阅读说明：本技术 反射型光掩模坯以及反射型光掩模 (Reflective photomask blank and reflective photomask ) 是由 古沟透 福上典仁 于 2018-06-29 设计创作，主要内容包括：第一实施方式的反射型光掩模坯(10)具备：基板(1),在基板(1)上形成的反射层(2),以及在反射层(2)上形成的、包含膜厚为17nm以上且小于25.0nm的氧化锡膜的光吸收层(4)。由此,抑制或减轻以远紫外线为光源的图案转印用的反射型光掩模的投影效应,提高对半导体基板的转印性能,并且同时抑制因清洗而产生的图案倒塌。(A reflective photomask blank (10) according to a first embodiment is provided with: the liquid crystal display device includes a substrate (1), a reflective layer (2) formed on the substrate (1), and a light absorption layer (4) formed on the reflective layer (2) and including a tin oxide film having a thickness of 17nm or more and less than 25.0 nm. Thus, the projection effect of a reflective photomask for pattern transfer using far ultraviolet rays as a light source is suppressed or reduced, the transfer performance to a semiconductor substrate is improved, and pattern collapse due to cleaning is suppressed.)

1. A reflective photomask blank for manufacturing a reflective photomask for pattern transfer using far ultraviolet rays as a light source, comprising:

a substrate, a first electrode and a second electrode,

a reflective layer formed of a multilayer film on the substrate, and

and a light absorption layer formed on the reflection layer and including a tin oxide film having a film thickness of 17nm or more and less than 25.0 nm.

2. The reflective photomask blank according to claim 1, wherein an atomic ratio (O/Sn) of oxygen to tin is 1.0 or more and 2.0 or less with respect to tin (Sn) and oxygen (O) contained in the tin oxide film.

3. The reflective photomask blank according to claim 1 or 2, wherein the material for forming the tin oxide film contains 80 atomic% or more of tin (Sn) and oxygen (O) in total.

4. The reflective photomask blank according to any one of claims 1 to 3, wherein when the intensity of reflected light from the reflective layer is Rm and the intensity of reflected light from the light-absorbing layer is Ra, the OD value (optical Density) specified in the following expression (1) is 1 or more,

OD＝-log(Ra/Rm)…(1)。

5. reflective photomask blank according to any of claims 1 to 4, wherein there is a capping layer formed between the light absorbing layer and the reflective layer.

6. A reflective photomask, comprising:

a substrate, a first electrode and a second electrode,

a reflective layer formed on the substrate, and

a light absorption pattern layer formed on the reflection layer, including a tin oxide film having a film thickness of 17nm or more and less than 25.0nm, and having a pattern.

Technical Field

The present invention relates to a reflective photomask used for lithography using far ultraviolet light as a light source and a reflective photomask blank used for manufacturing the same.

Background

In the manufacturing process of semiconductor devices, demands for miniaturization of photolithography techniques have been increased along with the miniaturization of semiconductor devices. The minimum resolution size of a transferred pattern in lithography has a large relationship with the wavelength of an exposure light source, and the shorter the wavelength, the smaller the minimum resolution size. Therefore, in order to further miniaturize the transfer pattern, the exposure light source has been replaced with EUV (Extreme Ultra Violet: Extreme ultraviolet) having a wavelength of 13.5nm from the conventional ArF excimer laser (wavelength of 193 nm).

EUV can be absorbed by most substances in high proportions. Therefore, in EUV lithography, a refractive optical system using light transmission cannot be used, and a transmission type photomask cannot be used. For this reason, a reflective photomask is used as the EUV exposure photomask (EUV mask).

Patent document 1 discloses an EUV photomask obtained by: a light-reflecting layer composed of a multilayer film in which molybdenum (Mo) layers and silicon (Si) layers are alternately laminated is formed on a glass substrate, a light-absorbing layer containing tantalum (Ta) as a main component is formed thereon, and a pattern is formed on the light-absorbing layer.

In addition, as a member constituting an optical system of the exposure apparatus, a reflection member such as a mirror is used instead of a lens or a transmission type beam splitter. Therefore, a design in which incident light to the EUV mask and reflected light from the EUV mask are coaxially arranged cannot be obtained. Therefore, in EUV lithography, EUV is generally incident with the optical axis tilted by 6 degrees with respect to the direction perpendicular to the EUV mask plane, and reflected light with the optical axis tilted by 6 degrees is directed to the semiconductor substrate on the side opposite to the incident light.

