Principles and practice of an automatic process control for the deposition of hard nc-TiC/a-C:H coatings by hybrid PVD-PECVD under industrial conditions

Abstract

A study of a hybrid PVD-PECVD process of sputtering a titanium target in an argon/acetylene gas mixture was performed. This process was used for the deposition of nanocomposite coatings consisting of titanium carbide grains embedded in an amorphous hydrogenated carbon matrix (nc-TiC/a-C:H). The study was performed under industrial conditions employing a large-scale deposition device with a cylindrical sputtering cathode. When the acetylene supply was gradually increased, a discharge voltage drop and total pressure saturation simultaneously occurred at a certain acetylene supply. The hardest coatings were found always to be deposited at the acetylene supply corresponding to these deposition conditions. However, the acetylene supply to detect the voltage drop and pressure saturation was determined to be dependent on the cathode thickness. A fully automatic procedure suitable for the preparation of hard nc-TiC/a-C:H coatings by the hybrid PVD-PECVD process was proposed in this paper. This approach ensured that the optimal deposition setting was consistently found for the deposition process independent of the cathode thickness. The procedure was thoroughly tested, and it was demonstrated to be reliable and robust. Furthermore, the algorithm ensured the deposition of coatings with the same composition and the same high hardness throughout the cathode lifetime.