Dermot Monaghan, Patrick McCarthy, Joe Brindley, Gencoa Ltd, Liverpool, United Kingdom
Cathodic arc evaporation is widely used in physical vapor deposition due to its high ionization efficiency, excellent film adhesion, and dense coatings. However, macro-particle (droplet) formation remains a major limitation, adversely affecting coating smoothness and performance. Conventional approaches to macro-particle reduction typically rely on additional internal vacuum components such as magnetic filter coils, auxiliary power supplies, or pulsed power systems. While effective, these solutions increase system complexity, cost, and often reduce deposition rate.
We present here a novel approach employing a fast, circular rotating magnetic array operating at thousands of revolutions per minute. This has been demonstrated to produce significant improvements in coating quality via droplet defect reduction. This approach is a simpler and more robust arc-steering strategy for macro-particle reduction based on the application of external magnetic fields near the cathode surface. By controlling arc motion across the target, the local residence time at individual ignition sites is reduced, thereby limiting localized heating and cathode melting, which are key contributors to macro-particle generation.
We present a systematic study of various static magnetic field geometries and their influence on arc behaviour and coating properties during arc evaporation of TiN, TiAlN, CrN, AlCrN, ZrN, and CN coatings. Experimental results reveal the existence of a critical magnetic array rotation speed threshold required to effectively suppress macro-particle formation, with each material exhibiting a unique optimal magnetic configuration and speed. In addition, key process parameters including reactive gas pressure, arc current, and magnetic field strength are characterized to identify optimal operating conditions. The resulting coatings are evaluated using scanning electron microscopy, ball crater testing, and nano-indentation, while arc dynamics are analyzed using high-speed imaging. Hardnesses of 31 GPa for TiN and 25 GPa for CrN are achieved with low defect counts and surface roughness.
The findings demonstrate that optimized magnetic arc steering using high speed rotating external magnets provides an effective, low-complexity route to reducing macro-particle formation without compromising deposition efficiency, offering a practical alternative to more complex filtering technologies.