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Fabrication and Thermal Actuation of 3-D MEMS

Master's thesis, University of Maryland at College Park

A novel process has been developed to fabricate three-dimensional micro electro mechanical systems (3DMEMS) with silicon-on-insulator wafers. This batch process incorporates deep reactive ion etching and aligned bonding of two wafers to produce robust devices with true three-dimensional features such as out-of-plane joints. The process was developed to create a spatial, multiple-degree-of-freedom (DOF) platform micromanipulator with applications in microrobotics and microphotonics. The platform is controlled by parallel single-DOF slider inputs, which are linked to the platform by compliant in-plane and out-of-plane joints. 

Electrothermal microactuators have been developed for positioning 3DMEMS devices. These actuators employ a geometric constraint to produce large translational deflections from thermal expansion of a single crystal silicon beam. A complete electrothermal and thermomechanical model has been developed to predict actuator performance. Actuator fabrication is fully compatible with the 3DMEMS process. 

The 3DMEMS process has been developed, and fabrication of an out-of-plane compliant joint has been demonstrated. High-aspect-ratio electrothermal actuators have been fabricated and tested thoroughly, and experimental results agree with model predictions. The temperature dependence of silicon properties has been found to improve actuator performance significantly. Problems with wafer bonding in the 3DMEMS process prevented a complete micromanipulator from being fabricated successfully; accordingly, solutions to improve wafer bonding are proposed. Other recommendations for future work include process refinement and electrothermal motor integration.

 

copyright 1999-2003 John M. Maloney