Microsystems Manufacturing via Embossing of Photodefinable Thermally Sacrificial Materials

摘要

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.