The effect of humidity on the reliability of a surface micromachined microengine
- 20 January 2003
- conference paper
- Published by Institute of Electrical and Electronics Engineers (IEEE)
Abstract
Humidity is shown to be a strong factor in the wear of rubbing surfaces in polysilicon micromachines. We demonstrate that very low humidity can lead to very high wear without a significant change in reliability. We show that the volume of wear debris gen- erated is a function of the humidity in an air environment. As the humidity decreases, the wear debris generated increases. For the higher humidity levels, the formation of surface hydroxides may act as a lubricant. The dominant failure mechanism has been identified as wear. The wear debris has been identified as amorphous oxidized silicon. Large slivers (approximately 1 micron in length) of debris observed at the low humidity level were also amorphous oxidized silicon. Using transmission electron microscopy (TEM), we observed that the wear debris forms spherical and rod-like shapes. We compared two surface treatment processes: a fluorinated si- lane chain, (FTS) and supercritical CO2 dried (SCCO2). The mi- croengines using the SCCO2 process were found to be less reliable than those released with the FTS process under two humidity lev- els.Keywords
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