JPH0529197A - Method of forming resist pattern - Google Patents

Abstract

PURPOSE:To form a fine resist pattern by forming an uneven part on a surface of a resist, so forming a step of the resist surface that a phase of an exposure light wavelength is just deviated by a special wavelength, then exposing the entire surface with a parallel light ray by an exposure unit and developing it. CONSTITUTION:A desired base board 1 is coated with positive type photoresist 2, and a desired pattern is transferred from a mask 20 by a contraction exposure unit, etc. It is developed to form a step on the surface of the resist. Then, the entire surface is exposed with a parallel light ray having a wavelength lambda. In this case, the step of the resist surface is so set that the phase of the exposure wavelength is just deviated by 1/2 wavelength. Then, when it is developed, the resist so remains as to be disposed along a line of the step of the resist surface, and a very fine line pattern can be formed. Thus, a patterning of a finer width or space than the wavelength at the time of entire surface exposure, i.e., the wavelength of a single wavelength parallel beam which can be formed, can be performed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for forming a resist pattern using photolithography.

[0002]

2. Description of the Related Art A conventional photolithography process is shown below. As shown in FIG. 4A, for example, a positive photoresist 2 is applied on a desired base, and a desired pattern on the mask 30 is exposed by a reduction exposure device or the like. Next, by developing, a resist pattern as shown in FIG. 4B can be obtained. A semiconductor device is manufactured by using the photoresist pattern as a mask and performing an implantation process, an etching process, or the like.

[0003]

In order to resolve a narrower line width, an exposure machine with a higher NA (large numerical aperture) must be used, and the line width of the exposure wavelength level pitch is resolved. I couldn't.

[0004]

[Means for Solving the Problem] Asperity is formed on a resist surface portion. At this time, the step of the resist surface is set so that the phase of the exposure wavelength is shifted by exactly 1/2 wavelength. afterwards,
A parallel light beam was exposed on the entire surface with an exposure machine and developed.

[0005]

When manufactured as described above, the phase at the time of exposure changes between the convex portion and the concave portion. Therefore, light having different phases interferes with each other at the step portion, and light is not injected below the step portion. A certain light intensity distribution is formed around this step. By developing this, a resist pattern finer than the mask pattern can be formed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1A, a positive photoresist 2 is applied on a desired base substrate 1 and a desired pattern is transferred from a mask 20 by a reduction exposure device or the like. And
Development is performed to form a step on the resist surface as shown in FIG.

Next, the entire surface is exposed by parallel rays having a wavelength λ. At this time, the light passing through the upper part of the step and the light passing through the lower part of the step have a resist and an exposure atmosphere (for example, the atmosphere). A phase difference occurs due to the difference in refractive index. This phase difference is represented by k'λ-kλ. (Here, k is the wave number in the exposure atmosphere, and k ′ is the wave number in the photoresist film.) Since this phase difference is π, k′λ−kλ = k (αλ−λ) = ( R + 0.5) λ (1) (R: Arbitrary integer α: Refractive index of photoresist against exposure atmosphere) k = (R + 0.5) /
Set it to (α-1). Then, the film thickness difference T between the upper part and the lower part of the step portion may be formed so that the step difference is satisfied by T = kλ = {(R + 0.5) / (α-1)} λ (2) Recognize.
In order to obtain this step amount, the exposure amount, the developer concentration, the developing time, etc. when forming the step are adjusted. In order to more accurately form the final resist shape, the exposure amount for forming the step is set to be smaller than the exposure amount when the entire surface is exposed later with parallel rays of wavelength λ. Further, the film thickness difference T between the upper part and the lower part of the step is
It is preferable that the thickness is thin due to reasons such as the transparency at the time of exposure of the entire surface afterwards, resolution, and depth of focus. Further, since the refractive index α of the photoresist is generally 1 <α, the thickness difference T can be minimized when R = 0, and the thickness at that time is T _0. , T ₀ = λ / {2 (α-1)}.

A step is formed so that there is a film thickness difference that satisfies the above expression (2), for example, T ₀ , and then FIG.
As shown in (c), the second exposure is performed on the entire surface by using parallel rays having a wavelength λ. Then, at the top and bottom of the step,
Since the phase is shifted by π, light is not injected under the step. Therefore, when the development is performed later, the resist remains on the lines of the resist surface step portion as shown in FIG. 1D, and a very fine line pattern can be formed.

