WO2003057939A2 - Cathode pour evaporateurs a arc electrique sous vide - Google Patents

Cathode pour evaporateurs a arc electrique sous vide Download PDF

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Publication number
WO2003057939A2
WO2003057939A2 PCT/IL2003/000033 IL0300033W WO03057939A2 WO 2003057939 A2 WO2003057939 A2 WO 2003057939A2 IL 0300033 W IL0300033 W IL 0300033W WO 03057939 A2 WO03057939 A2 WO 03057939A2
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WO
WIPO (PCT)
Prior art keywords
cathode
end portion
conically
mid
cathode apparatus
Prior art date
Application number
PCT/IL2003/000033
Other languages
English (en)
Other versions
WO2003057939A3 (fr
Inventor
Aleksander Arenshtam
Efim Bender
Nitzan Eliyahu
Original Assignee
Varco Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from IL14762702A external-priority patent/IL147627A0/xx
Priority claimed from IL15085402A external-priority patent/IL150854A0/xx
Application filed by Varco Ltd. filed Critical Varco Ltd.
Priority to AU2003209606A priority Critical patent/AU2003209606A1/en
Publication of WO2003057939A2 publication Critical patent/WO2003057939A2/fr
Publication of WO2003057939A3 publication Critical patent/WO2003057939A3/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32055—Arc discharge
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/24—Vacuum evaporation
    • C23C14/32—Vacuum evaporation by explosion; by evaporation and subsequent ionisation of the vapours, e.g. ion-plating
    • C23C14/325—Electric arc evaporation

Definitions

  • the present invention relates to a cathode for vacuum arc evaporators and evaporators employing such cathodes.
  • Cathodic vacuum arc evaporation is a physical vapor deposition (PVD) process which uses a centrally located material source.
  • the material source usually is an electrically conductive metal but sometimes it is a semiconductor.
  • the process involves a high current, low voltage electric arc that strikes the source, and vaporizes it.
  • the plasma generated is then propelled into an evacuated chamber where it subsequently deposits onto a substrate.
  • Arc vapor deposition may be used in pulsed or continuous modes with appropriate modification of the apparatus design for each mode.
  • the negative lead of a direct current (DC) or pulsed DC power supply is attached to the source (hereinafter also referred to as the "cathode") and the positive lead is attached to an anode.
  • An arc-initiating trigger at or near the same electrical potential as the anode, contacts the cathode, producing an arc.
  • the exact point, or points, where the arc touches the surface of the cathode is referred to as a cathode spot or spots.
  • the cathode spots then move away from the trigger along the cathode, vaporizing the metal source.
  • the arc progresses down the cathode toward its connection to the negative terminal of the power source.
  • the current density of the arc at a cathode spot is of the order of 10 5 to 10 7 amperes per square centimeter, with spot sizes of the order of 20 microns and with a spot lifetime often as short as 5-50 ns.
  • the intensity of the energy at the cathode spot is sufficient to boil the cathode material; the parts of the cathode where there are no cathode spots remain cold.
  • cathode material at the spot vaporizes into a plasma containing atoms, ions, electrons, and particles. Cathode spots exist for very short intervals and are then replaced by new spots in the immediate vicinity of the old ones.
  • 1345719 discusses using a coil located inside a cathode to steer the arc, the coil creating a tangential magnetic field on the surface of the cathode.
  • the field causes the cathode spots to rotate around the target providing a circular homogeneous coating.
  • Some prior art devices steer the arc by mechanically regulating a magnetic field source relative to the cathode.
  • Other prior art devices steer the arc by alternately connecting a power supply lead between the two ends of a cathode.
  • the switching mechanisms and the hardware necessary to manipulate a magnetic field source relative to the cathode are complex.
  • U.S. Pat. Nos. 4,609,584, 5,037,522, and to some degree 5,269,898 provide a magnetic field produced by an arc current flowing within the cathode.
  • the forces generated by the interaction of the magnetic field and the arc current move the arc along the length of a generally cylindrical cathode.
  • patents '522 and '584 the motion of the arc is described as tracing out a helical or spiral path along the cathode.
  • FIG. 1 A typical prior art cathode for use in a vacuum arc apparatus is shown in Fig. 1 , to which reference is now made.
  • a cylindrical cathode rod 210 is positioned in a chamber 208.
  • a vacuum pump 270 is connected to chamber 208 and evacuates the gases from within it.
  • a substrate 280 to be coated is disposed within chamber 208 at a distance and direction from cathode 210 which produces an optimum coating.
  • the main cathode body 209 of cathode 210 is constructed of an evaporable metal.
  • Cathode 210 is insulated from chamber 208 by insulator 207.
  • One end 204 of cathode 210 serves as the ignition region 298 of the cathode.
  • Ignition region 298 is in association with first end 204, and includes an ignition electrode 202, which is typically surrounded by an insulator 203.
  • An insulating member 205 is joined to the second end 299 of main cathode body 209 of cathode 210. Insulating member 205 extinguishes the discharge arc when the arc reaches second end 299. Insulating member 205 prevents the arc spots from moving off the evaporable surface of main cathode body 209. Insulating member 205 is in communication on one side with the metal mid-section 212 of cathode 210 and on the other side with current electrode 206.
  • the negative terminal of a DC or pulsed DC high current, low voltage pulsed power supply 260 is connected to current electrode 206 of cathode 210 after electrode 206 exits chamber 208, while the positive terminal of power supply 260 is connected to the exterior of chamber 208.
  • Ignition electrode 202 is positioned so as to periodically connect to the positive terminal of a high voltage, low current pulsed power supply 250, via trigger mechanism 235.
  • Trigger mechanism 235 strikes ignition electrode 202 by reciprocally moving towards and away from electrode 202, thereby initiating an arc.
  • the negative terminal of power supply 250 is connected to current electrode 206 of cathode 210 after electrode 206 exits chamber 208.
  • the current supplied by power supply 260 generates a magnetic field as it flows through cathode 210; a component of this magnetic field is parallel to the long axis of, and tangential to, cathode 210.
  • the magnetic field steers the cathode spots produced by the discharge arc from ignition region 298 in the general direction of insulating ring 205.
  • the field reduces the random motion of the cathode spots and decreases the number of multiple visits to previously eroded locations on cathode 210.
  • the uniformity of cathode erosion is increased.
  • the uniformity of metal deposition on the substrate is increased, while droplet formation, as discussed below, is decreased.
  • cathodes particularly when the cathode is a cylindrical cathode, coils may be disposed on the outside of the cylinder, coaxial with it.
  • the cathode is a hollow cylinder
  • the coils may be placed inside the hollow of the cylinder.
  • the coils when a power supply is operative, the coils function as electromagnets generating a magnetic field, which steers the arc's cathode spots along cathode 210, reducing their random motion. Again, erosion and deposition uniformity is increased while droplet formation is decreased.
