JPS6278557A - Photomask - Google Patents

Abstract

PURPOSE:To make dry etching easy, to improve adhesiveness to a transparent substrate and to decrease the reflectivity of a mask by constituting a photomask material of the transparent substrate and carbonized metal formed on the transparent substrate. CONSTITUTION:A transition metallic film 3 consisting of carbonized molybdenum, tungsten, tantalum, etc., is formed to about 1,000Angstrom film thickness on the transparent glass substrate 1 consisting of quartz, etc. The carbonized film 3 can be easily formed by a sputtering method, etc. The reflectivity decreases as compared to the case in which an ordinary metallic silicide film is used as a mask material if the carbonizd metallic film is used as the mask material and therefore, the decrease in the resolution of the pattern by multiple reflections can be averted. The carbonized metal has the good adhesiveness to the transparent substrate, particularly to a quartz glass substrate and extends the life as a photomask. The etching of the film 3 is easily executed by a dry etching method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photomask used for manufacturing semiconductor devices.

[Conventional technology] In the early days, masks used in the manufacture of semiconductor devices used photographic emulsion plates with glass substrates, but with the advancement of higher integration and miniaturization, transparent glass substrates are now used. Hard masks on which a thin film of metal such as chromium (Cr) is formed are widely used (for example, Japanese Patent Application Laid-Open No.
1572478, Japanese Unexamined Patent Publication No. 157249/1983).

FIG. 2 is a cross-sectional view of a conventional photomask material. In the figure, a metal film 2 made of chromium or the like is formed on a transparent glass substrate 1 made of quartz or the like. The metal film 2, such as Or, is formed on the transparent glass substrate 1 by vapor deposition or sputtering to a thickness of about 600 to 800 Å. The semiconductor phase photomask is made by applying a photoresist or an electron beam (hereinafter referred to as EB) resist on the metal film 2,
After drawing a pattern with light or gB, it is created through processes such as development and etching. When the metal film 2 is made of Cr, etching is performed using sericum antimony nitrate and perchloric acid in the Quent method, and carbon tetrachloride (etching is performed in the dry method).
A mixed gas of CC14) and oxygen (02) is used. In the production of masks for semiconductor devices, particularly devices with high integration and fine patterns such as VLSI, dry etching is advantageous because it has less side etching effect.

[Problem that the invention seeks to solve]

Couette etching is commonly used to manufacture Cr masks used in conventional masks for manufacturing semiconductor devices, but due to side etching effects, high-precision masks can only be manufactured using internal etching. was less than about 1i) OA/min, and the selectivity with the resist was also poor, making it unsuitable for mass production of photomasks. Further, in the case of Cr, there was a problem that the adhesion to the quartz substrate was poor, and the fine pattern was peeled off during mask cleaning.

As a means to solve the above problems, molybdenum (MO)
One possible method is to use a metal silicide film obtained by siliciding transition metals such as tantalum (1"a) + tungsten (W) as a mask material (for example, Special Issue No. 1983-61372). In other words, silica glass base material The silicon (Sl) inside and the 81 in the metal silicide as the mask material combine effectively to obtain a strong adhesive.In addition, etching is performed using a mixture of carbon tetrafluoride (CF4) and oxygen (02). Chromium (Or) by gas plasma
Dry etching is easier compared to (~1000
'A/min etching rate).

However, 1. The above-mentioned transition metal silicide film has a high reflectance of around 50% for light, and during wafer pattern transfer, the resolution of the pattern is reduced due to multiple scattering of light between the wafer and the mask, resulting in a submicron pattern. This will put pressure on the manufacturing of ultra-LSI devices that will be developed in the near future.

This invention was made in order to eliminate the drawbacks of the conventional ones as mentioned above, and it is easy to dry-etch, has excellent adhesion of transparent base & 7, and has low reflectance of the mask. The purpose is to provide high quality photomask materials.

[Means for solving the problem] The photomask material according to this starting point J is transparent 1 whole plate,
It is composed of carbide metal formed on this transparent substrate.

[Effect]

In this invention, the carbonized transition metal film not only has low reflection characteristics and high resolution, but also can be easily dry etched and has good adhesion to transparent substrates. , the fine pattern is difficult to peel off when cleaning the mask.

〔Example〕

FIG. 1 is a sectional view of a photomask material that is an embodiment of the present invention. In the figure, a transition metal film 3 such as carbide molybdenum (MO), tungsten (wL), and tantalum (Ta) is formed on a transparent glass substrate 1 made of quartz or the like to a thickness of about 1000λ. Carbonized transition metal film (hereinafter referred to as metal carbide film)
3 can be easily formed by sputtering or the like. For example, when molybdenum (Mo) is used as a target and sputtered with a plasma containing a mixture of argon (Ar) and -carbon oxide (CO) gas at an arbitrary ratio, a molybdenum carbide film (MoCx) is formed, in which Mo and C are combined at an appropriate ratio. ) can be formed. Alternatively, a molybdenum carbide target prepared in advance at an appropriate ratio may be sputtered using Ar plasma.

The larger the value of X of MoCx, the lower the reflectance, but it gradually becomes more insulating. When manufacturing masks using electron beams (FB), there is the problem of charge-up, which increases the
It is necessary to control X so that for example,
When X is 0.1 or more F, the reflectance is 30% or more,
The resistance also becomes approximately Ω, which is preferable. Furthermore, since the reflection of light is particularly large at the layer surface, C may be controlled so that the concentration of hx increases as it approaches the surface.

As mentioned above, when a metal carbide film is used as a mask material, the reflectance is lower than when a normal metal silicide film is used as a mask material, so it is necessary to avoid deterioration of pattern resolution due to multiple reflections. I can do it. In addition, carbonized metal has good adhesion on transparent substrates (such as STO2. A/203), especially quartz glass substrates, and has a longer life as a photomask (no peeling of fine patterns due to mask cleaning). There are advantages.

Further, the etching of the metal carbide film 3 can be easily performed by dry etching. For example, in the case of molybdenum carbide, CF4+02 (2%) or fc P'
Using iCC/4+02 mixed gas, 0.2 Torr
Under the condition of vacuum degree of 300W, approximately 500X/mi
Etching is completed at a processing speed of n. At this time, molybdenum carbide film (MoCx)ldMo0Ct
It forms with reaction products such as a and CO2 and evaporates. It can be seen that this etching speed is about five times as high as the conventional dry etching speed for Cr, making it suitable for mass production of photomasks. Note that before performing dry etching, a 7-photoresist or EB resist is applied to a film thickness of 4000 to 6000^ on the carbonized metal film 3, and then a pattern is drawn on the transparent glass substrate 1 using light or EB. As described above, since the metal carbide silicide film 3 has a conductivity of &Omega, the problem of charge-up does not occur even in the case of EB writing.

[Effects of the Invention] As described above, according to the present invention, since a carbonized transition metal film is formed on a transparent substrate, high-resolution pattern formation is possible at 0J, dry etching is easy, and etching speed is increased. , and a highly reliable photomask can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a photomask that is an embodiment of the present invention. FIG. 2 is a cross-sectional view of a conventional photomask. In the figure, 1 is a transparent glass substrate, 2 is a metal film, and 3 is a metal carbide film. Note that the same reference numerals in each figure indicate corresponding parts.

Claims (3)

[Claims] (1) A photomask used in the manufacture of semiconductor devices, which includes a transparent substrate and a metal carbide film formed on the transparent substrate. (2) The transparent substrate is quartz glass.Claim 1
Photomask as described in section. (3) The photomask according to claim 1, wherein the transparent substrate is sapphire.