JPH04115523A - Flattening method of resist film - Google Patents

Abstract

PURPOSE:To enable a number of processes to be reduced by removing a thin resist film on a wide projected part and then developing utilizing difference of eluation speed to a developing liquid so that the resist film remains within a narrow recessed part. CONSTITUTION:A photoresist 12 is rotationally coated on a substrate 11 with recessed and projected stage differences by a same film thickness as a wide recessed part stage difference and this photoresist 12 is exposed by using a photo mask 13. At this time, a wide recessed part on the substrate 11 becomes a non-exposed part and a resist pattern 14 with a film thickness which is as high as the recessed part stage difference is formed when performing development. This development is performed by controlling development conditions so that eluation speed to a development liquid of the resist film within a narrow recessed part becomes smaller than that to a development liquid of the resist film on a wide projecting part, the resist film onto a wide projected part is eliminated, and then a resist film 15 is left within a narrow recessed part. After this, a resist film 16 is formed, thus enabling the number of processed to be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for planarizing resist III for forming a flat resist *M on a substrate having uneven steps.

(Prior Art) As circuits become more highly integrated, technical requirements regarding fine pattern formation are becoming increasingly strict.

If the substrate surface has uneven steps, the steps may cause disconnections or short circuits in the conductor layer, and when forming fine resist patterns by exposure, insufficient focus margin may be secured, resulting in poor resolution, etc. to occur.

In order to solve these problems and form fine patterns, technical improvements in planarization that eliminate unevenness and steps on the surface of a substrate are currently being actively pursued in eleven different fields.

Conventionally, as a method for forming a flat resist film, for example, there is a method disclosed in Japanese Patent Application Laid-open No. 74723/1983.
FIG. 2 is a sectional view of the process.

In the substrate 1 having uneven steps as shown in FIG. 2(A), a resist pattern 2 is formed in the wide recess 1a as shown in FIG. 2(B), and the width of the wide recess 1a is adjusted to a desired width. Under the width board.

Next, as shown in FIG. 2(C), after forming the first resist thin film 3, the first resist thin film 3 protruding onto the substrate 1 as shown in FIG. 2(D) is removed by etching back. Remove everything. Etch back the first resist thin film 3,
At the stage shown in FIG. 2(D), the level difference on the surface has been reduced, and a resist film 4 as a second resist thin film is further formed on this, resulting in the state shown in FIG. 2(E). Forms a very flat and uniform resist film.

(Problems to be Solved by the Invention) However, the method for forming a flat resist thin film described above has the following problems: requires a first step of exposure and a second step of development.

(2) Resist pattern 2 formed in this way
A third step is required in which a first resist thin film 3 is formed by coating on the substrate 1 on which the resist film 3 is formed.

(3) A fourth process of etching back and removing the first resist thin film 3 formed as described above and a notching process.
It requires a process.

(4) This etched back first resist thin film 3
A fifth coating step is required to form a resist film 4 serving as a second resist thin film thereon.

As the number of steps increases, there is a problem in terms of throughput.

The present invention provides a method for planarizing a resist film that solves the problems of the prior art, including the large number of steps and poor throughput.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a method for flattening a resist film, in which a resist pattern is formed in a wide recess on a substrate by exposure and development, and the development process is performed at the same time. Sometimes, the resist thin film remains in the narrow recesses by taking advantage of the difference between the elution speed of the resist thin film on the wide convex parts into the developer and the elution speed of the resist thin film on the narrow recesses into the developer. This is the introduction of the process.

According to this invention, in the method for flattening a resist film,
By introducing the process described above, a resist pattern is formed in the wide concave portions on the substrate by exposure and development, and at the same time, during this development, the dissolution rate of the resist ()ff film on the wide convex portions into the developer is faster than that in the developing solution. Since the elution rate of the thin resist film in the narrow concave portions into the developer is faster, the thin resist film on the wide convex portions is removed first, leaving the thin resist film in the narrow concave portions, thus solving the problem described above. Points can be removed.

(Example) Hereinafter, an example of the method for flattening a resist film of the present invention will be described based on the drawings. FIG. 1(A) to FIG. 1(C) are process cross-sectional views of one embodiment.

First, as shown in FIG. 1(A), a photoresist 12, for example, a positive novolak photoresist HPR-204 (manufactured by Fuji Hunt Co., Ltd.) is placed on a substrate 11 having uneven steps at the same height as the wide recessed steps. Rotate the coating to a film thickness of
This photoresist 12 is exposed using a photomask 13.

At this time, the wide recesses on the substrate 11 become unexposed parts, and during development, a resist pattern 14 having the same height as the step height of the recesses is formed as shown in FIG. 1(B).

This development is performed using a TMAH aqueous solution, which is an organic alkaline aqueous solution, but the elution rate of the resist film in the narrow concave portions into the developer is smaller than the elution rate of the resist film on the wide convex portions into the developer. By controlling the development conditions, it is possible to remove the resist film on the wide convex portions and leave the resist film 15 in the narrow concave portions.

That is, by increasing the difference in elution rate into the developer between the resist in the narrow concave portion and the resist on the wide convex portion, the resist can be selectively left in the narrow concave portion.

As for such development conditions, it is effective to use a developer with a dilute concentration such that the elution of the resist becomes the diffusion rate-determining rate of the developer, and the TMAHI degree is 0.1.
About 1% is particularly effective.

Further, as the developing method, a static dip method is optimal in which the developing solution is not stirred so as to increase the difference in elution rate.

(Effects of the Invention) As described above in detail, according to the present invention, a resist pattern is formed in a wide concave portion on a substrate by exposure and development, and at the same time, during this development, a thin resist film on a wide convex portion is removed. In addition, the development takes advantage of the difference in the rate of elution into the developer so that the resist film remains in the narrow recesses, so an excellent flat resist film can be obtained even with a reduced number of steps. It can be expected to have the effect of being able to form.

[Brief explanation of drawings]

FIG. 1(It) to FIG. 1(C) are process cross-sectional views of an embodiment of the resist film planarization method of the present invention, and FIG.
8) to 2(E) are process cross-sectional views of a conventional method for forming a flat resist film. DESCRIPTION OF SYMBOLS 11... Base plate, 12... Resist, 13... Photomask, 14... Resist pattern, 15...
Resist film, 16... Organic resist film. Figure 1 of the process diagram of the present invention Figure 2 of the conventional process diagram

Claims (1)

[Scope of Claims] (a) A resist pattern is formed in the wide concave portions of the substrate by exposure and development, and at the same time, during this development, the resist thin film on the wide convex portions of the substrate is removed, and (b) After the above development, apply an organic resist film to a desired thickness so that a thin resist film remains in the narrow recesses of the substrate using the difference in elution rate to the developer. A method for flattening a resist film, comprising: a step of forming a flat resist thin film; and a method for flattening a resist film.