Hi Isaac,

I guess AZ P4620 resist is a positive resist. How does the deep UV cure
work? We are looking for a photoresist that survives well 400 µm of
DRIE, while keeping its verticality. A hard bake of 200°C would
certainly increase the selectivity between resist and silicon.

Best regards

Michael

--------------------------------------------
Institute of Microtechnology
University of Neuchatel
Switzerland


-----Original Message-----

AZ P4620 resist is the conventional novolak-based resist which has the
glass transition temperature (Tg) around 125C. Tg is for novolak resin.
Besides solvent diffusion, it's more because the PGMEA solvent in this
resist has a boiling temperature around 145C, so hard bake 120C helps to
drive the solvent out but not all. Ideally, the resist will not reflow if
Tg is above the solvent boiling point, but not for this type of resist.
Other ways to hard bake without resist reflow include deep UV cure of the
resist surface to form a hard outer shell, then hard bake on hotplate up
to 200C to completely drive out the solvent and cross-link the novolak.
But you can't use stripper or acetone to remove the resist after process.
You need O2 plasma to etch it completely.

Isaac