JP6594742B2 - Photomask blank, photomask manufacturing method using the same, and display device manufacturing method - Google Patents

Description

  The present invention relates to a photomask blank and a photomask, and in particular, a photomask blank (a blank for a photomask) for manufacturing an FPD device, a method for manufacturing a photomask (a transfer mask) using the photomask blank, The present invention also relates to a method for manufacturing a display device using a photomask manufactured by the manufacturing method.

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

  In a photomask for manufacturing a display device, in general, laser light having a wavelength of 413 nm or the like is used for mask pattern drawing from the viewpoint of increasing the fineness of the pattern used and the mask pattern drawing throughput. In order to form a mask pattern with high dimensional accuracy by laser drawing, a mask pattern (light-shielding film pattern) formed on a transparent substrate such as synthetic quartz is generally an exposure light for manufacturing a display device. The mask pattern light-shielding film has a laminated structure of a light-shielding layer that shields (exposure light used in lithography) and a reflection-reducing layer that reduces reflection of the laser drawing light. The reflection reduction layer formed on the light shielding layer suppresses the reflection of the laser drawing light, and it becomes possible to form a mask pattern with high dimensional accuracy.

  In order to manufacture such a display device with a high yield without pixel or circuit defects, a photomask to be used must have few defects. Photomask defects are broadly classified into foreign matter defects due to adhesion of foreign matter or contaminants (contamination) and mask pattern defects made of a light shielding film. Both of these defects must be small. Cleaning during the photomask manufacturing process is important for reducing foreign matter defects and contamination adhesion. Before forming a mask pattern formation resist on the photomask blank that is the original photomask, sulfuric acid or sulfuric acid is required. Cleaning before resist application (chemical cleaning) is performed using a cleaning solution containing sulfuric acid such as water, or a chemical solution such as an ozone cleaning solution. By performing pre-resist cleaning using such a cleaning solution containing sulfuric acid or an ozone cleaning solution, adhering foreign matter and contamination are removed, and in particular, ozone cleaning improves the adhesion of the resist, and resist film peeling failure and In addition, defective etching defects due to penetration of the etchant into the interface between the resist and the reflection reducing layer due to insufficient resist adhesion are prevented.

  On the other hand, in order to reduce mask pattern defects, it is necessary to reduce defects in the light shielding film itself as well as reduce defects in a series of pattern forming processes such as resist drawing, development, and etching on a photomask blank.

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

Japanese Patent No. 5004283

  As described above, pre-resist coating cleaning on the photomask blank with sulfuric acid-containing cleaning solution or ozone cleaning solution is performed for the purpose of preventing foreign object defects during the photomask manufacturing process. The reflection reduction layer formed on the surface of the photomask blank is damaged with an in-plane distribution, and the reflectivity with respect to laser light for drawing a mask pattern (hereinafter also referred to as drawing light) changes with an in-plane distribution. I understood. In particular, when performing pre-resist coating cleaning on a photomask blank with an ozone cleaning solution, it has been found that the reflectance with respect to laser light for mask pattern drawing changes greatly. Here, as described above, the reflection reducing layer absorbs exposure light (hereinafter referred to as exposure light, which is distinguished from the above-described drawing light) when performing exposure on the display device substrate, and is on the light shielding layer that shields light. The formed layer is for reducing the reflection of laser light for mask pattern writing and increasing the drawing accuracy. If there is reflection, the drawing accuracy is lowered due to the optical interference between the drawing light and the reflected light, which causes a reduction in drawing resolution and variations in drawing dimensions (mask pattern dimensions). When the reflectivity has an in-plane distribution, the drawing dimension (mask pattern dimension) also has an in-plane distribution, and the mask pattern dimension accuracy decreases.

  The cleaning before the resist coating on the mask blank with the cleaning solution containing sulfuric acid or the ozone cleaning solution described above is not limited to once, and the foreign matter is removed when the foreign matter is detected on the surface on which the resist is applied (reflection reducing layer surface). Repeat until washing. If there is a defect in the resist film, or there is a defect in the resist pattern formed by drawing and development, the resist is removed and the resist coating is started again (this process is called registry work). In this case, however, cleaning with a cleaning solution containing sulfuric acid or an ozone cleaning solution is performed again before applying the resist. It has been found that, by such repeated ozone cleaning before resist application, the reflectance change and reflectance in-plane distribution of the reflection reducing layer with respect to the laser drawing light further increase and the mask pattern dimensional accuracy is greatly reduced.

  As described above, it is possible to prevent a reduction in mask pattern dimensional accuracy due to a change in reflectance and a change in reflectance distribution caused by cleaning before application of a resist by a cleaning solution containing sulfuric acid or an ozone cleaning solution, and to form a mask pattern with high dimensional accuracy. However, this is the first problem targeted by the present invention.

  Further, as described above, in order to obtain a photomask with few defects, in addition to the resistance of a cleaning solution containing sulfuric acid and an ozone cleaning solution before resist coating, the mask pattern shading film itself has few defects. Must not. The second problem of the present invention is that it has a high resistance to cleaning before resist coating with a cleaning solution containing sulfuric acid or an ozone cleaning solution, and has a light shielding film for a mask pattern comprising a reflection reducing layer and a light shielding layer with few defects. It is to obtain a defective photomask blank and a photomask.

  Accordingly, an object of the present invention is to provide a photomask blank having a mask pattern light-shielding film with high resistance to cleaning before resist application using a cleaning solution containing sulfuric acid and ozone cleaning solution before resist coating, and having few defects, It is to provide a photomask having high dimensional accuracy and having few defects by manufacturing a photomask using the photomask blank. In addition, the present invention provides a method for manufacturing a high-definition display device with a high yield.

  In order to solve the above problems, the present invention has the following configuration.

(Configuration 1)
A photomask blank comprising a transparent substrate made of a material substantially transparent to exposure light, a light shielding layer on the transparent substrate, and a reflection reducing layer on the light shielding layer,
The light shielding layer is made of a chromium material containing chromium,
The reflection reduction layer is made of a chromium oxide material containing less oxygen than the light shielding layer and containing oxygen,
The reflection reducing layer is a laminated film in which a plurality of layers are laminated,
The photomask blank, wherein the oxygen content on the light shielding layer side is equal to or higher than the oxygen content on the surface side of the reflection reducing layer.

(Configuration 2)
The reflection reduction layer is characterized in that at least one of a film thickness and an oxygen content is adjusted so that a bottom peak wavelength at which a film surface reflectance is minimum falls within a wavelength range of 350 nm to 550 nm. The photomask blank according to Configuration 1.

(Configuration 3)
The reflection reducing layer is characterized in that at least one of a film thickness and an oxygen content is adjusted so that a bottom peak wavelength at which the film surface reflectance is minimum falls within a wavelength range of 365 nm to 550 nm. The photomask blank according to Configuration 1.

(Configuration 4)
The reflection reduction layer includes a high chromium oxide layer containing oxygen in an amount of 35 atomic percent to less than 65 atomic percent and a low chromium oxide layer containing oxygen in an amount of 10 atomic percent to 50 atomic percent from the light shielding layer side. 4. The photomask blank according to any one of configurations 1 to 3, wherein the photomask blank is a structure.

(Configuration 5)
5. The photomask blank according to any one of Structures 1 to 4, wherein the reflection reducing layer is made of a chromium oxynitride material further containing nitrogen.

(Configuration 6)
6. The photomask blank according to Configuration 5, wherein the reflection reducing layer contains 2 atom% or more and 30 atom% or less of nitrogen.

(Configuration 7)
7. The photomask blank according to claim 1, wherein the light shielding layer has a chromium nitride layer containing more nitrogen on the transparent substrate side than on the reflection reducing layer side. .

(Configuration 8)
The photomask blank according to any one of Structures 1 to 7, wherein each element contained in the light shielding layer and the reflection reducing layer has a composition gradient continuously.

(Configuration 9)
The photomask according to any one of Structures 1 to 8, further comprising a functional film that adjusts at least one of a transmittance of exposure light and a phase shift amount between the transparent substrate and the light shielding layer. blank.

(Configuration 10)
The photomask blank according to any one of configurations 1 to 9, wherein the photomask blank is an original plate of a photomask for manufacturing a display device.

(Configuration 11)
Using the photomask blank according to any one of configurations 1 to 10, and forming a resist film on the photomask blank;
Drawing a desired pattern with light;
Performing a development to form a resist pattern on the photomask blank; and
Patterning the light shielding layer and the reflection reducing layer by etching;
A photomask manufacturing method comprising manufacturing a photomask.

(Configuration 12)
A photomask manufactured by the method for manufacturing a photomask described in Structure 11 is placed on a mask stage of an exposure apparatus, and a transfer pattern formed on the photomask is exposed and transferred to a resist formed on a display apparatus substrate. A manufacturing method of a display device, characterized by comprising an exposure step to perform.

  The photomask blank of the present invention is a photomask blank in which a light shielding layer and a reflection reducing layer are laminated on a transparent substrate, the light shielding layer is a chromium-based material containing chromium, and the reflection reducing layer is a light shielding layer. It is a chromium oxide material containing less oxygen than oxygen and containing oxygen, and is a multi-layered laminated film. The oxygen content on the light-shielding layer side of the antireflection layer made of this laminated film is reduced in reflection. It is a photomask blank having an oxygen content higher than the layer surface side. With this structure, the mask pattern light-shielding film having a high cleaning resistance with little change in reflectance with respect to chemical liquids used in chemical cleaning, particularly ozone cleaning liquid, and comprising a reflection reducing layer and a light-shielding layer. A photomask blank with few defects can be provided. In addition, by manufacturing a photomask using the photomask blank, it is possible to provide a photomask with high mask pattern dimensional accuracy and low defects. Further, by manufacturing a display device using the photomask, a high-definition display device can be manufactured with a high yield.

It is a principal part cross-section block diagram which shows schematic structure of the photomask blank by Embodiment 1 of this invention. It is a schematic diagram which shows schematic structure of the in-line type | mold sputtering apparatus which can be used for film-forming of the photomask blank which concerns on this invention. It is principal part sectional drawing which shows the photomask manufacturing process by Embodiment 2 of this invention. FIG. 6 is a characteristic diagram showing an element distribution of a photomask blank film in Example 1. It is a characteristic view which shows the spectral characteristic of the reflectance of the photomask blank in Example 1. FIG. It is a characteristic view which shows the spectral characteristic of the reflectance of the photomask blank in the comparative example 2.

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

Embodiment 1 FIG.
In Embodiment 1, a photomask blank for manufacturing a display device and a manufacturing method thereof will be described.

