Chemistry: electrical and wave energy – Processes and products – Vacuum arc discharge coating
Reexamination Certificate
2002-05-06
2004-03-16
VerSteeg, Steven H. (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Vacuum arc discharge coating
C204S298410
Reexamination Certificate
active
06706157
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to a vacuum arc plasma gun deposition system that can be used to coat relatively large substrates and that can be operated with satisfactory stability for extended periods of time.
Vacuum arc deposition is used to deposit thin films and coatings from a source electrode (usually the cathode) placed in a vacuum chamber and subjected to a high current electrical arc. In the most utilized mode, the electrical current naturally concentrates at minute areas on the cathode surface known as cathode spots, which are heated to very high temperatures. There is very intense local evaporation of the cathode material from the cathode spots. High current densities pass through the vapor emitted from the cathode spot, heating and ionizing the vapor, and thus the emitted vapor expands away from the cathode spot in the form of hypersonic plasma jets. In addition, the vacuum arc produces a spray of molten droplets or solid debris, known collectively as macroparticles. The macroparticles are generally undesirable.
In the 1870′s A. Wright (“On the production of transparent metallic films by the electrical discharge in exhausted tubes”,
Am. J. Sci. Arts
vol. 13 pp. 49-55 (1877); “On a new process for the electrical deposition of metals, and for constructing metal-covered glass specula”,
Am. J. Sci. Arts
vol. 14 pp. 169-178 (1878)) described the application of what was apparently a pulsed vacuum arc to deposit coatings on glass, and described their visual properties. Thomas Alva Edison (“Art of plating one material with another”, U.S. Pat. No. 526,147, 1894; “Process of duplicating phonograms”, U.S. Pat. No. 484, 582, 1892) taught the use of a continuous vacuum arc to produce metal coatings, and their use in the process of duplicating phonograms.
Currently, vacuum arc deposition is widely practiced, in particular to deposit diamond-like carbon, TiN, TiCN, (Ti,Al)N, ZrN and other ceramic materials on cutting and forming tools, household hardware (e.g. door knobs, plumbing fixtures), surgical instruments and implants, and jewelry. In the most common “batch coater” type of configuration, one or more cathodes are mounted in a vacuum chamber and serve as vapor plasma sources. The chamber is periodically opened to remove coated workpieces, and to mount new workpieces for coatings. At these times it is convenient to replace expended cathodes with new ones, and to clean the chamber walls and other components of accumulated coatings and debris. Typical cycle times are on the order of a few hours, during which the arc is operated for only some fraction of the time. In these systems, the coatings will generally contain some degree of macroparticle inclusions.
As taught by Aksenov et al. (
Sov. J. Plasma Phys
. Vol. 4 p. 425; Pribory I Tekhnika Eksperimenta N5 (1978) p. 1416), macroparticles can be separated from the plasma jets by bending the plasma using a magnetic field around an obstacle that occludes any direct path between the cathode and the substrates. The most common form of obstacle is the walls of a curved duct. Alternatively, as described by S. Falabella and D. M. Sanders,
J. Vac. Sci. Technol. A
vol. 10 p. 394 (1992), the duct may be formed from straight tubular sections joined at an angle. Nevertheless, some macroparticles may rebound from the duct wall and eventually bounce along the duct and reach the substrate. Several inventions (J. Storer et al.,
J. Appl. Phys
. vol. 66 p. 5245 (1989); R. P. Welty, U.S. Pat. No. 5,480,527) teach that macroparticle transmission may be reduced by corrugating the duct wall or by placing baffle plates in the duct to catch bouncing macroparticles.
Prior art vacuum arc deposition devices are well suited for laboratory studies and for batch coating operation, where there are ample opportunities to replace expended cathodes and to clean the system of accumulated debris. However, in certain applications, long-term stable operation is required. For example, in large flat glass coating plants, an alternative technology, magnetron sputtering, is widely employed, and continuous operation runs of two weeks are common. Stable operation over long periods requires maintaining an approximately constant cathode temperature, electrode geometry and duct geometry, in the face of cathode erosion on the one hand, and the accumulation of a coating on the anode and other surfaces on the other hand.
There is thus a widely recognized need for, and it would be highly advantageous to have, a vacuum arc plasma gun deposition system including mechanisms for stabilizing cathode temperature, electrode geometry and duct geometry.
SUMMARY OF THE INVENTION
It is an objective of the present invention to provide the means for stable, long duration, continuous vacuum arc deposition, by providing mechanisms for operating the cathode surface at a constant average temperature, and for maintaining approximately constant electrode and duct geometries in the face of cathode erosion and coating accumulation on other surfaces.
According to the present invention there is provided a vacuum arc plasma gun including: (a) a cathode having an active surface; (b) at least one anode; (c) a current source for causing electrical current to flow from the at least one anode to the active surface of the cathode; and (d) a mechanism for moving the cathode to keep the active surface substantially at a fixed position relative to the at least one anode while the electrical current flows.
According to the present invention there is provided a vacuum arc plasma gun including: (a) a cathode having an active surface and at least one lateral surface; (b) at least one anode; (c) a current source for causing electrical current to flow from the at least one anode to the active surface of the cathode; and (d) a mechanism for cooling the cathode while the electrical current flows, by conducting heat away from the at least one lateral surface.
According to the present invention there is provided a vacuum arc plasma gun including: (a) a cathode; (b) a plurality of anode assemblies defining a channel having a cross sectional size; (c) a current source for causing electrical current to flow from the plurality of anode assemblies to the cathode, thereby causing material to flow away from the cathode via the channel, at least a portion of the material then being deposited on the anode assemblies; and (d) for each anode assembly: a mechanism for moving the each anode assembly to keep the cross sectional size of the channel substantially constant while the material is deposited on the each anode assembly.
According to the present invention there is provided a method of coating a substrate, including the steps of: (a) providing a vacuum arc plasma gun including: (i) a cathode having an active surface, and (ii) at least one anode; (b) causing an electrical current to flow from the at least one anode to the active surface of the cathode, thereby creating a plasma that carries coating material away from the active surface of the cathode; and (c) while the electrical current flows: (i) positioning the substrate relative to the plasma so that at least a portion of the coating material is deposited on the substrate, and (ii) moving the cathode so that the active surface remains substantially in a fixed position relative to the at least one anode.
According to the present invention there is provided a method of coating a substrate, including: (a) providing a vacuum arc plasma gun including: (i) a cathode having an active surface and a lateral surface, and (ii) at least one anode; (b) causing an electrical current to flow from the at least one anode to the active surface of the cathode, thereby creating a plasma that carries coating material away from the active surface of the cathode; and (c) while the electrical current flows: (i) positioning the substrate relative to the plasma so that at least a portion of the coating material is deposited on the substrate, and (ii) removing heat from the cathode by conduction via the lateral surface.
According to the present inven
Boxman Raymond Reuven
David Yair
Goldsmith Samuel
TransArc Ltd.
VerSteeg Steven H.
LandOfFree
Vacuum arc plasma gun deposition system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vacuum arc plasma gun deposition system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vacuum arc plasma gun deposition system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3275001