Vapor Deposition Polymerization of para-Xylylene Derivatives-Mechanism and Applications

Abstract

Vapor deposition polymerization (VDP) of poly(p-xylylene) and its derivatives is discussed. The process, known as parylene technology, is a thin film vacuum deposition method, utilizing [22]-paracyclophanes as precursor compounds and it is approximately forty years old. Today, thanks to its applications in miniature electromechanical systems (MEMS) and all organic semiconductor (AOS) technologies, it is a subject of a strong renewed scientific interest. The emphasis of this review is put on the mechanism of parylene deposition as well as on this process' applications. As far as the deposition mechanism is concerned it is discussed in terms of both chemical reactions and physical phases and phenomena involved. The occurrence of two different mechanisms, of which the solid phase addition polymerization takes place at temperatures below monomer melting point, is particularly stressed. The diversity of parylene uses, both present and future, is also discussed with an attention on the development of future biomedical, MEMS and AOS applications.