Thermal decomposition behavior of the HfO2/SiO2/Si system

We report on the thermal decomposition of uncapped, ultrathin HfO2 films grown by chemical vapor deposition on SiO2/Si(100) substrates. Medium energy ion scattering, x-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy were used to examine the films after they had been annealed in vacuum to 900–1050 °C. Film decomposition is a strong function of the HfO2 overlayer thickness at a given temperature, but the underlying SiO2 layer thickness does not significantly affect the thermal stability of the HfO2 film. Oxygen diffusion in the system was monitored by 16O/18O isotopic labeling methods. Direct evidence of silicide formation is observed upon decomposition.