Influence on curvature induced stress to the flatband voltage and interface density of 4H-SiC MOS structure

Gate oxide film on Silicon carbide (SiC) severely affects the performance of SiC metal-oxidesemiconductor field effect transistor (MOSFET). The authors investigated the influence of curvature induced stress/strain to flatband voltage (Vfb) and interface density (Dit) on SiO2/SiC by Capacitance-voltage (C-V) measurement. The curvature of epitaxy wafers has been identified by the Thin Film Stress Measurement system. The compress/tensile curvature led to increase of the positive Vfb shift (negative fixed charge) of SiO2 and the interface density of SiO2/SiC during dry thermal oxidation process. In addition, the transverse optical (TO) phonon wavenumber of the samples related with the curvature of the film, indicating that stress mainly affected the interface of SiO2/SiC. According to the experimental result, the authors suggested that a “free” stress oxide film might be a best choice for the application of SiC-MOSFET.