Interface Formation and Electrical Properties of TiOxNy/HfO2/Si Structure

Abstract

In this work, interface formation and electrical properties of the interface between TiOxNy 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 TiOxNy layers at room temperature. Phase identification of TiOxNy layers before and after thermal annealing of TiOxNy(100 nm)/HfO2/Si by X-ray diffraction (XRD) indicates the formation of TiO1-zNz with the preferential orientations in (111), (200) and (220) directions. Depth profiling analysis of Ti, Si, Hf, N, and O element for TiOxNy(50 nm)/HfO2/Si structure by Auger electron spectroscopy (AES) shows the increased oxidation of TiOxNy layers at elevated annealing temperature, TA = 800°C. Investigation of the interfacial reaction of TiOxNy(5 nm)/HfO2 by depth profiling using X-ray photoelectron spectroscopy (XPS) shows the existence of mixture of TiO1-zNz and TiO2 (or TiO) phase and increased fraction of TiO2 phase and Hf–O bondings for the samples annealed at the elevated annealing temperature, TA = 800°C. Sheet resistance of TiOxNy/HfO2/Si systems measured by a four-point probe shows the initial decrease in RS values but the abrupt increase in RS values at TA = 800°C. The combined results indicate that TiOxNy 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 TiOxNy layers at the elevated annealing temperature of 800°C.