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Fabrication of Silicon Probes for Biosensors

Fabrication of Silicon Probes for Biosensors. Dr. Marcelo Bariatto A. Fontes (Post-Doc) LSI / USP Dr. Rogério Furlan LSI / USP Dr. Jorge J. Santiago-Avilés UPENN. MOTIVATION. Biological applications neural activities

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Fabrication of Silicon Probes for Biosensors

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  1. Fabrication of Silicon Probes for Biosensors Dr. Marcelo Bariatto A. Fontes (Post-Doc) LSI / USP Dr. Rogério Furlan LSI / USP Dr. Jorge J. Santiago-Avilés UPENN

  2. MOTIVATION • Biological applications • neural activities • intracellular recording • ionic distribution • electrical stimulation http://www.lsi.usp.br/~bariatto/ SBmicro 2000 - Manaus - Amazonas

  3. MICROPROBE FABRICATION • Glass micropipette • Carbon • Metal • Single electrode • Low reproducibility http://www.lsi.usp.br/~bariatto/ SBmicro 2000 - Manaus - Amazonas

  4. SILICON MICROMACHINED PROBES • Easy shape definition by computer-designed photomask • Multidetection and spatial distribution • High reproducibility • IC compatible (smart sensors) • Batch fabrication and • Low cost http://www.lsi.usp.br/~bariatto/ SBmicro 2000 - Manaus - Amazonas

  5. MICROMACHINING TECHNIQUES • Deep boron diffusion • high temperature and time • Lateral diffusion • “large”dimensions • Strong crystal orientation dependence • Boron etch stop • Plasma etching • Low temperature process • Better shape definition and thickness control • without lateral diffusion • Quick process • Low silicon crystalline orientation dependence http://www.lsi.usp.br/~bariatto/ SBmicro 2000 - Manaus - Amazonas

  6. PROBE DESIGN • Needle shape general purpose electrochemical system • Multipoint and multispecies detection • 2 to10 gold µelectrodes • 90 to 340 µm tip Ag/AgCl reference Platinum auxiliary http://www.lsi.usp.br/~bariatto/ SBmicro 2000 - Manaus - Amazonas

  7. FABRICATION STEPS • Boron etch stop mask 3 mask 1 mask 1 mask 2 mask 1 • Plasma etching mask 1  probe shape mask 2  lines / contacts mask 3  windows http://www.lsi.usp.br/~bariatto/ SBmicro 2000 - Manaus - Amazonas

  8. FABRICATION RESULTS - SEM and AFM • High reproducibility • Roughness :12.5 nm (rms) • 16 %  area http://www.lsi.usp.br/~bariatto/ SBmicro 2000 - Manaus - Amazonas

  9. FABRICATION RESULTS - Si PROBES • Etch stop SIMS analyses [B]=1.25 1020at./cm3 • Plasma etching http://www.lsi.usp.br/~bariatto/ SBmicro 2000 - Manaus - Amazonas

  10. FABRICATION RESULTS - COMPLETE SEQUENCE • Uncompensated mechanical stress • coverage and lines damaged http://www.lsi.usp.br/~bariatto/ SBmicro 2000 - Manaus - Amazonas

  11. FABRICATION RESULTS - FINAL DEVICE http://www.lsi.usp.br/~bariatto/ SBmicro 2000 - Manaus - Amazonas

  12. CONCLUSION • High reproducible micromachined multidetection silicon probe (80%) • Several probe designs were explored by varying the number of the detection electrodes • Plasma etching technique presented better characteristics of shape definition and processing time than “etch stop” • Boron etch stop  2.4x1019 at./cm3 (SIMS) http://www.lsi.usp.br/~bariatto/ SBmicro 2000 - Manaus - Amazonas

  13. CONCLUSION - cont. • Plain silicon probes of 15 µm were obtained • Uncompensated mechanical stress between SiO2 and Si3N4 • Bent structures  decrease the processing yield • Increase of probe thickness by plasma etching  45 µm • Compatibility with silicon microelectronic technology • New materials for interconnection and coverage (Poly-Si / Polymers) http://www.lsi.usp.br/~bariatto/ SBmicro 2000 - Manaus - Amazonas

  14. ACKNOWLEDGMENTS • CNPq • FAPESP • CNPq/PADCT/CDCT • Center for Sensor Technology at UPENN http://www.lsi.usp.br/~bariatto/ SBmicro 2000 - Manaus - Amazonas

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