JPH0594946A - Method of forming resist pattern - Google Patents

Abstract

PURPOSE:To form a convex lens layer on a photoresist film to increase the substantial aperture number of an optical system and to improve the resolution of a pattern. CONSTITUTION:Ultraviolet rays 1 transmit a reticle 2 under a hole pattern and thereafter, image and expose a photoresist film 5 on a substrate 6 and a convex lens layer 4 on the film 5 by a projection lens 3. At this time, if the curved surface of the layer 4 is optimized, it is possible to make larger the visual angle of a pupil in the resist than that in the case where there is not the layer 4 and the substantial aperture number of an optical system can be improved by 1.2 times or more. In this embodiment, a photoresist film is previously formed on the substrate 6 in a thickness of 1.4mum using a P-type novolak resist and thereafter, a dot pattern of a diameter of 1.2mum is transferred and exposed by a projection exposing device and is developed to a thickness of 0.4mum from the upper layer of the pattern. In this process, the dot pattern developed by choosing optimally the exposure of the focal point of the projection exposing device is formed into a convex lens form.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resist pattern forming method capable of forming an extremely fine hole-shaped resist pattern by improving the separation resolution characteristic of a projection exposure apparatus in the formation of a resist pattern in a semiconductor manufacturing process. .

[0002]

2. Description of the Related Art Along with the optical integration of semiconductor devices, there is a demand for a technique for forming an extremely fine resist pattern. In forming a resist pattern in a semiconductor manufacturing process, a method is generally used in which a photoresist film on a substrate is transferred and exposed with a predetermined pattern by a projection exposure apparatus and then developed. The separation resolution characteristics of the resist pattern by this method are limited by the chemical characteristics of the photoresist and the optical characteristics such as the exposure wavelength of the projection exposure apparatus and the numerical aperture of the projection lens.

[0003]

The separation resolution performance of the projection exposure apparatus can be improved by using a projection lens having a shorter exposure wavelength and a higher numerical aperture. However, it will not improve in a short period of time because development of the light source and lens glass material and advancement of lens manufacturing technology are required. In the semiconductor manufacturing process, pattern miniaturization and patterning in an area close to the limit resolution of a projection exposure apparatus are inevitable.
In particular, in forming a hole-shaped pattern, the resolution is lower than that of a line pattern having the same size.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to improve the separation resolution and stably form a fine hole-like pattern while using an existing projection exposure apparatus. .

[0005]

According to the present invention, as means for achieving the above object, a predetermined upper layer portion on a single-layer photoresist film is processed into a convex lens shape, and a predetermined pattern is transferred and exposed from the convex lens layer. After that, a development process is performed to improve the optical separation resolution and easily form a fine hole-shaped pattern.

[0006]

The optical separation resolution of the projection exposure apparatus is inversely proportional to the numerical aperture of the projection lens if the exposure wavelength is the same. NA is the numerical aperture of the projection lens, and the angle of entry of the projection lens is 2
Letting θ be n and the refractive index of air between the lens surface and the image plane be n, NA = n · sin θ is expressed. When the projected light is incident on the flat photoresist film, the refractive index of the photoresist is generally 1 or more, so that the angle of entry of the pupil in the photoresist decreases according to the refractive index. However, since the numerical aperture is proportional to the refractive index of the medium, the numerical aperture does not change. Here, if the predetermined upper layer portion on the single-layer photoresist film is processed into a convex lens shape to increase the pupil misalignment angle in the photoresist film, the numerical aperture can be increased and the separation resolution can be improved. it can. When projecting a hole-shaped pattern, a circular convex lens layer may be formed in the image forming portion.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. After the ultraviolet light 1 passes through the reticle 2 having a hole pattern, the projection lens 3 causes the photoresist film 5 on the substrate 6 to pass through.
The convex lens layer 4 is imaged and exposed. At this time, the convex lens layer 4
If the curved surface is optimized, the angle of pupil entry in the resist can be made larger than in the case without the convex lens layer 4, and the substantial numerical aperture can be improved to 1.2 times or more. In this embodiment, a photoresist film having a thickness of 1.4 μm is formed on the substrate 6 in advance using a novolac-based positive resist, and then a dot pattern having a diameter of 1.2 μm is transferred and exposed by a projection exposure apparatus to form an upper layer. To a thickness of 0.4 μm. In this step, the developed dot pattern has a convex lens shape by optimally selecting the focus and exposure amount of the projection exposure apparatus. As a result,
The convex lens layer 4 having a thickness of 4 μm and the photoresist film 5 having a thickness of 1 μm are formed. The projection lens 3 that transfers and exposes the hole pattern has a numerical aperture of 0.45 and the ultraviolet light source is g-line. The photoresist film 5 and the convex lens layer 4 that have been transferred and exposed are developed with an organic alkaline developer. This gives 0.5
A hole pattern of 5 μm can be formed.

It is a matter of course that the convex lens layer 4 can be applied to a line-shaped pattern by improving the processing method.

[0009]

As is apparent from the above description, according to the present invention, the predetermined upper layer portion on the single-layer photoresist film on the substrate is processed into a convex lens shape, and then the predetermined photoresist film is formed on the convex lens layer. Since the pattern is transferred and exposed and then developed, the separation resolution of the hole-shaped resist pattern can be improved very easily, and the numerical aperture of the projection exposure apparatus can be improved substantially by 20% or more. It is possible to provide a method for forming a fine resist pattern that can be performed.

[Brief description of drawings]

FIG. 1 is a structural cross-sectional view showing a method for forming a resist pattern according to an embodiment of the present invention.

[Explanation of symbols]

 1 UV light (g line) 2 Hole pattern reticle 3 Projection lens 4 Convex lens layer 5 Photoresist film 6 Substrate

Claims (1)

[Claims] 1. A predetermined upper layer portion of a single-layer photoresist film on a substrate is processed into a convex lens shape, and then a predetermined pattern is transferred and exposed from the convex lens layer onto the photoresist film.
A method for forming a resist pattern, which comprises performing a development process.