JPH01288853A - Dry etching method - Google Patents

Abstract

PURPOSE:To improve the etching resistance of a resist film by bringing the plasma of a gaseous fluorine system into contact with the resist film, thereby curing said film. CONSTITUTION:A Cr layer 2 of a desired thickness is formed on a glass substrate 1 and a resist for electron beam exposing is coated on the layer 2 and is then exposed and developed to form the resist film 3. This substrate is charged into a plasma treatment device and after the gaseous fluorine is introduced into the device, a desired power is supplied to the device to bring the plasma into contact with the film 3 by which the surface thereof is changed to the film 31 having the high etching resistance to the plasma of the gaseous mixture composed of CCl4 and O2. The gaseous mixture composed of the CCl4 and O2 is then introduced into the treatment device to etch the layer 2. The resist film is capable of maintaining the shape during dry etching and the accuracy of patterning is improved according to this method.

Description

[Detailed Description of the Invention] [Summary] Regarding the improvement of dry etching of metals such as light shielding materials of photomasks, we have developed a reactive ion etching method using a resist for electron beam exposure, a mixed gas of carbon tetrachloride and oxygen as a reactive gas, and The purpose is to provide a dry etching method that maintains accurate patterning, which is the inherent advantage of the combination of The metal layer partially covered by the resist mask for electron beam exposure is subjected to reactive ion etching using a mixed gas of carbon tetrachloride and oxygen as a reactive gas. The resist mask for electron beam exposure is brought into contact with a fluorine-based gas plasma to convert the surface of the resist mask for electron beam exposure into a hardened resist layer.

[Industrial application field]

The present invention relates to improvements in dry etching methods. In particular, it relates to improvements in dry etching of metals such as light shielding materials for photomasks.

[Conventional technology]

Metals such as chrome are generally used for the light shielding material of photomasks, and in order to accurately pattern metals such as chrome, a resist mask must be formed accurately using an electron beam exposure method, etc. It is appropriate to perform dry etching using this resist mask.

In this case, as a resist for electron beam exposure,
For example, EBR-9 (manufactured by Toshi Co., Ltd.) is used, and as a negative resist for electron beam exposure, for example, CNS
(manufactured by Toyo Soda Co., Ltd.), etc. are suitable. To carry out dry etching using these resists for electron beam exposure, a mixed gas of carbon tetrachloride and oxygen is used as the reaction gas, for example, at 3.56 MHz. It is preferred to use a parallel plate reactive ion etching method using RF.

[Problem to be solved by the invention]

When etching is performed by combining the above-described resist for electron beam exposure with a reactive ion etching method, especially a combination of a positive resist and a reactive ion etching method using a mixed gas of carbon tetrachloride and oxygen as a reactive gas. Therefore, the selectivity ratio with metals such as chrome is approximately 1:1.
However, it has the disadvantage that accurate etching is difficult.

An object of the present invention is to maintain accurate patterning properties, which are the inherent benefits of the combination of a resist for electron beam exposure and a reactive ion etching method using a mixed gas of carbon tetrachloride and oxygen as a reactive gas. It is an object of the present invention to provide a dry etching method that improves the selectivity with metals such as chromium and enables more accurate patterning.

[Means to solve the problem]

The above purpose is to create a resist mask for electron beam exposure (3
), the metal layer (2) is partially covered before being subjected to reactive ion etching using a mixed gas of carbon tetrachloride and oxygen as a reactive gas. The above-mentioned resist mask for electron beam exposure (
3) is achieved by contacting fluorine-based gas plasma to convert the surface of the electron beam exposure resist mask (3) into a hardened resist layer (31).

[Effect]

In the present invention, using a resist for electron beam exposure, such as a positive resist EBR-9 manufactured by Toshi Co., Ltd., the surface is exposed to a plasma of a fluorine-based gas such as carbon tetrafluoride before dry etching a metal such as chrome. The etching resistance of the above resist against a mixed gas plasma of carbon tetrachloride and oxygen is improved, and the etching resistance of the above resist and a metal such as chromium is improved by a mixed gas plasma of carbon tetrachloride and oxygen. Selectivity ratio for plasma is 1:
2, the resist can maintain its shape during the above-mentioned dry etching, and patterning accuracy is improved.

