JPH04217324A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve the filming property of a resist in etching of the barrier metal existing in the layer below a bump, after formation of the bump. CONSTITUTION:Negative resist is applied thick on a silicon substrate 1, where a barrier metal 5 is made, and the negative resist is overexposed to form a resist 7, whose cross section is reversely tapered, and with this resist 7 as a mask, a bump 6 is made by electrolytic plating method. Then, the barrier metal 5 is selectively etched. The overetching of the barrier metal right below the bump 6 can be prevented, and the contact area between the bump 6 and the barrier metal 5 widens enough, and the adhesive strength of the bump 6 improves. Furthermore, corrosion by the etchant of an aluminum pad 3 is prevented and the yield rate and the reliability improve.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming bumps.

0002

[Background Art] In recent years, as semiconductor integrated circuits have become more highly integrated, denser, and have more pins, TAB (Tape Automated Bond) using bumps has been used instead of conventional wire bonding technology in the mounting of semiconductor integrated circuits.
ding) technology is used. There are various methods for forming bumps, one of which is electrolytic plating. The shape of bumps produced by electrolytic plating was mainly mushroom-shaped, but in recent years there has been a trend toward smaller pad pitches due to higher integration, higher density, and increased number of pins. The development of bumps is becoming more popular.

[0003] Hereinafter, straight bumps formed by conventional methods (hereinafter referred to as "straight bumps")
I will explain about it. FIG. 2(a) is a cross-sectional view after straight bumps are formed, and 1 is a silicon substrate, 2 is an insulating film, 3 is an aluminum pad, 4 is a protective film, 5 is a barrier metal, and 16 is a straight bump. The straight bump 16 is formed by electrolytic plating using a mask patterned with a thick film resist, and its cross-sectional shape is shown in FIG.
a) The side walls are almost vertical as shown in .

0004

However, in order to selectively etch the barrier metal 5 underlying the straight bump 16 having vertical sidewalls, when a resist is patterned using a normal photolithography technique, as shown in FIG. 2(b). As shown in FIG. 2(c), the film characteristics of the resist 18 at the straight bump 16 portion deteriorate, and when selectively etching the barrier metal 5, the barrier metal 5 directly under the straight bump 16 is over-etched, as shown in FIG. 2(c). There was a problem in that the aluminum pad 3 was etched and the etching solution penetrated into the aluminum pad 3, etching the aluminum pad 3 and causing corrosion 3a.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, it is an object of the present invention to provide a method for manufacturing a semiconductor device that can improve the film characteristics of a resist during etching of a barrier metal under a bump after forming a bump. It is.

[0006]

A method of manufacturing a semiconductor device of the present invention includes the steps of forming bumps on a semiconductor substrate on which a barrier metal is formed and selectively etching the barrier metal. The process of forming bumps is
A negative resist is applied thickly onto a semiconductor substrate, the negative resist is overexposed, a resist pattern with a reverse tapered cross section is formed, and bumps are formed by electrolytic plating using this resist pattern as a mask. .

[0007]

[Operation] According to the structure of the present invention, a negative resist is applied thickly to a semiconductor substrate on which a barrier metal is formed, and this negative resist is overexposed to form a resist pattern with a reversely tapered cross section. By forming bumps by electrolytic plating using a resist pattern as a mask, it is possible to improve the film characteristics of the resist during subsequent selective etching of the barrier metal.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a step-by-step sectional view showing a method of manufacturing a semiconductor device according to the present invention. First, as shown in FIG. 1(a), after forming an insulating film 2, an aluminum pad 3, and a protective film 4 on a silicon substrate 1, for example, Ti,
Pt, W, Pd, etc. are deposited to a thickness of 5,000 to 8,000 Å and
A barrier metal 5 consisting of three layers is formed.

Next, a negative type thick film resist is applied to a thickness of 15 to 20 μm. Then, during pattern formation, the exposure time is made longer than usual (overexposure) so that the cross-sectional shape of the resist 7 becomes inversely tapered as shown in FIG. 1(b). Next, by electrolytically plating with an Au electrolytic plating solution using the resist 7 as a mask, the cross-sectional shape of the bump 6 after Au plating is as shown in FIG. 1(c).
As shown in the figure, it becomes a forward taper.

Thereafter, the resist 7 is removed, and a resist 8 patterned by photolithography is formed for etching the barrier metal 5 (see FIG. 1).
d) ). Then, the barrier metal 5 is selectively etched to remove the resist 8 (FIG. 1(e)).

As described above, according to this embodiment, by making the bump 6 have a forward tapered cross-sectional shape, the film characteristics of the resist 8 (FIG. 1(d)) are good, and the resist 8 extends to the bottom of the bump 6. The bumps 6 are sufficiently covered, preventing over-etching of the barrier metal 5 directly under the bumps 6, and the contact area between the bumps 6 and the barrier metal 5 is sufficiently wide, so that the adhesive strength of the bumps 6 is improved. Furthermore, defects such as corrosion of the aluminum pad 3 due to the etching liquid are eliminated, and yield and reliability are improved.

0012

[Effects of the Invention] The method for manufacturing a semiconductor device of the present invention is to apply a thick negative resist onto a semiconductor substrate on which a barrier metal is formed, overexpose the negative resist, and form a resist pattern with a reversely tapered cross section. By forming bumps by electrolytic plating using this resist pattern as a mask, it is possible to improve the film characteristics of the resist when selectively etching the barrier metal afterwards. As a result, over-etching of the barrier metal directly under the bump can be prevented, and the contact area between the bump and the barrier metal is also sufficiently widened, improving the adhesive strength of the bump. Furthermore, defects such as corrosion of the aluminum pad due to the etching liquid are eliminated, improving yield and reliability.

[Brief explanation of the drawing]

FIG. 1 is a step-by-step sectional view showing a method for manufacturing a semiconductor device according to the present invention.

FIG. 2 is a process-order cross-sectional view for explaining a conventional method of manufacturing a semiconductor device and its problems.

[Explanation of symbols]

1 Silicon substrate 5 Barrier metal 6 Bump 7 Resist

Claims (1)

[Claims] 1. A negative resist is applied thickly to a semiconductor substrate on which a barrier metal has been formed, and this negative resist is overexposed to form a resist pattern with a reversely tapered cross section. Using this resist pattern as a mask, electrolysis is performed. A method for manufacturing a semiconductor device, including the steps of forming bumps by plating and selectively etching the barrier metal.