JPS61208847A - Formation of metal wiring layer - Google Patents

Abstract

PURPOSE:To form a semiconductor integrated circuit of finer rule by forming metal wirings of a composite metal film by a sputtering method and an electron beam depositing method. CONSTITUTION:After an aluminum layer 2 formed by a sputtering method is grown on a silicon wafer, it is not exposed with atmosphere, i.e., not contacted with oxygen gas, but an aluminum layer 3 is grown by an electron beam depositing method. Then, after the aluminum layer is selectively etched to form electrode wirings, it is heat treated at approx. 450 deg.C to grow aluminum flying metal particles, thereby forming stable aluminum wiring.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming a metal wiring layer used in a circuit device.0 Prior Art Semiconductor integrated circuit devices are becoming finer and finer year by year, and multilayer metal wiring is becoming increasingly finer. Conventionally, a metal film is applied to aluminum or aluminum/silicon by electron beam evaporation or sputtering, and then unnecessary portions are removed by etching to form metal wiring.

Problems to be Solved by the Invention Looking at conventional metal wiring in relation to its formation method, in the electron beam evaporation method, the thickness of the metal film that covers the side surfaces of step portions exceeding 1 μm is thin, resulting in so-called step coverage. There was a problem with it being bad.

On the other hand, in a metal film formed by sputtering, which has relatively good step coverage and is used for multilayer wiring, the metal film in some wiring portions is damaged by subsequent heat treatment. This is due to the coarsening of flying metal particles, and as semiconductor integrated circuit devices become smaller and the metal wiring width becomes finer to about 1 to 3 μm, such defects in the metal film can lead to wire breakage. There was a problem.

The present invention is intended to solve these problems, and aims to provide fine width metal wiring without disconnection and with good step coverage.

Means for Solving the Problem In order to solve this problem, the present invention provides a method for forming metal wiring using a composite metal film consisting of a metal film formed by a sputtering method and a metal film formed by an electron beam evaporation method. The present invention provides a manufacturing method for

Effect: With this configuration, the step coverage of the stepped portion is good in the first metal film formed by sputtering, and furthermore, no defects occur in the second metal film formed by high-density electron beam evaporation. A composite metal film such as this can be obtained, and disconnection of metal wiring can be prevented. This is because a metal film formed by sputtering has a low density, and when grains are grown through subsequent heat treatment, the metal film shrinks and breaks. The density of the metal film formed by electron beam evaporation remains dense even after subsequent heat treatment. By forming metal wiring from a pile metal film made by sputtering and a metal film made by electron beam evaporation, which have different characteristics, the drawbacks of both can be compensated for.

Embodiment An embodiment of the present invention will be described with reference to FIG. 1 and the sectional view of FIG. In FIG. 1, elements such as transistors or resistors (
(not shown), then metal wiring for electrically connecting each element is formed.

That is, on the substrate 1, an aluminum layer 2 of about 0.5 μm is grown by sputtering. The internal pressure of the chamber where the silicon wafer is located is about 1.3 Pascals using the argon gas used for sputtering, and after reducing the pressure to about 10 Pascals using a vacuum pump, the aluminum layer 3 is deposited to a thickness of about 0.6 μm using electron beam evaporation. Make it grow.

After the aluminum layer 2 is grown by sputtering on silicon, the aluminum layer 3 must be grown by electron beam evaporation without exposing it to the atmosphere, that is, without exposing it to oxygen gas. This is because the surface of aluminum oxidizes when exposed to oxygen gas, increasing electrical resistance with the aluminum layer to be grown next. It is better to form a film by sputtering and then continuously grow an aluminum layer by electron beam evaporation in the same chamber. The argon gas used in the sputtering method is an inert gas, does not adsorb to the silicon wafer, and the reduced pressure required for the electron beam evaporation method can be easily obtained.

After that, the aluminum layer is selectively etched to form electrode wiring, and then heat-treated at about 450"C.
The flying metal particles of aluminum are grown to form stable aluminum wiring. The density of aluminum wiring formed by sputtering method is about 2.5 g/cl, and the density of aluminum wiring formed by electron beam evaporation method is about 2.5 g/cl.
It is 7g/-. The density of aluminum metal is approximately 2.7
97-, the aluminum layer 2 formed by sputtering has many minute cavities inside, and when metal particles are grown by heat treatment, the density of aluminum increases.
Approximately 2. As a result, a cavity of about 0.5 to 1 μm was formed in the aluminum film, which caused defects in the aluminum wiring.

On the other hand, by using the aluminum layer 3 made by electron beam evaporation, whose density does not change due to heat treatment, together with the aluminum layer 2 made by sputtering, the cavities in the aluminum layer 2 made by sputtering can be kept small. Disconnection due to heat treatment of aluminum wiring will no longer occur.

As shown in Figure 2, after growing an aluminum layer of about 0.3 μm by sputtering, then growing an aluminum layer of about 0.4 μm by electron beam evaporation, and then growing an aluminum layer of about 0.4 μm by sputtering. If the aluminum wiring is grown to a thickness of .3 .mu.m to form an aluminum wiring having a total thickness of about 1 .mu.m, the poor step coverage of the aluminum layer by electron beam evaporation can be compensated for, and the overall thickness of the wiring layer at the stepped portion can be increased. In this way, the wiring layer may be formed by repeating the sputtering method and the electron beam evaporation method. In addition, although an example of aluminum wiring was shown, aluminum/silico y (1w
t%), wiring using an alloy such as aluminum/silicon/copper may be used.

This multilayer wiring is formed by repeating sputtering and electron beam evaporation, but it may also be formed using alloys or metals with different components.

Effects of the Invention As described above, according to the present invention, step coverage is good, and even if fine pattern metal wiring is performed, no damage or disconnection occurs due to heat treatment of the metal wiring, and a semiconductor integrated circuit with finer rules is realized. You can get the effect that you can.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of a device obtained by a method of manufacturing a semiconductor device according to an embodiment of the present invention. 1... Silicon substrate, 2... Aluminum layer formed by sputtering method, 3... Aluminum layer formed by electron beam evaporation method. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Figure 2

Claims (1)

[Claims] A method for forming a metal wiring layer, comprising the steps of forming a first metal film using a sputtering method and forming a second metal film using an electron beam evaporation method.