JPS6350020A - Formation of pattern - Google Patents

Abstract

PURPOSE:To form a uniform resist film by crosslinking an Si resin and applying a solvent, into which the Si resin is difficult to be dissolved, onto the Si resin before a resist is applied. CONSTITUTION:An Si resin 3 is applied onto a substrate 1 on which a wiring metal 2 is shaped. A polar solvent into which the Si resin is difficult to be dissolved is applied onto the resin 3. The upper section of the solvent is irradiated with ultraviolet rays or X-rays or coated with an electron ray resist 4. Since the polar solvent is diffused previously to the inside, the polar solvent is difficult to be diffused into the resin 3. Consequently, the solvent is hardly dissolved, and the resist 4 can be applied in uniform film thickness. The resist is irradiated with ultraviolet rays, X-rays or electron rays by using a desired mask or data, and developed, thus forming the pattern of the resist 4. According to said pattern forming method, the fine pattern can be shaped excellently.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pattern forming method used in the manufacture of various solid-state devices including integrated circuits.

(Prior Art and Problems to be Solved by the Invention) Integrated circuits are becoming larger and more highly integrated year by year, and new circuit manufacturing techniques and materials are being researched and developed one after another. Organopolysiloxane represented by the following general formula,
Silicone resin is also attracting attention as a new material for LSI.

? (R is an organic group such as methyl or phenyl) The most important feature of silicone resin is that it has a polymeric form that can be spin-coated, but it is different from ordinary organic polymers that have carbon atoms in the main chain. It exhibits excellent insulation, heat resistance, and oxidation resistance (oxygen glazma resistance). Therefore, LSI can be used as an insulating film whose surface is flattened, and as a material for multilayer resists such as the intermediate layer of three-layered (r9) cysts.
It has been widely applied in production. Taking a silicone resin insulating film as an example, the formation process will be explained. As shown in FIG. (b). The spin coating method involves the steps of resin dropping, spin rotation, and baking, similar to the formation of a normal resist film. The amount of dripping is usually 2 to 5 cc to cover the entire surface of the substrate, and the number of spin rotations and rotation time are such that the required film thickness can be formed, which is usually 10 to 5 cc.
00 to 4000 rpm, 10 to 30 seconds, baking should be done only to the extent that the solvent in which the resist was dissolved evaporates.
Usually 100-200°0. Next, as shown in +41), ultraviolet rays are applied to form a pattern on the silicone resin 3.
An X-ray or electron beam resist 4 is applied with a strip of paint. A pattern of the resist 4 is formed by irradiating ultraviolet rays, X-rays, or electron beams using a desired mask or data and developing with an arbitrary solvent (d). Subsequently, using the formed pattern of the resist 4 as a mask, the silicone resin 3 is dry-etched using gas plasma such as CF4, and further, the /-tan on the resist 4 is removed (,).

After this, for example, a second layer of wiring metal 5 is formed (f).

When such a silicone resin is used as an insulating film, the surface of the silicone resin is flattened, so as shown in FIG. 7 will disappear. Also, 5102
The insulating film is formed by splattering in a vacuum apparatus, whereas the silicone resin is formed by spin coating, so the formation time can be significantly shortened.

As described above, silicone resin insulating film has various advantages and is an effective material for the multilayer metal wiring process that is essential for VLSI, but when a resist is applied on silicone resin, it is difficult to heat the silicone resin to Unless cross-linked sufficiently, the resist coated on the silicone resin will dissolve the silicone resin, as shown in Figure 3, due to the solubility of the resist in the solvent (for example, Tokyo Ohka Photoresist 0FPR-800, the solvent is ethyl cellosolve acetate). In addition to forming the mixed layer 8, a problem arises in that the resist film thickness becomes uneven.

As a result, there was a problem in that it was not possible to form a good resist arm tongue as shown in FIG. 1d or a good silicone resin arm tongue as shown in e. On the other hand, when heated at high temperatures, there is a problem in that the silicone resin film cracks.

On the other hand, even when silicone resin is used as the intermediate layer of a three-layer resist, the three-layer film can be formed continuously by spin coating, which has the advantage of simplifying the formation process. Since the resist to be exposed to light is formed on the silicone resin, the problem arises that the resist cannot be formed satisfactorily on the silicone resin in the case of a three-layer resist as well as when used as an insulating film.

(Means for Solving the Problems) The present invention was proposed in order to solve the above-mentioned drawback that a resist cannot be formed on silicone resin. The purpose of the present invention is to provide a four-layer or three-layer resist film layer.

In order to achieve the above object, the present invention comprises a step of forming a silicone resin on a substrate to be processed, a step of applying a polar solvent in which the silicone resin is poorly soluble onto the silicone resin, and a step of applying the polar solvent to the silicone resin. The gist of the invention is a pattern forming method characterized by including a step of applying a resist sensitive to ultraviolet rays, X-rays, or electron beams on the applied silicone resin.

In order to lower the solubility of a silicone resin in a solvent, it is necessary to crosslink the silicone resin with heat or a crosslinking agent to increase its molecular weight.

