Photolithography Protocol

Photolithography Protocol

Photolithography Protocol

V 2.0

Joshua

 

Outline

  1. Chip Preparation
  2. Spin Coating

III. Exposure

  1. Development
  2. Metal Evaporation
  3. Lift-off

 

  1. Chip Preparation
  2. Use 3” or 4” Silicon Wafer
  3. Clean wafer (front and back) with acetone. Flush thoroughly with isopropanol (IPA) to avoid

acetone residue.

  1. Dry wafer with N2 gently.

 

  1. Spin Parameters
  2. Pre-coat wafer with HMDS
  3. Deposit ~1” diameter of HMDS on wafer surface.
  4. Spin 5s @ 500 RPM / 40s @ 4000 RPM
  5. No post-spin bake is necessary
  6. Coat wafer with LOR3A resist
  7. Deposit 1 small pipette of resist on wafer surface.
  8. Spin 5s @ 500 RPM / 40s @ 4000 RPM
  9. Bake 5 min @ 180C
  10. Coat wafer with S1805 resist
  11. Deposit 1 small pipette of resist on wafer surface.
  12. Spin 5s @ 500 RPM / 40s @ 4000 RPM
  13. Bake 5 min @ 115C

 

III. Exposure – OAI 808 Aligner (consult operating manual for full directions on use)

  1. Load outer electrode mask into 5” mask holder. Make sure to activate mask vacuum
  2. Load wafer into appropriate-sized wafer chuck. Activate sample vacuum
  3. Calibrate gap
  4. Set gap to 30 μm and exposure time to 10s
  5. Perform alignment (if necessary)
  6. Move sample to contact position and activate N2 hard contact
  7. Expose the wafer
  8. Unload wafer and mask

 

 

  1. Development
  2. Put on PPE (chemical gown, face shield, and chemical gloves)
  3. Transport MF-319 developer and large (>4” diameter) beaker to base hood
  4. Pour into beaker enough developer to completely cover wafer
  5. Immerse chip in developer for 60s. Use gentle stirring motion
  6. Rinse chip with DI water for 30s to stop reaction
  7. Dry chip with N2

 

  1. Metal Evaporation (Lesker #3 PVD)
  2. Run chamber vent recipe
  3. Clean chamber
  4. Wipe door gasket area with IPA on cleanroom wipe
  5. Vacuum chamber interior. DO NOT MAKE CONTACT WITH FILAMENT
  6. Replace plastic window cover if necessary
  7. Load Au and Cr crucibles in chamber
  8. Load sample in chamber
  9. Unload platen from top of chamber. Lift up slightly, then pull out.
  10. Fix sample as close to center of platen as possible
  11. Return platen to position in chamber
  12. Run pump-down recipe – wait for pressure to reach 3×10-6 Torr (about 3 hours)
  13. Deposit Cr
  14. Rotate crucible holder to Cr source
  15. Turn on e-beam HV
  16. Ramp up voltage (rate 0.05, no more than 2% at once) until deposition rate is ~1Å/s
  17. Deposit 50 Å of Cr (5 nm)
  18. Ramp down voltage at rate 0.05. DO NOT ABRUPTLY CUT OFF VOLTAGE, OR SERIOUS

DAMAGE TO THE CRUCIBLE MAY OCCUR.

  1. Turn off e-beam HV
  2. Deposit Au
  3. Rotate crucible holder to Au source
  4. Turn on e-beam HV
  5. Ramp up voltage (rate 0.05, no more than 2% at once) until deposition rate is 1-2Å/s
  6. Deposit 550 Å of Au (55 nm)
  7. Ramp down voltage at rate 0.05. DO NOT ABRUPTLY CUT OFF VOLTAGE, OR SERIOUS

DAMAGE TO THE CRUCIBLE MAY OCCUR.

  1. Turn off e-beam HV
  2. Wait 5-10 minutes for sources and sample to cool
  3. Run chamber vent recipe
  4. Unload Cr and Au crucibles
  5. Unload sample; replace platen
  6. Clean chamber
  7. Wipe door gasket area with IPA on cleanroom wipe
  8. Vacuum chamber interior. DO NOT MAKE CONTACT WITH FILAMENT
  9. Replace plastic window cover
  10. Run pump-down recipe
  11. Deposit Al (per CSSER regulations)
  12. Rotate crucible holder to Al source
  13. Turn on e-beam HV
  14. Ramp up voltage (rate 0.05, no more than 2% at once) until deposition rate is 2-3Å/s
  15. Deposit 2000 Å of Au (200 nm)
  16. Ramp down voltage at rate 0.05. DO NOT ABRUPTLY CUT OFF VOLTAGE, OR SERIOUS

DAMAGE TO THE CRUCIBLE MAY OCCUR.

  1. Turn off e-beam HV
  2. Lift-off
  3. Select a glass container sufficient in size to hold the substrate
  4. Fill container with Remover-PG to a sufficient level to cover the substrate
  5. On a hotplate, heat the Remover-PG to 80 ⁰C.
  6. Soak the substrate until the resist and deposited metal film have completely

lifted-off from the substrate. The time depends on metal area and thickness, and can range from tens of minutes to a few hours.

  1. Remove the substrate from the Remover-PG, and rinse with isopropanol, then

blow dry with nitrogen.