I am currently trying to etch a Si wafer with hot KOH. There is a Si3N4
mask (1 um) on the back face wafer. There is a ceramic film on the other
face, this film requires several high temperature treatments up to 750 C
(drying and sintering), before the etching can be started. I do not
believe that these thermal treatments damage the nitride. However
continued removal and replacement of the nitride mask onto a hotplate
might result in tiny scratches in the nitride and lead to pinholes in
the etched sample.

After etching of the back face for >12 hours, there are large pinholes
(300 um wide by 600 um deep) in my samples. How can I protect the
nitride from scratching / damage?



Richard Haigh