JP2018049111A - Photomask blank, method of manufacturing photomask blank, method of manufacturing photomask using these, and method of manufacturing display unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photomask blank capable of verticalization of a mask pattern cross-sectional shape, a method of manufacturing the same, a method of manufacturing a photomask using these, and a method of manufacturing a display unit.SOLUTION: The photomask blank includes: a transparent substrate 1; a light shielding layer 2; and a reflex-reducing layer 3, where the light-shielding layer 2 comprises a chromium compound containing chromium, and nitrogen, the reflex-reducing layer 3 comprises a chromium compound containing chromium, nitrogen, and oxygen, the content of chromium contained in the reflex-reducing layer 3 is less than a content of chromium contained in the light-shielding layer 2, the reflex-reducing layer 3 is composed of a laminated membrane obtained by laminating a plurality of layers, the content of oxygen contained in an upper layer part 32 of a surface side of the reflex-reducing layer 3 is greater than a content of oxygen contained in a lower part 31 of a light-shielding layer side of the reflex-reducing layer 3, and the reflex-reducing layer has a region substantially not containing carbon on a surface side of the upper layer part 32, the region having an oxygen concentration continuously increasing toward a surface-most face, and a maximum value of a ratio (O/N) of oxygen to nitrogen of not less than 5.SELECTED DRAWING: Figure 1

Description

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

  For example, in a display device such as an FPD (Flat Panel Display) represented by an LCD (Liquid Crystal Display), a high-definition and a high-speed display are rapidly progressing along with an increase in screen size and a wide viewing angle. 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.

  Patent Document 1 discloses a technique relating to such a photomask blank, a method for manufacturing a photomask using the same, and a method for manufacturing a display device.

JP2016-105158

In order to manufacture the display device as described above with high yield by reducing pixel defects and circuit defects, a photomask with high pattern accuracy is required. Therefore, there is a need for a photomask blank that satisfies the required optical performance, has few defects, and can form a highly accurate pattern.
One factor that affects the optical performance and pattern accuracy in a photomask is the vertical cross-sectional shape of the pattern.
In general, the size of a transfer pattern in manufacturing a display device is larger than the size of a transfer pattern required for manufacturing a semiconductor device. However, while a reduction projection mask is usually used as a photomask for manufacturing a semiconductor device, a mask for normal exposure (same size mask) is usually used as a photomask for manufacturing a display device. Due to the difference in mask magnification, in a photomask for manufacturing a display device, the inclination of the cross-sectional shape of the mask pattern is related to the aspect ratio of the mask pattern (ratio of the height H to the width W of the mask pattern: H / W). The width of the region becomes larger when transferred with respect to that of the reduced projection mask. In addition, in a photomask for manufacturing a display device (same size mask), the inclination of the cross-sectional shape of the mask pattern itself also affects the transfer performance. Therefore, it is important to make the inclination as close to vertical as possible in order to meet the demand for forming a fine pattern in display device manufacturing.

  In view of the above points, the present invention is capable of forming a mask pattern having a cross-sectional shape close to vertical, and thereby a photomask blank capable of manufacturing a photomask capable of forming a fine pattern with high accuracy, and its manufacture. It aims to provide a method. It is another object of the present invention to provide a photomask manufacturing method and a display device manufacturing method using these.

(Configuration 1)
A photomask blank having a transparent substrate made of a material that is substantially transparent to exposure light, a light shielding layer on the transparent substrate, and a reflection reducing layer on the light shielding layer, wherein the light shielding layer comprises: The reflection reduction layer is made of a chromium compound containing chromium, nitrogen, and oxygen, and the content of chromium contained in the reflection reduction layer is chromium contained in the light shielding layer. The reflection reducing layer is a laminated film in which a plurality of layers are laminated, and the oxygen content contained in the upper layer portion on the surface side of the reflection reducing layer is the light shielding layer side of the reflection reducing layer. More than the oxygen content contained in the lower layer part, having a region substantially free of carbon on the surface side of the upper layer part, the region, the oxygen continuously increases toward the outermost surface, and Ratio of oxygen to nitrogen (O / N Photomask blank, wherein a maximum value of 5 or more.

(Configuration 2)
2. The photomask blank according to Configuration 1, wherein a minimum value of the ratio of oxygen to nitrogen (O / N) is 2 or more.

(Configuration 3)
The photomask blank according to Configuration 1 or 2, further comprising a transmittance adjusting layer for adjusting the transmittance between the transparent substrate and the light shielding layer.

(Configuration 4)
The photomask blank according to Configuration 1 or 2, further comprising a phase adjusting layer for adjusting a phase difference between the transparent substrate and the light shielding layer.

(Configuration 5)
The photomask blank according to Configuration 3 or 4, wherein the transmittance adjusting layer and the phase adjusting layer are made of a material having etching selectivity with respect to the light shielding layer.

(Configuration 6)
The photomask blank according to any one of Structures 1 to 5, wherein a resist layer is formed on the reflection reducing layer.

(Configuration 7)
7. The photomask blank according to Configuration 6, wherein the resist layer is coated with a resist that does not contain a surfactant.

(Configuration 8)
It is a manufacturing method of the photomask blank as described in any one of Claim 1 to 7, Comprising: The process of preparing the said transparent substrate, The process of forming the said light shielding layer on the main surface of the said transparent substrate, Forming the reflection reduction layer on a light shielding layer, and forming a lower layer portion of the reflection reduction layer by sputtering using a chromium target in a mixed gas atmosphere containing carbon dioxide gas and nitrogen-based gas. And a step of forming the upper layer portion of the reflection reducing layer by sputtering using a chromium target in a mixed gas atmosphere containing an oxygen-based gas and a nitrogen-based gas. Manufacturing method.

(Configuration 9)
A step of forming a resist layer on the photomask blank using the photomask blank according to any one of configurations 1 to 5 or the photomask blank produced by the production method according to claim 8; A step of drawing a desired pattern on the resist layer, a step of performing development to form a resist pattern on the photomask blank, and etching the light shielding layer and the reflection reducing layer based on the resist pattern And a step of patterning to manufacture a photomask.

