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

Abstract

In this paper, we demonstrate threshold voltage (VT) adjustment for Mo-gated ultra-thin-body (UTB) silicon-on-insulator (SOI) MOSFETs by nitrogen (14N+) implantation for the first time. In order to avoid dopant fluctuation effects and impurity scattering, a lightly doped (1015 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 1×1015 cm-2 increment in 14N+ implant dose. An estimated dose of 6–8×1015 cm-2 is needed for achieving low VT (0.2–0.3 V) Mo-gated UTB SOI n-channel MOSFET.