Effect of nitrogen passivation on interface composition and physical stress in SiO2/SiC(4H) structures

Abstract

The electron density and physical stress at the thermally oxidized SiC/SiO2 interface, and their change with nitrogen incorporation, were observed using x-ray reflectivity, Raman scattering, and in-situ stress measurement. There is no evidence for residual carbon species at the SiO2/SiC. Instead, a ∼1 nm thick low electron density layer is formed at this interface, consistent with interfacial suboxides (SiOx, 0.3 < x < 2), along with high interfacial stress. Nitrogen passivation, a known process to improve the interface state density and electronic properties, eliminates the low density component and simultaneously releases the interface stress. On the basis of these findings, a chemical interaction model is proposed to explain the effect of the nitrogen in terms of both stress reduction and elemental control of the dielectric/SiC interface, resulting in a higher quality gate stack on SiC.