High voltage silicon carbide semiconductor device with bended ed

Details High voltage silicon carbide semiconductor device with bended ed High voltage silicon carbide semiconductor device with bended ed

1997-03-05

1999-06-22

Chaudhuri, Olik

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

Specified wide band gap semiconductor material other than...

Diamond or silicon carbide

257510, 257622, 438 43, 438 39, 438931, H01L 310312, H01L 2900, H01L 2906

Patent

active

059144998

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a semiconductor device with silicon carbide as base material. Proton or ion implantation is used for restructuring a region of the silicon carbide from being conductive to being resistive, wherein the method is used both for defining the area of a p-n junction during manufacture of a component and for edge terminating the p-n junction and for passivating the surface of the component. Further, the method is used for creating a positive edge angle at the edge of the p-n junction. The invention also relates to the implantation method itself.


BACKGROUND ART

Semiconductor devices based on silicon carbide (SiC) as base material are continuously developed to be used in high-temperature contexts, high-power applications and under conditions involving a high radiation, under which circumstances conventional semiconductors cannot function satisfactorily. Estimations indicate that SiC transistors of power MOSFET type and diode rectifiers of SiC could operate over larger voltage and temperature intervals, for example up to 650.degree.-800.degree. C., and exhibit better breaker properties with lower losses and higher frequencies, and still be 20 times smaller in volume than corresponding silicon components. These improvements are due to the inherent advantageous material properties which silicon carbide possesses in relation to silicon, as for example a higher breakdown field (up to 10 times higher than silicon), a higher thermal conductivity (more than 3 times higher than silicon), and a higher energy band gap (2.9 eV for 6H--SiC, one of the crystal structures for SiC).
Since the silicon-carbide semiconductor technique is relatively young and in many respects non-optimized, there are many critical manufacturing problems which require a solution before fully useful SiC power semiconductors may be realized experimentally and manufacture in larger quantities may be carried out. This is especially true of components intended for high-power and high-voltage applications. Difficulties requiring a solution are that the background doping concentration for the voltage-absorbing layer in the component must be reduced for one single component to be able to withstand voltages of several kilovolts, that the surface passivation technique of the silicon carbide must be optimized, and that the quantity of critical defects in the silicon carbide material must be reduced if, for example, heavy-current components with large areas are to be manufactured. Other areas which require development are, for example, methods for manufacturing good ohmic contacts for the material, methods for doping with, for example, implantation, and process techniques for, for example, etching, etc.
Manufacturing high-volt diodes in 6H--SiC with epitaxially created p-n junctions and Schottky junctions has been carried out for experimental purposes (see, e.g., M. Bhatnagar and B. J. Baliga, IEEE Trans. Electron Devices, Vol. 40, No. 3, pp 645-655, March 1993, or P. G. Neudeck, D. J. Larkin, J. A. Powell, L. G. Matus and C. S. Salupu, Appl. Phys. Lett., Vol. 64, No. 11, 14 Mar. 1994, pp 1386-1388). Some of the problems described above have been solved, such as among other things the reduction of the doping concentration, whereby the first 2000 V silicon carbide diodes ever have been reported. This has been realizable because of the progress of development in recent years for manufacturing substrate materials in silicon carbide.
However, no simple method for surface-passivating silicon carbide useful for restructuring the surface of a silicon carbide material for obtaining a high-resistance layer from the surface down to a desired depth is known.
Another difficulty to master during manufacture of high-volt diodes or other semiconductor devices with a voltage-absorbing p-n junction is to achieve a suitable termination of the edge of the p-n junction. The electric field across the p-n junction at the edge of thereof is very large when a high reverse voltage is applied across the p-n junction. This problem has not

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