JPH0594982A - Manufacture of resist film - Google Patents

Abstract

PURPOSE:To enable a resist pattern to be enhanced in accuracy by a method wherein a silicon nitride film formed on a semiconductor substrate is surface- treated with acylating agent or alkylating agent, and then resist provided with carboxyl groups as side chains is applied onto the surface of the film, and then the substrate is thermally treated. CONSTITUTION:A silicon nitride film 2 formed on a semiconductor substrate 1 is surface-treated with acylating agent or alkylating agent. Resist 3 provided with carboxyl groups as side chains is applied onto the surface of the silicon nitride film 2 and thermally treated at a temperature of over 150 deg.C. By this setup, the insolubilized resist film 3a on the base of an opening of the resist 3 can be lessened after exposure and development. Therefore, a resist pattern can be enhanced in accuracy, so that a fine resist pattern can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a resist film, and more particularly to a method for producing a resist film in an electron beam lithography process.

[0002]

2. Description of the Related Art Conventionally, various copolymer resists using methacrylic acid as one of the monomers have been developed as positive resists having sensitivity to electron beams, and fine resists have been developed. It is used for processing. A method of forming a resist pattern on a substrate with a methacrylic acid-phenyl methacrylate copolymer resist film which is a general resist having a carboxyl group as a side chain will be described.

As shown in FIG. 2, first, as a substrate, G
After laminating the silicon nitride film (2) on the aAs substrate (1),
A methacrylic acid-phenyl methacrylate copolymer resist (3) was applied with a spin coater to a thickness of 1500Å,
Pre-bake at 230 ° C. for 2 hours. Then, a pattern with a 1500 Å line width is drawn by electron beam exposure, and then methyl isobutyl ketone-ethylcyclohexanol (8
Development is performed with a mixed solution of 0:20) to form a desired resist pattern.

In the above resist pattern forming method, when the resist (3) having a carboxyl group as a side chain is applied to the silicon nitride film (2) and prebaked at 150 ° C. or higher, the resist after exposure and development is used. The insolubilized resist film (3b) may remain on the bottom surface of the opening of (3). Therefore, there is a problem that it is necessary to separately remove the insolubilized resist film (3b) by etching with oxygen plasma or the like.

Further, in etching by oxygen plasma or the like, it is difficult to perform anisotropic processing with good reproducibility at a level of several hundred liters, and at the same time as removing the insolubilized resist film (3b), the resist (3) The opening is laterally etched and the line width is increased. For example,
Generally, an insolubilized resist film (3
When removing b), etching of about 250 to 300 Å is required, but this etching increases the line width of the resist (3) by 500 to 600 Å, which causes a decrease in the accuracy of the resist pattern. was there.

Furthermore, reactive ion etching (RI
Although a method of anisotropically etching the resist (3) with E) to reduce the lateral etching of the opening of the resist (3) has been considered, reactive ion etching damages the semiconductor substrate (1). And is not suitable for forming a shallow channel layer directly under the opening of the resist (3). In some cases, a heat treatment step must be performed to recover damage. there were.

The present invention has been made in view of the above problems, and it is possible to reduce the generation of an insolubilized resist film on the bottom surface of the opening of the resist after exposure and development, and improve the resist pattern accuracy. It is an object to provide a film manufacturing method.

[0008]

In order to solve the above-mentioned problems, according to the present invention, after a silicon nitride film formed on a semiconductor substrate is surface-treated with an acylating agent or an alkylating agent, It is characterized in that a resist having a carboxyl group as a side chain is coated on the silicon nitride film and heat-treated at a temperature of 150 ° C. or higher.

[0009]

In general, a resist having a carboxyl group as a side chain is coated on a silicon nitride film deposited on a semiconductor substrate,
When the heat treatment is performed at a temperature of 0 ° C. or higher, a resist film having poor solubility in a developing solution is formed at the interface between the silicon nitride film and the resist. It is considered that this is because a dehydration reaction occurs between the carboxyl group of the resist and the imino group or amino group on the surface of the silicon nitride film, and a part of the silicon nitride film and the resist bond to insolubilize the resist at the interface. Be done.

Therefore, according to the above-mentioned method, after the silicon nitride film formed on the semiconductor substrate is surface-treated with an acylating agent or an alkylating agent, the silicon nitride film has a carboxyl group as a side chain. Apply resist and apply 1
By performing the heat treatment at a temperature of 50 ° C. or higher, the imino group or amino group on the surface of the silicon nitride film is hydrophobized by acylation or alkylation, and the reactivity of the resist with the carboxyl group is reduced, so that the silicon nitride film The bond with the resist is reduced, and the generation of an insolubilized resist film on the bottom surface of the opening of the resist after exposure and development is reduced.

[0011]

EXAMPLES AND COMPARATIVE EXAMPLES Examples of the method for producing a resist film according to the present invention will be described. It should be noted that components having the same functions as those of the conventional example are designated by the same reference numerals.

Example 1 As shown in FIG. 1, first, a silicon nitride film (2) was laminated on a GaAs substrate (1) as a substrate, and then a GaAs substrate (1) on which a silicon nitride film (2) was laminated. ) As an acylating agent in a mixture of acetic acid and acetic anhydride (1: 1) at room temperature.
After immersing for a time to perform surface treatment of the silicon nitride film (2),
It was washed with isopropanol and dried.

Next, a methacrylic acid-phenyl methacrylate copolymer resist (5% by weight methyl cellosolve acetate solution containing 25.4 mol% of methacrylic acid component and 74.6 mol% of phenyl methacrylate component) (3) was applied by a spin coater at 1500Å. And a pre-bake at 230 ° C. for 1 hour. Then, using the electron beam exposure apparatus,
Draw a line pattern of 3 nC / cm on the resist (3),
It was developed with a mixed solution of methyl isobutyl ketone-ethyl cyclohexanol (80:20).

