JPH0888159A - Formation of resist pattern having high aspect ratio - Google Patents

Abstract

PURPOSE: To provide a method of forming a resist pattern, which can form the positive resist pattern having a height (a depth) of 100μm or higher and a high aspect ratio easily and in a short time using quite the same device as a conventional device. CONSTITUTION: A method of forming a resist pattern comprises a step for forming a resist film 2 having a film thickness of 100μm or thicker on a substrate 1 by multiple coating of the substrate with positive resist, a step for performing a prebaking on the film 2 for solidification of the film 2 and the improvement of the adhesiveness of the film 2 to the substrate and a step for performing repeatedly a treatment pattern, which consists of an exposure and a developing, on the solidified resist film 2 a plurality of times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photolithography technique in a semiconductor fine processing technique, and more particularly to a method for forming a resist pattern having a high aspect ratio using a positive resist.

[0002]

2. Description of the Related Art In the field of semiconductor fine processing technology, a photolithography technology using a photoresist is used for forming a structure such as a circuit pattern on a substrate.

Photoresists made of a photosensitive polymer material are classified into a negative type in which a light-irradiated portion is cured and a positive type in which a light-irradiated portion is deteriorated and easily dissolved in a developing solution. A high-resolution positive resist is used for forming a so-called high aspect ratio structure pattern having a large height (depth) with respect to a planar width.

Regarding formation of a resist pattern having a high aspect ratio, "FABRICATION OF HIGH DEPTH-TO-WI" is used.
DTH ASPECT RATIO MICROSTRACTURES ", IEEE MEMS '92,
There are examples disclosed in pp.93-97.

[0005]

According to the conventional example disclosed in the above document, as shown in FIGS. 2A and 2B, the positive type resist 2 is coated on the silicon substrate 1. After that, exposure is normally performed only once through the photomask 3 (see FIG. 2A), and then development is performed only once to form the resist pattern 2a (see FIG. 2). (See (B)). For this reason, the light (ultraviolet ray) 4 does not enter the deep portion of the resist during exposure, and even if the aspect ratio is not trapped, exposure to a depth of at most 70 μm is the limit. On the other hand, when considering the aspect ratio, the depth (height) was 22 μm while the width was about 3 μm, and the aspect ratio was 7.3.

[0006] Further, it is usually formed by a single coating to about 2
In order to dissolve a resist film having a thickness of 0 μm from the surface to the bottom surface by developing after exposure,
Conventionally, it took about 10 minutes. Therefore, the thicker the resist film, the longer the development time. When the resist film is exposed to the developing solution for such a long time, the unexposed portion is also attacked by the developing solution, which has a great adverse effect on the formation of the resist pattern.

The present invention has been made to solve the above-mentioned problems in the prior art. The object of the present invention is to use a device exactly the same as the conventional one, and to have a height (depth) of 100 μm or more and a high aspect ratio. It is an object of the present invention to provide a positive resist pattern forming method capable of easily forming a resist pattern having a ratio in a short time.

[0008]

To achieve the above object, according to a main aspect of the present invention, a resist film having a film thickness of 100 μm or more is formed on a substrate by applying a positive resist multiple times. Forming a resist film, prebaking the resist film for solidification of the resist film and improving adhesion to the substrate, and repeating the treatment pattern of exposing and developing the solidified resist film a plurality of times. A method for forming a resist pattern having a high aspect ratio is provided, which comprises each step.

According to a second aspect of the present invention, in forming the resist film according to the first aspect, a predetermined amount of positive resist solution is dropped onto the upper surface of the substrate, and the resist solution is applied onto the upper surface of the substrate. Preliminarily rotate the substrate at a relatively low rotation speed for a few seconds using a spin coater so that the whole is expanded, and then use a spin coater to further increase the resist solution to a predetermined thickness. Repeat the application once, including each step of rotating the substrate at a relatively high rotation speed for a predetermined time and heating the applied resist solution at a predetermined temperature for a predetermined time to softly cure the resist solution. A method of forming a resist pattern having a high aspect ratio is provided.

