The present application is a continuation in part of prior-filed U.S. Patent Application No.07/728,566 filed July 11th, 1991. This invention was made with Government support under Contract No. DE-AC03-76SF00098 between the U.S. Department of Energy and the University of California for the operation of Lawrence Berkeley Laboratory and the U.S. Army Research Office and the Office of Naval Research under Contract No. ARO 116-89. The Government has certain rights in this invention.

BACKGROUND OF THE INVENTION The present invention relates to a continuous, broad beamed vacuum arc ion source. The inventive apparatus can be used to implantations into the surfaces of materials in order to modify their characteristics. This apparatus can also serve as a primary ion source for a number of different applications.

Ion implantation has proven to be highly useful for a number of purposes. Ion implantation is used in such diverse areas as semiconductor manufacture, treatment of large machinery part surfaces, and the manufacture of catalysts.

The wide applicability of ion implantation is due to its ability to specifically modify the surfaces of materials. Much of the function of various materials and components derives from their surface characteristics. As an example, catalytic function is a result of such surface

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activity. Also, the limitations of many machine parts involving wear or corrosion are due to surface phenomena.

Ion implantation provides an opportunity to treat only the portion of a material which will reflect on a particular function. Using such techniques, one can develop a component with good, inexpensive structural aspects to its bulk, but with a highly specialized surface. When expensive materials are required for surface function, treating the surface alone can make a technology economically feasible. An example would be platinum use in a large catalytic body.

Ion implantation has advantages over other surface treatment process. Ion implantation allows considerably better adhesion in diverse environments than plating or other techniques of surface deposition. Ion implantation can be used advantageously as a substitute for full body alloys. Ion implantation allows dramatic savings by limiting the need for costly materials. Additionally, metallic proportions which can not be achieved by alloy techniques can be created by physically forcing ions into a surface using ion implantation.

Previously available ion sources are of two main types; broad and narrow beam. Both these apparatus types and attendant techniques have allowed the production of various new materials and the treating of surfaces to varying degrees. However, each has limitations which, until the present invention, had not been overcome. Broad ion beams have been produced previously utilizing gases, such as nobel gases, as the ion source. Such ion implantation techniques have been used to treat surfaces in order to provide tribological modifications, generally of metals. Gas ions are implanted to decrease friction, wear, fatigue and corrosion on metal surfaces. Additionally, the general hardness of such materials are improved by such processing. However, ions from solid sources can not be employed in such apparatuses.

Finely tuned, low energy ion beams have been developed for use in such areas as the micro-electronics

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industry. These ion beam sources are able to utilize solids such as metals for ion sources, but only on a small scale with a small metal ion beam. A typical use for this technology is in micro-circuitry. Such apparatuses are capable only of low current ion production. As a result, they can only produce a narrow ion beam which is impractical for the implantation of large surfaces.

Some of the present inventors developed a number of pulsed mode, low duty cycle metal vapor vacuum arc ion sources. Such a device, termed MEWA (metal vapor vacuum arc) , was initially designed for use in production of high current uranium ion beams for use in fundamental heavy ion nuclear physics research. Some of the present inventors have used the insight gained by this nuclear research experience to produce ion beam generating devices suitable for certain manufacturing and other ion implantation needs.

Some examples of the commercially useful, advanced repeatedly pulsed ion sources developed by some of the present inventors are taught in U.S. Patent No. 4,714,860 issued December 22, 1987, U.S. Patent 4,952,843 issued August 28, 1990, and U.S. Patent No. 4,785,220 issued November 15, 1988, all to Brown et al. Such devices produce a reliable, controlled rate of ions, and are useful for a number of ion-implantation purposes.

The energy of the ion beam and the duty cycle of these advanced MEWAs developed by some of the present inventors are comparatively low. When run at higher energies or longer duty cycles, these apparatuses rapidly becomes dysfunctional. They typically can not be run at high energy levels for more than 10 minutes. These limitations result in a low rate of implantation of the ions. Additionally, the available ion beam size of any practical energy is small. When operated in a continuous, high energy manner, the previously patented MEWAs suffer from a number of operational malfunctions. These limitations of prior art

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were not obvious, and many were only recognized by the inventors during experimental operation.

