Evaluation of radiation sensor aspects of Er2O3 MOS capacitors under zero gate bias

Abstract

The aim of the present study is to investigate the usage of Erbium Oxide (Er2O3) as a gate dielectric in MOS-based radiation sensors. Er2O3 thin films were deposited on a p-type Si (100) substrate via RF magnetron sputtering and were annealed at 500 degrees C under N-2 ambient. The structural properties of the Er2O3 thin films were determined via XRD, FTIR, and AFM analyses. The Erbium silicate formation was not observed in the XRD and FTIR spectra. The roughness root-mean-square was measured as 16.4 nm by the AFM analysis. Following the description of the film, the Er2O3 MOS capacitors were fabricated and irradiated by a Co-60 radioactive source in different doses varying from 4 Gy to 76 Gy. The capacitance-voltage (C-V) curves shifted to the right side compared to the ideal one in the dose range of 4-16 Gy and to the left side from 16 Gy to 76 Gy. The oxide trapped charge density increased with an increasing irradiation dose. A significant variation in the interface states densities was not observed, the value of which always remained in the order of 10(10) eV cm(-2) in the studied dose range. Based on these results, it can be said that gamma radiation does not cause a significant deterioration during irradiation. The calibration curve of the capacitor was obtained from the flat band voltage shifts depending on the gamma dose. Some electrical parameters, such as the barrier height and acceptor concentration, were investigated depending on the gamma dose. The sensitivity of the capacitor was determined to be 107 mV/Gy for the dose range of 4-16 Gy and 61 mV/Gy for the dose range of 16-76. These results showed that the Er2O3 MOS capacitor was more sensitive to the gamma radiation compared to the SiO2 and Sm2O3-based capacitors.