Ohmic contact to semiconductor devices and method of...

Details Ohmic contact to semiconductor devices and method of... Ohmic contact to semiconductor devices and method of...

1999-06-03

2001-11-20

Whitehead, Jr., Carl (Department: 2822)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S606000, C438S608000, C438S685000, C438S686000

Reexamination Certificate

active

06319808

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an ohmic contact to semiconductor devices and its manufacturing method, particularly an ohmic contact to p-type gallium nitride and the method of manufacturing the same.
2. Description of Prior Art
In recent years, gallium nitride (hereinafter referred to as GaN) has been broadly used in the fabrication of short-wavelength light-emitting diodes, laser diodes, photo-detectors and microelectronic components, etc. Good ohmic contact is especially important to commercialized light-emitting devices. Currently, the specific contact resistance for n-type GaN has been reduced to about 10
−4
~10
−8
&OHgr;·cm
2
. As for p-type GaN, however, the specific contact resistance can only attain 10
−2
~10
−3
&OHgr;·cm
2
, much higher than that for the contact to n-type GaN. Such a high interface resistance markedly affects the performance and reliability of these devices. Therefore, it is an important issue for the scientists and engineers to lower the specific contact resistance of the contact to p-type GaN. Until now, most conventional methods to manufacture contacts to p-type GaN deposit the metals directly. For example, in U.S. Pat. No. 5,652,434, the Nichia Chemical Industrial Company uses Ni or Ni/Au in its light-emitting diodes (LED) to form a contact. In addition, in U.S. Pat. No. 5,739,554, Cree Research Company uses Ti/Au, Ti/Ni or Ni/Au in its LED to form contact. But neither described the specific contact resistance of the contacts. In other references, other kinds of metals are disclosed, such as Au, Ni, Ti, Pd, Pt, W, WSix, Ni/Au, Pt/Au, Cr/Au, Pd/Au, Au/Mg/Au, Pd/Pt/Au, Ni/Cr/Au, Ni/Pt/Au, Pt/Ni/Au, Ni/Au-Zn, Ni/Mg/Ni/Si, etc. However, the specific contact resistance of the above metal contacts can only attain 10
−2
~10
−3
cm-
−2
, which is higher than 10
−4
cm
−2
generally required for optoelectronic devices. In addition, almost all of the above metals do not exhibit ohmic behavior.
SUMMARY OF THE INVENTION
Accordingly, the object of this invention is to provide an ohmic contact to semiconductor devices and its manufacturing method by which the interface resistance of ohmic contact is lowered so as to improve the performance and reliability of semiconductor devices.
This invention provides a new semiconductor manufacturing process which can form an ohmic contact to p-type GaN with a low interface resistance for application in the fabrication of GaN-based devices.
The manufacturing method of this invention forms a film, which includes transition metal and noble metal, on the semiconductor substrate. Then, the film is heat-treated and oxidized to obtain an ohmic contact with a low specific contact resistance. So formed, an ohmic contact can meet the requirement of an optoelectronic device; that is, the specific contact resistance of the ohmic contact is lower than 10
−4
cm-
−2
.


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