Threshold Voltage Tunability of p-Channel Metal Oxide Semiconductor Field-Effect Transistor with Ternary HfxMoyNz Metal Gate and Gd2O3 High-k Gate Dielectric

Abstract

p-channel metal oxide semiconductor field-effect transistor (pMOSFET) devices with a ternary HfxMoyNz metal gate and a Gd2O3 high-k gate dielectric have been demonstrated for the first time. The nitrogen-concentration-control method is a simple and cost-effective technique for metal work-function modulation. HfxMoyNz thin films were cosputtered from pure hafnium (Hf) and molybdenum (Mo) targets in nitrogen (N2) and argon (Ar) mixtures. The HfxMoyNz thin films have low resistivity and high thermal stability up to 950 °C. The threshold voltage (Vth) of the HfxMoyNz/Gd2O3 pMOSFET can be tuned from -0.6 to -0.08 V by controlling the nitrogen flow ratio. Moreover, there is little negative bias temperature instability (NBTI) degradation of the HfxMoyNz/Gd2O3 pMOSFET device. Compared with the HfxMoyNz/SiO2 pMOSFET, the HfxMoyNz/Gd2O3 pMOSFET has a small threshold voltage modulation owing to the extrinsic Fermi level effect at the HfxMoyNz and Gd2O3 interface. A physical model has been proposed to explain the extrinsic Fermi level pinning effect of the HfxMoyNz/Gd2O3 pMOSFET device.