  • magnetic field producing elements can be deployed in other configurations, which control and steer the cathode spots in the direction of insulator 205.
  • Cathode ignition portion 4 has an ignition electrode 1 surrounded by a ceramic bushing 2, and a thin molybdenum ring 3. Having ignition electrode 1 surrounded by bushing 2 of high thermal conductivity, which, in turn is surrounded by ring 3 fabricated of a high melting-point metal will drive the discharge arc rapidly from the discharge region to the evaporable metal portion 13 of cathode ignition portion 4 as desired for longer life when used in the pulsed mode.
  • droplets also known as macroparticles.
  • These droplets consist of molten metal ejected from the target as the target undergoes vaporization and superheating at the region of the cathode spots.
  • the droplets are typically about 0.1 to 50 microns in diameter.
  • the formation of these droplets leads to irregularities in the coating of the substrate. Even when these droplets are treated and removed from the substrate, they leave pinholes in the coating.
  • the droplets arise as a result of multiple random passes of cathode spots during a short time interval through a region of the cathode's surface. The random motion of the cathode spots causes superheating in the regions which are frequently visited. Even when methods to control and steer cathode spots are used, the problem of droplets is not completely resolved.
  • the cathode is eroded non- uniformly. Accordingly, the cathode is not used efficiently and much metal goes unused.
  • the present invention provides a cathode for use in pulsed vacuum arc evaporators which can be used for evaporating and depositing metals and semiconductors.
  • Cathodes described herein can also be used for fabricating electronic components, hardening metal surfaces, preventing corrosion in metals, and producing fullerenes and diamond-like films, as well as for many other applications.
  • the ignition region of the cathode is configured to extend the life of that region.
  • the ignition region is conically shaped, includes an insulating bushing, usually a ceramic bushing, which has a high thermal conductivity, and further includes a thin metal ring, typically a molybdenum ring around the insulating bushing, and spacing elements therebetween.
  • the mid-section of the cathode has a screw-like shape to better control and steer the arc and reduce the random motion of the cathode spots.
  • the screw-like shape keeps the cathode spots separate, preventing them from joining together at common sites.
  • the cathode has a high melting point metal ring, typically a molybdenum metal ring, positioned adjacent to a conductor electrode, the latter being connected to the negative terminal of a pulsed power supply.
  • a high melting point metal ring typically a molybdenum metal ring
  • This metal ring quenches the arc's cathode spots preventing them from leaving the cathode.
  • an apparatus for applying material by pulsed cathodic arc vapor deposition onto a substrate.
  • the apparatus includes a vessel and a means for obtaining a vacuum in the vessel. It also includes a generally cylindrical screw- shaped cathode for selectively sustaining an arc of electrical energy along the cathode.
  • the screw-shaped cathode serves as a means for steering the arc along and around the cathode, reducing the random motion of cathode spots.
  • the arc of electrical energy moving down the length of the cathode vaporizes a portion of the cathode, and the vaporized metal thereby produced subsequently deposits on a substrate positioned inside the vessel.
  • the cathode apparatus is connected to first and second pulsed power supplies.
  • the apparatus includes a main cathode body of evaporable metal, the body having first and second end portions.
  • An ignition electrode is mounted onto the first end portion of the main cathode body. The electrode generates a discharge arc which produces migrating cathode spots. The spots move generally along the main cathode body away from the first end portion.
  • the ignition electrode is connected to a first pulsed power supply, and generates the arc after being activated.
  • the second end portion of the main cathode body is in conductive association with a negative terminal of the second pulsed power supply, the second power supply providing an arc current.
  • the main cathode body further has a mid-section, integrally formed with and extending between the first and second end portions and has a generally screw-like configuration for steering the cathode spots generally from the first end portion toward the second end portion.
  • the first end portion is configured and constructed to drive the cathode spots away from the ignition electrode, toward the mid-section of the main cathode body.
  • the screw-like configuration of the mid-section is operative to cause a helical motion of the migrating cathode spots toward the second end of the main cathode body.
  • the first end portion further includes an insulating bushing surrounding the ignition electrode, which has a wide, nail-head-like end which partially covers the bushing at a predetermined spacing therefrom.
  • the bushing itself is surrounded by a first metal ring with a predetermined spacing therebetween.
  • spacing elements interposed in the two predetermined spaces which are chosen from a high conductivity material. They may be chosen from a distending material or they may be spring-like spacing elements.
  • the springlike spacing elements may be formed of molybdenum and may be, respectively, a cone- shaped spring interposed in the spacing between the insulating bushing and the nail-like head of the ignition electrode, and a cylindrical spring with a radial wave-like form interposed in the spacing between the first metal ring and the insulating bushing.
  • the insulating bushing is chosen from a material which dissipates heat rapidly and the first metal ring is chosen from a material which accelerates the movement of the cathode spots away from the first end portion.
  • the insulating bushing is chosen from a material which has a thermal conductivity at 20°C of not less than about 250 W/m.°K.
  • the first metal ring is made from a high melting point metal chosen from a group consisting of molybdenum, tungsten, osmium, rhenium and tantalum.
  • the cathode apparatus further includes a screen element coaxial with the negative terminal of the second pulsed power supply and having a shading portion extending radially, thereby serving to shade the negative terminal from material evaporated from the main cathode body and the second end portion is in association with a second metal ring positioned on the side of the mid-section distal from the first end portion.
  • the second ring serves to extinguish or quench the arc's cathode spots and to prevent the cathode spots from leaving the cathode apparatus.
  • the second metal ring includes a shield portion distal from the second end portion and extending radially therefrom, and the shading portion of the screen element and the shield portion of the second metal ring have a predetermined spacing therebetween further serving to prevent the cathode spots from leaving the cathode apparatus.
  • the shading portion of the screen element and the shield portion of the second metal ring further may be disc-like in shape with diameters greater than that of the second end portion which may be approximately equal.
  • the second metal ring is made from a high melting point metal chosen from a group consisting of molybdenum, tungsten, osmium, rhenium and tantalum.
  • the shield portion of the second metal ring is made from a preselected metallic material and the second metal ring is integrally fabricated of the spacer portion and the shield portion.
  • the first end portion is conically-shaped.
  • the conically-shaped first end portion is frustro- conically shaped.
  • the conically- shaped region forms an angle of no more than 90 degrees.
  • the conically-shaped region is a double conical region with an inner conically- shaped region forming an angle greater than 90 degrees or preferably, approximately 120 degrees, and an outer conically-shaped region forming an angle less than 90 degrees or preferably, approximately 60 degrees.
  • the conically-shaped region has a base which is integrally connected to the mid-section.
  • the conically-shaped first end portion has a base symmetrically disposed around the mid-section.
  • the mid-section is an elongated cylindrical body.
