composition range shown in (d). The concentration of O to be reduced and N to increase the etching rate can be reduced, and the difference between the etching rates of the respective layers can be suppressed and made uniform. As a result, the cross-sectional shape of the photomask blank 1 when the light shielding film 12 is etched, that is, the cross-sectional shape of the mask pattern can be made close to 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 °. In addition, it is possible to suppress the etching residue of the first reflection suppression layer 13 or the erosion (so-called undercut) of the first reflection suppression layer 13 and the second reflection suppression layer 15 as well as making the cross-sectional shape close to perpendicular. . As a result, CD uniformity in a mask pattern (light shielding film pattern) can be improved, and a highly accurate mask pattern of 100 nm or less can be formed.

(H) Further, in the present embodiment, the light shielding film 12 has an etching time which is equal to that of the first reflection suppression layer 13, the light shielding layer 14, and the second reflection suppression layer 15 which constitute the light shielding film 12. The verticality of the cross-sectional shape can be stably secured regardless of the length and shortness, the density of the etching solution, and the temperature of the etching solution. For example, when the just etching time of the light shielding film 12 is T, even if the etching time is 1.5 × T and the overetching is performed, the verticality equivalent to the etching time 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, in the case where the concentration of the etching solution is increased and in the case where 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. The just etching time indicates the etching time until the light shielding film 12 is etched in the film thickness direction and the surface of the transparent substrate 11 starts to be exposed.

(I) In the light shielding film 12, the first reflection suppressing layer 13 and the second reflection suppressing layer 15 are chromium-based materials containing chromium, oxygen and nitrogen, and the first reflection suppressing layer 13 is made of 50% Cr. The second reflection suppression layer 15 contains 50 to 75 atomic% of Cr and 20 to 40 atomic% of O at a content of -75 atomic%, 15 to 35 atomic% of O, and 10 to 25 atomic% of N, respectively. And N at a content of 5 to 20 at%, respectively.

  By further reducing the O content in the first reflection suppression layer 13 and the second reflection suppression layer 15, it is possible to suppress an excessive decrease in the etching rate due to the inclusion of O in these layers. Therefore, the content 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 content of Cr in the light shielding layer 14 can be increased, and the optical density (OD) can be maintained high.

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

(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, it is preferable that the O content of the second reflection suppression layer 15 be larger than that of the first reflection suppression layer 13 by 5 atomic% to 10 atomic% or more. The first reflection suppression layer 13 is preferably configured to have a higher N content than the second reflection suppression layer 15. Specifically, it is preferable that the N content of the first reflection suppression layer 13 be larger than that of the second reflection suppression layer 15 by 5 atomic% to 10 atomic%. According to the study of 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 surface side is higher than that on the back surface side despite the same composition. It turned out that it tends to be higher. Then, when the composition ratio (O content ratio, N content ratio) of each layer of the first reflection suppression layer 13 and the second reflection suppression layer 15 was further examined, the composition ratio of the first reflection suppression layer 13 and the second reflection suppression layer 15 It was found that by making (O content rate, N content rate) as described above, the reflectance on the back surface side can be reduced to the same level as that on the surface side or more than on the surface side. Thus, the reflectance of front and back can be controlled by changing the composition ratio (O content, N content) of each layer.

(K) In the first reflection suppressing layer 13 and the second reflection suppressing layer 15, the content of at least one of O and N changes in composition continuously or stepwise along the film thickness direction. It is preferred to have a region. By changing the composition of each layer of the first reflection suppressing layer 13 and the second reflection suppressing layer 15, the average of O or N in each layer is obtained while locally introducing a region in which the content of O or N is high in each layer. Content can be kept low. Thereby, the reflectance on the front surface side and the back surface side of the photomask blank 1 can be maintained low.

  In each of the first reflection suppressing layer 13, the light shielding layer 14, and the second reflection suppressing layer 15 constituting the light shielding film 12, when the O content increases, the etching rate decreases excessively or the N content increases. Although the etching rate may increase excessively, by reducing the content of O and N, it is possible to suppress the difference in etching rate of each layer by containing these elements. That is, the separation of the etching rate between the first reflection suppression layer 13 and the second reflection suppression layer 15 and the light shielding layer 14 can be suppressed. As a result, N and carbon contained in the light shielding layer 14 are 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. No carbon can be contained in 14 without containing carbon. As a result, the content of Cr in the light shielding layer 14 can be increased, and the optical density (OD) can be maintained high.

(L) The second reflection suppression layer 15 preferably has a region in which the O content rate increases toward the light shielding layer 14 in the film thickness direction. As a result, in the second reflection suppression layer 15, the O content in the interface with the light shielding layer 14 is locally increased, and the average O content in the film thickness direction is reduced. As a result, it is possible to obtain a desired reflectance on the surface side (the second reflection suppressing layer 15) of the light shielding film 12 and to suppress erosion due to excessive etching at the interface.

