阅读说明：本技术 光掩模坯料、光掩模的制造方法、及显示装置的制造方法 (Photomask blank, method for manufacturing photomask, and method for manufacturing display device ) 是由 田边胜 浅川敬司 安森顺一 于 2020-02-24 设计创作，主要内容包括：本发明提供光掩模坯料、光掩模的制造方法、及显示装置的制造方法,在以过度蚀刻时间对图案形成用薄膜进行湿法蚀刻而形成于透明基板上的转印图案中抑制在与透明基板的界面的浸入。光掩模坯料为用于形成光掩模的底版,光掩模为通过湿法蚀刻图案形成用薄膜而得到的、在透明基板上具有转印图案的光掩模,图案形成用薄膜含有过渡金属、硅、氧、氮,通过XPS分析得到的氧的含有率为1原子％以上且70原子％以下,且在将透明基板与图案形成用薄膜的界面定义为通过XPS分析得到的图案形成用薄膜中包含的过渡金属的含有率为0原子％的位置时,从界面起向上述图案形成用薄膜的表面30nm以内的区域中,氮相对于氧的比率存在最大值。(The invention provides a photomask blank, a method for manufacturing a photomask and a method for manufacturing a display device, which can inhibit the penetration of a transfer pattern formed on a transparent substrate by wet etching a thin film for pattern formation in an over-etching time. The photomask blank is a master for forming a photomask, the photomask having a transfer pattern on a transparent substrate obtained by wet etching a thin film for pattern formation, the thin film for pattern formation containing a transition metal, silicon, oxygen, and nitrogen, the oxygen content obtained by XPS analysis being 1 atomic% or more and 70 atomic% or less, and the ratio of nitrogen to oxygen being a maximum in a region within 30nm from the interface to the surface of the thin film for pattern formation when the interface between the transparent substrate and the thin film for pattern formation is defined as a position at which the content of the transition metal contained in the thin film for pattern formation obtained by XPS analysis is 0 atomic%.)

1. A photomask blank having a thin film for pattern formation on a transparent substrate,

the photomask blank is a master for forming a photomask having a transferred pattern on the transparent substrate obtained by wet etching the thin film for pattern formation,

the thin film for pattern formation contains a transition metal, silicon, oxygen, and nitrogen, the oxygen content obtained by XPS analysis is 1 atomic% or more and 70 atomic% or less, and when an interface between the transparent substrate and the thin film for pattern formation is defined as a position where the transition metal content contained in the thin film for pattern formation obtained by XPS analysis is 0 atomic%, a maximum value of a ratio of nitrogen to oxygen exists in a region within 30nm from the interface toward a surface of the thin film for pattern formation.

2. The photomask blank of claim 1,

the transition metal is molybdenum.

3. The photomask blank of claim 1 or 2,

the content of oxygen is 5 atomic% or more and 70 atomic% or less.

4. The photomask blank of claim 1 or 2,

the nitrogen content is 35 at% or more and 60 at% or less.

5. The photomask blank of claim 1 or 2,

the pattern-forming thin film has a columnar structure.

6. The photomask blank of claim 1 or 2,

the pattern forming film is a phase shift film having optical characteristics such that the transmittance thereof is 1% or more and 80% or less with respect to a typical wavelength of exposure light, and the phase difference thereof is 160 ° or more and 200 ° or less.

7. The photomask blank of claim 1 or 2,

the thin film for pattern formation is provided with an etching mask film having a different etching selectivity with respect to the thin film for pattern formation.

8. The photomask blank of claim 7,

the etching mask film is made of a material containing chromium and substantially not containing silicon.

9. A method for manufacturing a photomask, comprising the steps of,

comprising:

a step of preparing a photomask blank according to any one of claims 1 to 6;

and a step of forming a resist film on the thin film for pattern formation, and wet-etching the thin film for pattern formation using a resist film pattern formed of the resist film as a mask to form the transfer pattern on the transparent substrate.

10. A method for manufacturing a photomask, comprising the steps of,

comprising:

preparing the photomask blank according to claim 7 or 8;

forming a resist film on the etching mask film, and performing wet etching on the etching mask film using a resist film pattern formed of the resist film as a mask to form an etching mask film pattern on the thin film for pattern formation;

and a step of forming the transfer pattern on the transparent substrate by wet etching the thin film for pattern formation using the etching mask film pattern as a mask.

