Experimental and Analytical Study of the Responses of Nanoscale Devices to Neutrons Impinging at Various Incident Angles

Abstract

In harsh radiation environments, it is well known that the angle of incidence of impinging particles against the surface of the operating devices has significant effects on their sensitivity. This paper discusses the sensitivity underestimations that are made if particle isotropy is not taken into account, by means of an analytical study made with a single event upset predictive platform. To achieve this goal, experimental results carried out with a COTS bulk 130-nm non-volatile SRAM for various incident angles on 14.2 MeV neutrons are firstly discussed. Then, a modeling tool called MUSCA-SEP3 is used to predict the sensitivity of this memory under the same environmental conditions. Predictions and experimental results will be cross-checked, therefore the feasibility of this tool will be demonstrated for testing any other incident angle. Finally, an isotropic environment and an XY SRAM array will be emulated with MUSCA in order to demonstrate that the asymmetrical cross-sections that were observed experimentally for various incidence angles are due to the underlying asymmetry of the metalization/passivation layers within the device with respect to its active silicon. Conclusions will finally be drawn as for the importance of taking into account particle isotropy in radiationground tests.

SEE sensitivity of a COTS 28-nm SRAM-based FPGA under thermal neutrons and different incident angles

“…This is in agreement with the results regarding MBUs presented in Fig. 3: 2-and 3-bit MBU per-bit cross-sections obtained at different incident angles in the CRAM, but at the same time it contradicts the results that the authors obtained in a previous work [29] with 14-MeV neutrons on a 130-nm bulk memory, where the highest MCU sensitivity was measured at grazing angles.…”

“…The detailed analysis indicates two parameters that influence the occurrence level according to the direction; the ratio between the surface of drains/sources and the depth of dopant implantation and the distance travelled by the thermal neutron. These results are very different from those observed experimentally, and by simulation, for 14-MeV neutrons [29]. Indeed, a lower sensitivity in 14-MeV neutron tests was obtained for the front of the device than the grazing condition, while an opposite behavior is observed with thermal neutrons.…”

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

“…In each simulation, a particle is selected according to the input energy spectrum and angular properties. In this case, this is reduced to a normal incidence, although MUSCA-SEP3 is also capable of studying angular effects of incident particles, as demonstrated in another recent research [33]. Then, the starting point of the particle is selected as the central cell of the 11×11 grid of memory cells.…”