  FIG. 1 is a schematic cross-sectional view showing a film configuration of a photomask blank 100 for manufacturing a display device. The photomask blank 100 is roughly composed of a substrate 1 that is transparent to exposure light and a light shielding film 5 for forming a mask pattern. The light shielding film 5 includes a light shielding layer 2 formed on the substrate side and a reflection reducing layer 3 formed thereon.

The light shielding layer 2 has a function of absorbing exposure light and shielding it, and has a laminated structure including a lower light shielding layer 21 formed on the substrate 1 side and an upper light shielding layer 22 formed thereon. The lower light shielding layer 21 and the upper light shielding layer 22 are made of a material containing chromium (Cr), and the lower light shielding layer 21 contains more nitrogen (N) than the upper light shielding layer 22. For example, the material of the lower light shielding layer 21 is CrN, and the material of the upper light shielding layer 22 is CrC. As a result, a difference occurs in the etching rate when the light-shielding layer 2 is wet-etched, so that the chrome residue is prevented and the cross-sectional shape after the etching is also good near vertical. Further, the adhesion of the light shielding layer 2 to the substrate 1 is improved, and the film peeling defect can be prevented. Here, it is preferable to add carbon to chromium because the wet etching rate with respect to the chromium etching solution can be easily controlled. In order to improve the wet etching controllability by slowing the wet etching rate of chromium by adding carbon or the like, the fluctuation of the additive to chromium ratio is 5 atomic% or less, preferably 3 atomic% or less. Is preferred.
In FIG. 1, the lower light-shielding layer 21 and the upper light-shielding layer 22 are depicted as being separated into two films, but they may be continuously changed layers or may be separated into two films. . Furthermore, a laminated film having three or more layers may be used. What is important is that the light shielding layer 2 is a laminated film, and the nitrogen content on the substrate 1 side (lower surface side) of the laminated film is larger than the nitrogen content on the reflection reduction layer 3 side (upper surface side). .
In addition, the light shielding layer 2 may be configured by only the upper light shielding layer 22 without providing the lower light shielding layer 21 as necessary.

  The reflection reduction layer 3 has a function of preventing the reflection of the mask pattern drawing light, and includes a first reflection reduction layer 31 on the upper light shielding layer 22 side and a second reflection reduction layer 32 formed thereon. It has a structure. The reflection reducing layer 3 also has an antireflection function for exposure light when manufacturing a display device. The reflection reducing layer 3 is made of a material containing at least chromium and oxygen (O), but the chromium content is less than the chromium content of the light shielding layer 2. This is because when the chromium content of the reflection reducing layer 3 is larger than the chromium content of the light shielding layer 2, the reflectance with respect to the mask pattern drawing light and the exposure light becomes high. Further, the oxygen content of the first reflection reduction layer 31 on the light shielding layer 2 side is equal to or higher than the oxygen content of the second reflection reduction layer 32 on the surface side. This is because it is easy to adjust the wavelength range where the minimum reflectance is obtained due to the relationship between the refractive index and the extinction coefficient, and the reflection reduction layer 3 becomes a dense film to suppress the occurrence of film defects. This is because the cleaning resistance against the ozone cleaning liquid is improved. In FIG. 1, the first reflection reduction layer 31 and the second reflection reduction layer 32 are depicted as being separated into two films. However, the layers may be changed continuously, and the two films may be separated. It does not matter if they are separated. Furthermore, a laminated film having three or more layers may be used. What is important is that the reflection reducing layer 3 is a laminated film, and the oxygen content on the light shielding layer 2 side (lower surface side) of the laminated film is not less than the oxygen content on the surface side (upper surface side). .

In the reflection reduction layer 3, the film thickness of the reflection reduction layer 3, that is, the film thickness of the first reflection reduction layer 31 and the first thickness are set so that the minimum reflectance of the light shielding film 5 falls within the wavelength range of 350 nm to 550 nm. At least one of the film thickness of the two reflection reducing layers 32 and the oxygen content of these layers is adjusted.
As another aspect, in the reflection reduction layer 3, the film thickness of the reflection reduction layer 3, that is, the first reflection is set so that the minimum value of the reflectance of the light shielding film 5 falls within the wavelength range of 365 nm to 550 nm. At least one of the thickness of the reduction layer 31 and the thickness of the second reflection reduction layer 32 or the oxygen content of these layers is adjusted.
The film thickness can be adjusted by the film formation time, and the oxygen content can be adjusted by the flow rate of the gas containing oxygen to be supplied. As a result, the mask pattern can be drawn at the minimum reflectance with respect to the laser beam used for mask pattern drawing, and the mask pattern drawing accuracy is improved. That is, it is possible to reduce CD (Critical Dimension) variation in the mask pattern to be formed. Further, when the reflectance of the film surface is in the vicinity of the minimum value, there is little change in the reflectance when the photomask blank is cleaned with ozone, and it is possible to reduce the CD variation of the mask pattern formed from this viewpoint. . For mask pattern drawing, a light source such as a laser having a wavelength of 355 nm, 365 nm, 405 nm, 413 nm, 436 nm, 442 nm, or a wavelength in the range of 350 nm to 500 nm or a laser having a wavelength of 365 nm to 500 nm is often used. It is also effective to keep the minimum value of the reflectance within the wavelength range of 350 nm to 500 nm or within the wavelength range of 365 nm to 500 nm.

  As a result of detailed examination, the oxygen content of the first reflection reduction layer 31 is 35 atomic% or more and 65 atomic% or less, and the oxygen content of the second reflection reduction layer 32 is 10 atomic% or more and 50 atomic% or less. Thus, it was found that there is a particular effect on the ease of adjustment of the wavelength region where the minimum reflectance is obtained, suppression of film defects, and resistance to ozone cleaning. On the other hand, when the oxygen content is outside the above range, the ease of adjustment of the wavelength region that provides the minimum reflectance is impaired, and the reflectance also increases.

Further, it is preferable that the reflection reducing layer 3 is a chromium oxynitride material further containing nitrogen, because the minimum value of the reflectance can be reduced due to the optical constant consisting of the refractive index and the extinction coefficient. The nitrogen content is desirably 2 atomic% or more and 30 atomic% or less.
Further, the reflection reducing layer 3 is preferably a chromium oxynitride carbide material further containing carbon, because the cleaning resistance and stability over time are improved, and the controllability of wet etching when forming a mask pattern is increased. The carbon content is preferably from 0.5 atomic% to 3.0 atomic%.

  In addition, if each element contained in the light shielding layer 2 and the reflection reducing layer 3 has a composition distribution (composition gradient) continuously in the film thickness direction, the cross section of the light shielding film pattern after the wet etching becomes smooth. Preferably, the CD accuracy is also improved.

  The light shielding film 5 for forming a mask pattern may be a light shielding film for a binary mask, or may be a phase shift mask (for example, a halftone phase shift mask) or a Levenson type phase shift mask (Levenson). The light shielding film 5 may be a phase shift film for a mask (Alternating Phase Shift Mask)) or a light shielding film 5 formed on or below a transmittance control film of a multi-level gradation mask.

Among the phase shift masks, in the case of a half-tone type phase shift mask or a multi-tone mask in which a transmittance control film pattern is formed between a transparent substrate and a light shielding film pattern, the phase shift film serving as the mask pattern and the transmission In order for the rate control film to perform transmittance control and / or phase control of transmitted light, a functional film that adjusts at least one of transmittance and phase is provided between the substrate 1 and the lower light shielding layer 21. As this functional film, at least one of metal, oxygen, nitrogen, carbon, or fluorine is added to silicon (Si) that is a material having etching selectivity with respect to a chromium material that is a material constituting the light shielding layer. The included material is suitable. For example, metal silicide such as MoSi, metal silicide oxide, metal silicide nitride, metal silicide oxynitride, metal silicide oxynitride, metal silicide oxycarbide, metal silicide oxynitride, SiO, SiO ₂ and SiON are suitable. SiO and SiO ₂ are composed of the same element as that when the substrate 1 is made of synthetic quartz. However, the etching rate differs from the etching rate of the substrate due to a difference in bonding state between atoms and the like. The distance (etching depth) can be controlled with high accuracy. Note that this functional film may be a laminated film composed of the above-described films cited as the functional film.
The functional film is processed using the light shielding film pattern 5a containing chromium as an etching mask. For this reason, a wet etching solution is used for processing the functional film so that the functional film has a higher etching rate than the light shielding film 5 composed of the light shielding layer 2 and the reflection reducing layer 3. This type of wet etching solution is selected from, for example, at least one fluoride compound selected from hydrofluoric acid, hydrosilicofluoric acid, and ammonium hydrogen fluoride, and hydrogen peroxide, nitric acid, and sulfuric acid. And a solution containing at least one oxidizing agent or water. Specifically, an etching solution in which a mixed solution of ammonium hydrogen fluoride and hydrogen peroxide is diluted with pure water, an etching solution in which ammonium fluoride is mixed in a hydrofluoric acid aqueous solution, and the like can be given.
Hereinafter, the manufacturing process of the photomask blank will be described in detail.

1. Preparation Step First, the substrate 1 is prepared.
The material of the substrate 1 is not particularly limited as long as the material has translucency with respect to the exposure light to be used and has a rigidity. Examples thereof include synthetic quartz glass, soda lime glass, and alkali-free glass. In addition, polishing including a rough polishing process, a precision polishing process, a local processing process, and a touch polishing process is appropriately performed as necessary so as to obtain a flat and smooth main surface. Thereafter, cleaning is performed to remove foreign matters and contamination on the surface of the substrate 1. As the cleaning, for example, sulfuric acid, sulfuric acid / hydrogen peroxide (SPM), ammonia, ammonia hydrogen peroxide (APM), OH radical cleaning water, ozone water or the like can be used.

2. Next, a light shielding film 5 for forming a mask pattern made of a chromium-based material is formed on the main surface of the substrate 1 by a sputtering method. The light shielding film 5 is composed of a laminated film having the light shielding layer 2 and the reflection reducing layer 3, and each layer of the light shielding layer 2 and the reflection reducing layer 3 is also a laminated film. There is no particular limitation on the number of laminated layers, but here, the light shielding layer 2 is two layers and the reflection reducing layer 3 is also two layers, the lower light shielding layer 21, the upper light shielding layer 22, the first reflection reducing layer 31, The formation process in the case where the second reflection reducing layer 32 is composed of a total of four layers will be described in detail.

First, the film forming apparatus will be described.
FIG. 2 is a schematic view showing an example of a sputtering apparatus used for forming the light shielding layer 2 and the reflection reducing layer 3.
The sputtering apparatus 300 shown in FIG. 2 is an inline type, and includes a carry-in chamber LL, a first sputtering chamber SP1, a first buffer chamber BU1, a second sputtering chamber SP2, a second buffer chamber BU2, a third sputtering chamber SP3, and a third buffer. It consists of nine chambers, chamber BU3, fourth sputter chamber SP4, and carry-out chamber UL. These nine chambers are arranged sequentially in sequence.

