Hi Jeffrey I had the same experience with most of negative resist. They are very sensitive to the PEB bake temp and time and exposure dose in stepper. If you have good track and stepper, they are manageable. But if you have some particle on hot plates and so on, you can lose your control fast. Have you tried positive resist lift-off pattern by soaking on MF developer before exposure? Chris -----Original Message----- From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org] On Behalf Of Yue Mun Pun, Jeffrey Sent: Wednesday, May 16, 2007 2:39 AM To: mems-talk@memsnet.org Subject: [mems-talk] AZ5214E in image reversal mode Hi, I have tried to use AZ5214E in image reversal mode to pattern some alignment marks by lift-off process. I have compared the image reversal mode versus the positive imaging mode and found that the lift-off process using image reversal is much more difficult than the positive image mode. Can anyone advise me on this matter? Here is my image reversal process: 1. Coat SiO2 wafer with AZ5214E spun at 2500rpm. This gave me a resist of thickness 1.4-1.6um. 2. Soft bake at 95'C for 120s on hot plate. 3. Expose at 405nm near UV light with intensity of about 7.5mW/cm2 for 5.4s to obtain average energy of 40mJ/cm2. 4. Reversal bake on hot plate at 115'C for 120s. 5. Flood expose at 405nm with intensity of 7.5mW/cm2 for 160s to obtain average energy of 1200mJ/cm2. 6. Develop in AZ400K developer diluted in DI water to a ratio of 1:4 for 45-60s. 7. Thermal evaporation of 30nm Chromium. 8. Lift off via both Acetone and PGMEA (SU-8 developer). The wafer with the positive image was run as above except without the reversal bake aqnd flood exposure. Lift-off using the image reveral mode is very difficult even after overnight soak in PGMEA. Jeffrey _______________________________________________ Hosted by the MEMS and Nanotechnology Exchange, the country's leading provider of MEMS and Nanotechnology design and fabrication services. Visit us at http://www.mems-exchange.org Want to advertise to this community? See http://www.memsnet.org To unsubscribe: http://mail.mems-exchange.org/mailman/listinfo/mems-talk