Reduction of interface-state density in 4H–SiC n-type metal–oxide–semiconductor structures using high-temperature hydrogen annealing

The effects of hydrogen annealing on capacitance–voltage $\mathrm{(C–V)}$ characteristics and interface-state density ${\mathrm{(D}}_{\mathrm{it}})$ of 4H–SiC metal–oxide–semiconductor (MOS) structures have been investigated. The $D_{\mathrm{it}}$ was reduced to as low as ${\text{1×10}}^{11} {\mathrm{eV}}^{\mathrm{-1}}{\mathrm{ cm}}^{\mathrm{-2}}$ at $E_c\text{−E=0.6\hspace{0.05em}}\mathrm{eV}$ using hydrogen annealing above $\text{800\hspace{0.05em}°}\mathrm{C},$ where $E_c\mathrm{-E}$ is the energy level from the conduction-band edge. Secondary ion mass spectroscopy and $D_{\mathrm{it}}$ analysis revealed that $D_{\mathrm{it}}$ decreased with the increase of hydrogen concentration accumulated at the ${\mathrm{SiO}}_{\mathrm{2}}\mathrm{/4H–SiC}$ interface. The interface states at ${\mathrm{SiO}}_{\mathrm{2}}\mathrm{/4H–SiC}$ are thought to be originated from the dangling bonds of C atoms as well as Si atoms, because $D_{\mathrm{it}}$ decreases as the hydrogen annealing temperature increases and saturates around $\text{800\hspace{0.05em}°}\mathrm{C}.$ This high-temperature hydrogen annealing is useful for accumulation-type SiC metal–oxide–semiconductor field-effect transistors, which have n-type MOS structures to reduce the $D_{\mathrm{it}}.$