Threshold voltage variation in SOI Schottky-barrier MOSFETs

The inhomogeneity of Schottky-barrier (SB) height Phi(B) is found to strongly affect the threshold voltage V-th Of SB-MOSFETs fabricated in ultrathin body silicon-on-insulator (SOI). The magnitude of this influence is dependent on gate oxide thickness t(ox) and SOI body thickness t(si); the contribution of inhomogeneity to the V-th variation becomes less pronounced with smaller t(ox) and/or larger t(si). Moreover, an enhanced V-th variation is observed for devices with dopant segregation used for reduction of the effective Phi(B). Furthermore, a multigate structure is found to help suppress the V-th variation by improving carrier injection through reduction of its sensitivity to the Phi(B) inhomogeneity. A new method for extraction of Phi(B) from room temperature transfer characteristics is also presented.