Diffusive transport in supercritical CO2 drying of MEMS structures

Paul J. Resnick; Matthew G. Hankins

doi:10.1117/12.478208

16 January 2003 Diffusive transport in supercritical CO₂ drying of MEMS structures

Paul J. Resnick, Matthew G. Hankins

Proceedings Volume 4980, Reliability, Testing, and Characterization of MEMS/MOEMS II; (2003) https://doi.org/10.1117/12.478208
Event: Micromachining and Microfabrication, 2003, San Jose, CA, United States

Abstract

Supercritical CO₂ drying has been shown to be an effective method for drying complex MEMS structures with little or no stiction. This process typically involves transferring released parts from ultrapure water into a solvent, such as methanol, that is miscible with liquid CO₂, and subsequently displacing the methanol with liquid CO₂. During this process sequence, transport of methanol into and out of the tortuous pathways of the MEMS device is dominated by diffusion. The non-steady state diffusion equation (Fick’s second law) with length scales relevant to MEMS structures can be applied to understand the speed at which diffusion occurs. This analysis indicates that diffusion of methanol into the pathways of a MEMS device occurs very rapidly, typically on the order of minutes. Experimental data are consistent with the rapid diffusion hypothesis.

Citation Download Citation

Paul J. Resnick and Matthew G. Hankins "Diffusive transport in supercritical CO₂ drying of MEMS structures", Proc. SPIE 4980, Reliability, Testing, and Characterization of MEMS/MOEMS II, (16 January 2003); https://doi.org/10.1117/12.478208

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