Subthreshold response of a MOSFET to radiation effects

A study of the degradation of the subthreshold swing in a general-purpose pMOSFET is carried out to evaluate its use as a dosimetric parameter. Its reliability in terms of sensitivity, linearity, and reproducibility is experimentally tested and compared with the threshold voltage shift under gamma rays from a 60Co source up to 56 Gy, typical in radiotherapy treatments. The dependence of the subthreshold swing as a function of temperature is characterized and modeled as a mean for thermal compensation when used for dose measurement. Very promising results have been obtained for the subthreshold swing as a complementary dosimetric parameter to the threshold voltage for enhancing the confidence of dose verification systems based on MOSFETs.