Geant4 and Microelectronics – Recent Successes, Looming Concerns Robert Weller, Robert Reed, Mike King, Marcus Mendenhall, Makoto Asai Supported in part by the DTRA Basic Research Program 2014 Geant4 Space Users Workshop

Energetic Electron-Induced Single-Event Upsets in SRAMs

Single Electron-Induced SEU Particle Strikes Sensitive Node of SRAM Energetic electron creates e-h pairs Circuit Transient Response Results in Error

Increasing Sensitivity of SRAMs 65 45 32 22 16

Motivation For Electron-Induce SEU Critical charge estimates for 22 nm on the order of 0.1 fC – 0.35 fC at nominal supply voltage Devices are becoming increasingly sensitive to lightly ionizing particles Low-energy Protons Muons MRED simulations suggested electrons can deposit energy in excess of critical charge estimates - 2.6 keV or 0.12fC 10 keV electron 50 nm Cube

Experimental Method #1 – X-ray Irradiation 28 nm and 45 nm SRAMs X-rays used to generate secondary energetic electrons Dose rate of 100 rad(SiO2)/min Reduced bias testing Devices were designed and verified experimentally to be functional at all supply voltages used in this experiment Incident X-ray Sensitive Volume Energetic Electron

Upsets in 28 & 45 nm SRAMs SEU probability Eliminated TID, photocurrents, and functionality as source of observed errors No significant parametric degradation; power supply current stable

Experimental Method #2 – Electron Irradiation Arnold Engineering Development Center Space Threat Assessment Testbed (STAT) Electrons, protons, photons, and others AEDC

Electron-Induced SEUs 28 nm SRAMs 100 keV and 40 keV electrons Flux = 2.6 × 107 cm-2 s-1 Fluence = 1 × 1010 to 5 × 1010 cm-2 Reduced bias testing Condition SEU Probability Standard Error 0.45 V, 100 keV 1.71E-07 1.19E-08 0.5 V, 100 keV 5.04E-08 7.06E-09 0.45 V, 40 keV 3.13E-07 2.55E-08

Experimental Method #3 – Sr-90 electron source The Use of Strontium-90 Beta Radiotherapy as Adjuvant Treatment for Conjunctival Melanoma Cohen VM, Papastefanou VP, Liu S, Stoker I, Hungerford JL - J Oncol (2013

Potential Space Environments Solar activity (solar flares, CMEs, solar wind, photons) Trapped particle Environment (Earth, Jupiter, etc..) Bremsstrahlung produce by primary environment interactions with S/C Beta decay in packaging Activated nuclei in S/C Local delta-rays (generated by heavy-ions) Shower produced by high-energy (~TeV) ions interacting with S/C

Need to identify critical space radiation environments Conclusions Provided evidence of single electron-induced SEU in 28 nm and 45 nm technologies Electron-induced SEU primarily a concern for low-power applications, may impact more sensitive current generation ICs at nominal supply voltage Modeling of electron transport down to very low energies may be an important issue for future technology Need to identify critical space radiation environments

Cubesat Program Update

Satellite Program Overview Goal: Provide a low cost on-orbit system to improve our understanding of the impact of space radiation environments on satellite components and systems One system delivered for S/C integration One slated for summer 2014 delivery Another TBD experiment schedule for early 2016 Warren - Cubesat

RadFxSat Concept Example Spacecraft Example Payload Warren - Cubesat Vanderbilt provides payload CubeSat partner provides spacecraft bus Example Spacecraft Example Payload Warren - Cubesat

Senior Design Teams 2012 team 2013 team 2014 team Designed an latchup experiment that will be flown on the RadFx-1 2013 team Preliminary design of an SRAM tester 2014 team Evaluated commercial CubeSat S/C for radiation effects