JPH0799169A - Manufacture of silicon carbide electronic device - Google Patents

Abstract

PURPOSE:To conduct a heat treatment at a low temperature and to prevent graphite from being precipitated on the surface of an ohmic electrode by a method wherein a nickel-silicon alloy layer whose nickel composition is at specific atomic % is formed on an n-type silicon carbide substrate, the heat treatment is conducted and the ohmic electrode is formed on the silicon carbide substrate. CONSTITUTION:Ni and Si are sputtered and vapor-deposited simultaneously, by an RF magnetron sputtering method, on the surface of an n-type SiC substrate 1, and an Ni-Si alloy layer 2 is formed in such a way that Ni and Si are set at an atomic ratio of 38:62. As a heat treatment after that, this assembly is annealed in a vacuum of 2X10 Torrs, at 600 deg.C and for 30min, and a current- voltage characteristic without a rectification property is displayed. In addition, when the composition ratio of Ni to Si is changed, a good ohmic property is displayed when the composition of Ni is at an atomic ratio of 33% or higher and 67% or lower. Thereby, an electrode which can be connected easily is obtained without a need for a heat treatment at a high temperature, by a heat treatment at a temperature of 700 deg.C or lower and without precipitating graphite on the face of the electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a SiC electronic device using silicon carbide (hereinafter referred to as SiC) as a new semiconductor material.

[0002]

2. Description of the Related Art Currently, a power device using Si has been developed for the purpose of controlling high frequency and high power, and has been improved in performance by various structural measures. But this too is approaching the theoretical limit. In addition, power devices are often required to operate in adverse environments such as high temperatures and radiation, but such devices cannot be realized in Si. In this way, it is necessary to apply new materials in order to achieve higher performance. In response to the above requirements, since SiC is a 6H type and has a wide band gap of 2.93 ev, it has excellent electrical conduction control at high temperatures and radiation resistance,
The breakdown electric field, which is about one digit higher than Si, can be applied to high breakdown voltage devices, and the saturation drift velocity of electrons, which is about twice that of Si, enables high frequency and high power control, so SiC is suitable for high frequency and high power control. It is a promising semiconductor material.

[0003]

Ni is used as an ohmic electrode material on n-type SiC when applying the excellent material properties of SiC as described above to a power device. However, only by depositing Ni on n-type SiC by a vacuum vapor deposition method or the like, a Schottky barrier is formed at the interface between the metal and the semiconductor, and rectifying property is exhibited, and ohmic property is not exhibited. An ohmic electrode can be obtained for the first time by applying a heat treatment to promote the diffusion of Ni into SiC and the diffusion of Si in SiC into Ni. However, this has a drawback that the heat treatment must be performed at a high temperature of 1000 ° C. or higher. Further, during the heat treatment, Ni and Si in SiC diffuse into each other to form nickel silicide, but C in SiC diffuses on the surface of the Ni electrode and precipitates as graphite. This graphite has a drawback that it hinders the connection of the conductor to the electrode.

The object of the present invention is to eliminate the above-mentioned drawbacks, the heat treatment for forming an ohmic electrode with Ni on n-type SiC can be carried out at low temperature, and the precipitation of graphite on the electrode surface can be prevented. It is to provide a manufacturing method of a non-SiC electronic device.

[0005]

In order to achieve the above object, a method for manufacturing a SiC electronic device according to the present invention is an n-type Si device.
After forming a Ni-Si alloy layer having a Ni composition of 33 to 67 atomic% on a C substrate, heat treatment is performed to form an ohmic electrode on the SiC substrate. It is a good method to form such a Ni-Si alloy layer by vapor deposition simultaneously with Ni and Si.
Another method of manufacturing a SiC electronic device of the present invention is an n-type SiC
A Si layer and a Ni layer are laminated in this order on the substrate, and Ni is
After being made to exist at 33 to 67 atomic%, heat treatment is performed to form an ohmic electrode on the SiC substrate. It is a good method to form each of the Si layer and the Ni layer of such a laminated body by vapor deposition. In either method, the purpose is that the heat treatment temperature is 700 ° C or lower.