When the prior MEWA's are run in a high power, continuous bases, the cathodic material quickly suffers from large scale vaporization. This phenomenon causes the major portions of the vacuum chamber to fill with metal vapor. The cathodic material then builds up on the anode, which produces an inappropriate anode configuration.

The maximum heat load, power load, and ion beam power density of the prior art MEWA apparatuses are rapidly exceeded when run on a continuous, high power basis. The triggering device either welds to the anode, or plates over and becomes non-functional. The extractor grids are rapidly destroyed. Many other physical malfunctions of the apparatuses also occur.

It would be very desirable to produce a high energy, large beam ion source that could be employed in a continuous fashion. It would be even more desirable to have an apparatus with this capability also allow the modulation of the energy of the ion beam. Further, it would be highly useful if a multi-use triggering mechanism were available, and that the apparatus's extractor grids allowed for a high power load and high ion beam power density.

SUMMARY OF THE INVENTION

The present invention is a continuous, high current ion producing apparatus and method. For the first time, a wide beam of high energy ionized metal or other conductive solids can be produced in a continuous manner using the inventive teachings. Using the present invention, direct current beams of metal ions with beam current two or three orders of magnitude higher than prior pulsed techniques is possible. This advancement is important for the industrial utilization of ion implantation technology, as well as being important from the perspective of fundamental ion source development.

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It is an object of the present invention to provide a high-energy, broad beamed continuous source of ions from a conductive solid material.

It is a further object of the present invention to provide a wide beamed, high energy ion source apparatus which can function continuously for upwards of eight hours.

It is yet a further object of the present invention to provide a high-energy ion source which can rapidly implant ions into a large surface area.

It is an additional object of the present invention to provide a high-energy ion source which allows the modulation of the ion beam energy during a single processing run. It is a further object of the present invention to provide a continuous high-energy ion beam with up to a 100% duty cycle.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of the device showing portions of the vacuum chamber enclosure in section.

FIG. 2 is a sectional view of the plasma discharge generation region and mechanism of the present invention.

FIG. 3 is a sectional view taken along line 3-3 of Fig. 2. FIG. 4 is a sectional view taken along line 4-4 of Fig. 2.

FIG. 5 is a view taken along line 5-5 of Fig. 2 FIG. 6 is a top plan view of the housing for the coolant and electrical conduits leading into the vacuum chamber, enlarged from its rendition on Fig. 1.

FIG. 7 is a sectional view taken along line 7-7 of Fig. 6.

FIG. 8 is a left end view of the housing depicted in Fig. 7 taken along line 8-8 of Fig. 7. FIG. 9 is a sectional view taken along line 9-9 of Fig. 6.

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FIG. 10 is a electrical schematic showing the electrical components employed in an embodiment of the present invention utilizing a flaring anode portion.

FIG. 11 is a schematic depicting a power supply to the embodiment of the present invention possessing a solenoid.

FIG. 12 is a partial front elevational view of a typical extractor grid used in the present invention.

GENERAL DESCRIPTION OF THE INVENTION The present invention represents a dramatic departure from prior art pulsed ion implantation technology. In order to provide for direct current operation of the present invention, the range of the power handling capacity, beam size, duty cycle and other parameters must differ substantially from prior art methods. The approximate range of such parameters in the present invention is in fact increased typically by a factor of 100 over prior art apparatuses. The careful design and selection of the interrelated components of the present invention, and their inventive configuration meets for the first time the challenge that such extremes of operation represent.

The description of the invention which follows demonstrate the intimate relationship between the inventive apparatus and process, and the unique function of the present invention.

APPARATUS COMPONENTS

Cathode The cathode in the present invention is sacrificial. The conductive material from which it is made becomes the source of the ion beam produced. It can be composed of virtually any electrically conductive solid material. For instance, a very wide range of metallic elements can be employed, such as Li, C, Mg, Al, Si, Ca, Sc, Ti, V, Cu, Mn, Fe, Co Ni, Cu, Zn, Ge, Sr, Y, Zr, Nb, Mo, Pd, Ag, Cd, In, Sn, Ba, La, Cc, Pr, Nd, Sm, Gd, Dy, Ho, Er, Tm, Yb, Hf, Ta, W, Ir, Pt Au, Pb, Bi, Th, and U.

