High-quality HfSi_xO_y gate dielectrics fabricated by solid phase interface reaction between physical-vapor-deposited metal-Hf and SiO_2 underlayer

摘要

We fabricated high-quality Hf-silicate (HfSi_xO_y) gate dielectrics by utilizing the solid phase interface reaction between physical-vapor-deposited metal-Hf (typically 0.5 nm thick) and SiO_2 underlayers. Metal diffusion to the SiO_2 layer increases the permittivity of the underlayer, while preservation of the initial SiO_2/Si bottom interface ensures good electrical properties of the gate dielectrics. The Hf-silicate layer remains amorphous and the poly-Si/HfSi_xO_y gate stack endures activation annealing at 1000℃. The interface trap density was comparable to that of conventional SiO_2 dielectrics and the hysteresis of capacitance-voltage curves was as low as 4 mV for a bias swing between -2 and +2.5 V. Moreover, high electron mobility, equal to 89% of the universal mobility, was obtained for the high-k gate transistor.