Filtered ion source

#This invention relates generally to an ion source, and more specifically to a filtered ion source for use in a variety of ion applications where efficient ion transport and macroparticle filtering is desired.

#Ion sources are used in a variety of applications, from heat treatments to physical vapor deposition (“PVD”) of materials on substrates. Typically, the ion source material is consumed and this results in the transmission of undesirable chunks or droplets called macroparticles. Macroparticles are undesirable for nearly all ion source applications, especially those applications involving PVD.

#Prior art PVD techniques using an ion source incorporate a deposition or coating chamber in which a “plasma” of the coating material is produced and projected toward a substrate to be coated. Coatings applied to substrates and the shapes and materials of the substrates can vary widely, from decorative coatings on ceramic or pottery materials to circuit interconnection wiring paths on the surfaces of semiconductor chips, to wear-resistant coatings on cutting tools and bearing surfaces. Similarly, the physical nature and properties of the coating materials may vary widely, from conductive coatings to semiconductive coatings to those forming electrical insulators. Physical vapor deposition processes generally require evacuation of the deposition chamber prior to and maintenance of a negative pressure level during the deposition coating process. In an electric arc type ion source, after evacuation of the chamber, the typically solid sacrificial source material is acted upon by an electric arc that converts the solid source material into a vaporous plasma of coating material. Once converted into a plasma, a coating source material may be combined with reactive gasses or other elements within the chamber to form coating compounds and molecules prior to or during deposition thereof on substrate(s). The coating plasma typically includes atoms, molecules, ionized atoms and molecules, and agglomerates of molecules.

#The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

#FIG. 1A is a schematic cross-sectional planar view of an ion source usable with the present invention.

#FIG. 1B illustrates schematically the magnetic field lines, triggering mechanism, and electrical circuitry of the embodiment depicted in FIG. 1A.

#The embodiments described below relate to use of the present invention in a physical vapor deposition system using the cathodic arc. It is important to note that the present invention is by no means limited to deposition of materials on substrates but rather, the macroparticle filtering aspect of the present invention has several beneficial uses besides deposition. For example, efficient macroparticle filtering enables an arc ion source to function as a high intensity electron source for heating workpieces prior to coating. Additionally, this high electron density source is able to be used for excitation and ionization of vapor produced by an auxiliary evaporation source. When operating in such a mode, high intensity, low energy electron streams are capable of being produced. This heating capability may be exploited as a means for vacuum degassing components, surface annealing or other vacuum heat treatments. Thus, the present invention is by no means limited to use as a deposition system but rather any situation where efficient filtering of macroparticles from ions is beneficial can utilize the present invention.

#Furthermore, the embodiments described below all relate to deposition systems using consumable cathode materials. One of ordinary skill in the art will appreciate that the present invention is not limited by the charge assigned to the source material.

#With reference now to FIG. 1A, an embodiment of an ion source useable with the present invention will now be described. FIG. 1A is a schematic cross-sectional planar view of an apparatus for use in combination with an electric arc vapor deposition system where the vacuum chamber 26 and area 12 are illustrated schematically for purposes of simplicity. Cathodic arc vacuum chambers are well known in the art and thus the details and construction of the chamber itself will not herein be described. Workpieces are arranged in area 12 and may be mounted in a holder or fixture and rotated within area 12 to provide uniformity in coating and the availability of coating a large number of workpieces. Plasma duct 18 is capped at one end by endplate 24 and mounted to a vacuum chamber 26 which typically functions as the anode. Alternatively, the anode can be placed within area 12. Endplate 24, magnetic coil housing 16, duct 18, and pylon 20 are suitably made of a non-magnetic material such as stainless steel. The apparatus depicted in FIG. 1A uses a substantially cylindrical-shaped cathode 10 that has an evaporation surface facing away from the deposition area 12. In other words, the evaporation surface of cathode 10 faces the closed end of the ion source, which in this particular embodiment is endplate 24. During operation, the arc evaporates source material from the side of cathode 10 as well. Thus, an alternative arrangement of cathode 10 (not shown) may limit evaporation to a surface facing the wall of duct 18 as well. Inner magnetic coil 14 is located between cathode 10 and area 12. Inner magnetic coil 14 is contained within a housing 16 that also holds the cathode 10. The embodiment depicted in FIG. 1A contains an additional magnet 22 which is in opposition to inner magnet 14. As explained in greater detail below, magnets 14 and 22 are opposing electromagnets that are used to guide ions through the apparatus to the deposition area 12. Magnets 14 and 22 can also be permanent magnets. Housing 16, located between cathode 10 and deposition area 12, together with duct 18, act to prevent macroparticles from reaching deposition area 12.