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.