Hy Martina,
Your problem is that gold/silicon combination forms a galvanic cell.
In fact this tecnique is already used and it is called galvanic etch stop.
Here you can find more on this topic:
http://www.dimes.tudelft.nl/1998/s2/c2/c2-1-fundamentals.html

Max


From: "Martyna" 
To: 
Sent: Tuesday, November 18, 2003 11:50 AM
Subject: ITCSpam: [mems-talk] metal? etch mask for TMAH


> Hello,
>
> Does anybody know if gold mask can be used for TMAH etching? I have 1000 A
gold layer (with 100 A Cr) on a Si wafer. I used 5% TMAH and etch for half
an hour. The result is much below the typical etch rate.
>
> Before etching I removed native oxide with HF.
>
> Thank you for your help
>
> Martyna
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