(Configuration 10)
A step of drawing a desired pattern on the resist layer using the photomask blank according to Configuration 6 or 7, a step of performing development to form a resist pattern on the photomask blank, and the resist pattern And a step of patterning the light shielding layer and the reflection reducing layer by etching based on the method, and manufacturing a photomask.

(Configuration 11)
The method for producing a photomask according to Configuration 9 or 10, wherein the resist layer is coated with a resist not containing a surfactant.

(Configuration 12)
A photomask manufactured by the photomask manufacturing method according to any one of Structures 9 to 11 is placed on a mask stage of an exposure apparatus, and a transfer pattern formed on the photomask is formed on a display device substrate. A method for manufacturing a display device, comprising: an exposure step of exposing and transferring to a resist that has been exposed.

  By manufacturing a photomask using the photomask blank of the present invention, it is possible to provide a photomask suitable for transfer characteristics and miniaturization because the pattern cross-sectional shape is nearly vertical. Further, by manufacturing a display device using the photomask, a high-definition display device can be manufactured with a high yield.

FIG. 1 is a cross-sectional view of a main part showing a schematic configuration of a photomask blank according to Embodiment 1 of the present invention The 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 Cross-sectional structure diagram of main parts showing a photomask manufacturing process according to Embodiment 2 of the present invention Characteristic diagram showing element distribution of film of photomask blank in Example 1 The figure which showed the ratio of the element distribution of nitrogen and oxygen of the photomask blank in Example 1 Cross-sectional photograph showing the cross-sectional shape of the edge portion of the light-shielding film pattern of Example 1 Characteristic diagram showing element distribution of photomask blank film in comparative example Cross-sectional photograph showing the cross-sectional shape of the edge portion of the light-shielding film pattern of the comparative example

  Hereinafter, embodiments of the present invention will be specifically described 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.

<Embodiment 1>
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 divided into a transparent substrate 1 made of a material transparent to exposure light, a light shielding layer 2 formed on the transparent substrate 1, and a reflection reducing layer 3 formed thereon. Become.

The light shielding layer 2 is composed of a chromium compound containing at least chromium and nitrogen, and has a function of absorbing exposure light and shielding it. As the chromium compound constituting the light shielding layer 2, chromium nitride (CrN), chromium oxynitride (CrON), or the like can be used. By containing nitrogen in the light shielding layer 2, the wet etching rate with respect to the chromium etching solution can be increased. In addition, when the light shielding layer 2 contains nitrogen, a film controlled so as to reduce the crystal grains can be formed. The inclusion of nitrogen in the light shielding layer 2 is also preferable from the viewpoint of relaxing the film stress. From the above viewpoint, chromium nitride (CrN) containing no oxygen is preferable, but in the case of chromium oxynitride (CrON), the oxygen content is 10 atomic% or less, preferably 8 atomic% or less, more preferably 5 atomic%. The following is desirable.
The elements contained in the light shielding layer 2 may be compositionally inclined. When the composition is inclined, the composition may be continuously inclined (distributed) or may be distributed stepwise. When the composition has a gradient distribution continuously, the wet etching rate in the mask pattern film thickness direction also changes continuously, and it is easy to obtain a smooth and nearly vertical mask pattern shape. On the other hand, when the composition distribution is stepwise, the process of forming the light shielding layer is stabilized and it is easy to improve the manufacturing quality. Therefore, the process necessary for PQC (Process Quality Control) can be simplified. There is a feature.

The reflection reducing layer 3 is made of a chromium compound containing chromium, nitrogen, and oxygen, and has a function of preventing reflection of mask pattern drawing light (laser drawing light). The reflection reducing layer 3 also has an antireflection function for exposure light when a display device is manufactured. The chromium content of the reflection reducing layer 3 is less than the chromium content of the light shielding layer 2. Alternatively, the light shielding layer 2 is made of a chromium compound containing at least chromium and nitrogen among chromium, nitrogen, and oxygen, and the oxygen content of the reflection reducing layer 3 is larger than the oxygen content of the light shielding layer 2. This is because if the chromium content of the reflection reducing layer 3 is larger than the chromium content of the light shielding layer 2 or the oxygen content of the reflection reducing layer 3 is smaller than the oxygen content of the light shielding layer 2, the mask pattern drawing light ( This is because the reflectance with respect to (laser drawing light) and exposure light is increased.
The reflection reduction layer 3 is configured by a laminated film in which an upper layer portion 32 on the surface side and a lower layer portion 31 on the light shielding layer 2 side are laminated. By using a laminated film, the reflection reducing layer 3 having a thickness capable of obtaining necessary optical performance can be formed with a dense film (formed with low power sputtering power). Thereby, the occurrence of film defects can be suppressed, and the reflection reducing layer 3 has high chemical resistance (resistance to cleaning before resist application by a cleaning liquid containing sulfuric acid such as sulfuric acid or sulfuric acid / sulfuric acid or ozone cleaning liquid). It can be.

The oxygen content contained in the upper layer portion 32 of the reflection reducing layer 3 is larger than the oxygen content contained in the lower layer portion 31, and has a region substantially free of carbon on the surface side of the upper layer portion 32. Then, oxygen continuously increases toward the outermost surface, and the maximum value of the ratio of oxygen to nitrogen (O / N) is 5 or more. With such a configuration, the cross-sectional shape of the mask pattern can be made vertical.
The mask pattern is formed by cleaning the photomask blank, forming a resist layer on the reflection reducing layer 3, and etching the reflection reducing layer 3 based on the resist pattern formed on the resist layer.
Conventionally, a resist containing a surfactant has been used to form this resist layer. This is for improving the wettability at the time of applying the resist. However, the surfactant contained in this resist is a detrimental effect of improving resist coating performance (in-plane film thickness uniformity, defect reduction, etc.) in reducing the thickness of the resist layer for miniaturization of transfer patterns. As a result, when a mask pattern was formed using a resist containing no surfactant, the cross-sectional shape of the mask pattern had a very long skirt as shown in a comparative example (FIG. 8). Tapered shape. This is because wet etching liquid infiltrates into the interface between the resist film and the photomask blank (reflection reduction layer) due to the adhesion problem between the resist and the photomask blank surface (reflection reduction layer), and so on. This is considered to be the cause.
As a result of a detailed study on this problem, as shown in the following examples, a region substantially free of carbon is formed on the surface side of the upper layer portion 32 of the reflection reducing layer 3, and in this region, on the outermost surface. Oxygen continuously increases toward the surface, and the maximum value of the ratio of oxygen to nitrogen (O / N) is set to 5 or more, thereby improving the adhesion between the resist and the photomask blank surface (reflection reduction layer). As a result, the cross-sectional shape of the mask pattern has been dramatically improved (verticalized). Further, by increasing the ratio of oxygen to nitrogen, a dense film can be formed and a film having excellent chemical resistance can be obtained.
In FIG. 1, the upper layer portion 32 and the lower layer portion 31 are depicted as being separated into two films, but a layer that is continuously changed may be used. Furthermore, a laminated film having three or more layers may be used. The reflection reducing layer 3 is a laminated film, and is a region substantially not containing carbon on the surface side of the upper layer portion of the laminated film, in which oxygen continuously increases toward the outermost surface, and nitrogen Any region may be used as long as the region where the maximum value of the ratio of oxygen to oxygen (O / N) is 5 or more is formed.
From the viewpoint of verticalizing the cross-sectional shape of the mask pattern, preferably, the minimum value of the ratio of oxygen to nitrogen (O / N) in the substantially carbon-free region on the surface side of the upper layer portion 32 of the reflection reducing layer 3 Is 2 or more, and more preferably, the minimum value of the ratio of oxygen to nitrogen (O / N) is 2.5 or more.

