Investigation of molybdenum nitride gate on SiO2 and HfO2 for MOSFET application

Abstract

It has been reported that the work function of nitrided molybdenum (MoN) can be modulated by the atomic ratio of N/Mo and is suitable for gate material of complementary metal oxide semiconductor devices. In this work, we investigated the characteristics of MoNx prepared by reactively sputtering deposition from the gate electrode point of view. The main phase of the MoNx films is MoN(200). As the N/Mo ratio increases, the microstructure of MoNx film tends to be amorphous-like and the resistivity increases. After high-temperature annealing, the phase remains stable and grain size increases slightly. The HfO2 film has better immunity to sputtering damage than SiO2 film; therefore, the sputtering deposition method could be a choice of metal gate deposition as HfO2-based dielectric is used. The work function of MoNx increases with the increase of nitrogen content and tends to saturate at the valence band of Si. No Fermi-pinning effect is observed on HfO2 film. The work function and thermal stability of MoNx show good thermal stability on both SiO2 and HfO2 films up to 800 degrees C at least. All of these results indicate that MoN is a good candidate of gate electrode for p-type metal oxide semiconductor field effect transistors (pMOSFETs) or fully depleted SOI devices. (c) 2006 The Electrochemical Society.