Plasma chemical vapor deposition of hydrocarbon films: The influence of hydrocarbon source gas on the film properties

Hydrocarbon films were prepared by electron cyclotron resonance plasma depo sition from different hydrocarbon source gases at varying ion energies. The source gases used were the saturated hydrocarbons CH4, C2H6, C3H8, C4H10 ( n- and iso-) and the unsaturated hydrocarbons C2H4 and C2H2 as well as mixt ures of these gases with hydrogen. Film deposition was analyzed in situ by real-time ellipsometry, and the resulting films ex situ by ion-beam analysi s. On the basis of the large range of deposition parameters investigated, t he correlation between hydrocarbon source gas, deposition parameters, and f ilm properties was determined. The film properties are found to be influenc ed over a wide range not only by the energy of the impinging ions, but also by the choice of source gas. This is in contrast to a widely accepted stud y where no dependence of the film properties on the source gas was observed , this being ascribed to a "lost-memory effect." A strong correlation was f ound between the hydrogen content of the films and the film properties. Thi s strong correlation is explained on the basis of the random-covalent-netwo rk model. (C) 1999 American Institute of Physics. [S0021-8979(99)02819-4].