I would like to use silicone rubber in the lab
acremann at slac.stanford.edu
Mon Jan 31 14:38:47 PST 2005
One of the tricky processing steps is KOH backside etching of wafers
with metal structures on the frontside. The main problem is
the protection of the front side during the etch process. We currently
use black wax for that purpose. We had some problems with
this in the past where the black wax layer failed during very long
etches (up to 40 hours for 1.2mm thick Si wafers).
We would like to try to put two wafers front to front and use silicone
rubber to seal the edge. In addition, we plan to have black wax on the
We did some tests with silicone rubber and its ability to withstand KOH
in our lab at SLAC and this method looks promising.
We used the following product for our tests (copied from the home depot
catalog :-)) ):
"GE 2.8 oz. Clear Silicone Household Glue
Model GE280 3TG
100% silicone. Permanently flexible. Adheres to tile, porcelain, glass,
fiberglass, marble, wood, steel, aluminum, brick, mortar, concrete, and
most plastics. Lifetime satisfaction guarantee. Won't dry out, crack,
chip or peel. Easy to use squeeze tube. Can be used as glue, sealant,
caulk or gasketing, and for many patch and repair applications around
the house and shop."
For our real wafers, we would like to test this method in the cleanroom.
As similar materials are likely used during construction of the wet
benches, I hope it will be possible to get approval for
this material. Of corse we only deal with gold contaminated wafers and
this is our last processing step (followed by solvent cleaning and
sawing the wafer). We also will NOT heat the
wafer to a temperature higher than 75C (in KOH) and if necessary, we can
do the KOH etch in our lab at SLAC.
I did not find the MSDS that corresponds directly to this product, but
there is a link containing more information about it:
More information about the specmat