JPS5875832A - Forming method for square aperture for charged beam exposure apparatus - Google Patents

Abstract

PURPOSE:To enhance the patterning accuracy by superposing four aluminum foils having at least one linear side, thereby forming a mask having a square hole, and anisotropically dry etching an aperture material with the mask. CONSTITUTION:Four aluminum foils of 50mum thick cut at at least one linear side are employed and are superposed so that the linear sides form a square hole, thereby forming a mask 1. This is placed on a molybdenum 2 of 30mum thick, and is anisotropically etched under the conditions of CHF3+15%-O2 and 0.001Torr of gas pressure. The size of the square is arbitrarily set by the superposition of the foils 1. In this manner, highly accurate square aperture can be obtained, a square ultrafine spot beam can be generated using the same.

Description

[Detailed Description of the Invention] Kinoe @ describes a method for forming square apertures for charged beam exposure equipment.In recent years, as semiconductor integrated circuits have become highly integrated and dense, electron beam or ion It has become important to deform fine patterns by irradiating a charged beam such as a beam onto a resin. As such a charged beam, a circular minute spot beam is usually generated, and a rectangular minute spot beam is generated and used for high-speed processing and first exposure.

In the latter case, one or more square apertures are generally used to make the beam [square], but it is important to use square apertures with good dimensional accuracy. Since it is necessary to maintain dimensional accuracy when irradiated with a charged beam accelerated by voltage,
Typically, a molybdenum, platinum or thallium material with a thickness of about 30 mm is used.To process such aperture materials, aluminum or other materials are used as a mask for etching, but in the case of isotropic etching, the master Even if the hole is square, the aperture opening will have rounded corners and side etching (Figure 1a), so the aperture will not be square (Figure C, tb).

When this etching is performed isotropically, it is wet etching or reactive dry etching.

Aluminum is used as a master for molybdenum, and the pressure of etching gas CF + 15% O is 0.0 F.
5 Toyry, in the above case, it is mixed with reactive dry etching, and a rectangular aperture cannot be obtained for the above reasons. When the gas pressure is 0.002 Torr or less, anisotropic etching occurs, but in order to process molybdenum, the aperture material, with a thickness of 30 μm, the thickness of the mask material, aluminum laminate, must also be 2
It is difficult to obtain patterning with such a thick aluminum strip that has a high degree of deposition when using a resist.

The aim of the invention is to eliminate the above-mentioned drawbacks.

The above-mentioned object of the present invention is to anisotropically dry-etch an aperture material by stacking four aluminum foils each having at least one straight side to form an aluminum mask with a rectangular opening having arbitrary dimensions. This can be achieved by a method of creating a rectangular aperture for charged beam exposure**, which is characterized by the following. “The method of the present invention will be illustrated with reference to Figure 2a*%?L!!@ ・Using four sheets of aluminum foil with a thickness of 4 ISOam, cut so that at least one side is a straight line. Then, overlap them to form a rectangular opening surrounded by straight sides to form a mask L (Fig. 2a), place it on a 30μ thick molybdenum film, and apply a gas pressure of 0.001T to %CHF, +15Is.
Anisotropic etching was performed on the corners of the aperture with no roundness (Fig. 2b). As an aperture, we were able to generate a small rectangular spot beam.

[Brief explanation of drawings]

1aIQ is a cross-sectional view of the mask and aperture in isotropic etching, the glib diagram is a plan view of the 1st & 1st line, and 2a
The figure is a sectional view of the mask and aperture used in the present invention, and FIG. 2b is a sectional view taken along the line nb-IIb of FIG. 2a.
Figure 2c is ■ in Figure 2b. - Roto, which is a solid plan view.
...Mask, 2...Aperture. Figure 1Q Figure 1b

Claims (1)

[Claims] 1. Aluminum with at least one side being a straight line t is <t-
A method for creating a rectangular aperture for charged beam exposure by overlapping four sheets and anisotropically dry etching the aperture material using an aluminum master with a rectangular opening of an arbitrary dimension tV.