FREEZE-OUT CHARACTERIZATION OF RADIATION HARDENED N+ POLYSILICON GATE CMOS TRANSISTORS

Freeze-out behavior of radiation hardened N+ polysilicon gate CMOS devices is studied at liquid-nitrogen temperature before and after irradiation at different dose levels. Explanations are given for the threshold voltage variations and freeze-out effects both before and after irradiation. The degree of freeze-out of the counterdope implant is controlled by temperature, applied gate potential and applied body-to-source potential. Based on experimental results of this work, freeze-out is not significantly affected by irradiation dose, or the magnitude of the gate bias during radiation.