(M) It is preferable that the second reflection suppressing layer 15 have a region in which the N content decreases toward the light shielding layer 14 in the film thickness direction. Thereby, in the second reflection suppression layer 15, the N content in the interface portion with the light shielding layer 14 is locally lowered while maintaining the average N content in the film thickness direction to some extent. As a result, it is possible to suppress erosion due to excessive etching at the interface between the second reflection suppressing layer 15 and the light shielding layer 14.

(N) It is preferable that the first reflection suppressing layer 13 has a region in which the O content rate increases and the N content rate decreases toward the transparent substrate 11 in the 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. . As a result, it is possible to suppress corrosion at the interface between the first reflection suppressing layer 13 and the transparent substrate 11 and to further improve the CD uniformity of the mask pattern.

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

(P) Further, according to the present embodiment, the first reflection suppression layer 13 and the second reflection suppression layer 15 are made of chromium mononitride (CrN), chromium oxide (III) (Cr ₂ O ₃ ) and chromium oxide (VI) It is preferable to use a chromium-based material in a bonded state (chemical state) containing (CrO ₃ ). 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 reflectances of the front and back surfaces of the light shielding film 12 can be effectively reduced. it can. In addition, since the first reflection suppressing layer 13 and the second reflection suppressing layer 15 contain chromium nitride of CrN, excessive reduction of the etching rate by the above-mentioned chromium oxide can be suppressed, so that the cross section of the light shielding film pattern The shape can be made close to vertical.

(Q) Further, according to the present embodiment, the first reflection suppression layer 13 and the second reflection suppression layer 15 are formed of a sputtering target containing Cr, and a sputtering gas containing an oxygen-based gas, a nitrogen-based gas and a rare gas. The film formation by reactive sputtering used is performed, and the light shielding layer 14 is formed by reactive sputtering using a sputtering target containing Cr, a sputtering gas containing a nitrogen-based gas and a rare gas, and these reactive sputtering It is preferable to select a flow rate at which the flow rate of the reactive gas contained in the sputtering gas is in the metal mode as the film formation condition of the above. Thus, each layer of the first reflection suppressing layer 13, the light shielding layer 14, and the second reflection suppressing layer 15 constituting the light shielding film 12 can be easily adjusted to the above composition range, and the reflectance of the front and back of the light shielding film 12 is effective. The cross-sectional shape of the light-shielding film pattern when patterning the light-shielding film 12 can be made close to vertical while being reduced.

(R) It is preferable to use oxygen (O ₂ gas) as an oxygen-based gas when forming the layers of the first reflection suppression layer 13 and the second reflection suppression layer 15 by reactive sputtering. According to the O ₂ gas, since the oxidizing power is higher than that of other oxygen-based gas, each layer can be surely adjusted by the above composition range even in the case of forming a film by selecting the metal mode. Thereby, the cross-sectional shape of the light shielding film pattern when patterning the light shielding film 12 can be made to approach perpendicular perpendicularly, reducing the reflectance of front and back of the light shielding film 12 effectively.

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

(T) The photomask manufactured from the photomask blank 1 of the present embodiment has high precision in the light shielding film pattern and the reflectance of the front and back surfaces of the light shielding film pattern is reduced. At the time of pattern transfer, high transfer characteristics can be obtained.

(U) In the present embodiment, even when the photomask blank 1 is enlarged using a rectangular substrate having a short side length of 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.

Other Embodiments
As mentioned above, although one Embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, It can change suitably in the range which does not deviate from the summary.

Although the above-mentioned embodiment demonstrated the case where the light shielding film 12 was directly provided on the transparent substrate 11, this invention is not limited to this. For example, it may be a photomask blank in which a semi-transmissive film having an optical density lower than that of the light shielding film 12 is provided between the transparent substrate 11 and the light shielding film 12. Even in the photomask blank in which the semitransparent film and the light shielding film 12 are formed on the transparent substrate 11, the back surface reflectance of the semitransparent film to the exposure light is 10% or less within the exposure wavelength range of 365 nm to 436 nm. It is preferable that the surface reflectance of the light shielding film is 10% or less, and the wavelength dependency of the back surface reflectance of the semitransparent film in the wavelength range is 5% or less. This photomask blank can be used as a gray tone mask or a photomask blank for a gradation mask that has the effect of reducing the number of photomasks used in display device manufacture. The mask pattern in this gray tone mask or gradation mask is a semi-transparent film pattern and / or a light shielding film pattern.
Further, instead of the semi-transparent film, a photomask blank may be used 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. Also in the photomask blank in which the phase shift film and the light shielding film 12 are formed on the transparent substrate 11, the back surface reflectance of the phase shift film to the exposure light is 10% or less within the range of the exposure wavelength 365 nm to 436 nm. Preferably, the surface reflectance of the light shielding film is 10% or less, and the wavelength dependency of the back surface reflectance of the semitransparent film in the wavelength range is 5% or less. This photomask blank can be used as a phase shift mask having the effect of high pattern resolution by 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 to a chromium-based material which 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 further oxygen, nitrogen, A material containing at least one of carbon and fluorine is suitable. For example, metal silicides such as MoSi, ZrSi, TiSi and TaSi, oxides of metal silicides, nitrides of metal silicides, oxynitrides of metal silicides, carbonitrides of metal silicides, carbides of metal silicides, carbides of metal silicides Oxidized nitride is suitable. The semi-transparent film or the phase shift film may be a laminated film composed of the above-mentioned films listed as the functional film.

