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SREC04 Section IV Radiation activities in a project flow : Total Ionizing Dose (TID) effects

SREC04 Section IV Radiation activities in a project flow : Total Ionizing Dose (TID) effects. customer. Radiation expert. customer. Program manager. Program manager. Radiation : why do we care?. Short Course Out line. Introduction Basic concepts

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SREC04 Section IV Radiation activities in a project flow : Total Ionizing Dose (TID) effects

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  1. SREC04 Section IVRadiation activities in a project flow : Total Ionizing Dose (TID) effects SREC04 - June 18, 2004

  2. customer Radiation expert customer Program manager Program manager Radiation : why do we care? SREC04 - June 18, 2004

  3. Short Course Out line • Introduction • Basic concepts • Constraint linked to space radiation environment • Total ionising Dose Level (TDL) calculation • TID degradation mechanisms • Device Total ionising Dose Sensitivity (TDS) determination • TID and Radiation Hardness Assurance (RHA) • Conclusion SREC04 - June 18, 2004

  4. Introduction • Underestimation of radiation induced degradation may endanger any space mission • Among all radiation induced degradations, Total Ionising Dose (TID) has to be considered • TID may degrade electronics and materials performances • TID Radiation Hardness Assurance (RHA) process has to be implemented SREC04 - June 18, 2004

  5. Introduction • RHA consists of all activities undertaken to ensure that the electronics and materials of a space system perform to their design specifications after exposure to the space radiation environment • TID Radiation Hardness Assurance (RHA) process is based on the comparison between • calculated in flight TID level (TDL) and, • TID sensitivity (TDS) of the element under study. • Radiation Hardness Assurance goes beyond the piece part level SREC04 - June 18, 2004

  6. Short Course Out line • Introduction • Basic concepts • Constraint linked to space radiation environment • Total ionising Dose Level (TDL) calculation • TID degradation mechanisms • Device Total ionising Dose Sensitivity (TDS) determination • TID and Radiation Hardness Assurance (RHA) • Conclusion SREC04 - June 18, 2004

  7. Basic concepts • Definition and units • TID is the measure for the quantity of radiation deposited through ionisation mechanism at a specific location, in a specific material • "Standard" unit is the rad(material) regardless that SI unit is the Gray(material) • Rad = Radiation Absorbed Dose • Gray (Gy) = J/ kg (S.I.), 1 Gy = 100 Rad • The dose rate is the amount of TID deposited per unit of time example : rad(Si)/s or rad(Si)/hour SREC04 - June 18, 2004

  8. Short Course Out line • Introduction • Basic concepts • Constraint linked to space radiation environment • Total ionising Dose Level (TDL) calculation • TID degradation mechanisms • Device Total ionising Dose Sensitivity (TDS) determination • TID and Radiation Hardness Assurance (RHA) • Conclusion SREC04 - June 18, 2004

  9. Space radiation environment • Space radiation environment of concern has to be defined in the earliest phase of the program • Particles of concern for TID are protons and electrons • They may transit through the solar system or be trapped by the Earth magnetic field • These create the radiation belts SREC04 - June 18, 2004

  10. Radiation environment : mission related requirements • Different types of space mission in terms of orbit and duration • Major risks not associated to the same constituent of the radiation environment, then, not to the same effect • Required confidence level may vary with the mission type • Identification of the different mission • Launcher : no concern related to TID • Telecommunication • Earth observation / Constellation / Space station • Scientific mission (interplanetary) SREC04 - June 18, 2004

  11. Radiation environment : system related requirements • Different elements of a space system may be radiation sensitive • Electronics • Ionising and Non Ionising Dose (displacement damage), Single Event Effects (SEE) • Materials, optics • Ionising and Non Ionising Dose • Solar generator • mainly Non Ionising Dose • Detectors • Ionising and Non Ionising Dose (displacement damage), Single Event Effects SREC04 - June 18, 2004

  12. Short Course Out line • Introduction • Basic concepts • Constraint linked to space radiation environment • Total ionising Dose Level (TDL) calculation • TID degradation mechanisms • Device Total ionising Dose Sensitivity (TDS) determination • TID and Radiation Hardness Assurance (RHA) • Conclusion SREC04 - June 18, 2004

