Research On The Silicon-Based Integrated Planar Nano-Positioning Microsystem

As a typical micro electro-mechanical device, miniature robot applied in micro- and nano-manipulation domain has the characteristics of compactable configuration, light mass, low energy consumption and high integration, etc. Besides, it can accomplish some detection and repairing micro-handling tasks in relative narrow working space in which traditional mechanical system cannot enter. So, it has wide application in micro- and nano-manipulation domain in future. At the same time, in the micro electro-mechanical system (MEMS) domain, with the development of the silicon micromachining process, silicon-based miniature robot has been attracted wide attention and applied in various fields, such as data storage devices, optical equipments, scanning probe microscopes (SPM), etc, all of which provides miniature manipulation robot a new research and development direction for researcher and has become a new research hotspot of corporations and institutes all over the world. The final development objective of the research is setting up micro- and nano-manipulation system based on miniature robot.Sponsored by the National 863 Project Foundation—"Research on the key technologies of the typical micro-nano-scale components operations (project number - 2007AA04Z315)", the dissertation takes the design and analysis of the micro displacement sensor used to detect motion in plane as the research starting point on the basis of comprehensive understanding for the latest domestic and overseas situation of micro nano-positioning stage based on bulk micromachining. A novel micro xy-stage integrated with structure, laterally comb-driven actuator and displacement detecting sensor is proposed, in which the design thinking of the integration of actuation, structure and sensor-feedback is fully exhibited. Besides, intelligent control strategy has been applied in field of micro xy-stage control.Based on the theory of the electromechanical coupling, the two main failure dynamic models of the comb-driven actuator are modeled and analyzed. Besides, xy-stage dynamic characteristics are also analyzed under the impact of the air damping. The maximum velocity, the biggest overshoot displacement and natural frequency are obtained on the basis of the energy conservation principle, which provides theoretical reference for the design of micro xy-stage and experimental research.For the design of the micro integrated xy-stage, the driving efficiency of micro xy-stage is improved by optimizing design of comb electrode structure. The flexible element stiffness model and the output displacement model of micro xy-stage are built by using elastic mechanics method respectively. The key components structural analysis is performed using finite element method. By combing the analysis on theoretic model and simulation of mechanical system, the mechanism dimensions are designed. By optimizing design of the flexible seamless support beams, dynamic characteristic of the micro xy-stage and stability of the electrostatics comb actuator are improved. In order to improve micro xy-stage positioning accuracy, sidewall surface piezoresistive displacement sensor is integrated into the micro xy-stage to form closed-loop position feedback.On the aspect of the vertical sidewall surface piezoresistive displacement sensor design, the mechanical model of the elastic detecting beam is established by using elastic mechanical method. The optimal arrangement pattern of piezoresistor has been calculated on the basis of the principle of piezoresistive detection. The optimal piezoresistive dimensions and process parameters are obtained by analyzing displacement sensor key performances.In order to fabricate the designed integrated micro xy-stage, a set of process flows are brought forward and a series of important process experiments are carried out to optimize the process parameters and the process flows. Some typical process phenomena occurred during the micro-fabrication is analyzed and then the corresponding solutions are put forward. Foremost, a novel vertical sidewall surface piezoresistive technique is proposed and the process details are depicted. With this process, the piezoresistor is located at the vertical sidewall surface of the detecting beam to improve the sensitivity and displacement resolution of the displacement sensor.For the control strategy and the controller in the positioning system, the comb-drive power is designed and its performance is tested. Based on the analysis of the electrical characteristics and mechanics of machinery, their mathematical models are built respectively. Concerning the inaccurate model of the micro xy-stage due to fabrication imperfect, the single neuron adaptive PID controller is designed, which improves the dynamic performance and positioning accuracy.Finally, the experimental system is built and the performance testing of the integrated micro xy-stage has been carried out based on above analysis results. The experimental results verify that fabricated micro xy-stage can meet the micro- and nano-manipulation requirement of miniaturized structure, light mass, low energy consumption, high positioning accuracy and high resolution, etc. The work of this dissertation will provide theoretical foundation and practical experience for further research and the next design of nano-manipulation system based on the scan electrical microscope (SEM).