Molybdenum Gate Work Function Engineering for Ultra-Thin-Body Silicon-on-Insulator (UTB SOI) MOSFETs

In this paper, we demonstrate threshold voltage (V-T) adjustment for Mo-gated ultra-thin-body (UTB) silicon-on-insulator (SOI) MOSFETs by nitrogen (N-14(+)) implantation for the first time. In order to avoid dopant fluctuation effects and impurity scattering, a lightly doped (10(15) cm(-3)) Si body is used without degrading the short channel effects by virtue of an ultra-thin body. Metallic gate materials are desirable for reducing resistance, and for eliminating the gate depletion effect as well as dopant penetration through an ultra-thin gate dielectric. The VT for Mo-gated UTB SOI p-channel MOSFET is -0.2 V, and it can be shifted by approximately -65 mV for every 1 x 10(15) cm(-2) increment in N-14(+) implant dose. An estimated dose of 6-8 x 10(15) cm(-2) is needed for achieving low V-T (0.2-0.3 V) Mo-gated UTB SOI n-channel MOSFET.