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Alloys and other compounds can also be utilized as cathodic material. Typical cathodic materials would be titanium, cobalt, yttrium, tungsten, molybdenum, silicon, stainless steal, brass, cadmium, FeS, PbS, TiN, Sic, WC, UC, C, Pt and Pd, among others.

Appropriate cathodes for use in the present invention work hand-in-hand with the encompassing anode, and the designs of these two components are interrelated. The cathode must be initially seated fully within the bore of the anode. It is consumed during ion beam production. As it loses its mass, it recedes further into the anode, typically towards its point of attachment.

Ease of cathode replacement is a useful feature of the present invention. Continuous cathode replacement can be provided during operation by slowly advancing cathodic material, such as a metal rod, during cathodic consumption. By providing the required stock through a bore hole, the lifetime between cathode charges can be extended indefinitely. The cathode employed in the present invention is unusual in its size and shape for use in the production of ion beams, although similar cathodes have been used in different technologies. In fact, the geometry of the cathode of the inventive apparatus is in opposite proportionality to those of prior art ion sources. The present invention employs a short, squat cathode as compared to the long, thin cathodes of prior ion source apparatuses.

The shape of the cathode of the present invention can be rectangular, square, ovid, cylindrical, or of any other similar shape. The choice of shape may depend on the workability of the material, and the expense that shape modification would require. The shortest bisectional dimension of the cathode is typically less that its height. For instance, in the case of a cylinder, the relationship of the diameter to the height can be from about 1:1 to 100:1. More commonly, the relationship of diameter to height would be from about 10:1 to 3:2. The

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preferred proportionality of diameter to height would be about 2:1.

The size of the cathode will also vary depending on the particular configuration or use of the inventive apparatus. The initial dimensions of the cathode of the present invention can vary in height from lm ² to lcm ² . A typical range (flat dimension x height) would be from 1 meter x 20 cm to 5 cm x 2 cm. A preferred cathode size in the present invention is about 10 cm x 5 cm. A special cathodic cooling device is provided in order to assure that the maximum heat load is not exceeded. In prior art ion guns, sacrificial cathodes were typically cooled by conductive type configurations. In the present invention, the cooling liquid is put into direct contact with the cathode. In one embodiment of the present invention, this cooling liquid is simple water, but it can be virtually any cooling material. Because the surface subject to this cooling is large compared to the total cathodic mass, the efficacy of the cooling is greatly enhanced.

Anode The anode in the present invention is configured so as to surround the cathode and together those components constitute a plasma gun. A typical shape for the anode of the present invention would be an annular cylinder. In the cylindrical anode embodiment of the present invention, the anode is co-axial with the cathode. The anode and cathode are so designed that a gap is provided between these apparatus components. This gap can range from 1-5 cm, depending on the needs of the particular embodiment of the inventive apparatus. A typical range would be from about 2-4 cm, with a preferred range of about 3 cm. The gap is selected with a view to the appropriate flow of the developing plasma into the plasma cloud region of the apparatus. The diameter of the anode is chosen in view of its height, density of material, and expected use in order to assure adequacy of cooling. The diameter of the anode material surrounding the cathode can vary from about 1-50

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cm. A typical range for the anode diameter is from about 1-20 cm. A preferred anode diameter would be of about 10 cm.

Virtually any typical anodic material can be employed, and is selected with a view to the demands of the particular embodiment of the inventive apparatus which is desired, and the temperature and duration of its expected duty cycle. The proportions and absolute size of the anode is selected in view of the limitations of the chosen anodic material.

A special anodic cooling device is optionally provided in order to assure that the maximum heat load is not exceeded. This apparatus component is particularly useful when an arduous duty cycle is contemplated. It is also important when the ion beam energy will be employed at a particularly high level.

The optional anodic cooling device employed in the present invention can be one of any number of standard configurations. A particularly preferred design is a coil though which water is continuously circulated. This coil is in the configuration of a large cylinder co-axial with and encompassing the anode.

Triggering Means The present inventive apparatus employs a re-usable triggering means. The triggering means can include a laser, a gas puff, or a high voltage spark, among others. In the case of an inventive embodiment in which a spark is employed as a triggering means, a weld resistant material can be employed at the terminus of the spark producing tip to avoid its adhesion to the anode or cathode during ignition of the plasma.