However, excessive crosslinking causes volumetric shrinkage and causes cracking of the membrane. Although a small amount of crosslinking slightly reduces solubility, resist film unevenness during resist coating cannot be avoided. Even slight film unevenness has a large effect on fine 9-turn formation. The present invention is characterized by forming a uniform resist film with slight crosslinking. Specifically, after the silicone resin is slightly crosslinked, a solvent in which the silicone resin is hardly soluble is applied before applying the Resist. This solvent is usually applied by spin coating, but other methods may also be used. By spin coating, the solvent permeates the surface of the silicone resin and only the diffused solvent remains. The solvent in the silicone resin is generated as the solvent diffuses into the resin. Therefore, by simply suppressing the diffusion of the solvent into the resin,
The rate of dissolution can be reduced. The solvent coating before resist coating is aimed at suppressing diffusion. That is, if a solvent (A) in which silicone resin is poorly soluble is applied onto the resin before resist application, this solvent (A) will diffuse into the resin. In this state, even if a resist containing a resin-soluble solvent (B) such as ethyl cellosolve acetate is applied, the solvent (B) will not diffuse because the solvent (A) has already been diffused inside. <Vru. As a result, the resist can be coated with a uniform thickness with almost no dissolution. The solvent (A) to be used may be any solvent as long as it does not easily dissolve the silicone resin, but since most photoresist solvents are polar solvents, the above-mentioned solvents may be used from the viewpoint of mutual competition and compatibility. The solvent (A) is preferably a polar solvent. Furthermore, alcohols such as methanol and ethanol, which are particularly difficult to dissolve polymers, ketones such as methyl isobutyl ketone and methyl ethyl ketone, or mixtures thereof are preferable.

Furthermore, although the above description has been made regarding the case where the silicone resin is slightly crosslinked, the present invention does not require "slight crosslinking" if a solvent in which the silicone resin is poorly soluble can be applied without crosslinking.

The present invention will be described in detail below according to examples.

It should be noted that the embodiments are merely illustrative, and it goes without saying that modifications and improvements may be made without departing from the spirit of the present invention.

(Example 1) A 2 μm thick silicone resin made of methylvinyl polysiloxane was spin-coated on a silicon substrate having an i9 tan made of molybdenum, and the thickness was 150°0.20 during opening.
It was heated for a minute. After this, 5 cc of methanol was added dropwise, and 3
Spin at 00 rpm for 75 seconds + 300 rpm for 720 seconds. Next, photoresist 0FPR-80 manufactured by Tokyo Ohka Co., Ltd.
0 was formed to a thickness of 0.1 μm, and 0FPR-800 was exposed by reduction projection using a desired mask i4 tan with 436 nm ultraviolet light. After developing with alkaline developer, CF
Using 4 gas plasma, 0.3W/C! ll, CF
The silicone resin was etched at 450 sec under a pressure of 100 Pa using the resist pattern as a mask.

As a result, a good insulating film pattern was obtained.

(Example 2) After forming a silicone resin with a thickness of 2 μm in the same manner as in Example 1 on a silicon substrate having an aluminum thin film pattern, 5ea of methyl isobutyl ketone was dropped, and then spin was performed under the same conditions as in Example 1. Next, a 1 μm thick photoresist 0FPR-800 manufactured by Tokyo Ohka Chemical Co., Ltd. was formed, and the OFPR-800 was exposed and developed in the same manner as in Example 1 to form a resist pattern with a diameter of 1 μm. Using CF4 gas plasma, 0.3W/C1/l, CF450 sec,
0.5 μ under Zoo Pa undercut conditions
After etching the thickness of m, reduce the pressure to 50P and remove the remaining silicone resin by 1.5cm under the condition that no undercut occurs.
μm etched. As a result, a good insulating film pattern with a diameter of 1 μm and a tapered upper part was obtained.

(Example 3) A 2 μm thick photoresist 0FPR-800 manufactured by Tokyo Ohka Co., Ltd. was coated on a silicon substrate on which a 0.5 μm thick aluminum thin film was deposited, and after heating at 240° C. for 30 minutes, silicone made of methylpolyroxane was coated. The resin was applied to a thickness of 0.2 μm and heated at 240° C. for 30 minutes.

Next, 5 cc of methanol was added dropwise, followed by spinning in the same manner as in Example 1. After this, photoresist 0FPR made by Tokyo Ohka Co., Ltd.
-800 was applied to a thickness of 1 .mu.m, and a wiring pattern with a width of 0.8 .mu.m was formed by reduction projection exposure and development with 365 nm ultraviolet rays. Under the conditions of 0.3 W/cI/l and I Pa, the silicone resin was heated with a gas mixture of CF4 and 20% H2, and the 2 μm J'lE below it was heated with oxygen gas.
0FPR-800 was plasma etched. Using this three-layer resist pattern as a mask, apply BClS to an aluminum thin film.
and CCt4 mixed gas plasma,
A good mother tongue with a width of 0.8 μm was obtained.

(Effects of the Invention) As explained above, according to the present invention, it is possible to solve the problems that occurred when a resist was formed on a silicone resin. As a result, there is no uneven coating on the resist.
It shows the effect that fine patterns can be formed well and that a good insulating film for multilayer wiring or a multilayer resist can be formed.

[Brief explanation of drawings]

Figure 1 a''=f is a cross-sectional view showing the process of forming a silicone resin insulating film, and Figure 2 is a cross-sectional view when an SlO□ insulating film is used instead of silicone resin. 3
The figure shows that the resist dissolves the silicone resin to form a mixed layer. DESCRIPTION OF SYMBOLS 1... Board, 2... Wiring metal, 3... Silicone resin, 4... Resist, 5... Wiring metal, 6...
5IO2 insulating film, 7... Disconnected portion, 8... Mixed layer. Figure 1/Knee: No-゛1] Q') 2 Figure 2 □ Figure 3

Claims (2)

[Claims] (1) A step of forming a silicone resin on the substrate to be processed, a step of applying a polar solvent in which the silicone resin is poorly soluble onto the silicone resin, and a step of applying ultraviolet rays to the silicone resin coated with the polar solvent. A pattern forming method comprising the step of applying a resist sensitive to X-rays or electron beams. (2) The pattern forming method according to claim 1, wherein the polar solvent is an alcohol.