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 = 22.5) Al-doped HfO2 film was prepared on Si substrate by plasma-enhanced atomic layer deposition (PEALD) at a reduced thickness of ~ 30 nm by realizing a (200) preferentially oriented tetragonal structure. The realization of a (200) preferred orientation was able to be obtained by the interface control in PEALD. When using a conventional supercycle that consisted of the Al2O3 and HfO2 subcycles, the dielectric constants of tetragonal Al-doped HfO2 films rapidly decreased from 37 to 8.5 as the film thickness decreased from ~ 92 to ~ 9 nm due to the change of the preferred orientation from (200) to (111). To obtain (200) preferentially oriented tetragonal Al-doped HfO2 thin films at highly thin thickness, a modified supercycle that consisted of the Hf-Al-O subcycle and the HfO2 subcycle was designed to increase Al dopant distribution in HfO2 films. As a result, a (200) preferentially oriented tetragonal Al-doped HfO2 films with a high dielectric constant of 22.5 was obtained at a reduced thickness of ~ 30 nm. Also, the leakage current densities of the Pt/~ 30 nm-thick-tetragonal Al-doped HfO2 films/Si capacitor were about 10-5 A/cm2 for a field strength of -1 MV/cm due to the crystallization after N2 annealing process.