Because a multiple-use triggering means is employed in the present invention, conditions closer to arc extinction can be used as re-triggering can occur without substantial disruption of the processing cycle. In the spark-trigger aspect of the present invention, a mechanical snap-back feature is employed to avoid impediment of the flow of developing plasma, and to protect the triggering device. Typically, a small hole in

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the wall of the anode provides an entry for the spark tip, so that its attendant electrical source remains outside the anode cathode gap area. This arrangement assures a much more reliable triggering function. Magnetic Field Plasma Guiding Means An optional feature of the present invention is a magnetic field means of guiding the plasma cloud as it escapes from the anode cathode gap area. This guiding generally is provided in a drift region of a length which can vary from about 0.1 to lm, and a field generated which can vary from about 0-100 G. While the field is typically 100 Gauss, it can range from 0 to 5000 Gauss. A preferred range is 20 to 200 Gauss. In some aspects of the present invention, this direction of the plasma allows optimal efficiency of the inventive apparatus. Additionally, a greater diversity of component configuration is available when the plasma stream or cloud can be channeled towards the ion extractor means.

When the field is produced by an electro-magnet, the opportunity is available to control the fraction of plasma which reaches the ion extracting means. The magnetic field can be varied in intensity. This variation causes a greater or smaller percentage of the plasma cloud to be directed to the extractor grids. In this way, the ion beam intensity can be controlled. Modification of the intensity can occur even during the continuous operation of the apparatus. This allows fine adjustments, and multiple processing conditions during a single arc event.

Ion Extracting Means Because of the high beam power, high duty cycle, and long continuous function of the present invention, the ion extracting means must be robust so as to avoid untimely deterioration. Additionally, even with such a structure, a typical ion extracting means generally will be exhausted in a matter of hours of continuous ion beam production. Therefore, in one aspect of the present invention, ease of replacement for the exhausted ion extracting means is provided.

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The ion extracting means of the present invention can be of any of several well-known types. In one aspect of the present invention, grids are used for this purpose. The grid can vary in size from about 1-lOOX the diameter of the anode. A typical range for the grid size is about 2-10X the anode diameter. A preferred range of grid size is about 5X the anode diameter.

The grids are often assembled in parallel arrays. These ion extractor grids can be employed in one aspect of the present invention. A high voltage is applied between two of the grids in order to form an ion beam, from the plasma. The outermost grid is generally employed at ground potential. The innermost grid is generally used at "extraction potential" (the energy of the ion beam to be formed) . The middle grid is usually at about 5% to 10% of the extraction potential, but negative, in order to impede electron flow.

Because of the large mass of material that is transported away from the cathode, the plasma transport region is considered to be a kind of "ash collection" region of the apparatus. For this reason among others, the extractor grids in some aspect of the present invention may need to be replaced relatively often. In such cases, these grids are designed to be both inexpensive and easily replaced.

In one aspect of the present invention, very large area extractor grids are provided. They are multiple (such as three grids) , multi-apertured with about a 50 cm diameter configuration. They are constructed of a strong, durable material such as aluminum, and can be from 2-10 mm thick. A preferred thickness is 4.7 mm. The beamlet hoes can be about 1 cm in diameter. Depending on the size of the grids and the particular needs of an inventive embodiment, there can be from 100 to 10,000 holes, with a preferred amount being about 1000. The extractor gap can be in the range of 1cm, with an optical transparency in the range of 30-80%, with a preferred value of 50%.

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CONFIGURATION AND OPERATIONAL PARAMETERS

Arc Current The present invention allows for considerably higher arc current levels then previously available in continuous ion beam production. In one typical embodiment of the present invention, the arc power dissipation is around 2Kw and the beam power is around 50Kw. While the present inventive apparatus does provide for modification of the arc current level, note that it is not possible to reduce the arc current to arbitrarily low levels. For instance, the arc will not operate at a current level of 1 A as it extinguishes before this value is obtained.

It is a well established property of vacuum arcs that there is a minimum current level at which these arcs will stay alive, but below which the cathode spots are not maintained (see, Vacuum Arcs - Theory and Application, J.M. Lafferty, ed, John Wiley and Sons, New York, 1980, incorporated herein by reference) . Therefore, the modulation of the power of the ion beam in the present invention is constrained by such absolute limitations of arc generation.

