JPS6112030A - Pattern forming method using two-layer resist - Google Patents

Abstract

PURPOSE:To improve the dissolving speed of the resist polymer of the lower layer as well as to reduce the deterioration in quality of image due to the interaction of a pattern part by a method wherein the thin polymer resist of the upper layer is cooled quickly after baking. CONSTITUTION:The first layer of resist 3 is coated on the surface of the film 2 to be processed on a substrate 1 in sufficient thickness with which the effect of stepping can be neglected. Subsequently, said resist layer is baked at the prescribed temperature for the prescribed period of time. Then, the second layer resist 4 to be used for high resolution patterning is coated on said resist 3. Subsequently, a baking is performed again on the second layer resist 4 under the designated baking conditions, and a resist film is completed. Then, a necessary part is exposed 5 using a suitable light source of exposure. After the second layer resist is developed and the desired pattern in vertical profile is obtained on the first layer resist, a baking is performed again, and the above is immediately cooled quickly to room temperature. As a result, the solubility of the first layer resist is improved, and the range of selectivity of developing solvent is made wider, thereby enabling to control the profile properly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for processing a high-density positive resist applied in the manufacture of high-density semiconductor integrated circuits, high-frequency semiconductor devices, etc., and particularly relates to a method for forming a resist film. It is something.

[Technical background of the invention and its problems]

For semiconductor integrated circuits and high frequency semiconductor devices.

Higher densification is progressing, and thin film microfabrication technology has become an extremely important elemental technology.

As the minimum dimension is reduced to the submicron region, the aspect ratio inevitably increases, and in addition, it is extremely difficult to control the dimensions on a more complicated step structure. In addition, interference effects of light reflected from steps on the surface of the workpiece and proximity effects in electron beam exposure must also be taken into consideration. A so-called multiple resist process is used as one means to solve these problems. Its main feature is a thick layer for smoothing at the bottom,
A thin resist layer for patterning is provided on the top, and although there are several variegation types, the two-layer structure will be explained here.

According to this method, the upper layer pattern has a vertical profile and the desired purpose can be achieved, but if the conditions are not selected carefully when developing the lower resist layer, the pattern portion that should be left and the developing solvent Due to this effect, it was difficult to control the profile, and the accuracy obtained in the upper layer could not be maintained in the lower layer.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a resist process that is capable of responding to microfabrication in the submicron region and is highly dense.

[Summary of the invention]

Hereinafter, the present invention will be explained with reference to the drawings.

First, as shown in FIG. 11 ((roll)), a first layer of resist (3) is applied to the surface of the film to be processed (2) on the substrate (1) with a sufficient thickness so that the effect of the step can be ignored. , this resist layer is baked at a predetermined temperature and for a predetermined time.

Next, a second layer resist (4) for highly disintegrated battanning is thinly applied onto this resist (3). Thereafter, baking is performed again under the baking conditions specified for the second layer resist (4) to complete the resist film. Thereafter, necessary portions are exposed to light β) using an appropriate exposure light source. 1st
Figures 1 and 2) are cross-sectional views of the current process of forming the second layer of resist, after which a desired pattern with a vertical profile can be obtained on the second layer of resist. This is then baked again and then quickly cooled to room temperature. This increases the solubility of the polymer resist and greatly contributes to improving the solubility of permanent cysts. Therefore, the selection range of current solvents can be expanded and the profile can be controlled. Also,
This baking serves as a post-bake for the A two-layer resist after the phenomenon occurs, and prevents profile deterioration in subsequent processes. As described above, the main component of the present invention is to develop and bake the second layer resist and then rapidly cool it to develop the first layer resist in forming a pattern of the two layer resist. FIG. 1(e) shows a cross section of the completed resist pattern. Note that in order to obtain this rapid cooling effect, the post-baking temperature of the second layer resist must be higher than the glass transition point of the first layer resist.

〔Effect of the invention〕

According to the method of the present invention, in a two-layer resist process, the upper thin polymer resist is rapidly cooled after baking, thereby improving the dissolution rate of the lower resist polymer. Therefore, it is of course possible to reduce the process time.

It is possible to reduce the deterioration of fineness due to interaction with the pattern area, and furthermore, because the selection range of developing solvents is expanded, it is easy to control the profile, and the dimensions of the cylindrical density obtained in the upper layer can be maintained, and the actual etching protection is achieved. A high solution as a membrane can be expected to have good properties.

Note that the effect of improving the dissolution rate by rapid cooling treatment is obtained by baking at a temperature higher than the glass transition temperature of the polymer. has been selected.

[Embodiments of the invention]

Polymethyl isopropenyl ketone was applied to a thickness of 0.8 μm on a silicon substrate by spin coating. Subsequently, as the second step, polymethyl methacrylate was applied to a thickness of 0.3μ by spin coating, and this substrate was coated with
Baked at 0°C for 30 minutes. Next, an electron beam with an acceleration voltage of 20 KV was applied to a desired portion of this resist film at 15 μC/C.
After irradiation at an irradiation density of 100.degree. C., the upper resist layer was developed using a developer consisting of methylinobutylketone. Thereafter, this resist@substrate is baked at 120.degree. C. for 30 minutes. Immediately after baking, this resist film substrate is brought into contact with a cooling body to instantly cool it to room temperature.

Next, the sieved cyst layer was developed using a developer consisting of methyl isobutyl ketone, xylene, and ethylbenzene to complete the profile.

For comparison, a sample was prepared through the same process except that the second layer resist was exposed and cooled without being forced to cool after the post-baking.

It was confirmed that with the sample produced by the method of the present invention, a clear resist pattern was obtained with less swelling of the resist and a profile close to vertical, and with poor adhesion to the silicon substrate. Profile control was not sufficient with general methods. As can be seen from the above examples, according to the method of the present invention, it is possible to form a clear resist pattern having the above-mentioned features.

[Brief explanation of drawings]

FIG. 1 is a sectional view for explaining the present invention in detail. ]... Substrate, 2... Processed surface, 3... First pigeon cyst, 4... Second signature resist, 5... Electron beam,
Radiation such as X-rays. Representative Patent Attorney Noriyuki Chika (1 idiot) Figure 1 (α) (Me (C)

Claims (2)

[Claims] (1) In the process of forming a resist pattern on a substrate, the resist is formed into two layers, upper and lower, and after developing the upper layer resist, it is post-baked, and then cooled down to room temperature by rapid cooling, and then the lower layer resist is developed. A pattern forming method using a characteristic two-layer resist. (2) A pattern forming method using a two-layer resist according to claim 1, characterized in that the post-bake temperature of the upper resist layer is selected to be higher than the glass transition temperature of the lower resist layer.