Filtered cathodic arc source

Details Filtered cathodic arc source Filtered cathodic arc source

1997-11-21

2000-02-29

Anderson, Bruce C.

Radiant energy

Irradiation of objects or material

Irradiation of semiconductor devices

250398, 250396ML, H01J 3730

Patent

active

060312394

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention relates to a filtered cathodic arc source. More specifically, this invention relates to an improved filtered cathodic arc for generating a plasma beam containing positive ions for depositing a coating of the positive ions on a substrate. The invention relates to improved filtering of the plasma beam, to a method and apparatus for coating substrates using a filtered cathodic arc, to a method and apparatus for generating multi-layer coatings using a filtered cathodic arc, to ignition of the filtered cathodic arc, and to substrates having a coating of positive ions obtained using a filtered cathodic arc.
Various methods and apparatus are known in the art for obtaining a thin film or thin coating on a substrate. It is known to deposit films by physical vapour deposition techniques and chemical vapour deposition techniques; this invention relates to physical techniques. It is known to provide such coatings using magnetron sputtering, and one such method is described in U.S. Pat. No. 5,225,057. The quality of these films is open to considerable improvement. Sputtering is sometimes ion beam assisted. The purpose of the ion beam may be to clean substrate prior to coating or to promote reaction of subsequent deposited layers.
Another method of depositing thin films involves the use of positive ions generated from a cathodic arc source. The cathodic arc is a form of electrical discharge in vacuum which is sustained in metal plasma created by the arc alone and does not require the addition of an inert gas. Currents used in cathodic arc systems are typically of the order of 100 amps, at around 30 volts. A large percentage of the metal vapour generated by the arc is ionised by the discharge and a fraction of the arc current escapes as a beam of positive ions; this fraction is steered and optionally filtered to produce a coating on a distal substrate. The increased energy of these positive ions compared to the particles in previous deposition methods is thought to be a reason why arc evaporation techniques would deposit high density, high uniformity films. Deposition of thin films by filtered arc evaporation is described generally by P. J. Martin in Surface and Coatings Technology, Volumes 54/55 (1992) pages 136-142, and further reviewed in Surface Engineering, Volume 9 (1993), no. 1, pages 51-57.
Cathodic vacuum arc systems have thus been recognized as potentially a cost-effective method to produce coatings in a vacuum. However, the approaches taken do not address the requirements needed for the industrial applications of this technique. Such industrial system must be automatic, easily maintained and produce a large coating area, free of blemishes.
It has been observed in the deposition of films using cathodic arc technology that the plasma beam of positive ions and electrons produced by the arc is frequently contaminated by large, typically neutral, particles that are multi-atom clusters. These contaminating particles are commonly referred to as macroparticles and can be defined as particles visible under the optical microscope in a film deposited using cathodic arc methods. The presence of macroparticles in deposited films has precluded the use of cathodic arc techniques for obtaining optical and electronic coatings.
Much work in the art has been directed towards filtering macroparticles from the plasma beam, thereby eliminating the undesirable side effects of the presence of macroparticles in the deposited coating. GB-A-2117610 uses a baffle placed directly between the cathode and the substrate to prevent macroparticles reaching the substrate. The positive ions in the plasma beam are focused around the baffle. This has the disadvantage that there is a very low transmission of the plasma beam to the substrate. Further, some macroparticles reach the substrate by bouncing off the sides of the apparatus.
U.S. Pat. No. 5,279,723, in the name of Falabella et al, describes a cathodic ion source in which the plasma beam is filtered in an attempt to eliminate macroparticles by prov

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