For an acceptably low probability of plasma extinction over long periods of dc operations, the minimum arc current can be taken as approximately 100A. For some cathode materials, a higher current will be required and for others, a lower current may be possible as will be appreciated by the ordinary skilled artisan. Thus power dissipation and cooling is a primary concern that alters the choice of parameters such a cathode configuration and extractor size.

Heat Accommodation Expected heat load for a particular chosen embodiment of the present invention is an important consideration in the particular design employed. Special cooling components are provided for a number of the functioning parts of the present apparatus. Some of these are required to allow the apparatus to function continuously for long periods at high energy levels.

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A large amount of heat is typically generated at the front face of the cathode during continuous, high power function of the inventive apparatus. The inventors designed the cathode in a flat cylindrical geometry to provide for efficient water cooling at this component's rear surface. Rather than attempt to provide adequate cooling using conventional conduction methods, the present invention bring water directly into contact with the cathodic material. This provides for an optimal removal of excess heat.

The anode is another source of heat production in the present invention. Unlike the cathode, in certain embodiments of the present invention, the apparatus can function at acceptable levels without a specific component for anode cooling. Some of the anodic heat derives directly from its own function. An additional source of anodic heating is heat from the cathode which it encompasses. As described above, in one aspect of the present invention, the anode is cooled by a co-axial water coil.

Cathode Mass Reguirements The requirements for cathodic mass per amount of ion implantation vary with different operational parameters and other aspects of a particular inventive embodiment. If the ion beam intensity is modulated substantially during the processing time, the efficiency of implantation as a percentage of cathodic mass is typically decreased. This effect is emphasized when the beam power is diminished by use of a magnetic field to diminish the amount of plasma in the plasma cloud region which is directed through the extractor means. Thus, when conservation of cathode material is desirable, control of beam intensity through modification of the distance between the beam arc and the extractor is the method of choice. The rate of removal of cathode mass by arc erosion has been studied by a number of researchers (see C.W. Kimblin, Journal of Applied Physics, Volume 44, Page 3074, 1973, and I.G. Brown, IEEE Trans. Plasma Science. PS-18,

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Page 179, 1990, incorporated herein by reference) . For most metals, the erosion rate is in the range of 20-60 micrograms per Coulomb of arc current. The necessary cathode mass in such cases can then be estimated to be of an order of lkG per day of steady operation.

Control of Beam Power The arc current cannot be reduced arbitrarily. None the less, the present inventive method allows the user to vary the beam current over a wide range and to levels considerably less that 1A. This is accomplished in the present invention by two separate means of control, which either separately or utilized together, provide unprecedented control over the beam current. These means, separately and together, provide straightforward control of the amount of plasma that is transported to the extractor grids, and thereby of the magnitude of the beam current produced.

In the first means of beam current arc modulation, the dc plasma gun is located at a distance from the extractor grids that can be varied from about 10 cm up to about 1 m. This can be done prior to initiation of the arc, or during the arc cycle. In one embodiment of the invention, this is accomplished mechanically by a rod attached to the anode and cathode portion of the apparatus. In other embodiments, automatic orientation with a motorized or robotics feature allows precise spacing and thus control of the beam current. This can be accomplished on an automated basis to avoid the need for operator attention, and provide very precise quality control of the product. Automated cyclic modification is possible, coordinated with automated target positioning in a mass-production setting.

In the second method of beam current arc control, the plasma transport region is immersed in a solenoidal magnetic field whose strength is continuously variable from zero up to about 100 G. This limits the percentage of the plasma cloud reaching the extractor, and thus the ion beam intensity. The ion beam intensity can also be

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controlled by varying the biasing on the beam extraction plates.

ADVANTAGES OF THE PRESENT INVENTION

Manufacturing Considerations The present inventive apparatus for the first time provides a practical means of ion implantation for a number of different manufacturing processes. Prior to the present inventive method, it was not possible to provide solid material ion implantation of large areas. Thus, thanks to the present inventive apparatus and method, large scale applications such as large turbine blades, various engine components, and large industrial parts can now receive the benefits of ion implantation. Novel alloy surfaces can also be produced. Another innovation of the present invention is the ability to carefully modulate the ion beam power to accommodate varying manufacturing needs and requirements. Thus, penetration of ions into the surface of materials can be carefully controlled. Additionally, the heating of the treated surface by the energy of ion impact can be precisely modulated, and ideal heating levels maintained. This capacity of the present invention has particular applicability to superconductor and semiconductor arts. For instance, large surface superconducting films could be produced, and then cut into thin strips for certain applications.

