Optimization of Low-Voltage-Operating Conditions for MG-MOSFETs

Adaptive threshold-voltage controlling of thin-film multi-gate (MG) MOSFETs, using independent back-gate biasing, is applied for realizing latency and power optimization. The controlling-method validity for low-voltage operation is analyzed with the compact model HiSIM-MG, considering all internally induced charges specific for MG controlling. Current-drivability degradations, due to back-gate-charge contribution under positively-biased back-gate voltage and existence of an optimized operating condition, are confirmed. The optimized operating condition is shown to keep the back-gate charge under the weak inversion with a corresponding relatively small back-gate charge. It is also demonstrated, that an input-voltage optimization accompanies the back-gate-voltage optimization, sustaining the optimized low power loss with low input voltage. Circuit-performance improvement of 27% by about 30% reduction of substrate thickness, while keeping switching-power loss small, is also verified.