Electrical properties of hafnium silicate gate dielectrics deposited directly on silicon

Abstract

Hafnium silicate (HfSixOy) gate dielectric films with ∼6 at. % Hf exhibit significantly improved leakage properties over SiO2 in the ultrathin regime while remaining thermally stable in direct contact with Si. Capacitance–voltage measurements show an equivalent oxide thickness (tox) of less than 18 Å for a 50 Å HfSixOy 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 1.2×10−6 A/cm2 at 1 V bias. Hysteresis in these films is measured to be less than 20 mV, the breakdown field is measured to be EBD∼10 MV/cm, and the midgap interface state density is Dit∼1011 cm−2 eV−1. Cross-sectional transmission electron microscopy shows no signs of reaction or crystallization in HfSixOy films on Si after being annealed at 800 °C for 30 min.