Hi Ramesh

As the replies show there are several reasons why this is happening. Certainly
the suggested stiction problem is a high probability candidate. The best way to
fix this is to move to a dry process. Using a silicon sacrificial layer and
etching it with xenon difluoride may be the best solution. The etch has no
attack on aluminum and is capable of very long undercuts. If this looks like a
possible solution to your problem and you would like to try it please get in
touch with me. XACTIX is the overwhelming market leader in providing equipment
for isotropic etching of silicon using xenon difluoride.

 Best Regards
David Springer
XACTIX, Inc.

>I have fabricated array of mico cantilevers using aluminum. dimension are
>length=300um, width=200um, height=2um.(air gap3-4um) i am using sacrificial
>material and washing it away to free the cantilever. But most of the
>cantilevers have collapsed. I have also calculated the bending due to its
>own weight and i am getting answer in nanometers. Is this happening because
>of the E(Al)=70GPa or dimension is too large and collapsing due to its
>own weight? Or am i making calculation mistake?