Plasma enhanced atomic layer deposition of HfO2 and ZrO2 high-k thin films

A plasma enhanced atomic layer deposition (PEALD) process was developed to deposit high-k dielectric constant materials using alternative metal t-butoxide and oxygen plasma exposures. The deposited thickness increased linearly with an increasing number of precursor/oxygen plasma cycles, and the growth rates of HfO2 and ZrO2 were determined to be 1.1 and 2.8 angstrom/cycle, respectively. The as-deposited films were determined to be fully oxidized and amorphous by the x-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared spectroscopy (FTIR). The PEALD films were found to have high concentrations of bridging oxygen bonds with metals (M-O-M) as the film thickness increased, in contrast to the high concentrations of M-O-H in the films deposited by plasma enhanced chemical vapor deposition (PECVD). The M-O-M bonds in the PEALD films were further increased upon annealing at 250 degrees C in atmosphere with a corresponding decrease in M-O-H concentrations, suggesting the elimination of hydroxyl groups upon annealing. The PEALD HfO2 and ZrO2 films showed higher dielectric constants (25, 22) than those of PECVD deposited films (21, 19), likely due to the enhanced ionic contribution from the M-O-M bonds in the PEALD films. The smallest equivalent oxide thickness (EOT) of 13 angstrom was achieved by PEALD HfO2 with a leakage current density of 0.2 A/cm(2), several orders of magnitude below that of thermally grown SiO2 films with the same EOT. (c) 2005 American Vacuum Society.