Investigation of the Impact of Angles and Rotation of Low-Energy Protons in SRAM Cells Down to 16 nm

This work presents the single-event upset (SEU) responses of four SRAM devices (65, 40, 28, and 16 nm) measured at different angles of incidence and orientation of the device with respect to the low-energy proton (LEP) beam direction. Experimental data are discussed with the support of multiphysics and multiscale simulations. Difference of one order of magnitude is observed for SRAMs irradiated between the different directions the beam is entering the device. The conclusions drawn from the simulation results suggest that the difference in the SEU cross section could be attributed to the charge sharing between the n-well and p-well of the two inverters of the SRAM bit. The consequent feedback reduces the overall ionization effects in the SRAM cell when exposed to LEPs.