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The Nanofab Group

The Nanofab Group. EE 4345 – Semiconductor Electronics Design Project – Spring 2002 Kevin Bradford Corey Clark Carlos Garcia Guillaume Gbetibouo Eric Goebel Fariba Pouya. Technical Project 1.5. ANALOG BiCMOS. Introduction. What is BiCMOS?

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The Nanofab Group

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  1. The Nanofab Group EE 4345 – Semiconductor Electronics Design Project – Spring 2002 Kevin Bradford Corey Clark Carlos Garcia Guillaume Gbetibouo Eric Goebel Fariba Pouya

  2. Technical Project 1.5 ANALOG BiCMOS

  3. Introduction What is BiCMOS? BiCMOS technology combines Bipolar and CMOS transistors onto a single integrated circuit where the advantages of both can be utilized.

  4. Advantages of CMOS over Bipolar • Power dissipation • Noise margin • Packing density • The ability to integrate large comples functions with high yields

  5. Advantages of Bipolar over CMOS • Switching speed • Currents drive per unit area • Noise perfomance • Analog capability • Input/output speed

  6. Advantages of BiCMOS Technology • Improved speed over CMOS • Lower power dissipation than Bipolar • Flexible input/outputs • High performance analog • Latch up immunity

  7. Higher performance analog circuits Reduced design efforts Faster design cycles Higher wafer cost Longer manufacturing time Lower process yields Analog BiCMOS Complexity Analog BiCMOS processes are characterized by their complexity, most needing15 masks. Some up to 30 masks. Advantages of complexity Disadvantages of complexity

  8. Evolution of BiCMOS from CMOS BiCMOS technologies have tended to evolve from CMOS processes in order to obtain the highest CMOS performance possible. The bipolar processing steps have been added to the core CMOS flow to realize the desired device characteristics.

  9. Fabrication Equipment Molecular Beam Epitaxy (MBE)

  10. Fabrication Equipment Photoresist Spinner Bake-out Ovens

  11. Fabrication Equipment Mask Aligner Reactive Ion Etching (RIE)

  12. Fabrication Equipment Chemical Vapor Deposition (CVD) Plasma Quest Sputter

  13. Fabrication Equipment Plasma Sputter Perkin-Elmer MBE

  14. Fabrication Equipment Probe Station Scanning Electron Microscope (SEM)

  15. N-well CMOS Structure • NMOS device, built in a 15um thick P-epitaxial layer on top of P+substrate • PMOS transistor, built in an implanted N-well approximately 5um deep • P+ substrate is used to reduce latch up susceptibility by providing a low impedance patch through a vertical PNP device • Polysilicon gates are used for both the PMOS and NMOS transistors

  16. Adding NPN Bipolar Transistor • The simplest way to add an NPN bipolar transistor to the previous CMOS structure is by using PMOS N-well as the collector of the Bipolar device and introducing an additional mask level for the P-base region. • the P-base is approx 1 um deep with a doping level of about 1e17 atoms/cm^3 • the N+ source/drain ion implantation step is used for the emitter and collector contact of the bipolar structure • the P+ source/drain ion implantation step is used to create a P+ base contact to minimize the base series resistance

  17. Contacts

  18. Contacts metal n-type s/c qcs qfm qVbi qfs,n qfBn Ec EFm EFn EFi Depl reg Ev qf’n

  19. Pattern Shift – NBL Shadow (1/2)

  20. Pattern Shift – NBL Shadow (2/2) • Stacking faults • An extra plane of atoms • The lack of a plane of atoms • Other Causes • Temprature • Pressure • Wafer pre-leaning • Growth precursor

  21. P Isolation vs. CDI Collector Diffused Isolation P Isolation

  22. BiCMOS Isolation Consideration • Key factor in determining overall circuit performance and density • Collector Diffused Isolation (CDI) • N-well used to form collector of NPN transistor • Base and emitter consist of successive counterdoping of the well. • CDI transistors • Saturate prematurely • Limits low-voltage operation • Complicates device modeling • Causes undesired substrate injection

  23. Applications of BiCMOS Technology • System-on-a-Chip Technology • personal Internet access devices • set-top boxes • thin clients

  24. References • Carter, Ronald. “Lecture 9 – EE 5342” UTA  • Cheung, Nathan “ Lecture 17 – EE 143” UC Berkeley  • http: //et.nmso.edu/ETCLASSES/vlsi/files/CRYSTAL.HTM  • Hastings, Alan “The Art of Analog Layout”, Prentice Hall, New Jersey, 2001  • Campbell, Stephen A. , “The Science and Engineering of Microelectronic Fabrication”, Oxford University Press, New York, 2001 • Alvarez, Antonio, “BiCMOS Technology and Applications”, Prentice Hall, New Jersey, 2001

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