Analysis of Oxygen and Nitrogen Redistribution at Interfaces of HfO2 with Laminate TiN/TiAl/TiN Electrodes

The physicochemical nature of the change in the effective work function (EWF) of aluminum doped TiN (using TiN/TiAl/TiN laminate structure) was studied by X-ray photoelectron spectroscopy with high kinetic energies (HAXPES). Comparative analysis of Si/SiO2/HfO2/TiN-TiAl-TiN and Si/SiO2/HfO2/TiN stacks reveals identical composition of the HfO2/TiN interfaces in both stacks. It was established that the EWF decrease for TiN/TiAl/TiN laminate electrode with respect to the "normal" value for TiN is related to redistribution of light N and O atoms in the bulk of TiN/TiAl/TiN instead of frequently supposed Al diffusion and formation of HfAlOx mixed oxide at the HfO2/TiN interface. Formation of nonstoichiometric TiNx, metallic Ti and Al, and AlN in the bulk of TiN/TiAl/TiN was revealed by HAXPES.