Interface-state generation under radiation and high-field stressing in reoxidized nitrided oxide MOS capacitors

The time evolution of interface-state (D_it) buildup following radiation and high-field stressing in MOS capacitors was compared for 45-nm-thick conventional `dry´ oxide (SiO₂) and reoxidized nitrided oxide (RNO). While the oxide shows the expected postirradiation increase of D_it with time under positive bias, the RNO shows no time-dependent buildup. This indicates that hydrogen transport, widely held responsible for the slow evolution of D_it after radiation, does not play a role in D_it generation in RNO. It is suggested that this is due to a blocking effect of the nitrogen-rich oxynitride layer which is known to exist in RNO near the silicon/silicon-dioxide interface, and which inhibits the drift of hydrogen ions to the interface. Exposure of the capacitors to a hydrogen ambient after irradiation confirms that for RNO, unlike the case of oxide, there is no increase of D_it due to hydrogen effects. Postirradiation electron injection in RNO suggests that trapped-hole recombination may be responsible for the small D_it generation seen in RNO