Threshold Voltage Tunability of p-Channel Metal Oxide Semiconductor Field-Effect Transistor with Ternary Hf_xMo_yN_z Metal Gate and Gd_2O_3 High-K Gate Dielectric

摘要

p-channel metal oxide semiconductor field-effect transistor (pMOSFET) devices with a ternary Hf_xMo_yN_z metal gate and a Gd_2O_3 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. Hf_xMO_yN_z thin films were cosputtered from pure hafnium (Hf) and molybdenum (Mo) targets in nitrogen (N_2) and argon (Ar) mixtures. The Hf_xMO_yN_z thin films have low resistivity and high thermal stability up to 950 ℃. The threshold voltage (V_(th)) of the Hf_xMo_yN_z/ Gd_2O_3 pMOSFET can be tuned from -0.6 to -0.08V by controlling the nitrogen flow ratio. Moreover, there is little negative bias temperature instability (NBTI) degradation of the Hf_xMo_yN_z/Gd_2O_3 pMOSFET device. Compared with the Hf_xMo_yN_z/SiO_2 pMOSFET, the Hf_xMo_yN_z/Gd_2O_3 pMOSFET has a small threshold voltage modulation owing to the extrinsic Fermi level effect at the Hf_xMo_yN_z and Gd_2O_3 interface. A physical model has been proposed to explaln the extrinsic Fermi level pinning effect of the Hf_xMo_yN_z/Gd_2O_3 pMOSFET device.