Influence of curvature induced stress on first principle calculation and the reliability of 4H-SiC (0001) thermally grown SiO_2 gate oxide

摘要

Gate oxide films on silicon carbide (SiC) markedly affect the performance of SiC metal-oxide-semiconductor field effect transistors (MOSFETs). We used current-voltage (I-V) measurements to investigate the influence of curvature induced stress/strain on the breakdown electric field and the charge-to-breakdown (Q(BD)) at SiO2/SiC, defined here as time-zero dielectric breakdown and time-dependent dielectric breakdown, respectively. The curvature of the epitaxy wafers was characterized by a thin film stress measurement system. The compression/tensile curvature decreased E-BD and Q(BD) during the dry thermal oxidation process. Furthermore, first-principle calculations suggested that the energy levels of the samples were related to the lattice constants of the SiC crystal, indicating that stress mainly affected the SiO2/SiC interface. We suggest that a "stress free" oxide film might be the best choice for SiC-MOSFET applications.