  Note that each element contained in the reflection reduction layer 3 also has a smooth (or graded) composition distribution (composition gradient) in the film thickness direction, so that the cross section of the light-shielding film pattern after wet etching is smooth. This is preferable, and the CD accuracy is also improved.

  The light shielding film composed of the light shielding layer 2 and the reflection reducing layer 3 may be a light shielding film for a binary mask, a phase shift mask (for example, a halftone phase shift mask), a Levenson, or the like. Type phase shift mask (Levenson Mask, Alternate Phase Shift Mask) phase shift film (phase adjustment layer for adjusting phase difference), or multi-tone mask (Multi-level Gradation Mask) transmittance control film (transmission) It may be a light shielding film formed on or below the transmittance adjusting layer for adjusting the rate.

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 transparent substrate 1 and the light shielding layer 2. As this functional film, at least one of metal, oxygen, nitrogen, carbon, and fluorine is added to silicon (Si) which is a material having etching selectivity with respect to a chromium material which is a material constituting the light shielding layer 2. Material containing 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. When the transparent substrate 1 is made of synthetic quartz, SiO and SiO ₂ are composed of the same elements as the transparent substrate 1, but the etching rate differs from the etching rate of the substrate due to the difference in bonding state between atoms, etc., and phase difference control is performed. It is possible to control the optical distance (etching depth), which is important for the control, 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 processing of the functional film is performed using a light shielding film pattern containing chromium as an etching mask. For this reason, a wet etching solution is used for processing the functional film such that the functional film has a higher etching rate than the light shielding film 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 transparent substrate 1 is prepared.
The material of the transparent 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 transparent substrate 1. As the cleaning, for example, hydrofluoric acid, silicic hydrofluoric acid, 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 for forming a mask pattern made of a chromium-based material is formed on the main surface of the transparent substrate 1 by a sputtering method. The light shielding film is composed of a laminated film having the light shielding layer 2 and the reflection reducing layer 3, and the reflection reducing layer 3 is also a laminated film. The light shielding layer 2 may also be formed of a laminated film. The number of the light shielding layers 2 and the reflection reduction layers 3 is not particularly limited, but here, as an example, a formation process in the case where the light shielding layers 2 and the two reflection reduction layers 3 are composed of a total of three layers. This 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 in-line type, and includes five chambers: a carry-in chamber LL, a first sputter chamber SP1, a buffer chamber BU, a second sputter chamber SP2, and a carry-out chamber UL. These five chambers are arranged sequentially in sequence.

  The tray 301 on which the transparent substrate 1 is mounted on the substrate holder has a predetermined movement speed (conveyance speed) and a loading chamber LL, a first sputtering chamber SP1, a buffer chamber BU, a second sputtering chamber SP2, and an unloading in the direction of the arrow. It is conveyed in the order of the chambers UL.

The carry-in chamber LL and the first sputter chamber SP1, the second sputter chamber SP2 and the carry-out chamber UL are partitioned by shutters 311 and 312, respectively. The carry-in chamber LL, the sputter chambers SP1 and SP2, the buffer chamber BU, and the carry-out chamber UL are connected to an exhaust device (not shown) that exhausts air.
Sputter targets 331 and 332 are provided in the first sputter chamber SP1, and gas inlets (not shown) corresponding to the respective targets are arranged on the upstream side (left side in the drawing) of each target. In addition, sputter targets 333 and 334 are provided in the second sputter chamber SP2. A gas inlet (not shown) corresponding to the sputter target 333 is arranged on the upstream side (left side in the drawing) with respect to the target, and a gas inlet (not shown) corresponding to the sputter target 334 is downstream with respect to the target. It is arranged on the side (right side in the drawing).

  Next, a process of forming the light shielding layer 2 and the reflection reducing layer 3 (the upper layer portion 32 and the lower layer portion 31) using the in-line type sputtering apparatus 300 will be described.

First, the tray 301 is carried into the carry-in 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 light shielding layer 2 is introduced from the gas introduction port arranged in the first sputtering chamber SP1 at a predetermined flow rate, Further, a predetermined sputtering power is applied to the sputtering target, and the tray 301 is passed over the sputtering targets 331 and 332 at a predetermined speed S1. As the sputtering targets 331 and 332, chromium or a target mainly containing chromium is used. Targets mainly containing chromium include chromium, chromium nitride, and chromium oxide. However, reactive sputtering with a supply gas is easier to control the inclination of the composition distribution as desired. It was. The gas supplied from the gas inlet arranged in the first sputter chamber SP1 is at least nitrogen in order to form a chromium nitride (CrN) layer or chromium oxynitride (CrON) layer containing chromium and nitrogen as the light shielding layer 2. An inert gas such as argon (Ar) gas is added as necessary with a gas containing (N ₂ ). 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 tray 301 passes near the sputter target in the first sputter chamber SP1, the light shielding composed of a chromium-based material having a predetermined thickness is formed on the main surface of the transparent substrate 1 by reactive sputtering. Layer 2 is deposited. At this time, the OD value for light having a wavelength of 436 nm is preferably set to 1.0 or more. This is because the occurrence of transfer defects can be prevented even if transfer is performed with a high exposure amount (high dose amount). The OD value may be ensured depending on the composition, or the OD value may be ensured by controlling the film thickness.

