JPH0513382A - Etching method - Google Patents

Abstract

PURPOSE:To avoid the occurrence of after corrosion by a method wherein the gas as an etchant is to be largely composed of germanium tetrachloride or germanium tetrabromide and then a surface layer is etched away while being decomposed on an eutectic alloy in the etching step of a metallic thin film largely composed of aluminum. CONSTITUTION:A BPSG film 12 is formed on a silicon substrate 11 next an Al-Si-Cu film 13 is grown on the film 12 and then a photoresist 14 is pattern- formed. Next, the whole body is fed to a reaction chamber to be etched away using CeCl4 and Cl4 base mixed gas. At this time, about 4000Angstrom /min of etching rate for the Al-Si-Cu film 13, about 0.4-8.8 of selection ratios respectively to a resist and a BPSG are specified to bear the basic characteristics. At this time Al-Ge euteclic alloy 16 is formed. Through these procedures, even if Cl2 constituent reacts to any atmospheric water content to produce HCl, any after corrosion shall not occur since the sidewall surface of the Al-Si-Cu film 13 is previously eutectic alloyed.

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 an etching method for etching a metal thin film containing at least aluminum as a main component.

[0002]

2. Description of the Related Art In the prior art, various kinds of gases have been proposed and used for etching a metal thin film containing aluminum as a main component. Specifically, chlorine-based compounds are SiCl ₄ , BCl ₃ , Cl ₂ and CHCl ₃ , and bromine-based compounds are BBr ₃ (JP-A-54-59880), B
r2, HBr, etc. (JP-A-64-30227). In the conventional method using these gases, a gas mixed at an arbitrary ratio is used as an etchant and introduced into a vacuum container, and plasma processing is performed to obtain a good processed shape. In addition, as a measure against after-corrosion,
An etching apparatus having at least two plasma reaction chambers was used, and at least the metal thin film containing aluminum as a main component was etched using the photoresist pattern as a mask in the first reaction chamber, and then the semiconductor substrate was transported in vacuum. 180C as a post-treatment in the second reaction chamber
There is a method of applying heat treatment using the above temperature (JP-A-64-15932), a method of performing ashing with a mixed gas of O ₂ gas and a fluorine-based gas, and the like.

For example, a silicon substrate 1 as shown in FIG.
1, BPSG film 12 is formed, and then the film thickness is 0.8 μ.
The Al-Si (1%)-Cu (0.5%) film 13 of m is grown by the sputtering method. After that, the photoresist film 14 having the pattern formed by the known photolithography technique was subjected to ordinary RIE plasma etching in a BCl ₃ gas system.

Then, the residual chlorine content 15 always adheres to the photoresist 14 and the side wall surface of the Al-Si-Cu film 13 which is the wiring pattern. After that, ashing is performed at an appropriate temperature or a heat treatment is applied to reduce the chlorine content, prevent the reaction with moisture in the atmosphere to form HCl, and suppress after-corrosion.

[0005]

However, in the above-mentioned structure, since chlorine basically remains on the side wall surface after etching, even if any post-treatment is performed, a metal thin film containing at least aluminum as a main component. The chlorine once adsorbed once cannot be completely removed, and it combines with moisture in the atmosphere to form HCl and dissolves aluminum, so the after-corrosion countermeasure is insufficient (when left in the atmosphere for 3 days or more, etc. ).

In view of the above problems, the present invention performs etching while changing at least the surface of a metal thin film containing aluminum as a eutectic alloy into a eutectic alloy so that chlorine remains on the sidewall surface after etching. The present invention provides an etching method in which after-corrosion is not fundamentally generated.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention, when etching at least a metal thin film containing aluminum as a main component, performs etching while changing the surface layer of the metal thin film, and further the surface thereof. The etching method is characterized in that the layer forms a eutectic alloy.

The eutectic alloy is an AL-Ge system,
The etching method is characterized in that the etchants forming it are GeCl ₄ (germanium tetrachloride) and GeBr ₄ (germanium tetrabromide), which are Ge-bearing gases.

[0009]

The present invention has the above-described structure, and in the etching of a metal thin film containing at least aluminum as a main component, the gas system uses GeCl ₄ or GeBr ₄ which is a gas bearing Ge, so that the surface of the metal thin film is Etching is performed while forming a crystalline alloy and changing the quality, that is, while forming an AL-Ge-based eutectic alloy, in which a chlorine component attaches to at least a metal thin film wiring pattern containing aluminum as a main component and reacts with moisture. Even if it becomes HCl, at least the side wall of the metal thin film wiring pattern containing aluminum as a main component is protected by the Al-Ge eutectic alloy, so that aluminum is not corroded.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a schematic diagram of an etching reaction chamber (RIE) for carrying out the present invention. In FIG. 3, 1 is a wafer to be etched, 2 is a chamber,
3 is an upper electrode, 4 is a lower electrode, 5 is a lower pressing SUS plate, 6 is a gas inlet, 7 is a groove for cooling water, and 8 is an upper SU.
An S plate, 9 is a gas exhaust port, and 10 is an RF power source.

