JPH01143236A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce the etching rate of Ti significantly and avoid over-etching into a foundation layer caused by the variation in etching of wiring metals and obtain satisfactory windings by a method wherein Ar gas and oxygen gas is mixed and ion milling is carried out. CONSTITUTION:A second layer wiring metal 6 is etched by ion milling with Ar gas until a Ti thin film 5 which is a foundation begins appearing by using a second layer wiring pattern 7 as a mask. At that time, the second layer wiring metal 6' is left on the tapered part of the edge of a first layer wiring. Then ion milling is carried out with 1:1 mixed gas of Ar gas and oxygen gas to remove all the second layer wiring metal 6 except the part under the second layer wiring pattern 7. Then the Ti thin film 5 is removed by mired solution of fluoric acid and water to form a second layer wiring 8. By replacing the Ar gas with mixed gas of Ar gas and oxygen gas, the etching rate of Ti is extremely lowered but the etching rate of Au is not.

Description

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

2. Description of the Related Art In recent years, semiconductors have progressed more and more, and LSIs with high integration and high speed operation have been developed. In LSIs that require high-speed operation, not only the high-speed performance of the device but also delays due to wiring resistance are a major problem, and in order to reduce the wiring resistance, it is essential to increase the wiring film thickness.

In particular, in GaAs ICs capable of ultra-high-speed operation, thick film A
U wiring is mainly used, and ion milling equipment is often used for etching Au to form wiring patterns.

Part 3 (2) is a cross-sectional view of a manufacturing process for explaining a conventional manufacturing method of a two-layer wiring forming process using ion milling. In FIG. 3, 11 is a semiconductor substrate on which an element is formed, 12 is a first layer wiring, 13 is an interlayer insulating film, 14 is a contact hole, 16 is a second layer wiring metal, 16 is a second layer wiring pattern, and 17 is a second layer wiring pattern. It is a two-layer wiring.

On the semiconductor substrate 11 on which the elements are formed, the first layer wiring 12 is formed of, for example, Ti/Au (soo/5ooo).
a). Next, the interlayer insulating film 13, for example, a silicon nitride film, is
A contact hole 14 for contact between the first layer wiring and the second layer wiring is formed (b). After that, a second layer wiring metal 15, for example T j /Au, is applied to the entire surface.
A desired second layer wiring pattern 16 is formed using a photoresist (c). Next, using the second layer wiring pattern 16 of the photoresist as a mask, Au and Ti other than the second layer wiring pattern 16 are vertically etched by Ar gas ion milling.
Layer wiring 17 is formed (d).

Problems to be Solved by the Invention In the wiring manufacturing method as explained in FIG. 3, when etching the second wiring metal by ion milling, as shown in FIG. Due to the step difference in the insulating film, the etching of the second-layer wiring metal in the tapered part is slower than in the other flat parts, and even when the second-layer wiring metal in the flat part is removed, the second-layer wiring metal remains in the taper part. Oh dear,
In order to remove part of the second layer wiring metal from the taper, it is necessary to add additional etching, and as shown in Figure 4, in order to completely etch the second layer wiring metal from part of the taper. However, there was a problem in that the flat portion was over-etched and the interlayer insulating film was etched.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides that Ti is applied over the entire surface of the substrate.
a step of forming a thin film, a step of forming a wiring metal over the entire surface of the Ti, a step of forming a desired wiring pattern,
Using the wiring pattern as a mask, etching the wiring metal by ion milling in Ar gas until a part of the Ti thin film is exposed, and etching the wiring metal other than the wiring pattern by mixing oxygen gas with Ar gas and ion milling. This process consists of a step of etching the wiring metal and a step of removing Ti other than the wiring pattern portion.

Effects of the present invention With the above-described configuration, the etching rate of Ti is extremely reduced by mixing Ar gas and oxygen gas and performing ion milling, and over-etching of the underlying layer due to variations in etching of wiring metal is prevented, resulting in good etching. wiring.