11. A method of manufacturing a display device, characterized in that,

the method for manufacturing a photomask according to claim 9 or 10, comprising an exposure step of placing the photomask on a mask stage of an exposure apparatus, and exposing and transferring the transfer pattern formed on the photomask to a resist film formed on a substrate of a display device.

Technical Field

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

Background

In recent years, with the increase in screen size and viewing angle, high definition and high-speed display have been rapidly developed in display devices such as fpds (flat Panel displays) represented by lcds (liquid Crystal displays). One of the elements required for the high definition and high speed display is the production of electronic circuit patterns such as fine and highly dimensionally accurate elements and wirings. Photolithography is often used for patterning electronic circuits for display devices. Therefore, a phase shift mask for manufacturing a display device, which forms a fine and highly accurate pattern, is required.

For example, patent document 1 discloses a blank mask for a flat panel display and a photomask using the same, in which a thin film containing molybdenum silicide is wet-etched with an etching solution obtained by diluting phosphoric acid, hydrogen peroxide, and ammonium fluoride in water in order to minimize damage to a transparent substrate during wet etching of the thin film containing molybdenum silicide.

In addition, patent document 2 discloses a phase-reversal blank mask and a photomask obtained in such a manner that a phase-reversal film 104 is composed of films having different compositions that can be etched in the same etching solution, and each of the films having different compositions is formed in the form of a multilayer film or a continuous film having at least 2 layers or more, which are laminated once or more, in order to improve the pattern accuracy.

Disclosure of Invention

Problems to be solved by the invention

In recent years, as a phase shift mask blank for manufacturing such a display device, it has been studied to use a phase shift film containing oxygen at a certain ratio or more (for example, 5 atomic% or more, or even 10 atomic% or more) as a phase shift film having optical characteristics such that the transmittance of the phase shift film with respect to exposure light is 10% or more, or even 20% or more, because a fine pattern of less than 2.0 μm can be reliably transferred.

Further, the size of the phase shift mask blank for manufacturing a display device is much larger than that of the phase shift mask blank for manufacturing a semiconductor device. In the case where the phase shift film of such a phase shift mask blank having a large size is patterned into a phase shift film, even if wet etching is performed at a time until the transparent substrate is exposed in the phase shift film pattern (just etching time), CD fluctuation of in-plane distribution greater than 100nm cannot be avoided. In order to make the CD fluctuation of the phase shift film pattern less than 100nm, it is required to perform wet etching for a time longer than just the etching time (over-etching time).

It is known that, when a phase shift film having such an oxygen content of not less than a predetermined value, for example, not less than 5 atomic% or even not less than 10 atomic% is patterned by wet etching with an excessive etching time, the wet etching solution enters the interface between the phase shift film and the transparent substrate, and etching of the interface portion proceeds relatively quickly. The cross-sectional shape of the edge portion of the phase shift film pattern formed is a shape in which so-called biting occurs due to the immersion of the wet etching solution.

In the case where a gnawing shape is generated in the sectional shape of the edge portion of the phase shift film pattern, the phase shift effect is weak. Therefore, the phase shift effect cannot be sufficiently exhibited, and a fine pattern of less than 2.0 μm cannot be stably transferred. When the content of oxygen in the phase shift film is set to be not less than a predetermined value, for example, not less than 5 atomic% or even not less than 10 atomic%, it is difficult to strictly control the cross-sectional shape of the edge portion of the phase shift film pattern, and it is very difficult to control the line width (CD).

In addition, in a binary mask blank including a light-shielding film containing a transition metal, silicon, oxygen, and nitrogen, the same problem occurs when a light-shielding pattern is formed in the light-shielding film by wet etching.

The present invention has been made to solve the above conventional problems, and an object thereof is to provide a photomask blank, a method for manufacturing a photomask, and a method for manufacturing a display device, in which the penetration of a thin film for pattern formation into an interface with a transparent substrate is suppressed in a transfer pattern formed on the transparent substrate by wet etching for an excessive etching time.

