Si-Based RF & Microwave device

SiGe HBT Technology Si-Based RF & Microwave device 2004-21454 김 경 운 RF & Millimeter-wave Integrated Systems Lab.

Si vs III-V material • Competitive III-V technology. • Processing maturity • Integration level • Yield • Cost • Recent work • passive & transmission lines on Si Si-based MMIC’s possible

Why Si? • High quality dielectric(SiO2) grown on Si • Used for isolation, passivation, active layer (e.g gate oxide) • Grown in very large, defect free single crystals • Excellent thermal properties • Controllably doped n- & p-type impurities • High dynamic range(1014~1022 cm-3) • Facilitating ease of handling & fabrication • Easy to make low resistance ohmic contact

Ge content in SiGe • Stability diagram • Effective film thickness as func of effective film strain( Ge content) • ‘metastable’ generating device-killing defects in the process metastable Thermodynamically stable SiGe films remain stable after processing SiGe film must be very thin

History of SiGe technology Commercial Production on 200mm wafer SiGe BiCMOS tech. Various technology have been Demonstrated using variety epitaxial growth technologies fT=75GHz HBT LSI ckt (DAC) 1993 1990 1992 1994 1994~

III. The SiGe HBT • DC characteristics • Frequency response • Low-freq and broad-band noise • Reliability • Temperature effect

1.DC characteristics • Graded –base(Ge) • Dependence Ge produces an electric-field Transport of carrier Improve freq response • Collector current-density(Jc) • Reduce barrier at EB junction • More charge transfer • Increase current gain Ratio of the DOS between SiGe & Si Difference between the electron & hole mobilities in the base

1.DC characteristics(cont’) • Graded Ge • Enhancement in output conductance • Physically base profile toward the CB side of the neutral base Effectively harder to deplete for a given bias than Si-BJT Current gain – Early voltage product

2. Frequency response • Built in field effectively decreases base transit time • Emitter transit time also decreases.

3. Low-freq and broad-band noise • 1/f noise • Limit on the system: phase noise in mixer & oscillator • Comparable to Si-BJT • Superior to III-V HBT or FET

3. Low-freq and broad-band noise(cont’) Low power ,low noise application

4. Reliability • DC lifetime test • 0.8x12um2 0.8x25um2 No degradation!!!

4. Reliability(cont’) • R.B at EB-junction • Open collector stress • 4V up to 10min • Ic not change • Ib change DC current gain decrease!!

4. Reliability(cont’)

4. Reliability(cont’) S21 S11,S12,S22 practically no change S21 mainly variation!!! if Ic is const S21 variation minimize!!!

5. Temperature effect • Cryogenic environment Current gain:500 fT=60GHz fmax=50GHz

5. Temperature effect(cont’) • Ge misplacement • Reduce the collector current & cutoff freq • Due to parasitic energy barriers • fT degradation • Caused by the reduction of the collector current Pileup of minority carrier in the base

5. Temperature effect(cont’) • Ge ramp-effect Eg,Ge(0): bandgap reduction due to Ge at EB depletion edge @ bias VBE temp T Eg,Ge(grade): grading across the quasi-neutral base Ic Vbe space charge width reducing Ge at boundary Produce bias & Temp dependence

5. Temperature effect(cont’) • neutral base recombination • IB: hole current, impact ionization current, NBR • Small VCB : impact ionization current negligible • Effective electron diff length is comparable to neutral base width • Reduction electron lifetime due to the presence of traps in base • High injection barrier effect

IV. Technology Issues • Growth & film stability • Passive and transmission lines on Si • SiGe BiCMOS for system on chip

1. Growth & film stability • Several keys • film uniformity and control for both doping, Ge content, film thickness, Ge profile shape. • Film contaminants must be miniscule : excellent interface quality • Growth conditions allow abrupt doping transitions with large dynamic range • Ge content • 8~12% base width 80~100nm • 16~24% base width 40~50nm • Limit base transit time

2. Passive and transmission lines on Si • Passive element • Precision resistor • Made from heavily doped polysilicon on oxide • MIM Cap • high Q factor & precision • Inductor • high Q & high inductance

2. Passive and transmission lines on Si • Transmission lines • Low loss lines required ZL=50ohm @ 24GHz |S21|=0.7dB

3. SiGe BiCMOS for system on chip • System-on-chip ? • Cost ? decrease size, improve performance, reliability, reduce cost!!! • But In the RF world • Important signal isolation

V. Status & future • Past • Target freq : 900MHz~2GHz • Present • Various freq. band • C-band(4~8GHz) • X-band(8~12.5GHz) • Ku-band(12.5~18GHz) • K-band(18~26.5GHz) • V-band(50~75GHz) Very rapidly Increasing!!!

V. Status & future(cont’) LNA PA

V. Status & future(cont’) • Johnson limit • fT•BVCEO product • Tradeoff between fT & BVCEO • How high will fT go? • In the region of Fmax • Reduced parasitic component

Conclusion • Motivation for SiGe tech. • Competitive III-V tech • Technology has been rapidly developed. • Good performance • RF system-on-chip solution : BiCMOS tech. Future for SiGe appears bright!!!

