Monitoring SEU parameters at reduced bias (CMOS SRAM)

SEU (single event upset) sensitivity of a CMOS SRAM (static random-access memory) increases with decreasing bias in such a manner that the critical charge exhibits a linear dependence on bias. This should allow proton and neutron monitoring of SEU parameters even for radiation-hardened devices. The sensitivity of SEU rates to the thickness of the sensitive volume is demonstrated, and procedures for determining the SEU parameters using protons are outlined. A method for determining the thickness of the sensitive volume using SEU measurements at normal and grazing incidence has been developed. Values determined by this procedure agree with values obtained with large collection measurements, SEM measurements, and estimates from the thickness of the epi-layer.< >