Reactive deposition of nitrides and oxides using a twin-cathode inverted cylindrical magnetron

Abstract

Nitrides and oxides of aluminum and other metals were reactively sputtered in a twin-cathode inverted cylindrical magnetron run with mid-frequency power. This geometry is particularly suited for coating three-dimensional objects of complex shape. However, high rate reactive sputtering in such an enclosed cathode has not been reported and presents unknown processing conditions. High rate deposition requires operation at a point that is normally unstable. For aluminum nitride films, high pumping speed was sufficient to ensure stable operation. Reactive deposition of oxides required feedback from the discharge current to control the flow of oxygen. This was successful for the relatively simple case of aluminum oxide, and the much more complicated case of titanium oxide. Films were deposited onto glass substrates under conditions of different pressure, power, and reactive gas flow. Reactive gas flows were found where good films of aluminum nitride and aluminum oxide could be deposited at high rates. Rates (relative to pure aluminum) were 32% for aluminum nitride and 26–40% for aluminum oxide. Both aluminum nitride and aluminum oxide films were insulating, non-absorbing, and adherent to the glass substrates.