JPH0453954A - Formation of resist pattern - Google Patents

Abstract

PURPOSE:To form a fine resist pattern capable of application to a dry etching by applying a resist added Tetra-n-butyl ammonium perchlorate (TnBAP) on a substrate, then extracting TnBAP in an upper layer of resist and heating it. CONSTITUTION:The resist which TnBAP added to polymethyl methacrylate is used, and TnBAP in the applied resist surface is extracted with a lower alcohol and heated, then the solubility of a part extracted TnBAP into a developer is decreased. When developed after exposure on the desired pattern, a sharper resist pattern on a flank than the substrate is formed, because the wear of the film on the upper layer part of the unexposed portion does not occur so much. Hence the film resist pattern capable of application to dry etching is formed.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a method for forming a resist pattern used in the manufacture of semiconductor integrated circuit devices, and in particular to a method for forming a resist pattern for microfabrication by dry etching processing. Regarding.

(b) Conventional technology In order to improve the degree of integration of semiconductor integrated circuit devices, radiation-sensitive materials used to form fine patterns include
They are required to have high sensitivity to radiation such as beams, electron beams, ultraviolet rays, and deep ultraviolet rays, and to have high resolution.

Therefore, in Japanese Patent Publication No. 1-25054, the applicant added tetrabutylammonium perchlorate (particularly tetra-n-butylammonium perchlorate) as a sensitizer to polymethyl methacrylate (hereinafter referred to as PMMA), and added it to polymethyl methacrylate (hereinafter referred to as PMMA). We provide positive radiation-sensitive materials with increased sensitivity and high resolution.

When creating a floating mask using such a sensitive material (resist), first, the surface of a chrome blank (a glass substrate with a chromium film deposited on the entire surface) or a chromium film is coated with chromium oxide. A resist is applied to the surface of the chrome blank, and after prebaking, a desired pattern is drawn using an electron beam, and wet development is performed using a developer consisting of a mixture of methyl cellosolve and isopropyl alcohol. Then, post-baking is performed to remove (light ash) the remaining unnecessary resist (remaining in the area irradiated with the electron beam), and then the chromium film is removed by wet etching using the formed resist pattern as a mask. Furthermore, all the resist was removed to obtain 7 otomasks with the desired pattern.

However, when etching is performed by wet etching, it is difficult to manage etching conditions, and it is difficult to achieve uniform etching and control the amount of etching. In addition, the process is relatively complicated, and there are problems such as the risk of environmental pollution due to waste liquid from wet etching, so it is desired to switch to a dry etching process.

In the above case, even when wet etching the lower layer film (chrome film in the above case) using the formed resist pattern as a mask, the etching solution may seep between the resist and the lower layer film (chrome film). , it was difficult to control microfabrication at the submicron level.

(c) Problems to be Solved by the Invention In the above-mentioned resist, tetrabutylammonium perchlorate added as a sensitizer increases the solubility in the developing solution, so the film does not form in the upper layer of the unexposed area. The resist pattern thus formed has a trapezoidal shape as shown in FIG.

When anisotropic dry etching such as reactive ion etching (RIE) is performed using such a trapezoidal resist pattern as a mask, the resist pattern is also etched, and the resist around the base of the trapezoid is removed. etching with high precision was not possible.

The present invention has been developed in view of the above problems, and uses a resist that is highly sensitive to radiation to form a fine resist pattern that can be applied to dry etching.

(d) Means for Solving the Problems The present invention comprises a step of applying a resist in which tetrabutylammonium perchlorate is added to PMMA on a substrate;
A step of extracting tetrabutylammonium perchlorate on the surface of the applied resist with a lower alcohol, a step of heating the resist from which the tetrabutylammonium perchlorate on the surface has been extracted, a step of exposing the resist in a desired pattern, and exposure. A method for forming a resist pattern includes a step of developing the resist.

(e) Effect Using a resist to which tetrabutylammonium perchlorate has been added, extract the tetrabutylammonium perchlorate on the surface of the applied resist with lower alcohol and heat it to remove the area from which the tetrabutylammonium perchlorate has been extracted. The solubility in the developer decreases.

Then, after exposure to a desired pattern, development is performed to form a resist pattern in which film thinning in the upper layer portion of the unexposed portion is not significant and whose side surfaces are steep with respect to the substrate.

(f) Example FIG. 1 is a process explanatory diagram of an embodiment of the method of the present invention.

In this embodiment, manufacturing of 7 otomasks will be explained as an example.

