JPH04287973A - Manufacture of compound semiconductor device - Google Patents

Abstract

PURPOSE:To stably form a heat resistant ohmic electrode having a low resistance thereof itself. CONSTITUTION:After an insulating film 2 opened at a desired ohmic electrode part is formed, an Ni4/Ge5 layer is deposited on the electrode part by a lifting- off method. Then, a high melting point metal layer of W6 or the like is selectively formed on the Ge5 by a CVD method, and annealed at about 600 deg.C to form an ohmic electrode. Extraction of As at the time of heat treating can be prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a compound semiconductor device, and more particularly to a method of forming a heat-resistant ohmic electrode without using Au.

0002

2. Description of the Related Art FIGS. 4 to 6 are cross-sectional views showing steps 4 to 6 of a conventional method for manufacturing a compound semiconductor device in the order of steps. In the figures, 1 is a GaAs substrate, 2 is an insulating film, 3 is a photoresist, and 7 is an AuGe eutectic, 8 is a Ni layer, and 9 is an Au layer.

First, as shown in FIG. 4, plasma CVD (Chemical
An insulating film 2 is formed on the entire surface using a vapor deposition method, etc., and a photoresist 3 is formed using a transfer technique so that the desired drain electrode/source electrode portions are opened.
form.

Next, as shown in FIG. 5, RIE (reactive-ion etch) is performed using the photoresist 3 as a mask.
After etching the insulating film 2 by a method such as ing) and sequentially depositing AuGe eutectic 7 Ni layer 8 Au layer 9,
As shown in Figure 6, by removing the photoresist 3 with acetone or the like, a gold layer is left only on the source and drain electrodes, and heat treatment at about 400°C (hereinafter referred to as sintering) is performed to form an ohmic electrode. do.

[0005] In this method, since Au is used for the ohmic electrode portion, if Al is used for the wiring metal, Au and Al will react, so Al cannot be used for the wiring metal. Therefore, it is possible to form an ohmic electrode using only the Ni layer and the Ge layer, but since the sintering temperature is around 600°C, As dropout occurs and the resistance of the ohmic electrode itself becomes high, making it difficult to put it into practical use. .

One possible solution to this problem is to deposit a Ni layer, a Ge layer, and a high-melting point metal layer in sequence and sinter using the high-melting point metal as a cap.However, since high-melting point metals have a large stress, if they are deposited with a thickness of 1000 Å or more, the deposition process may be interrupted. The photoresist is deformed and cannot be stably formed.

[0007]

[Problems to be Solved by the Invention] As described above, it is not possible to use Al as a wiring metal in conventional ohmic electrodes, and it is difficult to form ohmic electrodes that are stable and have sufficiently low resistance using only Ni/Ge. There were problems such as not being able to.

The present invention was made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a method for manufacturing a compound semiconductor device that can form an ohmic electrode whose resistance is sufficiently low without using Au. With the goal.

[0009]

[Means for Solving the Problems] A method for manufacturing a semiconductor device according to the present invention includes the steps of: depositing an insulating film on an active layer formed on a compound semiconductor substrate; and then opening source and drain electrode portions; The method includes a step of forming a Ge/Ni layer in the opening, a step of forming a W layer on the Ge/Ni layer by W-CVD, and a step of obtaining ohmic characteristics by performing heat treatment.

0010

[Function] In this invention, since a high melting point metal layer of 1000 Å or more can be stably formed, the resistance of the ohmic electrode itself can be lowered, and As
It can also prevent it from coming off.

[0011]

[Example] Example 1. An embodiment of the present invention will be described below with reference to the drawings. Figure 1
3 are sectional views of the first to third steps showing the method of manufacturing a semiconductor device according to an embodiment of the present invention in order of steps. In the figure, 1 to 3 are the same as in Figures 4 to 6, 4 is a Ni layer, and 5 is a G
The e layer and 6 are the W layer.

[0012] As shown in FIG.
An insulating film 2 is formed on the entire surface of the As substrate 1 by a plasma CVD method or the like, and a photoresist 3 is formed by a transfer technique so that desired drain and source electrode portions are opened.

Next, as shown in FIG. 2, the insulating film 2 is etched by RIE using the photoresist 3 as a mask, and a Ni layer 4 and a Ge layer 5 are deposited.

Next, after removing the photoresist 3 with acetone or the like to leave a metal layer only on the source and drain electrodes, W-CVD is selectively applied to the Ge layer as shown in FIG. An ohmic electrode is formed by forming a layer and sintering at about 600°C.

[0015] In the above embodiment, the case where a Ni/Ge layer is used has been described, but the present invention can also be applied to a case where a Ni/In layer is used.

Further, although the case where the W layer is formed by the W-CVD method has been described, other high melting point metal layers such as a layer by the CVD method may be formed.

[0017]

As described above, according to the present invention, it is possible to stably form a high melting point metal layer with a thickness of 1000 Å or more, so the resistance of the ohmic electrode itself can be reduced.
Even if annealing is performed at a temperature higher than .degree. C., As loss can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a first step cross-sectional view showing a method for manufacturing a compound semiconductor device according to an embodiment of the present invention in order of steps.

FIG. 2 is a second step cross-sectional view showing the method for manufacturing a compound semiconductor device according to an embodiment of the present invention in order of steps;

FIG. 3 is a third step cross-sectional view showing the method for manufacturing a compound semiconductor device according to an embodiment of the present invention in order of steps;

FIG. 4 is a first step cross-sectional view showing the conventional method for manufacturing a compound semiconductor device in order of steps.

FIG. 5 is a second step cross-sectional view showing the conventional method for manufacturing a compound semiconductor device in order of steps.

FIG. 6 is a third step cross-sectional view showing the conventional method for manufacturing a compound semiconductor device in order of steps.

[Explanation of symbols]

1 GaAs substrate 2 Insulating film 3 Photoresist 4 Ni layer 5 Ge layer 6 W layer 7 AuGe eutectic 8 Ni layer 9 Au layer

Claims (1)

[Claims] 1. A step of opening source and drain electrode portions after depositing an insulating film on an active layer formed on a compound semiconductor substrate, a step of forming a Ge/Ni layer in the opening portions, and a step of forming a Ge/Ni layer in the opening portions. 1. A method for manufacturing a compound semiconductor device, comprising the steps of: forming a W layer on the /Ni layer by W-CVD; and obtaining ohmic characteristics by heat treatment.