JPS61173245A - Formation of photoresist pattern - Google Patents

Abstract

PURPOSE:To enable a micropattern good in resolution to be formed by lowering the solubility of a resist. CONSTITUTION:The resist is prepared by adding a small amt. of cross-linking agent having a sensitivity to a far UV ray in the range of 150-300nm wavelength to a positive type resist conventionally used having sensitivity to near UV rays in the range of 300-450nm wavelength. After the substrate to be processed is coated with this resist, it is uniformly irradiated with far UV rays sufficient in relative intensity prior to patternwise exposure to ordinary near UV rays to cross-link the resist. Since the solubility of the resist is reduced, and at the time of development the solubility of the unexposed parts is reduced, the film remaining proportion at the unexposed parts can be raised up to 100%. The exposed parts are also restrained in solubility, it is not dissolved by exposure with ordinary energy level, thus permitting the weakly exposed part with the diffracted light between the exposed part and the unexposed part not to be dissolved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a photoresist pattern with excellent resolution.

The degree of integration of semiconductor elements such as ICs and LSIs has been increasing more and more, and VLSI has come into practical use, and this has been achieved by miniaturizing various patterns including wiring patterns.

For example, taking an aluminum (AI) wiring pattern, the minimum pattern width is 1.7 to 1.8 μm in LSI.
1.5 is used in VLSI.
There is a tendency to use micrometers or smaller.

Here, NIIQ formation technology and photolithography are used to form fine patterns, but the theoretical limit of resolution is It is approximately 0° and 5 μm, but the practical limit of use is 1 due to light diffraction and scattering.
~2 μm, and therefore, when forming a semiconductor element with the above pattern width, a decrease in pattern accuracy is unavoidable.

- The use of short-wavelength electromagnetic waves such as rays and soft X-rays lowers the theoretical limit, making it easier to form patterns below lttm.

However, since the use of such electromagnetic waves needs to be carried out in a high vacuum and the scanning width of the beam is also small, there is a problem that the throughput (production amount) is significantly lower than that of conventional methods.

Furthermore, since exposure equipment that uses electromagnetic waves is completely different from conventional ultraviolet exposure equipment, significant changes to factory equipment are required.

For this reason, efforts are being made to form fine patterns as accurately as possible using conventional exposure equipment.

[Conventional technology]

Photoresists that are exposed to ultraviolet light undergo polymerization, decomposition, or the production of soluble substances by light irradiation, creating a difference in solubility in the developing solution and forming an image. Can negative types and light irradiated areas that are insoluble in developer be used in developer? There is a positive type that is positive.

Here, the positive type resist has a higher resolution than the negative type and is therefore suitable for forming fine patterns, but it is insufficient for a width of 1 to 2 μm as described above.

Specifically, there are problems in that the cross-sectional profile after development is not steep and the remaining film rate in unexposed areas is low.

This becomes a particular problem in the multilayer process, resulting in a decrease in yield.

In order to avoid this, various methods have been tried, such as improving the developer, improving the resist (applying additives), and improving the performance of the exposure device, but they have not yet achieved a sufficient effect.

[Problem that the invention seeks to solve]

As described above, it is difficult to form fine patterns with a pattern width of around 1 μm with high resolution using the conventional method of using ultraviolet HfAn light and positive type photoresist, and a solution to this problem was needed.

[Means for solving problems]

The above problem can be solved by making a resist by adding a crosslinking agent sensitive to far ultraviolet light to a positive resist sensitive to near ultraviolet light, and applying the resist to the substrate to be processed to form a resist film. After exposing the entire surface to deep ultraviolet light,
This problem can be solved by a method for forming a photoresist pattern, which is characterized in that the pattern is formed by selective exposure to near-ultraviolet light.

[Effect]

The present invention has been used conventionally and has a wavelength of 300 to 450 nm.
A positive type resist sensitive to near-ultraviolet light with a wavelength of 1
A resist to which a small amount of a crosslinking agent sensitive to deep ultraviolet light of 50 to 300 nm is added is used.

After this resist is coated on a substrate to be processed, the entire surface is irradiated with light containing deep ultraviolet light with sufficient relative intensity to cause crosslinking, prior to pattern exposure using normal near ultraviolet light.

As a result, the solubility of the resist is lower than before, so that the solubility of the unexposed portion during development is reduced, making it possible to increase the unexposed remaining film rate to about 100%.

Further, dissolution of the exposed areas is also suppressed due to the crosslinking effect, and the resist will not dissolve unless it is exposed to a higher energy than in the case of a normal resist.

Therefore, at the boundary between the exposed area and the unexposed area, the area weakly irradiated by the diffracted light does not dissolve.

Therefore, the pattern formed in this way exhibits a high gamma value and has a better profile than patterns obtained by conventional methods.

That is, it exhibits a high aspect ratio, the shoulder portions of the pattern are not rounded, and the pattern shape on a plane can be transferred with high fidelity.

Note that when the method of the present invention is used, the solubility of the resist is lower than that of the conventional method, so it is necessary to increase the pattern exposure time using near-ultraviolet light to some extent.

〔Example〕

A resist is prepared by adding approximately 8% of an azide compound sensitive to deep ultraviolet light, such as 4' azidobiphenyl sulfide, as a crosslinking agent to 0FPR-800, which is a positive type photoresist. A resist film having a thickness of about 1 μm was formed by spin coding at a rotation speed of about 500 rpm on a substrate coated with HMDS) using a spin code or vapor coating.

Next, after performing pre-beta at 110°C for 2 minutes, using a proximity aligner, the entire surface was exposed to far-ultraviolet light using an arc lamp with xenon (Xe) and mercury (It g ) as light sources, without using a mask. After irradiating the film for 0.2 seconds, the pattern was transferred for 1 second using a reduction projection exposure device (stepper) and an arc lamp using mercury as a light source.

The thus exposed substrate was subsequently developed using tetramethylammonium hydroxide and post-haked at 110° C. for 94 minutes to form a resist pattern.

The resist pattern thus obtained had a residual film rate in the unexposed area of almost 100% and also exhibited a high aspect ratio.

〔Effect of the invention〕

As described above, by carrying out the present invention, it has become possible to form a fine pattern with a line width of 1 to 2 μm and good resolution using a conventional photoresist.

Although the present invention is effective for forming any pattern, it is particularly applicable to the process of forming conductive holes on an interlayer insulating film, and the process of forming a pattern on a substrate exhibiting high reflectance such as aluminum (A1). It is effective to use processes such as providing aluminum wiring patterns in the second and third layers.

Claims (1)

[Claims] A resist is made by adding a cross-linking agent sensitive to deep ultraviolet light to a positive resist sensitive to near ultraviolet light, the resist is applied to a substrate to be processed to form a resist film, and deep ultraviolet light is applied to the resist film. A method for forming a photoresist pattern, which comprises exposing the entire surface to light and then selectively exposing it to near-ultraviolet light to form a pattern.