I have the following device structure PZT on Pt on Ti on SiO2 on Si with a
Si3N4 back face mask. Before etching in KOH The PZT is secured to a glass
plate with black wax, so as the face with the nitride mask will be etched.

During etching KOH got under the black wax and appears to have detached the
Ti/Pt from the SiO2. It is not clear if the etchant has reacted with the Ti or
with the SiO2. Has anyone else come across this before?  Would anyone
understand the chemistry involved.

Regards


Richard