Reaction of NO molecule at 4H-SiC/SiO2 interface and its orientation dependence: a first-principles study

The reactions of NO molecules at the 4H-SiC/SiO2 interface on various plane orientations are theoretically investigated using density functional calculations to clarify the microscopic mechanisms of the NO post-oxidation annealing (POA) process. We find that the energy barriers for nitrogen incorporation reaction are smaller than those for nitrogen desorption irrespective of the plane orientation, indicating that N atoms are preferentially incorporated. However, on the Si-face we a find possible NO reaction process without CO molecule formation and the reaction with NCO molecule formation when the interface includes pre-incorporated N atoms. Owing to the reaction resulting in the formation of an NCO molecule, the incorporation of N atoms can be suppressed, which could be one of the possible origins for the N density saturation in the NO-POA. The calculated results suggest that not only the structural stability of the interface but also reaction kinetics are crucial for the incorporation of N atoms during the NO-POA.