Kris,
      Almost all Au etches will undercut the mask to some exent.  Is this
what you mean by undercut?  You could possibly improve this by using a hard
mask such as SiO2.  It may be that the resist is not adhereing too well to
your Au.

-Lou

>From: kris 
>Subject: [mems-talk] Gold undercut
>Date: Thu, 16 Jun 2005 21:37:26 -0700 (PDT)
>
>I was wondering if KI+I2+H2O undercuts gold??
>
>Is there any AU etchant that does`nt undercuts AU.
>