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Substantial recent interest in microelectronics manufacturing has motivated significant work on
non-traditional processes such as embossing-based lithography. This work has been generally
limited to manufacturing conventional microelectronics, producing two dimensional patterned
surfaces and structures. To date, little work has been done to produce microelectromechanical
systems (MEMS), which can require production of complex three-dimensional and possibly free
standing structures.
This paper reports a novel method for manufacturing three-dimensional microstructures that can
be freely standing and/or fully released. The method involves the use of thermally sacrificial
polymers, i.e. materials that can be cleanly decomposed to gaseous products upon heating at
elevated temperatures. Such sacrificial polymers can be directly embossed and subsequently
overcoated with a variety of materials including other polymers, dielectrics, semiconductors, and
metals. Following the deposition of the overcoat layer, further processing can be performed on
the overcoat layer (e.g. selective etching or deposition of additional materials). Finally, the entire
structure is heated to the decomposition temperature of the sacrificial polymer which results in
the “dry” removal of the sacrificial layer, thus releasing the desired structures. The various
sacrificial materials that have been investigated are polynorbornenes and polycarbonates, and the
overlayer materials include polyimides, silicon oxide, and metals. This paper discusses the
various properties of these sacrificial materials, the printing and processing conditions for these
materials, and the use of this method for the fabrication of a MEMS based microfluidic system
with free standing and suspended obstructions.
This novel manufacturing technique meets the needs of MEMS manufacturing in that it can
produce three dimensional and free standing microstructures. It permits the fabrication of devices
and systems in only a few process steps that would otherwise be either substantially more
complicated or impossible to achieve. This process of coating, embossing, and overcoating can
also be repeated to build-up complex multi-layered structures.
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