JPS5819476A - Dry etching method for chromium film - Google Patents

Abstract

PURPOSE:To perform etching with superior dimensional accuracy by carrying out etching for forming a desired pattern on a mask plate using a chromium film by dry etching using a gaseous mixture of a gas contg. halogen with gaseous CO. CONSTITUTION:A mask plate using a single-layer or multilayer film of chromium or chromium oxide as a photomask material in the manufacture of a semiconductor device is etched to form a desired pattern. At this time, by dry etching such as gas plasma etching or reactive ion etching using a gaseous mixture of a gas contg. halogen, especially Cl such as CCl4 or chloroform with gaseous CO, the mask plate using the chromium film is etched. A chromium film pattern with high dimensional accuracy is easily obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel dry etching method for PM-based films.

A mask plate, which is a photomask material used in the manufacturing process of semiconductor devices, is a thin film layer made of a light-shielding substance such as chromium, iron, silicon, or oxides thereof, formed on a glass substrate in a single layer or multiple layers. It is made up of. As the light-shielding substance, chromium-based materials are generally used because of their excellent adhesion to glass, which is a transparent substrate, their excellent light-shielding properties, and their ability to form fine patterns. Note that in the present invention, the chromium-based film refers to a single layer or multilayer film of chromium or its oxide.

By the way, in order to form a desired pattern on a mask plate using a chromium-based film (hereinafter referred to as a chrome plate), etching of a chromium-based film is performed using 27thium ammonium nitrate [0e(NH4)3(N03)]. Wet chemical etching using chemicals such as a mixed solution of 6] and perchloric acid (HOJO) is applied.

However, wet chemical etching has many drawbacks such as difficulty in forming fine patterns, difficulty in controlling dimensions, high defect density, and complicated waste liquid processing.Recently, gas plasma etching or reactive ion etching has been Dry etching techniques such as etching have been developed and put into practical use. Reactive ion etching is a method in which gas plasma is generated between parallel plate electrodes and etching is performed in situ.

Conventionally, in these dry etching methods, a mixed gas containing at least a chlorine gas such as carbon tetrachloride and oxygen gas is heated by glow discharge. The reaction thought to be ↑ removes the PM by etching. As is clear from the above chemical reaction equation, the presence of oxygen atoms is essential for dry etching a chromium-based film.

In etching, oxygen gas plasma decomposes the photosensitive resin film that is the etching-resistant mask material for the chromium-based film. Therefore, by increasing the oxygen gas partial pressure in the mixed gas, the etch rate of the chromium-based film can be increased, but at the same time, the decomposition speed of the photosensitive resin film also increases. Therefore, if the oxygen partial pressure is increased to increase the etch rate of the chromium-based film to a practical level, the decomposition of the resist will also be accelerated, resulting in larger dimensional variations within the mask surface, making dimensional control extremely difficult. This is causing various problems such as.

Furthermore, recently, electron beam exposure technology has been developed as a high-precision exposure technology to replace photoresist technology, but the dry etching resistance of resists for electron beam exposure is even worse than that of photosensitive resists. Therefore, if a resist for electron beam exposure is used as an etching mask material and a mixed gas plasma containing chlorine-based gas and oxygen gas is used, there is a problem that dry etching is basically impossible because the resist film is greatly reduced. There is.

An example of this is shown in FIG. Figure 1 shows a mixed gas containing carbon tetrachloride as an etchant gas (0074+0+H
The etch rate of the chromium-based film in step 1 and the etch rate of the photosensitive resin film after plasma etching using 0IC
BR-100 (manufactured by Tokyo Ohka Kogyo ■).

The inventors of the present invention have conducted extensive research to overcome the drawbacks of ridges, and as a result, we have developed a material to be etched, which has a photosensitive resin film having a predetermined number of turns on a chromium-based film. When performing dry etching using a mixed gas plasma containing carbon gas and carbon monoxide, it is possible to suppress the loss of the photosensitive resin film, which is a masking material for etching, and at the same time to change the etch rate of the high retchromium film. It was discovered that seven turns of a PM-based film with extremely high dimensional accuracy could be changed, and the present invention was completed.

