JPS597363A - Formation of mask - Google Patents

Abstract

PURPOSE:To enhance precision of a master pattern, and to reduce a number of defects of a mask, by exposing the surface of a thin metallic film formed on a glass substrate to an oxygen plasma atmosphere, and etching it using the resist pattern as the mask. CONSTITUTION:A thin metallic film 2 is formed on a glass substrate 1, and exposed to oxygen plasma for about 10min immediately before coating with a resist to remove foreign matters 3 on the film 2, such as organic matters. The film 2 is coated with the resist 4, patternwise exposed, and developed. After the development, an about 10nm thick insoluble resist layer 5 remains at the positions where the resist is dissolved. The layer 5 is formed on the surface of the layer 2 as a insoluble film during the development by the exposure of it to the oxygen plasma. It is removed by dry ashing again with oxygen plasma. Then, the layer 2 is etched using the resist 4 as a mask and the resist 4 is removed to complete a photomask.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a mask.0 In the photomask manufacturing process, the adhesiveness of the thin metal film 2 with the resist applied to the film, such as a chromium film or a chromium oxide/chromium film, is The quality is determined by the photomask pattern shape, accuracy, and mask defects (white defects, black defects).
This has a major impact on the situation of occurrence. Therefore, conventionally, for a metal surface formed on a glass substrate used for mask production, contamination layers and foreign substances between the metal surface and the resist coated thereon have been removed to improve the adhesion therebetween.

For this purpose, cleaning with organic solvents, acids, water, etc. has been carried out. Although cleaning with these solutions is effective in removing strong contamination and large foreign objects on metal surfaces, they do not essentially improve the adhesion between the metal surface and the resist, but rather they only strengthen the adhesion. In some cases, the adhesion strengthening agent was removed from the surface of the metal film, but in many cases, a sufficient effect could not be obtained.

The present invention cleans the surface of the metal thin film that causes such mask defects at the molecular layer level, and also improves the adhesion with the resist.
It is an object of the present invention to provide a mask forming method that improves mask pattern accuracy and reduces mask defects.

The present invention will be explained in detail below.

Chromium (C
r) Single layer film or chromium-chromium oxide (Cr-Crx
A two-layer film of Oy) is used. In the node mask manufacturing process using a Cr single-layer film, the present inventor has demonstrated that by exposing the mask plate before resist coating to oxygen plasma, the adhesion between the metal film and the resist coated thereon is strengthened. At the same time, it has been found that contaminant layers and foreign substances such as organic substances on the surface of the metal film are removed, and as a result, it is possible to manufacture a mask with high pattern accuracy and fewer defects.

This phenomenon of enhanced adhesion is interpreted to be due to the formation of an extremely thin Cr x Oy layer on the surface of the Cr film, which is active against the resist. In addition, the light-shielding film is Cr-Cr
In the case of a two-layer film of XOy, Cr is removed by oxygen plasma.
It is interpreted that an active oxidation state is uniformly generated on the surface of the X0Y film.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. A thin metal film 2 is formed on the glass substrate 1 without being separated, and this is heated with oxygen plasma (high frequency power 40
oW, 02 If force of 2 Torr) for 10 minutes, and through this treatment, foreign matter 3 such as organic matter on the resist is removed (FIG. 1). Thereafter, a resist 4 is applied (FIG. 2), and after exposure and drawing, development is performed by a normal method (FIG. 3). After development,
An insoluble resist layer 6 of 100 layers remains in the resist-dissolved area (FIG. 4). The thickness of this remaining layer 5 increases in proportion to the exposure time to oxygen plasma and the high frequency power. This resist residual layer 6 is formed on the metal surface as a film that is not melted during development by exposing the metal surface to oxygen plasma, and its presence strengthens the adhesion between the metal surface and the resist. It is also proof of that. That is, even if the adhesion between the metal surface and the resist is originally poor, the adhesion can be strengthened by treating the metal surface with this oxygen plasma.

This remaining layer 6 is removed again by light ashing using oxygen plasma (FIG. 5). Thereafter, the metal thin film 2 is etched using the resist 4 as a mask (sixth etching).
After that, the resist 4 is removed and the fumetomask is completed.

As explained above, the present invention not only removes foreign matter on the surface by treating the surface of a thin film of metal or metal oxide using oxygen plasma, but also strengthens the adhesion with the resist and then forms a pattern with the resist. Therefore, it is possible to provide a method for forming a mask with a fine dimension pattern with high accuracy and low defect density, and its effects are significant.

[Brief explanation of the drawing]

1 to 6 are process diagrams showing a method of forming a mask according to an embodiment of the present invention. 1...Glass substrate, 2...Metal thin film,
3... Foreign matter such as organic matter, 4... Resist, 6... Resist remaining layer. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 6

Claims (1)

[Claims] After exposing the surface of the metal film or metal oxide film formed on the glass substrate to an oxygen plasma atmosphere, a resist pattern is formed on the surface of the metal film or metal oxide film, and the resist pattern is used as a mask to expose the metal film or metal oxide film to an oxygen plasma atmosphere. A method for forming a mask, comprising forming a pattern of the metal film or metal oxide film by etching the metal oxide film.