  The sample 301 on which the substrate 1 is mounted on the tray has a predetermined movement speed (conveyance speed) and a loading chamber LL, a first sputtering chamber SP1, a first buffer chamber BU1, a second sputtering chamber SP2, 2 The buffer chamber BU2, the third sputter chamber SP3, the third buffer chamber BU3, the fourth sputter chamber SP4, and the carry-out chamber UL can be transferred in this order.

  The carry-in chamber LL and the first sputter chamber SP1, and the fourth sputter chamber SP4 and the carry-out chamber UL are partitioned by shutters 311 and 312, respectively. The carry-in chamber LL, the sputter chambers SP1 to SP4, the buffer chambers BU1 to BU3, and the carry-out chamber UL are connected to an exhaust device (not shown) that exhausts air. Furthermore, sputter targets 331 to 334 and gas inlets 321 to 324 are arranged in the sputter chambers SP1 to SP4.

  Next, a process of forming the lower light shielding layer 21, the upper light shielding layer 22, the first reflection reduction layer 31, and the second reflection reduction layer 32 using the inline-type sputtering apparatus 300 will be described.

First, the sample 301 on which the substrate 1 is mounted on a tray (not shown) is loaded into the loading chamber LL.
After the inside of the sputtering apparatus 300 is set to a predetermined degree of vacuum, a film forming gas necessary for forming the lower light shielding layer 21 is introduced from the first gas introduction port 321 at a predetermined flow rate, and a predetermined sputtering is performed. Power is applied and the sample 301 is passed over the first sputter target 331 at a predetermined speed S1. As the first sputter target, chromium or a target mainly containing chromium is used. As a target mainly containing chromium, there is chromium nitride or the like. However, since reactive sputtering with a supply gas is easier to control the inclination of the composition distribution as desired, chromium was used as the target here. The gas supplied from the first gas inlet 321 is a gas containing at least nitrogen (N) to form a CrN layer as the lower light shielding layer 21, and an inert gas such as argon (Ar) gas is used as necessary. Add. In addition to argon gas, inert gas includes helium (He) gas, neon (Ne) gas, krypton (Kr) gas, xenon (Xe) gas, etc. One or more of these are necessary. Is selected accordingly. The composition distribution in the film thickness direction can be controlled by the arrangement of gas inlets, the gas supply method, and the like.
By the above process, when the sample 301 passes near the first sputter target 331 of the first sputter chamber SP1, the main surface of the substrate 1 is made of a chromium-based material having a predetermined thickness by reactive sputtering. A lower light shielding layer 21 (CrN layer) is formed.

Thereafter, the sample 301 passes through the first buffer chamber BU1 and moves to the second sputtering chamber SP2. A predetermined flow rate of a deposition gas necessary for forming the upper light shielding layer 22 is introduced from the second gas inlet 322, and a predetermined sputtering power is applied. In this state, the sample 301 is deposited at a predetermined speed S2 while passing over the second sputter target 332. A chrome target is used as the second sputter target. In addition, a target containing an appropriate additive for chromium can also be used. The gas supplied from the second gas introduction port 322 is a gas containing at least carbon (C) to form a CrC layer as the upper light shielding layer 22, and an inert gas such as argon (Ar) gas is used as necessary. Add. In addition to argon gas, inert gas includes helium (He) gas, neon (Ne) gas, krypton (Kr) gas, xenon (Xe) gas, etc. One or more of these are necessary. Is selected accordingly. Examples of the gas containing carbon include methane (CH ₄ ) gas, carbon dioxide (CO ₂ ) gas, and carbon monoxide (CO) gas. The composition distribution in the film thickness direction can be controlled by the arrangement of gas inlets, the gas supply method, and the like.
Through the above steps, when the sample 301 passes near the second sputter target 332 of the second sputter chamber SP2, the main surface of the sample 301 is made of a chromium-based material having a predetermined thickness by reactive sputtering. An upper light shielding layer 22 (CrC layer) is formed.

Thereafter, the sample 301 passes through the second buffer chamber BU2 and moves to the third sputtering chamber SP3. A predetermined flow rate of a deposition gas necessary for forming the first reflection reducing layer 31 is introduced from the third gas introduction port 323, and a predetermined sputtering power is applied. In this state, the sample 301 is deposited at a predetermined speed S3 while passing over the third sputter target 333. A chrome target is used as the third sputter target. In addition, a target containing an appropriate additive for chromium can also be used. The gas supplied from the third gas inlet 323 is a gas containing at least carbon (C), oxygen (O), and nitrogen (N) in order to form a CrCON layer as the first reflection reducing layer 31. In response, an inert gas such as argon (Ar) gas is added. In addition to argon gas, inert gas includes helium (He) gas, neon (Ne) gas, krypton (Kr) gas, xenon (Xe) gas, etc. One or more of these are necessary. Is selected accordingly. Examples of the gas containing carbon include methane (CH ₄ ) gas, carbon dioxide (CO ₂ ) gas, and carbon monoxide (CO) gas. Examples of the gas containing nitrogen include nitrogen (N ₂ ) gas, nitrogen dioxide (NO ₂ ) gas, and nitrogen monoxide (NO) gas. Examples of the gas containing oxygen include, for example, oxygen (O ₂ ) gas, carbon dioxide (CO ₂ ) gas that is the oxygen component-containing gas, carbon monoxide (CO) gas, nitrogen dioxide (NO ₂ ) gas, And nitric oxide (NO) gas. The composition distribution in the film thickness direction can be controlled by the arrangement of gas inlets, the gas supply method, and the like. Here, if the film is formed under a condition where the flow rate of oxygen is reduced and the sputtering power is low, a dense film is formed and film defects are less likely to occur.
The sputtering power condition for making the first reflection reducing layer 31 a dense film and making film defects less likely to occur is preferably 3.0 kW or less. Considering the reduction of film defects and productivity, the sputtering power is preferably 1.0 kW or more and 3.0 kW or less, more preferably 1.0 kW or more and 2.5 kW or less.
Through the above steps, when the sample 301 passes near the third sputter target 333 in the third sputter chamber SP3, the main surface of the sample 301 is made of a chromium-based material having a predetermined thickness by reactive sputtering. The first reflection reduction layer 31 (CrCON layer) is formed.

Thereafter, the sample 301 passes through the third buffer chamber BU3 and moves to the fourth sputtering chamber SP4. A predetermined flow rate of a deposition gas necessary for forming the second reflection reducing layer 32 is introduced from the fourth gas introduction port 324, and a predetermined sputtering power is applied. In this state, the sample 301 is deposited at a predetermined speed S4 while passing over the fourth sputter target 334. As the fourth sputter target, a chromium target is used. In addition, a target containing an appropriate additive for chromium can also be used. The gas supplied from the fourth gas inlet 324 is a gas containing at least carbon (C), oxygen (O), and nitrogen (N) in order to form a CrCON layer as the second reflection reducing layer 32. In response, an inert gas such as argon (Ar) gas is added. In addition to argon gas, inert gas includes helium (He) gas, neon (Ne) gas, krypton (Kr) gas, xenon (Xe) gas, etc. One or more of these are necessary. Is selected accordingly. Examples of the gas containing carbon include methane (CH ₄ ) gas, carbon dioxide (CO ₂ ) gas, and carbon monoxide (CO) gas. Examples of the gas containing nitrogen include nitrogen (N ₂ ) gas, nitrogen dioxide (NO ₂ ) gas, and nitrogen monoxide (NO) gas. Examples of the gas containing oxygen include, for example, oxygen (O ₂ ) gas, carbon dioxide (CO ₂ ) gas that is the oxygen component-containing gas, carbon monoxide (CO) gas, nitrogen dioxide (NO ₂ ) gas, And nitric oxide (NO) gas. The composition distribution in the film thickness direction can be controlled by the arrangement of gas inlets, the gas supply method, and the like. Here, if the film is formed under a condition where the flow rate of oxygen is reduced and the sputtering power is low, a dense film is formed and film defects are less likely to occur.
The sputtering power condition for making the second reflection reducing layer 32 a dense film and making film defects less likely to occur is preferably 3.0 kW or less. Considering the reduction of film defects and productivity, the sputtering power is preferably 1.0 kW or more and 3.0 kW or less, more preferably 1.0 kW or more and 2.5 kW or less.
Through the above steps, when the sample 301 passes through the vicinity of the fourth sputter target 334 of the fourth sputter chamber SP4, the main surface of the sample 301 is made of a chromium-based material having a predetermined thickness by reactive sputtering. A second reflection reduction layer 32 (CrCON layer) is formed.

Thereafter, the sample 301 moves to the carry-out chamber UL, and after that, the shutter 312 is closed and evacuated, then opened to the atmosphere and the sample 301 is taken out of the sputtering apparatus 300.
The extracted sample 301 is appropriately subjected to defect inspection and cleaning as necessary, and the photomask blank 100 is manufactured.
The photomask blank 100 manufactured in the first embodiment has a low reflectance with respect to the mask pattern drawing light and a high resistance to ozone cleaning that is cleaning before resist coating, so that it is uniform within the photomask blank surface even after ozone cleaning. The reflectivity is In addition, there is a feature that there are few film defects in the light shielding film 5 for the mask pattern.

Embodiment 2. FIG.
In Embodiment 2, a method for manufacturing a photomask for manufacturing a display device will be described with reference to FIG.
First, before applying and forming a resist on the prepared photomask blank 100, pre-resist application cleaning (chemical cleaning) with a chemical solution such as the above-described cleaning solution containing sulfuric acid or ozone cleaning solution is performed. In particular, as cleaning before resist coating, ozone cleaning may be performed using an ozone cleaning liquid. This ozone cleaning is a position of pre-resist cleaning performed after the cleaning, thereby removing foreign matters and contamination on the resist-coated surface and contributing to improving the adhesion between the resist and the photomask blank surface. This improvement in adhesion has an effect of preventing the resist pattern from peeling off and preventing the etching shape deterioration of the mask pattern light-shielding film 5. That is, by improving the adhesion, when the mask pattern light-shielding film 5 is wet-etched, the wet etching solution is prevented from entering the interface between the resist film 4 and the photomask blank (reflection reduction layer 3). Deterioration of the etching shape of the light shielding film 5 can be prevented. Hereinafter, ozone cleaning will be described as the pre-resist cleaning, but the cleaning apparatus and cleaning method can be replaced with chemical cleaning using a chemical solution such as a cleaning solution containing sulfuric acid.

