I regularly use some black wax to protect the front surface of my silicon
wafers during the KOH etch of the backside. Sticking a dummy wafer after
black wax application may be necessary. You should apply this process on a
hot plate above 120 C. After etch, hot plate and/or trichlorethane (TCE)
solvent can be used for cleaning.
=================================
Isa Kiyat