Electrical properties of hafnium silicate gate dielectrics deposited directly on silicon

Hafnium silicate (${\mathrm{HfSi}}_x{\mathrm{O}}_y)$ gate dielectric films with ∼6 at. % Hf exhibit significantly improved leakage properties over ${\mathrm{SiO}}_{\mathrm{2}}$ in the ultrathin regime while remaining thermally stable in direct contact with Si. Capacitance–voltage measurements show an equivalent oxide thickness ${\mathrm{(t}}_{\mathrm{ox}})$ of less than 18 Å for a 50 Å ${\mathrm{HfSi}}_x{\mathrm{O}}_y$ film deposited directly on a Si substrate, with no significant dispersion of the capacitance for frequencies ranging from 10 kHz to 1 MHz. Current–voltage measurements show for the same film a leakage current of ${\text{1.2×10}}^{\text{−6}} {\mathrm{A/cm}}^{\mathrm{2}}$ at 1 V bias. Hysteresis in these films is measured to be less than 20 mV, the breakdown field is measured to be $E_{\mathrm{BD}}\text{∼10\hspace{0.05em}}\mathrm{MV/cm},$ and the midgap interface state density is $D_{\mathrm{it}}{\text{∼10}}^{11} {\mathrm{cm}}^{\mathrm{-2}}{\mathrm{ eV}}^{\mathrm{-1}}.$ Cross-sectional transmission electron microscopy shows no signs of reaction or crystallization in ${\mathrm{HfSi}}_x{\mathrm{O}}_y$ films on Si after being annealed at 800 °C for 30 min.