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

Abstract

The time evolution of interface-state (Dit) 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 Dit 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 Dit after radiation, does not play a role in Dit 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 Dit due to hydrogen effects. Postirradiation electron injection in RNO suggests that trapped-hole recombination may be responsible for the small Dit generation seen in RNO.