Effects of nitridation and annealing on interface properties of thermally oxidized SiO2/SiC metal–oxide–semiconductor system

The effects of N2O nitridation and subsequent annealing in different conditions on thermally oxidized n-type 6H–silicon carbide (SiC) metal–oxide–semiconductor (MOS) interface properties were investigated. Influence of high-field stress on the MOS system was also studied. The nitrided device annealed in dry or wet O2 is found to have lower interface-state density compared to the device annealed in N2 because the reoxidation can reduce nitridation-induced interface damage. Furthermore, significantly less shift of flatband voltage during high-field stress for all nitrided devices indicates much better oxide reliability by replacing strained Si–O bonds with stronger Si–N bonds during nitridation. This is further supported by the fact that annealing of the nitrided device in dry or wet oxygen slightly reduces the robustness of the oxide. In summary, the O2-annealing conditions have to be optimized to deliver a proper tradoff between interface quality and reliability.