help with evaporating tungsten
Charis Quay Huei Li
cquayhl at stanford.edu
Mon Dec 11 18:40:18 PST 2006
Recently we have been trying in our lab to evaporate tungsten as
e-beam alignment marks. We are encountering some problems with poor
adhesion during liftoff and we were wondering if ay of you who do a
similar process would mind sharing your steps?
Our smallest feature size is about 100nm and we are using either
200K/950K or 495K/950K PMMA bilayer.
Initially, after just soaking in acetone, squirting and heating up
the acetone (and squirting again) one chip came out with extra metal all
over the place. I then tried sonicating in larger and larger time
increments, starting with 10s and finally going up to minutes at a time.
It looked like the metal wouldn't come off and wouldn't come off, and then
suddenly a lot of it came off at once at t = 20 minutes roughly.
Please let me know if you have any insight into this.
Thanks very much.
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