  • the elongated cylindrical body has a length to diameter ratio of between about 1 :1 and about 50:1.
  • the diameter of the mid-section is equal to the diameter of the base of the conically shaped region.
  • the mid-section has a tapered shaped.
  • the tapered shaped mid-section is integrally joined to the base of a first end portion having a conical shape.
  • the main cathode body is a solid body.
  • the mid- section is composed of a plurality of evaporable metal cylindrical bodies.
  • each of the plurality of metal cylindrical bodies is formed of a different evaporable metal.
  • the screw-like mid-section has threads having rounded edges.
  • a preferred embodiment of a first end portion construction for a cathode apparatus for use with a pulsed vacuum arc evaporator has a main cathode body formed of an evaporable metal.
  • the main cathode body has first and second end portions with a mid- section integrally formed with, and extending between, the end portions.
  • the first end portion construction includes an ignition electrode with a wide, nail-head-like end for generating a discharge arc.
  • the arc produces migrating cathode spots which move generally along the cathode away from the first end portion.
  • the ignition electrode generates the arc after being activated by a pulsed power supply to which it is connected.
  • the first end portion construction also includes an insulating bushing surrounding the ignition electrode and partially covered by and with a predetermined spacing between it and the nail-head-like end thereof, with the insulating bushing being chosen from material which rapidly dissipates heat.
  • the construction also includes a metal ring surrounding the insulating bushing with a predetermined spacing therebetween, the ring chosen from a material which drives the discharge arc away from the first end portion, and spacing elements chosen from a high conductivity material interposed in the two predetermined spaces.
  • the spacing elements may be chosen from a distending material or they may be spring-like spacing elements.
  • the spring-like spacing elements may be formed of molybdenum and may be, respectively, a cone-shaped spring interposed in the spacing between the insulating bushing and the naillike head of the ignition electrode, and a cylindrical spring with a radial wave-like form interposed in the spacing between the first metal ring and the insulating bushing.
  • the ignition electrode, insulating bushing, spacing elements, and metal ring are positioned in the conically-shaped first end portion of the main cathode body.
  • the mid-section has a generally screw-shaped cylindrical configuration.
  • the generally screw-shaped cylindrical main cathode body is in communication with a molybdenum ring at the second end portion, the molybdenum ring extinguishing or quenching the arc's cathode spots.
  • the molybdenum ring includes a shield portion distal from the second end portion and extending radially therefrom, the shield portion of the molybdenum ring being a predetermined spacing from a screen element having a shading portion extending radially therefrom and further serving to prevent the cathode spots from leaving the cathode apparatus.
  • the shading portion of the screen element and the shield portion of the second metal ring further may be disc-like in shape with diameters greater than that of the second end portion which may be approximately equal.
  • the second ring further includes a spacer portion with a diameter less than that of the shield portion, coaxial with the mid-section and extending from the shield portion proximally towards the first end portion.
  • the insulating bushing has a thermal conductivity at 20°C of not less than about 250 W/m.°K. In another preferred embodiment of the first end portion construction, the insulating bushing is a ceramic bushing.
  • the conically-shaped first end portion forms an angle of no more than 90 degrees.
  • the conically-shaped first end portion is a double conical region with an inner conically-shaped region forming an angle greater than 90 degrees or preferably, approximately 120 degrees, and an outer conically-shaped region forming an angle less than 90 degrees or preferably, approximately 60 degrees.
  • the conically-shaped first end portion has a frustro-conical configuration.
  • the distance between the outer side portion of the nail-head-like end of the ignition electrode and the outer radius of the insulating bushing is between about 0.5 to about 1 mm.
  • the metal ring is made of a high melting point metal chosen from a group consisting of molybdenum, tungsten, osmium, rhenium and tantalum.
  • a cathode apparatus for use in a pulsed vacuum arc evaporator.
  • the cathode apparatus includes a main cathode body formed of at least one evaporable metal.
  • the main cathode body further includes two end portions. There is a conically-shaped first end portion having an ignition electrode with a wide, nail-head-like end for producing a discharge arc. The arc generates cathode spots which migrate on the cathode.
  • the ignition electrode is surrounded by an insulating bushing which is partially covered by the nail-head-like end of the ignition electrode at a predetermined spacing therefrom, and the bushing is further surrounded by a first metal ring with a predetermined spacing therebetween.
  • spacing elements interposed in the two predetermined spaces which are chosen from a high conductivity material. They may be chosen from a distending material or they may be springlike spacing elements.
  • the spring-like spacing elements may be formed of molybdenum and may be, respectively, a cone-shaped spring interposed in the spacing between the insulating bushing and the nail-like head of the ignition electrode, and a cylindrical spring with a radial wave-like form interposed in the spacing between the first metal ring and the insulating bushing.
  • the second end portion is in association with a second metal ring which quenches the arc.
  • the ignition electrode generates the arc after being activated by a first pulsed power supply to which it is connected.
  • the cathode apparatus also has a mid-section which lies between the two end portions. The mid-section has a generally screw-like shape steering the cathode spots in the general direction of the second end portion and is integrally joined to a base of the conically-shaped first end portion.
  • the apparatus further includes a current electrode in communication with the negative terminal of a second pulsed power supply and the second metal ring. The positive terminal of the second power supply is connected to an evacuated chamber of the evaporator.
  • the configuration and construction of the conically-shaped first end portion drives the cathode spots away from the ignition electrode and toward the mid-section of the cathode.
  • the screw-like configuration of the mid-section introduces directed helical motion of the migrating cathode spots toward the second ring.
  • the cathode apparatus further includes a screen element coaxial with the negative terminal of the second pulsed power supply and having a shading portion extending radially, thereby serving to shade the negative terminal from material evaporated from the main cathode body.
  • the second metal ring includes a shield portion distal from the second end portion and extending radially therefrom, and the shading portion of the screen element and the shield portion of the second metal ring have a predetermined spacing therebetween further serving to prevent the cathode spots from leaving the cathode apparatus.
  • the shading portion of the screen element and the shield portion of the second metal ring further may be disc-like in shape with diameters greater than that of the second end portion which may be approximately equal.
  • the second ring further includes a spacer portion with a diameter less than that of the shield portion, coaxial with the mid-section and extending from the shield portion proximally towards the first end portion.
  • the mid-section is symmetrically disposed around the base of the conically-shaped first end portion.
  • the cathode apparatus's mid-section is an elongated cylindrical body.
  • the elongated cylindrical body has a length to diameter ratio of between about 1 :1 and about 50:1.
  • the diameter of the elongated cylindrical body is equal to the diameter of the base of the conically-shaped first end portion.
  • the mid-section is a tapered body.
  • the main cathode body is a solid body.
  • the insulating bushing has a thermal conductivity at 20°C of not less than about 250 W/m.°K.
  • the insulating bushing is a ceramic bushing.
