JPS61288426A - Taper etching method for aluminum film - Google Patents

Abstract

PURPOSE:To make it possible to control the tapered shape of an Al-Si alloy film in a highly accurate manner by a method wherein the thickness of the first and the second photoresist films and the amount of the first and the second photoresost films and the amount of exposure of a pattern are controlled properly. CONSTITUTION:After an Si dioxide film 2 is formed on the surface of a silicon substrate 1, an Al-Si alloy film 3 of approximately 1mum thickness containing the silicon of approximately 1wt% is formed. The first positive photoresist film 4 of approximately 1.0mum thickness and a positive type photoresist film 5 of approximately 0.5mum thickness having the sensitivity lower than that of said photoresist 4, is formed. Then, when the exposure treatment and the pattern developing treatment for formation of a pattern are performed on the photoresist films 4 and 5, these films can be formed in the cross-sectional shape wherein the photoresist film 5 is brought into overhang form for the photoresist film 4. When a dry etching treatment is performed on the Al-Si alloy film 3 using said photoresist film as a mask, the wiring pattern of the Al-Si alloy film 3 having an excellent tapered shape can be formed.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention provides a method for controlling the cross-sectional shape of a pattern of a wiring electrode material widely used in the manufacture of semiconductor devices. It can be used for manufacturing semiconductor devices.

Conventional technology When manufacturing multilayer wiring using an aluminum film or aluminum alloy film, it is necessary to provide good step coverage of the glabella insulating film at the edge of the wiring pattern of the first layer aluminum film or aluminum alloy film. In order to achieve this, it is required that the pattern of the first layer of aluminum film or aluminum alloy film has a tapered cross-sectional shape.
-) and (b), when dry etching the aluminum film or aluminum alloy film 3, the etching speed ratio with the resist 6 is completely controlled, and the etching speed of the resist 6 is controlled to be the same as that of the aluminum film or aluminum alloy film 3. When the etching speed approaches the etching speed of the alloy film 3, the pattern width of the resist 6 becomes gradually smaller during etching, so that the cross-sectional shape of the pattern of the aluminum film or aluminum alloy film 3 becomes tapered.

Problems to be Solved by the Invention In the conventional method of bringing the etching speed of a resist closer to the etching speed of an aluminum film or aluminum alloy film, the resist dimensions during etching are reduced not only in the lateral direction of the pattern but also in the thickness direction. Therefore, if there is a large step on the base of the aluminum film or aluminum alloy film, the resist film thickness will be thinner at the top of the step than in other parts. Since the aluminum film or aluminum alloy film in the high part of the base layer may be disconnected due to the etching process, the practical use of this method has been limited. Furthermore, it was difficult to control the taper shape of the aluminum film or aluminum alloy film formed thereby.

Means for Solving the Problems The present invention involves forming a first resist film and a second resist film having lower sensitivity than the first resist film on the surface of an aluminum film or an aluminum alloy film, and then forming a pattern. This process includes a process of performing exposure processing and pattern development processing for the purpose of the film, and then dry etching the aluminum film or aluminum alloy film.

Function After forming the first resist film and the second resist film with lower sensitivity than the first resist film, when exposure processing and pattern development processing for pattern formation are performed, the second resist film with lower sensitivity is The film is formed in a cross-sectional shape that overhangs the pattern of the first resist film. When the aluminum film and aluminum alloy film are then dry-etched, the second resist is gradually reduced during the etching process, and the aluminum film or aluminum alloy is also removed from the end of the first resist pattern at the bottom of the overhang. Etching of the film progresses,
A good taper shape can be obtained.

Further, by controlling the first resist film thickness, the second resist film thickness, and the pattern exposure amount, it is possible to precisely control the taper shape of the aluminum film or aluminum alloy film by etching.

Embodiment FIGS. 1(a) and 1(b) are sectional views showing step-by-step process steps in which taper etching of an aluminum film was performed by the method of the present invention. As shown in FIG. 1(a), after forming a silicon dioxide film 2 on the surface of a silicon substrate 1, approximately 1ωt
% silicon-containing Al-3i alloy film 3 with a thickness of about 1 μm
It is formed to a thickness of about 1.0 mm. A positive type first photoresist film 4 having a thickness of #fn and a positive type photoresist film 5 having a thickness of about 0.6)Lm and having a lower sensitivity than the first photoresist film 4 are formed. Thereafter, when the photoresist film 4 and the second photoresist film 6 of the cylinder 1 are subjected to exposure processing and pattern development processing for forming a pattern, the first photoresist film 4 is larger than the second photoresist film 5. During exposure processing, due to the reflection effect from the underlying Al-5i alloy film, the first 7
The second photoresist film 5 can be formed in a cross-sectional shape overhanging the photoresist film 4. When the Al-8t alloy film 3 is dry-etched using a mixed gas of BCl3 and C12 using the photoresist film as a mask, the second resist film 5 is etched as shown in FIG. 1(b). The etching of the Al-5t alloy film 3 also progresses from the pattern end of the first 7 photoresist film 4 below the overhang part. A wiring pattern of the -3t alloy film 3 can be formed.

Effects of the Invention According to the method of the present invention, the taper shape of the Al-5t alloy film formed by controlling the first 7-photoresist film thickness, the second 7-photoresist film thickness, and the pattern exposure amount can be controlled with high precision. Therefore, it can be applied to a wide range of processes.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are cross-sectional views in the order of steps of an embodiment of the present invention, and FIGS. 2(a) and (b) are cross-sectional views in the order of steps of a conventional example. 1...Silicon substrate, 2...Silicon dioxide film, 3...Aluminum film, 4,6.6.
...Photoresist film.

Claims (2)

[Claims] (1) A first resist film and a second resist film having lower sensitivity than the first resist film are formed on the surface of the aluminum film or aluminum alloy film, and then the first resist film is formed.
A taper of an aluminum film, characterized in that the resist film and the second resist film are subjected to an exposure treatment and a pattern development treatment for pattern formation, and then a dry etching treatment is performed on the aluminum film or aluminum alloy film. Etching method. (2) The method for taper etching an aluminum film according to claim 1, wherein the first and second resist films are positive resists.