JPH04257215A - Formation of resist pattern - Google Patents

Abstract

PURPOSE:To form a microhole pattern stably by improving decomposition resolution using an existing projection aligner. CONSTITUTION:After a photoresist layer 1 is overlaid with a convex lens layer 2, a predetermined pattern is transferred and exposed to light from above the convex lens layer 2; then, development is made with the convex lens layer 2 removed.

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 for forming extremely fine hole-like resist patterns in a semiconductor manufacturing process by improving the separation resolution characteristics of a projection exposure apparatus. It is something.

0002

2. Description of the Related Art With the increasing optical integration of semiconductor devices, there is a need for a technique for forming extremely fine resist patterns. 2. Description of the Related Art To form a resist pattern in a semiconductor manufacturing process, a method is generally used in which a predetermined pattern is transferred onto a photoresist film on a substrate using a projection exposure apparatus, exposed, and then developed. The separation resolution characteristics of the resist pattern by this method are limited by the chemical characteristics of the photoresist film 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 described above can be improved by using a shorter exposure wavelength and a projection lens with a larger numerical aperture. However, improvements will not be made in a short period of time because it requires the development of light sources and lens glass materials, as well as advances in lens manufacturing technology. In the semiconductor manufacturing process, as patterns become finer, patterning is forced to occur in an area close to the resolution limit of a projection exposure apparatus. In particular, when forming a hole-like pattern, the resolution is lower than when forming a line pattern of the same size.

The present invention is intended to solve these problems, and aims to stably form fine hole-like patterns by improving separation resolution while using an existing projection exposure apparatus.

[0005]

[Means for Solving the Problem] In order to solve this problem, the present invention forms a convex lens layer on a photoresist film, transfers a predetermined pattern onto the photoresist film from above the convex lens layer, and then exposes the convex lens. The layer is removed and developed.

[0006]

[Operation] The optical separation resolution of the projection exposure apparatus is inversely proportional to the numerical aperture of the projection lens if the exposure wavelengths are the same. The numerical aperture of the projection lens is NA, and the viewing angle of the pupil of the projection lens is 2.
If θ is the refractive index of the air between the lens surface and the imaging surface, then NA=n·sin θ. When the projected light is incident on a flat photoresist film, the refractive index of the photoresist film is generally 1 or more, so the viewing angle of the pupil in the photoresist film becomes smaller in accordance with the refractive index. However, the numerical aperture does not change because it is proportional to the refractive index of the medium. Here, if a convex lens layer is formed on the photoresist film to increase the viewing angle of the pupil in the photoresist film, it is possible to increase the numerical aperture and improve the separation resolution. When projecting a hole-shaped pattern, a circular convex lens layer may be formed in the image forming area.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a photoresist film 1 has a convex lens layer 2 formed thereon, and ultraviolet light 3 is transmitted through a hole-shaped reticle 4 and then passed through a projection lens 5.
The substrate 7 passes through the convex lens layer 2 and the buffer layer 6.
An image is formed on the upper photoresist film 1. At this time, if the curved surface and material of the convex lens layer 2 are optimized, the viewing angle of the pupil in the photoresist film 1 can be made larger than in the case without the convex lens layer 2, and the numerical aperture can be increased by about 1.2 times. can be improved. After the exposure process is completed, the convex lens layer 2 is removed using a release agent, and then the buffer layer 6 is removed and the photoresist film 1 is developed by a development process. In this embodiment, the convex lens layer 2
After forming a convex lens pattern by photolithography using a novolak positive photoresist with a thickness of 1.4 μm, the curved surface is optimized by heat treatment. The buffer layer 6 facilitates the peeling of the convex lens layer 2, and is made of polyvinyl alcohol with a thickness of 0.1 μm. For the photoresist film 1, a novolak positive type photoresist with a thickness of 1.0 μm is used. Ethyl cellosolve acetate is used to remove the convex lens layer 2. Furthermore, an organic alkaline aqueous solution is used as the developer. In the above embodiment, G-line is used as the ultraviolet light 3, and a projection lens 5 with a numerical aperture of 0.45 is used.
A hole pattern of 5 μm can be stably formed.

[0008]

Effects of the Invention As is clear from the above description, according to the present invention, it is possible to improve the separation resolution of hole-like resist patterns very easily, and the numerical aperture of the projection exposure apparatus can be substantially reduced by 20%. The above can also be improved. Furthermore, if the processing method of the convex lens layer is studied, it can be applied to line-shaped patterns, which is useful for the semiconductor manufacturing process where miniaturization is progressing, and has high industrial value.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a method of forming a resist pattern in an embodiment of the present invention.

[Explanation of symbols]

1 Photoresist film 2 Convex lens layer 3 Ultraviolet light 4 Hole-shaped reticle 5 Projection lens

Claims (1)

[Claims] 1. After forming a convex lens layer on a photoresist film, a predetermined pattern is transferred and exposed onto the photoresist film from above the convex lens layer, and then the convex lens layer is removed and a development process is performed. How to form a resist pattern.