The exposure intensity in the processing pattern described in the above-mentioned main embodiment is 900 millijoule / cm ² or less, and the developing time is within 2 minutes.

Further, the preliminary rotation described in the second mode is 5
The rotation is performed at 00 rpm for 5 seconds, and the main rotation is performed at 2000 rpm for 20 seconds.

Further, the heating for soft curing of the resist solution described in the second aspect is carried out at 60 ° C. for 10 minutes.

[0013]

According to the present invention, a positive resist is applied a plurality of times on a substrate until a predetermined film thickness is obtained, and then a predetermined portion of the positive resist film is removed from the surface to the bottom. The exposure and development processes are repeated a plurality of times so that a resist pattern having an aspect ratio is formed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the accompanying drawings (FIG. 1).

First, referring to FIG. 1A, as an example, a positive resist (AZ4903) manufactured by Hoechst Co. is formed on a silicon substrate 1 five times using a spin coater (spin coat or spinner) not shown. Over, and a resist film 2 having a thickness of about 100 μm was formed.
The film formation by one-time coating was performed as follows. That is, after a predetermined amount of resist solution was dropped on the upper surface of the silicon substrate 1, the resist solution was spun on the entire upper surface of the silicon substrate 1 by spinning at 500 rpm for 5 seconds with a spin coater. From the state, rotate the spin coater 2
The speed was increased to 000 rpm and held for 20 seconds. Then, the resist film 2 was slightly cured (softened) by heating at 60 ° C. for 10 minutes for the next application of the resist solution.

When the resist film 2 having a predetermined thickness (about 100 μm) is formed on the silicon substrate 1, the resist film 2 is solidified and the resist film 2 and the silicon substrate 1 are solidified.
In order to improve the adhesiveness with, the resist film 2 was prebaked by heating at a temperature of 60 ° C. for 2 hours.

Next, the resist film 2 formed on the silicon substrate 1 is irradiated with light (ultraviolet ray) 4 having an intensity of about 900 millijoules / cm ² through the photomask 3 for the first time. The exposure was done.

Subsequently, the AZ400K liquid and pure water are mixed at a ratio of 1: 4.
The resist film 2 which had been subjected to the first exposure described above was subjected to the first development treatment for 2 minutes by using the developer mixed in the above step.

A resist pattern having a height (depth) of 18.8 μm was formed by the first exposure and development processing pattern.

Further, the second, third, and fourth processing patterns under the same conditions as those of the first processing pattern are (c) and (d), (e), and (f) of FIG. Repeatedly applied as shown in g) and (h) respectively. Since the second and subsequent processing patterns are the same as the first processing pattern, their description will be omitted to avoid duplication.

By repeating the treatment pattern a total of four times, a resist pattern 2 having a height of 104.5 μm and having a groove 5 having the silicon substrate upper surface 1a as a bottom surface on both sides was formed on the silicon substrate 1. .

Table 1 below shows the processing results of the first to fourth processing patterns.

[0023]

[Table 1] The intensity of the light used for exposure is 500 millijoules / c
Even when dropped to m ² , the result was almost unchanged.

Further, the resist pattern post-baking which is performed in general semiconductor manufacturing is not performed in the present invention. This is because the resist pattern formed according to the present invention has an extremely high aspect ratio, and therefore internal stress may be generated by post-baking and the resist pattern may be cracked or broken.

Next, Table 2 shows a comparative example with respect to the embodiment of the present invention.

[0026]

[Table 2] As is clear from Table 2 above, in the comparative example, two samples A and B each having a resist film formed on a silicon substrate with a thickness of about 100 μm were exposed to light under the same conditions as in the example. A processing pattern for development was applied. As a result, a resist pattern having a height of 18.8 μm was formed in both samples.

