Large area VHF plasma polymerisation electrode system

VHF excitation of the discharge using frequencies in the range of 40–100 MHz has been noticed to result in high quality films at high deposition rates due to lower electron temperature and higher plasma densities in comparison with the mostly used 13.56 MHz or low frequency excitation. Polymer chain degradation and the formation of weak boundary layers due to long exposure times can be avoided. ma polymerisation reactor was developed for substrate dimensions of 500 mm × 500 mm up-scalable to about 1 m2 and an excitation frequency of 40.68 MHz. An process up-scaling from a small electrode size reactor was done. Hydrocarbon films were deposited on polymer plates with deep trenches (aspect ratio of up to 6). A film non-uniformity smaller ≤±10% and a deposition rate of about 1 nm/s were achieved. A high radical density and low pressure are necessary to obtain a good conformity. The reactor cleaning was done by plasmachemical etching using an oxygen process. The bombardment of the substrates by high energy electrons could be minimised.