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Radiation Effects in SiGe Devices

Radiation Effects in SiGe Devices Bongim Jun, Gnana Prakash, Akil Sutton, Marco Bellini, Ram Krithivasan, and John D. Cressler MURI Review: Vanderbilt University, Nashville, TN June 13, 2006. School of Electrical and Computer Engineering

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Radiation Effects in SiGe Devices

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  1. Radiation Effects in SiGe Devices Bongim Jun, Gnana Prakash, Akil Sutton, Marco Bellini, Ram Krithivasan, and John D. Cressler MURI Review: Vanderbilt University, Nashville, TN June 13, 2006 School of Electrical and Computer Engineering 777 Atlantic Drive, N.W., Georgia Institute of Technology Atlanta, GA 30332-0250 USA cressler@ece.gatech.edu Tel (404) 894-5161 / http://users.ece.gatech.edu/~cressler/

  2. The SiGe Success Story • RapidGenerational Evolution (full SiGe BiCMOS) • Making Significant In-roads in High-speed Communications ICs • Many DoD-Relevant Opportunities - very high performance SiGe HBT + best-of-breed Si CMOS - RF to mm-wave + analog + digital + passives for integrated SoC / SiP 4th 3rd 2nd 1st

  3. Half-TeraHertz SiGe HBT! • 510 GHz peak fT at 4.5K! • World’s First Half-TeraHertz Si-based Transistor • Lot’s of Steam Left for SiGe HBT Scaling … To appear in IEEE Electron Device Letters, July 2006

  4. Applications Defense Navigation Automotive Communications

  5. SiGe mm-wave SoC • Wireless 60 GHz (ISM band) Data Links (1.0 Gb/sec!) DARPA Funded Courtesy of Ullrich Pfeiffer ofIBM

  6. SiGe Radar Systems Single Chip X-band SiGe T/R (4x4 mm2) MDA Funded Begs For SiGe! Potential Paradigm Shifting Impact for Phased Array Radar!

  7. Extreme Environments • Cryogenic Temperatures (e.g., 77K = -196C) • High Temperatures (e.g., 200C) • Radiation (e.g., Earth orbit) Cars Drilling Moon / Mars CEV Aerospace

  8. Total-Dose Response • Multi-Mrad Total Dose Hardness (with no intentional hardening!) • Radiation Hardness Due to Epitaxial Base Structure (not Ge) - thin emitter-base spacer + heavily doped extrinsic base + very thin base 4th 3rd 200 GHz SiGe HBT 2nd 1st 63 MeV protons @ 5x1013 p/cm2 = 6.7 Mrad TID!

  9. Single Event Effects • • Observed SEU Sensitivity in SiGe HBT Shift Registers • - low LET threshold + high saturated cross-section (bad news!) 50 GHz SiGe HBTs Goal… The ‘Achilles Heel’ of SiGe and Space! 1.6 Gb/sec P. Marshall et al., IEEE TNS, 47, p. 2669, 2000

  10. The Intuitive Picture • Collector-substrate (n+/p-) Junction Is a Problem (SOI solves this) • Lightly Doped Substrate Definitely Doesn’t Help! Heavy Ion (GeV cosmic ray) Very Efficient Charge Collection!

  11. 3-D TCAD Modeling Collaboration with R. Reed ofVanderbilt Univ. and G. Niu of Auburn Univ.

  12. Most Charge Collection Occurs Through C/Sx Junction Long Collection Times for High LET Ion Strikes (nsec!) Deep Collection Depth (16μm!) TCAD Charge Dynamics Drift Diffusion Collaboration with R. Reed of Vanderbilt and Guofu Niu of Auburn Univ.