Means for solving the problems

In order to solve these problems, the present inventors have conducted intensive studies on a technique for suppressing the penetration of a transfer pattern formed on a transparent substrate at the interface with the transparent substrate by wet-etching a thin film for pattern formation for an over-etching time. The present inventors originally thought that the cause of the penetration into the interface with the transparent substrate in the thin film for pattern formation containing a transition metal, silicon, oxygen, and nitrogen may not be the absolute amount of oxygen in the thin film for pattern formation. However, even if the absolute amount of oxygen in the pattern forming thin film is about the same, there are cases where the film is immersed in the interface with the transparent substrate and cases where the film is not immersed in the interface with the transparent substrate. As a result of further studies, the present inventors have found that the ratio of nitrogen to oxygen in the composition region of the pattern forming thin film formed on the interface side with the transparent substrate is closely related to the penetration into the interface with the transparent substrate. Further, the present inventors have further studied and found that, when the content of oxygen in the pattern forming film obtained by XPS (X-ray Photoelectron Spectroscopy) analysis is 1 atomic% or more and 70 atomic% or less (particularly, the content of oxygen is 5 atomic% or more and 70 atomic% or less) and the interface is defined as a position where the content of the transition metal contained in the pattern forming film obtained by XPS analysis is 0 atomic%, if the structure is such that the ratio of nitrogen to oxygen has a maximum value in a region within 30nm from the interface toward the surface of the pattern forming film, the intrusion into the interface with the transparent substrate is suppressed even when the pattern is formed by wet etching the pattern forming film for an excessive etching time.

The present inventors presume a cause of suppressing the intrusion at the interface with the transparent substrate by the above-described structure as described below. When the pattern forming thin film is measured by XPS, a composition gradient region in which the composition of the thin film is inclined appears in a region of 30nm from the interface with the transparent substrate defined by XPS measurement as a measured characteristic. The transition metal and silicon in the pattern forming thin film are components derived from the target material, and the composition ratio thereof is substantially the same as the composition ratio of the target material. On the other hand, oxygen and nitrogen in the thin film for pattern formation are both components responsible for gas. Since there is a limit to the amount of gas taken into the pattern forming thin film, it is considered that the amount of oxygen decreases as the amount of nitrogen taken in increases. Further, oxygen is an element that accelerates the etching rate of wet etching, whereas nitrogen is an element that retards the etching rate of wet etching. Therefore, the ratio of nitrogen to oxygen (N/O) is very important in the characteristics of the thin film for pattern formation. It is presumed that if the film for pattern formation has a maximum value of the ratio (N/O) of nitrogen to oxygen in a region within 30nm from the interface with the transparent substrate defined by XPS measurement, the etching rate is appropriately lowered in the vicinity of the interface with the transparent substrate, and the occurrence of biting can be suppressed while suppressing the intrusion.

These assumptions are based on the assumptions found at the present stage, and do not limit the scope of the present invention at all.

The present invention has been made as a result of the above-described intensive studies, and has the following configuration.

(Structure 1)

A photomask blank having a thin film for pattern formation on a transparent substrate,

the photomask blank is a master for forming a photomask having a transferred pattern on the transparent substrate obtained by wet etching the thin film for pattern formation,

the thin film for pattern formation contains a transition metal, silicon, oxygen, and nitrogen, the oxygen content obtained by XPS analysis is 1 atomic% or more and 70 atomic% or less, and when an interface between the transparent substrate and the thin film for pattern formation is defined as a position where the transition metal content contained in the thin film for pattern formation obtained by XPS analysis is 0 atomic%, a maximum value of a ratio of nitrogen to oxygen exists in a region within 30nm from the interface toward a surface of the thin film for pattern formation.

(Structure 2)

The photomask blank according to structure 1, wherein the transition metal is molybdenum.

(Structure 3)

The photomask blank according to structure 1 or 2, wherein the content of oxygen is 5 atomic% or more and 70 atomic% or less.

(Structure 4)

The photomask blank according to any one of structures 1 to 3, characterized in that the nitrogen content is 35 at% or more and 60 at% or less.

(Structure 5)

The photomask blank according to any one of structures 1 to 4, wherein the pattern-forming thin film has a columnar structure.

(Structure 6)

The photomask blank according to any one of structures 1 to 5, wherein the pattern-forming film is a phase shift film having optical characteristics such that the transmittance is 1% or more and 80% or less with respect to the typical wavelength of the exposure light and the phase difference is 160 ° or more and 200 ° or less.

