Expanding plasma used for plasma deposition

Abstract

A description of the deposition process for the production of amorphous carbon coatings, based on decomposition of hydrocarbons in a new type of plasma reactor, is presented. In this reactor the dissociation and ionization of the original, carbon containing material takes place following injection in the thermal high density plasma of a cascaded arc. This plasma is close to local thermal equilibrium (LTE). The hot seeded arc plasma is cooled by allowing it to expand supersonically into a large vacuum system. In the expansion high particle velocities are attained, ensuring that the plasma composition does not change substantially before the substrate is reached. At the substrate an amorphous carbon film is deposited with rates up to 200 nm/s, which are measured with In-situ ellipsometry. The quality of this film, determined by parameters like refractive index, hardness, absorption coefficient in the infrared spectral region, resistance against oxidation, adhesion to the substrate and internal stress, is strongly dependent on the plasma parameters. These parameters can be controlled easily so the intensity and conditions of the particle flux impinging on the substrate can be influenced. Plasma parameters such as electron density, temperatures as well as drift velocities have been measured. © 1988 IUPAC