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