1. 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

2. Energetic Electron-Induced Single-Event Upsets in SRAMs

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

4. Increasing Sensitivity of SRAMs

5. 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

6. 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

7. 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

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

9. 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

10. 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

11. 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

12. 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

13. Cubesat Program Update

14. 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

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

16. 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