  Moreover, although the above-mentioned embodiment demonstrated the case where both the 1st reflection suppression layer 13 and the 2nd reflection suppression layer 15 were each one layer, this invention is not limited to this. For example, each layer may be a plurality of two or more layers.

  In the above-described 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 a light shielding film and an etching selectivity 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 to a chromium-based material which is a material of the light shielding film 12. Such materials include metal silicide materials containing molybdenum (Mo), zirconium (Zr), titanium (Ti), tantalum (Ta) and silicon (Si), Si, SiO, SiO ₂ , SiON, Si Silicon-based materials such as ₃ N ₄ can be mentioned.

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

Example 1
In the present example, the first reflection suppression layer, the light shielding layer, and the first on a transparent substrate having a substrate size of 1220 mm × 1400 mm as shown in FIG. 1 according to the procedure described in the above-described embodiment using an inline sputtering apparatus. Two reflection suppression layers were laminated to produce a photomask blank provided with a light shielding film.

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

The deposition conditions for the light shielding layer are a sputtering target of Cr sputtering target, and a flow rate of reactive gas is a metal mode, such as a flow rate of nitrogen (N ₂ ) gas, 1 to 60 sccm, and a flow rate of argon (Ar) gas 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 370 to 380 V. In addition, the board | substrate conveyance speed in the case of film-forming of the light shielding layer was 200 mm / min.

Conditions for forming the second antireflection layer, a sputter target and Cr sputter target, the flow rate of the reactive gas, so that the metal mode, oxygen _{(O 2)} 8~45sccm the flow rate of the gas, nitrogen _{(N 2} ) The flow rate of gas is selected in the range of 30 to 60 sccm, and the flow rate of argon (Ar) gas is selected in the range of 60 to 150 sccm, and the target applied power is in the range of 2.0 to 6.0 kW, and the target applied voltage is in the range of 420 to 430 V Set. In addition, the board | substrate conveyance speed in the case 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 a light shielding film has a composition distribution shown in FIG. FIG. 2 is a view showing the composition analysis result in the film thickness direction in the photomask blank of Example 1. The horizontal axis shows the sputtering time, and the vertical axis shows the content [atomic%] of the element. Sputtering time represents the depth from the surface of the light shielding film.

In FIG. 2, the region from the surface to a depth of about 5 minutes is a surface natural oxide layer, and the region from a depth of about 5 minutes to a depth of about 16 minutes is a second reflection suppression layer, and the depth from about 16 minutes to a depth of about The area up to 40 min is a transition layer, the area from about 40 min to about 97 min is a light shielding layer, the area from about 97 min to about 124 min is a transition layer, and the depth is about 124 min The region from the depth of about 132 min to the depth of about 132 min is the first reflection suppression layer, and the region from the depth of about 132 min is the transparent substrate.
The thickness of the light shielding film measured by a film thickness meter is 198 nm, and the thickness of each of the surface natural oxide layer, the second reflection suppression layer, the transition layer, the light shielding layer, the transition layer, and the first reflection suppression layer 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 contains 55.4 atomic% of Cr, 20.8 atomic% of N, and 23.8 atomic% of O. The content rates of these elements are measured in the portion where N peaks in the first reflection suppression layer (the region where the sputtering time is 123 minutes). The first reflection suppressing layer has a gradient composition as shown in FIG. 2 and has a portion where the O content increases and the N content decreases toward the transparent substrate in the film thickness direction. In the first reflection suppression layer, the content of each element averaged in the film thickness direction was 57 atomic% of Cr, 18 atomic% of N, and 25 atomic% of O.

  The light shielding layer is a CrN film, and contains 92.0 at% of Cr and 8.0 at% of N. The content rates of these elements are measured at the central portion (area with a sputtering time of 69 min) in the film thickness direction of the light shielding layer. In the light shielding layer, the content of each element averaged in the film thickness direction was 91 atomic% of Cr and 9 atomic% of N.