  13. TCAD to Circuits 5HP 8HP Standard Master Slave OUT DATA CLOCK UPSETS “Hit” RamHard RHBD OUT DATA CLOCK • 3D Simulation I(t), Deep Strike, LET=10, Vsx= -4V (4 GB/s)

  14. SEU Tolerant Latches • Reduce Tx-Tx Feedback Coupling Internal to the Latch • Circuit Architecture Changes + Transistor Layout Changes Dual-Interleaved Limiting Cross-section (no errors!) First Successful Hardening of SiGe! Leverage: DARPA RHBD Program DTRA / NEPP

  15. Outline • • Some Reminders • New Total Dose Effects in Bulk SiGe HBTs • New Cryogenic Irradiation Results • New Results on SiGe HBTs on Thin-Film SOI • A First Look at SiGe MODFETs • Progress / Plans

  16. Source / Rate Effects • EB spacer  SiO2/Si3N4 composite stack • Variation in ∆JB damage with dose rate for different sources not large • Dose enhancement effects apparently observed for x-ray damage • photon interaction with Cu/W metallization  enhanced x-ray damage? • results qualitatively agree with Geant-4 MRED simulations on SRAMs x-ray dose enhancement Cu/W studs above EB spacer Collaboration with MURI Vanderbilt Team Leverage: DTRA / NEPP

  17. Source / Rate Effects • STI oxide  thermal CVD (different interface to EB spacer) • Increase in inverse mode ∆JB with dose rate (60Co and x-ray) • electron-hole pairs escape recombination  increased charge yield • secondary electrons generated with low stopping power  increased damage E B C

  18. Reliability Issues • Preliminary study of possible reliability stress path dependence • Mixed-mode stress (high VCB + high JE) prior to proton irradiation • 63 MeV protons / 3000 sec mixed-mode stress (JE=40mA/µm2, VCB=3V) • No change observed in post-radiation response after 3000 s of stress

  19. Reliability Issues • 1Mrad(SiO2) prior to 3000 sec mixed-mode stress • Forward and inverse mode ∆JB independent of pre-stress condition • More work needed • increase stress time beyond 3000 sec & vary current density during stress • explore reverse EB stress response

  20. Outline • • Some Reminders • New Total Dose Effects in Bulk SiGe HBTs • New Cryogenic Irradiation Results • New Results on SiGe HBTs on Thin-Film SOI • A First Look at SiGe MODFETs • Progress / Plans

  21. The Moon (Classic Extreme Environment!) Rover / Robotics Temperature: • +120C to -180C • 28 day cycles • -230C in shadowed polar craters Radiation: • 10’s of krad (modest) • single event upset (SEU) • solar events Many Different Circuits: • digital / analog library • ADC / DAC • RF • power • control functions • sensor interfaces Get Rid of the Centralized “Warm Box” Large GT-led NASA Funded Effort (RHESE) Targeting RLEP-2

  22. Cryo-T Irradiation • Less Degradation For Devices Irradiated at 77K Compared to at 300K • Damage is Produced Even in the Absence of Significant Thermal Energy Leverage: DTRA / NEPP 63 MeV protons

  23. Cryo-T Irradiation • 300K Irradiation + 77K Measurement vs. 77K Irradiation + 300K Meas. • 300K Irradiation Appears to Produce More Damage Than 77K Irradiation • Interesting Physics AND Bodes Well Lunar Apps of SiGe

  24. Cryo-T Irradiation • Answer Appears to Depend on the Technology Node! • In 200 GHz 8HP Devices, Forward-Mode IB is Larger for 77K Irradiation • We Will Focus Some More Attention Here

  25. Outline • • Some Reminders • New Total Dose Effects in Bulk SiGe HBTs • New Cryogenic Irradiation Results • New Results on SiGe HBTs on Thin-Film SOI • A First Look at SiGe MODFETs • Progress / Plans

  26. Intuitive Picture for SEU • Collector-substrate (n+/p-) Junction Is a Problem • Low Resistivity Substrate (8-10 ohm-cm) Definitely Hurts! SOI J. Pellish et al., NSREC 06 Leverage: DTRA / NEPP NAVSEA Very efficient charge collection (to 16 um!) An “obvious” solution – move to SOI!

