JPH02183256A - Pattern forming method - Google Patents

Abstract

PURPOSE:To obtain the pattern which is excellent in definition and dry etching resistance after curing by specifying the irradiation quantity of UV rays used for exposing the pattern on a resist layer at the time of forming the pattern applying a crosslinking agent-contg. positive type photoresist on a substrate to be treated. CONSTITUTION:The crosslinking agent-contg. novolak type positive resist is applied on a GaAs wafer 1 having the film to be worked to form the resist layer 2 and thereafter, the layer is subjected to soft baking in the atm. The resist layer 2 is then irradiated with g rays (436nm wavelength) 3 thereon at 1,000 to 2,000mJ/cm<2> irradiation quantity according to the desired pattern. The resist layer is subjected to the baking in the atm. after the exposing of the pattern to thermally crosslink the exposed part 4 of the resist; thereafter, the entire surface of the resist is irradiated with far UV rays 6 so that the unexposed part 5 formed after the pattern exposing is made soluble in a developing soln. Finally, the substrate 1 is developed to dissolve away the unexposed part 5 in the pattern exposing. The resist pattern having the excellent definition and the dry etching resistance after curing is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention] (Industrial Field of Application) The present invention relates to a pattern forming method by an image reverse method using a positive photoresist containing a crosslinking agent.

(Prior Art) Today, as LSIs become more highly integrated and faster, there is a demand for improved performance of elements such as FETs. For this purpose, microfabrication techniques such as shortening the gate length are essential techniques. In order to carry out such fine processing, a technique for forming fine patterns on a substrate is required, and the image reversing method is known as one of the methods. The image reverse method has conventionally been mainly used in the lift-off method for forming metal wiring and the like. However, since the resolution can be improved by increasing the development contrast, it is considered to be advantageous for other microfabrication as well.

In the image reversal method, a layer of positive photoresist containing a crosslinking agent is first formed on a substrate, a pattern is exposed on this resist layer using ultraviolet rays, and then the exposed portions of the resist are thermally crosslinked by baking. A resist pattern is formed by exposing the entire surface of the resist layer to deep ultraviolet rays and then developing it. In this method, the exposed portions of the resist are crosslinked through initial pattern exposure using ultraviolet rays and subsequent baking, and this portion functions as a mask that blocks the deep ultraviolet rays that are then applied to the entire surface of the resist. By irradiating with deep ultraviolet rays after baking, the resist other than the portions exposed to the ultraviolet rays becomes soluble in a developer and is removed by development. Therefore, the resist that ultimately remains on the substrate is the portion that was first exposed to ultraviolet light, resulting in a negative pattern even though a positive resist is used.

(Problems to be Solved by the Invention) However, in the conventional image reverse method, pattern exposure using ultraviolet rays is performed with an irradiation dose of 500 a+J/c+n2 or less. For this reason, the degree of crosslinking in the exposed portion of the resist decreases, causing deterioration in resolution such as thinning of the pattern due to film thinning during development, and deterioration in dry etching resistance.

An object of the present invention is to provide a method for forming a resist pattern with excellent resolution and dry etching resistance after curing.

[Structure of the Invention] (Means for Solving the Problems) In view of the above-mentioned problems, the present invention includes the steps of: coating a positive photoresist containing a crosslinking agent on a substrate to be processed to form a resist layer on the substrate; , a step of exposing a desired pattern on a resist layer formed on a substrate using ultraviolet rays; a step of baking the resist layer with the pattern exposed using ultraviolet rays to thermally crosslink the resist portions exposed to ultraviolet rays; In a pattern forming method that includes a step of irradiating the entire surface of a baked resist layer with deep ultraviolet rays and a step of developing the resist layer irradiated with far ultraviolet rays, the amount of irradiation of ultraviolet rays used to expose a pattern on the resist layer is controlled. 1000
The present invention provides a pattern forming method characterized in that the patterning pattern is 2000IIIJ/c+n2.

(Function) In the image reverse method, first, a pattern is exposed on a resist using ultraviolet rays, and then the exposed resist is baked to thermally crosslink the exposed portions of the resist. Next, the entire surface of the resist is irradiated with deep ultraviolet rays to solubilize parts of the resist other than the crosslinked portions in the developer solution. In this case, the greater the amount of ultraviolet ray irradiation during pattern exposure, the greater the degree of crosslinking of the resist, and the greater the degree of crosslinking of the resist, the more pronounced the insolubility in the developer becomes. Therefore, in the image reverse method, by increasing the irradiation amount during pattern exposure, the difference in dissolution rate during development between the exposed area by pattern exposure and a certain exposed area becomes large, and the development contrast can be increased.

In the pattern forming method of the present invention, the irradiation amount during pattern exposure is 1000 to 2000 aJ/cm2, which means that the exposed areas of the resist by pattern exposure are sufficiently crosslinked and the residual film rate after development is 100. % or more. Therefore, in the pattern forming method of the present invention, there is no film loss due to development.