〔Example〕

Hereinafter, an example of manufacturing a photomask having a chrome pattern on a glass substrate using a dry etching method according to an embodiment of the present invention will be described with reference to the drawings.

Referring to FIG. 2, a chrome layer 2 is formed to a thickness of approximately 500 to 2,000 layers on a glass substrate 1 having a thickness of approximately 2.3 mm.

A positive resist for electron beam exposure, such as EBR-9 manufactured by Toshi Co., Ltd., can be spin-coded and exposed using an electron beam shower using another mask, or it can be exposed using an electron beam scanning method. After selectively exposing the resist film, a patterned resist film 3 is formed through a developing process.

Refer to Figure 3 In Figure 0, the above glass substrate is loaded into a parallel plate plasma processing apparatus as shown, for example, 71 is a vacuum container, 72 is a gas supply port, and 73 is a gas discharge port. 74 is, for example, a 3.56 MHz RF power source, 75 is an electrode made of carbon or the like, and 76 is a substrate support stand and electrode.

Refer to Fig. 1a. First, a fluorine-based gas such as carbon tetrachloride is supplied from the gas supply lower 2 at a pressure of about 1 Torr, and the RFlti
When a power of about 350 W is supplied using lI and plasma of fluorine-based gas such as carbon tetrachloride is brought into contact with the positive resist film 3 for electron beam exposure, its surface is hardened and carbon tetrachloride and oxygen The film 31 is converted into a film 31 with high etching resistance against mixed gas plasma. The etching selection ratio of this etching-resistant film 31 and chromium or the like with respect to a mixed gas of carbon tetrachloride and oxygen is 1:2.

See Figure 1b. Converting the reaction gas into a mixed gas of carbon tetrachloride and oxygen,
Perform reactive ion etching.

Since the surface of the positive resist film 3 for electron beam exposure is covered with a film 31 having high etching resistance against plasma of a mixed gas of carbon tetrachloride and oxygen,
Only the metal layer 2, such as chrome, is etched, and the resist mask 3 can maintain its shape during etching, allowing accurate patterning.

Thereafter, the mask is completed by removing the used resist film 3.

〔Effect of the invention〕

As explained above, in the dry etching method according to the present invention, reactive ions using a mixed gas of carbon tetrachloride and oxygen as a reactive gas are applied to the metal layer partially covered by the mask of the resist for electron beam exposure. Prior to etching, the surface of the electron beam exposure resist mask that partially covers the metal layer is brought into contact with fluorine-based gas plasma to harden the surface of the electron beam exposure resist mask. , it is said that the resist layer will be converted to a resist layer with improved etching resistance against mixed gas plasma of carbon tetrachloride and oxygen. The selectivity ratio for etching increases to about 1:2, and the resist can maintain its shape during the dry etching, improving patterning accuracy.

[Brief explanation of the drawing]

FIG. 1a is an explanatory diagram of a resist curing process according to the gist of the present invention. FIG. tb is an explanatory diagram of an etching process according to the gist of the present invention. FIG. 2 is a process diagram of a dry etching method according to an embodiment of the present invention. FIG. 3 is a structural diagram of a parallel plate type plasma processing apparatus used for carrying out the present invention. DESCRIPTION OF SYMBOLS 1... Glass substrate, 2... Metal layer, such as chrome, 3... Resist layer, 31... Hardened resist layer, 71... Vacuum container, 72... Gas supply port, 73... ...Gas exhaust port, 74...RF power supply, 75...Electrode of carbon, etc., 76...Substrate support stand and electrode.

Claims (1)

[Claims] A metal layer (2) partially covered by a resist mask (3) for electron beam exposure is subjected to reactive ion etching using a mixed gas of carbon tetrachloride and oxygen as a reactive gas. A dry etching method characterized in that, prior to this, a plasma of a fluorine-based gas is brought into contact with a mask (3) of the resist for electron beam exposure that partially covers the metal layer (2).