  The second reflection suppression layer is a CrON film, and contains 50.7 atomic% of Cr, 12.2 atomic% of N, and 37.1 atomic% of O. The contents of these elements are measured in the central portion of the region where O is increasing (the region with a sputtering time of 16 min) in the second reflection suppression layer. The second reflection suppressing layer has a gradient composition as shown in FIG. 2 and has a portion in which the O content rate increases and the N content rate decreases toward the light shielding layer side in the film thickness direction. In the second reflection suppression layer, the content of each element averaged in the film thickness direction was 52 atomic percent of Cr, 17 atomic percent of N, and 31 atomic percent of O. In addition, a surface natural oxide layer is formed on the surface of the second reflection suppressing layer by being exposed to the air, and this layer is oxidized or carbonized, so that the O content rate and the C content rate are detected high it is conceivable that.

Moreover, the spectrum analysis was performed based on the XPS measurement result about the coupling 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 reflection suppression layer and the second reflection suppression layer contain chromium mononitride (CrN), chromium (III) oxide (Cr ₂ O ₃ ) and chromium (VI) oxide (CrO ₃ ), and chromium and oxygen And a nitrogen-containing chromium-based material (chromium compound). 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)
With respect to 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 methods described below.

The optical density of the light-shielding film of the photomask blank of Example 1 was measured with a spectrophotometer (“SolidSpec-3700” manufactured by Shimadzu Corporation). As a result, the g-line (wavelength 436 nm), which is the wavelength band of exposure light, was measured. It was 5.0. Moreover, the reflectance of front and back of a light shielding film was measured by the spectrophotometer ("SolidSpec-3700" by Shimadzu Corp. make). Specifically, the reflectance (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 each measured by 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 represents wavelength [nm] and the vertical axis represents reflectance [%].
As shown in FIG. 3, in the photomask blank of Example 1, the bottom peak wavelength of the reflectance spectrum of the front and back surfaces can be made to be around 436 nm, and the reflectance can be greatly reduced for light of a wide wavelength. 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)), 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 of the light shielding film can be reduced to 10% or less at a wavelength of 365 nm to 436 nm. Especially for the light with a wavelength of 436 nm, the surface reflectance is 0.3% and the back reflectance is 4.8%. It was confirmed that it was possible.
Moreover, the dependence of the surface reflectance of the light shielding film in the range of the exposure wavelength of 365 nm to 436 nm was 7.4%, and the dependence of the back surface reflectance was 1.6%.
The surface reflectance of the light-shielding film at a wavelength of 530 nm was 11.8%.
In a wavelength band ranging from 300 nm to 500 nm, the wavelength (bottom peak wavelength) corresponding to the minimum value (bottom peak) of the surface reflectance and the back surface reflectance is 436 nm for the surface reflectance and 415.5 nm for the back surface reflectance there were.

(Evaluation of shading film pattern)
The photomask blank of Example 1 was used to form a light shielding film pattern on a transparent substrate. Specifically, after forming a novolak positive resist film on a light shielding film on a transparent substrate, a laser drawing (wavelength: 413 nm) / development was performed to form a resist pattern. 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 made close to perpendicular. FIG. 4 is a view for explaining the verticality 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 is based on the just etching time (JET) (100%). The cross-sectional shapes when over-etched are shown as 110%, 130%, and 150%, respectively. In FIG. 4, the light shielding film pattern and the resist film pattern were stacked on the transparent substrate, and it was confirmed that the side surface of the light shielding film pattern makes an angle of 70 ° with the transparent substrate when JET is 100%. . This angle is within the range of 60 ° -80 ° even when the etching time is 110%, 130% and 150% of JET, and the cross-sectional shape of the light shielding film pattern does not depend on the etching time. It was confirmed that it can be stably formed vertically.

  As in Example 1 above, with respect to the light shielding film of the photomask blank, 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 is configured to have 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 vertically formed.

(Production of photo mask)
Next, a photomask was produced using the photomask blank of Example 1.
First, a novolak positive resist was formed on the light shielding film of the photomask blank. Then, a pattern of a circuit pattern for the TFT panel was drawn on this resist film using a laser drawing apparatus, and further development and rinsing were performed to form a predetermined resist pattern (the minimum line width of the above-mentioned circuit pattern is 0.75 μm).
Thereafter, using the resist pattern as a mask, the light shielding film is patterned by wet etching using a chromium etching solution, and finally the resist pattern is peeled off by the resist peeling solution to form a light shielding film pattern (mask pattern) on the transparent substrate. The formed photomask was obtained. This photomask is an aperture ratio of a light shielding film pattern (mask pattern) formed on a transparent substrate, that is, a transparent substrate in which the light shielding film pattern is not formed on the entire area of the photomask on which the light shielding film pattern is formed. The exposure rate was 45%.
The CD uniformity of the light shielding film pattern of this photomask was measured by "SIR 8000" manufactured by Seiko Instruments Nano Technologies, Inc. The CD uniformity measurements were taken at 11 × 11 points on a 1100 mm × 1300 mm area excluding the peripheral area of the substrate.
As a result, the CD uniformity was 100 nm, and the CD uniformity of the obtained photomask was good.