  13. Total ionising Dose Level (TDL) calculation • Robustness of a device/subsystem/system evidenced thanks to comparison between expectedin flight level (TDL) and TID Sensitivity (TDS) of the concerned device • TDL may be estimated • by Monte Carlo technique (NOVICE, GEANT4…) • Accurate but time consuming • by Ray Tracing technique (NOVICE, SYSTEMA/DOSRAD…) • Less accurate but more "industrial" • Ray tracing technique needs as inputs • spacecraft/equipment/device geometry • TID dose-depth curve SREC04 - June 18, 2004

  14. Total ionising Dose Level (TDL) calculation • Dose-depth curve definition • Should be preferentially usable by any sub-contractor (e.g. compatible with their tools) • Should be adapted to orbit type • Electron rich orbit vs proton rich orbit • Should be provided as a standard for Silicon target with Aluminium shielding shape for electronics • May be provided for particular cases with • Other target/shielding shape materials • Specific thickness range SREC04 - June 18, 2004

  15. Total ionising Dose Level (TDL) calculation SREC04 - June 18, 2004

  16. Total ionising Dose Level (TDL) calculation • Shielding shape used as a standard is a sphere • Solid sphere or shell sphere • Such shielding shape as to be used in conjunction with the adapted ray tracing method • So called NORM or SLANT method SREC04 - June 18, 2004

  17. Total ionising Dose Level (TDL) calculation • Ray tracing vs reverse Monte Carlo calculation ["Comparaison des méthodologies de détermination de dose déposée sur HOTBIRD", T. Carrière, EADS ASTRIUM internal report, 1995.] ["Impact of material properties and shielding structures on dose level calculation", R. Mangeret, CNES funded study, internal ASTRIUM SAS report, 2001.] • Total ionising dose calculation on electronics dies • Inside different packages • For given equipment/satellite geometries • For various radiation environment SREC04 - June 18, 2004

  18. Total ionising Dose Level (TDL) calculation Device package + equipt + satellite GEO orbit, device package + Equipment, satellite is a box SREC04 - June 18, 2004

  19. Total ionising Dose Level (TDL) calculation • No problem for proton rich orbits (LEO, scientific) • Solid sphere to be used for ray tracing • For electron rich orbit (ex : GEO, GALILEO) • comparison with NOVICE Monte carlo calculation • Solid Sphere + SLANT , slight underestimation possible • Shell Sphere + NORM, overestimates generally the total dose level as calculated by MC technique Both give a realistic estimation of received TID • Shell Sphere + SLANT : catastrophic underestimation SREC04 - June 18, 2004

  20. Total ionising Dose Level (TDL) calculation • Impact of the tool on dose-depth curve SREC04 - June 18, 2004

  21. Short course Out line • Introduction • Basic concepts • Constraint linked to space radiation environment • Total ionising Dose Level (TDL) calculation • TID degradation mechanisms • Device Total ionising Dose Sensitivity (TDS) determination • TID and Radiation Hardness Assurance (RHA) • Conclusion SREC04 - June 18, 2004

  22. TID degradation mechanisms • TID effects on electronic devices • TID response on bipolar microcircuits • Main effect at transistor level : reduction of gain (1/)=K.DN with N#1at a low level of dose. • Degradations of PNP transistors are generally more serious (low initial gain), "lateral" PNP being the most critical case. • Integrated circuit degradation may be complex due to interaction between individual transistors degradation (increase of bias & offset currents, increase of offset voltages…) SREC04 - June 18, 2004

  23. TID degradation mechanisms • TID response of bipolar devices • Enhanced Low Dose Rate Sensitivity (ELDRS) • Enhanced degradation at a given TID level when device irradiated at low doserate • Evidenced on bipolar basedintegrated circuit, stronglysuggested for discretetransistors SREC04 - June 18, 2004

  24. TID degradation mechanisms Device type is 2N5551 transistor (STM), single lot SREC04 - June 18, 2004

  25. TID degradation mechanisms • TID response of MOS microcircuits • charges trapped in the oxide (oxide traps) • Charges trapped on the interface (interface traps) • Vth = Vot + Vit • Positive charges: Vth < 0 • Negative charges: Vth > 0 • At transistor level : VGSth drift • At integrated circuit level, increased operating and stand by currents, degradation of input logic level… • Rebound effect to be considered SREC04 - June 18, 2004

