JPH01302256A - Photomask for rectangular pattern resolution - Google Patents

Abstract

PURPOSE:To form a fine rectangular contact hole by providing a couple of rectangular mask patterns across a specific separation area. CONSTITUTION:This is a photomask using a chromium thin plate and the couple of rectangular mask patterns 2A and 2B (opening part) are bored adjacently so that their one-side parts face each other across the separation area 1. Here, the patterns 2A and 2B are formed to such size that they can be exposed to UV light, etc., and the area 1 is formed to such width that it is not exposed to and resolved with the UV light, etc. This mask is used to form the contact hole by photoetching and then the fine rectangular contact hole 3 is formed with good resolution.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a photomask. More particularly, the present invention relates to photomasks used in photoetching processes during the manufacturing process of integrated circuits.

(0) Conventional Technology There is an increasing demand for improved operating speed for integrated circuits. Efforts are being made to increase the degree of integration of circuits as a means of meeting such demands. One of the important points for increasing the degree of circuit integration is improving the resolution in the photoetching process. Of these, the method of exposing and resolving a photoresist pattern for etching using a photomask and then performing etching to form fine contact holes with high resolution is one of the important technologies to cope with the increase in the degree of integration. It is.

In this regard, efforts have been made to improve the resolution of photoetching by improving materials (photoresists, developing solutions, etc.) and exposure equipment. In particular, with regard to materials, attempts have been made to develop high-resolution photoresists by improving the degree of dispersion of molecular weight distribution and photosensitive groups.

(c) Problems to be solved by the invention However, there are limits to the improvement of resolution in terms of these materials, and it is difficult to form fine contact holes in the submicron region with high resolution, especially on adjacent sides. It has been difficult to form fine rectangular contact holes with different side lengths at high resolution. For example, when resolving photoresist by exposing it to ultraviolet light using a photomask with a rectangular open pattern, only an elliptical resolution pattern will be obtained due to the influence of light unless the short sides are long enough. First, it was not possible to form a fine rectangular contact hole.

The present invention was made under such circumstances, and particularly aims to provide a photomask capable of forming fine rectangular contact holes.

(d) Means for solving the problem As a result of intensive research from the above perspective, the inventors have found that:
In a photomask having a fine rectangular aperture, by interposing a separation bridge in the center of the aperture with a width that is not resolved by exposure, the exposure resolution can be significantly improved.
The present invention was achieved by discovering the fact that a rectangular contact hole corresponding to the opening shape of a mask can be efficiently formed.

Thus, according to the present invention, a pair of rectangular mask patterns of a size that can be resolved by exposure are formed in a rectangular shape formed by adjacent openings on a photomask plate, through a separation region with a width that cannot be resolved by exposure. A photomask for shape pattern resolution is provided.

The separation region in the present invention has a width such that the target photoresist is not resolved by exposure, and is usually 0.
Approximately 2 to 0.4 degrees is suitable. On the other hand, the negative set of mask patterns, ie, the openings, may be of a rectangular shape obtained by dividing the intended rectangular pattern into two by the separation region, and each has a size that can be resolved by exposure. In general, a square or rectangular opening having a side length of about 0.6 to 1.0 cm is suitable for forming a fine pattern.

(e) Operation The separation area that partitions the rectangular mask patterns is formed into a substantially rectangular shape corresponding to the size of the two sets of rectangular mask patterns by diffraction-dispersing the irradiation light without resolving the photoresist to be exposed. acts to form an image on the photoresist.

(f) Example FIG. 1 shows a mask pattern for forming contact holes in a photomask of the present invention using a thin chromium plate. As shown in the figure, the photomask has a -set of rectangular mask patterns 2A.

2B (openings) are adjacently opened so that one side thereof faces each other with the separation region 1 interposed therebetween. Here, patterns 2A, 2
Each of B has a size that allows UV exposure, specifically, a
-1,04,b -0,6s, and the width of the separation region bX1 is set to be narrow enough not to be exposed to UV light.
Specifically, it is set as C-0,24.

Using this photomask, contact holes were formed by photoetching.

The photoetching process used was as follows.

(+) A positive photoresist is applied onto a substrate such as a semiconductor having a SiO□ oxide film on its surface.

0) Heat-treat the substrate to remove the solvent remaining in the photoresist film.

(To) Position the above-mentioned mask at the desired position on the substrate.

(f) Ultraviolet light (405 to 436 rv) using an exposure device
) onto the photomask.

(V) Developing the photoresist using a developer such as an organic solvent.

The surface of the substrate is etched by 60 reactive ion etching to form contact holes.

The contact hole pattern 3 obtained by the above procedure is shown in FIG. In the figure, d −0,64, e −
It is 1,34. It has been found that by using a photomask having a set of mask patterns separated in this manner, a contact hole having a fine rectangular pattern corresponding to the combined shape of these patterns can be formed.

In addition, in order to confirm how the intensity distribution of the irradiated U light on the resist surface changes due to the presence of separation region 1, a two-dimensional light intensity distribution at a UV wavelength of 436 nm was calculated and drawn by simulation. The third result is
Shown in the figure. It can be seen that the existence of the separation region 1 reduces the so-called shadow portions that may occur at the corners of each rectangular mask pattern.

(g) Effects of the Invention According to the photomask of the present invention, fine rectangular contact holes can be formed with high resolution by photoetching. Therefore, by using this photomask, constraints on the layout of various semiconductor devices such as memory devices can be further relaxed, and its usefulness in the field of semiconductor device manufacturing is extremely large.

[Brief explanation of the drawing]

FIG. M1 is an enlarged plan view showing a mask pattern in the photomask of the present invention, FIG. 2 is an enlarged plan view showing a contact hole pattern formed by the mask pattern of FIG. 1, and FIG. 2 by mask pattern
FIG. 3 is a graph diagram showing a dimensional light intensity distribution. 1... Separation area, 2A, 2B... Rectangular mask pattern box 1
Jump flute 2 diagram jI31! IX(,L4JTl)

Claims (1)

[Claims] 1. For resolving rectangular patterns, a set of rectangular mask patterns of a size that can be resolved by exposure are opened adjacent to each other on a photomask plate through a separation region with a width that cannot be resolved by exposure. Photomask.