  Thereafter, the tray 301 passes through the buffer chamber BU and moves to the second sputtering chamber SP2.

A predetermined flow rate of a deposition gas necessary for forming the lower layer portion 31 is introduced from a gas inlet corresponding to the sputtering target 333, and a predetermined sputtering power is applied to the sputtering target 333.
In this state, the lower layer portion 31 is formed while the tray 301 is passed over the sputtering target 333 at a predetermined speed S2. As the sputtering target 333, a chromium target is used. In addition, a target containing appropriate additives such as nitrogen and oxygen in chromium can also be used. The gas supplied from the gas inlet corresponding to the sputter target 333 is a chromium oxynitride (CrON) layer containing chromium, oxygen, and nitrogen as the lower layer 31 or a chromium oxynitride carbide (CrON) containing chromium, oxygen, nitrogen, and carbon ( In order to form a (CrCON) layer, an inert gas such as an argon (Ar) gas is added as necessary with a gas containing at least an oxygen-based gas and a nitrogen-based gas. 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 oxygen-based gas is a gas containing oxygen as a constituent element, and the nitrogen-based gas is a gas containing nitrogen as a constituent element. Here, examples of the oxygen-based gas include oxygen (O ₂ ) gas and carbon dioxide (CO ₂ ) gas, and examples of the nitrogen-based gas include nitrogen (N ₂ ) 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, when the film is formed under a condition where 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 lower layer portion 31 a dense film and preventing film defects 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.
When the tray 301 passes through the vicinity of the sputter target 333 by the above steps, a lower layer composed of chromium, nitrogen, and oxygen containing a predetermined thickness on the light shielding layer 2 by reactive sputtering. A portion 31 (CrON layer or CrCON layer) is formed. From the viewpoint of verticalizing the cross-sectional shape, the lower layer portion 31 is preferably chromium oxynitride carbide (CrCON) containing chromium, oxygen, nitrogen, and carbon. As a gas for forming the lower layer portion 31, it is preferable to use a mixed gas containing carbon dioxide (CO ₂ ) gas, nitrogen (N ₂ ) gas, and inert gas (Ar or the like).

Thereafter, the tray 301 moves toward the sputter target 334. A predetermined flow rate of a deposition gas necessary for forming the upper layer 32 is formed from a gas inlet corresponding to the sputtering target 334, and a predetermined sputtering power is applied. In this state, the upper layer portion 32 is formed while the tray 301 is passed over the sputter target 334 at a predetermined speed S3. A chrome target is used as the sputter target 334. In addition, a target containing appropriate additives such as oxygen and nitrogen in chromium can also be used. The gas supplied from the gas inlet corresponding to the sputter target 334 contains chromium, oxygen, and nitrogen as the upper layer portion 32, and has a region containing substantially no carbon on the surface side of the upper layer portion 32. In order to form a (CrON) layer or a chromium oxynitride carbide (CrCON) layer, an inert gas such as an argon (Ar) gas is added as necessary with a gas containing at least an oxygen-based gas and a nitrogen-based gas. 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 oxygen-based gas is a gas containing oxygen as a constituent element, and the nitrogen-based gas is a gas containing nitrogen as a constituent element. Examples of the oxygen-based gas include oxygen (O ₂ ) gas and carbon dioxide (CO ₂ ) gas. Examples of the nitrogen-based gas include nitrogen (N ₂ ) gas, nitrogen dioxide (NO ₂ ) gas, and monoxide. There are nitrogen (NO) gas and the like. In order to have a substantially region not including the carbon on the surface side of the upper portion 32, as the oxygen-containing gas, using oxygen (O ₂₎ gas, as the gas containing nitrogen, nitrogen (N ₂ It is preferred to use a gas. That is, it is preferable to use a mixed gas containing oxygen (O ₂ ) gas, nitrogen (N ₂ ) gas, and inert gas as the gas for forming the upper layer portion 32. When the lower layer portion 31 is a carbon oxynitride chromium carbide (CrCON) layer containing carbon, in order to make the cross-sectional shape vertical, the upper layer portion 32 excluding the surface side includes a chromium oxynitride chromium carbide (CrCON) layer containing a small amount of carbon. can do. In this case, the inert gas contains a small amount of hydrocarbon gas. Examples of the hydrocarbon gas include methane, butane, and propane. When the inert gas contains a trace amount of hydrocarbon-based gas, the content is preferably 15% or less. More preferably, it is desirable to make it 12% or less. 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, when the film is formed under a condition where 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 upper layer portion 32 a dense film and preventing film defects 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.
When the tray 301 passes through the vicinity of the sputter target 334 by the above steps, an upper layer composed of chromium, nitrogen, and oxygen containing a predetermined thickness is formed on the lower layer 31 by reactive sputtering. A portion 32 (CrON layer or CrCON layer) is formed. When the upper layer portion 32 is made of chromium oxynitride carbide (CrCON) containing chromium, oxygen, nitrogen, and carbon, the upper layer portion 32 has a region that does not substantially contain carbon.

Thereafter, the tray 301 is moved to the carry-out chamber UL, after which the shutter 312 is closed and the chamber UL is evacuated and then opened to the atmosphere, and the substrate holder is taken out of the sputtering apparatus 300.
The photomask blank 100 is manufactured by taking out the transparent substrate on which the light-shielding film is formed from the substrate holder, and appropriately performing defect inspection and cleaning as necessary.
The photomask blank 100 manufactured in the first embodiment has high adhesion to the resist film, and the wet etching solution is prevented from entering the interface between the resist film and the photomask blank (reflection reduction layer). The cross-sectional shape of the mask pattern when forming the photomask can be made vertical. Moreover, since the reflection reducing layer 3 is formed of a dense film, the occurrence of film defects can be suppressed and high chemical resistance can be provided.

