A novel technique for die-level post-processing of released optical MEMS

Abstract

This work presents a novel die-level post-processing technique for dies including released movable structures. The procedure was applied to microelectromechanical systems (MEMS) chips that were fabricated in a commercial process, SOIMUMPs from MEMSCAP. It allows the performance of a clean DRIE etch of sidewalls on the diced chips enabling the optical testing of the pre-released MEMS mirrors through the chip edges. The etched patterns are defined by photolithography using photoresist spray coating. The photoresist thickness is tuned to create photoresist bridges over the pre-released gaps, protecting the released structures during subsequent wet processing steps. Then, the chips are subject to a sequence of wet and dry etching steps prior to dry photoresist removal in O2 plasma. Processed micromirrors were tested and found to rotate similarly to devices without processing, demonstrating that the post-processing procedure does not affect the mechanical performance of the devices significantly.

A rapid technique to integrate micro-components on released MEMS dies using SU-8

“…For example, microoptoelectromechanical systems (MOEMS), which are used in a wide range of applications such as telecommunication, optical imaging, displays, optical switches [8] and laser printers [9], have been fabricated by post-processing MEMS dies. In [10], post-processing steps of dry/wet etching were performed on a MEMS die with a released movable structure in order to create smooth facets for efficient optical coupling. A thin coating of S1813 photoresist protected the movable structure and was dry stripped using oxygen plasma after post-processing.…”