  Typical ozone cleaning is spin cleaning using ozone water, but bath cleaning may be performed in which the photomask blank 100 is placed in a bath of ozone cleaning liquid (ozone water) for cleaning. Spin cleaning is suitable for single-wafer processing, consumes less cleaning liquid, and has a relatively compact cleaning device, and bath cleaning has a feature that a plurality of photomask blanks 100 can be cleaned simultaneously. Photomask blanks for manufacturing large display devices are also large in size. For photomask blanks for manufacturing large display devices, cleaning of single wafer processing is required because of the consumption of cleaning liquid and the compactness of the cleaning device. The method, particularly the spin cleaning method, is preferably used.

  In the ozone cleaning by the spin cleaning method, first, an ozone cleaning liquid is dropped near the rotation center of the photomask blank 100 rotated at a low speed, and the second reflection reduction layer 32 of the photomask blank 100 is spread by spreading by rotation. Apply ozone cleaning solution to the entire surface. After that, the photomask blank 100 is rotated at a low speed while supplying the ozone cleaning liquid until the cleaning end time, and cleaning is continued. After the cleaning time ends, pure water is supplied to replace the ozone cleaning liquid with pure water, and finally spin drying. I do. It is also possible to use paddle type ozone cleaning that stops the dropping of the ozone cleaning liquid and the rotation of the photomask blank after the ozone cleaning liquid is deposited on the entire surface of the second reflection reducing layer 32 of the photomask blank 100. The flowing liquid type spin cleaning method that continues to flow the cleaning liquid while rotating at low speed is characterized by the fact that the ozone concentration does not change easily and has a mechanical cleaning effect by the flowing liquid. The paddle type cleaning method consumes the ozone cleaning liquid. There are few features. The spin cleaning method has the above-described characteristics. However, since the ozone cleaning liquid is first dropped on the rotation center of the photomask blank 100, a concentric cleaning impact (cleaning damage) centered on the rotation center is received. Cheap. Therefore, the cleaning damage difference tends to occur concentrically. Photomask blanks for manufacturing display devices, for example, those with large photomask blank dimensions such as 1220 mm × 1400 mm are often used, and this concentric cleaning damage difference (damage in-plane distribution difference) tends to increase. There is. For this reason, it is necessary to improve the ozone cleaning resistance particularly for a photomask blank for manufacturing a display device. In addition, if ozone cleaning liquid is dropped after performing pre-processing for supplying pure water to the surface of the photomask blank 100 in advance to wet the surface, first damage to the photomask blank surface material due to the ozone cleaning droplet (first) Impact) is reduced.

Subsequent to the resist pre-cleaning by ozone cleaning, a resist pattern forming process for forming a resist pattern 4a on the second reflection reducing layer 32 of the photomask blank 100 is performed.
Specifically, in this resist pattern forming step, first, a resist film 4 is formed on the second reflection reducing layer 32 that is the outermost surface layer of the photomask blank 100 (FIG. 3B). Thereafter, a desired pattern such as a circuit or a pixel pattern is drawn on the resist film 4 using light. As the drawing light, light having a wavelength of 355 nm, 365 nm, 405 nm, 413 nm, 436 nm, and 442 nm, particularly laser light is often used. Thereafter, the resist film 4 is developed with a predetermined developer to form a resist pattern 4a (FIG. 3C).

  Next, the light shielding film 5 for mask pattern is wet-etched using the resist pattern 4a as a mask to form the light shielding film pattern 5a (FIG. 3D). The mask pattern light-shielding film 5 includes a lower light-shielding layer 21, an upper light-shielding layer 22, a first reflection reduction layer 31, and a second reflection reduction layer 32. In order to reduce the number of processes, wet etching is performed collectively. It is desirable. The reduction in the number of processes not only improves the throughput and simplifies the etching apparatus, but also generally works to improve the defect quality. The photomask blank 100 manufactured in the first embodiment is made of a material in which all the layers constituting the light shielding film 5 for the mask pattern from the lower light shielding layer 21 to the second reflection reducing layer 32 contain chromium. In addition, since the composition of the constituent material is adjusted so that the etching rate is increased with respect to the chromium etching solution in the film thickness direction from the surface side to the substrate 1 side, The cross section is vertical, the bottom of the pattern is less likely to skirt, and chrome etching residues are less likely to occur. Specific examples of the chromium etching solution used here include an etching solution containing ceric ammonium nitrate and perchloric acid, and an alkaline solution containing no cerium.

  Thereafter, the resist pattern 4a is removed by a resist stripping solution, ashing or the like, and cleaning is performed. As the cleaning liquid, for example, sulfuric acid, sulfuric acid / hydrogen peroxide (SPM), ammonia, ammonia hydrogen peroxide (APM), OH radical cleaning water, ozone water, or the like can be used. Thereafter, a mask pattern defect inspection, defect correction, and the like are appropriately performed as necessary. In this way, the photomask 200 having the light shielding film pattern 5a composed of the lower light shielding layer pattern 21a, the upper light shielding layer pattern 22a, the first reflection reduction layer pattern 31a, and the second reflection reduction layer pattern 32a on the substrate 1. Manufacturing.

  In the manufacturing method of the photomask 200, the resist film 4 is directly formed on the second reflection reducing layer 32. However, an etching mask can be used. In this case, an etching mask is formed on the second reflection reducing layer 32, and the resist film 4 is formed thereon. After the resist pattern 4a is formed by the above-described method, the etching mask is once processed by wet etching, and the lower light-shielding layer 21, the upper light-shielding layer 22, and the first reflection reducing layer are processed using the processed etching mask as a mask. The light shielding film 5 composed of 31 and the second reflection reduction layer 32 is wet-etched. Thereafter, the processed etching mask is removed. The resist pattern 4a may be removed immediately after the etching mask is processed, or may be removed after wet etching of the light shielding film 5. When the etching mask is a material that has high wet etching resistance and has high adhesion to chromium oxide to prevent infiltration of the wet etching solution, this method allows light shielding with a vertical cross-sectional shape including the upper surface portion. The film pattern 5a can be obtained. Examples of the material for the etching mask include materials containing at least one of metal, oxygen, nitrogen, and carbon in silicon, such as MoSi, SiO, SiON, and SiC.

  When the photomask blank is the above-described phase shift mask blank or multi-tone mask blank, the phase of the exposure light described in the first embodiment formed between the substrate 1 and the lower light shielding layer 21 and The functional film for controlling the transmittance is etched after the light shielding film pattern 5a is formed by the above-described method. Further, when fine adjustment of the phase is necessary, the substrate 1 is etched to a desired depth using a dilute hydrofluoric acid aqueous solution or an etching solution in which a buffer solution such as ammonium fluoride is mixed in the hydrofluoric acid aqueous solution. Thereafter, the resist pattern 4a is removed to manufacture a phase shift mask.

  The photomask 200 manufactured in the second embodiment has high resistance to ozone cleaning that is cleaning before resist application. For this reason, there is little change of the reflectance with respect to the mask pattern drawing light, and the reflectance with respect to this light is uniform within the photomask blank surface. As a result, the CD variation of the formed mask pattern is small. In addition, the cross-sectional shape of the mask pattern bulk portion is also close to the vertical, and the bottom portion is less skirted. In addition, the light-shielding film 5 for the mask pattern has few film defects and few defects generated in the mask manufacturing process.

Embodiment 3 FIG.
In Embodiment 3, a method for manufacturing a display device will be described.

In the method for manufacturing a display device according to the third embodiment, first, a photomask for manufacturing a display device described in the second embodiment is manufactured for a substrate with a resist film in which a resist film is formed on the substrate of the display device. The photomask 200 obtained by the method is placed on the mask stage of the exposure apparatus so as to face the resist film formed on the substrate via the projection optical system of the exposure apparatus.
Next, a resist exposure process is performed in which the photomask 200 is irradiated with exposure light to expose the resist film.

  The exposure light is, for example, light having a wavelength range of 365 nm or more and 550 nm or less, and specifically, light having a single wavelength such as i-line having a wavelength of 365 nm, h-line having a wavelength of 405 nm, and g-line having a wavelength of 436 nm, or these. Including complex light is often used.

  According to the manufacturing method of the display device of the third embodiment, the display device is manufactured using the photomask obtained by the manufacturing method of the photomask for manufacturing the display device described in the second embodiment. For this reason, a fine pattern can be formed with high accuracy and low defects. In addition to this lithography process (exposure and development process), various processes such as etching of the film to be processed, formation of the insulating film and conductive film, introduction of dopants, and annealing have resulted in the formation of the desired electronic circuit. A fine display device can be manufactured with a high yield.

  Hereinafter, the present invention will be described in more detail with reference to the drawings for each embodiment. In addition, the same code | symbol is used about the same component in each Example, and description is simplified or abbreviate | omitted.

  FIG. 3 is a schematic cross-sectional view of an essential part showing a process of manufacturing a photomask for manufacturing a display device from a photomask blank 100 for manufacturing a display device, which is used in the description of the second embodiment.

  As shown in FIG. 3A, the photomask blank 100 of Example 1 includes a substrate 1, a light shielding layer 2 having a function of shielding exposure light mainly used for manufacturing a display device, and reflection of mask pattern drawing light. The light-shielding film 5 for mask pattern is formed by combining the light-shielding layer 2 and the reflection-reducing layer 3 together. The light shielding layer 2 includes a two-layer film in which CrN is a lower light shielding layer 21 and CrC is an upper light shielding layer 22, and the reflection reduction layer 3 is a first CrCON layer 31 (first reflection reduction layer having a high oxygen content). ) And a second layer film composed of a second CrCON layer 32 (second reflection reduction layer) made of a material having a lower oxygen content or equivalent to the material of the first CrCON layer 31. First, the manufacturing method of the photomask blank 100 and details of the film configuration will be described.

((Photomask blank, its manufacture and characteristic evaluation))
(((substrate)))
An 8092 size (about 800 mm × 920 mm) synthetic quartz glass substrate in which both surfaces of the first main surface and the second main surface were polished was prepared as a substrate 1. Here, the film thickness is 10 mm, but it may be 8 mm. Polishing including a rough polishing process, a precision polishing process, a local processing process, and a touch polishing process was appropriately performed so as to obtain a flat and smooth main surface.

(((Shading film)))
On the substrate 1, a large in-line type sputtering apparatus is used, and the light shielding layer 2 composed of two layers having CrN as the lower light shielding layer 21 and CrC as the upper light shielding layer 22, and the first CrCON layer 31 having a high oxygen content. And forming a light shielding film 5 for a mask pattern composed of the reflection reducing layer 3 made of the second CrCON layer 32 made of a material having a lower oxygen content than the material of the first CrCON layer 31. It was.

