Nidhi,

The thickness of the base PDMS layer is not the problem.  The problem is that
the PDMS is relatively soft and will deform if coated with a stressed metal
layer.  Metal deposition is notorious for stressed films.

What is the thickness of the sputtered Chrome and Gold? Have you measured the
stress of the metal?  I suspect that the stress of the Chrome is too high.  If
you keep the thickness to no more than 250-300Å, it should help.  Also, minimize
the thickness of the gold.

It may be possible to reduce the film stress by adjusting the sputter power or
deposition pressure.  Maybe someone else has experience manipulating sputtered
films.

Dan

-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org] On
Behalf Of nidhi maheshwari
Sent: Wednesday, June 03, 2009 12:24 AM
To: General MEMS discussion
Subject: Re: [mems-talk] metallization on PDMS

Hi,

Barbara, thanks for your reply.  I tried reducing the thickness of PDMS
to around 200-300 microns by spin coating it onto a glass wafer. After
curing and plasma oxidation I tried sputter of Chrome and Gold. But it
still showed the same cracked layer. Can you or someone else please
suggest as to what I should be doing to avoid these cracked metal
films.

warm regards,
Nidhi