Comparative study on slow-state near interface hole traps in NO and Ar annealed N-type 4H-SiC MOS capacitors by ultraviolet light

The characteristics of near interface charge trapping and releasing on n-type 4H-SiC MOS capacitors with NO and Ar passivation have been systematically investigated through time-dependent bias stress with ultraviolet light irradiation. Flat band voltage instability of the Ar annealed samples mainly results from electrons directly tunneling in and out of the near interface electron traps. However, hole trapping by the near interface hole traps (NIHTs) also need to be concerned for the NO annealed samples. It is found that part of the trapped holes cannot be easily released from the slow-state NIHTs, which may act as the positive fixed charge and induce the unrecoverable negative shift of threshold voltage. The results from XPS show that after the NO annealing, some of the intermediate oxidation states are converted to the strong Si≡N and Si–Ox–Ny bonds located in the transition layer, which may act as NIHTs and even suppress hydrofluoric acid etching. Thus, it is important to optimize nitrogen treatment in order to reduce the density of NIHTs induced in the 4H-SiC MOS devices.No Full Tex