EPR study of the role of hydrogen in the defect formation upon heat treatment of oxidized SiC

For the past several years hydrogen incorporation in metal oxide semiconductor (MOS) devices has been of interest because studies have shown that vacuum annealing of oxidized Si substrates desorbs hydrogen, revealing interfacial defects. To day, in applications that require higher power and/or temperature, Si will likely be replaced with a wide-band-gap semiconductor. For MOS devices, SiC is a leading contender because it can be thermally oxidized to form a SiO2 insulating layer similar to Si. However, the SiC/SiO2 structure potentially contains hydrogen sensitive centers similar to those found in Si/SiO2 structures. Using electron paramagnetic resonance (EPR), we have observed a center 1.8 G wide peak-to-peak at g=2.0026. The center is generated in oxidized SiC that has received a 900 degrees C dry, N-2 or O-2, Post Oxidation heat-treatment in which moisture is measured to be less than 1 ppm. Annealing at 900 degrees C in standard Ar containing at least 50 ppm H2O decreases the center's concentration by two orders of magnitude. By comparing results from our study to studies of Si-H and C-H bonds in a-SiC:H [1] and SiC converted graphite [2], we suggest that this center is related to carbon dangling bonds created by the effusion of hydrogen during the dry heat treatment. We will compare the activation energy for the hydrogen depassivation of our center with that found for other C-H and Si-H systems.