Technologies for creating a variety of microsensors, microactuators, and micromachines continue to be developed at a rapid rate. However, the capability for engineers to design these devices has been hampered by inadequate and inappropriate design tools. This paper identifies some of the critical issues facing the field, and presents a vision for the future.

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Surface micromachining is the fabrication of micromechanical structures from deposited thin films. Although the process dates to the 1960s, this paper will survey its rapid extension over the past few years and its application to batch-fabrication of micromechanisms and of monolithic micro electromechanical systems (MEMS). Two central issues in surface micromachining are: (i) the understanding and control of the material properties of microstructural films, such as polycrystalline silicon, and (ii) the release of the microstructure, for example by wet-etching silicon dioxide sacrificial films, followed by the drying and surface passivation of the microstructure. Recent developments in hinged structures for post-release assembly and high-aspect ratio fabrication of molded parts from deposited thin films promise to extend greatly the capabilities of surface micromachining technology.

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We have developed a new multi-layer structure of polycrystalline silicon field emitter array (poly-Si FEA) and thin film transistor (TFT), where poly-Si FEA and the TFT are successively fabricated using a thermally grown SiO2 mold and transferred to a glass substrate. During operation, the TFT not only controls amount of field emission but also stabilizes fluctuation of the field emission. Since the TFT does not decrease the space for poly-Si FEA fabrication, the structure will be a good candidate for high quality flat panel displays. In this paper, we present details of the fabrication method of the multi-layer structure, and also show the field emission control by the TFT for static and switching characteistics.

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