DEPOSITION OF THICK-FILMS OF OXYGEN-FREE HIGH CONDUCTIVITY COPPER BY UNBALANCED DC MAGNETRON SPUTTERING - SELF-BIASED AND BIASED CONDITIONS

Various thicknesses of copper films were deposited using a permanently unbalanced, d.c. magnetron sputtering source. To optimize the information obtained from a relatively small number of films, a Taguchi orthogonal array was used to investigate the effect of varying the process parameters. The process parameters investigated were the magnetron power, target to substrate separation, process pressure, substrate self-bias, substrate bias, and substrate temperature. For the various combinations of parameters, under self-bias conditions, the coating thicknesses varied from 11-mu-m to 195-mu-m for a run time of 1 h, the maximum deposition rate being in excess of 3-mu-m min-1. The films were very dense and of a highly ductile nature. Virtually all had a submicrometre grain size, which was unresolvable by scanning electron microscopy. At the self-bias voltage, high substrate current densities were extracted during coating, up to 20 mA cm-1. A bulk coating up to 1 mm in thickness was deposited during a continuous 8 h run. During this run, the current-voltage characteristics of both the magnetron and substrate electrodes were investigated. The results show the effect of the target erosion profile, process pressure, separation, and magnetron power on the current-voltage characteristics of both the substrate electrode and magnetron.