PROJECT TITLE :

Ultraviolet-Assisted Release of Microelectromechanical Systems From Polyimide Sacrificial Layer

ABSTRACT:

Process heating of microelectromechanical systems (MEMSs) devices hardens polyimide sacrificial layers, complicating the final unleash and lowering yield for delicate structures. This paper reports ultraviolet (UV)-assisted unleash, that is demonstrated on an MEMS cantilever fabricated by an eight-mask photolithographic method. A commercial co-developable polyimide ProLift one hundred (Brewer Science) sacrificial layer was used. The process subjects the device to multiple heat treatment steps. Each wet chemical etching and dry reactive ion etching were explored. Throughout the former, large sheets of hardened polyimide floated free of the substrate to break delicate MEMS structures. The latter is sometimes slow, therefore that grass appears during long exposures to plasma ions. The solution reported here is UV exposure previous to release. Optical constants of the sacrificial layer material, which were baked to simulate thermal histories throughout numerous fabrication steps, were measured to understand the effectiveness of UV exposure. Wet and dry etch rates were measured as a operate of UV dose. Finally, the advantages of UV pretreatment were demonstrated during the discharge of actual MEMS cantilevers. [2015-0193]