Hi Kuo,
   Can you be more specific? What does the contamination look like? Are
you sure its not just silicon that has precipitated out of solution? I
assume your using 5% wt./wt. of TMAH?  Dont be surprised if the solution
looks quite cloudy.

-Mike


>>> [email protected] 08/12/02 04:45AM >>>
Hi all,
i am working on silicon anisotropic etching using TMAH recently,
in order to control the roughness of etched silicon and the selectivity
to
Al and oxide,
we add silicic acid (SA) and ammonium persulfate (AP),
and as refer to S. Brida's recipe,
we add 2.5g AP per 15min to the etchant (~2L) to maintain the etching
rate,
after 1~3 hours of etching,
we take the sample out the etchant,
and rinse it in DI water,
and there are plenty of contamination over the sample,
if anyone have any ideal or experience about how to avoid the
contamination
issue,
many thanks,

Reference paper : S. Brida,"Microstructures etched in doped TMAH
solutions," Microelectronic Engineering, 53 (2000), 547-551

Grace Kuo
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