Ohmic electrode for n-type cubic boron nitride and the process f

Details Ohmic electrode for n-type cubic boron nitride and the process f Ohmic electrode for n-type cubic boron nitride and the process f

1991-05-28

1993-02-16

LaRoche, Eugene R.

Active solid-state devices (e.g., transistors, solid-state diode

Specified wide band gap semiconductor material other than...

437184, 437189, 257743, 257744, H01L 21283

Patent

active

051875608

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND

1. Field of the Invention
The present invention relates to a process for producing an ohmic electrode for n-type cubic boron nitride.
2. Prior Art
Hitherto, for producing an electrode for a semiconductor cubic boron nitride (hereafter referred to as "cBN"), a silver paste is used as described in Appl. Phys. Lett., vol 53 (11), Sep. 12, 1988, pp. 962.about.964, but the actual technique for producing an ohmic electrode for a semiconductor cBN has not yet been developed at present.
In a conventional process for producing an electrode using a silver paste, the contact resistance is large and also the resistance characteristics of the passing electric current are unstable. Furthermore, a silver paste displays a poor wetting property to cBN, in addition to the problem the adhesive strength is weak, whereby the electrode is liable to be separated from the crystal. Accordingly, it is difficult to produce a semiconductor using a cBN crystal.
On the other hand, an ohmic electrode for p-type cBN is described in Japanese patent application No. 1-276346.


SUMMARY OF THE INVENTION

In such circumstances, as the result of investigations for establishing a technique of forming an electrode having a sufficient adhesive strength to a semiconductor cBN with a good low resistance, the present inventors have succeeded in accomplishing the present invention.
One object of the present invention is to provide an even n-type cBN electrode having good ohmic characteristics which are effectively utilized, e.g., for the preparation of a semiconductor device using a cBN crystal.
Other objectives and effects of the present invention will be apparent from the following description.
The present invention relates to an ohmic electrode for n-type cBN, and also relates to a process for producing an ohmic electrode for n-type cBN, which comprises the following steps; providing at least one thin alloy film selected from Au-Si alloy, Au-Ge alloy and Au-Si-Ge alloy, the weight ratio of Si, Ge and Si plus Ge being 0.1 to 35% by weight, on n-type cBN; providing a thin film of at least one metal selected from Ni, Cr, Mo and Pt on the thin alloy film; and subjecting the n-type cBN having the thin films thus provided to a heat treatment in an inert gas or in a vaccum at a temperature ranging from 350.degree. C. to 600.degree. C. Concerning the inert gas, N.sub.2, Ar and a mixture of Ar and N.sub.2 are preferable.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view showing an ohmic electrode produced by the process of the present invention; and
FIG. 2 is a graph showing the measurement results of the current voltage characteristics of n-type cBN using the ohmic electrode produced in the example of the present invention.


DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1 showing a schematic sectional view of the electrode produced by the process of the present invention, one embodiment of the article and the process for producing an ohmic electrode according to the present invention is explained.
This invention provides the ohmic electrode for n-type cBN 1, on which the first thin film 2 of at least one alloy selected from Au-Si alloy, Au-Ge alloy and Au-Si-Ge alloy is coated, and the second thin film of at least one metal or alloy selected from Ni, Cr, Mo and Pt is coated.
Further, the process of the present invention may comprise the following steps: one, providing at least one thin film 2 of an alloy selected from Au-Si alloy, Au-Ge alloy and Au-Si-Ge alloy onto the surface of an n-type cBN crystal 1; two, providing at least one thin film 3 of a metal selected from Ni, Cr, Mo and Pt onto the thin film 2, and three, heat-treating the n-type cBN having the aforesaid thin film 2 and the thin film 3 at a temperature ranging from 350.degree. C. to 600.degree. C. in an inert gas atmosphere or in a vacuum.
It is preferable to conduct the heat-treating at a temperature ranging from 400.degree. C. to 550.degree. C. in an inert gas atmosphere or in a vacuum.
Conventionally, materials displaying ohmic properties at

REFERENCES:
patent: 3850688 (1974-11-01), Halt
patent: 4831212 (1989-05-01), Ogata et al.
patent: 5006914 (1991-04-01), Beetz, Jr.
patent: 5057454 (1991-10-01), Yoshida et al.

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