Improving yield, accuracy and complexity in surface tension self-assembled MOEMS

An advanced process for self-assembly of three-dimensional micro-opto-mechanical systems (MOEMS) is demonstrated, based on deep reactive ion etching of bonded silicon-on-insulator material, sacrificial etching, and out-of plane rotation powered by the surface tension of thick photoresist pads. Improvements in structure definition and design are described, which have led to an increase in process yield to approximately 75% and in the best assembly accuracy to <0.1. Optical mirrors oriented at 45 degrees and 90 degrees to the substrate are demonstrated by simultaneous and sequential self-assembly, respectively. Profile measurements of assembled structures show very high surface quality, and distortions of parts by surface tension forces are identified. (C) 2001 Elsevier Science B.V. All rights reserved.