High energy Si ion irradiation effects on 10 nm thick oxide MOS capacitors

We investigated the charge trapping properties of 10 nm thick oxide metal-oxide-semiconductor capacitors after 158 MeV silicon ion beam exposure up to 20 Mrad(Si) dose. Devices were biased during irradiation by a positive or negative gate voltage to drift radiation induced holes to the silicon/oxide and gate/oxide interface, respectively. Experimental results show that the radiation induced effective positive charge increases linearly with dose and is larger for the positive biased devices. The positive charge recombines with electrons injected in the oxide by Fowler-Nordheim tunnelling. After positive charge recombination a net negative charge builds up, due to electron trapping in radiation induced neutral defects. The negative charge density increases linearly with dose and it is larger for positive biased devices. The negative charge centroid is close to the oxide centre. The probability that one effective negative charge is generated by one radiation induced effective positive charge is 0.153 +/- 0.005.