A comparison of statistical variation of threshold voltage in bulk silicon and SOI MOSFETs

Using previously developed models for the bulk and SOI (silicon-on-insulator) MOSFETs, the authors compare and analyze the statistical variation of the threshold voltage V_th in these MOSFETs with respect to variation of device parameters such as doping density, oxide thickness, and channel length. The statistical variation of the threshold voltage reduction ΔV_th for three values of channel length is shown. The statistical distribution is broadened with a pronounced asymmetry toward the higher value of ΔV_th. It is also noted that the statistical distribution in the SOI MOSFET is narrower than that of the bulk MOSFET. The optimized design region of a fully depleted SOI MOSFET with a threshold voltage distribution smaller than its bulk silicon counterpart is shown