INTERFACE-STATE GENERATION UNDER RADIATION AND HIGH-FIELD STRESSING IN REOXIDIZED NITRIDED OXIDE MOS CAPACITORS

The time evolution of interface-state (D(it)) build-up following radiation and high-field stressing in metal-oxide-semiconductor (MOS) capacitors has been compared for 45 nm thick conventional ''dry'' oxide (SiO2) and reoxidized nitrided oxide (RNO). While the oxide shows the expected post-irradiation increase of D(it) with time under positive bias, the RNO shows no time-dependent build-up whatsoever. 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. We suggest 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. Post-irradiation electron injection in RNO suggests that trapped-hole recombination may be responsible for the small D(it) generation seen in RNO.