Processing parameters for the development of glass/ceramic MEMS

For the past few years we have been investigating the photophysical and photostructurable properties of Foturan, a photostructurable glass ceramic (PSGC) manufactured by Schott Glass Corp. In this paper, we discuss results on using Foturan as a MEMS and MOEMS substrate. Microfabrication in Foturan is possible through patterning by a pulsed UV laser, a subsequent heat treatment step, and chemical etching. In Foturan, the exposed areas undergo a selective phase change in which the native amorphous glass phase converts to a crystalline lithium silicate phase. The degree and type of crystallization are both sensitive functions of the irradiation and thermal processing procedures. Under high exposure dose, the crystallized areas etch up to 30 times faster than the unexposed material in HF, with the etch rate varying with irradiation dose. Because Foturan is transparent at visible through IR wavelengths, direct-write XYZ exposure with a pulsed laser can pattern complex 3-D structures within a sample. Devices made from Foturan may be glass, a glass-ceramic composite, or ceramic, with the final material composition depending on the irradiation and thermal processing procedures. Excellent aspect ratios (>30:1) have already been demonstrated in Foturan. Our interest is in making simple 3-D MEMS structures by implementing cost-effective manufacturing solutions that produce consistent results with a resolution on the order of ten microns.

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