TMAH Etching of Silicon
The process is to be done at the wbflexcorr-3 and -4 or wbflexcorr-1 and -2.
1) Fill a designated TMAH beaker with a TMAH solution in water; enough to submerge a wafer in a Teflon TMAH single wafer holder or multiple wafers in a designated Teflon boat.
2) Heat the solution to not more than 80C on a hot plate.
3) While etching, cover the solution
with a condenser lid.
NOTE: Most people use a 20% TMAH
solution. It etches at ~68 microns per hour, or through a wafer of standard
thickness (500 microns) in approximately 7-7.5 hours.
The bath may be left over night, keep the bench enabled.
Nitride and Oxide can be used
as a mask. Photoresist does not hold up to TMAH (it dissolves immediately).
TMAH BEAKERS AND HOLDERS:
quartz ware is not to be used with metals or nonstandard materials because wafers
that get TMAH etched often go back into the main stream processing equipment.
Do NOT use contaminated
beakers and holders etc... because if they are not designated for TMAH they
could have been used for anything -- including gold