JPS6169130A - Pattern forming process - Google Patents

Abstract

PURPOSE:To form a fine pattern stably with accurate dimension in a simple process by a method wherein, when positive type photoresists are laminated, xylene solution containing cyclopolyisoplene is utilized as an intermediate layer. CONSTITUTION:A substrate 1 to be processed is coated with a positive type photoresist 2 utilizing normal type photoresist containing naphthoxynondiazide as sensitive radical and phenolic resin as resin for baking process. Next the positive type photoresist 2 is coated with xylene solution containing cyclic polyisoplene 3 for baking process and then further coated with a positive type photoresist 4 with concentration of sensitive radical increased up to 50% for further baking process to be irradiated with exposing light 5. Then the resist 4 is removed by immersing it in ethylcellusorpacetate solution and then the intermediate layer 3 is removed by immersing it in xylene solution while the resist 2 is developed by immersing it in choline solution to pattern the resist 2. Through these procedures, an image may be drawn with high contrast utilizing the resist 4 as a fading film.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a pattern forming method suitable for microfabrication,
More specifically, the present invention relates to a pattern forming method for forming a fine pattern with stable dimensional accuracy of 1' using a simple method.

[Technical background of the invention and its drawbacks]

The density of integrated circuits has quadrupled every two to three years, and along with this, the dimensions required for microfabrication of devices have become increasingly finer, and dimensional accuracy has also become stricter. A control is requested. In response to these demands,
The development of a butter/forming technology that enables the formation of fine patterns and maintains a dimension of 417 degrees even with process variations is progressing aggressively, not only due to the exposure equipment, but also from the perspective of the resist materials used. There is.

By the way, one of the factors that limits the resolution required for forming fine patterns is diffraction development based on the wave nature of light beams (particles 1). The diffraction principle is (important light rays (particle beams)
This shows that the resolution of the exposure system increases as the wavelength becomes shorter. However, far ultraviolet rays (wavelength 200~
iλ light technology using 300nm), X-rays, and electron beams requires expensive equipment and has problems with mass production. Used for mask pattern formation.

On the other hand, ultraviolet exposure technology (wavelength 3
00 to 4 sonm) can be applied, the conventional technology can be used as is, which is extremely advantageous in terms of mass production and economy.

1'. Therefore, several attempts have been made to improve ultraviolet exposure technology for forming fine patterns. Improvements.

One method is to use the projection optical system, and the other method is on the resist side. B, F., and Griffin et al. have proposed providing a photobleachable coating on the positive resist film (IEEE, EIectron Device L).
etters, vol, EDL-4, (In2(19
83)).

This method consists in changing the illuminance distribution of the pattern by passing it through a photobleaching film, thereby improving the optical contrast with the resist. That is, the amount of color fading is small in shadow areas where the amount of light is relatively small, while the amount of color fading is large in highlight areas. Therefore, the transmitted light rays in the highlight part become relatively stronger compared to the shadow part, and the optical contrast with respect to the resist film is apparently improved. In order to effectively carry out this method of improving optical contrast, the fading substance must satisfy the following conditions.

■The light that exposes the resist must be sufficiently absorbed and the color can fade;■The fading speed should be close to the photosensitivity of the resist;■
After fading, the material changes to a fully transparent material.

As a result of conducting a rigorous computer simulation and investigating, it was found that the above condition (■) is the most important condition among these. On the other hand, it is known that positive photoresists using 7-toquinonediazide as a photosensitive group have photobleaching properties. That is, it has become clear that it is desirable to use the same positive photoresist as the resist photobleachable coating. Furthermore, when we prototyped and investigated a primary photobleaching film other than positive-type photoresist, we found that it was difficult to put it into practical use due to optical scattering, gas generation in U light, uneven coating, etc. It was found that the type photoresist does not have such an optical gap and is most preferable as a photobleaching pattern.

On the other hand, when using a 1-layer positive photoresist f, since both are in the same solvent, they naturally mix and cannot be distributed in the two layers.

Furthermore, the optical density was insufficient due to photobleaching, and there was a problem that a sufficient effect of increasing contrast could not be found.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pattern forming method that eliminates the above-mentioned complications and can stably obtain fine patterns with high precision in all dimensions using a simple method.

[Summary of the invention]

The inventor has discovered that it is possible to provide a xylene solution of cyclized polyisoprene as an intermediate layer when laminating positive photoresists, and that these can be sequentially removed by dissolution and patterning is possible. . In addition, we have found that by increasing the concentration of naphthoquinone diazide contained in the positive photoresist of the photobleaching film, sufficient initial optical density and photobleaching properties can be achieved.
The gist of the present invention is to form a positive photoresist f! by using an intermediate layer. : A layer is formed, and the upper layer of positive resist is used as a photobleaching film to obtain a high contrast image.

〔Effect of the invention〕

According to the present invention, it has an extremely excellent effect of being able to form fine patterns of 1 μm or less with high dimensional accuracy and stability in a simple manner while utilizing the conventional ultraviolet irradiation technology, and its industrial effects. is large.

[Embodiments of the invention]

Hereinafter, the invention will be described in detail based on examples.

As shown in Figure 1 fa), a normal positive photoresist (trade name, Tokyo Ohkasha 20FPR
800, Hoechst: Az (350J.

Hunt Co., Ltd.: HPR118, etc.) 2 was spin-coated to a thickness of 1 μm, and baked at 90° C. for 10 minutes. Next, the first
As shown in Figure (b), a xylene solution of cyclized polyisoprene, Kanto Kagaku Co., Ltd. KOC-23 (trade name) e, was spin-coated to a thickness of 0.2 μm, and baked for 90'010 minutes. Then, as shown in FIG. 1(C), a positive photoresist with a concentration of 50% of the photosensitive group, 7-toquinone diazide, was spin-coated to a thickness of 5 μm, and heated at 90°C for 10 minutes.
I did a minute of baking. Then, 5t of exposure light was applied. Next, as shown in FIG. 1(d), the positive photoresist 41 was removed by immersion in a % ethyl cellosolve acetate solution for 10 seconds. Furthermore, as shown in Figure 1(e), the intermediate layer 3 was removed by immersion in a xylene solution for 5 seconds, and the resist 2 was developed by immersion in a choline solution for 1 minute as shown in Figure 1(e). I made a deep turn.

[Brief explanation of drawings]

FIG. 1 is a process sectional view showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Photoresist layer, 3...
...Intermediate layer, 4...Photobleachable film, 5...Exposure light.

Claims (4)

[Claims] (1) Applying a first photoresist coating onto the substrate, forming a second coating on the photoresist, and forming a third photobleachable coating on the second coating. a step of simultaneously exposing the first and third films to pattern light; a step of sequentially removing the third and second films; and a step of developing and patterning the first photoresist film. A pattern forming method comprising: (2) The first photoresist film and the third photobleachable film,
2. The pattern forming method according to claim 1, wherein a normal positive photoresist using naphthoquinonediazide as a photosensitive group and a phenol resin as a resin is used. (3) The pattern forming method according to claim 1, characterized in that a xylene solution of cyclized polyisoprene is used for the second coating. (4) The pattern forming method according to claim 1, characterized in that the concentration of photosensitive groups in the positive photoresist of the third film is made higher than the concentration in the first positive photoresist.