COTS for the LHC radiation environment: the rules of the game

1. COTS for the LHC radiation environment: the rules of the game Federico Faccio CERN Federico Faccio - CERN

2. Outline • Introduction • Summary of radiation effects • Risk management • Dealing with the radiation hazard: fundamental steps • Conclusion Federico Faccio - CERN

3. Why talking about COTS? • COTS = Commercial Off The Shelf • No effort made to improve, assure or even test the radiation tolerance • Poor or no traceability of origin (what REALLY is inside the package??) • Cheaper and better performance, sometimes there is no alternative to their use • The cost of using COTS is higher than the bare part cost: testing and logistic are expensive! Federico Faccio - CERN

4. Total Ionizing Dose (TID) Potentially all components Displacement damage Transient SEEs Bipolar technologies Optocouplers Optical sources Optical detectors (photodiodes) Static SEEs Combinational logic Operational amplifiers SEU, SEFI Digital ICs Summary of radiation effects Permanent SEEs SEL CMOS technologies SEB Power MOSFETs, BJT and diodes SEGR Cumulative effects Power MOSFETs Single Event Effects (SEE) Federico Faccio - CERN

5. Risk Management Use of COTS => risk avoidance Mission: LHC and experiments running Which failure tolerable? How often? = Where? f (system) Risk management at system level (top-down) Do we have enough experience and competence in the same organizational unit? (learning process is time and resources consuming!) Federico Faccio - CERN

6. Dealing with the radiation hazard Get a good knowledge of the environment Define the requirements for the components Understand the effects Identify the candidate components Test the candidate components Engineer the system Federico Faccio - CERN

7. TID Total Dose [krad, Gy] 1 MeV equivalent neutron fluence (n/cm2) Displacement damage Fluence and energy distribution of main particles (p/cm2) SEEs or at least   (E,all hadrons)dE 20MeV The radiation environment Knowledge in “meaningful” terms: Get the most precise estimate of the environment Taylor the safety factor Safety factor = cost Federico Faccio - CERN

8. Effects of the environment • CMOS technologies • Memories (SRAM, DRAM, Flash, EEPROM) • FPGAs • Microprocessors and DSPs • Bipolar technologies • Power devices • Optocouplers Federico Faccio - CERN

9. Displacement damage TID Sensitive with dose rate effects Variable failure levels SEL Not very likely in LHC A few known sensitive components: K5 mp from AMD, SRAMs, ADCs, DSPs, FPGAs CMOS technologies (1) SEGR, SB Very unlikely Federico Faccio - CERN

10. CMOS technologies (2) SEU: memories SRAMs Sensitive with low threshold Sometimes MBU Stuck bits only with high LET DRAMs Sensitive with low threshold Situation improved with decreased cell area and better signal over noise sp comparable to SRAMs SEFI possible (low s) Flash Memories Errors in the complex control circuitry with different consequences Higher threshold than SRAMs-DRAMs Much lower sp (100-1000 times) EEPROMs Write mode more sensitive than read Higher threshold than SRAMs-DRAMs SEFI possible Federico Faccio - CERN

11. CMOS technologies (3) SEU: FPGAs SRAM-based Loss of configuration: consequences? Low threshold: likely in LHC Requires reprogramming Antifuse-based ONO antifuses sensitive to destructive event with high threshold A-Si antifuses more robust • FF and combinatorial logic gates: • Sensitive in both technologies (FF implementation with  sensitivity) • TMR can be integrated in antifuse-based • In new Virtex series, TMR can be safely integrated • SEFI: • Can happen in both technologies (SEU in JTAG circuitry) with low s • Solutions proposed by both Actel and Xilinx • Radiation tolerant products available (on epi substrate) • Variability in radiation performance (esp. TID and SEL) • Documented mitigation techniques exist for both Actel and Xilinx Federico Faccio - CERN

12. CMOS technologies (4) SEU: microprocessors and DSPs • SEU effects strongly application-dependent • Testing has to be performed running a representative program • SEU consequences: very variable (no effect, calculation error, code stopped, …) • Most devices are sensitive in a proton environment, hence in LHC Federico Faccio - CERN

13. TID Leakage paths and b degradation Sensitive with dose rate effects (ELDR) Variable failure levels SET At the output of comparators Rail-to-rail signal SEL Displacement damage b degradation PNP are affected from 3•1011 p/cm2 (50MeV) NPN are affected from 3•1012 p/cm2 (50MeV) Voltage regulators, comparators, op amps Bipolar technologies Simultaneous effects: they add up Federico Faccio - CERN

14. Power devices • Sensitive to TID and displacement damage • Power MOSFETs, bipolar and diodes SEB • Sensitive in hadron environment (also 14MeV n) • De-rating often required (of variable %) • P-channel MOSFETs are much less sensitive • Power MOSFETs and IGBTs SEGR • Very rare in an hadron environment • Dependent on Vgs (sensitive for Vgs < -20V) • Dependent on gate oxide thickness • Most data refer to HI: de-rate as indicated for experiments run with LET of 26 MeVcm2mg-1 Federico Faccio - CERN

15. Optocouplers • Sensitive to TID and displacement damage • CTR decreases after 1-5•1010 p/cm2 (4N49 Micropac and Optek, P2824 Hamamatsu) • Degradation of LED and ptotodetector • Other devices, with different LED and coupling LED/phototransistor, have good resistance (6N140, 6N134, 6N139 from HP) • Sensitive to SET • Sensitivity increases with speed • Sensitive to direct ionization from p+ (angular effect) • Might induce transient out dropout in DC-DC conv. Federico Faccio - CERN

