I received this letter in response to my reply to a recent KOH etching problem:


>
> Dear Alexander,
>
> Via Arno Steckenborn of Siemens, a query reached me concerning the
> etching of silicon in contact with Ti/Au in KOH solution. Indeed, it
> is very likely an electrochemical effect (galvanic cell formation). A
> solution to the problem might be to work with an oxygen-free KOH
> solution; without an oxidizing agent in solution there will be no
> cell formation. What is also worth trying is slightly higher etching
> temperature. The current between Au and Si required to passivate the
> semiconductor increases more strongly with temperature than the
> current due to the reduction of oxygen. We have used such effects for
> an etch-stop mechanism.
> See: Ashruf et al., Sensors and Actuators, A66 (1998) 284
> Ashruf et al., Mechatronics 8 (1998) 596
> If I can be of help please let me know.
>
> Best regards,
>
> John Kelly.

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Alexander Hölke, Postdoctoral Associate
     Microsystems Technology Laboratory
     Room 39-663, Massachusetts Institute of Technology
     Cambridge, MA 02139
Phone: 617-253-0724     [email protected]
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