In the etching method of the present invention configured as described above, its operation will be described below by showing the first embodiment thereof.

A BPSG film 12 is formed on a silicon substrate 11.
Is formed, and then Al-Si (1%)-having a film thickness of 0.8 μm is formed.
The Cu (0.5%) film 13 is grown by the sputtering method. After that, the photoresist film 14 is patterned by a known photolithography technique.

Therefore, the sample shown in FIG. 1 was placed in the apparatus shown in FIG. 3, the pressure was 60 mTorr, the RF power was 400 W, the electrode temperature was 70 ° C., the upper electrode gap and the lower electrode gap were 85 mm, and the GeC.
l was etched at ₄ and Cl ₂ gas mixture system.

The results are shown in Table 1.

[0015]

[Table 1]

In specific examples (1) to (3), Al-Si-Cu is used.
The etching rate of the film and the selection ratio with respect to the resist and the BPSG film are shown. The etching rate of the Al-Si-Cu film is about 4000 A / min, the selection ratio is about 2.4 for the resist, and about 8.8 for the BPSG.

On the other hand, GeCl ₄ in the first embodiment is used.
By the etching with a mixture system of Cl ₂ and Cl ₂ gas, an Al—Ge eutectic alloy 16 is formed. This results in Cl ₂
Even if the component reacts with moisture in the atmosphere to generate HCl, the side wall surface of the Al-Si-Cu film that is the wiring pattern is Al-
Since it is a eutectic alloy of Ge, after-corrosion does not occur.

A second embodiment of the present invention will be described below with reference to the drawings. Similarly, the sample shown in FIG.
Installed in the device, pressure 60mTorr, RF power 4
00W, electrode temperature 70 ℃, upper and lower electrode distance 85m
m, GeBr ₄ and Cl ₂ gas mixture system was used for etching.

The results are shown in Table 2.

[0020]

[Table 2]

Specific examples (4) to (6) are Al-Si-Cu.
The etching rate of the film and the selection ratio with respect to the resist and the BPSG film are shown. The etching rate of the Al-Si-Cu film is about 4200 A / min, the selection ratio is about 4.8 for the resist, and about 11.4 for the BPSG.

On the other hand, GeBr ₄ in the second embodiment
By the etching with a mixture system of Cl ₂ and Cl ₂ gas, an Al—Ge eutectic alloy 16 is formed. This results in Cl ₂
Even if the component reacts with moisture in the atmosphere to generate HCl, the side wall surface of the Al-Si-Cu film that is the wiring pattern is Al-
Since it is a eutectic alloy of Ge, after-corrosion does not occur.

As described above, at least the surface of the metal thin film containing aluminum as the main component is etched while forming a eutectic alloy of Al-Ge to protect the side wall of the wiring pattern with the eutectic alloy film, so that residual chlorine is removed. H reacts with water
Even if Cl is generated, fundamentally no after-corrosion occurs.

In the first embodiment, GeCl ₄
And it was a mixed gas system of Cl _2, these CHCl _3, N
It goes without saying that the same effect can be obtained by adding ₂ .

In the second embodiment, GeBr ₄ and Cl _{2 are used.}
However, it is needless to say that the same effect can be obtained by adding CHCl ₃ and N _{2 to} these.

[0026]

As described above, according to the present invention, when etching a metal thin film containing at least aluminum as a main component, the etchant is GeCl ₄ which is a gas bearing Ge.
(Germanium tetrachloride) and GeBr ₄ (germanium tetrabromide) are used to perform etching while altering the surface layer, and by forming a eutectic alloy on the surface layer, the sidewall surface after the etching is formed. It is possible to provide an etching method in which after-corrosion is not fundamentally generated even when chlorine remains.

[Brief description of drawings]

FIG. 1 is a wafer for etching in a gas system of the present invention.
FIG.

FIG. 2 is a wafer cross-sectional view of etching in a conventional gas system.

FIG. 3 is a schematic diagram of an RIE type etching chamber in an embodiment of the present invention.

[Explanation of symbols]

1 wafer 2 chambers (Al) 3 Upper electrode 4 Lower electrode 5 Lower presser plate SUS plate 6 gas inlet 7 Cooling water groove 8 Upper SUS plate 9 gas exhaust port 10 RF power supply 11 Silicon substrate 12 BPSG film 13 Al-Si-Cu film 14 Resist film 15 Residual chlorine 16 Al-Ge eutectic alloy film

Continued front page    (72) Inventor Masafumi Kubota             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd.

Claims (4)

[Claims] 1. An etching method, characterized in that, when a metal thin film containing at least aluminum as a main component is etched, the surface layer is etched while being altered. 2. The etching method according to claim 1, wherein when the metal thin film containing at least aluminum as a main component is etched, the surface layer is etched while forming a eutectic alloy. 3. The etching method according to claim 2, wherein the eutectic alloy is an AL-Ge system, and the etchant forming the eutectic alloy is a Ge-bearing gas. 4. The Ge-bearing gas is GeCl.
_4. The etching method according to claim 3, wherein the etching method is ₄ (germanium tetrachloride) or GeBr ₄ (germanium tetrabromide).