<Embodiment 2>
In the second embodiment, a manufacturing method of 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 a cleaning solution containing sulfuric acid or an ozone cleaning solution is performed. In particular, as cleaning before resist coating, ozone cleaning may be performed using an ozone cleaning liquid. Ozone cleaning removes foreign matter and contamination on the resist coating surface. This ozone cleaning is effective for removing foreign matters and contamination on the resist-coated surface. However, in the course of the applicant's examination leading to the present invention, when a resist containing no surfactant is used, It has been obtained as a finding that the adhesiveness is deteriorated and the resist coating performance may be deteriorated. Thereby, in the case of a conventional photomask blank, the adhesiveness with a resist (resist that does not contain a surfactant) is insufficient, and the cross-sectional shape of the pattern may be tapered. According to the photomask blank, such a problem is suppressed.
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, so for photomask blanks for manufacturing large display devices, the amount of cleaning liquid consumed and the size of the cleaning device can be used for single wafer processing. A cleaning method, particularly a 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 ozone is spread over the entire surface of the upper layer portion 32 of the photomask blank 100 by spreading by rotation. Add the cleaning solution. 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 in which the ozone cleaning liquid is deposited on the entire surface of the upper layer portion 32 of the photomask blank 100, and then dropping of the ozone cleaning liquid and rotation of the photomask blank are stopped. The flowing liquid spin cleaning method in which the cleaning liquid continues to flow while rotating the photomask blank 100 at a low speed is characterized by the fact that the ozone concentration hardly changes and has a mechanical cleaning effect by the flowing liquid. There is a feature that the consumption of the cleaning liquid is small. 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 pre-resist cleaning by ozone cleaning, a resist pattern forming process for forming a resist pattern 4a on the upper layer portion 32 of the photomask blank 100 is performed.
Specifically, in this resist pattern forming step, first, the resist film 4 is formed on the upper layer portion 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. 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. EB (Electron Beam) drawing using an electron beam may be used. Thereafter, the resist film 4 is developed with a predetermined developer to form a resist pattern 4a (FIG. 3C).

  Next, the mask pattern light shielding film is wet-etched using the resist pattern 4a as a mask to form a light shielding film pattern (light shielding layer pattern 2a and reflection reduction layer pattern 3a) (FIG. 3D). The light shielding film for the mask pattern is composed of the light shielding layer 2, the lower layer part 31, and the upper layer part 32. In order to reduce the number of processes, it is desirable to perform wet etching all at once. The reduction in the number of processes not only improves the throughput and simplifies the etching apparatus, but also advantageously improves the defect quality. In the photomask blank 100 manufactured in the first embodiment, all layers constituting the light shielding film for the mask pattern from the light shielding layer 2 to the upper layer portion 32 are made of a material containing chromium, and the surface In the film thickness direction from the side toward the transparent substrate 1, the composition of the constituent material is adjusted so that the etching rate is increased with respect to the chromium etching solution. The bottom of the pattern is less likely to be skirted, 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 including the light shielding layer pattern 2a, the lower layer pattern 31a, and the upper layer pattern 32a on the transparent substrate 1 is manufactured.

  In the manufacturing method of the photomask 200, the resist film 4 is directly formed on the upper layer portion 32. However, an etching mask may be formed on the upper layer portion 32, and the resist film 4 may be 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 light-shielding film including the light-shielding layer 2, the lower layer portion 31, and the upper layer portion 32 using the processed etching mask as a mask. Wet etching. 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. When the etching mask is a material that has high wet etching resistance and high adhesion to chromium oxide to prevent infiltration of the wet etching solution, this method is used to shield light in a vertical cross-sectional shape including the upper layer portion. A film pattern 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.

  Further, 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 transparent substrate 1 and the light shielding layer 2 and The functional film for controlling the transmittance is etched after the light shielding film pattern is formed by the above-described method. Further, when fine adjustment of the phase is necessary, the transparent 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 adhesion to the resist film, and the wet etching solution is prevented from entering the interface between the resist film and the reflection reducing layer 3. The cross-sectional shape of the (pattern) can be made vertical.
Moreover, the tolerance with respect to ozone cleaning which is cleaning before resist coating is high. 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 light shielding film 2 for the mask pattern has few film defects and few defects generated in the mask manufacturing process.

<Embodiment 3>
In the third embodiment, 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 200 obtained by the manufacturing method described in the second embodiment is applied to a substrate with a resist film in which a resist film is formed on the substrate of the display device. Is placed on the mask stage of the exposure apparatus in such an arrangement 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 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.

Example 1
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 also used in the description of the second embodiment.

As shown in FIG. 3A, the photomask blank 100 of Example 1 includes a transparent substrate 1, a light shielding layer 2 having a function of shielding exposure light mainly used for manufacturing a display device, and mask pattern drawing light. A reflection reduction layer 3 that reduces reflection is formed, and the light shielding layer 2 and the reflection reduction layer 3 are combined to form a light shielding film for a mask pattern. The light shielding layer 2 is made of a chromium compound containing chromium and nitrogen (CrON in this embodiment), and the reflection reducing layer 3 is made of two layers (upper layer portion 32 and lower layer portion 31) of chromium, oxygen and nitrogen. It consists of a compound (CrCON).
First, the manufacturing method of the photomask blank 100 and details of the film configuration will be described.

((Manufacture of photomask blank))
(((Transparent substrate)))
An 8092 size (about 800 mm × 920 mm) synthetic quartz glass substrate in which both the first main surface and the second main surface were polished was prepared as a transparent 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)))
Using a large in-line type sputtering apparatus 300 (FIG. 2) on the transparent substrate 1, a light shielding layer 2 made of a chromium compound (CrON in this embodiment 1) and two layers (upper layer 32, lower layer 31) of chromium. A light-shielding film for a mask pattern composed of the reflection reducing layer 3 made of a compound (CrCON in the present Example 1) was formed.

Next, a method for forming these films will be described.
First, an in-line type sputtering shown in FIG. 2 is applied to a tray 301 on which a transparent substrate 1 is mounted on a substrate holder (not shown) with the main surface of the transparent substrate 1 (the surface on which a light shielding film is formed) facing downward. It was loaded into the loading chamber LL of the apparatus 300. Here, sputter targets 331, 332, 333, and 334 made of chromium (Cr) are arranged in the first sputter chamber SP1 and the second sputter chamber SP2.

