| The purpose of this research is to enhance dynamic performance of MEMS devices through use of damping treatments. In particular, I have achieved two goals. The first goal is to develop passive and active damping designs for microstructures. The passive damping design is a micro-constrained layer treatment, which consists of a silicon base structure, a spin-on viscoelastic photoresist layer, and an aluminum constraining layer through low pressure vapor deposition. Their thicknesses are 200, 4.5 and 1.8 microns, respectively. The damping results from cyclic shearing of the viscoelastic photoresist layer during vibration. The damping coefficients were improved 40% and 646% experimentally for the first and second modes, respectively. Next, the active damping design is a PZT circuit with a feedback controller. PZT thin films are patterned and fabricated to serve as actuators on vibrating silicon structures. Based on the measured sensor signals from a laser vibrometer, a phase shifter alters the phase and an amplifier drives the PZT actuators to suppress the vibration. The resonance amplitude of the first mode was reduced by 66%.; The second goal is to fabricate PZT thin films through use of sol-gel processing and electrophoresis for the active damping design. Three fabrication methods were developed for PZT films with thickness between one and ten microns. They are compatible with current silicon-based microfabrication processes. In addition, the thicknesses are thick enough to offer good actuation and sensitivity strength, but also thin enough to match the need of microstructure designs. Moreover, I demonstrated the films with superior actuation strength and excellent film quality to serve actuators and sensors for MEMS devices. |
