A simple analytical model of counter doping in a uniformly and heavily doped channel region of MOSFETS

Abstract

We analyze counter doping into a heavily and uniformly doped channel MOSFET region, which enabled us to suppress short channel effects with a proper threshold voltage V th. We derive a model for the relation between the counter doping conditions and V th and verify its validity with numerical and experimental data. We show that V th is determined by the centroid, R p, and dose, Φ D, of the counter doping and that V th is independent of the straggle ΔR p. We show that R p is almost invariable while ( ΔR p 2 + 2 Dt) is smaller than R p0 2, where R p0 is the initial R p which is the projected range of ion implantation, D is the diffusion coefficient of the counter doped impurities, and t is the annealing time. Using this technology we can expect superb short channel immunity with a reduced threshold voltage suitable for deep submicron gate length devices, which is shown from numerical analysis.