Investigating the use of spray-coating technology in MEMS applications

摘要

Fabricating the many different varieties of microelectromechanical systems (MEMS) poses complex processing challenges, particularly in the lithography area. Since MEMS devices rely on mechanical elements, they incorporate three-dimensional microstructures. While spin-coating technology is used to perform most photoresist deposition processes in the chipmaking area, it does not perform well on three-dimensional MEMS structures. The severe topography of MEMS devices, such as V-grooves, mesas, and etch cavities that pass entirely through the wafer, impedes or prevents the smooth flow of resist from the center to the edge of the wafer. Spray coating was developed to over- come these challenges. Because it deposits resist from above, spray coating works well on surfaces with severe topographies. Moreover, it consumes less material than spin coating. In addition to performing MEMS lithography applications, spray coating can be used to coat irregularly shaped or heavy substrates, coat many small substrates simultaneously, deposit a protective coating on top of fragile structures, and perform underfill steps. This article, based on work performed by EV Group (Schaerding, Austria), compares spin-coating with spray-coating technology.