Interface formation and electrical properties of TiO_xN_y/HfO₂/Si structure

In this work, interface formation and electrical properties of the interface between TiO_xN_y and HfO₂ for application of gate structure were investigated as a function of annealing temperature. HfO₂ layers were formed at 500 °C by the thermal oxidation of the sputter-deposited Hf layers on n-Si (001) and followed by reactive DC magnetron sputter deposition of TiO_xN_y layers at room temperature. Phase identification of TiO_xN_y layers before and after thermal annealing of TiO_xN_y(100 nm)/HfO₂/Si by X-ray diffraction (XRD) indicates the formation of TiO_1-zN_z with the preferential orientations in (111), (200) and (220) directions. Depth profiling analysis of Ti, Si, Hr, N, and O element for TiO_xN_y(50 nm)/HfO₂/Si structure by Auger electron spectroscopy (AES) shows the increased oxidation of TiO_xN_y layers at elevated annealing temperature. T_A = 800 °C. Investigation of the interfacial reaction of TiO_xN_y(5 nm)/HfO₂ by depth profiling using X-ray photoelectron spectroscopy (XPS) shows the existence of mixture of TiO_1-zN_z and TiO₂ (or TiO) phase and increased fraction of TiO₂ phase and Hf-O bondings for the samples annealed at the elevated annealing temperature, T_A = 800 °C. Sheet resistance of TiO_xN_y/HfO₂/Si systems measured by a four-point probe shows the initial decrease in R_S values but the abrupt increase in R_S values at T_A = 800 °C. The combined results indicate that TiO_xN_y layer acts as an effective diffusion barrier for Hf and O element in the HfO₂ layer at the annealing temperature ≤700 °C, but O and Hf diffused out of the HfO₂ layers reacted with TiO_xN_y layers at the elevated annealing temperature of 800 °C.