Additive Processes for Polymeric Materials

Abstract

Polymers are an increasingly important MEMS material. They are available in diverse forms and possess material properties not found in more traditional microfabrication materials originating from the integrated circuit industry. These include, for example, improved fracture strength, low Young’s modulus, and high elongation. Many polymers also exhibit biocompatibility and chemical inertness which are desirable in challenging biological or chemical applications. Furthermore, low material and processing costs present interesting possibilities in MEMS both in terms of fabrication of novel research devices and mass production of inexpensive products. A variety of traditional and nontraditional processing approaches exists to manipulate polymeric materials as substrates, coatings, and sacrificial or structural layers in MEMS devices. A wide variety of polymer types and classifications exists (e.g., elastomers, epoxies, conductive polymers, hydrogels, thermosets, thermoplastics, etc.); it is the combination of material properties, processing conditions, and intended use (e.g., substrate, coating, sacrificial layer, or structural layer) that govern the selection of appropriate polymer type for a particular application. Several common MEMS polymer materials and their fabrication processes are reviewed here. The reader is also referred to Chapters 7, 8, and 9 for more in-depth discussions on wet/dry etching and lithography processes.