Fabrication Suspended High-Aspect-Ratio Parylene Structures for Large Displacement Requirements

Abstract

A new method is presented for the fabrication of suspended parylene structures, using dry etching at low temperatures with a single standard silicon wafer. A silicon micro trench is used as a mold, in which parylene beams are fabricated through the deposition and removal of parylene in multiple stages, after which the structure is released from the same side of the silicon wafer. Compared to traditional processes, this approach eliminates the deposition of unnecessary silicon-dioxide, overcomes the need for double-sided micro-machining and supports the wafer during the release of the structure, thereby reducing process complexity and production costs. The proposed process is used to fabricate a test device of free-standing parylene beams 20 um in width, 3000 um in span, and 50 um in thickness to verify the feasibility of the structure based on suspended parylene. The ductile characteristics of the parylene beams allows elastic deformation of up to 100 um . CoventorWare simulation results show that parylene generates only 2.3% of the maximum Von Mises stress compared to a silicon based test device with the same dimensions. This new process is well-suited for applications to devices with large in-plane displacement and low stiffness.