Embodiment FIGS. 1A to 1F are schematic cross-sectional views of manufacturing steps showing an embodiment of the method for manufacturing a semiconductor device of the present invention. In FIG. 1, 1 is a semiconductor substrate, 2 is a first layer wiring, 3 is an interlayer insulating film, and 4 is a semiconductor substrate.
5 is a contact hole, 5 is a Ti thin film, 6 is a second layer wiring metal, 7 is a second layer wiring pattern, and 8 is a second layer wiring.

On the semiconductor substrate 1 on which elements are formed, first layer wiring 2, for example, 5,001,5000 T i /A u are formed (a)
. Next, an interlayer insulating film 3 such as a silicon nitride film is deposited by 7,000 layers, and a contact hole 4 for contact between the first layer wiring and the second layer wiring is formed (b). Then the entire surface is T.
A thin film 5 and a second layer wiring metal 6, such as Au, are each formed by sputter deposition at 6oA and 8,000 people, and a desired second wiring pattern 7 is formed with photoresist (
c). Next, using the photoresinut second layer wiring pattern 7 as a mask, the second layer wiring metal 6 is etched by ion milling with Ar gas until the underlying Ti thin film 5 begins to be exposed. At this time, the second layer wiring metal 6' remains in a portion of the taper of the first layer wiring edge (d). Next, ion milling is performed using a 1:1 mixed gas of Ar gas and oxygen gas to remove all the second layer wiring metal 6 other than the second layer wiring pattern 7 (
e). Next, the Ti thin film 6 is removed using a mixed solution of hydrofluoric acid and water to form the first layer wiring 2 (see below).

In this example, when the Ti thin film starts to be exposed, by changing the ion milling gas from Ar gas to a mixed gas of Ar gas and oxygen gas, the Ti thin film can be removed as shown in Fig. 2.
The etching rate of A is extremely slow from % to A.
The etching rate of u does not decrease so much, and is only about . In particular, if the mixing ratio of Ar gas and oxygen gas is Ar:oxygen=1:1 to 3:2, the selectivity of Au and Ti will be 3 to 4 times higher than when only Ar gas is used. This is caused by oxygen.
This is due to the fact that it has become oxidized and is less susceptible to etching.

The selection ratio between Ti and Au increases due to the oxygen gas mixture, and variations occur in the etching of the second layer wiring metal at parts of the taper. is not removed and does not etch the underlying layer.

In this embodiment, a two-layer wiring process has been described, but the present invention is not limited to this, but is effective for all wiring processes such as one-layer wiring and three-layer wiring. In addition, in this embodiment, A
Although u is used, the wiring metal is not limited to this, and other wiring metals may be used.

Effects of the Invention As described above, according to the present invention, by mixing A4 gas and oxygen gas and performing ion milling, the etching rate of Ti is extremely reduced, and over-etching of the underlying layer due to variations in etching of wiring metal can be avoided. It is possible to prevent this and obtain good wiring.

[Brief explanation of the drawing]

FIG. 1 is a process cross-sectional view showing a method for manufacturing a semiconductor device according to an embodiment of the present invention, FIG. 2 is a characteristic diagram showing the dependence of etching rate on oxygen gas mixture ratio, and FIG. 3 is a diagram showing a conventional manufacturing method. FIG. 4 is a process cross-sectional view showing problems in the conventional manufacturing process. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 6... Ti thin film, 6... Wiring metal, 7... Wiring pattern, 8... Wiring. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure/lFt Sungai I λ Somiri 2F" No. No. +i Figure 2 Oxygen power/sumeshi ratio C% Figure 3

Claims (2)

[Claims] (1) Step of forming a Ti thin film on the entire surface of the substrate, and
A step of forming a wiring metal on the entire surface of the thin film, a step of forming a desired wiring pattern, and using the wiring pattern as a mask, ion milling the wiring metal in Ar gas until a part of the Ti thin film is exposed. The etching process and
A method for manufacturing a semiconductor device, comprising: mixing Ar gas with oxygen gas and etching the wiring metal other than the wiring pattern portion by ion milling; and removing Ti other than the wiring pattern portion. (2) The method for manufacturing a semiconductor device according to claim 1, wherein the mixing ratio of Ar gas and oxygen gas is 1:1 to 2:1.