Poly-Si-Gate-Related Variability in Decananometer MOSFETs With Conventional Architecture

In this paper, we present a comprehensive statistical 3-D simulation study of the effect of polysilicon (poly-Si) gate granularity on the threshold voltage variability in decananometer MOSFETs with conventional (bulk) architecture. Initially, the effect of both the pinning of the Fermi level and the doping nonuniformity at the poly-Si grain boundaries are studied and compared considering a single grain boundary crossing through the middle of the channel for different pinning positions and doping concentrations at the boundary. This is followed by systematic simulation results for the impact of the grain-size distribution on the standard deviation of the threshold voltage in a simple 30 30 nm MOSFET with uniform channel doping for different pinning positions and doping levels at the grain boundaries. Finally, simulation results for the magnitude of the threshold voltage variations induced by the poly-Si granularity are presented for a set of carefully scaled ldquorealisticrdquo bulk MOSFETs with gate lengths of 35, 25, 18, 13, and 9 nm and are compared with the variations introduced by random discrete dopants and line-edge roughness.