JPH07273007A - Resist pattern forming method - Google Patents

Abstract

PURPOSE:To form the microscopic pattern of a chemically amplified negative resist film on a GaAs substrate. CONSTITUTION:A GaAs substrate is sulfurized by dipping it into an (NH4)2S4 solution, and after a sulfide layer has been formed on the surface of the GaAs substrate, a novolac resin chemically amplified resist film is applied thereon, and an exposing operation is conducted by the irradiation of an electron beam. Then, the above-mentioned material is baked by a hot plate, a crosslinking reaction is progressed using an acid generated by exposure, and a microscopic pattern is formed by developing. The adsorption and diffusion of the acid to the GaAs substrate can be suppressed by the sulfide layer, and the exfoliation of a resist pattern and the deterioration of pattern accuracy can also be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a resist pattern, and more particularly to a method for forming a fine pattern using a chemically amplified resist.

[0002]

2. Description of the Related Art A dot-shaped quantum device for observing the quantum size effect of a semiconductor by processing a semiconductor substrate at the nanometer level is manufactured by using a positive electron beam resist, which has a higher resolution than a negative resist for an electron beam. A method has been employed in which a resist pattern is formed using a resist, a metal or the like is vapor-deposited to transfer the pattern, and then the pattern is etched. In addition, there is also a method of increasing the resolution by applying positive resist films having different molecular weights in multiple layers and then patterning.

On the other hand, a chemically amplified electron beam negative resist, which has recently been developed as a resist having high sensitivity and high resolution and high etching resistance, has been attracting attention.

In the chemically amplified negative resist film, the acid generator generates an acid in proportion to the irradiation amount by electron beam irradiation, and this acid serves as a catalyst by the heat treatment after the electron beam exposure and the base resin and the cross-linking agent. The cross-linking reaction with and progresses and becomes insoluble in the developing solution. Next, a fine pattern can be formed by developing this resist film with a developing solution.

However, in this chemically amplified negative resist film, the cross-linking reaction of the resist in the vicinity of the interface with the substrate does not proceed sufficiently depending on the material of the underlying substrate, and biting occurs, and the cross-sectional shape of the resist pattern becomes an inverse taper shape that narrows downward. Then, there is a problem that the resist film is peeled off and the pattern accuracy is deteriorated.

In this phenomenon, the acid generated near the interface with the substrate by electron beam irradiation is diffused or adsorbed on the substrate, and as a result, the crosslinking reaction of the resist film near the interface does not proceed and the resist pattern of the resist pattern is not formed. Biting occurs and the shape becomes an inverse taper.

For Si substrates, the journal of
The Electrochemical Society (Journal
of the Electrochemical S
1983, vol. 133, p. 619, hexamethyldisilazane (HM
It is known that the surface is made hydrophobic by treatment with DS) or the like. By using this method, it is possible to suppress the adsorption of acid on the Si substrate, and a fine pattern is formed by the chemically amplified negative resist film. it can.

[0008]

In this conventional resist pattern forming method, the HMD effective for the Si substrate is obtained.
S treatment has no effect on GaAs substrate,
There has been a problem that the resist film is peeled off or the pattern accuracy is deteriorated due to the biting of the cross-sectional shape of the resist pattern of the chemically amplified negative resist film formed on the surface of the substrate.

This phenomenon is caused by the fact that, in the case of a Si substrate, OH groups remain on the surface of the Si substrate in the surface cleaning step and the OH group becomes hydrophilic due to the HMDS treatment.
Is replaced with Si (CH ₃ ) ₃ and silylation occurs to make it hydrophobic, whereas the surface of the GaAs substrate has no OH group and silylation due to HMDS treatment does not occur. Therefore, in the case of GaAs substrate, the pattern is transferred to the metal film by using the conventional electron beam positive resist film,
The method of etching the GaAs substrate using this metal film pattern as a mask has to be adopted, which not only complicates the process but also suppresses miniaturization of the pattern.

An object of the present invention is to provide a method for forming a fine resist pattern for finely processing the surface of a GaAs substrate.

[0011]

According to the method of forming a resist pattern of the present invention, a GaAs substrate is dipped in a (NH ₄ ) ₂ S _x solution so that the surface is subjected to a sulfurating treatment and then a chemically amplified negative resist is formed on the surface of the GaAs substrate. A step of applying a film, a step of selectively exposing the chemically amplified negative resist film with an electron beam and then a heat treatment to cause a crosslinking reaction, and a step of developing the chemically amplified negative resist film to form a fine pattern And a process.

[0012]

EXAMPLES When a GaAs substrate is dipped in a (NH ₄ ) ₂ S _x solution and surface-treated (hereinafter referred to as sulfurization treatment), a sulfide layer of 1 to several atomic layers is deposited on the surface of the GaAs substrate (surface science). , 1990, Vol. 11, No. 8, p. 9)). It was found that the sulfide layer on the GaAs substrate has a function of suppressing the adsorption and diffusion of the acid generated by the electron beam exposure of the chemically amplified negative resist film on the GaAs substrate. As a result, a fine pattern of the chemically amplified resist film can be formed on the GaAs substrate.

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a process chart showing an embodiment of the present invention.

As shown in FIG. 1, first, clean GaAs is used.
The substrate is dipped in a (NH ₄ ) ₂ S _x solution for 20 minutes or more to sulphate the surface to form a sulphide layer on the surface of the GaAs substrate.

Next, the GaAs substrate taken out from the (NH ₄ ) ₂ S _x solution is exposed to running water for several minutes to be sufficiently washed with water.

Next, nitrogen gas is blown onto the surface of the GaAs substrate to dry it.

Next, a chemically amplified resist film containing a novolac resin as a base resin is applied on the surface of the GaAs substrate and prebaked for about 20 minutes in an N ₂ gas atmosphere at 90 to 130 ° C.

Next, the chemically amplified resist film is irradiated with an electron beam to expose, for example, an array of square patterns having a side of 15 μm, and after exposure, postbaking is performed for 1 to 3 minutes on a hot plate at 85 to 105 ° C. Allow the crosslinking reaction to proceed.

Here, the acid generated by the electron beam irradiation is converted into G by the sulfide film formed on the surface of the GaAs substrate.
It can be prevented from being adsorbed and diffused on the aAs substrate.
The cross-linking reaction of the resist film proceeds even near the interface with the aAs substrate.

Next, the chemically amplified resist film is developed with an alkali developing solution and rinsed with pure water to obtain a fine pattern.

Thereafter, the GaAs substrate is etched by using the patterned chemically amplified resist film as a mask, and G
It is possible to construct a quantum dot device in which a needle-shaped pattern is formed on a surface of an aAs substrate in a large area and at a high density.

[0023]

As described above, the present invention is based on GaAs
An effect that a fine pattern of a chemically amplified resist film can be formed by sulfurating the surface of a substrate with a (NH ₄ ) ₂ S _x solution, and a GaAs quantum dot device can be formed by a simpler process than before. Have.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of the present invention.

Claims (1)

[Claims] 1. A step of applying a chemically amplified negative resist film to the surface of the GaAs substrate after immersing the GaAs substrate in a (NH ₄ ) ₂ S _x solution to subject the surface to sulfurization treatment, and the chemically amplified negative resist film. Forming a fine pattern by developing the chemically amplified negative resist film by developing the fine pattern by selectively exposing the film to an electron beam and then subjecting it to heat treatment for crosslinking reaction. .