JPS59189626A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a contact hole which does not allow the dielectric strength of interlayer insulating film and has a high pattern size accuracy for tapered etching by using a first etching mask having a high etching characteristic and a second photo etching mask by the photo resist for an insulating film. CONSTITUTION:A polycrystalline silicon 13 which becomes a first etching mask is formed at the surface of interlayer insulating film 12 on semiconductor substrate 11. The anisotropic etching is carried out to the polycrystalline silicon 13 using a photo resist film 14 and a first etching mask is formed by the polycrystalline silicon 13. Thereafter, a second etching mask 15 having a contact window which is smaller than that of the first etching mask 13 is formed using the photo resist film. The tapered etching is carried out to such a pattern having the etching masks 13, 15 in such a double-layer structure using the plasma obtained by adding oxygen gas to the fluorine gas plasma. Thereafter, the first and the second etching masks 13, 15 are removed and a tapered contact hole 16 can be obtained. An electrode of aluminium film 17 is formed on such hole.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of forming a contact hole for contacting an electrode.

Conventional configurations and their problems Conventional - Due to the miniaturization of processing dimensions in the formation of contact holes in insulating films on semiconductor devices, in recent years parallel plate type dry etching equipment has been used to achieve anisotropic etching without side etching. Etching is now in practical use.

However, in anisotropic etching of contact holes, it is difficult to obtain sufficient etching selectivity for the underlying etching film of the photoresist mask used as an etching mask, which causes significant damage to the photoresist mask due to gas plasma, which causes a drop in breakdown voltage of the underlying interlayer insulating film. It becomes. Further, the contact hole formed by anisotropic etching has a steep hole edge, which causes a problem in that the aluminum wiring is easily disconnected.

Figure 1 is a cross-sectional view of a contact hole formed using a conventional anisotropic etching method. film, 4 is an aluminum film for wiring,
5 is a CVD silicon oxide film as an interlayer insulating film, and 6 is a contact hole. As the pattern size of the contact hole 6 becomes finer and the thickness of the interlayer insulating film 5 becomes thicker, it is necessary to form a deep contact hole, which results in disconnection of the aluminum wiring at the edge of the hole. Cheap.

Purpose of the Invention The present invention is an attempt to solve the above-mentioned problems.By using a first etching mask that has high etching selectivity with respect to the insulating film, the pattern size can be improved without reducing the withstand voltage of the interlayer insulating film. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can form contact holes with high precision and can also perform taper etching by using a second etching mask made of photoresist.

Structure of the Invention In the present invention, a polycrystalline silicon film or an aluminum film, which is a first etching mask material, is formed on an insulating film.

These films have extremely high etching selectivity compared to photoresist masks, so they can be formed with a thin film thickness, and they also have high pattern dimensional accuracy due to anisotropic etching.
Form an etching mask. A second etching mask having contact windows smaller than the first etching mask pattern size is then formed using a photoresist mask. After this, the first. Using the second etching mask as a mask, the insulating film is dry etched using gas plasma containing oxygen gas to form a tapered opening in the insulating film.

DESCRIPTION OF EMBODIMENTS Embodiments of the present invention will be described below, taking as an example a case where a contact ball is formed on a silicon substrate.

First, as shown in FIG. 2(-), polycrystalline silicon 13, which will serve as a first etching mask, is etched on the surface of the interlayer insulating film 12 on the semiconductor substrate 11 at a reduced pressure of 200 to 5000 A.
Formed by VD method. Next, the polycrystalline silicon 13 is anisotropically etched using the photoresist film 14 to form a first etching mask using the polycrystalline silicon 13 (FIG. 3(b)).

Furthermore, a second etching mask 1d having a contact window smaller than that of the first etching mask 13 is formed using a photoresist film by a single photolithography step (FIG. 3C). Such a two-layer etching mask 13.
Taper etching is performed to form a pattern having the pattern No. 15 using a fluorine gas plasma to which oxygen gas is added. This etching creates the second etching mask 1.
5 is etched by plasma to form a tapered contact hole (d in the same figure). Next, the first. Second
The etching masks 13 and 15 are removed to obtain a tapered contact hole 16 (see e in the figure). Then, an aluminum film 17 as an electrode is formed on this (FIG. 5f).

Effects of the Invention According to the method of the present invention, since the first etching mask has high etching selectivity, its film thickness can be reduced, and a fine etching pattern can be formed using a photoresist film. Since the etching mask has a two-layer structure, the influence of etching on the interlayer insulating film can be reduced. Furthermore, the taper angle of the contact hole can be independently controlled using the second etching mask. Furthermore, since the first etching mask is formed under the second etching mask, the thickness of the photoresist film that is the second etching mask can be made thinner, making it easier to pattern extremely fine contact windows using a single photolithography process. This method has the effect of significantly improving the quality of semiconductor devices, such as reducing breakdown voltage due to dry etching of interlayer insulating films, improving @ lines of aluminum wiring, and improving dimensional accuracy of pattern processing.

[Brief explanation of the drawing]

FIG. 1 is a sectional view for explaining a conventional contact hole forming method, and FIGS. 2(a) to 2(f) are process sectional views showing a method for manufacturing a semiconductor device according to the present invention. 11... Semiconductor substrate, 12... Interlayer insulating film,
13. ,,, First etching mask, 15...
...Second etching mask, 1 completion...Aluminum film. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 5 Figure 2 Figure 2

Claims (2)

[Claims] (1) A step of forming an insulating film on the surface of a semiconductor substrate, and then forming a first etching mask for forming a contact hole having high etching selectivity with respect to the insulating film, the first etching mask forming a second etching mask using a photoresist film to open a window for forming a small contact hole; A method of manufacturing a semiconductor device, comprising the step of dry etching the insulating film using a second etching mask as a mask. (2) The method for manufacturing a semiconductor device according to claim 1, wherein the first etching mask is a polycrystalline silicon film.