Mechanical Performance Analysis And Experiment Research On Laterally Driven Electrostatic Comb Silicon Micro Resonators

Laterally driven electrostatic comb silicon micro resonator is one of the earliest developed and applied MEMS devices. It can be used not only as transducers for converting the electrical energy to the mechanical one, but also as actuator to shoulders the response functions of the system information. Available for outputting large linear displacement, laterally driven resonators with meander suspensions or multi-folded-beam ones were studied in the dissertation. And the modeling, design and experiment were explored.Previous researches showed that resonance could be inspired by AC driving signals with or without DC bias voltages. But differences were that the resonance frequencies of resonators would equal to those of the AC voltages with large DC bias voltages, while it would be only a half of the AC voltage's frequencies without any DC bias voltages.A novel symmetry transformation theory was advanced. To achieve large displacement, an analytic mechanical model of the resonator with meander or multi-folded-beam suspensions was founded upon the symmetry transformation theory, electromagnetics and mechanics, and the influences of the structure parameters on the performances were discussed for the two types of resonators. Comparative studies were conducted between Fedder's experiment results of surface silicon resonators with meander suspensions and the calculated results by the model developed in the dissertation. And experiments were carried out on this novel type of resonators by the bulk silicon process, which could provide beneficial experience on the design of the large displacement resonators.To make objective appraisals on resonators' mechanical performances of different kinds, based upon the mechanical models of various kinds of resonators, several types of resonators with straight-leg, crab-leg, meander or multi-folded-beam suspensions were designed according to different requirements of surface and bulk fabrication process. And ANSYS simulations on the maximum static displacement and stress under certain outer loads, and resonance frequencies were simulated. It was found that the ANSYS results and the calculated ones matched well, which had validated the models developed preliminary. It was also found that the outputting displacement could be increased greatly by using resonators with multi-folded-beam suspensions, while the maximum stress was decreased at the same time. Under the same outer loads and at similar character size levels, resonators with multi-folded-beam suspensions could provide much larger displacements than those with meander suspensions, and so did the resonators with meander suspensions to those with straight-leg or crab-leg suspensions.Experiments were made on resonators designed by an optical microscope and CCD. Resonance frequencies, quality factors and the resonance amplitudes were measured. Response curves of the resonance amplititudes to the voltages were plotted out. The results showed that resonance frequencies tested were perfectly consistent, which showed the resonance frequencies were very stable for certain resonators. While there were obvious differences in quality factors and resonance amplitudes even for the same resonator. Therefore it could be concluded that the quality factors and amplitudes depended badly on the fabrication process and working conditions.Systematical experimental studies were also made on the performances of resonators under certain bias DC voltages or without any bias DC voltages. It could be found that about 7.5μm of displacements might be generated by only an 20V AC voltage without any DC bias voltage. And the displacements of the resonators with multi-folded-beam suspensions were about 5 times of those with straight-leg suspensions in similar characteristic sizes under the same voltages.The resonance frequencies by analytic models, ANSYS software and experiment consistent very well, which proved the validity of the model developed.With the experiment results of the bulk silicon resonators, semi-empirical formulas were identified for the quality factors and the ratios of amplitudes to voltages. It had been proved by the experiment results of the bulk silicon resonators that the new formulas were more consistent than the former models.Based on the mechanical models, programs for resonator design with user-friendly interfaces were developed with C and TCL/TK languages, and which has been successfully used in the IEEE V1.0 software systems.