High-etch-rate anisotropic deep silicon plasma etching for the fabrication of microsensors

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Abstract
Dry plasma etching can offer many advantages in the fabrication of MEMS because of its anisotropic etching behavior, high etch rate, and its compatibility with traditional IC processing. A patented high density inductively coupled RFIC plasma source with independent source power and substrate bias control has been developed by Alcatel for deep etching of silicon. With the optimization of hardware and process parameters in a Fluorine based chemistry, processes with silicon etch rate up to 6 micrometers/min, etch uniformity better than +/- 5 percent, Si:SiO2 selectivity of more than 150:1, Si:photoresist selectivity of more than 50:1, etch depths of greater than 250 mm and profile angels of +/- 1 degree have been demonstrated. The silicon etch rate increases with increasing source power and Si:SiO2 selectivity increases with decreasing substrate bias. Substrate temperature can be maintained between -120 to +20 C during processing. The process parameters can be adjusted to give the desired performance for a particular application. Process results obtained at room temperature and at lower temperatures for different applications will be presented. The results indicate that this technology is a promising candidate for micromachining. The tool can be configured for production applications with vacuum loadlock and automated wafer handling.

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