(Production of LCD panel)
The photomask manufactured in this Example 1 is set on the mask stage of an exposure apparatus, and pattern exposure is performed on a transfer target having a resist film formed on a substrate for a display device (TFT) to manufacture a TFT array. did. As the exposure light, composite light including i-line of wavelength 365 nm, h-line of wavelength 405 nm, and g-line of wavelength 436 nm was used.
A TFT-LCD panel was manufactured by combining the manufactured TFT array, a color filter, a polarizing plate, and a backlight. As a result, a TFT-LCD panel without display unevenness was obtained. This is considered to be because, when pattern exposure was performed using a photomask, reflection of light on the front and back surfaces was suppressed, and the total light amount of the reflected light was reduced.

(Example 2)
In this example, the film formation conditions of the first reflection suppression layer and the film formation conditions of the second reflection suppression layer in Example 1 are changed as follows, and the first reflection is performed on a transparent substrate having a substrate size of 1220 mm × 1400 mm. A suppression layer, a light shielding layer, and a second reflection suppression layer were laminated to produce a photomask blank provided with a light shielding film.

The deposition condition of the first reflection suppression film is that the sputter target is a Cr sputter target, and the flow rate of the reactive gas is 25 to 45 sccm of oxygen (O ₂ ) gas so as to be in metal mode, nitrogen (N ₂₎ ) Select the flow rate of gas from 40 to 60 sccm, flow rate of argon (Ar) gas from 80 to 120 sccm, target applied power of 1.5 to 5.0 kW, target applied voltage of 380 to 400 V Set in. In addition, the board | substrate conveyance speed in the case of film-forming of a 1st reflection suppression layer was 300 mm / min.

In addition, as the film formation conditions of the second reflection suppression film, the sputter target is a Cr sputter target, the flow rate of the reactive gas is 8-25 sccm of oxygen (O ₂ ) gas, nitrogen ( The flow rate of N ₂ ) gas is selected from 30 to 40 sccm, the flow rate of argon (Ar) gas is selected from the range of 90 to 120 sccm, the target applied power is 3.5 to 8.0 kW, and the target applied voltage is 435 to 455 V Set in the range. In addition, the board | substrate conveyance speed in the case of film-forming of a 2nd reflection suppression layer was 250 mm / min.

(Evaluation of photomask blank)
With respect to the photomask blank of Example 2, the optical density of the light shielding film and the reflectance of the front and back surfaces of the light shielding film were evaluated in the same manner as in Example 1.
In the photomask blank of Example 2, the optical density of the light-shielding film was 5.1 at the g-line (wavelength 436 nm) which is the wavelength band of the exposure light. Moreover, it was confirmed that the bottom peak wavelength of the reflectance spectrum of front and back can be made into 400 nm vicinity, and a reflectance can be reduced large with respect to the light of a wide wavelength. Specifically, at a wavelength of 365 nm to 436 nm, the surface reflectance of the light shielding film is 7.5% or less (7.5% (365 nm), 4.9% (405 nm), 4.9% (413 nm) ), 6.3% (wavelength 436 nm)), the back surface reflectance of the light shielding film is 5% or less (2.8% (wavelength 365 nm), 1.6% (wavelength 405 nm), 3.9% (wavelength 436 nm) )Met. The reflectance of the front and back of the light shielding film can be reduced to 7.5% or less at a wavelength of 365 nm to 436 nm, and in particular, the reflectance for light with a wavelength of 405 nm is 4.9% for the surface reflectance and 1.6 for the back surface reflectance. It has been confirmed that it is possible to%.
Moreover, the dependence of the surface reflectance of the light shielding film in the range of the exposure wavelength of 365 nm to 436 nm was 2.6%, and the dependence of the back surface reflectance was 2.5%.
The surface reflectance of the light-shielding film at a wavelength of 530 nm was 22.8%.
In a wavelength band ranging from 200 nm to 500 nm, the wavelength (bottom peak wavelength) corresponding to the minimum value (bottom peak) of surface reflectance and back surface reflectance is 404 nm in surface reflectance and 394 nm in back surface reflectance .

(Production of photo mask)
Next, when the photomask blank of Example 2 was used to prepare a photomask in the same manner as in Example 1, the CD uniformity was 92 nm, and the CD uniformity of the obtained photomask was good. .