The ability to treat heat vulnerable materials has been achieved by the present invention due to its ability to vary the intensity of the ion beam, and to provide broad, relatively low energy sweeps of ions over a surface. This capacity has special applications in the treatment of glasses, plastics, and other materials which are sensitive to high heats. Tinting and metalizing glass can be used for automated tint variability.

Beam Size The ability of the present inventive apparatus to produce a large continuous ion beam of a solid material is a hallmark of the present invention. The beam size is measured by the largest cross section of

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the beam. By varying the different components and available parameter settings of the present invention, a wide variety of ion beam sizes can be produced. Beams from about 10 meters to 10 cm can be efficiently generated. A more typical range of beam production is about 5 meters to 50 cm. A preferred beam size is in the range of about one meter.

Providing Optimal Beam Power In the present invention, the direct current beam power is high as compared to prior art devices. The present invention is designed for a large beam areas, which mitigates the potential for melting or otherwise compromising the implantation target. This design feature also provides for appropriate beam power density dissipation in the beam formation electrodes themselves.

By using a very large area beam, the inventors obtained a large cross-sectional area in part by expanding the metal plasma prior to extraction. An other factor in achieving this unprecedented large beam was by utilizing very large area beam formation electrodes, which can take the form of extractor grids.

DETAILED DESCRIPTION OF THE INVENTION The invention as a whole is shown in the drawings by reference character 10. The continuous high current metal ion source 10 includes as one of its elements a vacuum chamber 12 having end portions 14 and 16, as well as, cylindrical side portion 18. End portion 16 includes recess 20 having a target 22 on the inner surface 24 of end portion 16 to receive the ion beam generated by source 10, directional arrows 26.

Vacuum enclosure 12 may be constructed dielectric material such as Lucite, glass, and the like. The overall shape of vacuum enclosure 12 may be cylindrical and define a vacuum chamber 28 therewithin. With reference to Fig. 2, a plasma generation region 30 is depicted in section and is positioned within chamber 28. Plasma generation region 30 includes cathode 32 and a surrounding anode 34.

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Cathode 32 is relatively large when compared to the prior art pulsed vacuum arc source cathodes. As depicted in Fig. 2, cathode 32 is approximately 2 inches in diameter and 1 inch thick. Anode 34 is approximately 3 inches in diameter.

Means 36 is shown in the drawings for cooling cathode 32. Means 36 may take the form of tubes 38 and 40 which extend through axial member 42. Tubes 38 and 40 may be formed of copper while axial member 42 includes an outer tube 44 which may be formed of stainless steel. Means 48 is also depicted in the drawings for cooling anode 34. Means 48 may take the form of tubes 50 and 52 which lead into an helical member 54 welded to the outer surface 46 of anode 34. Tubes 50 and 52 are not in electrical contact with tubes 38 and 40 although the fluid used to cool cathode 32 and anode 34 interlink. With reference to Fig. 4, it may be observed that cross-link tubes 56 and 58 feed fluid to tubes 50 and 52 which run through a block 60 fastened to metallic disk 62 by fasteners 64. Openings 66 and 68 represent jogs or turns in cross-link tubes 56 and 58. Axial member 42 includes a metallic plate 70 which holds the end 72 of outer tube 44. Insulative spacer 74 separates metallic plate 70 from metallic disk 62. Plurality of 0-ring seals 78 prevent leakage of any fluid outside passageway 80. Plate 70 and disk 62 may be formed of brass or similar material. Spacer 74 may be constructed of a thermal plastic material such as Delrin. Insulative cup 82 separates metallic disk 62 from metallic member 84 which butts against the back surface 86 of cathode 32. Metallic ring 88 connects anode 34 with metallic disk 62. Metallic tubes 38 and 40 also serve to carry electrical current to cathode 32 and anode 34. For example, tube 38 transmits electrical current though metallic member 84 and to cathode 32. On the other hand, tube 40 transmits electrical current through metallic disk 62 and metallic ring 88, to anode 34. It should be noted that tubes 38 and 40 include ends 90 and 92 which stop short of tubes 50 and 52, to obviate electrical contact

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therebetween. Passages 94 and 96 permit the flow of fluid from tubes 38 and 40 and tubes 50 and 52 without such electrical contact.

