HY,
   Long etches in any of the anisotropic etch solutions is very challenging with
metals already on them.  While EDP, KOH, etc. are selective to oxide, they are
not perfectly selective. And for EDP you loose even more selectivity when it
begins to oxidize (turn a dark brownish color).  So what happens is that the
metal layers are undercut as the oxide is etched.  This problem is frequently
made even worse by the presence of pin holes in the metals..  I think some
people have a degree of luck using a second metalization in addition to the
oxide masking layer.  This metal layer is often something like Cr/Au/Cr/Au.
Also there was a company developing a spin on coating for anisotropic etching, I
think it was Brewer Science, not sure how it worked though.


-Michael Martin
 U. of Louisville

>>> "Ho Yin Chan"  9/11/2007 11:35 PM >>>
Hi,

 Currently, I am doing EDP process with Ti/Au/Ag stacks on SiO2. It is found
that the metal stack pattern has gone after EDP etch.  Could you share with
me your experience? I am guessing if the problem is caused by Ti.