  • the distance between the outer side portion of the nail-head-like end of the ignition electrode and the outer radius of the insulating bushing is between about 0.5 to about 1 mm.
  • the conically-shaped first end portion forms an angle of no more than 90 degrees.
  • the conically-shaped first end portion is a double conical region with an inner conically-shaped region forming an angle greater than 90 degrees or preferably, approximately 120 degrees, and an outer conically-shaped region forming an angle less than 90 degrees or preferably, approximately 60 degrees.
  • the mid-section is comprised of a plurality of metal cylindrical bodies.
  • each of the plurality of metal cylindrical bodies is formed from a different metal.
  • the screw-like mid- section has threads having rounded edges.
  • the conically-shaped first end portion is a frustro-conically-shaped first end portion.
  • the first and second metal rings are made of high melting point metals chosen from a group consisting of molybdenum, tungsten, osmium, rhenium and tantalum.
  • the shield portion of the second ring is made from a preselected metallic material and the second metal ring is integrally fabricated of the spacer portion and the shield portion.
  • a pulsed vacuum arc evaporator for depositing drop-free metal coatings.
  • the evaporator includes a chamber for containing a substrate. The chamber is connected to a means for generating a vacuum.
  • the evaporator also includes a cathode positioned in the chamber.
  • the cathode includes a main cathode body formed of at least one evaporable metal.
  • the main cathode body also includes two end portions. The first end portion is conically-shaped having an ignition electrode with a wide, nail-head-like end for producing a discharge arc which generates cathode spots, the latter migrating on the cathode.
  • the ignition electrode is surrounded by an insulating bushing, which is partially covered by and with a predetermined spacing between it and the nail-head-like end of the ignition electrode.
  • the bushing is further surrounded by a first metal ring at a predetermined spacing therefrom.
  • spacing elements chosen from a high conductivity material interposed in the two predetermined spaces.
  • the spacing elements may be chosen from a distending material or they may be spring-like spacing elements.
  • the spring-like spacing elements may be formed of molybdenum and may be, respectively, a cone-shaped spring interposed in the spacing between the insulating bushing and the nail-like head of the ignition electrode, and a cylindrical spring with a radial wave-like form interposed in the spacing between the first metal ring and the insulating bushing.
  • the second end portion is in association with a second metal ring which quenches the arc.
  • the ignition electrode generates the arc after being activated by a first pulsed power to which it is attached.
  • the cathode also includes a mid- section which lies between the two end portions.
  • the mid-section has a generally screw-like shape which steers the cathode spots in the general direction of the second end portion.
  • the mid-section is integrally joined to a base of the conically-shaped first end portion.
  • the cathode also includes a current electrode in communication with the second metallic ring and with the negative terminal of a second pulsed power supply. The positive terminal of the second power supply is connected to the chamber.
  • the configuration and construction of the conically-shaped first end portion drives the cathode spots away from the ignition electrode and toward the mid-section of the cathode.
  • the screw-like configuration of the mid-section introduces directed helical motion of the migrating cathode spots toward the second ring.
  • the evaporator further includes a screen element coaxial with the negative terminal of the second pulsed power supply and having a shading portion extending radially, thereby serving to shade the negative terminal from material evaporated from the main cathode body.
  • the second metal ring includes a shield portion distal from the second end portion and extending radially therefrom, and the shading portion of the screen element and the shield portion of the second metal ring have a predetermined spacing therebetween further serving to prevent the cathode spots from leaving the cathode apparatus.
  • the shading portion of the screen element and the shield portion of the second metal ring further may be disc-like in shape with diameters greater than that of the second end portion which may be approximately equal.
  • the second ring further includes a spacer portion with a diameter less than that of the shield portion, coaxial with the mid-section and extending from the shield portion proximally towards the first end portion.
  • the chamber has an interior surface, the surface serving as the substrate.
  • the cathode's mid-section is a generally elongated cylindrical body.
  • the elongated cylindrical body is integrally joined to the base of the conically-shaped first end portion.
  • the elongated cylindrical body has a length to diameter ratio of between about 1 :1 and about 50:1.
  • the diameter of the cathode's mid- section is equal to the diameter of the base of the conically-shaped first end portion.
  • the cathode's mid-section is a tapered body.
  • the tapered body is integrally joined to the base of the conically-shaped first end portion.
  • the main cathode body is a solid body.
  • the insulating bushing has a thermal conductivity at 20°C of not less than about 250 W/m.°K. In another embodiment of the evaporator, the insulating bushing is a ceramic bushing.
  • the cathode's conically-shaped first end portion forms an angle of no more than 90 degrees.
  • the conically-shaped first end portion is a double conical region with an inner conically-shaped region forming an angle greater than 90 degrees or preferably, approximately 120 degrees, and an outer conically-shaped region forming an angle less than 90 degrees or preferably, approximately 60 degrees.
  • the distance between the outer side portion of the nail-head-like end of the cathode's ignition electrode and the outer radius of the insulating bushing is between about 0.5 to about 1 mm.
  • the cathode's main cathode body is composed of a plurality of metal cylindrical bodies.
  • each of the metal cylindrical bodies in the plurality of metal cylindrical bodies is formed from a different metal.
  • the screw-like mid-section has threads having rounded edges.
  • the conically-shaped first end portion is a frustro-conically-shaped first end portion.
  • the cathode's first and second metal rings are made of high melting point metals chosen from a group consisting of molybdenum, tungsten, osmium, rhenium and tantalum.
  • the shield portion of the second ring is made from a preselected metallic material and the second metal ring is integrally fabricated of the spacer portion and the shield portion.
  • the cathode apparatus includes a main cathode body formed of an evaporable metal.
  • the main cathode body has first and second end portions with a mid-section integrally formed with , and extending between, the two end portions. It also includes an ignition electrode positioned at the first end portion; the ignition electrode generates a discharge arc which produces migrating cathode spots which move along the main cathode body generally away from the first end portion and toward the second end portion.
  • the ignition electrode generates the arc after being activated by a pulsed power supply to which it is connected.
  • the cathode apparatus also includes a second end portion metal ring, the ring being disposed on the second end portion of the main cathode body and in association with the mid-section.
  • the ring quenches the discharge arc, thereby preventing the cathode spots from leaving the cathode apparatus.
  • the second end portion of the main cathode body is in conductive association with the negative electrode of a second pulsed power supply which provides an arc current.
  • the first end portion of the cathode apparatus further includes an insulating bushing surrounding the ignition electrode, which has a wide, nail-head-like end which partially covers the bushing at a predetermined spacing there.
  • the bushing itself is surrounded by a first end portion metal ring with a predetermined spacing therebetween.
  • spacing elements interposed in the two predetermined spaces which are chosen from a high conductivity material. They may be chosen from a distending material or they may be springlike spacing elements.
