Characterization of the effects of nitrogen and hydrogen passivation on SiO2/4H-SiC interface by low temperature conductance measurements

We investigate the effects of NO annealing and forming gas（FG） annealing on the electrical properties of a SiO2/SiC interface by low-temperature conductance measurements.With nitrogen passivation,the density of interface states(DIT) is significantly reduced in the entire energy range,and the shift of flatband voltage,△VFB,is effectively suppressed to less than 0.4 V.However,very fast states are observed after NO annealing and the response frequencies are higherthan 1 MHz at room temperature.After additional FG annealing,the DIT and △VFB are further reduced.The values of the DIT decrease to less than 1011 cm-2 eV-1 for the energy range of EC-ET≥0.4 eV.It is suggested that the fast states in shallow energy levels originated from the N atoms accumulating at the interface by NO annealing.Though FG annealing has a limited effect on these shallow traps,hydrogen can terminate the residual Si and C dangling bonds corresponding to traps at deep energy levels and improve the interface quality further.It is indicated that NO annealing in conjunction with FG annealing will be a better post-oxidation process method for high performance SiC MOSFETs.