Hi all ,
         I have some problems with thermal evaporation. I am trying to do a lift
off of Cu / Cr top electrodes using LOR 5A
and Shipley 1813 bi layer stack.I am doing in situ Cr sputtering and then Cu
evaporation without breaking vacuum.
I see that during the lift off process the metal patterns peel off. I get good
lift off of 0.25 um Cu/ 200 A Cr. However
when I do 0.5 um Cu/ 200 A Cr , I do not get good yield on the devices ( most of
it peels off ).


My queries are :-

(1) What is the typical adhesion layer thickness used ? ( is thinner layer
better for any reason).

(2) Does Ti work any better than Cr.

(3) For doing Cu deposition is it better to do in steps of 0.25 um rather than
one long run.

My deposition conditions are are follows :

Cu ;-

Base pr - 5.0 exp (-6) torr
chamber pr - 4.0 exp ( -6 ) torr
current - 250 A
Voltage - 1.8 V

      Thanks in advance,
                 Dipankar
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