POSTIRRADIATION DOPANT PASSIVATION IN MOS CAPACITORS EXPOSED TO HIGH-DOSES OF X-RAYS

We study post-irradiation dopant passivation in p-type silicon metal-o xide-semiconductor capacitors exposed to high doses of low-energy x-ra ys. The passivation presents a logarithmic temporal behaviour which ca n be detected within less than one hour and continues to evolve for se veral thousand hours after irradiation. The time delay between irradia tion and passivation increases with radiation dose and a change in the anneal curve slope of oxide charge is associated with the onset of pa ssivation. These observations are discussed in terms of tunnelling ele ctrons from the silicon substrate, which may interact with traps in th e oxide and trigger the passivation by releasing hydrogen-related spec ies.