The shutter 311 is opened, the tray 301 on which the transparent substrate 1 is mounted is moved from the carry-in chamber LL to the first sputter chamber SP1, and from the gas inlet corresponding to the sputter target 331 and the gas inlet corresponding to the sputter target 332 A mixed gas of argon (Ar) gas, nitrogen (N ₂ ) gas, and oxygen (O ₂ ) gas is introduced, a sputtering power of 9 kW is applied to the sputtering target 332 (the sputtering target 331 is 0 kW), and reactive sputtering is performed. went. In the present embodiment, the gases described below are introduced simultaneously from the gas inlets corresponding to the sputtering targets 331 to 334, respectively.
The gas flow rates are 70 sccm for Ar, 15 sccm for N ₂ , and 3 sccm for O ₂ (both the gas inlet corresponding to the sputter target 331 and the gas inlet corresponding to the sputter target 332 have the same conditions). At this time, the tray 301 was moved in the first sputter chamber SP1 at a speed of 400 mm / min. By this step, a CrON film as the light shielding layer 2 was formed on the main surface of the transparent substrate 1 with a thickness of about 80 nm.

Next, the tray 301 passes through the buffer chamber BU and moves to the second sputtering chamber SP2.
Argon (Ar) gas, nitrogen (N ₂ ) gas, and carbon dioxide (CO ₂ ) gas are introduced from the gas inlet corresponding to the sputter target 333, and a sputtering power of 2.2 kW is applied to the sputter target 333, Reactive sputtering was performed. The gas flow rates are 60 sccm for argon gas, 25 sccm for nitrogen gas, and 17 sccm for carbon dioxide gas. At this time, the tray 301 was moved at a speed of 400 mm / min. By this reactive ion sputtering process, a CrCON film (lower layer 31) having a thickness of about 20 nm was formed on the CrON film having a thickness of about 80 nm as the light shielding layer 2.

Next, a mixed gas in which 12% methane (CH ₄ ) is mixed with argon (Ar) gas, nitrogen (N ₂ ) gas, and oxygen (O ₂ ) gas are introduced from the inlet corresponding to the sputtering target 334. Then, a sputtering power of 2.4 kW was applied to the sputtering target 334 to perform reactive sputtering. The gas flow rate is 60 sccm for a mixed gas of argon and methane, 32 sccm for nitrogen gas, and 12 sccm for oxygen gas. At this time, the tray 301 was moved at a speed of 400 mm / min. By this reactive ion sputtering process, a CrCON film (upper layer portion 32) having a thickness of about 20 nm was formed on a CrCON film (lower layer portion 31) having a thickness of about 20 nm.

Thereafter, the tray 301 is moved from the second sputter chamber SP2 to the carry-out chamber UL, the shutter 312 is closed, and after evacuation, the carry-out chamber UL is returned to the atmospheric pressure state, and the substrate holder is taken out from the sputtering apparatus 300. .
In this way, a photomask blank 100 was obtained in which a light-shielding film made of CrON (light-shielding layer), CrCON (lower layer part), and CrCON (upper-layer part) was formed on a 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 = 70 sccm, N ₂ = 15 sccm, Power = 0 kW, tray conveyance speed = 400 mm / min
Sputtering 2: Ar = 70 sccm, N ₂ = 15 sccm, Power = 9.0 kW, tray conveyance speed = 400 mm / min
Sputtering 3: Ar = 60 sccm, N ₂ = 25 sccm, CO ₂ = 17 sccm, Power = 2.2 kW, tray conveyance speed = 400 mm / min
Sputtering 4: Ar / CH4 (12%) = 60 sccm, N ₂ = 32 sccm, O ₂ = 12 sccm, Power = 2.4 kW, tray conveyance speed = 400 mm / min
In addition, the gas supply of sputter | spatters 1-3 is supplied from the river upper side with respect to the target. The gas supply of the sputter 4 was supplied from the downstream side to the target.

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.
As shown in the figure, the chromium content contained in the reflection reducing layer is less than the chromium content contained in the light shielding layer, and the oxygen content contained in the upper layer portion of the reflection reducing layer is lower layer. More than the oxygen content contained in the part. (The oxygen content contained in the reflection reducing layer is greater than the oxygen content contained in the light shielding layer, and the oxygen content contained in the upper layer portion of the reflection reducing layer is the oxygen content contained in the lower layer portion. More than.)
Further, on the surface side of the upper layer portion (excluding the outermost surface layer (from the surface to a depth of about 2 nm) where natural oxidation or other contamination occurs), a region A substantially free of carbon has a thickness of about 6.5 nm. In this region A, oxygen continuously increases toward the outermost surface, and conversely, nitrogen continuously decreases.
FIG. 5 is a graph showing the ratio of nitrogen and oxygen based on the XPS analysis results. As shown in the figure, the maximum value of the ratio of oxygen to nitrogen (O / N) in region A is 5 or more, and the minimum value is 2.8 or more.
“Substantially free of carbon” means below the carbon detection limit in XPS.
The amount of change in flatness before and after forming the light shielding film (light shielding layer 2 and reflection reducing layer 3) on the transparent substrate 1 was measured with a flatness measuring device to be 5 μm, and the film stress of the light shielding film was low. confirmed. This is because the light shielding layer is made of chromium nitride containing a small amount of oxygen and has tensile stress, and the reflection reducing layer is made of chromium compound having a higher oxygen content than the light shielding layer and compressive stress. This is considered to be due to the stress canceling effect.

((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 upper layer portion 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.
When the change in reflectance (wavelength 436 nm) before and after ozone cleaning was measured, it was 0.06%, and it was confirmed that the ozone cleaning resistance was extremely high.

  Next, as shown in FIG. 3B, a resist film 4 having a film thickness of 525 nm is formed on the upper layer portion 32 of the photomask blank 100 using a photoresist that does not contain a surfactant. did. 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 light shielding film composed of a total of three layers of a CrON layer (light shielding layer 2), a CrCON layer (lower layer portion 31), and a CrCON layer (upper layer portion 32) sequentially formed on the transparent substrate 1 is used with the resist pattern 4a as a mask. Then, patterning was integrally performed by wet etching to form a light shielding film pattern (FIG. 3D). Therefore, the light shielding film pattern is composed of the light shielding layer pattern 2a made of CrON, the lower layer pattern 31a made of CrCON, and the upper layer pattern 32a made of 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.

