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
M.Sc. Student
Dept. of Electrical and Electronics Engineering
+90(312)-290-1247
Advanced Research Labs / National Nanotechnology Research Center
+90(312)-290-3525
BILKENT UNIVERSITY
06800
ANKARA/TURKEY