The Correlation Between the Preferred Orientation and Al Distribution of Al-Doped HfO2 Films by Plasma-Enhanced Atomic Layer Deposition

Abstract

A high dielectric constant (k = similar to 22.5) Al-doped HfO2 film was prepared on Si substrate by plasma-enhanced atomic layer deposition (PEALD) at a thickness of similar to 30 nm by realizing a (200) preferentially oriented tetragonal structure. The crystalline structure of Al-doped HfO2 films (monoclinic, tetragonal or a mixed monoclinic and tetragonal) was mainly determined by the number of unit cycles in a HfO2 subcycle. However, the preferred orientation and the dielectric constant of tetragonal Al-doped HfO2 films were strongly affected by the film thickness. With decreasing the film thickness from similar to 92 to similar to 9 nm, the dielectric constants of tetragonal Al-doped HfO2 films rapidly decreased from similar to 37 to similar to 8.5 due to the change of the preferred orientation from (200) to (111). By increasing the yield Al dopant distribution in HfO2 film without changing the film composition and the total film thickness, a (200) preferentially oriented tetragonal Al-doped HfO2 films with a high dielectric constant of similar to 22.5 was able to be obtained at a thickness of similar to 30 nm. And, the leakage current densities of the Pt/similar to 30 nm-thick-tetragonal Al-doped HfO2 films/Si capacitor were similar to 10(-5) A/cm(2) for a field strength of -1 MV/cm due to the crystallization after N-2 annealing process.