Furthermore, as described above, the exposed portions of the resist through pattern exposure are sufficiently crosslinked, so that dry etching resistance is improved.

(Example) Hereinafter, the method of the present invention will be specifically explained with reference to the drawings.

First, as shown in FIG. 1(a), AZ5214 (Hoechst Japan Co., Ltd.), which is a novolac positive type resist containing a crosslinking agent, is placed on a GaAs wafer 1 having a film to be processed (for example, SiO'2), which is a substrate to be processed. Co., Ltd.) to form a resist layer 2 having a thickness of 1.5 .mu.m.

After forming the resist layer 2, soft baking is performed at 90° C. for about 2 minutes in the air.

Next, as shown in FIG. 1(b), using an exposure device,
According to the desired pattern, irradiation amount of G-line (wavelength 438rv) 3 is 20 0IIJ/cI11 on the resist layer 2.
Irradiate with 2.

After exposing the pattern, baking is performed in the atmosphere at 115° C. for about 1 minute and 30 seconds to thermally crosslink the exposed portions 4 of the resist as shown in FIG. 1(C).

After baking, as shown in FIG. 1(d), the entire surface of the resist is irradiated with deep ultraviolet rays 6 having a wavelength of 290 rv for about 1 minute.

As a result, the unexposed portion 5 during pattern exposure becomes soluble in the developer.

Finally, the resist is developed by immersing the substrate 1 in a 50% diluted resist special developer for 1 minute at room temperature, and the unexposed portions 5 in the pattern exposure are dissolved and removed.

By washing this and further drying it, as shown in Figure 1 (
A substrate formed with a pattern as shown in e) can be obtained.

The inventors' experiments have confirmed that in order to form a resist pattern with better dry etching resistance, the following points should be taken into consideration.

In the pattern forming method of the present invention, ultraviolet rays are used when exposing a resist layer formed on a substrate to a pattern. The ultraviolet rays referred to here include light including so-called g-line having a wavelength of 438 ni.

The ultraviolet rays used in the pattern forming method of the present invention are preferably the above-mentioned g-line or the so-called i-line having a wavelength of 385 nn+, and the g-line is particularly preferable.

The irradiation amount of the ultraviolet rays when exposing the pattern on the resist layer is 1000 to 2000 IIlj/cI112, preferably 1500 to 2000 mJ/cm.
It is 2.

Heating to crosslink the exposed portions of the resist irradiated with ultraviolet rays varies depending on the resist used, but when a novolac positive resist is used, it is usually carried out at 115 to 120° C. for 1 to 2 minutes.

After baking the resist layer, the entire surface of the resist layer is irradiated with deep ultraviolet rays. The far ultraviolet rays referred to here have a wavelength of 290 tv.
In particular, light with a wavelength of 290 ns is preferable.

As a method for applying a crosslinking agent-containing positive photoresist onto a substrate to be processed, a method normally used for forming a resist layer on a substrate can be used, and for example, spin coating etc. can be preferably used. can.

The crosslinking agent-containing positive photoresist used here is sensitive to ultraviolet rays and deep ultraviolet rays at the wavelengths used in the pattern forming method of the present invention, and contains a crosslinking agent that crosslinks the portions exposed to ultraviolet rays by baking. Any resist can be used as long as it contains the resist.

As such a photoresist, a crosslinking agent-containing novolac positive resist is known.

After coating the photoresist on the substrate to form a resist layer, it is preferable to bake the resist layer for the purpose of removing the solvent remaining in the resist layer and/or improving the contact between the substrate and the resist layer. .

[Effects of the Invention] As described above, according to the present invention, a method for forming a resist pattern with excellent resolution and dry etching resistance after curing is provided.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the invention in detail. 1... Substrate to be processed, 2... Resist layer, 4... Exposed portion, 5... Unexposed portion. Applicant's agent Patent attorney Takehiko Suzue

Claims (4)

[Claims] (1) A step of coating a positive photoresist containing a crosslinking agent on the substrate to be processed to form a resist layer on the substrate, and a step of exposing the resist layer formed on the substrate to a desired pattern using ultraviolet light. , a step of baking a resist layer with a pattern exposed to ultraviolet rays and thermally crosslinking the resist portion exposed to ultraviolet rays, a step of irradiating the entire surface of the baked resist layer with deep ultraviolet rays, and a step of irradiating the resist layer with deep ultraviolet rays. In the pattern forming method, the amount of ultraviolet rays used to expose the pattern on the resist layer is 1000.
A method for forming a pattern, characterized in that the current is between 2000 mJ/cm^2 and 2000 mJ/cm^2. (2) The wavelength of the ultraviolet rays is 365 nm or 436 nm.
The pattern forming method according to claim 1, wherein m. (3) The pattern forming method according to claim 2, wherein the substrate is a semiconductor substrate. (4) The pattern forming method according to claim 2, wherein the wavelength of the ultraviolet rays is 436 nm, the irradiation amount is 1500 to 2000 mJ/cm^2, and the wavelength of the deep ultraviolet rays is 290 nm.