Study of interface state density and effective oxide charge in post-metallization annealed SiO2-SiC structures

A systematic study of post-metallization annealing (PMA) effect on the quality of thermal SiO₂ 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_eff) and interface state density (D _it). To ensure accurate results, D_it was measured at 350°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_eff and D_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_eff values close to the detection limit due to the uncertainty in SiC electron affinities and D_it values below 1×10¹¹ cm^-2/eV deep in the band gap can be reproducibly obtained for both p-type 6H- and 4H-SiC