Next, by the oxygen plasma etching method,
The insolubilized resist film (3a) on the bottom of the opening of the resist (3) is etched by 90Å, then the silicon nitride film (2) is etched with an aqueous solution of hydrogen fluoride, and the resist pattern is used as a mask on the GaAs substrate (1). Aluminum was vapor-deposited at 2000 liters. The produced aluminum metal electrode in this case had a line drawing of 0.15 μm.

After prebaking as described above,
When the resist (3) is dissolved and peeled off with acetone, which is a good solvent for the resist (3) without electron beam exposure, an insolubilized resist film (3a) of about 90 Å is formed on the surface of the silicon nitride film (2). ) Was observed. The results are shown in Table 1 together with other examples and comparative examples.

Example 2 As in Example 1, the substrate (1) on which the silicon nitride film (2) was laminated was immersed in acetyl bromide as an acylating agent at room temperature for 3 hours to form a silicon nitride film (2). After the surface treatment, it was washed with isopropanol and dried. Then, a methacrylic acid-phenyl methacrylate copolymer resist (5% by weight methyl cellosolve acetate solution containing 25.4 mol% of methacrylic acid component and 74.6 mol% of phenyl methacrylate component) (3) was applied with a spin coater to a thickness of 1500Å. Then, the resist (3) was pre-baked at 230 ° C. for 1 hour, and the resist (3) was dissolved and peeled off with acetone which was a good solvent for the resist (3).

Example 3 As in Example 1, the substrate (1) on which the silicon nitride film (2) was laminated was immersed in allyl bromide as an alkylating agent for 3 hours at room temperature to form a silicon nitride film (2). After the surface treatment, it was washed with isopropanol and dried. Then, a methacrylic acid-phenyl methacrylate copolymer resist (5% by weight methyl cellosolve acetate solution containing 25.4 mol% of methacrylic acid component and 74.6 mol% of phenyl methacrylate component) (3) was applied with a spin coater to a thickness of 1500Å. Then, the resist (3) was pre-baked at 230 ° C. for 1 hour, and the resist (3) was dissolved and peeled off with acetone which was a good solvent for the resist (3).

Comparative Example 1 Similar to Example 1, the substrate (1) having the silicon nitride film (2) laminated thereon was not subjected to surface treatment with an acylating agent or an alkylating agent, and the same resist as in Example 1 was used. (3) was applied and prebaked at 230 ° C. for 1 hour. Then, using an electron beam exposure apparatus, the resist (3) is exposed to 3 nC / cm.
Was drawn and developed with a mixed solution of methylisobutylketone-ethylcyclohexanol (80:20). Next, the insolubilized resist film (3b) was etched by the oxygen plasma etching method. On this occasion,
The etching film thickness of the insolubilized resist film (3b) is 20
Below 0 Å, the insolubilized resist film (3b) could not be completely removed. Then, when the silicon nitride film (2) was further etched with an aqueous hydrogen fluoride solution, the silicon nitride film (2) could not be etched or a part of the silicon nitride film (2) that was not etched was produced. After the insolubilized resist film (3b) was etched by 200Å, aluminum was evaporated by 2000Å on the GaAs substrate (1) using the resist pattern as a mask. The aluminum metal electrode produced in this case had a line drawing of 0.2 μm.

[0019]

[Table 1] As is clear from Table 1, when the resist (3) is applied after the surface of the silicon nitride film (2) is treated with an acylating agent or an alkylating agent, the resist is insoluble after exposure and development of the resist (3). It was found to reduce the formation of the membrane (3a). Therefore, a resist pattern with a fine line width could be drawn.

In this Example, the case where acetic acid and acetic anhydride mixture and acetyl bromide were used as the acylating agent and allyl bromide was used as the alkylating agent was explained, but the present invention is not particularly limited. Not what is done,
It is considered that other acylating agents or alkylating agents can also obtain similar effects. Further, the case where a methacrylic acid-phenyl methacrylate copolymer resist is used as a resist having a carboxyl group as a side chain is described, but the present invention is not particularly limited to this, and other carboxyl groups may be used. It is also possible to use a resist having a side chain.

[0021]

According to the method of forming and forming a resist film according to the present invention, a silicon nitride film formed on a semiconductor substrate is surface-treated with an acylating agent or an alkylating agent and then exposed on the silicon nitride film. By coating a resist having a carboxyl group as a chain and heat-treating at a temperature of 150 ° C. or higher, the imino group or amino group on the surface of the silicon nitride film is hydrophobized by acylation or alkylation,
Decrease the reactivity of the resist to carboxyl groups,
Bonding between the silicon nitride film and the resist can be reduced. That is, it is possible to reduce the generation of an insolubilized resist film on the bottom surface of the opening of the resist after exposure and development. Therefore, it is possible to improve the accuracy of the resist pattern and form a fine resist pattern.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a semiconductor substrate for explaining a resist pattern formed by a method for producing a resist film according to the present invention.

FIG. 2 is a schematic cross-sectional view of a semiconductor substrate for explaining a resist pattern formed by a conventional resist film forming method.

[Explanation of symbols]

 1 substrate 2 silicon nitride film 3 resist

Claims (1)

[Claims] 1. A silicon nitride film formed on a semiconductor substrate is surface-treated with an acylating agent or an alkylating agent, and then a resist having a carboxyl group as a side chain is applied to the silicon nitride film, and the temperature is 150 ° C. A method for producing a resist film, which comprises performing heat treatment at the above temperature.