A second embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 2A, a desired base substrate 1
A negative photoresist 3 is coated on the above, and exposed and developed in the same manner as in the first embodiment using a reduction exposure device or the like. At this time, the shape is as shown in FIG. 2B, but the step T _{1 at} this time is T ₁ = λ / {2 (β-1)}, where β is the refractive index of the negative photoresist. In this way, the first exposure and development conditions are set.

Next, as shown in FIG. 2C, a second exposure is performed on the entire surface. When development is performed later, the resist remains as shown in FIG. 2D, and a very fine space pattern can be formed. Next, a third embodiment of the present invention will be described with reference to the drawings. A negative photoresist is applied on a desired underlayer, and a pattern as shown in FIG. 3A is exposed by a reduction exposure device or the like. At this time, the exposure amount is set to 1/2 of the first exposure amount of the second embodiment.

Next, the pattern as shown in FIG. 3B is exposed. At this time, the exposure amount is set to 1/2 of the first exposure amount of the second embodiment. Then, the development is performed under the same development conditions as the first development conditions of the second embodiment. Then, as shown in FIG. 3C, a resist step is formed in a grid pattern, and the highest step region 9 of the resist step surrounding the intersection is formed.
And the step of the lowest step region 10 is λ / {2 (β-
1)}. Further, at this time, the middle part region 11 needs to have a sufficient level difference with the highest part region 9 and the lowest part region 10, and in particular, it is in the middle of the heights of the highest part and the lowest part. , It is easy to form a more circular pattern.

Next, the entire surface is exposed with parallel rays of wavelength λ. After that, when development is performed, as shown in FIG.
The hole pattern 12 is opened in the negative resist, and a very small hole pattern can be formed.

[0013]

As described above, according to the present invention, a resist coated on a desired underlayer is used for phase shift and exposure, so that a very fine pattern having a wavelength of light is formed. Is possible. Further, in the exposure for forming a step on the resist surface, since it is sufficient to form an image only on the resist surface, a depth of focus is not required, and when the entire surface is exposed, if the parallel short-wavelength rays are used, a lens having a high NA is used. Since it is not necessary to use the light that has passed through, it is possible to form a very fine pattern even in the step portion as a whole.
Further, by using the negative resist and the positive resist properly, and by forming the surface step in two steps, it is possible to form a complicated pattern such as a fine space pattern or a hole pattern. Further, by using a resist having a high transmittance for short-wavelength ultraviolet rays, if a parallel NA ray can be created even in a wavelength band in which a high NA lens is difficult to create, interference of light waves creates a contrast of light intensity, which is smaller than the wavelength. There is an effect that it is possible to pattern the line width or the space.

[Brief description of drawings]

1A to 1D are cross-sectional views in order of the processes, showing a method for manufacturing a semiconductor device according to a first embodiment.

2A to 2D are cross-sectional views in order of the steps, showing a method for manufacturing a semiconductor device according to a second embodiment.

3A to 3D are plan views in order of the steps, showing the method for manufacturing the semiconductor device according to the third embodiment.

4A and 4B are cross-sectional views in order of the processes, showing a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

 1 Base Substrate 2 Positive Photoresist 3,4 Negative Photoresist 5,7 Exposure Area 6,8 Emergency Light Area 9 Highest Step Area 10 Lower Step Area 11 Middle Step Area 12 Hole Pattern

Claims (1)

Claim: What is claimed is: 1. A step of applying a positive or screw photoresist on a semiconductor substrate, and a step of exposing and developing the photoresist to form a desired step on the photoresist surface. The step of exposing the entire surface to a parallel light beam of a single wavelength and developing, the difference in film thickness between the upper part and the lower part of the step portion is caused by the parallel light beam of a single wavelength when exposed to the photoresist. A method of forming a resist pattern using photolithography, characterized in that the thickness of the parallel light beam when incident on the lower surface of the stepped portion is shifted by an odd multiple of a half wavelength at the non-existing portion.