Stabilization of a very high-k crystalline ZrO_2 phase by post deposition annealing of atomic layer deposited ZrO_2/La_2O_3 dielectrics on germanium

摘要

The impact of the ZrO_2/La_2O_3 film thickness ratio and the post deposition annealing in the temperature range between 400℃ and 600 ℃ on the electrical properties of ultrathin ZrO_2/L_2O_3 high-k dielectrics grown by atomic layer deposition on (1 0 0) germanium is investigated. As-deposited stacks have a relative dielectric constant of 24 which is increased to a value of 35 after annealing at 500 ℃ due to the stabilization of tetragonal/cubic ZrO_2 phases. This effect depends on the absolute thickness of ZrO_2 within the dielectric stack and is limited due to possible interfacial reactions at the oxide/Ge interface. We show that adequate processing leads to very high-k dielectrics with EOT values below 1 nm, leakage current densities in the range of 0.01 A/cm~2, and interface trap densities in the range of 2-5 × 10~(12) eV~(-1) cm~(-2).