First, 4g of PMMA (weight average molecular weight Mw=IXI
O', ratio with number average molecular weight Mn Mw/Mn = 1.5)
was dissolved in 100 g of methyl cellosolve acetate, and then tetra-n-butylammonium perchlorate (hereinafter referred to as T
A resist is prepared by adding 0.6 g of nBAP).

The prepared resist (3) is applied to a film thickness of 50 mm on a glass substrate (1) having a chromium film (2) of 800 m thick as a substrate.
00, and prebaked at 180° C. for 1 hour (Fig. 1A).

Next, the glass substrate (1) coated with the resist was soaked in methyl alcohol (temperature 22°C) as a lower alcohol for 1 hour.
TnBAP on the resist (3) surface (upper layer)
(Fig. 1 B y, '--Then, bake at 180°C for 30 minutes.

Next, a desired pattern is irradiated and drawn using an electron beam with an acceleration voltage of 20 keV, a beam current of 1×10'A, and an exposure dose of 2 μC/crn (Fig. 1C). Then, methyl cellosolve and isopropyl alcohol are mixed at a volume ratio of 72.5. : 2
Using the developer mixed in step 7.5, develop for 13 minutes at a temperature of 22°C to remove the exposed area and form the desired resist pattern.
Form a turn (Fig. 1D).

At this time, the substrate (1
) was approximately 80°.

Note that the angle between the side surface of the resist pattern and the substrate formed by exposure and development under the same conditions without extracting TnBAP is 5.
It was 5°.

Here, FIG. 2 shows the dissolution characteristics of a resist prepared by adding TnBAP to PMMA in a developer containing a mixture of methyl cellosolve and isopropyl alcohol.

Here, 5000 resists were applied to the substrate, and 180
After prebaking at 180°C for 1 hour, a was dissolved in a developer as it was, b was baked at 180°C for 30 minutes,
C is TnB after soaking in methyl alcohol at 22℃ for 15 minutes.
AP is extracted, and d is the same as C, without TnBAP extracted, and then further baked at 180° C. for 30 minutes.

As is clear from this figure, when TnBAP is heat-treated (baked) after being extracted, its solubility in the developer is extremely reduced.

In the present invention, by shortening the extraction time of TnBAP and extracting TnBAP from the upper layer of the resist, the thinning of the upper layer during development is reduced while maintaining high sensitivity to radiation in the lower layer of the resist. The side surface of the formed resist pattern can be made steeper with respect to the substrate.

After developing the exposed resist (3), it is washed with isopropyl alcohol for 1 minute at room temperature, and then post-baked at 180° C. for 30 minutes.

Then, using a parallel plate type RIE device, 0.0% etching gas was applied. Light ashing of the resist remaining in the exposed areas is performed using gas.

Subsequently, using the RIE device, the etching gas was changed to C1,1.
0, WetAir was added to the system gas, gas pressure was 200mTorr, and RF output was 0.35W/cm'.
Etching is performed for 2 minutes under the following conditions. As a result, the chromium film (2) exposed without being masked by the resist (3)
All parts are removed (Fig. 1E).

After that, apply etching gas to 0. Etching is performed using a gas to remove the remaining resist (3), completing the 7th mask (FIG. 1F).

(g) Effects of the invention As is clear from the above description, the present invention provides TnBAP
After applying the resist to which TnBAP is added to the substrate, the TnBAP in the upper layer of the resist is extracted and further heated, thereby reducing the solubility of the TnBAP-extracted portion in the developer. As a result, while maintaining high sensitivity to exposure light in the lower layer of the resist, film thinning in the upper layer of the unexposed portion is reduced, and a resist pattern with steep side surfaces relative to the substrate is formed. As a result, a fine resist pattern that can be applied to dry etching is formed, making it possible to dry the semiconductor manufacturing process and improve productivity.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a process according to an embodiment of the method of the present invention, FIG. 2 is a diagram showing the dissolution characteristics of a resist in a developer according to the method of the present invention, and FIG. 3 is an explanatory diagram of a conventional resist pattern.

Claims (3)

[Claims] (1) A process of applying a resist made by adding tetrabutylammonium perchlorate to polymethyl methacrylate on a substrate, a process of extracting tetrabutylammonium perchlorate on the surface of the applied resist with a lower alcohol, and a process of extracting tetrabutylammonium perchlorate on the surface of the applied resist. A method for forming a resist pattern, comprising the steps of: heating the resist from which is extracted; exposing the resist to a desired pattern; and developing the exposed resist. (2) The method for forming a resist pattern according to claim 1, wherein the tetrabutylammonium perchlorate is tetra-n-butylammonium perchlorate. (3) The method for forming a resist pattern according to claim 1 or 2, wherein the lower alcohol is methyl alcohol.