Next, a method for forming these films will be described.
First, the sample 301 mounted on the tray (not shown) with the main surface (surface on which the light shielding film is formed) of the substrate 1 facing downward is carried into the carry-in chamber LL of the inline-type sputtering apparatus 300 shown in FIG. did. Here, sputter targets 331, 332, 333, and 334 made of chromium (Cr) are disposed in the first sputter chamber SP1, the second sputter chamber SP2, the third sputter chamber SP3, and the fourth sputter chamber SP4, respectively. ing.

Next, the shutter 311 is opened, the sample 301 made of the substrate 1 is moved from the carry-in chamber LL to the first sputter chamber SP1, and the first gas introduction port arranged near the first sputter target 331 in the first sputter chamber SP1. Reactive sputtering was performed by introducing a mixed gas of argon (Ar) gas and nitrogen (N 2) gas from 321 and applying a sputtering power of 1.5 kW to the first sputtering target 331. The gas flow rates are 65 sccm for Ar and 15 sccm for N ₂ . At this time, the sample 301 was moved in the first sputter chamber SP1 at a speed of 400 mm / min. By this step, a CrN film as the lower light shielding layer 21 was formed to a thickness of 15 nm on the main surface of the substrate 1.

Next, a mixed gas in which 4.9% methane (CH ₄ ) is mixed with argon (Ar) gas is introduced from the second gas introduction port 322 arranged near the second sputtering target 332 of the second sputtering chamber SP2. Then, a sputtering power of 8.5 kW was applied to the second sputtering target 332. The sample 301 was moved from the first sputtering chamber SP1 through the first buffer chamber BU1 to the second sputtering chamber SP2, and reactive sputtering was performed in the second sputtering chamber SP2. Here, the flow rate of the gas is 31 sccm. At this time, the sample 301 was moved in the second sputter chamber SP2 at a speed of 400 mm / min. By this step, a CrC film having a film thickness of 60 nm as the upper light-shielding layer 22 was formed on CrN film having a film thickness of 15 nm as the lower light-shielding layer 21.

Next, a mixed gas in which 5.5% methane (CH ₄ ) is mixed with argon (Ar) gas from a third gas introduction port 323 disposed near the third sputter target 333 of the third sputter chamber SP3; Nitrogen (N ₂ ) gas and oxygen (O ₂ ) gas were introduced, and a sputtering power of 1.5 kW was applied to the third sputtering target 333. The sample 301 was moved from the second sputtering chamber SP2 through the second buffer chamber BU2 to the third sputtering chamber SP3, and reactive sputtering was performed in the third sputtering chamber SP3. The gas flow rate is 31 sccm for a mixed gas of argon and methane, 8 sccm for nitrogen gas, and 3 sccm for oxygen gas. At this time, the sample 301 was moved in the third sputter chamber SP3 at a speed of 400 mm / min. By this reactive ion sputtering step, a first CrCON (first reflection reduction layer 31) having a thickness of 10 nm was formed on CrC having a thickness of 60 nm, which is the upper light shielding layer 22.

Next, a mixed gas in which 5.5% methane (CH ₄ ) is mixed with argon (Ar) gas from a fourth gas introduction port 324 disposed near the fourth sputter target 334 of the fourth sputter chamber SP4; Nitrogen (N ₂ ) gas and oxygen (O ₂ ) gas were introduced, and a sputtering power of 1.95 kW was applied to the fourth sputtering target 334. The sample 301 was moved from the third sputtering chamber SP3 through the third buffer chamber BU3 to the fourth sputtering chamber SP4, and reactive sputtering was performed in the fourth sputtering chamber SP4. The gas flow rate is 31 sccm for a mixed gas of argon and methane, 8 sccm for nitrogen gas, and 3 sccm for oxygen gas. At this time, the sample 301 was moved in the fourth sputter chamber SP4 at a speed of 400 mm / min. By this reactive ion sputtering process, a second CrCON (second reflection reduction layer 32) having a thickness of 19 nm was formed on the first CrCON (first reflection reduction layer 31) having a thickness of 10 nm. .

After that, after moving the sample 301 from the fourth sputter chamber SP4 to the unloading chamber UL, the shutter 312 is closed, and after evacuating, the unloading chamber UL is returned to the atmospheric pressure state, and CrN, A sample 301 on which the light shielding film 5 made of CrC, first CrCON, and second CrCON was formed was taken out from the sputtering apparatus 300.
In this way, a photomask blank 100 was obtained in which the light shielding film 5 made of CrN, CrC, first CrCON, and second CrCON was formed on the synthetic quartz glass substrate.

The film formation conditions of each film (each layer) described above are described as a list as follows.
Sputtering 1: Ar = 65 sccm, N ₂ = 15 sccm, Power = 1.5 kW, sample moving speed = 400 mm / min
Sputtering 2: Ar / CH ₄ (4.9%) = 31 sccm, Power = 8.5 kW, sample moving speed = 400 mm / min
Sputtering 3: Ar / CH ₄ (5.5%) = 31 sccm, N ₂ = 8 sccm, O ₂ = 3 sccm, Power = 1.5 kW, sample moving speed = 400 mm / min
Sputtering 4: Ar / CH ₄ (5.5%) = 31 sccm, N ₂ = 8 sccm, O ₂ = 3 sccm, Power = 1.95 kW, sample moving speed = 400 mm / min
What is characteristic of this film formation condition is that, in comparison with Comparative Example 2 described later, in sputtering 3 and sputtering 4 which are film formation processes of the reflection reducing layer 3, the oxygen gas flow rate is small and the power Is low. This film forming condition is a basis for making the reflection reducing layer 3 a dense film with few defects.

About the obtained photomask blank, the composition analysis of the depth direction by X-ray photoelectron spectroscopy (XPS) was performed. The result is shown in FIG. Hereinafter, in the description of this figure, the depth from the surface is expressed by the sputter time (sputter etching time).
From the characteristics of this composition distribution, from the surface to a depth of about 8 min (this region will be referred to as a surface natural oxide layer) and from about 8 min to about 32 min (this region will be referred to as an A layer herein). From about 32 min to about 55 min (this region will be referred to herein as the B layer), from about 55 min to about 70 min (this region will be referred to as the transition layer), and from about 70 min to about 170 min. (This region will be referred to as C layer here) and from about 170 min to about 195 min (this region will be referred to as D layer here). The composition changes continuously between the layers. Here, the A layer is the second CrCON layer (second reflection reduction layer), the B layer is the first CrCON layer (first reflection reduction layer), the C layer is the CrC layer (upper layer of the light shielding layer), D The layer corresponds to a CrN layer (under the light shielding layer).

  The chromium (Cr) atomic ratio of the A layer and the B layer is about 55% or less, the C layer (CrC layer) is about 90%, and the D layer (CrN layer) is about 75% or more. small. That is, the chromium content of the first and second reflection reducing layers 3 is less than the chromium content of the light shielding layer 2. In addition, the oxygen ratio of the A layer which is the second reflection reduction layer 32 (reflection reduction layer on the surface layer side) is about 24% to 45%, and the first reflection reduction is about 45% to 50%. It is smaller than the oxygen ratio of the B layer which is the layer 31 (reflection reducing layer on the light shielding layer side). Focusing on nitrogen (N), the nitrogen atom ratio of the A layer which is the second reflection reduction layer 32 (reflection reduction layer on the surface layer side) is about 9% to 20%, and is about 2% to 9%. It is larger than the nitrogen ratio of the B layer which is the first reflection reduction layer 31 (reflection reduction layer on the light shielding layer side). Further, nitrogen atoms are detected from the A layer to the D layer, and the nitrogen content is increased to about 20% particularly in the D layer which is a CrN layer. When attention is paid to the light shielding layer 2, the nitrogen content of the D layer corresponding to the CrN layer (lower light shielding layer 21) is larger than the nitrogen content of the C layer corresponding to the CrC layer (upper light shielding layer 22). When attention is paid to the distribution of atomic ratios in the reflection reduction layer composed of the A layer and the B layer, the composition gradient of chromium, oxygen, and nitrogen continuously in each layer.

  In the photomask blank manufacturing method described above, the layers of the light shielding film 5 were continuously formed under reduced pressure and vacuum conditions without returning to the atmosphere in the middle. By continuously forming the film in a vacuum state in this manner, the variation in composition from the outermost surface of the light shielding film 5 (second reflection reduction layer 32 made of CrCON) to the substrate 1 can be reduced. it can.

(((Evaluation of reflectivity and ozone cleaning resistance)))
The photomask blank 100 was subjected to ozone cleaning, and test evaluation of ozone cleaning resistance was performed. For the purpose of accelerating the ozone cleaning resistance test, ozone cleaning solution is ozone water with an ozone concentration of 45 mg / L, and four levels of samples are prepared: untreated, treated for 30 minutes, treated for 60 minutes, and treated for 120 minutes. The spectral reflectance characteristics of each sample were evaluated. The result is shown in FIG. The spectral reflectance was measured with a spectrophotometer (SolidSpec-3700 manufactured by Shimadzu Corporation).

  As a result, the film surface reflectance of the mask pattern light-shielding film 5 before the ozone treatment (before the ozone treatment) is, for example, a laser used when manufacturing a photomask for a display device as shown in FIG. And 11% or less in a drawing wavelength band of 350 nm to 450 nm including a drawing wavelength (for example, 355 nm, 365 nm, 405 nm, 413 nm, 436 nm, 442 nm). Further, the wavelength at which the reflectance is minimum is 430 nm, and the reflectance at that time is 7.26%. The reflectance at a wavelength of 436 nm was 7.3%, which was almost the same as the minimum value. The reflectance at 413 nm, which is a drawing wavelength described later, was 7.49%. These reflectances are good values that are sufficiently low to perform mask pattern drawing with high accuracy, and exposure light of a display device mainly composed of an i-line having a wavelength of 365 nm, an h-line having a wavelength of 405 nm, and a g-line having a wavelength of 436 nm. It was a low reflectance that was sufficiently acceptable.

  When the film surface reflectivity of the light shielding film 5 for the mask pattern is high, when the pattern on the photomask is exposed and transferred to the resist formed on the substrate of the display device via the projection optical system, the display device The exposure light is reflected from the substrate, and the reflected light is re-reflected on the surface of the photomask, and is affected by reflection, irregular reflection, imaging, and the like in the projection optical system, thereby causing adverse effects on the transfer such as flare and ghost. Here, the flare is an exposure cover, which lowers the contrast of the transferred optical image, causing a decrease in resolution and a decrease in transfer dimensional accuracy. The film surface reflectance with respect to the exposure light of the light shielding film 5 for the mask pattern of Example 1 is a sufficiently low value that does not cause the problem of flare and ghost. Therefore, high-precision exposure to the substrate of the display device can be performed. did it.

