Accuracy Improvement of MOSFET Dosimeters in Case of Variation in Thermal Parameters

Abstract

Extraction of radiation dose information from MOSFET (RADFET) based dosimetry systems usually relies on biasing the MOSFET during readout at zero temperature coefficient drain current ( \mbi IZTC), measured before irradiation. This current can vary due to accumulated radiation doses and thermal fluctuations, which degrades dosimetric accuracy. This work presents a method to reduce thermal drift related to this \mbi IZTC shift. It is based on biasing with two carefully chosen currents during readout according to a thermal model suitable for MOSFETs. An experiment including irradiation and thermal cycles has been carried out to test the proposed method, using five types of RADFETs with three different gate-oxide thicknesses. If we compare the thermal drift of the output voltage measured using our proposed method with that measured using the usual constant \mbi IZTC method, the linear thermal coefficient shows reductions of 33% to 80% for \mbiIZTC shifts between -15% and + 65%.