Hello all,

Some colleagues of mine have been doing some ICP silicon etching and
have come across a major issue.

They use small substrates which have to be attached to a 4 inch silicon
carrier wafer. The following structure is used (from top to bottom):

Patterned AZ4562 photomask
Silicon substrate (this will be etched)
Cool grease used to provide thermal contact between carrier wafer and
substrate
AZ4562 ~ 6 um thick spun onto Carrier Wafer
4 inch Carrier wafer

They have found that after the etch the back of the silicon substrate
(i.e. side which is not etched) has some carbon looking deposits which
cannot be removed in O2 plasma or solvent. Does anyone have any idea
where this carbon is coming from?

I myself do a lot of ICP etching and have not seen this before so am at
a loss to explain it.

Many thanks!

--
Dr. James Paul Grant
Postdoctoral Research Associate
Microsystems Technology Group
76 Oakfield Avenue Room 3
University of Glasgow
Glasgow
Scotland
G12 8LS

Telephone: +44(0)141 330 3374