Hi Grace,

   To give you a more accurate answer, you have to describe the type of
contamination.  Are they particulates, residue, etc?

Phil Tabada

-----Original Message-----
From: GraceKuo@gct.com.tw [mailto:GraceKuo@gct.com.tw]
Sent: Monday, August 12, 2002 4:45 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] Contamination issue of additive in THAH etching


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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