If you incorporate one or both of the following tricks, you will definately
improve the outcome: get a thicker thermal SiO2 underneath the nitride
and/or adding a layer of Cr/Au ontop of the nitride.
hv
Temmuz CEYHAN writes:
Hello,
I am trying to do back side etching to Si based SOI wafer entirely
(500um etch). As etchant, I am using %30 KOH at 80 degrees for 7-8
hours. In order to protect the topside, I am using 500nm thick nitride
layer, however, because of the void formations during PECVD SiN
deposition process, KOH etches everything on the topside. DRIE is not
an option for me. Finally I decided to paste my sample to glass in
order to etch only the backside. Does anyone know of a paste, like
silver paste or epoxy, which can resist to extended hours of KOH etching
without getting etched at all?
OR!
Do anyone know of a way which I can protect the topside of my sample
during etching?
P.S. As I read the archives, I learned that Protek B3 coating or
annealing to high temperatures (800 degrees) can work, however, as some
of the members say, coating is hard to remove and I can not anneal up to
800 or more degrees since my features include Al (it has melting point
of 660 degrees)..
Thank you.
Temmuz CEYHAN