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BioMEMS Device Fabrication Procedure

BioMEMS Device Fabrication Procedure. Theresa Valentine 8/19/03. Electrode Fabrication. Begin with Pyrex wafer, 100 mm diameter, 0.5 mm thickness Metal deposition E-beam evaporate 90Å Cr and 2000Å Au Must provide Au target Tom Loughran, ECE clean room, tcl@glue.umd.edu Resist patterning

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BioMEMS Device Fabrication Procedure

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  1. BioMEMS DeviceFabrication Procedure Theresa Valentine 8/19/03

  2. Electrode Fabrication • Begin with Pyrex wafer, 100 mm diameter, 0.5 mm thickness • Metal deposition • E-beam evaporate 90Å Cr and 2000Å Au • Must provide Au target • Tom Loughran, ECE clean room, tcl@glue.umd.edu • Resist patterning • Clean wafer with acetone/methanol/IPA • Dehydrate for 10 minutes on hotplate at 100°C • Cover wafer with HMDS primer while on spinner • Wait exactly 1 minute • Spin HMDS at 5000 rpm for 30 s • Apply one pipette of Shipley 1813 photoresist to wafer • Spin 1813 at 5000 rpm for 30 s • Soft bake for 1 minute at 100°C on hotplate • Expose at 150-200 mJ/cm2 dose • Develop for 30 s in Shipley 352 developer • Wash immediately • Hard bake at 120°C for a few minutes • Metal etching • Etch Au in Transene TFA etchant, 28Å/s (1 min 40 s works well for 2000Å) • Etch Cr in Transene 1020 etchant, 40Å/s (20 s works well for 90Å)

  3. Mold Fabrication • Remove SU-8 from refrigerator at least 2 hours before process • Begin with bare Si wafer, 100 mm diameter, 0.5 mm thickness • Clean wafer with acetone/methanol/IPA if not fresh from box • Dehydrate for 10 minutes on hotplate at 100°C • Cover 2/3 of wafer with SU-8/50 (from bottle) while wafer is on spinner • Spin SU-8 (recipe for 220 microns) • Pre-bake SU-8 (220 microns) for 100 min on hotplate at 95°C, 300°C/min ramp, auto off • Let wafer cool on hotplate for 30 min after auto-off • Expose with 900 mJ/cm2 dose • Post-bake for 30 min on hotplate at 95°C, 300°C/min ramp, auto off • Let wafer cool on hotplate for 30 min after auto-off • Develop for 22 min in SU-8 developer • Rinse wafer in fresh SU-8 developer (never water!) and let dry

  4. Fluid Control Layer Fabrication • Place SU-8 mold wafer in 0.1M SDS solution (1.44 g SDS powder per 50 mL water) for 2 minutes • Remove wafer and let dry naturally (no nitrogen) • Mix PDMS (Sylgard 184) in a plastic cup with curing agent in 10:1 weight ratio • Cover wafer with PDMS while wafer is on the spinner • Spin PDMS (recipe for ~130 microns) • Bake wafer in box furnace for 2 hours at 70°C • Hold in “Set” to program, press enter, select program “0” and press enter • SP1=70, time1=0.01 (1 min), SP2=70, time2=2.00, SP3=22, time3=off, JC=0 to ramp to 70°C as fast as possible, remain for 2 hours, turn off to room temperature • Remove wafer from box furnace, turn off furnace, and let wafer cool • Submerge wafer in a dish of methanol and loosen PDMS edges with razor blade or tweezers • Pull one side of PDMS gently from wafer until entire layer is free • Keep PDMS layer under methanol while aligning to electrode wafer • Remove electrode wafer with PDMS from methanol and check alignment under microscope • Use extra methanol squirted on wafer to allow fine alignment • Dry wafer gently with a wiper or let dry in air

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