Alternative routes to minimize electrical degradation in 4H-SiC MOS capacitors

To minimize electrical degradation from thermal oxidation of 4H-SiC, a thin and stoichiometric SiO₂ film was thermally grown, monitored by X-ray photoelectron spectroscopy. To obtain thicker films, SiO₂ was deposited by sputtering. Reduction in the leakage current and in the flatband voltage were observed when compared to SiO₂ films thermally grown or deposited directly on 4H-SiC, indicating, respectively, improvement in the dielectric properties and reduction of the effective negative fixed charge in the structure. Post-deposition annealing in Ar also reduced the flatband voltage of the samples but induced an electrical degradation in the SiO₂/4H-SiC interface. Nuclear reaction analyses proved that the thin film thermally grown was not stable during this annealing, exchanging O atoms with the deposited film and with the gaseous ambient.