  27. Device Technology • IBM Research Collaboration (J. Cai) • TSi = 120 nm / TBOX = 140 nm(compatible with 130 nm SOI CMOS) • Substrate Can Be Used as an Active 4th Terminal • True 2-D Device(fundamentally different from conventional SiGe HBT) VSUB

  28. X-ray Irradiation • IB Leakage Increases at Low VBE(EB spacer damage) • IB Decreases at High VBE (RC effect) Collaboration with MURI Vanderbilt Team

  29. X-ray Irradiation • Partially Depleted Devices Irradiated for the First Time • Larger Excess Current with Respect to 63 MeV Protons Fully Depleted Partially Depleted

  30. Outline • • Some Reminders • New Total Dose Effects in Bulk SiGe HBTs • New Cryogenic Irradiation Results • New Results on SiGe HBTs on Thin-Film SOI • A First Look at SiGe MODFETs • Progress / Plans

  31. SiGe MODFETs Collaboration with S. Koester at IBM

  32. SiGe n-MODFETs Collaboration with S. Koester at IBM

  33. nMODFET Irradiation • Peak gm and peak fT decrease with Radiation • Impact of Displacement Damage on Transport? Leverage: DTRA / NEPP 63 MeV protons

  34. Georgia Tech Focus • Many Fundamental Issues in SiGe Need Attention • - improve our understanding of basic damage mechanisms (TID + SEU) • - understand observed dose enhancement / source dependent effects • - understand the effects of operating temperature on damage mechanisms • - explore other SiGe HBT variants (e.g., SiGe HBT on SOI, C-SiGe) • - explore other (new) SiGe-based devices (e.g., SiGe MODFETs) • - improve 3D modeling and understanding for SEU (with R. Reed) • - explore metalization / overlayer effects (GEANT4 – with R. Reed) • - explore device-to-circuit coupling (mixed-mode TCAD – with R. Reed) • Leverage of Significant SiGe Hardware / Testing Activity • - many SiGe tapeouts at Georgia Tech (IBM, Jazz, etc.): devices + circuits • - DTRA / NASA-GSFC (NEPP) • - DARPA RHBD Program • - NASA SiGe ETDP RHESE Program (Lunar apps)

  35. Progress / Plans • Dose Enhancement Effects / Source Dependence in SiGe HBTs - push deeper into the mechanisms: more data + TCAD + GEANT4, etc. • Explore the Role of Temperature in Damage Physics - push deeper into the mechanisms: more data + TCAD, etc. • Continue to Push More Deeply into New Types of SiGe Devices - SiGe MODFET; SiGe HBT on SOI; complementary SiGe (npn vs pnp) • Publications [1] A.K. Sutton, A.P.G. Prakash, R.M. Diestelhorst, G. Espinel, B. Jun, M. Carts, A. Phan, J.D. Cressler, P.W. Marshall, C.J. Marshall, R.A. Reed, R.D. Schrimpf, and D.M. Fleetwood, “An Investigation of Dose Enhancement and Source Dependent Effects in 200 GHz SiGe HBTs,” IEEE Nuclear and Space Radiation Effects Conference, July 2006. [2] G. Prakash, R. Diestelhorst, G. Espinel, A. Sutton, B. Jun, C. Marshall, P. Marshall, and J.D. Cressler, “The Effects of 63 MeV Proton Irradiation on SiGe HBTs Operating at Liquid Nitrogen Temperature,” Proceedings of the Seventh IEEE European Workshop on Low-Temperature Electronics, June 2006. [3] M. Bellini, B. Jun, T. Chen, J.D. Cressler, P.W. Marshall, D. Chen, and J. Cai, “Radiation and Bias Effects in Fully-Depleted and Partially-Depleted SiGe HBTs Fabricated on CMOS-Compatible SOI,” 2006 IEEE Nuclear and Space Radiation Effects Conference, July 2006. [4] A.P.G. Prakash, A.K. Sutton, R. Diestelhorst, G. Espinel, J. Andrews, B. Jun, J.D. Cressler, P.W. Marshall, and C.J. Marshall, “The Effects of Irradiation Temperature on the Proton Response of SiGe HBTs,” 2006 IEEE Nuclear and Space Radiation Effects Conference, July 2006.

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