Fading of pMOS dosimeters over a long period of time

Abstract

The fading of radiation-sensitive p-channel metal-oxide-semiconductor field-effect transistors (known as RADFETs or pMOS dosimeters) over a long time period of 10 years after irradiation has been investigated. Fading is, in addition to sensitivity, another characteristic of pMOS radiation dosimeters. It is considered as the recovery of threshold voltage of irradiated pMOS dosimeters during ambient annealing without gate polarization. Usually, there are the fading data for few months after irradiation only. Although fading is a very important dosimetric characteristic, here it is given for the first time in the literature in such a long period of time. Two types of pMOS dosimeters with oxide thicknesses of 400 and 1000 nm are used. They are irradiated without and with a 5 V polarization on the gate. For the first time, the authors came to a very significant result that the key role in fading has the voltage applied during irradiation, but not the thickness of the oxide, and that the pMOS dosimeters irradiated with gate voltage of 5 V have greater fading than pMOS dosimeters irradiated without a gate voltage. Fitting of threshold voltage shift and fading, performed using the radiation-induced Eγ and Es traps, shows very good agreement with the experimental values.