  • the spring-like spacing elements may be formed of molybdenum and may be, respectively, a cone-shaped spring interposed in the spacing between the insulating bushing and the nail-like head of the ignition electrode, and a cylindrical spring with a radial wave-like form interposed in the spacing between the first metal ring and the insulating bushing.
  • the insulating ring is chosen from material which rapidly dissipates heat.
  • the first end portion metal ring is chosen from material which accelerates the movement of the cathode spots away from the first end portion.
  • the insulating bushing has a thermal conductivity at 20°C of not less than about 250 W/m.°K.
  • the first end portion metal ring is made from a high melting point metal chosen from a group consisting of molybdenum, tungsten, osmium, rhenium and tantalum.
  • the second end portion metal ring is made from a metal chosen from a group consisting of molybdenum, tungsten, osmium, rhenium and tantalum.
  • the cathode apparatus further includes a screen element coaxial with the negative terminal of the second pulsed power supply and having a shading portion extending radially, the screen element serving to shade the negative terminal from material evaporated from the main cathode body.
  • the second end portion metal ring includes a shield portion distal from the second end portion and extending radially therefrom, the shading portion of the screen element and the shield portion of the second end portion metal ring having a predetermined spacing therebetween further serving to prevent the cathode spots from leaving the cathode apparatus.
  • the shading portion of the screen element and the shield portion of the second metal ring further may be disc-like in shape with diameters greater than that of the second end portion which may be approximately equal.
  • the second ring further includes a spacer portion with a diameter less than that of the shield portion, coaxial with the mid-section and extending from the shield portion proximally towards the first end portion.
  • the shield portion of the second metal ring is made from a preselected metallic material and the second metal ring is integrally fabricated of the spacer portion and the shield portion.
  • the first end portion is conically-shaped.
  • the conically-shaped first end portion is a frustro- conically-shaped first end portion.
  • the conically-shaped first end portion forms an angle of no more than 90 degrees.
  • the conically-shaped first end portion is a double conical region with an inner conically-shaped region forming an angle greater than 90 degrees or preferably, approximately 120 degrees, and an outer conically-shaped region forming an angle less than 90 degrees or preferably, approximately 60 degrees.
  • the conically-shaped first end portion has a base which is integrally connected to the mid-section.
  • the conically-shaped first end portion has a base symmetrically disposed around the mid-section.
  • the diameter of the mid-section is equal to the diameter of the base of the conically shaped region.
  • the mid- section is an elongated cylindrical body.
  • the elongated cylindrical body has a length to diameter ratio of between about 1 :1 and about 50:1.
  • the mid-section has a tapered shaped.
  • the tapered shaped mid-section is integrally joined to the base of the first end portion, the first end portion having a conical shape.
  • the main cathode body is a solid body.
  • the main cathode body has a generally screw-shaped cylindrical configuration.
  • the screw-like main cathode body has threads having rounded edges.
  • the mid-section has a generally screw-shaped configuration.
  • the screw-like mid-section has threads having rounded edges.
  • Fig. 1 is a schematic lateral sectional view of a cathode and evaporator constructed in accordance with prior art
  • Figs. 2A and 2B are a schematic lateral sectional views of two cathodes and evaporators constructed in accordance with two preferred embodiments of the present invention
  • Fig. 3A is an expanded schematic lateral sectional view of the conical first end portion of a cathode constructed in accordance with a preferred embodiment of the present invention
  • Figs. 3B, 3C, and 3D are schematic lateral sectional views of the conical first end portion of cathodes constructed in accordance with a preferred embodiment of the present invention, showing alternative embodiments for mounting the ignition end;
  • Figs. 4A and 4B are graphical representations of the pulses supplied by the pulsed arc power supply and the high voltage power supply, respectively, used in the evaporator shown in Fig 2A;
  • Fig. 5 is a schematic lateral sectional view of a partly eroded cathode constructed and operative as in the preferred embodiment shown Fig. 2B;
  • Fig. 6 is a schematic lateral sectional view of a multi-elemental cylindrical cathode constructed in accordance with another preferred embodiment of the present invention.
  • Fig. 7 is a schematic lateral sectional view of a cathode and evaporator constructed in accordance with yet another embodiment of the present invention.
  • Fig. 8 is a schematic lateral sectional view of a cathode and evaporator constructed in accordance with an alternative embodiment of the present invention for a high evaporation rate application.
  • Cathode vacuum arc evaporators are known.
  • the metal cathodes currently used with such evaporators have several problems. They often produce droplets that interfere with coating uniformity, and when used in the pulse mode, cathode lifetime is short. Moreover, they usually erode unevenly and their coating depositions are not uniform even when cathode spot steering methods are used. Applicant has realized that arc steering, and hence erosion and deposition uniformity, can be enhanced by using a screw-like configuration over a major portion of the cathode's length.
  • a cathode constructed and operative according to the present invention and an evaporator using such a cathode provide a simple design, requiring no auxiliary equipment, such as magnetic coils or cooling equipment.
  • Applicant has further realized that constructing the ignition region, at the first end portion of the cathode, so as to have a generally conical shape, an insulating bushing with a high thermal conductivity, and a high melting point metal adjacent to the insulating bushing drives the discharge arc rapidly from the ignition region.
  • This construction extends the region's working life when used in the pulsed mode so long as provision is made to ensure dimensional stability even under thermal cycling.
  • Applicant has also realized that a high-melting point metal positioned at the second end portion of the cathode, in a suitable geometry, quenches the discharge arc, preventing it from leaping off the cathode.
  • a cathode and an evaporator constructed and operative according to the present invention are illustrated.
  • the cathode generally referenced 10, is shown positioned in a vacuum chamber 8 with a substrate (not shown) being coated by vapors emitted from cathode 10.
  • the substrate is usually positioned within chamber 8.
  • the wall of chamber 8 itself can serve as the substrate, as in the case where the inside of vacuum or pressurized containers are being coated.
  • Fig. 2A shows a solid, generally cylindrical cathode 10 with a first end or ignition portion 4 containing an ignition electrode 1 surrounded by a ceramic bushing 2.
  • Ignition electrode 1 is connected to the positive terminal of a pulsed high voltage power supply 50 positioned outside vacuum chamber 8.
  • the negative terminal of power supply 50 is connected to a conductor electrode 6 of cathode 10 which extends outside of chamber 8.
  • the positive terminal of power source 50 enters chamber 8 via a conductor lead 90 positioned within insulator block 95.
  • a current is supplied periodically by high voltage power supply 50 with the current having a pulse duration of between about 0.1-10.0 msec, preferably about 0.5-2.0 msec.
  • pulsed power supply 50 operates at a voltage of about 400-1000 V, preferably about 500-700 V, and provides currents of about 40-300 A, preferably about 50-70 A.
