• Clean the wafer with acetone, isopropanol, DI H₂0, and blow dry with filtered N₂
• Center the wafer on the chuck of the spin coater
• Apply enough Shipley S1813 photoresist to cover the wafer completely, with special care not to have any bubbles in the resist.
• Spin the wafer for 30 seconds at 3000RPM (acceleration at 300RPM/sec).
• Bake the wafer for 10 minutes at 100°C (or 2 minutes at 130°C) on a hotplate.
•  Align wafer on mask aligner, and expose to UV light at 150 mJ/cm^₂.
  •  Note: S1813, as a positive photoresist, is less sensitive to exposure dose than negative photoresists. As long as the baking is sufficient to cure the photoresist, the exposure dose simply needs to be above a minimum threshold to ensure accurate reproduction of features.
•  Develop in a bath of MF319 (or MF 321) developer for 30-60 seconds
• Rinse with DI H₂O to remove excess MF319 and blow dry with filtered N₂.

Shipley 1813 Removal
While commercially produced positive resist strippers are available, acetone leaves less residue and can be deposited into standard lab organic waste, since it does not contain
the levels of base that commercial strippers require for processing. Also, acetone is much less expensive than the commercially available resist strippers (approximately 1/4 the price per volume).

• Remove excess titanium and resist by sonicating in acetone for 480 seconds (8 minutes)
  • Note: the photoresist/titanium particles that are suspended in the acetone can create issues when depositing the SU-8 photoresist in later steps. To reduce contamination from these particles, repeat the sonication for an additional 480 seconds in fresh acetone
• Spray the wafer with acetone, isopropanol, and blow dry with filtered N₂