Subsequently, the samples A and B were re-developed only without being exposed. As a result, the height of the resist pattern was 23.9 μm in Sample A, and 24.5 μm in Sample B. This indicates that the exposed resist, which was not completely removed by the first development, was removed by the second development.

Further, both the samples A and B were again subjected to the exposure and development processing pattern under the same conditions as the first time, and the height of the resist pattern was about 2 in both samples A and B.
The height increased to 0 μm to reach the height shown in Table 2.

As is clear from the above, by repeatedly applying the exposure and development treatment patterns, a resist pattern having a height of 100 μm or more, which has been impossible in the past, can be easily formed without causing any cracks. .

Further, it is usually about 2 formed by one application.
In order to dissolve a resist film having a thickness of 0 μm from the surface to the bottom surface by developing after exposure,
Conventionally, it took about 10 minutes. Therefore, 100
It takes 50 minutes to develop a resist film having a thickness of μm, even if it is simply calculated. If the resist film is exposed to the developing solution for such a long time, the unexposed portion will also be eroded by the developing solution, making it impossible to form a resist pattern, or even if it is formed, the strength will be high. The resist pattern is unusable in terms of shape and shape.

In the present invention, by repeating the exposure and development processing pattern a plurality of times, the development time for one time could be shortened to a relatively short time of 2 minutes. As a result, the time required to form a resist pattern having a height (thickness) of 100 μm or more could be significantly shortened. The above description is merely illustrative of the preferred embodiments of the present invention, and the scope of the present invention is not limited thereto. Many more variations and modifications of the present invention will readily suggest themselves to those skilled in the art without departing from the scope of the invention.

[0032]

According to the present invention, a positive resist film formed on a substrate with a film thickness of 100 μm or more is subjected to a plurality of exposure and development processing patterns, and therefore a depth of 100 μm or more is obtained. A resist pattern having a high aspect ratio can be easily formed in a short time.

[Brief description of drawings]

FIG. 1 is a process flow sequentially showing sectional views from (a) to (h) according to an embodiment of the present invention.

FIG. 2 is a process flow sequentially showing sectional views of the conventional example up to (A) and (B).

[Explanation of symbols]

 1 Silicon Substrate 1a Silicon Substrate Upper Surface 2 Resist Film 2a Resist Pattern 3 Photomask 4 Light 5 Groove

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location G03F 7/38 501 H01L 21/30 566 569 F

Claims (6)

[Claims] 1. A resist for forming a resist film having a film thickness of 100 μm or more on a substrate by applying a positive resist a plurality of times and for solidifying the resist film and improving adhesion to the substrate. A method of forming a resist pattern having a high aspect ratio, which comprises the steps of pre-baking the film and repeating a treatment pattern consisting of exposure and development on the solidified resist film a plurality of times. 2. The resist film is formed by dropping a predetermined amount of positive resist solution onto the upper surface of the substrate and using a spin coater so that the resist solution is spread over the entire upper surface of the substrate. Preliminarily rotating the substrate at a relatively low rotation speed for several seconds, and then further rotating the substrate at a relatively high rotation speed for a predetermined time using a spin coater so that the resist solution has a predetermined thickness. 2. The high aspect ratio according to claim 1, wherein one application including each step of, and heating the applied resist liquid at a predetermined temperature for a predetermined time to soften the resist solution is repeated a plurality of times. A method for forming a resist pattern having the same. 3. The exposure intensity in the processing pattern is 9
^{2. The} method for forming a resist pattern having a high aspect ratio according to claim 1, wherein the resist pattern is less than 00 millijoule / cm ² and the developing time is within 2 minutes. 4. The method of forming a resist pattern having a high aspect ratio according to claim 2, wherein the preliminary rotation is performed at 500 rpm for 5 seconds. 5. The method of forming a resist pattern having a high aspect ratio according to claim 2, wherein the main rotation is performed at 2000 rpm for 20 seconds. 6. The method for forming a resist pattern having a high aspect ratio according to claim 2, wherein heating for softening the resist solution is performed at 60 ° C. for 10 minutes.