  26. TID degradation mechanisms • Dose rate effects in MOS devices • High dose rate generally worst case for MOS devices SREC04 - June 18, 2004

  27. TID degradation mechanisms • TID effects in materials • Organic materials : chemical reactions initiated • Cross-linking, chain scission, formation of gaseous by-products… • Transparent materials (optics) • Darkening (colour centres) • Index of refraction changes • Mechanical and structural changes • For external materials, UV degradation (surface) has to be taken into account SREC04 - June 18, 2004

  28. Short course Out line • Introduction • Basic concepts • Constraint linked to space radiation environment • Total ionising Dose Level (TDL) calculation • TID degradation mechanisms • Device Total ionising Dose Sensitivity (TDS) determination • TID and Radiation Hardness Assurance (RHA) • Conclusion SREC04 - June 18, 2004

  29. Device TID Sensitivity (TDS) determination • TID Device Sensitivity (TDS) is determined thanks to : • Manufacturer guarantee (TID hardened devices) • Technological assessment • TID ground testing • TDS validity is ensured by complying to TID Radiation Hardness Assurance (RHA) rules • Manufacturer guarantee should rely on data set relevant for space application (ELDRS issue) • Technological assessment to be based on degradation mechanisms already presented • TID ground testing should be adapted to space issues SREC04 - June 18, 2004

  30. Device TID Sensitivity (TDS) determination • TID testing issue • Objective is to forecast the behaviour of devices regarding TID flight constraint • In most cases, simulating space radiation environment at ground level is not possible • Testing should mimic or bound the flight usage • TID testing likely to be implemented with 60Co source SREC04 - June 18, 2004

  31. Device TID Sensitivity (TDS) determination • TID testing issue • Existing specifications for electronics are • ESA SCC 22900 issue 2 • MIL STD 883D TM 1019.6 • Both specification are (off course) significantly different • Specification provides with guidelines to insure test conditions reproducibility and test results comparison • Insure test adequacy regarding flight conditions, based on the technical state of the art. • Material TID testing is particularly tough and is in most of the cases performed on case by case bases. SREC04 - June 18, 2004

  32. Device TID Sensitivity (TDS) determination • Two approaches may be used for TDS determination • "worst case" approach : TID level at which the worst case device of the worst case tested lot exceeds its parametric or functional limits • "Statistical" approach : "K factor" / 3-sigma • Then, TDS may corresponds to the first parametric "out of specification" level or to application related Worst Case Analysis (WCA) SREC04 - June 18, 2004

  33. Short course Out line • Introduction • Basic concepts • Constraint linked to space radiation environment • Total ionising Dose Level (TDL) calculation • TID degradation mechanisms • Device Total ionising Dose Sensitivity (TDS) determination • TID and Radiation Hardness Assurance (RHA) • Conclusion SREC04 - June 18, 2004

  34. TID and RHA • RHA methodologies for TID & electronics • Main used method is to categorise devices regarding TID constraint • Radiation Design Margin (RDM) is defined as being the ratio between TDS and TDL • Several empirical methods existsfor RDM determination • Design Margin Breakpoint • Part categorisation Criteria SREC04 - June 18, 2004

  35. TID and RHA • Examples of industrial RHA approaches regarding TID • EADS ASTRIUM : DMBP related approach • A major point is that for RDM value to be valid, both TDL and TDS have to be valid • ALCATEL SPACE : "RADLAT" approach SREC04 - June 18, 2004

  36. TID and RHA • TID mitigation • Some countermeasure may have to be implemented in the course of a space program • Several possibilities exist for TID mitigation • Shielding at device or equipment level • To refine TDL with more accurate calculation (MC) • Equipment / system re-design • Replacement of concerned device by a radiation hardened product • Cold redundancies • … SREC04 - June 18, 2004

  37. Conclusion • From ESA upcoming ECSS-E-10-12 specification • "There is no space system in which radiation effects can be neglected" • TID is one of these radiation effects, then • Degradation mechanisms at sensitive element levelshould be understood • TDL has to be determined with an adequate degree of precision • TDS has to be evaluated in accordance with state of the art radiation knowledge • Risks have to be lowered as much as possible, in conformance with mission requirements, by help of a RHA process SREC04 - June 18, 2004

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