References [1]J.W.Slotboom, G.Streutker, A.Pruijmboom, and D.J.Gravesteijin, “Parasitic energy barriers in SiGe HBT’s”,IEEE Electron Device Lett,Vol12 pp 486-488 sept.1991 [2] Burghartz, J.N.; Soyuer, M.; Jenkins, K.A.; Kies, M.; Dolan, M.; Stein, K.J.; Malinowski, J.; Harame, D.L.; “Integrated RF components in a SiGe bipolar technology”Solid-State Circuits, IEEE Journal of , Volume: 32 , Issue: 9 , Sept. 1997 Pages:1440 - 1445 [3] Larson, L.; Case, M.; Rosenbaum, S.; Rensch, D.; Macdonald, P.; Matloubian, M.; Chen, M.; Harame, D.; Malinowski, J.; Meyerson, B.; Gilbert, M.; Maas, S.;“Si/SiGe HBT technology for low-cost monolithic microwave integrated circuits”Solid-State Circuits Conference, 1996. Digest of Technical Papers. 43rd ISSCC., 1996 IEEE International , 8-10 Feb. 1996 [4] Crabbe, E.F.; Cressler, J.D.; Patton, G.L.; Stork, J.M.; Comfort, J.H.; Sun, J.Y.-C.; “Current gain rolloff in graded-base SiGe heterojunction bipolar transistors”Electron Device Letters, IEEE , Volume: 14 , Issue: 4 , April 1993 [5] Salmon, S.L.; Cressler, J.D.; Jaeger, R.C.; Harame, D.L.;“The impact of Ge profile shape on the operation of SiGe HBT precision voltage references”Bipolar/BiCMOS Circuits and Technology Meeting, 1997. Proceedings of the , 28-30 Sept. 1997

References [6] Schumacher, H.; Erben, U.; Gruhle, A.; “Low-noise performance of SiGe heterojunction bipolar transistors” Microwave Symposium Digest, 1994., IEEE MTT-S International , 23-27 May 1994 Pages:1167 - 1170 vol.2 [7] Joseph, A.J.; Cressler, J.D.; Richey, D.M.; Jaeger, R.C.; Harame, D.L.;“Neutral base recombination and its influence on the temperature dependence of Early voltage and current gain-Early voltage product in UHV/CVD SiGe heterojunction bipolar transistors” Electron Devices, IEEE Transactions on , Volume: 44 , Issue: 3 , March 1997 Pages:404 - 413 [8] Burghartz, J.N.; Soyuer, M.; Jenkins, K.A.; Kies, M.; Dolan, M.; Stein, K.J.; Malinowski, J.; Harame, D.L.; “Integrated RF components in a SiGe bipolar technology” Solid-State Circuits, IEEE Journal of , Volume: 32 , Issue: 9 , Sept. 1997 Pages:1440 – 1445 [9] Larson, L.; Case, M.; Rosenbaum, S.; Rensch, D.; Macdonald, P.; Matloubian, M.; Chen, M.; Harame, D.; Malinowski, J.; Meyerson, B.; Gilbert, M.; Maas, S.; “Si/SiGe HBT technology for low-cost monolithic microwave integrated circuits”Solid-State Circuits Conference, 1996. Digest of Technical Papers. 43rd ISSCC., 1996 IEEE International , 8-10 Feb. 1996 Pages:80 - 81, 422 [10] Joseph, A.J.; Cressler, J.D.; Jaeger, R.C.; Richey, D.M.; Harame, D.L.; “Neutral base recombination in advanced SiGe HBTs and its impact on the temperature characteristics of precision analog circuits”Electron Devices Meeting, 1995., International , 10-13 Dec. 1995 Pages:755 - 758

References [11] Cressler, J.D.; Crabbe, E.F.; Comfort, J.H.; Sun, J.Y.-C.; Stork, J.M.C.;“An epitaxial emitter-cap SiGe-base bipolar technology optimized for liquid-nitrogen temperature operation”Electron Device Letters, IEEE , Volume: 15 , Issue: 11 , Nov. 1994 Pages:472 – 474 [12] Cressler, J.D.; “SiGe HBT technology: a new contender for Si-based RF and microwave circuit applications” Microwave Theory and Techniques, IEEE Transactions on , Volume: 46 , Issue: 5 , May 1998 Pages:572 – 589 [13] Kuchenbecker, J.; Borgarino, M.; Bary, L.; Cibiel, G.; Llopis, O.; Tartarin, J.G.; Graffeuil, J.; Kovacic, S.; Roux, J.L.; Plana, R.; “Reliability investigation in SiGe HBT's” Silicon Monolithic Integrated Circuits in RF Systems, 2001. Digest of Papers. 2001 Topical Meeting on , 12-14 Sept. 2001 Pages:131 - 134

Si-Based RF & Microwave device