Means 98 is also included in the present for triggering a continuous plasma discharge from cathode 32, Fig. 2. Means 98 further includes means 100 for delivering an electrical arc current to cathode 32 during a certain time period to initiate production of the continuous plasma discharge. Such delivery means may take the form of a rod 102 constructed of weld-resistant material such as tantalum. Rod 102 is slightly curved and fixed to a holder 104 which includes a sleeve 106, Figs. 2 and 5. Sleeve 106 interconnects split terminal block 108 and L-shaped arm 110. Conductors 112 electrically connect to terminal 108 at pins 114 and lead to a source of a electrical current which passes from electrical connector 116 and originates with a source of a electrical current that will be described hereinafter. Rod 102 extends through an opening 118 in anode 34 is capable of touching the front surface 120 of cathode 32. In this regard, L- shape arm 110 rotates at pivot element 122, specifically pivot pin 124, Figs. 2 and 3. Pivot pin 124 is actuated by solenoids 126 and 128 which are activated by an electrical switching mechanism 130, Fig. 10. Conductors 132 on electrical terminal 134 feed the electrical switching current from switching mechanism 130 to conductors 136 at pivot element 122. Electrical current may be fed to terminal 108 via conductors 112, from an electrical connector 116 through passage 80 or by any other suitable entrance to chamber 28. Clamp 138, Fig. 3, and fastening means 140 holds pivot element 122 to tube 44.

Referring again to Fig. 1, it may be observed that means 142 for adjusting the distance between cathode 32 and the ion extracting means 144, which will be described hereinafter is shown. In this regard, tube 44 supported to end 14 of vacuum enclosure 12 by bushing 146 and bolted flange 148. Seal 150 surrounding tube 44 permits tube 44

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to move according to directional arrow 152 without breaking the vacuum seal within chamber 28.

Turning now Fig. 6-9, it may be found that metallic tubes 38 and 40 are depicted as extending through stainless steel tube 44 and are fixed to support 154 by the use metallic clamp 156 and plurality of fasteners 158, Figs. 6 and 7. Cooling fluid inlets 160 and 162 connect to tubes 38 and 40 at support element 164, Fig. 9. In addition, electrical connectors 166 and 168 bolt to insulation block 170 and connect to electrical clamp pins 172 and 174 which lie within insulative spacers 176 and 178. Electrical clamps 180 and 182 fasten pins 172 and 174 to tubes 38 and 40. Thus, electrical connectors 166 and 168 pass electrical current to cathode 32 and anode 34. Block 170, spacers 176 and 178, and support 154 form a coolant and electrical supply housing 180 at the terminus of stainless tube 44 which serves to mechanically cantilever the plasma generation unit 182 within chamber 28. Returning now to Fig. 1, solenoid 184 optionally confines plasma generated by plasma generation unit 182 through generation of a magnetic field. Plurality of cooling tubes 186 surrounds solenoid 184 heat by the plasma plume. Electrical connectors 188 and conductors (not shown) feed electrical current into solenoid 184. In addition, tubes 190 and 192 circulate coolant through solenoid 184 which flow from tubes 38 and 40 at pivot element 122. It may be seen that the conical element 194 (shown partially in Fig. 1) may be substituted for solenoid 184 to permit expansion of the plasma generated by cathode 32. In this case, vacuum enclosure 12 would also formed to a larger configuration to accommodate conical element 194. As will be described hereinafter, conical element 194 is electrically linked to and serves as a portion of anode 34.

With further reference to Fig. 1 alteration is drawn to extracting means 144 depicted in Fig. 1 as a pair of grids 196 and 198. Grid 196 is a power grid while grid

