Hi
Al is more nobler than Cr.The electrochemical voltage dissolves the
oxide on the Cr which protects it initially.

Ravi Shankar
Semiconductor Complex Ltd.,
India.



On Sat, 5 Jan 2002, Onnop Srivannavit wrote:

> Hi All
>
> I found from web that HCl:H2O can etch Cr (shown
> below). However, they need to touch substrate with
> aluminum wire. I wonder if anyone know why we need to
> use aluminum wire to touch substrate. Is there any
> books or article talking about this phenomena? Thanks
> in advance.
>
>  Chromium Etchant
>
>      *    HCl:H2O2  (3:1)  This will also etch gold
> film.
>
>      *    HCl:H2O  (1:1)  Heat to 50C, immerse
> substrate
>           and touch with aluminum wire.
>
>      Chromium/Nichrome Etchant
>
>      *    HCl:H2O2  (3:1)  This will also etch gold
> film.
>
>      *    HCl and touch with aluminum wire.
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