Hello all,

I am new to lithography so I apologize if questions are excessively
ignorant.

I am having trouble hard baking thick film of AZ4620. I am spinning on
~20um twice. My 40um of AZ4620 exposes and develops well, but on hard
baking on hotplate the pattern is lost immediately as the PR reflows into a
dome. This PR will be dry etched (so it will see high heat eventually).

Hard baking:
I am hardbaking 40-60um of AZ4620 at 90C for 30min (reflows in under
10min).
I tried ramping 20-50C, holding overnight. Little rounding at edges, but a
two days later it had reflowed even more.

Other resists have had some problems, but I am still trying out new resists
(right now i'm on 4903, and two negative resists).

So can someone give me some guidelines on how to hard bake 4620 so I won't
have to change the process much? I'm very confused because I thought the Tg
for 4620 was not this low, and because I do single spins of 4620 (~10-15um)
and hardbake at 90C without reflow! Why would thicker application drop the
Tg so much?

Should I try exposing post development to UV to crosslink the top before
hard baking? Would that inhibit solvent evaporation too much? "Low and
Slow" bake over 3 days? Or just give up on 4620... (any AZ class PR that
would work here?)

Thanks in advance,
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