2 - Technologies

Vacuum pyrolysis is a common technology for preparing parylane films. These thin film are deposited using a vacuum process in which the crystalline solid dimmer (di-p-xylylene) is sublimed under vacuum at 100-250 °C and then pyloyzed at about 450-750 °C to give a nearly quantitative yield of the reactive intermediate, p-xylylene. Although this is stable in the gas phase, it condenses and simultaneously polymerizes on any solid surface at a temperature less then 120 °C to give a continuous film of linear, high molecular weight poly(p-xylylene) called parylene.

Polymerization of simple organic monomer gases on surface under electron bombardment was observed many years ago and it can be used for the deposition of thin polymer films. It was proved experimentally that active sites are produced on the surface by the electron beam and the polymer film grows by interaction of adsorbed monomer with these active sites rather than by direct collision of gas phase molecules. The process if often used to prepare polymers from butadiebe or silicon oils, for example.The mechanism of the UV-initiated polymer film deposition process is similar to the former one.

The glow discharge or so-called plasma polymerization process is similar to the plasma-enhanced chemical vapour deposition and it can be performed in PECVD and RF sputtering equipment, which is widely used in the fabrication of electronic components and integrated circuits. The reactor chamber has to be evacuated to 10-2 Pa, after which the monomer gas will flow in up to a pressure of 1-20 Pa. A high voltage RF source will then be switched on with a capaticive coupling of the glow discharge.