Try to use a solution of 20g : 20g : 100 ml of NaOH : K3Fe(CN)6 : H2O.
It is ok with copper. It etches Cr at the rate of 4-5 nm/sec.

Best regards.

Daniel Sang-Won Park, Ph. D.
UTD MiNDS (http://www.utdallas.edu/~jblee/research/index.html) Lab

----- Original Message -----
From: "Michael D Martin" 
To: ; ;
; 
Sent: Wednesday, August 18, 2004 12:37 PM
Subject: Re: [mems-talk] Chromium etchant selective to copper


> Hi Shweta,
>    If your geometry will allow it you might try placing a small voltage
> on either the chrome or copper or both to introduce selectivity. We used
> a small potential (~2.5V) on chrome electrodes to protect them in a
> chromic acid based chrome etchant. We also found that when chrome is
> electrically connected to copper, the copper is solvated before the
> chrome. This is an electrochemical effect so experiment with applying
> voltages or find an electrochemist to talk to.
>
> -Mike Martin
>
> >>> [email protected] 8/17/2004 2:15:25 PM >>>
> CR-14 by Transene had some selectivity on our experiments, etching Cr
> 5
> times faster than Cu.
> CR-7 actually etched Cu faster than Cr, so don't use that.
> See JMEMS etching papers, as reported earlier on this newsgroup.
>     --Kirt Williams
>
> ----- Original Message -----
> From: "Shweta Humad" 
> To: 
> Sent: Tuesday, August 10, 2004 2:57 PM
> Subject: [mems-talk] Chromium etchant selective to copper
> > Does anyone know of a chromium etchant selective to copper?
> > Thanks,
> > Shweta Humad
>
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