Quantization effects in silicided and metal gate MOSFETs

Abstract

Great improvements in MOSFET performance can be obtained when metal or fully silicided gates are used rather than their polysilicon counterparts. However, we will show that although the non-metallic effects are partially suppressed, accumulation and depletion regions are still present, even when metal gates are used. Poisson and Schrodinger equations are self-consistently solved to study the actual charge physics underneath the metal or silicided gate. After introducing the physical context, we highlight the overestimation in the extraction of the oxide thickness from C-V measurements. An error of up to 15% in the evaluation of gate to channel capacitance was found due to the quantization of the holes in accumulation. Finally, the impact of a substoichiometric insulator layer and the band-gap narrowing of highly-doped polysilicon gates are also discussed.