Date on Master's Thesis/Doctoral Dissertation

5-2006

Document Type

Master's Thesis

Degree Name

M. Eng.

Department

Electrical and Computer Engineering

Committee Chair

Walsh, Kevin Michael, 1955-

Subject

Protective coatings; Microelectromechanical systems

Abstract

PARYLENE (poly-para-xylylene) is mostly used as a conformal protective polymer pin-hole free coating material to uniformly protect any component configuration on diverse substrates. This thesis describes in detail how the unique properties of parylene can be conveniently combined with MEMS technology to meet biocompatibility requirements of biological and chemical applications and develop unique microstructure shapes. Since etching of parylene is not readily possible, the best way to mold it into any shape would be to etch hollow molds in silicon and deposit parylene in them. It is easy to etch away the silicon mold for releasing these parylene structures. Parylene is nonreactive in wet etchants (like TMAH or KOH) that are used to etch silicon. These microstructures can be helpful in implants and other biomedical applications. This technique allows for the production of unique microstructures, many of which are not realizable by other fabrication technique. Any other material that conforms easily in silicon molds and is non-reactive with silicon and silicon etchants, can be molded in the shape of the fabricated molds. A material that is tested for these properties can be deposited because most of the fabrication processes (like etching, lithography, oxidation and wafer bonding) are performed only on silicon for preparing the molds. Materials deposited by CVD (chemical vapor deposition) or less viscous liquids that solidify on cooling, can be investigated for deposition in molds. Many useful applications can be derived by combining this method with various materials. CAD tools were used to simulate the mask features for designing this microstructure and to layout the photomask pattern. A fabrication procedure is devised from these simulation results and the process is implemented in a Class 100/1000 Cleanroom facility at the Lutz Micro/Nanotechnology Cleanroom core facility, University of Louisville. A complete guide to fabricate this MEMS-based parylene structure is provided in this thesis project. Important observations, complete experimental procedure and results are discussed in detail.

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