(Production of LCD panel)
The photomask prepared in Example 2 was set on the mask stage of an exposure apparatus, and pattern exposure was performed on a transfer target having a resist film formed on a substrate for a display device (TFT) to produce a TFT array. . As the exposure light, composite light including i-line of wavelength 365 nm, h-line of wavelength 405 nm, and g-line of wavelength 436 nm was used. A TFT-LCD panel was manufactured by combining the manufactured TFT array, a color filter, a polarizing plate, and a backlight. As a result, a TFT-LCD panel without display unevenness was obtained. This is considered to be because, when pattern exposure was performed using a photomask, reflection of light on the front and back surfaces was suppressed, and the total light amount of the reflected light was reduced.

(Example 3)
In the present example, a photomask is used in the same manner as in Example 1 except that the photomask blank of Example 1 is used to manufacture a photomask having a slit-like pattern having a light shielding film pattern width of 1.2 μm. Was produced. In the manufactured photomask, the aperture ratio of the light shielding film pattern formed on the transparent substrate was 38%.
The CD uniformity of the light shielding film pattern of this photomask was 82 nm, and the CD uniformity of the obtained photomask was good.
The photomask manufactured in Example 3 was set on the mask stage of the exposure apparatus, and pattern exposure was performed on a transfer target having a resist film formed on a substrate for a display device (TFT) to manufacture a TFT array. . As the exposure light, composite light including i-line of wavelength 365 nm, h-line of wavelength 405 nm, and g-line of wavelength 436 nm was used. A TFT-LCD panel was manufactured by combining the manufactured TFT array, a color filter, a polarizing plate, and a backlight. As a result, a TFT-LCD panel without display unevenness was obtained. This is considered to be because, when pattern exposure was performed using a photomask, reflection of light on the front and back surfaces was suppressed, and the total light amount of the reflected light was reduced.

(Example 4)
In the present example, a photomask blank was produced in the same manner as in Example 1 except that a phase shift film was formed between the transparent substrate and the light shielding film in the photomask blank of Example 1.
The phase shift film was formed as follows.
The film forming conditions of the phase shift film are reactive sputtering using a mixed gas of argon gas, nitrogen gas (N ₂ ) and nitrogen monoxide gas (NO) with a sputtering target being a MoSi sputter target (Mo: Si = 1: 4). Thus, a phase shift film of MoSiON with a thickness of 183 nm was formed. The gas flow rate of the mixed gas was 40 sccm of Ar gas, 34 sccm of N ₂ gas, and 34.5 sccm of NO gas. The phase shift film had a transmittance of 27% (wavelength: 405 nm) and a phase difference of 173 ° (wavelength: 405 nm).
Next, in the same manner as in Example 1, a light shielding film comprising a first reflection suppression layer, a light shielding layer, and a second reflection suppression layer was formed on the phase shift film, to prepare a photomask blank.

(Evaluation of photomask blank)
The back surface reflectance of the phase shift film in the photomask blank of Example 4 is 10.0% or less (4.2% (wavelength 365 nm), 6.2% (wavelength 405 nm), 9.2% (wavelength 436 nm) In addition, 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% The photomask blank of Example 4 can reduce the back surface reflectance of the phase shift film to 10% or less and the surface reflectance of the light shielding film to 10% or less at wavelengths 365 nm to 436 nm. Furthermore, the wavelength dependency of the back surface reflectance of the phase shift film was 5% or less.

(Production of photo mask and production of LCD panel)
Next, a photomask was manufactured using the photomask blank of Example 4.
First, a novolak positive resist was formed on the light shielding film of the photomask blank. Then, using a laser drawing apparatus, a hole-like pattern having a hole diameter of 1.2 μm was drawn on this resist film, and further development and rinsing were performed to form a first resist pattern.
Thereafter, the light shielding film was patterned by wet etching using a chromium etching solution using the first resist pattern as a mask to form a light shielding film pattern on the phase shift film.
Next, using the light shielding film pattern as a mask, the phase shift film was patterned by wet etching using a molybdenum silicide etching solution to form a phase shift film pattern. Thereafter, the first resist pattern was peeled off.
Thereafter, a resist film is formed so as to cover the light shielding film pattern, and the pattern is drawn using a laser drawing apparatus, and further development and rinsing are performed to form a light shielding zone on the phase shift film pattern. The resist pattern of
Thereafter, using the second resist pattern as a mask, the light shielding film is patterned by wet etching using a chromium etching solution to form a light shielding film pattern for a light shielding zone on the phase shift film, and finally, the second The resist film pattern was peeled off to prepare a photomask.
In this manner, a photomask was obtained in which a light shielding zone having a laminated structure of a phase shift film pattern having a hole diameter of 1.2 μm and a phase shift film pattern and a light shielding film pattern was formed on a transparent substrate.
The CD uniformity of the phase shift film pattern of this photomask was 90 nm, and the CD uniformity of the obtained photomask was good.
Moreover, as a result of producing TFT-CLD panel parent using the photomask produced in Example 4, the TFT-LCD panel without a display nonuniformity was obtained. This is considered to be because, when pattern exposure was performed using a photomask, reflection of light on the front and back surfaces was suppressed, and the total fragrance of reflected light could be reduced.

