Structure, bonding, and passivation of single carbon-related oxide hole traps near 4H-SiC/SiO2 interfaces

• Published in: Journal of applied physics 2014-11, Vol.116 (17)
• Main Authors: Ettisserry, D. P., Goldsman, N., Akturk, A., Lelis, A. J.
• Format: Article
• Language: English
• Subjects: Applied physics; Bonding; Carbon; Defects; Density functional theory; Free energy; Heat of formation; Hole traps; Interface stability; Lattice vacancies; MOSFETs; Nitric oxide; Oxidation; Oxygen; Silicon dioxide; Threshold voltage; Valence band
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4900981

Single carbon interstitial in silicon dioxide, existing in carboxyl configuration, is shown to act as a border hole trap near 4H-SiC/SiO2 interface. Using density functional theory-based formation energy considerations, it is found to switch charge state between +2 and neutral as the 4H-SiC Fermi level sweeps its charge transition level located 1.4 eV above 4H-SiC valence band edge. Thus, carboxyl defect is predicted to be a potential candidate for threshold voltage instability in 4H-SiC MOSFETs. Post oxidation annealing of the interface with nitric oxide is shown to remove carboxyl defects. However, treating the defect in H2 creates a hole trap level at 1.1 eV above 4H-SiC valence band edge similar to the original carboxyl defect. The stability of carboxyl and H2 treated carboxyl defects in their doubly positive state is explained on the basis of their structural and bonding transformations during hole capture. These include puckering and back-bonding of silicon with lattice oxygen as in the well-known oxygen vacancy (E′ center) hole traps and an increase in the bond order between carboxyl carbon and oxygen.