JPS6074624A - Formation of resist film - Google Patents

Abstract

PURPOSE:To reduce the generation of striae even if a high-viscosity resist liquid is used when coating a substrate to be treated with a resist film by spin coating by performing the formation of a coating film with inverting a spin direction after a spin speed reaches the predetermined speed and the predetermined time has passed. CONSTITUTION:A motor 5 is rotated inversely in the state that a resist liquid is dripped and a substrate 1 is spinned till the predetermined speed is attained and a film thickness is determined. The motor 5 does not drive a head 3 directly, but a chuck part is connected to a spin shaft rotating at a high speed in a moment through a clutch in this constitution, so that an inverse spin of the head 3 can be done without a difficulty. Striae 8 generated with being bent in the spin direction are diminished and start to be extinguished. At the same time, dryness progresses and the film cures in the state there exists almost no stria.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method for spin-coding a high viscosity resist with reduced striae.

(b) Background of the Technology Currently, photolithography using photoresist is widely used as a method for forming fine electronic circuits on semiconductor crystal substrates and dielectric crystal substrates.

This technique involves applying photoresist onto a substrate on which a fine pattern is to be formed to form a coating film, projecting and exposing the photoresist to ultraviolet light through a photomask to partially expose the photoresist, and then developing and etching the film. A fine pattern is formed by exposing a target pattern and subjecting it to physical etching such as chemical etching or ion etching.

There are several methods for applying photoresist onto a substrate, including the spinner method, spray method, and dipping method, but the spinner method is most suitable for creating a uniform and thin coating film.

The present invention relates to a method for uniformly applying a high viscosity resist solution.

(e) Prior Art and Problems FIG. 1 is a plan view of a substrate coated with a resist film, and FIG. 2 is a sectional view of a spinner.

As previously mentioned, photo-etching technology is used in all fields as a method for forming fine butter.

The following is an example of the case where a photomask is formed on a substrate made of transparent quartz or glass.

The thickness of the substrate 1 used in this example is approximately 25 [■
], and there are various sizes, such as disc-shaped ones with a diameter of 6 [inches] or 7 [inches], and rectangular ones with a side length of 5 [inches]. A photomask consisting of a highly accurate pattern is produced by depositing chromium (Cr) to a thickness of 100 mL and etching the Cr film. That is, as shown in FIG. 2, the substrate 1 was placed on the head 3 of a spinner 2 equipped with a Makabe chuck mechanism, and the substrate 1 was attracted by a vacuum suction mechanism provided through the axis of the rotating shaft 4. A liquid resist is dropped onto the center of the rear substrate 1, and the rotating shaft is rotated at high speed by the motor 5.

The head 3 on which the substrate 1 is attracted is formed so as to be inserted into and removed from the rotating shaft 4, which has various types in proportion to the size of the substrate 1, and is fixed with screws 6. Also, the number of rotations of head 3 is approximately 1
It is configured so that it can be set arbitrarily within the range of 200 to 3000 [rpm].

Next, the resist solution is 4 to 70% depending on the type and usage conditions.
There are [cp] and various viscosities, and the resist dropped onto the center of the substrate 1 is spread evenly by the centrifugal force as the substrate rotates 10 times, and unnecessary resist is scattered to form a resist with a uniform thickness. be inspected.

The thickness of the resist required here is 5000 to 1500.
0[:A), and this thickness varies depending on the purpose of use and depends on the viscosity of the resist liquid and the rotation speed, and is expressed by the following equation.

t=KP2/rw ・・・・・・・・・・・・・・・
・・・・・・・・・・・・(1) Here t・・・・・・
Resist film thickness K...Constant W...Rotation speed P...Concentration The uniformity of the film thickness is better as the rise of the rotation of the spinner is larger.

The thinner the coating film spin-coded in this way is, the better from the viewpoint of resolution, but the thinner the coating, the more likely pinholes will occur, and the chemical resistance will be worse. When performing ion etching or the like, it is necessary that some resist remains in the pattern 1, and for this reason, a resist film that is thick enough is required.

However, when a highly viscous resist solution is used, a large number of striae 8 are produced in the resist film 7 as shown in FIG. 1, which significantly reduces pattern conflict.

In other words, striae have a pitch of less than 1 [moromi] and are 1000 (A).
The striae 8 appeared more clearly and became an obstacle to pattern formation when a resist liquid with a higher viscosity was used, and the pattern consisted of unevenness of some degree and moved outward from the center.

(d) Object of the Invention It is an object of the present invention to provide a coating film forming method in which striae are less likely to occur even though a highly viscous resist solution is used when spin-coding a substrate.

(e) Structure of the Invention The purpose of the present invention is to apply a resist film onto a substrate to be processed using a spin code method, and after the rotation speed reaches a constant speed and a set time has elapsed, the direction of rotation is reversed to form a coating film. This can be achieved by using a method.

(f) Embodiments of the Invention The present invention has been developed by focusing on the fact that resist coating by the spin code method is determined by coating conditions for the first few seconds.

That is, when forming a coating film by the spin code method,
When forming a thin coating film, based on experience, the substrate 1 should be heated for about 15 seconds.
If a thick coating film is to be produced by rotating the resist, it is common to use a high viscosity resist solution and rotating the resist for about 90 seconds.

However, as a result of experiments, it was found that the thickness of the coating film is determined within the first few seconds, and that subsequent rotation merely evaporates and dries the solvent in the coating film without forming pinholes.

Therefore, in the present invention, the resist solution is dropped, the substrate 1 is rotated, and after reaching a constant speed, for example, 5 seconds have elapsed, the motor 5 is rotated in the reverse direction with the film thickness determined. In this state, striae 8 is formed in the coating film 7, but drying has not yet begun.

In addition, in commercially available spinners, in order to improve the start-up of rotation, the motor 5 does not directly drive the head 3, but drives the head 3 at high speed (
b) Since the structure is such that the chuck part is instantly connected to the rotating shaft, the head 3 can be rotated in the opposite direction without much difficulty, and the striae 8 that was caused by curving in the direction of rotation can be reversed. It is reduced by rotation and begins to disappear, and at the same time, drying progresses and it hardens with almost no striae.

The optimal timing for reversing the head 3 depends on the viscosity of the resist liquid and the number of revolutions, but it is not constant when the head 3 is reversed.
In the example of forming a positive resist of about 5 μm]
[Seconds] was appropriate.

In this way, if the resist solution is diffused into the surrounding area by centrifugal force and reversed with a fixed film thickness, striae 8 will collapse because the formation conditions will be reversed, and the solvent will disappear without any time to form striae in the opposite direction. It evaporates and loses liquidity.

(g) Effects of the Invention The present invention has been made in order to improve the problem that when a resist film is formed by the spin code method, a large number of striae are generated and pattern accuracy is impaired due to these irregularities, and the substrate is rotated in the opposite direction. By carrying out the present invention, it is possible to almost eliminate the occurrence of striae even when using a highly viscous lens +-a.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a substrate coated with a resist film, and FIG. 2 is a sectional view of a spinner. In the figure, 1 is a substrate, 2 is a spinner, 3 is a head, and 5
is the motor, 7 is the resist film, and 8 is the striae.

Claims (1)

[Claims] A method for forming a resist film, which comprises applying a resist film onto a substrate to be processed using a spin code method, and forming a coating film by rotating the rotation direction in the opposite direction after a set time has elapsed after the rotation speed reaches a constant speed.