JPS5825234A - Formation of resist pattern - Google Patents

Abstract

PURPOSE:To accurately obtain a less-than-1mum minimal resist pattern by shifting the same pattern on a semiconductor wafer and exposing more than two times through the reduced projection type exposure method used mainly for loose devices of 2-3mum. CONSTITUTION:A positive photo resist 2 with a thickness of approx. 1mum is formed on a substrate 1, and a specified pattern is transferred to this resist using a reduced projection type exposure apparatus. Portions d of the resist 2 shown in the figure are the ultimately desired portions, while portions 3 are alkali-solubilized portions resulted from the first pattern transfer. Without removing the substrate 1 from the exposure apparatus after the first pattern transfer, an exposure position is shifted a specified length of less than 1mum and the same pattern is again transferred so that alkali-solubilized portions 4 are partially produced within the portions 3. Finally, the substrate is removed from the apparatus and subjected to development to remove the portions 3, 4 to retain the desired portions d on the substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a resist pattern of a predetermined shape on the surface of a substrate such as a semiconductor unit.

2. Description of the Related Art As various devices, mainly semiconductor devices, become denser and more highly integrated, there is a demand for smaller pattern dimensions. In the manufacturing process of semiconductor devices, miniaturization of etching masks for etching various thin films into predetermined pattern shapes has become an important issue. This etching mask is 1
Usually, it is formed by photo-transferring a mask pattern of a predetermined shape onto an organic polymer resist and then performing a development process.

Note that, conventionally, the mainstream phototransfer method has been to bring a mask and a semiconductor wafer into close contact with each other and perform batch transfer using ultraviolet light. Later, the diameter of semiconductor wafers became larger, and as semiconductor devices became more dense and highly integrated, chip areas also became larger. Pattern dimensions became smaller, and optical transfer methods changed from contact exposure to reflective projection exposure, and then to reduction projection. There is a shift towards a type exposure method.

However, in the exposure method using light, the limit is to obtain a resolution of about 1 μm due to the wavelength of the light used. For this reason, an exposure method using deep ultraviolet light, a wafer direct exposure method using an electron beam, and an exposure method using X-rays are being considered, but none of them have reached the practical stage.

The present invention uses a reduction projection exposure method, which is said to be the mainstream for 2 to 3 μm rule devices, and uses the same mask on a substrate such as a semiconductor wafer to perform exposure processing two or more times to create a fine resist pattern of 91 μm or less. The aim is to form the image with high precision.

Hereinafter, a case in which a fine resist pattern is formed by the method of the present invention will be described with reference to cross-sectional views of embodiments.

First, as shown in FIG.
A positive type photoresist 2 of μm size is formed and prepared. The portion indicated by d in this resist 2 is the portion that is ultimately desired to remain. A predetermined pattern is transferred onto this silicon substrate 1 using a reduction projection type exposure device.

FIG. 2 is a diagram showing the state after pattern transfer, and 3 in the figure is a resist portion that has been separated by ultraviolet light and has become alkali-soluble. Thereafter, without taking out the silicon substrate 2 from the exposure unit, the exposure position is shifted from the first exposure position by a predetermined dimension (for example, a dimension of 1 μm or less) and the same pattern as described above is transferred.

The accuracy of the shift amount at this time is determined by the stage accuracy of the reduction projection exposure apparatus, but the stage accuracy of this apparatus is 0.
High accuracy of 0.06 μm or less. FIG. 3 shows the state of the resist after the second exposure. In the figure, 4 indicates a part of Talecyst that is photodecomposed and becomes alkali-soluble by the second exposure. Thereafter, the silicon substrate is taken out of the exposure apparatus and subjected to development processing.

FIG. 4 shows a cross section of the resist after development. In this development process, even after the double exposure process, the pattern which was not irradiated with light remained and the pattern had very good dimensional accuracy compared to the pattern obtained by the exposure process of all other resists. Further, although a halo-type photoresist is used in this embodiment, the same effect can be obtained with a negative-type photoresist.

Note that the mask can be moved arbitrarily in one direction or in a direction perpendicular to this direction, and various photoresist patterns can be formed with high precision.

As explained above, the resist pattern (turn) formed on a semiconductor substrate by the method of the present invention has better precision than the resist pattern (turn) obtained by normal exposure.
It also has good reproducibility.

Furthermore, according to the method of the present invention, it is possible to easily obtain resist patterns with minute dimensions, and since the shift amount of the exposure position can be freely controlled, it exhibits the excellent effect of arbitrarily obtaining resist patterns with various dimensions. can do.

Although the present invention has been explained above using the formation of resist turns on a semiconductor substrate as an example, it goes without saying that the method of the present invention can also be applied to the formation of resist turns on other substrates. The second exposure process also does not need to be performed once, and may be performed twice or more.

[Brief explanation of the drawing]

1 to 4 are cross-sectional views showing the process of forming a resist pattern according to an embodiment of the present invention. 1...Silicon substrate, 2...Positive photoresist h3...Photoresist portion exposed by first exposure, 4...... by second exposure Exposed photoresist area.

Claims (2)

[Claims] (1) When forming a pattern on a photoresist film deposited on a substrate surface through an exposure mask using a reduction projection exposure method, a first exposure process in which the exposure mask is aligned at one position on the substrate surface and exposed. A method for forming a resist pattern, the method comprising: performing a second exposure process in which the exposure mask is shifted by a predetermined dimension from the above position, and then a development process is performed. (2) The method for forming a resist pattern according to claim 1, wherein the second exposure process includes a step consisting of parallel shift of an exposure mask and exposure two or more times.