High-quality HfSixOy gate dielectrics fabricated by solid phase interface reaction between physical-vapor-deposited metal–Hf and SiO2 underlayer

Abstract

We fabricated high-quality Hf–silicate (HfSixOy) gate dielectrics by utilizing the solid phase interface reaction between physical-vapor-deposited metal–Hf (typically 0.5nm thick) and SiO2 underlayers. Metal diffusion to the SiO2 layer increases the permittivity of the underlayer, while preservation of the initial SiO2∕Si bottom interface ensures good electrical properties of the gate dielectrics. The Hf–silicate layer remains amorphous and the poly-Si∕HfSixOy gate stack endures activation annealing at 1000°C. The interface trap density was comparable to that of conventional SiO2 dielectrics and the hysteresis of capacitance–voltage curves was as low as 4mV for a bias swing between −2 and +2.5V. Moreover, high electron mobility, equal to 89% of the universal mobility, was obtained for the high-k gate transistor.