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 福上典仁 古沟透 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)、和在反射层(2)上形成的光吸收层(4)。光吸收层(4)包含氧(O)相对于锡(Sn)的原子数比(O/Sn)超过1.50且为2.0以下、并且膜厚为25nm以上45nm以下的氧化锡膜。由此,抑制或减轻以远紫外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,同时提高光吸收层的耐清洗性。(A reflective photomask blank (10) according to a first embodiment is provided with: the light-absorbing layer comprises a substrate (1), a reflecting layer (2) formed on the substrate (1), and a light-absorbing layer (4) formed on the reflecting layer (2). The light absorbing layer (4) contains a tin oxide film having an atomic ratio (O/Sn) of oxygen (O) to tin (Sn) of more than 1.50 and not more than 2.0 and having a film thickness of 25nm to 45 nm. Thus, the projection effect of a reflective photomask for pattern transfer using far ultraviolet as a light source is suppressed or reduced, the transfer performance to a semiconductor substrate is improved, and the cleaning resistance of a light absorbing layer is improved.)

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

a light absorbing layer formed on the reflective layer,

the light absorbing layer contains a tin oxide film having an atomic ratio (O/Sn) of oxygen (O) to tin (Sn) of more than 1.50 and not more than 2.0 and a film thickness of 25nm to 45 nm.

2. The reflective photomask blank according to claim 1, wherein the tin oxide film has a film thickness of 32nm to 45 nm.

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. Reflective photomask blank according to any of claims 1 to 3, wherein there is a capping layer formed between the light absorbing layer and the reflective layer.

5. 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 reflective layer and having a pattern,

the light absorption pattern layer includes a tin oxide film having an atomic ratio (O/Sn) of oxygen (O) to tin (Sn) of more than 1.50 and 2.0 or less and a film thickness of 25nm to 45 nm.

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.

Further, for future mass production of EUV mask blanks and EUV masks, it is also required to improve the cleaning resistance of the light absorbing layer.

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 improve the cleaning resistance of a light absorbing layer.

[ 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 light-absorbing layer includes a substrate, a reflective layer formed on the substrate, and a light-absorbing layer formed on the reflective layer. The light-absorbing layer contains a tin oxide film having an atomic ratio (O/Sn) of oxygen (O) to tin (Sn) of more than 1.50 and not more than 2.0 and a film thickness of 25nm to 45 nm.

A second aspect of the present invention is a reflective photomask, comprising: the light absorbing pattern layer includes a tin oxide film having an atomic ratio (O/Sn) of oxygen (O) to tin (Sn) of more than 1.50 and 2.0 or less and a film thickness of 25nm to 45 nm.

[ 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 cleaning resistance of the light absorbing layer is improved.

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 graph showing the relationship between the film thickness of the light-absorbing layer obtained as a result of the calculation and NILS (average value 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. 11 is a cross-sectional view showing a reflective photomask blank of an example.

FIG. 12 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. 13 is a sectional view showing a step subsequent to that of FIG. 12 in a method for manufacturing a reflective photomask using the reflective photomask blank of the example.

FIG. 14 is a sectional view showing a reflective photomask obtained in example.

Detailed Description