Hi

I’m using SU-8 2050.
I make 50um thick SU-8 layer on Au seed layer and open vias 12um diameter
in SU-8 for electroplating Au, using SU-8 as mold.
Electroplating is unsuccessful because not all SU-8 is removed from seed layer.

My process detail is like following.
Pre-baking :  20 degree C (room temp.)->ramp up to 65C with 3C/min->stay 3 min
in 65C-> ramp up to 95C with 3C/min -> stay 9 min in 95C
           ->ramp down to 65C with -3C/min -> stay 10 min in 65C
           ->ramp down to room temp with -1C/min
I’ve been using 400nm UV light with 10mW/cm^2 intensity, 380mJ/cm^2 dose (about
38 sec exposure).
(We have Quintel Q-4000 mask aligner, so I can use 365nm UV light.)
Post-baking : 20 degree C (room temp.)->ramp up to 65C with 3C/min->stay 1 min
in 65C->ramp up to 95C with 3C/min -> stay 7 min in 95C
           ->ramp down to 65C with -3C/min -> stay 10 min in 65C
           ->ramp down to room temp with -1C/min
Developing : Agitating in SU-8 developer (microchem)

I tried to increase the developing time and RIE with 100% O2 , 200mTorr, 200W
for several min.
And also tried to dip in acetone for 10 sec.
All these were not working.
Actually I have some bigger features (100umx100um) on the same sample and those
are well developed.
I think I need to have more optimized or experienced values for exposure dose
and baking time.

Any suggestions to remove all SU-8 from Au seed layer?
You guys think 12um Diameter hole (with 50um thick) is ok or too small?

Thank you.

Jaesang Lee
Aerospace Engineering
Texas A&M University
[email protected]