As the nitrogen-based gases used in the present invention,
Chlorine gases such as carbon tetrachloride and chloroform are preferred.

Next, the dry etching method of the present invention will be explained with reference to Examples.

Example 1 Dist O
Plasma etching was performed on the sample formed by the IB 100 with a desired seven-layer pattern using a mixed gas plasma consisting of carbon tetrachloride, carbon monoxide, and helium as an etchant gas.

A plasma etching device having a cylindrical electrode was used as the etching device. Also, the etching condition is 1!1.56
High frequency power of MHz, 200 W was applied, and the gas pressure was 0.2 Torr. A mixed gas was obtained by pulling carbon tetrachloride with a carrier gas (oo-1-as).

Here, the composition ratio of the carrier gas, i.e., the composition ratio of carbon oxide and helium, is used as a noza parameter to determine the etch rate of the chromium film and the mask-resistant material 01BR-100.
FIG. 2 is a graph showing the etch rate.

Here, in FIGS. 1 and 2, the composition ratio of the carrier gas is a value indicated by X 100 (X) 020Hs in FIG. 1, and in FIG. . +i X
It is a value expressed as 100 (%).

As is clear from FIG. 2, as the amount of carbon monoxide in the carrier gas increases, the etch rate of the PM film increases rapidly. On the other hand, although there is some variation in the etch rate of 0IBR-100, it is suppressed to a level that is of no practical use.

For example, as shown in FIG. 1, the etch rate of a chromium film with distance d using a mixed gas of oxygen gas and helium as a carrier gas is 50X, that is, 02. :He-75X/min at 1:1,
The etch rate of 0ICBR-100 is 160 minutes.

On the other hand, when a mixed gas of carbon monoxide and helium is used as the carrier gas as shown in Fig. 2, when the composition ratio of the carrier gas is 50%, that is, 00; The etch rate of the film is changed, and the etch rate of 0KBR-100 at this time is 50 L/min, which is about 1/3 of that when oxygen gas and helium are used. In this way, by adding carbon oxide, the etch rate of the four-layer film can be changed to a large extent, but the decomposition of the photosensitive resin film is suppressed.

This phenomenon does not occur at all in the conventional dry etching technique in which oxygen gas is added. Therefore, dry etching technology using a mixed gas plasma made by adding carbon monomer to a herogen-based gas, especially a chlorine-based gas, has made it possible to manufacture highly accurate chromium-based masks, and it has also become possible to produce electron beam resists, which had previously been considered difficult. Dry etching of chrome-based masks is now possible.

Furthermore, in the above embodiment, a gas plasma etching apparatus having a cylindrical electrode was used as the dry etching apparatus, but a reactive ion etching apparatus having a parallel plate type electrode was used.
It can also be applied to R,E,E,) devices. Note that although helium was mixed with carbon monoxide as a carrier gas, other inert gases such as argon and nitrogen may also be effective instead of helium, and of course, the same effect can be obtained by using carbon oxide alone.

Furthermore, in the above example, a plate consisting of a single layer of chromium film was used as the etching sample, but the same effect can be obtained by using a so-called low-reflection chrome plate, which is a two-layered chromium film and chromium oxide film formed on a glass substrate. It was confirmed that this effect was effective.

[Brief Description of the Drawings] Fig. 1 is a graph showing the etch rate of a chromium film and a photosensitive resin film according to the conventional method, and Fig. 2 is a graph showing the etch rate of a chromium film and a photosensitive resin film in an embodiment of the present invention. This is a graph showing. 21 figures 2 figures

Claims (1)

[Scope of Claims] (1) The material to be etched, which has a photosensitive resin film having a predetermined butterfly formed on a chromium-based film, is etched using a mixed gas plasma containing at least a heat-generating gas and m-carbon! 1. A method for dry etching a chromium-based film, characterized in that dry etching is performed using a chromium-based film to form a pattern of the chromium-based film corresponding to the pattern. (8) The dry etching method according to claim (2), wherein the chlorine-based gas is carbon tetrachloride or chloroform. (4) The dry etching method according to claim (1) or (2), wherein the dry etching is gas plasma etching or reactive ion etching.