Evaluation of a COTS 65-nm SRAM Under 15 MeV Protons and 14 MeV Neutrons at Low VDD

Abstract

This paper presents an experimental study on the sensitivity of a Commercial-Off-The-Shelf (COTS) bulk 65-nm SRAM under 15.6 MeV proton irradiation when powered up at ultra-low bias voltage. Tests were run on stand-by and while reading the memory. Results show obvious evidence indicating that decreasing the bias voltage below 1 V exponentially increases the number of observed errors. SBUs and MCUs (mostly with vertical shapes according to the manufacturers' layout) are reported and their behavior is analyzed in this paper. Predictions on the SEU sensitivity obtained with the MUSCA-SEP3 modeling tool are also provided, and compared with the experimental results. These are also compared with 14.2 MeV neutrons, showing a significant difference in the cross-sections for both irradiation sources. TID tests and GEANT4 simulations were also run to check for the reason behind the difference in the cross-section between these two particles.

Single Event Upsets Under Proton, Thermal, and Fast Neutron Irradiation in Emerging Nonvolatile Memories

“…Neutron fluxes were either 2.1×10 9 or 2.4×10 9 n/cm 2 /s (because they were carried out at different times in the same facility), but in any case, the table shows the total neutron fluences for each one of the rounds. Also, different bias voltages were tested in order to evaluate the possible effect of Dynamic Voltage Scaling (DVS) on the memory, which is known to have negative effects on the reliability of SRAMs [63], [64], [73].…”

“…Despite the low proton energy, the different device technologies were sensitive enough without delidding them. Furthermore, previous tests conducted by the CNA group with similar devices indicate that the covering (epoxy or similar) thickness on the order of 900-µm as maximum allows working with incident proton energies on the order of 15 MeV to study SEEs in technologies below 130-nm [63], [64].…”

Impact of the Bitcell Topology on the Multiple-Cell Upsets Observed in VLSI Nanoscale SRAMs

“…Additionally, new proton ones were carried out in May 2019 at the cyclotron existing at the Centro Nacional de Aceleradores (CNA) in Sevilla, Spain [30], [31]. Proton data on Device C were published in [32].…”