BioMEMS Device Fabrication Procedure

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_at_glue.umd.edu
• Resist patterning
• Clean wafer with acetone/methanol/IPA
• Dehydrate for 10 minutes on hotplate at 100C
• 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 100C on hotplate
• Expose at 150-200 mJ/cm2 dose
• Develop for 30 s in Shipley 352 developer
• Wash immediately
• Hard bake at 120C for a few minutes
• Metal etching

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 100C
• 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 95C, 300C/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 95C,
  300C/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

RPM1 240 RPM2 500 RPM3 1200 RAMP4 1
RAMP1 1 RAMP2 1 RAMP3 1
TIME1 3 TIME2 7 TIME3 20
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 101 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 70C
• Hold in Set to program, press enter, select
  program 0 and press enter
• SP170, time10.01 (1 min), SP270, time22.00,
  SP322, time3off, JC0 to ramp to 70C 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

RPM1 100 RPM2 200 RPM3 500 RAMP4 3
RAMP1 1 RAMP2 1 RAMP3 1
TIME1 3 TIME2 17 TIME3 60