(Comparative example 1)
As a comparative example, the first reflection suppression layer, the light shielding layer, and the second reflection suppression layer were stacked on a transparent substrate having a substrate size of 1220 mm × 1400 mm to manufacture a photomask blank including a light shielding film.

Conditions for forming the first antireflection layer, a sputter target and Cr sputter target, the flow rate of the reactive gas, so that the reactive mode, 100～250Sccm the flow rate of carbon dioxide (CO _2), nitrogen _{(N 2} ) Select a gas flow rate of 150 to 350 sccm, a methane (CH ₄ ) gas flow rate of 0 to 15 sccm, and an argon (Ar) gas flow rate of 150 to 300 sccm, and apply a target applied power of 2.0 to 7 It was set within the range of 0 kW. In addition, the board | substrate conveyance speed in the case of film-forming of a 1st reflection suppression layer was 200 mm / min, and film-forming was performed 3 times.

The deposition conditions for the light shielding layer are a sputtering target of Cr sputtering target, and a flow rate of reactive gas is a metal mode, such as a flow rate of nitrogen (N ₂ ) gas, 1 to 60 sccm, and a flow rate of argon (Ar) gas 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 in the case of film-forming of the light shielding layer was 200 mm / min.

The film formation conditions for the second reflection suppression layer are such that the sputtering target is a Cr sputtering target, and the flow rate of the reactive gas is 100 to 300 for carbon dioxide gas (CO ₂ ) and nitrogen (N ₂ ) so as to be a reaction mode. ) Select a gas flow rate of 150 to 350 sccm, a methane (CH ₄ ) gas flow rate of 0 to 15 sccm, and an argon (Ar) gas flow rate of 150 to 300 sccm, and apply a target applied power of 2.0 to 7 It was set within the range of 0 kW. In addition, the board | substrate conveyance speed in the case of film-forming of a 2nd reflection suppression layer was 200 mm / min, and film-forming was performed 3 times.

The optical density of the light shielding film and the reflectance of the front and back surfaces of the light shielding film of the photomask blank of Comparative Example 1 were measured in the same manner as Example 1 described above. As a result, the optical density of the light-shielding film was 5.1 at the g-line (wavelength 436 nm) which is the wavelength band of the exposure light. In addition, the surface reflectance of the light shielding film is 5.0% or less (2.8% (wavelength 365 nm), 3.5% (wavelength 405 nm), 3.9% (wavelength 413 nm), at a wavelength of 365 nm to 436 nm, 4 .8% (wavelength 436 nm)), the back surface reflectance of the light shielding film is 12% or less (11.2% (wavelength 365 nm), 7.1% (wavelength 405 nm), 4.9% (wavelength 436 nm)) The The surface reflectance of the light shielding film could be 5% or less at wavelengths of 365 nm to 436 nm, but the back surface reflectance exceeded 10% and became 11.2% at wavelengths of 365 nm.
In addition, the surface reflectance dependency of the light shielding film in the range of the exposure wavelength of 365 nm to 436 nm was 2.0%, and the back surface reflectance dependency was 6.3%.
In the wavelength band ranging from 300 nm to 500 nm, the wavelength (bottom peak wavelength) with respect to the minimum value (bottom peak) of the surface reflectance and the back surface reflectance is 337 nm as the surface reflectance and 474 nm as the back surface reflectance.

(Production of photo mask)
Next, using the photomask blank of Comparative Example 1, a photomask was produced in the same manner as Example 1. As a result of measuring CD uniformity of the light shielding film pattern of the obtained photomask, it became 155 nm and it deteriorated compared with Example 1,2.
(Production of LCD panel)
The photomask manufactured in Comparative Example 1 was set on the mask stage of the exposure apparatus, and pattern exposure was performed on a transfer target having a resist film formed on a substrate for a display device (TFT) to manufacture a TFT array. . As the exposure light, composite light including i-line of wavelength 365 nm, h-line of wavelength 405 nm, and g-line of wavelength 436 nm was used. A TFT-LCD panel was manufactured by combining the manufactured TFT array, a color filter, a polarizing plate, and a backlight. As a result, it was confirmed that display unevenness occurs in the TFT-LCD panel manufactured using the photomask of Comparative Example 1. This is because the photomask of Comparative Example 1 can not sufficiently suppress the reflection of light especially at the back surface of the light shielding film at the exposure wavelength (365 nm to 436 nm) when performing pattern exposure, and as a result, the total of reflected light It is considered that the amount of light has increased.

