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2 October 2001 Whole wafer critical point drying of MEMS devices
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Proceedings Volume 4558, Reliability, Testing, and Characterization of MEMS/MOEMS; (2001)
Event: Micromachining and Microfabrication, 2001, San Francisco, CA, United States
Stiction induced by capillary forces during the post-release drying step of MEMS fabrication can substantially limit the functional yield of complex devices. Supercritical CO2 drying provides a method to remove liquid from the device surface without creating a liquid/vapor interface, thereby mitigating stiction. We show that a continuous stirred-tank reactor (CSTR) model can be applied as a method to estimate the volume of liquid CO2 required to effectively displace the post release solvent. The CSTR model predicts that about 8 volume exchanges is sufficient to effectively displace the methanol to a concentration below the saturation point. Experimental data indicate that about 10 exchanges are adequate for repeatable drying of complex devices, which is in reasonable agreement to the model prediction. In addition to drying devices without inducing stiction, the process must be inherently non-contaminating. Data indicate that the majority of contaminants deposited during the drying process can be attributed to contaminants originating in the post-release solvent, rather than the supercritical CO2 process.
© (2001) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Paul J. Resnick and Peggy J. Clews "Whole wafer critical point drying of MEMS devices", Proc. SPIE 4558, Reliability, Testing, and Characterization of MEMS/MOEMS, (2 October 2001);

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