Radiation Effects in FPGAs & SEU Modeling Methodology Ketil Røed Høgskolen i Bergen

1. Radiation Effects in FPGAs & SEU Modeling Methodology Ketil Røed Høgskolen i Bergen

2. Topics • Radiation effects in the programmable logic • What is the problem / challange? • Key words: SEU rate in CERN ALICE TPC FEE FPGA • Experimental work • Why?  FPGA acceptance study • How?  Accelarated beam testing • Results • System design solution for radiation tolerant electronics • Simulation work • Why?  Predict SEU rate • How?  Monte Carlo based physics simulation • Results

3. Bly Bly Problemstilling: Elektronikk i strålingsmiljø • Hvordan oppfører elektronikk seg i et slikt miljø?

4. Field Programmable Gate Array, FPGA • Enkel sammenligning: • ASIC /Full Custom • Application Specific Integrated Circuit • FPGA • Field Programmable Gate Array

5. Field Programmable Gate Array, FPGA • En FPGA er laget av flere predefinerte elementer som kan konfigureres • Konfigurasjons-data lagres i SRAM => Rekonfigurerbar

6. 0101000101 0101011000 0101011110 1010110010 Transistor Field Programmable Gate Array, FPGA

7. + - - + + - - Transistor Transistor + + - - + - Transistor Og problemet var? Single Event Upset (SEU) 0101000101 0101011000 0101011110 1010110010 0101000101 0101011000 0101011110 1010100010

8. Utvikle testmetoder Utføre strålingstester Analyse Aksepttest: Arbeidsflyt Kartlegge Strålingsmiljø

9. Irradiation Test Facilities • The Svedberg Laboratory, TSL • 38 & 180 MeV protons • 90 MeV neutrons • 106-107 p/cm2s &103-104 n/cm2s • Beam spot radius 2 & 15 cm • The Oslo Cyclotron, OCL • 29 MeV protons • 106-107 p/cm2s • Beam spot radius: 2 cm

10. SEU Cross Section Result (Xilinx Virtex II Pro) • TSL (180 MeV p): σ = 2.14 x 10-14 cm2 / bit • OCL (29 MeV p): σ = 2.11 x 10-14 cm2 / bit • Independent experiment by Xilinx (atmospheric neutron spectra) • Rosetta+σ = 2.98 x 10-14 cm2 / bit • Scaled to the ALICE TPC radiation environment • Simulated* hadron flux 100-400 h/cm2s • Results per 216 FPGA / 4 hr unit Run • # SEU ~120 • # functional failures+ ~12 • Conservative numbers + Using an SEUPI: Single Event Upset Probability Impact = 10 Lesea et. al. The Rosetta Experiment, IEEE TRANS. ON DEVICE AND MATERIALS RELIABILITY, V 5, N3, 2005 *Fasso et. at, Radiation in the ALICE TPC detector, ALICE internal Note-TRD 2003

11. Alternativt Kontoret Fly (12000m) 1 FPGA CERN 216 FPGA CERN 1 FPGA OCL 1 feil / ~4000 timer 1 feil / ~400 timer 1 feil / ~100 timer 1 feil / ~0.5 timer 1 feil / ~sekunder Resultatet er i overkant av hva som kan tolereres

12. Systemløsning: Kontrollert rekonfigurering Fails during run

13. Komplisert resultat • Configuration memory is read back and bit-flips are corrected • The FPGA firmware design can be protected • Hamming bits • Triple Mode Redundancy • 1+2: Reduces the functional • failures to an acceptable level • Test flux: 106-107 p/cm2s • TPC flux: 100-400 h/cm2s • ~ factor 104 lower flux 1 2 3 1 1+2 No action Readback and Correction enabled Triple Modular Redundancy turned enabled

14. Ingen beskyttelse Enklere versjon Kombinasjonen har vist gode resultater i strålingstester Rekonfigurasjon + TMR % Feil under test < 5 <10 60-90 100

15. Next step: SEU Monte Carlo simulation Model the physical processes responsible for causing SEUs • General tools • FLUKA • GEANT4 • Dedicated tool • SEMM2 (IBM) • Not plug and play! • Utfordring: Tilpassing til vårt bruk Physics Software Tools SEU SIMULATION Semiconductor device technology

16. Reasearch Visit at IBM • 7 months research visit at IBM T.J. Watson Research Center, NY, USA(NFR Leiv Eiriksson mobilitetsstipend) • To learn the business of SEU modeling methodology

17. + -+ - - - + - + - + - - + Modeling Methodology Describe physical processes • Inelastic and elastic Interactions • Nuclear fragmentation • Transportation Target information • Technology • Layout • Material Radiation environment • Particle type • Energy & flux Modelling Software Tool Radiation event generator Charge transport & collection Critical Charge < SEU

18. Gate Source Drain N+ + - N+ + - + - + - + - + - + - + - + - + - + - + - + - + - P substrate The Physics of SEU p • Basic mechanism • Charge particle depositing energy in a device through ionization • If Qdep > Qcrit => SEU • TPC radiation environment* • Energetic Hadrons (E > 20 MeV) • Nuclear Interaction • Short range recoil-ion, • Typically E < 10 MeV Si(p,p α)Mg p α Mg Qdep * Fasso et. at, Radiation in the ALICE TPC detector, ALICE internal Note-TRD 2003

19. FIB: Focused Ion Beam Target Device Information • Investiagated using Focused Ion Beam tool (FIB)

20. Target Device Information: FIB Images ~5 um Device layer (90 nm transitors) Si substrate ~850 um Cu interconnet layer (0.4 um) FIB images are used to build a geometry model of our device

21. Radiation environment • Run new simulations • Add FEE geometry (C++ class in Aliroot) • SEU dedicated scoring regions http://aliceinfo.cern.ch/Public/panorama/WONDERS_QGP/index.html

22. SEMM2 Methodology Physics Radiation environment Target information Modeling software H.Tang, SEMM-2: ”A new generation of single-event-effect modeling tools”,IBM Journal of Research and Development V5 No3 2008

23. Adapt to CERN FPGA case CERN Radiation field BEOL FPGA geometry FEOL FPGA geometry Xilinx Qcrit information Dedicated Post-processing H.Tang, SEMM-2: ”A new generation of single-event-effect modeling tools”,IBM Journal of Research and Development V5 No3 2008

24. Thin Si target Alpha Recoil ion Beam Si P,n,d Ongoing work and outlook (I) • Comparison study (Fluka, GEANT4, NUSPA) • Particle production from nuclear reactions

25. Ongoing work and outlook (II) • Comparison study (Fluka, GEANT4, NUSPA) • Konklusjon: Modellene er forskjellige! • Men: Ingen overraskelse

26. Ongoing work and outlook (III) • Comparison study (Fluka, GEANT4, NUSPA) • Preparing simulation case study of FPGA • Compare with experimental results to validate method • Improve simulations of the radiation environment • Add more detailed geometry of electronics rack *Rodbell et al , Low-energy Proton induced Single Event Upsets in 65 nm…, Presented at NSREC July 2007

27. Konklusjon • Eksperimentelt arbeid foreløpig ferdig og aksepttest med tilhørende løsning godkjent • Mye spennende arbeid gjenstår • Tverrfaglig innsats • Strålingsproblematikken er forventent og tilta etter hvert som teknologien nedskaleres *Rodbell et al , Low-energy Proton induced Single Event Upsets in 65 nm…, Presented at NSREC July 2007