Brian--

I've had a similar problem with Au on 100 A of Cr.
There is apparently an electrochemical effect when the more-electronegative
Au is on Cr.
I found that in etching off this 0.01 um of Cr, the Au was undercut by over
50 um in CR-7, but less than 10 um in CR-14.
You can measure the undercut by stripping off the gold after etching the
chromium.
For large features, using CR-14 is a solution, but it looks like it isn't
for you.

Another solution I've used is to ion-mill off the Cr, but a lot of Au is
removed at the same time.

Still another solution I've used is to make another mask that is a few
microns wider than the mask you used for the Au, then use it for the Cr.
Not having the Au exposed to the etchant eliminates the electrochemical
problem.

    --Kirt Williams

> We pattern Au over Cr (200 A) with subsequent removal of the Cr outside
the
> Au regions.  We find that the Au features, though usually surviving the Cr
> removal etch per se, do fail the 'tape test' post-Cr removal.  These
> features survive this test pre-Cr etch and are large enough that we
> wouldn't expect an isotropic undercut to cause them to lift-off  We have
> tried the commercially available Cr-7 and Cr-14 with the same
> results.  Does anyone have any suggestion as to an etchant that maybe more
> viscous (as it appears capillary forces etc... may be increasing lateral
> etch of the Cr versus vertical)?