Wide bandgap semi-conductors : the silicon carbide domain (SiC)

In just a few years, silicon carbide (SiC) has become a major player in the electronics industry, driven by the ever-increasing need to save electrical energy. This wide-bandgap semiconductor boasts a high breakdown field, high electron saturation rate and high thermal conductivity. It is this unique combination of exceptional physical properties that gives it its excellent voltage withstand capability, combined with its ability to withstand very high current densities. Add to this the ability to work at high frequencies and temperatures, and it's easy to see why SiC is a material perfectly suited to the manufacture of power components, with electrical power distribution as its preferred field of application.

Today, the economic stakes are clearly identified, and it is estimated that, over the next few years, silicon carbide will progressively replace silicon for all power components required to operate above 1000 V. Its main handicap is that, generally speaking, substrates are expensive and the progress required to develop them is slow. Nevertheless, 3 and 4 in (7.5 and 10 cm) diameter wafers are available from several manufacturers, and prototype wafers with a diameter of 6 in (15 cm) have been presented. Thin-film deposition technologies (epitaxy) and selective doping technologies (in situ doping or ion implantation doping) have been relatively well controlled on these substrates for several years now. This means we can reproducibly control the concentration of carriers in several successive single-crystal layers, enabling us to pursue the development of a self-sufficient component production chain. What remains to be done is to optimize contact technology for high-temperature applications and passivation (particularly for very high-voltage rectification applications, where it is necessary to avoid arcing outside the junction). Finally, encapsulation remains a relatively unexplored field. To the best of our knowledge, there are as yet no enclosures specifically designed for extreme operating conditions.

The SiC process therefore appears to be the natural development of the older "silicon" and "gallium arsenide" processes. What's more, it's one of (if not the) ideal solution for producing sensors or optoelectronic devices (photoelectric switches, for example) that need to operate at very high temperatures. A number of articles on this subject published in Techniques de l'Ingénieur ( [RE3] , [D3119]...