JPH05251335A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To eliminate that an acid generated on the surface of a positive-type resist film is deactivated when it is reacted with moisture or oxygen in the air by a method wherein the surface of the resist film is coated with a thin film and this assembly is exposed to light. CONSTITUTION:A semiconductor substrate 1 is coated with a chemical- amplification type positive resist film 2; after that, a baking operation is executed. Then, a water-soluble polymer thin film 3 as a thin film for surface protection use is coated; a baking operation is executed. Then, while a mask 4 is used, an exposure operation is executed by using an excimer laser beam 5; after that, a heating operation is executed. Then, an alkali development operation is executed; a fine pattern 2A composed of the resist film is formed. At this time, the water-soluble polymer thin film 3 as the thin film for surface protection use is stripped by an alkali developing solution. When an acid generated after the exposure operation and the baking operated is reacted with oxygen or moisture in the air near the surface, it is not deactivated. An acid catalytic reaction progresses inside the resist film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a resist film in a lithography process.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor device manufacturing process, a method of forming a fine pattern using a chemically amplified positive resist film utilizing an acid catalyst reaction has been used. This method includes, for example, a method using a polarity change type resist, which is described in Itoh.
Symposium Series (ACS Symposium
Series) no242, P11 (1984).

The method using a chemically amplified resist uses a chain reaction or a catalytic reaction, and active species in the resist generated by the action of one photon cause many chemical reactions. An acid generator is often used as an active species that causes a chain reaction or a catalytic reaction.
The acid generator is used in the wavelength range from near ultraviolet to far ultraviolet (Deep
It has absorption in the UV region and generates acid by photolysis.

The polarity change type resist is composed of an acid generator and a polymer having a side chain with an alkali protecting group and an alkali-soluble main chain. The acid generated from the acid generator becomes an active species, and the polymer is heated by heat. The side chains are decomposed in a chain manner, and this decomposition makes the polymer soluble in a polar solvent such as an alcohol or an aqueous alkali solution. Figure 2
Will be explained.

First, as shown in FIG. 2 (a), a chemically amplified positive type of a semiconductor substrate 1 having an acid generator and a side chain having a protecting group from an alkali and a main chain made of an alkali-acceptable polymer. The resist film 2 is formed by a coating method. Next, heat is applied to remove the residual solvent in the resist film 2. Next, as shown in FIG. 2B, when exposure is performed through the mask 4 using, for example, excimer laser light 5, acid is generated from the acid generator in the exposed portion. Then, by heating, the acid generated from the acid generator exerts a catalytic action, and continuously decomposes a polymer in which the side chain has a protective group from alkali and the main chain is alkali-soluble. When this is developed with a polar solvent such as alcohol or an alkaline aqueous solution,
As shown in (c), the exposed portion is dissolved, and as a result, a positive type fine pattern 2B is formed.

[0006]

The chemically amplified positive type resist used in the method of forming a fine pattern in the conventional manufacturing process of a semiconductor device described above has a resist film surface which is in contact with air. The generated acid reacts with moisture or oxygen in the air to be decomposed, so that the acid concentration on the surface of the resist film becomes low, and the projections 6 are generated on the obtained resist pattern. Therefore, during etching, the active species of etching are blocked by the projections 6 on the upper portion of the resist pattern, which makes it difficult to accurately transfer the resist pattern to the underlying layer, resulting in a decrease in the yield of semiconductor devices.

[0007]

According to the method of manufacturing a semiconductor device of the present invention, a chemically amplified positive resist film is formed on a semiconductor substrate, and then the positive resist film is exposed and developed using a mask. In the manufacturing method, the surface of the positive resist film is coated with a thin film and then exposed.

[0008]

The present invention will be described below with reference to the drawings.

First, as shown in FIG. 1A, a chemically amplified positive resist film 2 is applied on a semiconductor substrate 1 and then baked. Next, as a thin film for surface protection, for example,
A water-soluble polymer thin film 3 such as polyvinyl alcohol or casein is applied in a thickness of 100 to 300 nm and baked.

Next, as shown in FIG. 1 (b), a mask 4 is used to perform exposure using an excimer laser beam 5, and then heating is performed.

Next, as shown in FIG. 1C, a fine pattern 2A made of a resist film is developed by alkali development.
To form. Here, the surface protection thin film, for example, the water-soluble polymer thin film 3 such as polyvinyl alcohol is peeled off by the alkali developing solution. By using the fine pattern 2A as a mask to etch the base, the pattern can be accurately transferred.

[0012]

As described above, the present invention is a resist method for providing a positive pattern by using a chemically amplified positive type resist which utilizes an acid catalyst reaction. After resist coating and baking, the resist film surface is covered with oxygen in the air. And by applying a water-soluble polymer thin film such as polyvinyl alcohol as a surface protection thin film for protecting from moisture, etc., the acid generated after exposure / baking with excimer laser light is not affected by oxygen or moisture in the air near the surface. Since the acid-catalyzed reaction proceeds in the resist film without reacting with the reaction, no protrusion appears on the resist pattern and a rectangular pattern is obtained. Therefore, a fine pattern having an excellent shape can be formed during etching. Furthermore, when a water-soluble polymer thin film such as polyvinyl alcohol is used for this surface protection thin film, mixing with the chemically amplified positive resist film does not occur, so that the thin film can be easily applied. In addition, the water-soluble polymer thin film can be peeled off at the time of alkali development, and no polluting gas is emitted during etching.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor chip for explaining an embodiment of the present invention.

FIG. 2 is a sectional view of a semiconductor chip for explaining a conventional example.

[Explanation of symbols]

 1 semiconductor substrate 2 chemically amplified positive resist 2A, 2B fine pattern 3 water-soluble polymer thin film 4 mask 5 excimer laser light 6 protrusion

Claims (3)

[Claims] 1. A method of manufacturing a semiconductor device, comprising forming a chemically amplified positive type resist film on a semiconductor substrate and then exposing and developing the positive type resist film using a mask, wherein the surface of the positive type resist film is a thin film. A method for manufacturing a semiconductor device, which comprises exposing after coating. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the thin film for coating is made of a water-soluble polymer. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the thin film is peeled off at the same time as the development of the positive type resist film with a polar developer.