X-ray photoelectron spectroscopic analysis of HfSiON thin films

HfSiON thin films with different thicknesses were prepared by the oxidation of sputter-deposited hafnium nitride (HfN) thin films. Thereafter, the chemical structures were investigated using XPS before and after a rapid thermal anneal (RTA) at a high temperature of 1000 degrees C. The thinner film of HfN was fully oxidized and HfSiON was formed after oxidation; Si atoms of HfSiON were obtained as a result of out-diffusion from the substrate. However, a majority of Hf-N bonds in the thicker sample remained unoxidized after oxidation, and subsequent annealing at 1000 degrees C revealed bond breaking of Hf-N, N loss, and bond formation of Hf-O. This suggested that the incorporation of O into the film was the main channel for N loss during high-temperature annealing. The high-resolution cross-sectional transmission electron microscopy (CS-TEM) results indicated that the thinner film was amorphous and the thicker one, crystalline. The existence of HfSiON at the interface in the thinner sample before RTA was considered to suppress the crystallization. Copyright (C) 2008 John Wiley & Sons, Ltd.