Investigation of lanthanum and hafnium-based dielectric films by X-ray reflectivity, spectroscopic ellipsometry and X-ray photoelectron spectroscopy

LaAlO 3 and HfAl x O y thin films have been deposited by magnetron sputtering for replacement of SiO 2 in new Complementary Metal Oxide Semiconductor applications. A three-layer model was found both in X-ray reflectivity (XRR) and spectroscopic ellipsometry (SE) analysis to be the best optical model for these two high-K materials. It was composed of an interfacial layer, covered by a layer of pure LaAlO 3 or HfAl x O y , and a surface-roughness layer. In the case of LaAlO 3 and HfAl x O y directly deposited on Si, the interfacial layer is a mixture of high-k material and amorphous-Si inclusions, which thickness is growing after post-deposition annealing (PDA) in O 2 at 600 °C. On the contrary, for films deposited on thermally nitrided Si, the SiON-like interface did not change significantly after a PDA in O 2 . XRR analysis showed that the dielectric/Si interface of HfAl x O y /SiON/Si structure had a significantly smaller roughness than those of HfAl x O y /Si. When being deposited on SiON/Si substrates, HfAl x O y , and to a lesser extent LaAlO 3 , demonstrate superior diffusion barrier properties pointed out by X-ray photoelectron spectroscopy.