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198 is grounded. It should be noted that a large variety of grid combinations may be employed in this regard with extracting means 144. In any case, power is supplied to grid 196 which is mounted on insulation ring 200 within vacuum chamber 28. Grids 196 and 198 may be of rather simple construction such as the metal plate 201 having a plurality of perforations 202, depicted in Fig. 12. It is anticipated that grids 196 and 198, as well as any other grids employed, would be disposable and easily replaceable within source 10, should a metallic plating develop. With further reference to Fig. 10, it should be apparent that a schematic of the electrical interconnection for the elements heretofore described is shown. Electrical switch mechanism 130 includes a source of electrical power 204 which activates two way switch three position 206 to either activate contact 208 or contact 210. It should be understood that contact 208 is connected to solenoid 126 while contact 210 is connected to solenoid 128. The solenoid 126 moves rod 102 into contact with cathode 32 and while solenoid 128 moves rod 102 from contact with cathode 32. In this manner, the contact of rod 102 with cathode 32 is momentary. Other triggering means 98, such as a laser beam, may be employed in place of rod 102. Cathode 32 receives power from arc supply 212 which may be a Miller WCP-260TS power supply having a 50 volt, 250 amp DC output. Isolation transformer Tl intercepts any interference from AC power source 214. Arc supply 212 is also connected to anode 34 and expanding or conical element 194. Thus, conical element 194 is at the same potential as the anode 34. Ion extracting means 144 includes a plasma grid 216 which receives power from supply 218 and limiting resistor R2 which rated at 10 Kohms. Switch means 220 switches between plasma grid power supply 218 and capacitor Cl which may be rated at 0.1 Mfarad. Capacitor Cl may serve as a portion of conditioning means 224 for the suppressor grid 226 and ground grid 228. Spark gap 230 permits the grids to spark over, break down, and thereby become

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conditioned to high voltage operation. Capacitor C2 aids in this endeavor and is rated at approximately 0.5 Mfarads. Suppressor grid power supply 232 and power suppressor grid 226 in conjunction with plasma grid 216 extract ions from the plasma discharge from cathode 32. Of course, an ion beam is directed at target 22 after passage through ground grid 228. In the embodiment depicted in Fig. 1 employing solenoid 184, a variable solenoid power supply may be used therewith. Fig. 11. The following is an example which illustrates the usage of the high continuous current metallic ion source 10 of the present invention and is described hereinafter for illustrative purposes only and is not intended to limit the scope of the invention sought for patenting:

EXAMPLE 1

The device depicted in Fig. 1 was operated at steady- state employing a titanium cathode. After 30 minutes the operation was terminated by switching off the arc supply 212. Several test runs were conducted using the arc current set at about 150 Amperes. The plasma ion current was measured down stream at target 22 as high as 6 Amperes. During several of the runs, a set of beam formation electrodes were set up to measure the size of the extracted beam. The beam size was determined to be almost 20 cm in diameter. The available power supply for such beam extraction was about 10 kilo vaults a 200 iliamp beam current.

The following table represents the minimum amperage values necessary to sustain continuous plasma discharge from cathodes having various metallic compositions:

TABLE I

AMPERAGE NECESSARY TO SUSTAIN CONTINUOUS CATHODIC MATERIAL DISCHARGE GREATER THAN 3 HOURS Molybdenum 300-400 Amps

Titanium 200 Amps (Approx)

Copper 100 Amps (Approx)

Cadmium 50 Amps (Estimated)

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In operation, the user positions target 22 within vacuum enclosure 28. Cathode 32 and anode 34 are cooled by fluid passing through tubes 38 and 40. Trigger means 98 is activated such that rod 102 is rotated into contact with cathode 32 by the use of solenoid 126 and switching circuit 130. Upon the application of an arc current from rod 102 to cathode 32 rod 102 is immediately retracted using solenoid 128 found in pivot element 122. At this point cathode 32 and anode 34 interact to create a prolific plasma plume in a continuous manner. The plasma plume begins in plasma generation region 30 and passes through drift region 236. The plasma discharge or plume is confined within drift region 236 if a solenoid, such as solenoid 184, is employed. On the other hand, conical element 194 is expansion of the plasma and, in a sense, a dilution of the intensity of the plasma plume before entering ion extracting means 144. In addition means 142 may be employed to adjust the distance between cathode 32 and extracting means 144. As such, axial member 42 may slide through seal 150 according to directional arrow 152. Means 144 and conical element 194 may be deemed means 238 for controlling the intensity of the plasma discharge while maintaining the current from arc supply 212 at a certain value, commensurate with the particular cathodic material. After passing through grids 216, 226, and 228, Fig. 10 a high intensity ion beam is passed to target 22 for implantation purposes. It has been found that cathode 32 may be run continuously until expended as long as the minimum current is maintained thereon. Grids 216, 226, and 228 of the construction described in Fig. 12 are easily replaced and should be considered disposable elements.

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