Effect of deposition temperature on the properties of thin polymer films deposited by plasma‐enhanced CVD using cyclo‐hexa‐hydrocarbons as monomers

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AbstractPlasma CVD is a candidate technology for the fabrication of optical polymer waveguides. It can deposit a film on any surface geometry and any substrate material at a temperature under 200 °C in a vacuum process. It also provides good thickness controllability and uniformity of the deposition film. In the present study, the effects of the deposition temperature on film properties, specifically the refractive index, deposition rate, and molecular structure, are discussed. The refractive index decreases as the deposition temperature rises. The logarithm of the deposition rate increases with the reciprocal of the temperature and the gradient of the deposition rate depends on the relative abundance of double bonds in the monomer source. The gradient does not change when CF4 is used instead of Ar as the gas mixed into the plasma, although the deposition rate increases by a factor of about five. We speculate that the deposition rate increases due to the increase in the abundance precursors produced by the presence of CF4 in the plasma and due to an increased abundance of dangling bonds on the surface of the deposition film caused by F radicals. We further speculate that the precursors incorporated into the polymer are selected on the substrate by the density of adsorption sites and the adsorption energy. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(4): 27–35, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10171