Disclosure of Invention

[ problems to be solved by the invention ]

In EUV lithography, the optical axis is inclined, and thus the incident light to the EUV mask causes a shadow of the mask pattern (patterned light-absorbing layer) of the EUV mask. The problem that occurs with the creation of this shadow is known as the projection effect. This projection effect is a principle problem of EUV lithography with an inclined optical axis.

In the conventional EUV mask blank, a film containing tantalum (Ta) as a main component and having a film thickness of 60 to 90nm is used as a light absorbing layer. In an EUV mask manufactured using this mask blank, there is a possibility that a contrast is lowered at an edge portion which becomes a shadow of a mask pattern depending on a relationship between an incident direction and a mask pattern direction at the time of exposure for pattern transfer. Accordingly, there is a problem that line edge roughness of a transfer pattern on a semiconductor substrate increases and a line width cannot be formed to a desired size, and transfer performance may deteriorate.

In addition, the conventional EUV mask has a problem of pattern collapse (パターン - れ) due to cleaning during production.

The invention aims to suppress or reduce the projection effect of a reflective photomask for pattern transfer using far ultraviolet rays as a light source, improve the transfer performance to a semiconductor substrate, and suppress pattern collapse due to cleaning.

[ means for solving problems ]

In order to solve the above problem, a first aspect of the present invention is a reflective photomask blank for manufacturing a reflective photomask blank for pattern transfer using deep ultraviolet rays as a light source, comprising: the optical film includes a substrate, a reflective layer formed on the substrate, and an optical absorption layer formed on the reflective layer and including a tin oxide film having a film thickness of 17nm or more and less than 25.0 nm.

A second aspect of the present invention is a reflective photomask, comprising: the light-absorbing film includes a substrate, a reflective layer formed on the substrate, and a light-absorbing pattern layer formed on the reflective layer and including a tin oxide film having a film thickness of 17nm or more and less than 25.0nm and having a pattern formed thereon.

[ Effect of the invention ]

According to the present invention, it is expected that the projection effect of the pattern transfer reflective photomask using far ultraviolet rays as a light source is suppressed or reduced, the transfer performance to the semiconductor substrate is improved, and the pattern collapse due to cleaning is suppressed.

Drawings

FIG. 1 is a cross-sectional view showing a reflective photomask blank according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a reflective photomask showing an embodiment of the present invention.

FIG. 3 is a graph showing optical constants of respective metal materials at an EUV wavelength.

FIG. 4 is a graph showing the relationship between the ratio of oxygen to tin (O/Sn) contained in a tin oxide film and the melting point.

Fig. 5 is a graph showing the relationship between the film thickness of the light-absorbing layer and the EUV reflectance obtained as a result of calculation when the light-absorbing layer is a tin oxide (SnOx) film or a tantalum (Ta) film.

Fig. 6 is a graph showing the relationship between the film thickness and the OD value of the light-absorbing layer obtained as a result of calculation when the light-absorbing layer is a tin oxide (SnOx) film or a tantalum (Ta) film.

FIG. 7 is a graph showing the relationship between the film thickness of the light-absorbing layer obtained as a result of calculation and the HV bias value of the pattern transferred using the photomask in the case where the light-absorbing layer is a tin oxide (SnOx) film or a tantalum (Ta) film.

Fig. 8 is a graph showing the calculation results of HV variation values when OD values were 1.0 and 2.0 in the case where the light absorbing layer was a tin oxide (SnOx) film and a tantalum (Ta) film.

Fig. 9 is a graph showing the relationship between the film thickness of the light absorbing layer obtained as a result of the calculation and NILS (values in the X direction and the Y direction) of the pattern transferred by the photomask in the case where the light absorbing layer is a tin oxide (SnOx) film or a tantalum (Ta) film.

FIG. 10 is a cross-sectional view showing a reflective photomask blank of an example.

FIG. 11 is a sectional view for explaining a step of a method for manufacturing a reflective photomask using the reflective photomask blank of the embodiment.

FIG. 12 is a sectional view showing a step subsequent to that of FIG. 11 in a method for manufacturing a reflective photomask using the reflective photomask blank of the example.

FIG. 13 is a sectional view showing a reflective photomask obtained in example.

Detailed Description