Next, the influence of ozone cleaning on the film surface reflectance of the light shielding film 5 for the mask pattern will be described. As the ozone cleaning time is increased to 0 minutes, 30 minutes, 60 minutes, and 120 minutes, the wavelength that minimizes the reflectance of this film shifts to the short wavelength side, and the minimum reflectance slightly decreases. . The wavelengths that minimize the reflectance when the ozone cleaning time is 0 minutes, 30 minutes, 60 minutes, and 120 minutes are 430 nm, 412 nm, 381 nm, and 325 nm, respectively, and the minimum reflectance at that time is 7.26%. 6.8%, 6.4%, and 6.1%. Then, until the ozone treatment was performed for 60 minutes, the minimum value shifted to the short wavelength side while maintaining the spectral characteristic curve shape. The reflectance at a wavelength of 436 nm increases with the time of ozone treatment, but the change up to 60 minutes of ozone treatment is slight, and the value is sufficiently low at 8.7%, an increase of 1.4% compared to the untreated ozone treatment. Value. Further, the change in reflectance at the drawing wavelength of 413 nm was an even lower value of 7.08%, a decrease of 0.41%.
In addition, another photomask blank 100 was subjected to sulfuric acid cleaning, and a sulfuric acid cleaning resistance test evaluation was performed. As the sulfuric acid cleaning solution, sulfuric acid having a temperature of 100 ° C. and a sulfuric acid concentration of 98% was used, and untreated, treated for 5 minutes, treated for 10 minutes, and treated for 15 minutes, and then subjected to spectroscopy using the same spectrophotometer as described above. The reflectance characteristics were evaluated.
As a result, the reflectance at a wavelength of 436 nm decreased with the sulfuric acid washing time, but the change up to 15 minutes with sulfuric acid treatment was slight, and the value was about 0.7% lower than that without sulfuric acid washing. Further, the change in reflectance at a drawing wavelength of 413 nm was as small as 1.025%.

((Manufacture of photomask))
Next, a photomask 200 was manufactured using the photomask blank 100.
First, ozone cleaning was performed on the prepared photomask blank 100 using an ozone cleaning liquid.
This ozone cleaning was performed as follows. First, an ozone cleaning liquid was dropped near the rotation center of the photomask blank 100 rotated at a low speed, and the ozone cleaning liquid was applied to the entire surface of the second reflection reduction layer 32 of the photomask blank 100 by spreading by rotation. . After that, the photomask blank 100 is rotated at a low speed while supplying the cleaning liquid until the cleaning end time, and cleaning is continued. After the cleaning time is completed, pure water is supplied to replace the ozone cleaning liquid with pure water, and finally spin drying is performed. went.
At this stage (FIG. 3A), a defect inspection was performed. The defect inspection was performed on an area of 790 mm × 910 mm, and defects having a size of 10 μm or more were inspected visually by applying strong light to the film surface in a dark room. As a result, the number of detected defects of this photomask blank 100 was zero.

  Next, as illustrated in FIG. 3B, a resist film 4 having a thickness of 1000 nm was formed on the second CrCON layer 32 of the photomask blank 100. A desired pattern such as a circuit pattern was drawn on the resist film 4 using a laser drawing machine, and further developed and rinsed to form a predetermined resist pattern 4a (FIG. 3C). Here, the wavelength of the drawing light of the used laser drawing machine is 413 nm. Thereafter, a CrN layer (lower light shielding layer 21), a CrC layer (upper light shielding layer 22), a first CrCON layer (first reflection reduction layer 31), and a second CrCON layer ( The light shielding film 5 consisting of a total of four layers of the second reflection reduction layer 32) is integrally patterned by wet etching using the resist pattern 4a as a mask to form the light shielding film pattern 5a (FIG. 3D). . Therefore, the light shielding film pattern 5a includes a lower light shielding layer pattern 21a made of CrN, an upper light shielding layer pattern 22a made of CrC (the above two layers are the light shielding layer pattern 2a), and a first reflection reduction layer pattern made of the first CrCON. 31a and a second reflection reduction layer pattern 32a made of the second CrCON (the two layers are the reflection reduction layer pattern 3a). Here, as the wet etching, a chromium etching solution containing ceric ammonium nitrate and perchloric acid was used.

  The cross-sectional shape of the light-shielding film pattern 5a with the resist pattern 4a remaining was observed using a scanning electron microscope using a sample manufactured in the same manner up to the above steps. As a result, no bottom skirting was observed, and a light shielding film pattern 5a having a vertical cross-sectional shape was obtained.

  Thereafter, the resist pattern was peeled off (FIG. 3E), and a photomask 200 in which the light shielding film pattern 5a was formed on the synthetic quartz glass substrate 1 was obtained.

The dimensional variation (CD variation) of the mask pattern of this photomask was measured by SIR8000 manufactured by Seiko Instruments Nano Technology. The CD variation was measured at 5 × 5 points in an 880 mm × 910 mm region excluding the peripheral region of the substrate. In the following examples and comparative examples, the same apparatus and the same evaluation method were used to measure CD variation.
As a result, the CD variation was 0.105 μm. As will be described later in the comparative example, the CD variations in Comparative Example 1 and Comparative Example 2 were 0.125 μm and 0.150 μm, respectively, and the CD variation in Example 1 was good.

((Manufacture of display devices))
The photomask 200 created in Example 1 was set on a mask stage of an exposure apparatus, and pattern exposure was performed on a sample in which a resist film was formed on a substrate of a display apparatus. The exposed resist film was developed to form a resist pattern on the display device substrate. As the exposure light, light having a wavelength of 300 nm or more and 500 nm or less including i-line with a wavelength of 365 nm, h-line with 405 nm, and g-line with 436 nm was used.
The photomask 200 prepared in Example 1 has a high mask pattern dimensional accuracy of 0.105 μm expressed by CD variation, a low reflectance with respect to the exposure light, and zero defects at the stage of the photomask blank. Since there were few defects, the transfer pattern of the resist pattern on the display device substrate was also highly accurate, and there were few defects.

  The resist pattern is transferred to a film to be processed by etching, and through various processes such as formation of an insulating film, a conductive film, introduction of a dopant, or annealing, a high-definition display device having desired characteristics is high. It was possible to manufacture with a yield.

In Example 2, the oxygen content of the CrCON layer that is the first reflection reduction layer 31 and the CrCON layer that is the second reflection reduction layer 32 is changed by changing only the film formation conditions of the sputtering 3 and the sputtering 4 of Example 1. The other examples are the same as those in the first embodiment, including the photomask manufacturing method and the display device manufacturing method. Therefore, the mask pattern light-shielding film 5 is composed of CrN (lower light-shielding layer 21), CrC (upper light-shielding layer 22), first CrCON (first reflection reducing layer 31), and It consists of a total of four layers of second CrCON (second reflection reduction layer 32).

The film forming conditions of Example 2 are shown below.
Sputtering 1: Ar = 65 sccm, N ₂ = 15 sccm, Power = 1.5 kW, sample moving speed = 400 mm / min
Sputtering 2: Ar / CH ₄ (4.9%) = 31 sccm, Power = 8.5 kW, sample moving speed = 400 mm / min
Sputtering 3: Ar / CH ₄ (5.5%) = 34.8 sccm, N ₂ = 32.2 sccm, CO ₂ = 4.5 sccm, Power = 1.74 kW, sample moving speed = 400 mm / min
Sputtering 4: Ar / CH ₄ (5.5%) = 34.8 sccm, N ₂ = 32.2 sccm, CO ₂ = 4.5 sccm, Power = 1.74 kW, sample moving speed = 400 mm / min
Here, the sputter 3 and the sputter 4 are formed under the same conditions, but are a laminated film formed by dividing the third sputter chamber SP3, the fourth sputter chamber SP4, and the chamber.
In addition, as in Example 1, this film formation condition is characterized by the low flow rate of oxygen component and low power in the sputter 3 and sputter 4 which are film formation processes of the reflection reducing layer 3. The film is being formed. This condition is the basis for a dense film with few defects.

The photomask blank manufactured under the film formation conditions was evaluated under the same conditions as the evaluation methods in Example 1. As a result, the oxygen contents of the first CrCON (first reflection reduction layer 31) and the second CrCON (second reflection reduction layer 32) were equal because the film formation conditions were the same. That is, each layer has an oxygen distribution as in Example 1, but the first CrCON and the second CrCON have the same oxygen distribution.
The film surface reflectance of the mask pattern light-shielding film 5 before ozone treatment (before ozone treatment) is 8.7% at a wavelength of 436 nm, and the reflectance at 413 nm, which is a drawing wavelength described later, is It was 10.5%. These reflectances are good values that are sufficiently low to perform mask pattern drawing with high accuracy, and exposure light of a display device mainly composed of an i-line having a wavelength of 365 nm, an h-line having a wavelength of 405 nm, and a g-line having a wavelength of 436 nm. It was a low reflectance that was sufficiently acceptable.
Further, the amount of change in reflectance at a wavelength of 436 nm caused by performing ozone treatment for 60 minutes is an increase of 1.3%, and the amount of change in reflectance at a writing wavelength of 413 nm is an increase of 0.41%. Both were small enough. Further, the change in reflectance at a wavelength of 436 nm caused by performing the sulfuric acid treatment for 15 minutes is a decrease of 1.5%, and the change in reflectance at a wavelength of 413 nm is a decrease of 1.35%. Both were small enough. And the defect number of 10 micrometers or more of the photomask blank of Example 2 which performed ozone treatment was zero.
In addition, the CD variation of the photomask manufactured by the same method as in Example 1 using the photomask blank manufactured by the method of Example 2 was a sufficiently small CD variation of 0.112 μm in the same evaluation as in Example 1. It was.

  As described above, the photomask blank manufactured by the method of Example 2 is highly resistant to ozone cleaning with little change in reflectivity due to ozone cleaning, and has excellent defect quality with zero visual defects. there were. In addition, a photomask manufactured using this photomask blank has a highly accurate mask pattern with sufficiently small CD variation. For this reason, a high-definition display device having desired characteristics can be manufactured with a high yield.

