JPS63234562A - Electrode of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the contamination of the surface of an electrode due to the diffusion of group III atoms at the time of heat treatment, and to increase the strength of wire bonding by forming a barrier layer onto an ohmic layer. CONSTITUTION:An ohmic layer 2 is shaped onto a III-V compound semiconductor substrate 1, and a barrier layer 3 and a gold layer 4 are formed onto the ohmic layer 2 in succession. The barrier layer 3 is constituted of a Ti layer 3a, an Mo layer 3b and a Ti layer 3c successively. That is, since Mo has inferior adhesive properties with Au, the Ti layers 3a, 3c having extremely excellent adhesive properties with both Mo and Au are shaped to the upper and lower sections of the Mo layer 36, and the adhesive properties of the Mo layer 3b with each of an Au layer 2c as the uppermost layer of the ohmic layer 2 and the Au layer 4 of the uppermost surface of an electrode are improved. Accordingly, the barrier layer stops the diffusion and permeation of Ga due to heat treatment, thus preventing the contamination of the surface of the electrode by group III atoms.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrode for a semiconductor device formed of a III-V group compound semiconductor.

(Prior Art) FIG. 2 is a cross-sectional view showing the structure of an electrode of a conventional semiconductor device made of a III-V compound semiconductor, for example, a semiconductor laser device made of GaAs, AJZGaAs, etc. In the figure, 1 is an N-type or P-type GaAs substrate, 2 is an ohmic layer in ohmic contact with this GaAs substrate 1, for example, a gold germanium (Au-Ge) alloy layer 2 a % nickel (Ni) layer 2 b, a gold (Au) layer 2c
It is formed by laminating layers.

Note that each metal layer of this ohmic layer 2 is formed by a vacuum evaporation method or the like, and then heat-treated to obtain good ohmic characteristics at the contact interface between the GaAs substrate 1 and the ohmic layer 2.

Furthermore, an Au wire or the like is wire-bonded to the surface of the Au layer 2C, which is the uppermost layer of the ohmic layer 2, during assembly.

(Problems to be Solved by the Invention) The conventional electrode is constructed as described above, but during the heat treatment to obtain the above-mentioned ohmic characteristics, Ga in the GaAs substrate 1 is thermally diffused into the ohmic layer 2. There were problems such as penetrating into the Au layer 2C, accumulating and oxidizing on the surface of the Au layer 2C, and reducing adhesive strength during wire bonding.

This invention was made in order to solve the above-mentioned problems, and the purpose is to prevent the electrode surface from being contaminated by heat treatment and to obtain an electrode for a semiconductor device that has high adhesive strength during wire bonding. shall be.

[Means for solving problems]

The electrode of the semiconductor device according to the present invention includes an ohmic layer formed on an IH-V group compound semiconductor substrate, and a barrier layer and a gold layer sequentially formed on the ohmic layer.

[Function] In the present invention, the barrier layer prevents diffusion and penetration of Ga due to heat treatment, thereby preventing contamination of the electrode surface by group III atoms.

〔Example〕

FIG. 1 is a sectional view showing an embodiment of the present invention.1.
2 is exactly the same as that shown in FIG. 3 is a barrier layer formed on the ohmic layer 2 by a vacuum evaporation method, and 4 is a gold layer formed on this barrier layer 3 by a vacuum evaporation method or the like. The barrier layer 3 includes Ti layers 3a and M in this order.

It is composed of a layer 3b and a Ti layer 3c.

In the electrode of the semiconductor device configured as above,
The MO layer 3b, which is a high melting point metal and has a sufficiently small diffusion coefficient for Ga, blocks Ga from diffusing from within the GaAs substrate 1 during heat treatment, and prevents Ga from further diffusing into the upper layer. However, since Mo has poor adhesion to Au, the Ti layers 3a and 3c have extremely good adhesion to both MO and Au.
M.

They are formed above and below the layer 3b to improve the adhesion between the Mo layer 3b and each of the Au layer 2c, which is the uppermost layer of the ohmic layer 2, and the Au layer 4, which is the outermost surface of the electrode.

It should be noted that although the above embodiment is a case of a GaAs substrate, the present invention can also be applied to other III-V group semiconductor substrates.

〔Effect of the invention〕

As explained above, this invention has the effect of preventing group III atoms from diffusing and contaminating the electrode surface during heat treatment by forming a barrier layer on the ohmic layer, thereby increasing wire bonding strength.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an electrode of a semiconductor device showing an embodiment of the present invention, and FIG. 2 is a sectional view of an electrode of a conventional semiconductor device. In the figure, 1 is a GaAs substrate, 2 is an ohmic layer, and 2 is a GaAs substrate.
a is an Au-Ge alloy layer, 2b is a Ni layer, 2c is an Au layer,
3 is a barrier layer, 3a is a Ti layer, 3b is an MO layer, 3c is a T layer
The i layer and 4 are Au layers. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa (2 others) Figure 1 Figure 2

Claims (2)

[Claims] (1) An electrode for a semiconductor device, characterized in that an ohmic layer, a barrier layer, and a gold layer are sequentially formed on a III-V group compound semiconductor substrate. (2) An electrode for a semiconductor device according to claim (1), wherein the barrier layer has a laminated structure in which a titanium layer, a molybdenum layer, and a titanium layer are sequentially formed.