JPS58176B2 - Electrode formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for forming ohmic electrodes and wiring in a simpler process for a semiconductor wafer having a structure in which both a P-type layer and an N-type layer of compound semiconductor gallium arsenide are exposed on one side. This invention relates to a method for forming electrodes.

Conventionally, Zn, Au-Zn alloy, Au-Be, etc. have been used for P-type gallium arsenide as ohmic contact materials for light emitting elements and high frequency devices using gallium arsenide.

In addition, for N-type gallium arsenide, AuGe-Ni-A
U, 5n-Au, etc. are used.

However, there is no effective ohmic material for both P-type GaAs and N-type GaAs, and both metals have poor adhesion to SiO2 or Al2O3, which are semiconductor protective films.

Therefore, in the P-type GaAs layer 1 as shown in FIG.
In the device provided with the GaAs layer 2, the P-type GaAs layer 1 and the N-type aAs layer 2 are exposed on one side of the semiconductor wafer by selective diffusion or selective epitaxial growth.

As a result, although the structure is such that the electrodes are formed in one evaporation and photolithography process, the ohmic electrode 3 for the P-type GaAs layer 1 and the ohmic electrode 4 for the N-type GaAs layer 2 are different.

Therefore, two photolithography steps and two vapor deposition steps were required.

Furthermore, in the device shown in FIG. 2, the P-type GaAs layer 1
A plurality of N-type GaAs regions 5 and 6 are exposed on one side, and electrodes 4A and 4B are formed on the N-type GaAs regions 5 and 6, and an electrode 3 is also formed on the P-type GaAs layer 1. A wiring 8 is provided on the electrodes 4A and 4B of the N-type GaAs regions 5 and 6 with an insulating film 7 interposed therebetween.

In the case of FIG. 2, an electrode 3 (ohmic electrode) for the P-type GaAs layer 1, electrodes 4A and 4B (ohmic electrodes) for the N-type GaAs region 5.6, and an insulating film 7.
A different metal is used from the metal of the wiring 8 which has good adhesion.

Therefore, three photolithography steps and three vapor deposition steps are required.

As is clear from the above, the methods of forming electrodes for the elements shown in FIGS. 1 and 2 both have the disadvantage of increasing the number of steps.

This invention was made in order to eliminate the above-mentioned conventional drawbacks, and involves exposing a P-type head region and an N-type region on one side of a GaAs substrate, and forming electrodes and wiring on the P-type head region and N-type region. By using a Ni-Cr alloy for the first layer, it satisfies three functions: ohmic properties for the P-type head region and N-type region, and adhesion with the protective film used for insulation. It is an object of the present invention to provide an electrode forming method that can form an electrode in two photolithography and vapor deposition steps and that can simplify the process.

Hereinafter, embodiments of the electrode forming method of the present invention will be described based on the drawings.

FIG. 3 is a diagram showing one embodiment thereof.

This figure 3 shows a high-efficiency Si-doped GaAs single-sided L.
This is an example of application to a method for forming electrodes of EDs (light emitting diodes).

First, a P-type GaAs layer 12 as a P-type region, a N-doped GaAs layer 12 as a P-type region, and a N N-type GaAs as type region
Layer 13 is exposed on one side of N+GaAs substrate 11.

Next, a PSG film of 2000 Å was formed into a protective film 1 using the CVD method.
In addition, 2000 Å of N1-Cr (Cr
20Wt/%) alloy 15, 2000 Å of Au is continuously formed as a wiring pattern 16.

As is clear from the figure, this Ni-Cr alloy 15 is P
It is formed on the type GaAs layer 12 and the N+GaAs substrate 11 in the area where the protective film 14 has been removed.

Then, on the N-type GaAs layer 13 and the P-type GaAs
A protective film 14 is left on a part of the layer 12, and the N-type G
A Ni--Cr alloy 15 and a wiring pattern 16 are sequentially formed on the aAs layer 13 with a protective film 14 interposed therebetween.

Note that pattern formation of the wiring 16 and the Ni-Cr alloy 15 is performed by photolithography, but it can also be performed by a lift-off method.

FIG. 4 is a diagram showing current versus voltage characteristics of a PN junction light emitting diode in which electrodes are formed by the electrode forming method of the present invention.

In FIG. 4, the horizontal axis represents forward voltage and the vertical axis represents forward current, and the P-N junction area is 1.
It is 6 x 10-3 cm2.

The current vs. voltage characteristics shown in Fig. 4 are equivalent to or better than the conventional case where different electrode metals are used for each P and N layer, and the current vs. voltage characteristics shown in FIG. It was also confirmed that there was no deterioration in the luminescent properties.

On the other hand, regarding the ohmic properties of the electrode made of NiCr alloy 15, the carrier density is 5 x 1016 pieces/cc, and T
e- or Si-doped N-type GaAs layer and Znn-doped GaAs with a carrier density of 1 x 1018 pieces/cc0 or more
layer, and a Si-doped GaAs layer by liquid phase growth.
After the type->P-type inversion growth, all the P-type GaAs layers in the portions thicker than at least 20 μm were confirmed.

Further, it is a well-known fact that the Ni-Cr alloy 15 has a high degree of adhesion to insulating films such as SiO2 and Al2O3.

As is clear from the above explanation, by forming the electrode using Ni-Cr alloy as the first layer metal, P-type GaA
It becomes possible to simultaneously satisfy three conditions: ohmic property for the s-layer 12, ohmic property for the N-type GaAs layer 13, and adhesion for the insulating film 14 such as SiO2.

Therefore, the vapor deposition process and the photolithography process can each be performed once, making it possible to significantly simplify the process.

As detailed above, according to the electrode forming method of the present invention,
A P-type region and an N-type region are exposed on one side of the GaAs substrate,
When forming electrodes and wiring in the P-type and N-type regions, Ni-Cr alloy is formed as the first layer of metal electrodes, so good ohmic properties can be obtained for the P-type and N-type regions. It not only has excellent adhesion to the insulating protective film, but also has the advantage that the vapor deposition process and the photolithography process can be completed only once, thereby simplifying the process.

[Brief explanation of drawings]

1 and 2 are diagrams for explaining a conventional electrode formation method, respectively, and FIG. 3 is a diagram illustrating an embodiment of the electrode formation method of the present invention applied to an electrode formation method for a light emitting diode. FIG. 4 is a diagram showing current versus voltage characteristics of a light emitting diode in which electrodes are formed by the electrode forming method of the present invention. 11...N+GaAs substrate, 12...P-type GaAs layer, 13...N-type GaAs layer, 14.
...Protective film, 15...Ni-Cr alloy,
16...Wiring.

Claims (1)

[Claims] 11 or more P-type head regions and one or more N-type regions
A semiconductor wafer is formed by exposing it on a semiconductor substrate made of As, and electrodes are formed on the P-type head region and the N-type region using a Ni-Cr alloy as the first metal layer. Electrode formation method.