A large reduction in interface-state density for MOS capacitor on 4H-SiC (11(2)over-bar0) face using H2 and H2O vapor atmosphere post-oxidation annealing

We have observed the SiC surface of 4H-SiC(0001) and (11 (2) over bar0) faces by atomic force microscopy (AFM) and investigated the oxidation and post-oxidation annealing (POA) effects on the capacitance-voltage (C-V) characteristics and the interface-state density (D-it) of n-type SiC MOS capacitors formed on the (11 (2) over bar0) face. As a result, AFM observation revealed the surface of the (11 (2) over bar0) face is smoother than that of the (000 1) face. This means that the (11 (2) over bar0) face is more suitable for SiC MOSFETs than the (000 1) face. In the case of the dry oxidation, the D-it of the (11 (2) over bar0) face is larger than that of the (0001) face. On the other hand, wet oxidation decreases the D-it at shallow level from the conduction band edge (E-c) on the (11 (2) over bar0) face, and results in smaller D-it than the (0001) face. H-2 and H2O vapor atmosphere POA reduce the D-it from E-c-E=0.2eV to 0.6eV Especially, H-2 POA is very effective for the D-it reduction. Our group has succeeded in the inversion-channel mobility as high as 110cm(2)/Vs using H-2 POA [1].