Soft Error Rates in 65nm SRAMs--Analysis of new Phenomena

Soft error rates measured on embedded SRAMs in a 65 nm CMOS technology show a significant increase of the error rate induced by neutron radiation (NSER), while the number of soft errors due to alpha radiation (ASER) is within the expected range. In this paper it will be discussed, that the increase of the NSER values is caused by an unexpected high number of single event upsets (SEU) that flip multiple SRAM cells simultaneously (multi-bit upset). As root cause radiation induced switching of parasitic bipolar transistors was found.