Impact Of Byproducts Formed On A 4h-Sic Surface On Interface State Density Of Al2o3/4h-Sic(0001) Gate Stacks

The impact of byproducts formed on a 4H-SiC(0001) surface by substrate oxidation on the interface state density (D-it) of Al2O3/4H-SiC gate stacks was investigated in this study, because some C-related byproducts are predicted to have defect states near the conduction band minimum (E-C) of 4H-SiC. At first, by developing an in situ cyclic metal layer oxidation method, we realized the formation of an Al2O3/4H-SiC gate stack without substrate oxidation, which was verified using conventional X-ray photoelectron spectroscopy (XPS). Then, the amount of byproducts on the 4H-SiC surface was controlled by chemical etching of thermally oxidized 4H-SiC. The results showed that the D-it near the E-C of 4H-SiC for the Al2O3/4H-SiC gate stack increased with the amount of byproducts until it fully covered the 4H-SiC surface; thereafter, it did not increase. For the sample with byproducts below the detection limit of XPS, a D-it value as low as 5x10(11)cm(-2) eV(-1) at around E-C - 0.15eV of 4H-SiC was obtained.