Total-dose radiation response and and post-irradiation annealing response of Hafnium capacitors

Abstract

the total-dose radiation response and post-irradiation annealing response of capacitors with Hafnium as the gate dielectric were studied in this work. HfO 2 capacitors with a gate dielectric thickness from 6 nm to 17 nm and electrode diameter of 0.6 mm were prepared on the p-Si substrate using plasma enhanced atomic layer deposition. The MOS capacitors are under zero bias during irradiation under 60Co gamma ray with total dose of 300 krad (Si)/ 1 Mrad (Si)/ 1.5 Mrad (Si)/ 2 Mrad (Si) at a dose rate of 80 rad (Si)/s. The maximum midgap voltage shifts is about −0.38 V, corresponding to net oxide-trapped charge densities projected to the surface of 1.77×1012 cm−2. But there seems no interface-trapped charge built up under irradiation in all samples. The midgap voltage shifts in these sample is linear dependence on oxide thickness and increase with the total dose. After annealing at 25 ° C and 100 ° C for 30 days, midgap voltage shifts decrease towards zero, indicating that the oxide trapped charge recover after longtime annealing. But there are interface trapped charges built up during the annealing, some negative, but some positive. The neutralization of oxide-trapped charges and build-up of the interface trapped charges are faster at 100 °C, and there are more remain oxide-trapped charges in samples annealed at 25 °C.