Effects of Scaling on Analog FoMs of UTBB FD-SOI MOS Transistors: A Detailed Analysis

In this article, the combined effect of BOX thickness ( ${T}_{\text {BOX}}$ ) and ground-plane (GP) doping ( ${N}_{\text {GP}}$ ) on channel carrier mobility and analog figures of merit (FoMs) is investigated. It is reported that the thin BOX along with higher ${N}_{\text {GP}}$ will limit the electron/hole mobility of ultrathin body and BOX fully depleted silicon-on-insulator (UTBB FD-SOI) MOS transistors. The physics responsible for this observation is discussed in detail. The contrasting behavior of different GPs, the effect of ${T}_{\text {BOX}}$ scaling, and gate-length scaling on device behavior is also analyzed. It is also shown that in advanced UTBB FD-SOI MOS transistors, a tradeoff exists between transistor intrinsic gain, cutoff frequency, and non-linearity. In nMOS transistors, the best intrinsic gain and cut-off frequency can be achieved with ultrathin BOX and n-type GP (or with no GP), whereas the best linearity can be achieved with ultrathin BOX and p-type GP implant.