A NOVEL REMOTE TECHNIQUE FOR HIGH-RATE PLASMA POLYMERIZATION WITH RADIO-FREQUENCY PLASMAS

Remote plasma polymerization is the method of choice for achieving hig h deposition rates with low thermal substrate load and damage. Since t he radical density roughly scales-up with the plasma excitation freque ncy, microwave plasmas are often used to yield optimum results. Howeve r, scale-up often causes problems in terms of plasma homogeneity over extended areas. It has been found also that a high degree of molecular gas fragmentation may be detrimental to high deposition rates, and in extreme cases leads to etching instead of deposition. In these cases r.f.-excited plasmas offer an attractive technological alternative wit h respect to performance and source complexity. We report on results w ith a linear 13.56 MHz hollow cathode multijet discharge (HCMD) operat ed in the remote processing mode. This type of source features an arra y of equidistantly arranged holes placed alongside the source tube axi s. The incremental length of such a tube is chosen as 30 cm. Several o f those tubes can be connected in series yielding total source lengths as multiples of 30 cm. Scratch resistant as well as anticorrosive thi n films based on hexamethyldisiloxane (HMDSO) and hydrophobic layers b ased on fluorocarbon monomers have been deposited successfully. Typica l growth rates were 60 nm min(-1) for fluorocarbons and 1400 nm min(-1 ) for HMDSO. The films exhibit an excellent thickness homogeneity alon g the linear tube axis better than 3.5%. Similar thickness variations could be achieved by moving planar substrates such as foils or membran es across the remote plasma zone.