16. The radiation requirements(theory) Know the system where the component operates (top-down) Cumulative effects: Simulation Test procedures COTS variability Estimated level • SF Destructive SEEs: No destructive SEE Transients and SEU Acceptable rate for the system Federico Faccio - CERN

17. Simulation accurate Test procedures correct COTS variability systematic Taylor the SF Cumulative effects: Which SF???? The radiation requirements (headaches) Destructive SEEs: Example Envir. = 1011 h/cm2 1000 components s = 10-11 cm2? Which limit on cross-section? Which limit on HI LETth? Transients and SEU Estimate the error rate in the real environment Evaluate the system-level impact of each error Federico Faccio - CERN

18. The candidate components • Search for radiation data • Databases on web (often obsolete): JPL compendia, GSFC, DTRA, SPUR, …. • NSREC “Workshop records” • December issue of Trans. Nucl. Science • ESA/ESTEC final presentation day (soon database?) • For FPGA, look in the manufacturer’s home page for fresh data • How to interpret SEE data? • Rough guidelines based on “Computational method to estimate SEU rates in an accelerator environment” (NIM, August 00) Federico Faccio - CERN

19. How to interpret SEE data (1) You have data for mono-energetic p or n beams (60-200MeV)! SEErate = sp/n • flux (all hadrons above 20MeV) Example Xilinx XC4010XL: s100MeV n = 4.4•10-15 cm2/bit Estimated flux = 2•103 cm-2s-1 (=1011 cm-2) => SEErate = 8.8•10-12 errors/(bit s) Each chip contains about 283k configuration bits => SEErate chip = 2.5•10-6 s-1 For each 110 FPGA, one looses its configuration each hour! Federico Faccio - CERN

20. Probability curves from the simulation of the environment Weibull curve 1 ) 2 2 3 cross section (cm 40 60 80 Deposited energy 0 20 100 120 How to interpret SEE data (2) You only have Heavy Ion data... … but you have the Weibull fit parameters! Federico Faccio - CERN

21. How to interpret SEE data (3) You only have Heavy Ion data... … and you do not have the Weibull fit parameters... You can just have a feeling: • LETth < 5 MeVcm2mg-1 => quite sensitive • LETth > 15 MeVcm2mg-1 => not sensitive Federico Faccio - CERN

22. Testing the candidate parts • Never use data from a database as a source for qualification, only to identify candidate parts! • Radiation source • Irradiation procedure • Board-level testing and hybrid devices Federico Faccio - CERN

23. Radiation source 60Co TID Low energy neutrons (nuclear reactor) Displacement damage SEEs Mono-energetic hadron beams (60-200 MeV p) With 60 MeV: - rare SEU under-estimate - Is the energy enough for SEB/SEGR? Global test plan (CMS: HCAL, Muons, Cavern) What about thermal neutrons? (they have not been taken into account for the experiments) Federico Faccio - CERN

24. Preferential access conditions for high-E proton beams Preferential agreement with 2 facilities established since several years through the RD49/COTS project : • CRC (Cyclotron Research Centre) in UCL, Louvain-la-Neuve (Be) • > protons (60MeV), Heavy Ions, neutrons (low intensity) • - PSI (Paul Scherrer Institute) in Villigen (Ch) • > protons (250MeV) Federico Faccio - CERN

25. Irradiation procedure (1) Prompt + Latent charge buildup Irradiation + Annealing Test methods give worst case picture CMOS TID ELDR effect JPL advice: Bipolar TIDspec < 30krad 50 & 0.005 rad/s test at room T compare if failure in any condition (@TID<1.5TIDspec) => do not use! TIDspec > 30krad test up to 30krad in 3 conditions: 50 & 0.005 rad/s at room T, 1rad/s at 90oC compare if comparable => use 90oC test BUT take an additional SF = 2 on TIDspec Federico Faccio - CERN

26. s E (MeV) sSEB Vds rated Vds Irradiation procedure (2) Displacement damage - room T, all grounded - measurement of s - representative conditions - needs a dedicated setup - careful to SEFI - with h-beams => in air and packaged SEU, SET - measurement of s - protect the component! - needs a dedicated setup - for SEB & SEGR look for derating conditions SEL, SEB, SEGR Federico Faccio - CERN

27. Board-level testing & hybrids • Board-level testing • Less infos on actual safety margins • It can be difficult to trace back the origin of problems • Use for go/no go tests only! • Can give useful infos on system response (esp. SEU) • Hybrid devices • Difficult to know what is in the hybrid (proprietary designs, no infos from the manufacturer) • Examples on DC-DC power converters (JPL, NASA) Federico Faccio - CERN

28. Qualify the components to be used Is there an alternative component? Is the tolerance sufficient? Use the components Qualification OK? Reduce requirements: - refine the environment knowledge - use mitigation techniques (for SEU) - foresee replacement if possible - modify the system Engineer the system Test the candidate components Yes No No Yes Yes No Federico Faccio - CERN

29. Summary • Radiation effects • Risk management • risk avoidance impossible with COTS! • more efficiently applied at system level! • Steps to deal with the radiation hazard • know the environment • understand the effects • define the requirements • identify the candidate components • test • engineer the system Federico Faccio - CERN

30. Conclusion Main rule of the game: System Environment Radiation hazard To merge knowledge on Big challenge for all LHC teams! Federico Faccio - CERN

31. Reference material • This presentation, made at the 6th Workshop on Electronics for the LHC Experiments (Cracow, September 2000), has been followed by a full paper with an extensive set of references (79 papers). The paper can be found as: • - F.Faccio, “COTS for the LHC radiation environment: the rules of the game”, proceedings of the 6th Workshop on Electronics for the LHC Experiments, CERN 2000-010, CERN/LHCC/2000-041, 25 October 2000, page 50 Federico Faccio - CERN