Silicon thickness fluctuation scattering dependence of electron mobility in ultrathin body silicon-on-insulator n-metal-oxide-semiconductor field-effect transistors

Abstract

A matrix element for thickness fluctuation (δTSOI) scattering was derived to demonstrate the mobility dependence on Eeff, especially at a low inversion charge concentration, with an ultrathin channel thickness below 7 nm. This case contrasts other research with a lack of such dependence on either thick silicon-on-insulator (SOI) metal-oxide-semiconductor field-effect transistors (MOSFETs) or bulk MOSFETs. Our matrix element implies that the quantized energy fluctuation associated with δTSOI varies with the average distance of electrons from the surface interface. In particular, it implies the effects of the change in transverse potential on the subband energy fluctuation for each subband, which results in a different matrix element for each applied gate bias. By using this matrix element model, the low-field electron mobility was shown to depend not only on TSi but also on Eeff. Furthermore, the results of a simulation of electron mobility degradation as a function of TSi at low Eeff agreed well with previous experimental results.