Intrinsic Origin of Negative Fixed Charge in Wet Oxidation for Silicon Carbide

TL;DR

This study uses first-principles calculations to identify the intrinsic origin of negative fixed charges in wet oxidation of silicon carbide, highlighting carbonate-like moieties and CO3 ions in SiO2 as key factors.

Contribution

It reveals the formation mechanisms of negative fixed charges in SiC oxidation, emphasizing the role of carbonate-like structures and residual carbon atoms.

Findings

Carbonate-like moiety in SiO2 causes negative fixed charge.

Residual carbon atoms contribute to CO3 ion formation.

H incorporation influences carbonate formation.

Abstract

We demonstrate on the basis of first-principles calculations that the formation of carbonate-like moiety in SiO$_2$ could be the intrinsic origin of negative fixed charge in SiC thermal oxidation. We find that two possible origins for the negative fixed charges are O-lone-pair state and a negatively charged CO$_3$ ion in SiO$_2$. Such CO$_3$ ion is able to be formed as a result of the existence of residual C atoms in SiO$_2$, which are expected to be emitted from the interface between SiC and SiO$_2$, and the incorporation of H atoms during wet oxidation.