NSEU Sensitivity of SRAM-based FPGAs

Joe Fabula, Austin Lesea, Carl Carmichael, and Saar Drimer
Xilinx Corp.

Summary

A study has been performed that verified and, more importantly quantified, the logic sensitivities of advanced sub-micron SRAM-based Xilinx FPGAs to the effects of the natural (real world) atmospheric neutron environment. Various technologies ranging from 0.5 micron CMOS down to 0.09 microns CMOS have been evaluated.

Measurements of the critical bit cross section of the storage elements of a select number of families of such devices, encompassing the range of 5,000 gate density devices (fabricated in a 0.5 micron DLM technology and operating at 5.0 volts) to 8,000,000 gate density devices (fabricated in 0.09 micron 8LM technology and operating at 1.2 volts) have been made. Data will be presented on the measured per bit proton and per bit neutron cross sections of these devices. Proton cross sections were measured using the Crocker Nuclear Laboratories Cyclotron (at 63 MEV) and using the University of Indiana Cyclotron Facility (over the range of 50-200 MeV). Critical bit neutron cross section data will also be presented on these technologies, taken utilizing the Hess spectrum of spallation neutrons available at the LANSCE facility of Los Alamos National Laboratories.

Then, the results of true atmospheric neutron exposure of a very large number of devices (the total number of exposed latches exceeded 1.9 terabits at each test implementation, and the tests were operated for periods of three to six months) at three elevations (sea level, 5200 feet and 12,250 feet) will be presented, and this data will be used to calibrate the accelerated test methodologies. Finally, the calculation methodology used to assess the logic MTBF of these devices will be presented, along with a tabulation of the MTBFs at various altitudes and latitudes in support of terrestrial and avionics applications.