Characterisation of HfO₂ deposited by photo-induced chemical vapour deposition

The deposition of thin Hafnia (HfO₂) films on crystalline Si by photo-induced chemical vapour deposition (CVD) using 222 nm excimer lamps at temperatures between 300 and 450 °C is presented. Hafnium (IV) tetra-t-butoxide was used as the precursor, which was carried into the photochemical reaction chamber by flowing Ar carrier gas at a pressure of several mbar using a special precursor injection system. Films from approximately 6-70 nm in thickness with refractive indices from 1.60 to 1.85 were grown. The deposition rate measured by ellipsometry was found to be 15 nmmin^-1 at a temperature of 400 °C. The deposited HfO₂ films were characterised by various techniques. XRD showed that as-deposited HfO₂ films were basically amorphous. Fourier transform infrared spectroscopy, revealed that Hf-O absorption in the photo-CVD deposited HfO₂ films is quite different at various deposition parameters. The substrate temperature, system pressure and UV-annealing dependence of the physical and interfacial properties of these films will also be presented.