[0006]

[Function] Ni-Si alloy layer or Si, Ni on SiC substrate
If a laminated body is formed, NiSi ₂ (Ni 33 at%, Si 67 at%) can be formed without supplying Si from the SiC substrate.
An electrode is obtained which makes ohmic contact with the substrate. In any case, if the atomic ratio of Ni is 33% or less, Si is excessive and inhibits conductivity, and if it is 67% or more, excessive Ni is present at the interface between NiSi ₂ and SiC, resulting in a discontinuous interface. Will end up. Ni
The formation of NiSi ₂ from Si does not require a high temperature of 1000 ° C. or higher, and a low temperature of 700 ° C. or lower is sufficient. Also, Si
Is not supplied from SiC, the surplus C is Ni
There is no phenomenon of diffusion into the electrode and precipitation of graphite on the surface of the electrode.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In the electronic device of one embodiment whose electrode portion is shown in FIG. 1, Ni and Si are simultaneously sputter-deposited on the surface of the n-type SiC substrate 1 by the RF magnetron sputtering method.
And Si formed the Ni-Si alloy layer 2 so that the atomic ratio was 38:62. As a heat treatment after this, in a vacuum of 2 × 10 ^-6 Torr
When annealed at 600 ° C. for 30 minutes, a current-voltage characteristic having no rectifying property was exhibited as shown by the line 11 in FIG. For comparison, Ni electrode was formed by sputter deposition by the conventional method, and 1200 ℃
When the current-voltage characteristic was measured by annealing for 10 minutes at 10 ° C., it did not show rectifying property as shown by the line 13 in FIG.
It was found that the line 11 of the embodiment of the present invention had a lower resistance and a current flowed more easily. Furthermore, changing the composition ratio of Ni and Si,
Experiments showed that the composition of Ni was 33% or more in atomic ratio and 67
When it was less than%, good ohmic property was exhibited.

In an electronic device of another embodiment having an electrode portion shown in FIG. 2, the Si layer 3 is sputter-deposited on the surface of the n-type SiC substrate 1 by the RF magnetron sputtering method, and then the Ni layer 4 is sputtered. It was vapor-deposited. At this time, the Si layer 3 and the Ni layer 4 were formed so that the composition ratio of Ni and Si was 40:70 in atomic ratio. For subsequent heat treatment, in a vacuum of 2 × 10 ^-6 Torr
When annealed at 600 ° C. for 30 minutes, as shown by the line 12 in FIG. 3, a current-voltage characteristic having no rectifying property was shown, and a resistance lower than that of the conventional electrode and a good ohmic electrode could be obtained. . When the ratio of the thickness of the Ni layer 4 to the thickness of the Si layer 3 was lower than 2.2: 8, the good ohmic property was not exhibited. If the Ni layer becomes thinner than this ratio, Ni will become Si by heat treatment.
Ni diffuses while forming NiSi ₂ ,
This is probably because the surface cannot be reached.

Further, when the surfaces of these examples were examined, there was no precipitation of graphite, and it was easier to carry out the bonding process of the conductor wire as compared with the conventional method.

[0010]

According to the present invention, by forming an ohmic electrode on an n-type SiC substrate from a Ni-Si alloy or a Ni-Si laminated body, the temperature is 1000 ° C or higher as in the case of a pure Ni electrode. No need for high temperature heat treatment, and only low temperature heat treatment of 700 ℃ or less is required. Further, since graphite is not deposited on the electrode surface and an electrode which can be easily connected is obtained, the effect on the manufacture of the SiC electronic device is extremely large.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an electrode portion of a SiC electronic device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an electrode portion of a SiC electronic device according to another embodiment of the present invention.

FIG. 3 is a current-voltage characteristic diagram of an n-type SiC substrate electrode according to an embodiment of the present invention and a conventional example.

[Explanation of symbols]

 1 n-type SiC substrate 2 Ni-Si alloy layer 3 Si layer 4 Ni layer

Claims (5)

[Claims] 1. A nickel composition of 33 on an n-type silicon carbide substrate.
A method for manufacturing a silicon carbide electronic device, comprising forming a nickel-silicon alloy layer of about 67 atomic% and then performing heat treatment to form an ohmic electrode on a silicon carbide substrate. 2. The method for manufacturing a silicon carbide electronic device according to claim 1, wherein the nickel-silicon alloy layer is formed by simultaneously vapor-depositing nickel and silicon. 3. A silicon layer and a nickel layer are laminated in this order on an n-type silicon carbide substrate so that Ni is present in the laminate at 33 to 67 atomic%, and then heat treated to give silicon carbide. A method of manufacturing a silicon carbide electronic device, comprising forming an ohmic electrode on a substrate. 4. The method for manufacturing a silicon carbide electronic device according to claim 3, wherein the silicon layer and the nickel layer of the laminate are each formed by vapor deposition. 5. The heat treatment temperature is 700 ° C. or lower.
5. A method for manufacturing a silicon carbide electronic device according to any one of 1 to 4.