Example 3 is an example of a photomask blank assuming a laser drawing machine in which the wavelength of a laser (drawing light) used when manufacturing a photomask is 355 nm. A photomask blank was manufactured in the same manner as in Example 1 except that the film formation conditions were adjusted so that the minimum value of the film surface reflectance of the light shielding film 5 for the mask pattern was around 355 nm. The structure of the light shielding film 5 for the mask pattern is the same as that of Example 1, and CrN (lower light shielding layer 21), CrC (upper light shielding layer 22), and first CrCON (first light shielding layer) are sequentially formed on the substrate. The reflection reduction layer 31) and the second CrCON (second reflection reduction layer 32) are composed of a total of four layers.
The film forming conditions of Example 3 are shown below.
Sputtering 1: Ar = 65 sccm, N ₂ = 15 sccm, Power = 1.5 kW, sample moving speed = 400 mm / min
Sputtering 2: Ar / CH ₄ (4.9%) = 31 sccm, Power = 8.5 kW, sample moving speed = 400 mm / min
Sputtering 3: Ar / CH ₄ (5.5%) = 34.8 sccm, N ₂ = 32.2 sccm, CO ₂ = 4.5 sccm, Power = 1.45 kW, Sample moving speed = 400 mm / min
Sputtering 4: Ar / CH ₄ (5.5%) = 34.8 sccm, N ₂ = 32.2 sccm, CO ₂ = 4.5 sccm, Power = 1.45 kW, sample moving speed = 400 mm / min
Here, the difference in film forming conditions from Example 2 is that the power of the sputters 3 and 4 is lowered.

The photomask blank manufactured under the film formation conditions was evaluated under the same conditions as the evaluation methods in Example 1. As a result, the chromium content, the oxygen content distribution, and the nitrogen content distribution of the first CrCON (first reflection reduction layer 31) and the second CrCON (second reflection reduction layer 32) are the same as those in the first embodiment. It was the same tendency as the chromium content, oxygen content distribution, and nitrogen content distribution of one CrCON (first reflection reduction layer 31) and second CrCON (second reflection reduction layer 32). That is, the oxygen content of the first CrCON (first reflection reduction layer 31) was larger than the oxygen content of the second CrCON (second reflection reduction layer 32).
As a result of measuring the film surface reflectance of the light shielding film 5 for the mask pattern in the same manner as in Example 1, the reflectance in the untreated ozone treatment (when the ozone treatment is not performed) is 11 in the drawing wavelength band of 350 nm to 450 nm. 0.0% or less. The wavelength at which the reflectance is minimum is 360 nm, and the reflectance at that time is 9.0%. The reflectance at a wavelength of 436 nm was 10.0%. The reflectance at 355 nm, which is a drawing wavelength described later, was 9.3%. These reflectances are good values that are sufficiently low to perform mask pattern drawing with high accuracy, and exposure light of a display device mainly composed of an i-line having a wavelength of 365 nm, an h-line having a wavelength of 405 nm, and a g-line having a wavelength of 436 nm. It was a low reflectance that was sufficiently acceptable.
In addition, the amount of change in reflectance at a wavelength of 436 nm generated by performing ozone treatment for 60 minutes is an increase of 1.0%, and the amount of change in reflectance at a drawing wavelength of 355 nm is an increase of 1.5%. Both were small enough. In addition, the change in reflectance at a wavelength of 436 nm caused by performing sulfuric acid treatment for 15 minutes is a decrease of 0.85%, and the change in reflectance at a wavelength of 413 nm is a decrease of 1.5%. Both were small enough. And the defect number of 10 micrometers or more of the photomask blank of Example 3 which performed ozone treatment was zero.
Further, the CD variation of the photomask manufactured by the same method as in Example 1 using the photomask blank manufactured by the method of Example 3 was a sufficiently small CD variation of 0.105 μm in the same evaluation as in Example 1. It was. When manufacturing the photomask, a laser drawing machine having a drawing wavelength of 355 nm was used.

  As described above, the photomask blank manufactured by the method of Example 3 is highly resistant to ozone cleaning with little change in reflectivity due to ozone cleaning, and has excellent defect quality with zero visual defects. there were. In addition, a photomask manufactured using this photomask blank has a highly accurate mask pattern with sufficiently small CD variation. For this reason, a high-definition display device having desired characteristics can be manufactured with a high yield.

The photomask blank 100 of Example 4 is a photomask blank in which a phase shift film, which is a functional film for adjusting the transmittance and phase shift amount of exposure light, is formed between the substrate 1 and the light shielding film 5 for the mask pattern. Therefore, it is a so-called phase shift mask blank. The mask pattern light-shielding film 5 formed on the phase shift film is the same light-shielding film as in the first embodiment, and a description thereof will be omitted.
A two-layer phase shift film made of MoSiN was formed on a substrate 1 made of a synthetic quartz glass substrate of the same size as in Example 1 using a large in-line sputtering apparatus. When forming the phase shift film, the sputter targets in the first sputter chamber SP1 and the second sputter chamber SP2 are changed to sputter targets 331 and 332 made of molybdenum silicide (MoSi), respectively, under the following film forming conditions. A phase shift film was formed.
Sputtering 1: Ar = 50 sccm, N ₂ = 90 sccm, Power = 8.0 kW, sample moving speed = 400 mm / min
Sputtering 2: Ar = 50 sccm, N ₂ = 90 sccm, Power = 8.0 kW, sample moving speed = 400 mm / min
Under the above-described film forming conditions, a first phase shift film made of a molybdenum silicide nitride film (MoSiN) having a film thickness of 55 nm is formed on the substrate 1 in the sputtering 1, and a molybdenum silicide film having a film thickness of 55 nm is formed in the sputtering 2. A second phase shift film made of a nitride film (MoSiN) was formed, and a phase shift film having a total film thickness of 110 nm made of two layers of molybdenum silicide nitride films (MoSiN) was formed on the substrate 1.
With respect to the substrate on which this phase shift film was formed, transmittance and phase difference were measured by MPM-100 manufactured by Japan Lasertec. The transmittance and the phase difference were measured using a 6025 size dummy substrate produced at the same time. As a result, the transmittance was 5.5% (wavelength: 365 nm), and the phase difference was 180 ° (wavelength: 365 nm).
Next, the same light-shielding film 5 for the mask pattern as that in Example 1 was formed on the phase shift film, and a phase shift mask blank was manufactured. When forming the light shielding film 5 for the mask pattern, the sputter targets 331 and 332 of the first sputter chamber SP1 and the second sputter chamber SP2 are replaced with chromium (Cr), and the mask pattern is formed on the phase shift film. A light shielding film 5 was formed.

  The obtained phase shift mask blank was evaluated under the same evaluation method and conditions as in Example 1. The chromium content, oxygen content distribution, and nitrogen content distribution of the light shielding film 5 for the mask pattern are the same, and the change in the reflectance of the light shielding film 5 after the ozone treatment and after the sulfuric acid treatment was the same result. .

Next, a phase shift mask was manufactured using this phase shift mask blank.
First, similarly to Example 1, the prepared phase shift mask blank was subjected to ozone cleaning using an ozone cleaning liquid.
Next, a resist film 4 having a film thickness of 1000 nm was formed on the light shielding film 5. A desired pattern such as a circuit pattern was drawn on the resist film 4 using a laser drawing machine, and further developed and rinsed to form a predetermined resist pattern 4a. Thereafter, the light shielding film 5 was patterned by wet etching with a chromium etching solution containing ceric ammonium nitrate and perchloric acid using the resist pattern as a mask to form a preliminary light shielding film pattern.
Then, without removing the resist pattern, using the resist pattern and the light-shielding film pattern as a mask, the phase shift film is changed to a fluorine compound such as hydrofluoric acid, hydrofluoric acid, ammonium hydrogen fluoride, hydrogen peroxide, Patterning was performed by wet etching using an etching solution to which an oxidizing agent such as nitric acid or sulfuric acid was added, thereby forming a phase shift film pattern.
Next, without removing the resist pattern, the preliminary light-shielding film pattern is again etched with the above-mentioned chromium etching solution to form a light-shielding film pattern having a desired pattern line width at the center of the phase shift film pattern. did.
Finally, the resist pattern was peeled off to obtain a phase shift mask in which a phase shift film pattern and a light shielding film pattern were formed on the synthetic quartz glass substrate 1.

  As a result of measuring and evaluating the dimensional variation (CD variation) of the phase shift film pattern of this phase shift mask in the same manner as in Example 1, the CD variation was 0.088 μm. This phase shift mask had a highly accurate phase shift film pattern with sufficiently small CD variation. Therefore, a high-definition display device having desired characteristics as in Example 1 could be manufactured with a high yield.

(Comparative Example 1)
Comparative Example 1 is an example in which only the film formation conditions of Sputter 3 and Sputter 4 of Example 1 are interchanged with each other to manufacture a photomask blank. Otherwise, a photomask manufacturing method and a display device manufacturing method are used. All of them are the same as in the first embodiment. That is, in Comparative Example 1, the sputter 3 and the sputter 4 were formed under the conditions of the sputter 4 and the sputter 3 in Example 1, respectively, and the others were the same as those in Example 1. Therefore, the light shielding film 5 for the mask pattern is composed of CrN (lower light shielding layer 21), CrC (upper light shielding layer 22), first CrCON (first reflection reduction layer 31), which are sequentially formed on the substrate 1. And the second CrCON (second reflection reduction layer 32) in total, the first CrCON of Comparative Example 1 is the second CrCON of Example 1, and the second of Comparative Example 1 The CrCON of the first embodiment is the first CrCON of the first embodiment.

The film forming conditions of Comparative Example 1 are shown below.
Sputtering 1: Ar = 65 sccm, N ₂ = 15 sccm, Power = 1.5 kW, sample moving speed = 400 mm / min
Sputtering 2: Ar / CH ₄ (4.9%) = 31 sccm, Power = 8.5 kW, sample moving speed = 400 mm / min
Sputtering 3: Ar / CH ₄ (5.5%) = 31 sccm, N ₂ = 8 sccm, O ₂ = 3 sccm, Power = 1.95 kW, sample moving speed = 400 mm / min
Sputtering 4: Ar / CH ₄ (5.5%) = 31 sccm, N ₂ = 8 sccm, O ₂ = 3 sccm, Power = 1.5 kW, sample moving speed = 400 mm / min

The photomask blank manufactured under the film formation conditions was evaluated under the same conditions as the evaluation methods in Example 1. As a result, the chromium content, the oxygen content distribution, and the nitrogen content distribution of the first CrCON (first reflection reduction layer 31) and the second CrCON (second reflection reduction layer 32) are the same as those in the first embodiment. The Cr content, oxygen content distribution, and nitrogen content distribution of the second CrCON (second reflection reduction layer 32) and the first CrCON (first reflection reduction layer 31) were obtained. For example, the oxygen content of the first CrCON (first reflection reduction layer 31, lower reflection reduction layer) of Comparative Example 1 is the same as the second CrCON (second reflection reduction layer 32, upper reflection reduction layer). Less than the oxygen content. The change in reflectance at a wavelength of 436 nm generated by performing ozone treatment for 60 minutes was sufficiently small, an increase of 1.2%, but the reflectance at a wavelength of 436 nm was as high as 15% or more, and the mask pattern The drawing accuracy and the exposure transfer accuracy to the display device substrate are reduced. Further, the number of defects of 10 μm or more in the photomask blank of Comparative Example 1 subjected to ozone treatment was one.
The CD variation of the photomask manufactured by the same method as in Example 1 using the photomask blank manufactured by the method of Comparative Example 1 was 0.125 μm in the same evaluation as in Example 1.

