Study of interface state density and effective oxide charge in post-metallization annealed SiO/sub 2/-SiC structures

A systematic study of post-metallization annealing (PMA) effect on the quality of thermal SiO/sub 2/ on p-type 6H- and 4H-SiC has been carried out. A simultaneous quasi-static hi-lo frequency capacitance-voltage method has been employed to measure the total effective oxide charge (N/sub eff/) and interface state density (D/sub it/). To ensure accurate results, D/sub it/ was measured at 350/spl deg/C which, depending on the hole capture cross sections, should enable the measurement of interface states located in the band gap as deep as 1.3-1.5 eV from the valence band edge. The dependence of N/sub eff/ and D/sub it/ on annealing temperature and ambient as well as the effect of thermal and sputtered gate metal on the oxide quality are reported. It is shown that N/sub eff/ values close to the detection limit due to the uncertainty in SiC electron affinities and D/sub it/ values below 1/spl times/10/sup 11/ cm/sup -2//eV deep in the band gap can be reproducibly obtained for both p-type 6H- and 4H-SiC.