Hello Kuang,

Are you sure the silicon you're etching starts etching right away? It is
possible that there is a thin native oxide preventing immediate exposure of
the silicon surface to KOH. Try rinsing in buffered HF for a few minutes
(depending on the oxide thickness) prior to KOH etching.

Let me know if this helps.

Regards,

Michael

>From: "¤p¿«" 
>Reply-To: General MEMS discussion 
>To: 
>Subject: [mems-talk] KOH+IPA etching problem
>Date: Wed, 14 Apr 2004 04:36:45 +0800
>
>Dear all
>I would like to ask if anyone have experiences with  etching by KOH+IPA.
>I need to use KOH with IPA to get appropriate ratio of etching rate <100>
>to other higher surface, but it results in some problems.
>
><1>  The etching rate seems not stable. I try the same parameter (the
>concentration of KOH I use is below 30%, temp. is aournd 75~65 centigrade)
>but often get different results. Etching rate and ratio of different
>surface in first 1 hr seems different from following several hours.
>It means that I need to check etching rate and change the KOH everytime I
>etch.
>Could someone has the same experience or help me explain it?
><2> When I use KOH below 30% with IPA, the hillock problem become very
>serious, do anyone have some ways to solve this ?
>
>Regards,
>
>Kuang H.
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