  As described above, the photomask blank manufactured by the method of Comparative Example 1 had a high reflectivity of 15% or more, although the change in reflectivity accompanying ozone cleaning was small. Therefore, the photomask manufactured using this photomask blank had a CD variation of the mask pattern of 0.125 μm, which was inferior to the first and second embodiments. Also, the number of defects in the photomask blank stage was one, but was larger than zero in Example 1 and Example 2. Since the defect size to be measured is as large as 10 μm, the difference of one defect has a great influence on the yield of the display device. For this reason, the yield of a high-definition display device having desired characteristics is inferior to those of the first and second embodiments.

(Comparative Example 2)
Comparative Example 2 is a case where a single reflection reduction layer is used, and the layer structure of the light shielding layer 2 made of CrN (lower light shielding layer 21) and CrC (upper light shielding layer 22) sequentially formed on the substrate 1 is an example. Same as 1. However, the film forming conditions of CrC which is the upper light shielding layer 22 are different from those in the first embodiment. Only the CrN that is the lower light shielding layer 21 is the same as that of the first embodiment in the film formation conditions. Other than that, including the photomask blank evaluation method, photomask manufacturing method, and display device manufacturing method, all were the same as in Example 1. That is, in Comparative Example 2, the film forming conditions for Sputter 2 and Sputter 3 are changed from those in Example 1, and the film forming process is skipped only by passing the sample 301 into the sputter chamber SP4. Made the same. The mask pattern light shielding film 5 includes a total of three layers of CrN (lower light shielding layer 21), CrC (upper light shielding layer 22), and CrCON (reflection reduction layer 3) sequentially formed on the substrate 1.

The film forming conditions of Comparative Example 2 are shown below.
Sputtering 1: Ar = 65 sccm, N ₂ = 15 sccm, Power = 1.5 kW, sample moving speed = 400 mm / min
Sputtering 2: Ar / CH ₄ (4.9%) = 31 sccm, Power = 8.5 kW, sample moving speed = 400 mm / min
Sputtering 3: Ar / CH ₄ (4.9%) = 34.8 sccm, N ₂ = 32.2 sccm, O ₂ = 5.5 sccm, Power = 3.6 kW, sample moving speed = 400 mm / min
What is characteristic about the film formation conditions is that the reflection reducing layer 3 is a single layer film (film formed in one sputter chamber) and the sputter 3 that is a film formation process is performed in the first embodiment and the first embodiment. 2, the film is formed under conditions where the flow rate of the oxygen component is high and the power is nearly double (1.8 to 2.4 times).

  The photomask blank manufactured under the film formation conditions was evaluated under the same conditions as the evaluation methods in Example 1. As a result, the spectral reflectance characteristic curve of the film surface of the mask pattern light-shielding film 5 that has not been subjected to ozone treatment is shown in FIG. It was almost the same as the spectral reflectance characteristic curve of the film surface of the film 5, and was 12% or less in the laser drawing wavelength band of 350 nm to 450 nm. The wavelength at which the reflectance is minimum is 430 nm, which is the same as in Example 1, and the reflectance at that time is 8.5%, which is 1.24% higher than that in Example 1. The reflectance at a wavelength of 436 nm was 8.5%, which was the same value as the minimum value. The reflectance at 413 nm, which is the drawing wavelength, was 8.69%. On the other hand, the spectral reflectance characteristics of the film surface of the mask pattern light-shielding film 5 when the ozone cleaning process was performed were different from those in Example 1. The characteristic that the wavelength at which the reflectance is minimized shifts to the short wavelength side with the increase of the ozone cleaning treatment time is the same as that in the first embodiment, but the minimum value of the reflectance at that time is the same as that in the first embodiment. On the contrary, it became higher as the ozone cleaning time increased. Specifically, the wavelengths that minimize the reflectance when the ozone cleaning time is 0 minutes, 30 minutes, 60 minutes, and 120 minutes are 430 nm, 400 nm, 358 nm, and 309 nm, respectively, and the minimum reflectance at that time is 8.5%, 10.2%, 11.7%, and 15.4%. As a result of the spectral reflectance characteristics, the amount of change in reflectance at a wavelength of 436 nm caused by performing ozone treatment for 60 minutes is an increase of 6.7%, and the increase in reflectance at a drawing wavelength of 413 nm is 4%. .7% is large, and the accuracy of drawing the mask pattern and the accuracy of exposure transfer to the display device substrate are lowered. Further, the photomask blank of Comparative Example 2 subjected to ozone treatment had 20 or more defects of 10 μm or more, and there were many defects.

  A photomask was manufactured by the same method as in Example 1 using the photomask blank manufactured by the method of Comparative Example 2. Further, using the sample produced in the same manner as in this comparative example, the cross-sectional shape of the light shielding film pattern 5a with the resist pattern 4a remaining was observed using a scanning electron microscope. As a result, it was a cross-sectional shape in which skirting was slightly observed and the surface layer portion was missing. Further, a chromium residue was observed on the substrate 1. Regarding the CD variation, since the change in reflectance by ozone cleaning was large, it was 0.150 μm in the same evaluation as in Example 1.

  As described above, the photomask blank manufactured by the method of Comparative Example 2 has a large reflectance with ozone cleaning, the number of defects is 20 or more, and the defect quality is inferior. Since the photomask manufactured using this photomask blank has a large change in reflectance due to ozone cleaning, the CD variation of the mask pattern is 0.150 μm, which is inferior to those of Example 1 and Example 2. . For this reason, the manufacturing yield of high-definition display devices having desired characteristics was low.

  DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Light shielding layer, 2a ... Light shielding layer pattern, 3 ... Reflection reduction layer, 3a ... Reflection reduction layer pattern, 4 ... Resist film, 4a ... Resist pattern, 5a ... Light shielding film pattern, 21 ... Lower layer light shielding layer ( CrN), 21a... Lower layer light shielding layer pattern (CrN pattern), 22... Upper layer light shielding layer (CrC), 22a... Upper layer light shielding layer pattern (CrC pattern), 31. Reflection reduction layer pattern (CrCON pattern), 32 ... second reflection reduction layer (CrCON), 32a ... second reflection reduction layer pattern (CrCON pattern), 100 ... photomask blank, 200 ... photomask, 300 ... inline Sputtering apparatus, 301 ... sample, 311 ... shutter, 312 ... shutter, 321 ... first gas inlet, 322 ... second gas guide 323 ... 3rd gas introduction port, 324 ... 4th gas introduction port, 331 ... 1st sputter target, 332 ... 2nd sputter target, 333 ... 3rd sputter target, 334 ... 4th sputter target, LL ... carrying-in chamber , UL ... unloading chamber, SP1 ... first sputter chamber, SP2 ... second sputter chamber, SP3 ... third sputter chamber, SP4 ... fourth sputter chamber, BU1 ... first buffer chamber, BU2 ... second buffer chamber, BU3 ... Third buffer chamber

Claims (12)

A photomask blank comprising a transparent substrate made of a material substantially transparent to exposure light, a light shielding layer on the transparent substrate, and a reflection reducing layer on the light shielding layer,
The light shielding layer is made of a chromium material containing chromium,
The reflection reduction layer is made of a chromium oxide material containing less oxygen than the light shielding layer and containing oxygen,
The reflection reducing layer is a laminated film formed by laminating a plurality of layers, the oxygen content of the light-shielding layer side Ri der than the oxygen content of the reflection reducing layer surface,
The reflection reduction layer is characterized in that at least one of a film thickness and an oxygen content is adjusted so that a bottom peak wavelength at which a film surface reflectance is minimum falls within a wavelength range of 350 nm to 550 nm. Photomask blank.   The reflection reducing layer is characterized in that at least one of a film thickness and an oxygen content is adjusted so that a bottom peak wavelength at which the film surface reflectance is minimum falls within a wavelength range of 365 nm to 550 nm. The photomask blank according to claim 1. The reflection reduction layer includes a high chromium oxide layer containing oxygen in an amount of 35 atomic percent to less than 65 atomic percent and a low chromium oxide layer containing oxygen in an amount of 10 atomic percent to 50 atomic percent from the light shielding layer side. the photomask blank of claim 1 or 2, characterized in that a structure. The photomask blank according to any one of claims 1 to 3 , wherein the reflection reducing layer is made of a chromium oxynitride material further containing nitrogen. The photomask blank according to claim 4 , wherein the reflection reducing layer contains 2 atom% or more and 30 atom% or less of nitrogen. The light shielding layer includes a photo mask according to any one of claims 1 to 5, characterized in that it has the reflection reducing layer side chromium layer nitride nitrogen is abundant in the transparent substrate side as compared with the blank. The photomask blank according to any one of claims 1 to 6 , wherein each element contained in the light shielding layer and the reflection reducing layer has a composition gradient continuously. Photos of any one of claims 1 to 7, characterized in that it has a functional film for adjusting at least one of transmission or phase shift of the exposure light between the transparent substrate and the light shielding layer Mask blank. The photomask blank according to any one of claims 1 to 8 , wherein the photomask blank is an original plate of a photomask for manufacturing a display device. Using the photomask blank according to any one of claims 1 to 9 , and forming a resist film on the photomask blank;
Drawing a desired pattern with light;
Performing a development to form a resist pattern on the photomask blank; and
Patterning the light shielding layer and the reflection reducing layer by etching;
A photomask manufacturing method comprising manufacturing a photomask. The photomask manufacturing method according to claim 10, wherein the drawing step includes laser drawing using a laser having a wavelength selected from a wavelength range of 350 nm to 550 nm. A photomask manufactured by the method for manufacturing a photomask according to claim 10 or 11 is placed on a mask stage of an exposure apparatus , and a single such as an i-line with a wavelength of 365 nm, an h-line with 405 nm, and a g-line with 436 nm A display characterized by having an exposure step of exposing and transferring a transfer pattern formed on the photomask to a resist formed on a display device substrate using light of a wavelength or composite light including these. Device manufacturing method.

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