  • Ceramic bushing 2 is constructed from any of a number of ceramic materials having a high thermal conductivity.
  • the thermal conductivity of bushing 2 is not less than 250 W/m.°K at 20° C.
  • a typical ceramic material that may be used is BeO. While bushing 2 is most often constructed of a ceramic material, it should be readily apparent to one skilled in the art that any insulating materials possessing the required high thermal conductivity as recited above also may be used.
  • Ceramic bushing 2 is fitted inside a thin molybdenum (Mo) ring 3, the latter being tightly held between bushing 2 and the evaporable metal portion 13 of first end portion 4 of main cathode body 11.
  • Main cathode body 11 is formed of an evaporable metal some of which is vaporized and ionized and then deposited on a substrate (not shown).
  • Ignition electrode 1 , ceramic bushing 2, molybdenum ring 3 and a small portion of conically-shaped evaporable metal form the conical first end portion 4, often a frustro-conical end, of main cathode body 11.
  • the evaporable metal used to form main cathode body 11 of cathode 10 can be fabricated from any conductive evaporable metal, for example Ti, Cu, Al, Zr, Cr and Mn. It should be readily apparent to one skilled in the art that many other metals can be used.
  • the evaporable metal can also be made from conductive alloys, such as alloys of Ti, Al, Cu and Fe, among others. Additionally, it may be made of carbon or evaporable semiconductor materials.
  • Electrode 1 of ignition region 4 has a wide end 25 like the head of a nail overlaping part of ceramic bushing 2, which is surrounded by molybdenum ring 3.
  • ignition region 4 is fabricated with spaces 103 and 104 between ring 3 and bushing 2 and between the covered front of bushing 2 and nail-head-like end 25 of electrode 1 , respectively.
  • Spaces 103 and 104 are preferably of a width in the range of 0.1 to 0.3 mm and have a cylindrical spring part 105, preferably with a radial wave-like form, and a conical spring part 106, respectively, interposed therein to maintain dimensional stability and thermal and, where relevant, electrical contact between the parts of ignition region 4 of the cathode.
  • Spring parts 105 and 106 also serve to prevent cathode spots from entering spaces 103 and 104.
  • spaces 103 and 104 may be filled by any distending material that will maintain dimensional stability having suitable conductivity.
  • the radial distance between the outer edge of nail-head-like end 25 of electrode 1 and the outer edge of bushing 2 is typically in the range of 0.5 to 1.0 mm.
  • FIGS 3B, 3C, and 3D show alternative embodiments for the required mounting.
  • Figure 3B shows a threaded channel 33 to accommodate set screw 34 to lock into ring 3, which preferably is fabricated with a groove 35 to provide a firm fitting therewith.
  • channel 33 takes a thin, chisel-like tool to deform channel end 36 into ring 3, thereby locking ignition end 4 in place.
  • Figure 3D shows ignition end 4 as a separate subassembly that screws via threads 17 into the end of the main evaporable body 13 of the cathode.
  • the conical end 18 of the evaporable cathode is separate from the main evaporable body 13 thereof; and ignition portion 4 thereof is fixed therein via insulator 19 and threaded nut 20.
  • the metal of main cathode body 11 being evaporated is configured as a generally elongated metal cylinder or rod, with the ratio of the rod's length to its diameter typically being between about 1 :1 and about 50:1.
  • the terms metal cylinder or metal rod may be used interchangeably with main cathode body 11.
  • Ignition electrode 1 described above is fitted into the first end portion 4 of cathode 10 while a ring and shield 5, typically and herein described as a molybdenum ring 5, is joined to the second end portion 14 of main cathode body 11.
  • Molybdenum ring 5 acts as an arc quencher, or extinguisher, preventing migrating cathode spots from leaving cathode 10 and reaching conductor electrode 6 as described below.
  • the arc quenching function of ring 5 requires shield portion 114 to prevent cathode spots from reaching the boundary between ring 5 and conductor electrode 6, which, because of the large critical current of ring 5, would greatly delay the cathode spots from reaching electrode 6, thereby preventing the desired arc quenching from occurring.
  • Shield portion 114 together with screen element 116, also prevent evaporated material from evaporable cathode body 13 from coating the boundary between ring 5 and conductor electrode 6 and input insulator 7, which would also interfere with arc quenching.
  • ring 5 may be a simple ring (not shown), without shield portion 114, but with screen element 116 still serving to prevent evaporated material from evaporable cathode body 13 from coating conductor electrode 6 and input insulator 7.
  • the width of ring 5 is 5 mm or more.
  • Molybdenum ring 5 is in electrically conductive association with conductor electrode 6. Any method which ensures adequate electrical contact can be used to join molybdenum ring 5 to second end portion 14 of main cathode body 11. Typically, welding is used.
  • any high melting point metal may be used as well.
  • Other metals which may be used are tungsten, tantalum, rhenium and osmium.
  • molybdenum is most preferable because of its less reactive surface.
  • High melting point metals with reactive surfaces are generally not effective as arc quenchers.
  • shield portion 114 thereof need not be, since its function is to shade conductor electrode 6 and input insulator 7 from evaporated material from cathode body 13.
  • an integral fabrication of molybdenum ring 5 with shield portion 114 made of some other metal is also included in the current invention.
  • cathode assembly 310 constructed and operative in accordance with an alternative embodiment of the present invention, similar in most of its features to cathode 10 shown in Figure 2A.
  • the quenching ring 5 of cathode assembly 310 only has a shield portion 114, with no distinct ring or spacer portion as in cathode 10 of Figure 2A. It is worth noting that is this case, the shield portion must be made of molybdenum or some suitable metal as discussed above, since the shield must als provide the quenching function.
  • the present embodiment is suitable for applications wherein the evaporation chamber 8 is of large diameter, therefore requiring a large shield that is closer to mid-section 9 of cathode body 11 to prevent cathode spots from reaching conductor electrode 6 and input insulator 7.
  • the design shown in Figure 2A with a ring or spacer 5 and an additional spacer portion 114 is suitable.
  • An insulating ring or block 7, allows conductor electrode 6 to be connected to the negative terminal of a DC arc power supply 60 located outside chamber 8.
  • the positive terminal of arc power supply 60 is connected to the exterior of chamber 8.
  • Power supply 60 operates at about 25-60 V and provides high currents.
  • the currents supplied by power supply 60 are typically about 50-3000 A, preferably about 100-500 A.
  • mid-section 9 of main cathode body 11 - mid-section 9 comprising the major portion of body 11 - is formed as a screw, with the threads of the screw having rounded edges.
  • cathode body 11 particularly screw-like mid-section 9, is truncated for ease of presentation and the full screw-like section 9 of main cathode body 11 is not shown.
  • the height, h, between the bottom of furrow f and the top of thread t of screw-like mid-section 9 of main cathode body 11 is typically approximately equal to half the distance s between adjacent threads t.
