Principles and applications of hollow cathode magnetron sputtering sources

Abstract

Hollow cathode magnetron sources, also known as inverted magnetrons, sputter material from the inside surfaces of cylindrical targets. A substrate enclosed by the cathode will receive a high-rate coating flux simultaneously from all directions. This feature, along with their ease of scalability and adaptable geometry, makes hollow cathodes ideal for a variety of sputtering applications. Devices with high aspect ratios (length to diameter) are used for rapidly coating fibers and wires, which can be transported continuously along the axis. Larger diameter, lower aspect ratio cathodes can be used to uniformly coat other types of three dimensional objects without rotation. The enclosed geometry assures that most of the sputtered material either coats the substrate or is redeposited on the target, making very efficient use of the target material and reducing the need for chamber cleaning. And because of the magnetic field shape, greater than 90% target utilization is possible without the typical racetrack formation seen in planar magnetrons. This paper discusses the operating principles and characteristics of these devices as well as several typical applications.