Dear Colleague,

I have a suspended structure (named rulings) made by PECVD SiO2 (0.9 um
thick) and coated with Cr/Au (0.15-0.2um thick by evaporation). The space
between SiO2 and substrate is about 1.5um. The ruling is 150um long and 3um
wide. If I pattern them by etching (photoresist as the mask) and then
release, rulings bend up that means the center of the rulings is higher than
the anchor, which is not a bad situation. But if I make it by lift off, bad
thing happened. The steps are: depositing sacrificial layer, then PECVD
SiO2, then make a Cr/Au/Ni stack by lift off. Using metal stack as the mask
to RIE SiO2. Then release structure and remove Ni. By this way, the rulings
are all stuck on the substrate, which is impossible to actuate these
rulings. I assume it caused by residual stress.

How to explain this and how to save these rulings? Annealing? What is the
condition? Thanks in advance.

Yahong
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