The masks are designed such that positive resists can be used. AZ5214 can also be used in 'image reversal' mode (that requires a reversal bake and a flood exposure). The optical resist processes are very uncritical because we make all small features with the e-beam.

Negative tone optical resist for single-layer lift-off Official resist page
This resist comes from DIMES (courtesy C. Martin, AMC). There is a TUDelft recipe for it here. Leiden recipe:

1. Make sure your Si/SiO2 chips are clean (acetone does not always help, I use 10min O2 plasma etch in Plasmalab90)
2. Spin MaN1410 resist at 3000rpm (recipe 3 custom, 30-45sec gives ~1um). If resist does not stick, clean chips as described above
3. Bake, 90 C, at least 90 sec
4. Expose, 15 sec
5. Develop, MaD 533s for 15 sec (maybe even a bit less)
6. Rinse, DI water, 30 sec
7. Dry, N₂ (blow-dry the water)
8. If needed, postbake (90 C, x min)

Here is a graph of the time neede to dissolve the exposed parts in maD 533s, as function of exposure time. Dissolving unexposed parts takes 20 sec. UV meter gave 28 MW/cm².

1. Spin AZ5214E resist, recipe 1 or 2 of the spinner (6000 or 4000 rpm)
2. Bake, 90 C, 2.5 min
3. Expose, 15 sec
4. Develop, AZ312 MIF (metal ion free) developer : DI water 1:1, 40 sec (or just look at the process, don't time it)
5. Rinse, DI water, 30 sec
6. Dry, N₂ (blow of the water very carefully for materials that give bad adhesion)
7. If needed, postbake (90 C, 3 min)

1. Spin MaP 1205 resist, recipe 1 or 2 of the spinner (6000 or 4000 rpm)
2. Bake, 100 C, 30 sec
3. Expose, 15 sec
4. Develop, MaD 532 : DI water 9:1, 30 sec (just look at the process, don't time it)
5. Rinse, DI water, 30 sec
6. Dry, N₂ (blow of the water very carefully for materials that give bad adhesion)
7. If needed, postbake (90 C, 3 min)
8. After etching: remove remaining resist with acetone

Here is a graph of the time needed for developing, as function of the maD-532-concentration. Exposure time was 15 sec (this is very uncritical). UV meter gave 29 MW/cm².

1. Spin HPR 205 resist, recipe 1 or 2 of the spinner (6000 or 4000 rpm)
2. Bake, 90 C, 2.5 min
3. Expose, 15 sec
4. Develop, AZ312 MIF (metal ion free) developer : DI water 1:1, 40 sec (or just look at the process, don't time it)
5. Rinse, DI water, 30 sec
6. Dry, N₂ (blow of the water very carefully for materials that give bad adhesion)
7. If needed, postbake (90 C, 3 min)