REFERENCE SIGNS LIST 1 photomask blank 11 transparent substrate 12 light shielding film 13 first reflection suppression layer 14 light shielding layer 15 second reflection suppression layer

Claims (16)

A photomask blank for use in producing a photomask for display device manufacture, comprising:
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,
When the surface on the light shielding film side is the front surface and the surface on the transparent substrate side is the back surface of both sides of the photomask blank, the surface reflectance and the back surface reflection for the exposure light within the range of the exposure wavelength of 365 nm to 436 nm A photomask blank characterized in that the respective rates are 10% or less, and the wavelength dependency of the back surface reflectance in the wavelength range is 5% or less.   2. The photomask blank according to claim 1, wherein the back surface reflectance is smaller than the surface reflectance over the entire exposure wavelength range of 365 nm to 436 nm. The reflectance spectrum of the front surface and the back surface in a wavelength band covering wavelengths of 300 nm to 500 nm in a reflectance spectrum in which the horizontal axis represents the surface reflectance and the back surface reflectance of the photomask blank. Are respectively convex downward curves, and the wavelength corresponding to the minimum value (bottom peak) of the surface reflectance and the back surface reflectance is located at 350 nm to 450 nm.
The photomask blank according to claim 1 or 2, characterized in that:   The photomask according to any one of claims 1 to 3, wherein in the exposure wavelength range of 365 nm to 436 nm, the wavelength dependency of the back surface reflectance is smaller than the wavelength dependency of the surface reflectance. blank.   The photomask blank according to any one of claims 1 to 4, wherein the surface reflectance is 10% or more in a wavelength range of 530 nm or more. The first reflection suppressing layer is a chromium-based material containing chromium, oxygen and nitrogen, and the content of chromium is 25 to 75 atomic%, the content of oxygen is 15 to 45 atomic%, and the content of nitrogen Have a composition of 10 to 30 atomic percent,
The light shielding layer is a chromium-based material containing chromium and nitrogen, and has a composition having a chromium content of 70 to 95 atomic% and a nitrogen content of 5 to 30 atomic%.
The second reflection suppressing layer is a chromium-based material containing chromium, oxygen and nitrogen, and the chromium content is 30 to 75 atomic%, the oxygen content is 20 to 50 atomic%, and the nitrogen content The photomask blank according to any one of claims 1 to 5, wherein the composition has a composition of 5 to 20 atomic%. The first reflection suppressing layer has a chromium content of 50 to 75 atomic%, an oxygen content of 15 to 35 atomic%, and a nitrogen content of 10 to 25 atomic%.
The second reflection suppressing layer has a chromium content of 50 to 75 atomic%, an oxygen content of 20 to 40 atomic%, and a nitrogen content of 5 to 20 atomic%. Photomask blank as described in.   The photomask blank according to claim 6 or 7, wherein the second reflection suppression layer is configured to have a higher oxygen content than the first reflection suppression layer.   8. The photomask blank according to claim 6, wherein the first reflection suppression layer is configured to have a higher nitrogen content than the second reflection suppression layer.   The said transparent substrate is a rectangular-shaped board | substrate, Comprising: The short side length of this board | substrate is 850 mm-1620 mm, The photomask blank of any one of the Claims 1-9 characterized by the above-mentioned.   The semi-transparent film 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 light transmission film of any one of the Claims 1-10 characterized by the above-mentioned. Photo mask blank.   The photomask blank according to any one of claims 1 to 10, further comprising a phase shift film for shifting the phase of transmitted light between the transparent substrate and the light shielding film. Preparing the photomask blank according to any one of claims 1 to 10.
Forming a resist film on the light shielding film, etching the light shielding film using the resist pattern formed from the resist film as a mask, and forming a light shielding film pattern on the transparent substrate;
A method of manufacturing a photomask, comprising: Providing the photomask blank according to claim 11;
Forming a resist film on the light shielding film, etching the light shielding film using the resist pattern formed from the resist film as a mask, and forming a light shielding film pattern on the transparent substrate;
Etching the semi-transparent film using the light shielding film pattern as a mask to form the semi-transparent film pattern on the transparent substrate;
A method of manufacturing a photomask, comprising: Providing the photomask blank according to claim 12;
Forming a resist film on the light shielding film, etching the light shielding film using the resist pattern formed from the resist film as a mask, and forming a light shielding film pattern on the transparent substrate;
Etching the phase shift film using the light shielding film pattern as a mask to form the phase shift film pattern on the transparent substrate;
A method of manufacturing a photomask, comprising: The said light shielding film pattern which mounted the photomask obtained by the manufacturing method of the photomask as described in any one of Claims 13-15 on the mask stage of exposure apparatus, and was formed on the said photomask, A method of manufacturing a display device, comprising: an exposure step of exposing and transferring at least one mask pattern of a semi-translucent film pattern and the phase shift film pattern on a resist formed on a display substrate.