during annealing at 380C Au/Ge form an eutectic, which alloys to GaAs to
form a contact.. lower temperature anneals may produce SOME alloying.. from
my experience, even alloyed contact is easily attaced by GaAs etchants..
I've used photoresist to protect these contacts on backside of the wafer
during the etch..

Mike
> -----Original Message-----
> From: Parshant Kumar [SMTP:kparshant@yahoo.com]
> Sent: Thursday, September 05, 2002 1:30 PM
> To:   mems-talk@memsnet.org
> Subject:      [mems-talk] delamination of Au/Ni/Ge/Au layers in Citric
> acid solution etch
>
> Hi All,
>
> I am working with the wet etch of GaAs in citric
> acid:Hydrogen peroxide::5:1. I am facing the problem that
> Electrode deposited as Au/Ni/Ge/Au layers start delaminated
> after 55-60 mintues of etching. However if we anneal the
> sample for 30 mintues at the 150 degree calcious, the
> effect is less.
>
> Any comment will be appericiated
>
> Thx
>
> Kumar
> Maryland MEMS Lab
> University of Maryland
> College Park-MD 20742
> Tel 301-405-0364
>
>
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