H2 surface treatment for gate-oxidation of SiC metal-oxide-semiconductor field effect transisitsors

This paper reports a comparative investigation of electrical characteristics of 4H- and 6H-SiC metal-oxide-semiconductor field effect transisitsors (MOSFETs). From the study of C–V measurement, no significant difference is found between p-type 6H-SiC and 4H-SiC in the dependence of the oxidation process, such as wet or dry ambient. Nevertheless, the MOSFETs characteristics are quite different, and a very small field effect mobility μeff (<10 cm2 (V s)−1) is obtained for 4H-SiC. This poor μeff is improved by H2 surface annealing, which has been reported to give atomically flat surface, and mono-hydride termination. In addition, a strong correlation is found between μeff and the shift of the threshold voltage from the ideal value. These results confirm that the surface preparation technique is a key factor to control the interface. And H2 treatment reduces the negative charges at the interface and results in a μeff of 20 cm2 (V s)−1 in 4H-SiC MOSFETs.