  • thread height h is about 5 mm.
  • a solid main cathode body 11 with a screw-like configuration such as the one shown in Fig. 2A can be constructed in any number of ways. Without being limiting and being exemplary only, the screw-like mid-section 9 of main cathode body 11 may be constructed by casting molten metal in a screw-shaped mold, by using appropriate chemical or physical etching techniques or by appropriate metal machining.
  • Fig. 2A does not show the placement of the substrate within chamber 8.
  • substrates having cylindrical symmetry are used. These can be positioned coaxially around cathode 10 or in any other way which exploits the cylindrical symmetry of the cathode. However, even substrates of other symmetries can be used if properly disposed around the cathode.
  • the substrate being coated can be attached to the negative terminal of one of power supplies 50 or 60, or a third power supply (not shown), thereby accelerating the evaporated metal ions generated from cathode 10 toward the substrate.
  • conical first end portion 4 operates as follows. Before ignition, the exposed end of ceramic bushing 2 is coated with a conductive film, such as a graphite, titanium or copper film. When a current pulse is received from high voltage power source 50 (Fig. 2A) by ignition electrode 1 , ignition occurs and a spark is produced. The conducting film on ceramic bushing 2 then breaks down because of thermally induced stresses within the ceramic bushing which results from ignition, and cathode spots begin to form on molybdenum ring 3. These spots are quickly driven in the direction of mid-section 9 of main cathode body 11 (Fig. 2A).
  • a conductive film such as a graphite, titanium or copper film.
  • ring 3 is made of molybdenum, as with the case of ring 5, any high melting point metal can be used as well.
  • Other metals which may be used are tungsten, tantalum, rhenium and osmium, but molybdenum is the most preferable metal because of its less reactive surface.
  • Bushing 2 does not readily crack or otherwise degrade even at the temperatures generated by the cathode spots because the high thermal conductivity of bushing 2 dissipates heat rapidly. Furthermore, as a result of the cathode spots very quickly moving to, and then abandoning, molybdenum ring 3, the conical first end portion 4 of cathode 10 is not readily worn out. Additionally, the conical, often frustro-conical, shape of the cathode's first end portion 4 accelerates the movement of the cathode spots onto the cathode's main section, its screw-like mid-section 9. Typically, the conical region makes an angle, ⁇ , of 90° or less; preferably, the angle should be as close to 90° as practicable.
  • ignition end portion 4 of the cathode shown in Figure 3A is a double cone with a first segment 107 of approximately 120° and a second segment 108 of approximately 60°.
  • a small angle is required to facilitate the transition of the cathode spots from the ignition end 4 of the cathode to the evaporation portion 13.
  • the beam spots will quickly progress from the large angle segment 107, which provides higher current that is less stable and sustainable to the smaller angle segment 108 which provides a lesser, but more stable current. The result is more current with much less cost in ignition tip lifetime.
  • Figs. 4A and 4B show typical timing and magnitude of the pulses provided by power sources 50 and 60 respectively, and the typical relationship between the two pulses.
  • the pulse that is provided by high voltage power source 50 triggering ignition electrode 1 is shown in Fig. 4B; the arc pulse provided by arc pulse power supply 60 which generates an arc steering magnetic field is shown in Fig. 4A.
  • the stepped form shown corresponds to emission stimulated by the two power sources 50 and 60 operating in sequence as described above. It is particularly suited for the double cone cathode detailed in Figure 3A, though it can also be beneficially applied with a single cone cathode of the sort shown in cathode assembly 10 in Figure 2A.
  • molybdenum ring 5 with shield portion 114 operates as an arc extinguisher or quencher, preventing the cathode spots from jumping off the cathode's surface.
  • insulators such as boron nitride and alumina (AI 2 O 3 ), are used to perform this function.
  • insulator quenchers have a tendency to crack, or otherwise degrade, as a result of the high temperatures produced at cathode spots.
  • ring 5 is first coated by evaporated metal generated by cathode spots located upstream of ring 5.
  • cathode spots When cathode spots reach ring 5, the condensed metal film is vaporized again, re-exposing the underlying Mo. Because of molybdenum's high boiling point, it does not vaporize and it quenches or extinguishes the arc.
  • ring 5 In order for ring 5 to function as a quencher, it must first be coated by condensed vaporized metal, This metal, which is then re-vaporized, is required to "stop" the arc long enough for quenching by ring 5 to occur.
  • shield portion 1 14 is readily coated because it faces the emission region, but does not allow coating to occur on its backside or on conductor electrode 6. This is also true of the alternative configurations of ring 5, shield portion 114, and screen element 116 discussed hereinabove.
  • a new pulse is initiated at conical first end portion 4 by another current pulse from high voltage power supply 50 and the arc process described above is repeated.
  • the time between current pulses sent from high voltage power supply 50 is, therefore, generally equal to the time required for the cathode spots produced by an ignition to migrate from conical first end portion 4 of cathode 10 to molybdenum ring 5.
  • the present cathode 10 configuration having a substantially screw-like mid-section 9 provides a further directional component to the general direction produced by the internally generated magnetic field.
  • This additional directional component an additional spiral one, further reduces the randomness in cathode spot motion. Understanding the theoretical basis of the effect is problematic. What can readily be noted is that the electric field in mid-section
  • cathode 10 is eroded in a more uniform fashion than in prior art and cathode lifetime is extended. Similarly, droplet formation is reduced making coating more uniform. Additionally, since cathode 10 operates without an external coil or other electromagnetic component, nothing obstructs the ejected ions from reaching the substrate. As a result, the metal cloud evaporated and ionized from main cathode body 11 and the resulting coating deposited on the substrate is more uniform. What is particularly interesting is the finding that erosion of the screw-like cathode produces a substantially constant profile during operation of the cathode. That is, the height h between the top of threads t and the bottom of furrow f remains substantially constant during use. This can best be seen in Fig.
  • FIG. 5 a schematic lateral cross-sectional view of a partially eroded cylinder, referred to generally as 410, is illustrated.
  • the profile of the eroded cylinder 410 of Fig. 5 is seen to be essentially the same as the profile of the original cylinder shown in Fig. 2B. It is thought that this constant profile is a result of electric and magnetic field interactions and the angle ⁇ discussed above. It is also posited that possibly the path of cathode spot movement alternates between furrows and threads, first moving along the bottom of furrows f and then along the tops of threads t.
  • FIG. 6 a schematic lateral sectional view of a compound cathode, referred to generally as 510, constructed and operative according to a further alternative embodiment of the present invention is illustrated.
  • Cathode 510 is composed of three different metal cylinders 311 , 411 and 511 , which permit the formation of composite coatings. The length of each metal cylinder determines the percentage of each metal in the coating.