(Structure 7)

The photomask blank according to any one of structures 1 to 6, comprising an etching mask film having a different etching selectivity with respect to the pattern forming thin film on the pattern forming thin film.

(Structure 8)

The photomask blank according to structure 7, wherein the etching mask film is made of a material containing chromium and substantially no silicon.

(Structure 9)

A method for manufacturing a photomask, comprising the steps of,

comprising:

preparing a photomask blank according to any one of structures 1 to 6;

and a step of forming a resist film on the thin film for pattern formation, and wet-etching the thin film for pattern formation using a resist film pattern formed of the resist film as a mask to form the transfer pattern on the transparent substrate.

(Structure 10)

A method for manufacturing a photomask, comprising the steps of,

comprising:

a step of preparing a photomask blank according to structure 7 or 8;

forming a resist film on the etching mask film, and performing wet etching on the etching mask film using a resist film pattern formed of the resist film as a mask to form an etching mask film pattern on the thin film for pattern formation;

and a step of forming the transfer pattern on the transparent substrate by wet etching the thin film for pattern formation using the etching mask film pattern as a mask.

(Structure 11)

A method for manufacturing a display device, comprising an exposure step of placing a photomask obtained by the method for manufacturing a photomask according to claim 9 or 10 on a mask stage of an exposure apparatus, and exposing and transferring the transfer pattern formed on the photomask to a resist film formed on a substrate of a display device.

Effects of the invention

According to the photomask blank of the present invention, even if the thin film for patterning is wet-etched for an excessive etching time, the thin film for patterning can be patterned into a good cross-sectional shape in which the thin film for patterning is prevented from entering the interface with the transparent substrate. Further, it is possible to realize a photomask blank in which a thin film for pattern formation is patterned by wet etching into a cross-sectional shape having a small in-plane distribution of CD fluctuation.

In addition, according to the method for manufacturing a photomask of the present invention, a photomask is manufactured using the photomask blank. Therefore, a photomask having a good transfer pattern can be manufactured. In addition, a photomask having a transfer pattern with a small CD fluctuation of in-plane distribution can be manufactured. The photomask can be adapted to the miniaturization of the line-space pattern and the connection hole.

In addition, according to the method for manufacturing a display device of the present invention, a display device is manufactured using a photomask manufactured using the photomask blank or a photomask obtained by the method for manufacturing a photomask. Therefore, a display device having a fine line-space pattern and a connection hole can be manufactured.

Drawings

Fig. 1 is a schematic view showing a film structure of a phase shift mask blank according to embodiment 1.

Fig. 2 is a schematic view showing a film structure of a phase shift mask blank according to embodiment 2.

Fig. 3(a) to (e) are schematic diagrams showing steps of manufacturing the phase shift mask according to embodiment 3.

Fig. 4(a) to (c) are schematic diagrams showing steps of manufacturing the phase shift mask according to embodiment 4.

Fig. 5 is a view showing the results of composition analysis in the depth direction of the phase shift mask blank of example 1.

FIG. 6 is a photograph of a cross section of a phase shift mask of example 1.

FIG. 7 is a photograph of a cross section of a phase shift mask of example 2.

Fig. 8 is a view showing the results of composition analysis in the depth direction of the phase shift mask blank according to example 3.

FIG. 9 is a photograph of a cross section of a phase shift mask of example 3.

Fig. 10 is a cross-sectional photograph of the phase shift mask of comparative example 1.

Fig. 11 is a graph showing the distance from the substrate interface and the ratio of N/O by XPS with respect to the phase shift mask blanks of examples 1 and 2 and comparative example 1.

Fig. 12 is a graph showing the distance from the substrate interface and the ratio of N/O based on XPS with respect to the phase shift mask blank of example 3.

Description of the reference numerals

10 … phase shift mask blank (photomask blank)

20 … transparent substrate

30 … phase shift film (film for pattern formation)

30a … phase shift film Pattern (transfer Pattern)

40 … etching mask film

40a … first etch mask film pattern

40b … second etch mask film pattern

50 … first resist film Pattern

60 … second resist film Pattern

100 … phase shift mask (photomask)

Detailed Description

Hereinafter, embodiments of the present invention will be described. In each embodiment, a case where the photomask blank is a phase shift mask blank and the pattern forming thin film is a phase shift film is described, but the content of the present invention is not limited to this.