Silicon-Germanium Technology

1. Silicon-GermaniumTechnology Fernando Gonzalez ECE 217B

2. Contents History Advantages SiGe Generations Physical Properties Si/SiGe Epitaxial-Base Transistors (ETx) DC Characteristics AC Characteristics Reference

3. History IBM�s research to reach fT > 60 GHz back in the early 1980�s. Need to reduce HBT�s base length to enhance computing power. UHV/CVD LTE (1994). Ultra High Vacuum Chemical Vapor Deposition, Low temperature Epitaxy. Silicon Epitaxy was at high temperature HF last-etch step, non wetSilicon Epitaxy was at high temperature HF last-etch step, non wet

4. Advantages of SiGe Low Cost -> Driving force of any technology Integration of Digital and Analog capabilities through BiCMOS on a single chip Higher current gain, excellent noise properties and stable operation over wider temperature ranges BiCMOS maximizes performance and minimize power consumptionBiCMOS maximizes performance and minimize power consumption

5. SiGe Generations First Generation SiGe: .5 um 3.3V On production in 1996, in 1998 the process was qualified Second Generation: .25 um, 2.5V Third Generation: .18 um, 1.8V

7. Physical Properties Pseudomorphic Si1-xGex - Ge has a 4.2% larger lattice constant than Si - Films were grown using Molecular Beam Epitaxy (MBE) - Along with strain, bandgap engineering could be used to produce different structures

9. Physical Properties (Cont.) Possible to design e- and h+ channels with balanced conductances -> high performance heterostructure CMOS Higher mobility allow same speed at � the voltage Defect density is 8 orders of magnitude compared to Si -> yield decreases

10. Physical Properties (Cont.)

11. Si/SiGeEpitaxial-Base Transistors (ETx) Epitaxial Base must be compatible with the existing CMOS tool sets Insure yield for the epi-base Share layers and processes to simplify integration Combine bipolar and CMOS w/o compromising performance due to incompatible thermal budget requirements

12. Yield Enhancement Bipolar Minimum wafer topography Optimization for the wafer pre-clean step CMOS Protection for the gate oxide integrity

13. Yield Enhancement (Cont.)

14. Sharing Layers SiGe-base growth simultaneously produces polysilicon over the poly-protected and any exposed oxide CMOS gate stack is the same as the HBT extrinsic base over field oxide

15. ETx BiCMOS

16. ETx BiCMOS (Cont.)

17. ETx BiCMOS (Cont.)

18. ETx BiCMOS (Cont.)

19. DC Electrical Characteristics High carrier velocity due to the electrical field in the base due to germanium dopants Higher common DC emitter current gain Tradeoff current gain for wider bandwidth by increase base dopants

20. DC Electrical Characteristics

21. DC Electrical Characteristics

22. AC Characteristics Tradeoff bandwidth for a lower power consumption SiGe HBT has lower delay time of, therefore, is more suitable for wide bandwidth application

23. AC Characteristics

24. AC Characteristics

25. AC Characteristics

26. Summary of Characteristics over SiGe Generations

27. References [1] The early history of IBM�s SiGe Mixed Signal Technology David L. Harame and Bernard S. Meyerson IEEE Transactions on Electron Devices, vol. 48, No. 11 Nov 2001 [2] The physics, Materials and Devices of SiGe Technology Douglas Paul, Physics World [3] Current Status and Future Trends of SiGe BiCMOS Technology David L. Harane, David C. Ahlgren IEEE Transactions on Electron Devices, vol. 48, No. 11 Nov 2001 [4] RF applications drive semiconductor process technology choices Frank Della Corte and Brent Wilkins RF Micro Devices, Applied Microwave & Wireless

28. References [5] Si/SiGe Epitaxial-Base Transistors- part II D. L. Harame, J. H. Comfort, J. D. Cressler IEEE Transactions on Electron Devices, Vol. 42, No. 3, March 1995 [6] How SiGe Evolved into a manufactorable semiconductor production Process S. Subbanna, D. ahlgren, D. Harame, B. Meyerson IEEE International Solid-State Circuits Conference, 1999 [7] SiGe & GaAs as Competitive Technologies for RF-Applications Daimler Benz Research Center Ulm FT2/HS. D-89081 Ulm, Germany