Dependence of optimized annealing temperature for tetragonal phase formation on the Si concentration of atomic-layer-deposited Hf-silicate film

Abstract

This study examined the relation between the permittivity and microstructures of atomic layer deposited Hf1−xSixO2 (HfSiO) thin films with different Si concentrations as a function of post-deposition annealing (PDA) temperature. The PDA at high temperature results in the separation of crystallized HfO2 phase from the much higher Si-containing amorphous-like matrix. Tetragonal phase HfO2 formation with higher permittivity than the monoclinic HfO2 phase is induced with an appropriate Si concentration in the film (∼10–20%). In the crystallized HfSiO film, the Si concentration in the phase-separated HfO2 (mainly consisting of HfO2) could be controlled by PDA temperature, which determines the degree of phase separation. The increased PDA temperature reduces the Si concentration in the phase-separated HfO2, which induced monoclinic phase formation. Therefore, the PDA temperature for maximized permittivity of the crystallized HfSiO films (maximized tetragonal phase portion in the film) depends on the Si concentration of the HfSiO film in the as-deposited state.