Threshold voltage variation in SOI Schottky-barrier MOSFETs

Abstract

The inhomogeneity of Schottky-barrier (SB) height ΦB is found to strongly affect the threshold voltage Vth of SB-MOSFETs fabricated in ultrathin body silicon-on-insulator (SOI). The magnitude of this influence is dependent on gate oxide thickness tox and SOI body thickness tsi; the contribution of inhomogeneity to the Vth variation becomes less pronounced with smaller tox and/or larger tsi. Moreover, an enhanced Vth variation is observed for devices with dopant segregation used for reduction of the effective ΦB. Furthermore, a multigate structure is found to help suppress the Vth variation by improving carrier injection through reduction of its sensitivity to the ΦB inhomogeneity. A new method for extraction of ΦB from room temperature transfer characteristics is also presented. © 2008 IEEE.