We are trying to use KOH to place a 5 micron deep etch on one side of
silicon wafer, and 25 micron on other side.  We are looking for a
protective coating we could apply to one side of the wafer after we've
done the first 5 microns of the etch, then continue with the final etch
on the other side.  Can anyone suggest a solution to this two step etch
process ?  Possibly a spin-on layer to be removed after the etching ?

Thanks,
Jim Stackhouse
Phil Klauder