Insight Into Mobility Improvement by the Oxidation-Minimizing Process in SiC MOSFETs

The mechanism of mobility improvement by the oxidation-minimizing process was investigated by measuring the low-temperature characteristics of MOSFETs with two different gate oxides formed by the conventional oxidation followed by nitric oxide (NO) annealing and the oxidation-minimizing process (H2-CVD-NO) which the authors proposed. Compared to the conventional MOSFETs, the H2-CVD-NO MOSFETs exhibited a low subthreshold swing (SS), small threshold voltage shift, and high mobility, especially at low temperatures. The H2-CVD-NO MOSFET on the (
$11\overline {{2}}0$
) face with heavily-doped p-body showed remarkably high mobility of about 200 cm2/Vs at 100 K and a 40% increase in channel mobility as the measurement temperature was lowered from 300 to 100 K. This increase in channel mobility by lowering the temperature may originate from a low interface state density close to the conduction band edge and weaker phonon scattering at low temperatures. These results indicate that the oxidation-minimizing process can dramatically reduce the interface states in the SiC/SiO2 system, leading to improvement in channel mobility.