FIG. 6 is a photograph of the cross-sectional shape of the light-shielding film pattern with the resist pattern 4a remaining, taken using a scanning electron microscope, using a sample prepared in the same manner up to the above steps.
As shown in the figure, a light-shielding film pattern having a cross-sectional shape very close to the vertical was obtained.

  Thereafter, the resist pattern was peeled off (FIG. 3E), and a photomask 200 in which a light-shielding film pattern having a line & space pattern (L / S) of 2 μm was formed on the transparent substrate 1 was obtained.

The dimensional variation (CD variation / CD uniformity) 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 uniformity.
As a result, the CD uniformity was 0.078 μm. As will be described later in the comparative example, the CD uniformity of the comparative example was 0.15 μm, and the CD uniformity of 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 produced in Example 1 has a high mask pattern dimensional accuracy of 0.078 μm in terms of CD uniformity, a low reflectivity for the exposure light, and zero defects at the photomask blank stage. Since there are few defects, the transfer pattern of the resist pattern on the display device substrate is also highly accurate and has 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.

(Example 2)
In the photomask blank of Example 2, the light shielding layer 2 was made of chromium nitride (CrN) substantially free of oxygen, and the film thickness of the light shielding layer 2 and the reflection reducing layer 3 (lower layer portion 31 and upper layer portion 32). A photomask blank was produced in the same manner as in Example 1 except that the above was adjusted.
The light shielding layer 2 of Example ₂ is formed by sputtering power in which the gas flow rate of Example 1 is 70 sccm for Ar, 15 sccm for N ₂ , and the CrN film thickness of the light shielding layer 2 is about 80 nm. did.
Further, the upper layer portion and the lower layer portion of the reflection reducing layer 3 are formed at the same gas flow rate as in Example 1, with the CrCON film thickness of the CrCON film in the lower layer portion 31 being about 20 nm and the CrCON of the upper layer portion 32. The film was formed with a sputtering power at which the film thickness was about 20 nm.
When XPS analysis was performed on the obtained photomask blank, oxygen was not detected in the light shielding layer 2 and it was confirmed that the light mask layer 2 was composed of a chromium nitride chromium compound composed of chromium and nitrogen.
Next, the obtained photomask blank was evaluated for film stress and ozone cleaning resistance in the same manner as in Example 1.
When the flatness change amount before and after forming the light shielding film (the light shielding layer 2 and the reflection reducing layer 3) on the transparent substrate 1 was measured with a flatness measuring machine, it was 4 μm, and the film stress of the light shielding film was low. confirmed. This is due to the stress canceling effect due to the fact that the light shielding layer is made of chromium nitride and is a tensile stress, and the reflection reducing layer is a material made of chromium compound having a higher oxygen content than the light shielding layer and is a compressive stress. Think of things.
When the change in reflectance (wavelength 436 nm) before and after ozone cleaning was measured, it was 0.06% as in Example 1, and it was confirmed that the ozone cleaning resistance was extremely high.

(Example 3)
In the photomask blank of Example 3, a phase shift film (phase adjustment layer), which is a functional film for adjusting the transmittance and phase shift amount of exposure light, is formed between the transparent substrate 1 and the light shielding film for the mask pattern. This is a so-called phase shift mask blank. Note that the light shielding film for the mask pattern 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 transparent substrate 1 made of a synthetic quartz glass substrate having the same size as in Example 1 by using a large in-line type 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 333 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, tray conveyance speed = 400 mm / min
Sputtering 3: Ar = 50 sccm, N ₂ = 90 sccm, Power = 8.0 kW, tray conveyance speed = 400 mm / min
Under the film forming conditions described above, in sputtering 1, a first phase shift film made of a molybdenum silicide nitride film (MoSiN) having a thickness of 55 nm is formed on the transparent substrate 1, and in sputtering 3, molybdenum having a thickness of 55 nm is formed. A second phase shift film made of a silicide 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 transparent substrate 1.
With respect to the substrate on which the phase shift film was formed, the transmittance and the phase difference were measured with MPM-100 manufactured by Lasertec Corporation. 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 mask pattern light-shielding film (the light-shielding layer 2 and the reflection reducing layer 3) as that in Example 1 was formed on the phase-shifting film to produce a phase-shifting mask blank.

  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 were the same.

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 thickness of 525 nm was formed on the light-shielding film using a photoresist containing no surfactant. 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, this light shielding film 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 having a phase shift film pattern with a line and space pattern of 2 μm on the transparent substrate 1 and a light shielding film pattern formed on the center of the phase shift film pattern. .

  As a result of measuring and evaluating the dimensional uniformity (CD uniformity) of the phase shift film pattern of this phase shift mask in the same manner as in Example 1, the CD uniformity was 0.08 μm. This phase shift mask had a highly accurate phase shift film pattern with sufficiently small CD uniformity. Therefore, a high-definition display device having desired characteristics as in Example 1 could be manufactured with a high yield.

(Comparative example)
The film forming conditions of the comparative example are shown below.
Sputtering 1: Ar = 65 sccm, N ₂ = 15 sccm, Power = 1.5 kW, tray conveyance speed = 400 mm / min
Sputtering 2: Ar / CH ₄ (4.9%) = 31 sccm, Power = 8.5 kW, tray conveyance speed = 400 mm / min
Sputtering 3: Ar = 34.8 sccm, N ₂ = 32.2 sccm, CO ₂ = 4.5 sccm, Power = 1.74 kW, tray conveyance speed = 400 mm / min
Sputtering 4: Ar = 34.8 sccm, N ₂ = 32.2 sccm, CO ₂ = 4.5 sccm, Power = 1.74 kW, tray conveyance speed = 400 mm / min
In addition, all the gas supply of sputter | spatters 1-4 is supplied from the upper stream side with respect to the target.
The photomask blank thus obtained comprises a CrN light-shielding layer and a reflection reducing layer having a two-layer structure of an upper layer portion and a lower layer portion, both of which are CrCON, on a transparent substrate.

