Effects of n-type 4H-SiC epitaxial wafer quality on reliability of thermal oxides

The reliability of thermal oxides was investigated on n-type 4H-SiC(0001) epitaxial wafers with different metal impurity concentrations and surface roughness. Time-zero dielectric breakdown measurements showed that almost all of the thermal oxides ruptured at a field-to-breakdown (E-BD) of 10 MV/cm, and that the maximum E-BD was 11 MV/cm, despite the influence of the epitaxial wafer. On the other hand, time-dependent dielectric breakdown measurements indicated that the charge-to-breakdown (Q(BD)) of the thermal oxides was influenced by the epitaxial wafer. This suggests that two types of oxide breakdown regimes exist under a high-stress field: one resulting from wafer influences, and the other intrinsic. (C) 2004 American Institute of Physics.