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4.1 Further 3DMEMS Process Improvements
A novel process has been developed and tested to fabricate true 3-D microstructures in single crystal silicon. This process can create many devices simultaneously through the use of batch fabrication techniques such as deep reactive ion etching, aligned wafer bonding, and HF etching. Silicon-on-insulator technology is used to create robust, high-aspect-ratio devices without an excessive number of aligning and bonding steps.
An important feature of the 3DMEMS process is the use of compliant beams as in-plane and out-of-plane joints. These joints allow the creation of a spatial micromanipulator that is controlled in parallel by several base-connected prismatic inputs.
The 3DMEMS process has been used to fabricate a 2 mm out-of-plane joint with an alignment error of less than 10 mm. Wafer bonding was partially unsuccessful and some other problems were encountered. Solutions to these problems are proposed.
Thermal actuation has been explored as a method to position 3DMEMS devices. V-beam actuators produce translational deflection and can be fabricated in arrays to increase output force. Moreover, actuator fabrication is fully compatible with the 3DMEMS process. A model has been developed and refined to predict deflections and forces available from V-beam actuators. Modeled results match experimental measurements well for a variety of actuator designs. Finally, a design strategy for optimizing actuator geometry has been derived. Design and testing of electrothermal motors is expected to lead to system-level integration with 3DMEMS micromanipulators.