USP Fabrication of Silicon Probes for Biosensors LSI

USP Fabrication of Silicon Probes for Biosensors LSI Dr. Marcelo Bariatto A. Fontes (Post-Doc) LSI / USP Dr. Rogério Furlan LSI / USP Dr. Jorge J. Santiago-Avilés UPENN http: //www. lsi. usp. br/~bariatto/ SBmicro 2000 - Manaus - Amazonas

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

INTEGRATED MICROSYSTEMS GROUP - DMI - LSI - USP MICROPROBE FABRICATION • Glass micropipette • Carbon • Metal – Single electrode – Low reproducibility http: //www. lsi. usp. br/~bariatto/ SBmicro 2000 - Manaus - Amazonas 3

INTEGRATED MICROSYSTEMS GROUP - DMI - LSI - USP 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 4

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

INTEGRATED MICROSYSTEMS GROUP - DMI - LSI - USP PROBE DESIGN • Needle shape general purpose electrochemical system • Multipoint and multispecies detection • 2 to 10 gold µelectrodes – 90 to 340 µm tip Ag/Ag. Cl reference Platinum auxiliary http: //www. lsi. usp. br/~bariatto/ SBmicro 2000 - Manaus - Amazonas 6

INTEGRATED MICROSYSTEMS GROUP - DMI - LSI - USP FABRICATION STEPS • Boron etch stop mask 312 • Plasma etching mask 1 probe shape mask 2 lines / contacts mask 3 windows http: //www. lsi. usp. br/~bariatto/ SBmicro 2000 - Manaus - Amazonas 7

INTEGRATED MICROSYSTEMS GROUP - DMI - LSI - USP FABRICATION RESULTS - SEM and AFM • High reproducibility • Roughness : 12. 5 nm (rms) – 16 % area http: //www. lsi. usp. br/~bariatto/ SBmicro 2000 - Manaus - Amazonas 8

INTEGRATED MICROSYSTEMS GROUP - DMI - LSI - USP FABRICATION RESULTS - Si PROBES • Etch stop SIMS analyses [B]=1. 25 1020 at. /cm 3 • Plasma etching http: //www. lsi. usp. br/~bariatto/ SBmicro 2000 - Manaus - Amazonas 9

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

INTEGRATED MICROSYSTEMS GROUP - DMI - LSI - USP FABRICATION RESULTS - FINAL DEVICE http: //www. lsi. usp. br/~bariatto/ SBmicro 2000 - Manaus - Amazonas 11

INTEGRATED MICROSYSTEMS GROUP - DMI - LSI - USP 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. 4 x 1019 at. /cm 3 (SIMS) http: //www. lsi. usp. br/~bariatto/ SBmicro 2000 - Manaus - Amazonas 12

INTEGRATED MICROSYSTEMS GROUP - DMI - LSI - USP CONCLUSION - cont. • Plain silicon probes of 15 µm were obtained • Uncompensated mechanical stress between Si. O 2 and Si 3 N 4 – 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 13

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