S0013-4651(98)11-028-5 CCC: $7.00 © The Electrochemical Society, Inc. stant is relatively small since the amount of fluorine that can be r K a s

ei Downloincorporated into SiO2 is limited. Another candidate material is polymer thin films, since they have low dielectric constants, below 3. Most of the studies on organic dielectric, are based on spin-on coatings followed by a curing process including k 5 2.4–2.6 for fluorinated poly(arylenethers), k 5 2.6–2.8 for flourinated polyimides, and k 5 2.4 for perfluoro-cyclobutane (PFCB). However, as the monomer is polymerized dur-ing the curing process, the macromolecules may align parallel to the substrate, leading to anisotropic properties. Another method is to use vapor deposition. It is solvent-free and can provide a uniform coat-ing over a large area. The vapor-deposited polymeric films are the following6-10: k 5 2.6 for Parylene-N,8 k 5 2.2 for Parylene copoly-mers, k 5 2.3 for Parylene-F,9 and k 5 1.9 for PTFE (polytetrafluo-roethylene, Teflon-AF). In particular, PTFE is a promising material