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; 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.