About the obtained photomask blank of the comparative example, the composition analysis of the depth direction by X-ray photoelectron spectroscopy (XPS) was performed. The result is shown in FIG.
As shown in the figure, the oxygen content contained in the reflection reducing layer is larger than the oxygen content contained in the light shielding layer, but the oxygen content contained in the upper layer portion in the reflection reducing layer is the same as that in the lower layer portion. It is almost the same level.
Moreover, the area | region which does not contain carbon substantially does not exist in the surface side of an upper layer part, and the content rate of nitrogen and oxygen is substantially flat.
Next, the obtained photomask blank was evaluated for film stress and ozone cleaning resistance in the same manner as in Example 1.
When the flatness change amount before and after forming the light shielding film (the light shielding layer 2 and the reflection reducing layer 3) on the transparent substrate 1 was measured with a flatness measuring machine, it was 7.5 μm. Moreover, it was 2.11% when the change of the reflectance (wavelength 436nm) before and behind ozone washing | cleaning was measured. Compared with Examples 1 and 2, film stress and ozone cleaning resistance deteriorated.

Using the photomask blank manufactured by the method of Comparative Example 1, a light-shielding film pattern is formed by the same method as in Example 1, and the cross-sectional shape of the light-shielding film pattern in a state where the resist pattern 4a remains is obtained by scanning electron FIG. 8 shows a picture taken using a microscope.
As shown in the figure, the cross-sectional shape was a tapered shape with a very long hem. This is because the wet etching solution entered the interface between the resist film and the reflection reducing layer due to the problem of adhesion between the resist (resist that does not contain a surfactant) and the reflection reducing layer. Possible cause.
The CD uniformity of the photomask manufactured by the same method as in Example 1 was 0.15 μm.

As is clear from the above, the basic film configuration is the same in the example and the comparative example (a light-shielding layer of CrON or CrN on the transparent substrate, and a two-layer structure of an upper layer portion and a lower layer portion, both of which are CrOCN). However, in the photomask blank of the comparative example, the cross-sectional shape of the photomask blank of the comparative example was a large tapered shape.
On the other hand, the photomask blank of the embodiment according to the present invention has the above-described configuration by the manufacturing method described above, so that the cross-sectional shape can be verticalized when the light-shielding film pattern is formed. .
Further, according to the photomask blank of the example, the reflection reducing layer 3 is formed in a two-layer structure of the upper layer portion 32 and the lower layer portion 31, and when the contents of oxygen and nitrogen are relatively compared, the lower layer portion 31 is rich in nitrogen and the upper layer 32 is rich in oxygen. As a result, tensile stress is generated in the lower layer portion 31 and compressive stress is generated in the upper layer portion 32 as the film stress, and the film stress is canceled out mutually. Therefore, the stress of the entire film can be reduced.

1. . . Transparent substrate . . Light shielding layer 2a. . . 2. Light shielding layer pattern . . Antireflection layer 31. . . Lower layer 32. . . Upper layer 3a. . . 3. Reflection reduction layer pattern . . Resist film 4a. . . Resist pattern 100. . . Photomask blank 200. . . Photomask 300. . . In-line sputtering equipment

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 compound containing chromium and nitrogen,
The reflection reduction layer is made of a chromium compound containing chromium, nitrogen, and oxygen,
The content of chromium contained in the reflection reducing layer is less than the content of chromium contained in the light shielding layer,
The reflection reduction layer is a laminated film in which a plurality of layers are laminated, and the oxygen content contained in the upper layer portion on the surface side of the reflection reduction layer is the oxygen content contained in the lower layer portion on the light shielding layer side of the reflection reduction layer. A region which is larger than the amount and substantially does not contain carbon on the surface side of the upper layer portion, and in the region, oxygen continuously increases toward the outermost surface, and the ratio of oxygen to nitrogen (O The maximum value of / N) is 5 or more.   2. The photomask blank according to claim 1, wherein the minimum value of the ratio of oxygen to nitrogen (O / N) is 2 or more.   The photomask blank according to claim 1, further comprising a transmittance adjusting layer that adjusts the transmittance between the transparent substrate and the light shielding layer.   The photomask blank according to claim 1, further comprising a phase adjusting layer for adjusting a phase difference between the transparent substrate and the light shielding layer.   The photomask blank according to claim 3, wherein the transmittance adjusting layer and the phase adjusting layer are made of a material having etching selectivity with respect to the light shielding layer.   6. The photomask blank according to claim 1, wherein a resist layer is formed on the reflection reducing layer.   The photomask blank according to claim 6, wherein the resist layer is coated with a resist containing no surfactant. It is a manufacturing method of the photomask blank according to any one of claims 1 to 7,
Preparing the transparent substrate, forming the light shielding layer on the main surface of the transparent substrate, and forming the reflection reducing layer on the light shielding layer,
Forming a lower layer portion of the reflection reducing layer by sputtering using a chromium target in a mixed gas atmosphere containing carbon dioxide gas and nitrogen-based gas;
Forming an upper layer portion of the reflection reducing layer by sputtering using a chromium target in a mixed gas atmosphere containing an oxygen-based gas and a nitrogen-based gas;
A method for producing a photomask blank, comprising: Using the photomask blank according to any one of claims 1 to 5 or the photomask blank produced by the production method according to claim 8, and forming a resist layer on the photomask blank; ,
Drawing a desired pattern on the resist layer;
Performing development to form a resist pattern on the photomask blank; and
Patterning the light shielding layer and the reflection reducing layer by etching based on the resist pattern;
A photomask manufacturing method comprising manufacturing a photomask. Using the photomask blank according to claim 6 or 7,
Drawing a desired pattern on the resist layer;
Performing development to form a resist pattern on the photomask blank; and
Patterning the light shielding layer and the reflection reducing layer by etching based on the resist pattern;
A photomask manufacturing method comprising manufacturing a photomask.   The method for producing a photomask according to claim 9 or 10, wherein the resist layer is coated with a resist not containing a surfactant.   A photomask manufactured by the photomask manufacturing method according to claim 9 is placed on a mask stage of an exposure apparatus, and a transfer pattern formed on the photomask is placed on a display device substrate. A display device manufacturing method comprising an exposure step of exposing and transferring to a formed resist.