Process techniques and electrical characterization for high-k (HfOxNy) gate dielectric in MOS devices

Effects of nitrogen concentration profiles in HfO_xN_y on the electrical properties of metal-oxide-semiconductor (MOS) devices were investigated. The nitrogen concentration profiles in HfO_xN_y gate dielectric was adjusted by sputtering the Hf target in ambient of modulated nitrogen flow. The trapped charges in HfO_xN_y dielectric are positive. The current-conduction mechanisms of HfO_xN_y film at the low- and high-electrical field are dominated by Schottky emission and Frenkel-Poole emission, respectively. The mechanism relevant to the relatively larger stress induced leakage current (SILC) at low electrical fields can be explained by the trap-assisted tunneling. On the other hand, the relatively smaller leakage current found at high electric fields can be attributed to the electron trapping in bulk defects. Smaller flat-band voltage shift and SILC are observed for devices with HfO_xN_y dielectric containing more nitrogen at the dielectric/Si interface or/and less bulk nitrogen, which can be attributed to less interface strain/stress and bulk trap. Electrical characterization of high-k MOSFET was performed by charge-pumping and charge separation techniques. Some interesting results are quite different from those generally observed in SiO: MOSFETs.