Dear All,

     I have similar problem like Terry Zhu.... I have aluminum
interconnecting lines on my device.... After patterning and Sintering the
Aluminum lines, i deposited Au/Cr seed layer (for doing electroplating) on
top of it..... Now, I want to Etch the Au/Cr layer selectively. Etching Au
is not a problem, since underlying Cr is protecting my Al lines. Now, I wish
to etch Cr selectively. This selective etching of Cr includes the portion
right above Al interconnecting lines.

   Like Terry Zhu, we are also using Transene ethcant for Cr etching which
is affecting aluminum lines. Do anyone knows the Al etch rate of Transene Cr
etchant... i mean selectivity of the Cr etchant over Aluminum.

  I tried lift-off method using S-1813 (Positive PR) and also with Su-8
resist, But, it was not successful......

  Can anyone tell how Aluminum lines be protected against Cr etchant...
Whether dry etching will solve the purpose? Anyone has tried it?

Regards,
A. Ravi Shankar..



> ---------- Forwarded message ----------
> From: Terry Zhu 
> To: [email protected]
> Date: Tue, 16 May 2006 12:48:55 -0700 (PDT)
> Subject: [mems-talk] Lift off process for gold
> Dear All,
>
>   I have a structure off Au/Cr with plated Copper on top. I am trying to
> find a way etcing the Au/Cr (seed layer). I can either etch the Au/Cr after
> Cu plated or use lift-off process. However, I am concerned with etching
> Au/Cr after Cu plated without affect Cu. If I put resist first before seed
> layer of Au/Cr, Then pattern it again for Cu plating, I am not sure if I can
> lift off the seed layer. Can anyone give some ideas for either situations?
> What are the etchant(s) that is/are better for the processes? Thanks.
>
>   Terry Zhu