Atomistic insights into carbon cluster decomposition in amorphous SiOC under O-, N-, and NO-containing conditions: A molecular dynamics study

Abstract

Carbon-related defects formed during thermal oxidation degrade SiC MOS device performance and reliability. NO annealing mitigates these defects, but the separate roles of oxygen and nitrogen in carbon-cluster decomposition and carbon removal at the SiC/SiO2 interface remain unclear. In this work, we perform melt-quench molecular dynamics simulations of amorphous SiOC derived from a Si30O60C12 reference model, adding up to 12 O or N atoms or 6 NO pairs, to track C—C network fragmentation and gas-like CO/CO2 unit formation. Carbon clusters decreased under all added conditions, but redistribution was species-dependent. O addition increased the fraction of carbon atoms in the gas category, i.e., CO/CO2-like units detached from the Si-containing network, to about 40%, while the solid phase retained a well-connected C—C network. In contrast, N addition caused pronounced solid-phase fragmentation of the C—C bond network, with only about 10% of carbon classified into this gas category. Under the N-added condition, among solid-phase carbon atoms, about 55% had no C—C bonds and about 40% were twofold coordinated. NO addition showed an intermediate gas-category carbon fraction of about 30%, whereas fragmented states with nitrogen-bonded low-coordination carbon remained common. The C—N distance distribution showed a short-bond component at 1.2–1.3 Å, suggesting multiple-bond character. This strong C—N bonding is associated with the stabilization of low-coordination carbon and the reduction of C—C bonding in the solid phase. Overall, these findings suggest that nitrogen and oxygen play complementary roles under NO annealing, with nitrogen fragmenting solid-phase carbon and oxygen promoting the formation of gas-like CO/CO2 precursor units relevant to carbon removal at the SiC/SiO2 interface.