Process and apparatus for reactive coating of a substrate

Process for reactively coating a substrate using a magnetron sputtering apparatus of the type comprising

• an evacuable coating chamber, respective means for introducing a process gas and a reactive gas into said chamber, a cathode which interacts with a metallic target to be sputtered, a power supply connected to said cathode, a plurality of magnets behind said target opposite said substrate, and a diaphragm anode between said target and said substrate, said diaphragm having aperture means between part of said target and said substrate to be coated, said process comprising the steps of
• positioning said magnets a distance behind said target so that the part of the target adjacent said aperture means is sputtered,
• controlling the power to the cathode and the supply of reactive gas so that said substrate is reactively coated,
• repositioning said magnets a like distance behind said target so that the parts of the target which are not adjacent said aperture means are sputtered, and
• controlling the power to the cathode and the supply of reactive gas so that said diaphragm is metallically coated.

Apparatus for reactive coating of a substrate comprising

• an evacuable coating chamber,
• means for introducing a process gas into said chamber,
• a tubular cathode having an axis and an outer cylindrical surface with a first zone closest to said substrate and a second zone outside of said first zone, said outer cylindrical surface being substantially parallel to said axis,
• a power source connected to said cathode,
• a plurality of magnets situated inside said tubular cathode,
• a target of a single metallic material in the form of a metallic coating on said outer cylindrical surface of said tubular cathode, and
• an anode between said cathode and said substrate and aligned with said first zone so that said first zone has a higher sputtering power density than said second zone, whereby
• during reactive sputtering, said anode can be coated by target material in a metallic mode from said first zone and said substrate can be coated with reacted target material from said second zone.