  • cathode 510 in Fig. 6 has been presented in truncated form for ease of presentation. While in Fig. 6 only cylinder 411 appears to have a screw-like configuration, it is readily apparent that all or any combination of the three metal cylinders can be substantially screw-like.
  • cathode 510 is similar to cathode 10 in Fig. 2B.
  • Fig. 7 a schematic lateral sectional view of a tapered or conical cathode, referred to generally as 610, and evaporator constructed and operative according to another embodiment of the present invention is illustrated.
  • Tapered cathode 610 can be viewed as being an enlargement of conical first end portion 4 of cathode 10 shown in Fig. 2B, the tapered or conical configuration extending through main cathode body 611 of cathode 610.
  • main cathode body 611 particularly screw-like mid-section 609 of tapered cathode 610, is shown in truncated form for ease of presentation.
  • tapeered cathode 610 includes an ignition electrode 1 , a ceramic bushing 2, a molybdenum ring 3, spacers (not shown), a screw-like tapered or conical metal mid-section 609, a molybdenum shield 5, a screen element 116, a current electrode 6, and an insulator 7.
  • Tapered cathode 610 is positioned in an evacuated chamber 8 with a substrate 80 positioned opposite the conical first end portion of cathode 610. Power sources such as those shown in Fig. 2B, while present, are not shown in Fig. 7.
  • Tapered cathode 610 is constructed of materials similar to, and operates in a fashion analogous to cylindrical cathode 10 discussed in conjunction with Figs. 2A-6 above and accordingly, will not be described here.
  • the cathode spots proceed from ignition electrode 1 and migrate to molybdenum shield 5.
  • the trajectory traced out by the mobile cathode spots is essentially helical, but with a non-constant, ever increasing radius, as the spots move in the direction of molybdenum shield 5.
  • FIG 810 there is shown a cathode assembly, referred to generally as 810, constructed and operative in accordance with a further alternative embodiment of the present invention, similar in most of its features to cathode 10 shown in Figure 2B with the addition of cooling finger assembly 117 in its core.
  • the design requires no cooling equipment, in some applications where the evaporation rate from the cathode is high enough, the cathode current heats the assembly faster than the evaporation and other paths for heat dissipation can remove excess thermal energy. Therefore, some cooling mechanism, such as cooling finger assembly 117, is required to prevent overheating.
  • an evaporation rate of less than 10 microg rams/sec for cathodes in accordance with the present invention will not require any additional cooling, as stated hereinabove, while an evaporation rate greater than 1 milligram/sec will require additional cooling, even for cathodes in accordance with the present invention.
  • evaporation rates in between these two values it will depend on the details of the design and the application.
  • the evaporable metal portion 13 of conical first end portion 4 has been described and shown as conically-shaped and non-screw-like. Adding a screw-like profile to the evaporable metal portion 13 of conically-shaped first end portion 4 is not desirable. A screw-like configuration at the conical end would retard the arc's advance toward screw-like mid-section 9 or 609 and would generally reduce the lifetime of ignition electrode 1.
  • metal cylinder metal rod or metal cathode
  • evaporable alloys and semiconductors as well as evaporable metals, may be used to fabricate these rods, cylinders or cathodes.
  • the arc has at times been described as impinging and moving on the screw-shaped mid-section 9 of cathode 10. It should be readily evident to one skilled in the art that the arc first impinges and moves on the evaporable metal portion 13 of conical first end portion 4 before moving onto the cathode's 10 screw-like mid-section 9. That erosion occurs on conical first end portion 4 of metal cathode 10 is clearly seen in Fig. 5.

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Abstract

Cette invention a trait à une cathode utilisable dans des évaporateurs à arc électrique sous vide à impulsions que l'on peut employer pour l'évaporation et le dépôt de métaux et de semi-conducteurs, pour fabriquer des composants électroniques, tremper des surfaces métalliques, empêcher la corrosion de métaux et produire des films du type à dépôt CDA. Ces évaporateurs sont en mesure de résister à un très grand nombre d'impulsions d'allumage, d'orienter ou de commander le déplacement de la tâche cathodique grâce à un élément médian en forme de vis, de sorte que l'évaporateur produit des enduits uniformes. Ces évaporateurs ont un extincteur d'arc métallique à longue durée.
PCT/IL2003/000033 2002-01-14 2003-01-14 Cathode pour evaporateurs a arc electrique sous vide WO2003057939A2 (fr)

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Cited By (2)

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Publication number Priority date Publication date Assignee Title
EP2447978A2 (fr) 2005-03-24 2012-05-02 Oerlikon Trading AG, Trübbach Source d'arc
DE102015004856A1 (de) 2015-04-15 2016-10-20 Oerlikon Metaplas Gmbh Bipolares Arc-Beschichtungsverfahren

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US4505947A (en) * 1982-07-14 1985-03-19 The Standard Oil Company (Ohio) Method for the deposition of coatings upon substrates utilizing a high pressure, non-local thermal equilibrium arc plasma
US5013578A (en) * 1989-12-11 1991-05-07 University Of California Apparatus for coating a surface with a metal utilizing a plasma source
US5026466A (en) * 1987-06-29 1991-06-25 Hauzer Holding B.V. Method and device for coating cavities of objects
US5269898A (en) * 1991-03-20 1993-12-14 Vapor Technologies, Inc. Apparatus and method for coating a substrate using vacuum arc evaporation
US5744017A (en) * 1993-12-17 1998-04-28 Kabushiki Kaisha Kobe Seiko Sho Vacuum arc deposition apparatus

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US4505947A (en) * 1982-07-14 1985-03-19 The Standard Oil Company (Ohio) Method for the deposition of coatings upon substrates utilizing a high pressure, non-local thermal equilibrium arc plasma
US5026466A (en) * 1987-06-29 1991-06-25 Hauzer Holding B.V. Method and device for coating cavities of objects
US5013578A (en) * 1989-12-11 1991-05-07 University Of California Apparatus for coating a surface with a metal utilizing a plasma source
US5269898A (en) * 1991-03-20 1993-12-14 Vapor Technologies, Inc. Apparatus and method for coating a substrate using vacuum arc evaporation
US5744017A (en) * 1993-12-17 1998-04-28 Kabushiki Kaisha Kobe Seiko Sho Vacuum arc deposition apparatus

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2447978A2 (fr) 2005-03-24 2012-05-02 Oerlikon Trading AG, Trübbach Source d'arc
US9997338B2 (en) 2005-03-24 2018-06-12 Oerlikon Surface Solutions Ag, Pfäffikon Method for operating a pulsed arc source
DE102015004856A1 (de) 2015-04-15 2016-10-20 Oerlikon Metaplas Gmbh Bipolares Arc-Beschichtungsverfahren
US11060179B2 (en) 2015-04-15 2021-07-13 Oerlikon Surface Solutions Ag, Pfäffikon Bipolar arc-coating method

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