JPS62142334A - Formation of metallic pattern - Google Patents

Abstract

PURPOSE:To make the inclination of an etching plane of an SiO2 film gentle by effecting a first etching to such degree that the etching reaches the middle of a layer and subjecting a photoresist film to a heat treatment to expand an opening of the photoresist, followed by the second etching. CONSTITUTION:On an SiO2 film 2 formed on a GaAs epitaxial wafer 1, a resist film 4 having an opening 3 is formed. Next, the etching of such degree that it reaches the middle of a layer is performed. After that, the wafer is subjected to a heat treatment of 130 deg.C for 30min to shrink the resist film 4 and to expand the opening 3. Then the etching of the SiO2 film is carried out again, so that an etching plane of the SiO2 film becomes to show an extremely gentle inclination. Subsequently, by depositing an Mo metal 5 over the whole surface of the wafer by vacuum vapor deposition, there is no gap produced between the SiO2 film 2 and the Mo metallic film 5 formed on the GaAs epitaxial wafer 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming metal patterns such as electrode wiring of semiconductor devices.

[Conventional technology]

Conventionally, when forming metal patterns for electrode wiring in diodes, transistors, integrated circuits, etc., a photo-etching method is used to photo-etch an insulating film and a metal film, or a lift-off method is used, which utilizes resist dissolution. However, the lift-off method is superior in terms of process reduction and pattern shape accuracy, and is widely used.

The present invention relates to an improvement in the method of forming metal patterns by the beam lift-off method, and hereinafter, GaAs with Mo metal as the 7-Yotkey metal and Al metal as the bonding metal.
Explanation will be given using a rear diode as an example.

FIG. 2 is an explanatory diagram showing an example of a conventional metal pattern forming method.

5i0 with a thickness of about 6,000 angstroms (X) was deposited on GaAs epitaxial Ueno-1 by vacuum sputtering.
A resist film 4 having an opening 3 having a diameter of about 5 micrometers (μm) is formed on the 5i02 film 2 by photolithography (FIG. 2(a)). next,
The resist film 4 is photo-etched with ASI 02 m 2 in a mass 1;
A part of the GaAs epitaxial wafer 1 is exposed (FIG. 2(b)). Next, a Mo metal film 5 is deposited on the entire surface of the wafer by vacuum evaporation (FIG. 2(c)), and the resist film 4 is dissolved in an acetone solution to remove the Mo metal film 5 deposited on the resist film 4 together with the resist film 4. remove. (
(Fig. 2(d)) Al metal is deposited on the entire surface of the GaAs epitaxial wafer 1 on which the Mo metal film 5 of the Shore 1 key metal is formed in a predetermined region by vacuum evaporation method, and the deposited Al metal is removed in a predetermined area by photoetching method. When parts other than pattern 6 are removed (Figure 2, tel).

The formation of the basic part of the Schottky barrier diode is completed.

[Problem that the invention seeks to solve]

In the conventional method as described above, when etching of the Sioz film 2 is continued until the eaves of the resist necessary for lift-off is secured, the etching progresses isotropically at the beginning, but under the resist, the etching progresses in an isotropic manner. As the etching progresses, the etching speed becomes slower, so as shown in Figure 2 (bl),
The etched surface of the 5i02 film 2 has a steep slope with respect to the wafer surface, and a gap 7 is formed between the Mo metal film 5 formed on the GaAs epitaxial wafer 1 and the Sioz film 2 as shown in FIG. There was a problem that it was easy to occur.

This gap causes deterioration of the characteristics due to oxidation of the exposed portion of GaAs, and also causes the Al metal film 6 of the bonding metal to come into contact with the GaAs surface on which the Mo metal film 5 should originally be formed, resulting in deterioration of the Schottky characteristics. bring.

At the same time, it is also a factor that causes large step differences to occur in the Al metal film 6, and gaps between steps in the wiring on the surface of the Al metal film 9.

The present invention was made to solve the above problems.
It is an object of the present invention to provide a method that does not create a gap between the Mo metal film 5 and the 5i02 film 2.

[Means for solving problems]

In the method of the present invention, the first etching is performed to reach the middle of one layer, the photoresist film is heat-treated to enlarge the photoresist opening, and the etching is performed again, thereby making the slope of the etched surface of the 5i02 film gentle. This is the way to do it.

〔Example〕

FIG. 1 is an explanatory diagram showing the metal pattern forming method of the present invention.

S i0 formed on GaAs epitaxial wafer 1
2. A resist film 4 having an opening 3 is formed on the film 2 (FIG. 1(a)). Next, the SiO2 film 2 in the opening 3 is etched to reach the middle of the layer (Fig. 1(b)).
)).

Thereafter, heat treatment is performed for 930 minutes at 130° C. while the wafer is open, thereby shrinking the resist film 4 and enlarging the opening 3 (FIG. 1(C)). After enlarging the opening 3, etching the 5i02 film 2 again results in 5i0
2 The etched surface of the film 2 has a very gentle slope (FIG. 1(d)).

Next, when the Mo metal film 5 is deposited on the entire surface of the wafer by vacuum evaporation, there is no gap between the Mo metal film 5 formed on the GaAs epitaxial wafer 1 and the 5i02 film 2 (Fig. 1(e)). ).

After this, as in the conventional case, the acetone solution telesist film 4 is dissolved, and the resist film 4 and the Mo attached thereon are dissolved.
The metal film 5 is removed (see FIG. 1(f)).

Al covering the Mo metal film 5 left by photoetching
A metal pattern 6 is formed (FIG. 1(g)).

〔Effect of the invention〕

As explained above, 1 According to the present invention, 9 For example, in the electrode formation of a Schottky barrier diode, the problem of a gap being formed between the Schottky metal and the 5i02 film, which causes deterioration of characteristics, is solved, and the yield is improved. This also has the effect of improving reliability.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the metal pattern forming method of the present invention,
FIG. 2 is an explanatory diagram showing an example of a conventional metal pattern forming method. 1...GaAs epitaxial Unino, 2...5
i02 film, 3... opening, 4... resist film, 5...
...MO metal film, 6...Al metal film. Patent applicant: New Japan Radio Co., Ltd. No. 1 [Australia]

Claims (1)

[Claims] A step of forming an insulating protective film on the substrate, a step of forming a photoresist film corresponding to a pattern to be formed on the protective film, and a step of performing etching to reach the middle of the layer of the protective film at the photoresist opening. , enlarging the photoresist opening by heat-treating the photoresist film;
The present invention is characterized by comprising the steps of performing etching to reach the bottom of the protective film layer in the enlarged photoresist opening, and forming a metal pattern by a lift-off method in the region from which the protective film of the enlarged photoresist opening has been removed. A method for forming a metal pattern.