Saturation threshold voltage degradation in deep-submicrometer fully depleted SOI nMOSFETs operating in cryogenic environments

摘要

This work demonstrated that the saturation threshold voltage of short-channel SOI nMOSFETs degrades as the temperature is reduced. The V/sub T/ degradation at low temperatures is caused by a combination between the floating-body and impact ionization effects, increasing the gain of the parasitic bipolar structure. The halo or pocket implantation contributes for the enhanced V/sub T/ degradation at lower temperatures. The absence of halo efficiently reduces both the V/sub T/ variation and the V/sub T/ degradation in cryogenic operation. A negative biasing of the back gate tends to enhance the V/sub T/ degradation with temperature.