FET-based radiation sensors with Er2O3 gate dielectric

Pre-irradiation device characteristics, gamma radiation response, and possible use in radiation dosimetry have been investigated for MOSFETs with a 100 nm thick Er2O3 gate dielectric. The performance of these novel devices has been compared with that of commercial pMOS dosimeters (RadFETs) with a standard SiO2 gate oxide of the same thickness. The radiation sensitivity of the Er2O3 is significantly higher than that of SiO2, and this is particularly pronounced at lower dose levels. Significantly larger numbers of positive charges are trapped in the Er2O3 dielectric than in SiO2 during irradiation exposure, resulting in increased threshold voltage shift. After two weeks of room temperature annealing, 11.9% and 24.0% fading have been observed in SiO2 and Er2O3 samples, respectively. Higher fading for Er2O3 may be related to higher number of shallow traps close to the dielectric/silicon interface. These initial results are promising for the possible use of Er2O3 as a new gate dielectric in pMOS dosimeters. The observed enhancement of device sensitivity can be a milestone for the introduction of the pMOS dosimeters in personal dosimetry applications.