fab. and test, of SiC electrostatic cantilever actuato


By Liudi Jiang , R. Cheun, M. Hassan and A. J. Harri, J. S. Burdes, C. A. Zorman, M. Mehregan.


Although micromachining techniques for silicon ~Si! are well developed and a range of silicon microelectromechanical systems ~MEMS! have been fabricated, Si MEMS are not suitable for use in harsh environments including locations of high temperature, high frequency, high wear, and corrosive media. In contrast, silicon carbide ~SiC! is an excellent candidate for microsensors and microactuators for use in extreme conditions due to its outstanding physical and chemical properties. 1 In particular, because of the high Young’s modulus (E) of SiC and the relatively low-mass density ~r!, the larger ratio of AE/r will result in significantly higher resonant frequencies for SiC beam structures compared to their silicon and gallium arsenide counterparts. 2 Micromachined SiC resonant devices have been fabricated in the past, these include pressure sensors, 1 lateral resonant structures, 3 and micromotors. 4 However, most of the fabricated devices make use of bulk micromachining or micromolding techniques that tend to be more complex than surface micromachining. Significant bending effect has also been observed in released cantilever beams, especially in longer beam structures. The bending effect has been attributed to the result of a bending moment induced by a residual stress gradient through the film thickness 1 and also due to surface tension encountered in the wet etch processes. In addition, comparing with dry etching techniques, there is also less control of etch rates and etch profiles using wet etch to release resonance structures


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