Electric field control of plasma and macroparticles in cathodic arc deposition as a practical alternative to magnetic fields in ducts

Plasma transportation and ion losses in a cathodic are fitted with a curved magnetic macroparticle filter are studied for different magnetic field configurations. A planar Langmuir probe was used to carry out ion saturation current measurements along the axis of the duct, so that the losses of ions could be quantified. The losses of ions were found to depend sensitively on the magnetic field configuration in the prefilter region. The potential of the duct wall was measured as a function of distance to the cathode and the results were used to locate the effective anode of the discharge. The location of the effective anode was determined by the magnetic field configuration and affected the running stability of the are. The conditions which provided the best efficiency of plasma transport also gave the least stable running conditions. The use of an electric field as a macroparticle filter was studied and higher deposition rates for coatings of comparable quality were found to be deposited onto a substrate held parallel to the drift velocity of the plasma to which a negative bias was applied. (C) 1996 American Vacuum Society.