1. John D. Cressler, 5/05 1 Radiation Effects in SiGe Technologies John D. Cressler MURI Kickoff: Vanderbilt, Nashville, TN, May 10, 2005 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. John D. Cressler, 5/05 2 21 st Century Communications Market - wireless + wireline + transportation + satellites + radar + other DoD + … frequency bands are pushing ever higher huge market but stringent device requirements Moral: Need High-Performance Device Technology at Low-Cost! The SiGe HBT - first bandgap-engineered Si transistor (nanotechnology!) - better , V A, f T, f max, NF min than Si BJT - III-V performance + Si fabrication yield and cost (win-win scenario!) - 200 GHz SiGe HBTs are a reality! … 300 GHz is on the way! SiGe HBT BiCMOS Technology - very high performance SiGe HBT + best-of-breed Si CMOS - RF/MMIC + analog + digital + passives for integrated SoC / SiP solutions - in production (e.g., IBM, Jazz, National, TI, ST, Infineon, Hitachi, etc…) SiGe: Why The Fuss?  

3. John D. Cressler, 5/05 3 SiGe Strained-Layers The Idea: Practice Bandgap Engineering (i.e., nanotechnology) in the Si Material System! Introduce a small amount of Ge (smaller bandgap) into a Si BJT to … Selectively tailor the transistor for improved performance!

4. John D. Cressler, 5/05 4 Seamless Integration of SiGe into Si When You Do It Right … No Evidence of Deposition! 50 nm

5. John D. Cressler, 5/05 5 Type-I Band Alignment (Valence Band Offset = 74 meV / 10% Ge) Hole Mobility Enhancement (good news) Consequences 100 meV grading across 100 nm = 10 kV/cm electric field! Strained SiGe Si ΔEVΔEV

6. John D. Cressler, 5/05 6 SEM of a SiGe HBT 120 GHz Peak f T Process (IBM) Courtesy of IBM

7. John D. Cressler, 5/05 7 The SiGe HBT The Idea: Put Graded Ge Layer into the Base of a Si BJT Primary Consequences: smaller base bandgap increases electron injection ( β ) field from graded base bandgap decreases base transit time (f T ) base bandgap grading produces higher Early voltage (V A ) III-V HBT Properties + Si Processing Maturity! Bandgap Engineering in Si!

8. John D. Cressler, 5/05 8 Performance Trends Generational Evolution (full SiGe BiCMOS technology) 1 st 2 nd 3 rd 4 th

9. John D. Cressler, 5/05 9 SiGe Fab Facilities Many Industrial SiGe Fab Facilities Worldwide (and growing) > 25!

10. John D. Cressler, 5/05 10 SiGe Millimeter-wave Communications Systems - 60 GHz ISM band (> 1Gb/sec wireless links) - wavelength at mm-wave enables monolithic antennae integration SiGe Radar Systems - defense theater radar (10 GHz) - automotive radar (24 GHz, 77 GHz, 94 GHz) SiGe Core Analog Functions - data converters (10Gb/sec 8 bit ADC!) - references, op-amps, drivers, etc. SiGe Extreme Environment Electronics - cryogenic temperatures (e.g., to 77K or 4K) - radiation (e.g., space) - high-temperatures (e.g., to 200C or 300C) New DoD Opportunities

11. John D. Cressler, 5/05 11 The Holy Grail of the Space Community - IC technology space-qualified without additional hardening - high integration levels to support SoC / SiP (low cost) Radiation Effects SiGe Technology Offers Significant Appeal! Earth protons belts electron belts

12. John D. Cressler, 5/05 12 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 63 MeV protons

13. John D. Cressler, 5/05 13 Observed SEU Sensitivity in SiGe HBT Shift Registers - low LET threshold + high saturated cross-section (bad news!) Common Circuit-level Hardening Schemes Not Effective P. Marshall et al., IEEE TNS, 47, p. 2669, 2000 1.6 Gb/sec Presently… The ‘Achilles Heel’ of SiGe and Space! SiGe 5HP SEU “Issues” Our Goal…

14. John D. Cressler, 5/05 14 Collector-substrate (n + /p - ) Junction Is a Problem (SOI) Lightly Doped Substrate Definitely Doesn’t Help! Very Efficient Charge Collection! The Intuitive Picture

15. John D. Cressler, 5/05 15 diffusion drift Charge Collection Mostly Occurs Through C/Sx Junction Long Diffusion Collection Tail for High LET Hit Collection Depth is Approximately 16um for Vertical Strike Charge Collection DARPA RHBD Program

16. John D. Cressler, 5/05 16 Modeling Challenges MURI Collaboration with Robert Reed IBM SiGe 8HP

17. John D. Cressler, 5/05 17 RAMHARD M/S CSH-M/S New Circuit NAND Reduce Tx-Tx Feedback Coupling Internal to the Latch Circuit Architecture Changes, Layout Changes for RHBD Variable Substrate Bias / Contacting Can Help Need RHBD Techniques RAMHARD M/S CSH-M/S New Circuit NAND DARPA RHBD Program

18. John D. Cressler, 5/05 18 No Local Sx Contact With Local Sx Contact Data / Clock Buffers Output Buffer 8HP RHBD SR Designs DARPA RHBD Program

19. John D. Cressler, 5/05 19 Surface (ionization) vs. Bulk (displacement + ionization) Gamma ∆J B larger than proton ∆J B for inverse-mode Proton vs Gamma 63 MeV Protons

20. John D. Cressler, 5/05 20 Damage Depends on Proton Dose Rate! Forward Mode (EB) Is Not the Same as Inverse Mode (STI) Very Unusual Annealing Effects! Dose Rate Effects?! 63 MeV Protons Damage Spontaneous Annealing Inverse Forward

21. John D. Cressler, 5/05 21 Use DLTS to Probe the Nature of the Traps Can We Meaningfully Perform DLTS Inside a Transistor? Damage Mechanisms 5AM SiGe HBT Tx Chain

22. John D. Cressler, 5/05 22 Can Irradiation Trigger Film Relaxation? How is This Affected by Generational Scaling? Stability Issues

23. John D. Cressler, 5/05 23 Many Fundamental Issues Need Attention - damage mechanisms? (need first principles calculations?) - nature of the traps? (DLTS inside the device?!) - STI vs EB damage mechanism differences? - dose rate issues? - impact on displacement damage on film stability? - improved 3D modeling for SEU understanding? (with R. Reed) - device-to-circuit coupling? (mixed mode – with R. Reed) GT MURI Tasks Leverage Significant SiGe Hardware / Testing Activity - SiGe tapeouts at Georgia Tech (IBM, Jazz, NSC) - DTRA / NASA-GSFC - DARPA RHBD - NASA SiGe Code T Leverage MURI Team Expertise (Exciting!) - R. Reed for modeling / TCAD (use the Vandy Cluster) - theory groups

24. John D. Cressler, 5/05 24 SiGe HBT BiCMOS Technology - bandgap engineering in Si (high speed + low cost + integration) - SiGe ideally suited for RF to mm-wave, analog, and digital circuits - SiGe technology offers many interesting DoD possibilities! Lots to Still Be Learned in SiGe Radiation Effects! Summary SiGe for Radiation-Intense Electronics Is Very Promising - epi-base structure has built-in total-dose hardness (multi-Mrad!) - SEU mitigation approaches currently being pursued BUT …