JP2723260B2 - Fine pattern forming method - Google Patents

Description

The present invention relates to a method of forming a fine pattern, and more particularly to a method of forming a fine pattern in the manufacture of an integrated circuit or a microwave semiconductor device using GaAs as a material. About.

(Prior Art) In recent years, the characteristics of integrated circuits such as high-speed static RAMs and multipliers, and microwave semiconductor devices made of GaAs have been dramatically improved with the progress of fine processing technology. Particularly, in a low-noise microwave semiconductor device represented by a high electron mobility transistor, a gate length practically used has reached 0.3 μm or less. As a method for forming such a fine pattern, an electron beam exposure method is widely used. 2 (a) to 2 (c) are diagrams specifically showing a method of forming a resist pattern on a semiconductor substrate using an electron beam exposure method. First, an electron beam resist film 102 is formed on a semiconductor substrate 101 as shown in FIG.
Next, as shown in FIG. 2 (b), the electron beam resist film 102
Is irradiated with the electron beam 103 from the direction indicated by the arrow. When a positive resist film is used as the electron beam resist film 102, a portion irradiated with the electron beam is removed by development as shown in FIG. 2C, and a resist pattern 112 is formed on the semiconductor substrate 101. Is done. By the way, in order to form a resist pattern stably with good reproducibility using the electron beam exposure method, it is necessary to precisely control the exposure conditions and the development conditions of the resist film and to make the diameter of the electron beam incident on the resist film 102 necessary. It is necessary to narrow down to less than the pattern size. In particular, when a resist pattern of about 0.3 μm is formed, electron scattering from the resist or from the semiconductor substrate cannot be neglected. Therefore, it is desirable to narrow the diameter of the electron beam incident on the resist film to 0.1 μm or less. Generally, the diameter of an electron beam incident on a resist film and the electron beam current have a proportional relationship, and the electron beam current and the time required for exposure have an inverse proportional relationship when a resist film having the same sensitivity is used. Therefore, narrowing the electron beam diameter is
The time required for exposure increases, and the number of processes within the time decreases.

(Problems to be Solved by the Invention) As described above, according to the conventional technology, the exposure time is increased, the number of processes per time is reduced, and the electron beam diameter is set to 0.1 μm or less. Since careful maintenance and adjustment of the electron optical system of the exposure apparatus is required, there is also a problem that the operation rate of the electron beam exposure apparatus is greatly reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a resist pattern forming method for efficiently forming a fine resist pattern in view of the above-mentioned conventional problems.

[Configuration of the invention]

(Means for Solving the Problems) According to the method for forming a fine pattern according to the present invention, a first resist film is provided on a semiconductor substrate and subjected to an exposure process and a development process to form a pattern having predetermined openings. Forming a second resist film having a composition different from that of the first resist film and forming a reaction layer with the first resist film on the side surface of the first resist film and the opening thereof; Forming a reaction layer of both resist films, and removing an unreacted layer of the second resist film;
An opening smaller than the opening of the resist film is formed.

(Operation) In the present invention, an opening smaller than the opening of the first resist film is finally obtained, so that the opening provided in the first resist film can be set wider than a predetermined opening size. For this reason,
The second resist film can be formed with sufficient margin with respect to the diameter of the electron beam to be irradiated, and a fine pattern can be easily achieved with good reproducibility without making a hole in the second resist film.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

First, as shown in FIG. 1A, as a first resist film 11 on a semiconductor substrate 101, for example, a positive type electron beam resist PMMA (polymethyl methacrylate) is 1 μm thick.
Then, the first resist film 11 is irradiated with an electron beam 13 according to a predetermined pattern from a direction indicated by an arrow. Next, as shown in FIG. 1B, the first resist film 11 is made of, for example, MIBK (methyl isobutyl ketone) and IPA.
(Ipsopropyl alcohol) is developed using a developing solution obtained by mixing the mixture in a volume ratio of 1: 2, and an opening 11a of, for example, 0.5 μm is formed. When the electron beam exposure method is used, the aperture size is 0.5
Since a pattern of about μm can be formed with a relatively large beam current, the time required for drawing is short.

As the resist film 12, for example, a positive type photoresist AZ1350 (trade name, manufactured by Shipley Co., Ltd.) is applied to a thickness of 0.5 μm, and heat-treated at, for example, 90 ° C. for 10 minutes to form a first resist film.
At the boundary between the second resist film 11 and the second resist film 12, a reaction layer 14 of the two resist films which is not stripped by the stripping process of the second resist film 12 as shown in FIG. 1C is formed. Here, the heat treatment after the application of the second resist film 12 is performed by a reaction layer of both resist films.
Although the aim is to form 14 stably,
It is not always necessary because the reaction layers 14 of both resist films can be formed only by applying the second resist film 12. Next, in order to remove the unreacted second resist film 12, for example, after irradiating an ultraviolet ray on the semiconductor substrate,
Immersion in an AZ developer forms a resist pattern 15 shown in FIG. 1 (d).

The thickness of the resist film on the semiconductor substrate (1) after the unreacted second resist film 12 is stripped is determined by the unreacted reaction layer
Due to the presence of 14, the thickness of the first resist film 12
It has been found that the thickness of the opening becomes smaller by 0.1 μm at the same time. Therefore, when the size of the opening 11a of the first resist film is set to 0.5 μm as in the above embodiment, the size of the opening 23 after the second resist film 12 is removed is
0.3 μm.

In the above embodiment, an example in which AZ1350 is used for PMMA has been described. However, although the dimensions of the openings after the second resist film is peeled off are slightly different, AZ1350 is used for PMIPK, and PMMA is also used for PMIPK.
Alternatively, a combination of resists such as HPR-1182 (trade name, manufactured by GAF) may be used. In addition, the first and second resist films 1
The exposure means used for forming the patterns 1 and 12 is not limited to electron beam exposure, but may be X-ray exposure or a combination thereof. Furthermore, SiO ₂ or A
The present invention is also applicable to the case where the film l is formed.

〔The invention's effect〕

As described above, according to the present invention, after a first resist film is provided on a semiconductor substrate to form a pattern having a predetermined opening, the first resist film and the side surface of the opening are provided with the first resist film. A second resist film having a different composition from that of the first resist film and forming a reaction layer with the first resist film is laminated and formed to form a reaction layer between the two resist films, thereby opening the first resist film. An opening smaller than the hole can be formed.

Therefore, the opening of the first resist film can be set wider than the finally required opening size, so that the first resist film can be formed with a sufficient margin for the diameter of the electron beam to be irradiated, and the second resist film can be formed with a sufficient margin. Since the required holes can be formed simply by peeling after applying the resist film, a remarkable effect that a fine pattern having a hole size of about 0.3 μm or less can be easily achieved with good reproducibility. There is.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 (a) to 1 (d) are sectional views showing a method of forming a fine pattern according to one embodiment of the present invention in the order of steps, and FIGS.
1A to 1C are cross-sectional views showing a conventional fine pattern forming method in the order of steps. 11 First resist film 12 Second resist film 13 Electron beam 14 Reaction layer 15 Resist pattern 101 Semiconductor substrate

Claims (1)

(57) [Claims] A step of providing a first resist film on a semiconductor substrate, performing an exposure process and a development process on the first resist film to form a pattern having a predetermined opening, and forming the first resist film and the opening of the opening. Laminating and applying a second resist film having a composition different from that of the first resist film and forming a reaction layer with the first resist film on a side surface to form a reaction layer of both resist films; Removing the unreacted layer of the second resist film, and forming an opening smaller than the opening of the first resist film.