Proposal of alternative sensitive region for MOS based radiation sensors: Yb2O3

Abstract

The purpose of this study is to investigate the usability of ytterbium oxide (Yb2O3) as a sensitive region/gate oxide in metal oxide semiconductor (MOS) based dosimeters and to determine the advantages and disadvantages of this device relative to its alternatives. For this purpose, amorphous Yb2O3 films were grown on p type Si by radio-frequency magnetron sputtering and aluminum (Al) was used as front and back ohmic contacts of the capacitor. Yb2O3 MOS devices were irradiated incrementally to the total dose of 70 Gy by Co-60 radioactive source. The capacitance-voltage measurements were performed at low (100 kHz) and high (1 MHz) frequencies to examine the behavior of the traps. The sensitivity of the device for 70 Gy was obtained using flat band voltage shifts as 27.5 +/- 1.1 and 28.1 +/- 1.3 mV/Gy for 100 kHz and 1 MHz, respectively. The changes in the oxide trap charge densities in the studied dose between 0.5 and 70 Gy are in the ranges of (1.09 +/- 0.04) x 10(11)-(1.23 +/- 0.05) x 10(12) cm(-2) for 100 kHz and (-3.26 +/- 0.08) x 10(10)-(8.16 +/- 0.35) x 10(11) cm(-2) for 1 MHz. For both frequencies, there was no significant change in the interface trap charge densities over the applied dose and the density of these traps remained in order of 10(11) cm(-2) after each applied dose. The percentage fading were measured at only 1 MHz for evaluation of the device's dose storage capacity and the results varied from 4% (5 min) to -19% (50 min). An almost constant fading value was obtained after 20 min from irradiation. The capacitor's sensitivity was found to be higher than those of similar devices composed of HfO2, La2O3, SiO2, Sm2O3, and Y2O3. Yb2O3 would be a promising candidate for a new generation of MOS based radiation sensors.