US3720598A - Cryogenic arc furnace and method of forming materials - Google Patents

Cryogenic arc furnace and method of forming materials Download PDF

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Publication number
US3720598A
US3720598A US00103086A US3720598DA US3720598A US 3720598 A US3720598 A US 3720598A US 00103086 A US00103086 A US 00103086A US 3720598D A US3720598D A US 3720598DA US 3720598 A US3720598 A US 3720598A
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capacitor
discharge
discharge circuit
hearth
establishing
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US00103086A
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W Thompson
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International Business Machines Corp
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International Business Machines Corp
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    • 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
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F3/00—Changing the physical structure of non-ferrous metals or alloys by special physical methods, e.g. treatment with neutrons
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H10N60/01—Manufacture or treatment

Definitions

  • ABSTRACT This disclosure provides apparatus for achieving rapidly a high temperature are discharge in the region of a material to be vaporized. Surrounding the region of the arc discharge is a cryogenic fluid against which both the arc and the vaporized produces exert pressure. The effect of the presence of the cryogenic fluid adjacent to the high temperature region is to constrain the arc discharge strongly and to quench rapidly the material in the vapor state to the solid state. As a consequence of the localized heating and rapid quenching in the cryogenic arc furnace, special materials and physical states thereof are achieved. Illustratively, chemical products and amorphous conditions of materials are achieved for the practice of this disclosure not heretofore contemplated in the practice of the prior art.
  • the material to be vaporized is ab initio established in location for a capacitive arc discharge and the capacitor plates are caused by mechanical shock to approach each other so that the discharge occurs preferentially at a preselected path on the material.
  • the prior art has known how to produce small circuit elements through use of photoresist techniques together with diffusion of ancillary materials into a semi-conductor material.
  • very small circuit elements of amorphous material or superconducting material are produced in a cryogenic environment.
  • high temperatures states are frozen into the material which do not alter sufficiently at operational temperatures of interest to change either chemical or physical state.
  • circuit elements dimension is of the order of micron size regions.
  • the precise initial portion of electrical discharge from the capacitor probe point may not be known, it is readily ascertained relative to the geometry of the substrate wafer and thereafter is essentially fixed relative to the probe for any given fabrication procedure.
  • the localization of the arc discharge is determined both by the geometry of the capacitor probe and the constraint on the discharge by the proximatecryogenic fluid.
  • the practice of this invention is based on the discovery that if superconducting leads are used throughout the discharge circuit to a point discharge in a cryogenic fluid, a high temperature plasma of material in the arc discharge is formed and rapidly quenched by the proximate cryogenic fluid.
  • the rapid quench of the plasma provides new chemical and physical states for the material established in the arc discharge and homogenized distribution of the components of the material throughout the body of the resultant solid state material.
  • a device for the practice of this invention incorporates a capacitor with superconducting plates and superconducting electrical energy transfer leads thereto, a hearth in the vicinity of the resultant arc discharge for holding initially the material to be vaporized to a plasma, and a cryogenic fluid environment within which the arc discharge is established. Since the cryogenic fluid is non-conducting, it effectively constrains the arc but does not participate therein.
  • the device includes mechanical or electrical means for causing the capacitor probe temporally to approach the hearth material thereby initiating the arc discharge and effecting the release of the energy stored in the capacitor into a small spatial volume.
  • the practice of the invention provides a cryogenic arc discharge device which is capable of producing very high local temperatures by the use of a fast superconducting discharge circuit and a fast recondensation of the vapor products by use of a cryogenic fluid in intimate contact therewith.
  • the superconducting capacitor is charged up and discharged through high current superconducting leads to a superconducting point electrode which is moved vertically by a mechanical shock.
  • the use of superconductivity allows high current density for discharge over a few microseconds.
  • the use of the cryogenic fluid gives the quick recondensation of the reactant material.
  • the pointed discharge electrode is caused to move either over all the material or to lay out a predetermined circuit on the hearth substrate.
  • the movement of the hearth substrate under the discharge probe may be any type of mechanical manipulator providing X-Y motion, rotary motion or linear motion. However, it is required that the hearth surface be connected electrically to the capacitor with superconducting leads.
  • It is another object of this invention to provide a cryogenic arc furnace comprising a capacitive arc discharge device having one electrode movable by electrical or mechanical shock so that a periodic application of shocks causes sequential discharges in a given region or along a given path.
  • FIG. 1 is a functional diagram showing some structural components of a cryogenic arc furnace for the practice of this invention wherein an arc discharge is established between a probe mounted on a movable capacitor plate and the discharge is repetitively established by the synchronous cooperation of electrical means for charging the capacitor" and" electromechanical means for discharging it.
  • FIG. 2A is a detailed cross-sectional view of a cryogenic arc discharging apparatus embodying the principles illustrated in FIG. 1 and showing the cooperative environment of capacitive arc discharge region, cryogenic fluid, means for charging the capacitor and means for discharging it to modify either a chemical or physical state in the material of the arc discharge by rapidly vaporizing it and simultaneously quenching it via the cryogenic fluid.
  • FIG. 2B illustrates a modification of FIG. 2A wherein the support mount for the hearth is indicated to be also movable in the plane relative to the capacitor probe as well as vertically with respect to it.
  • FIGS. 1A, 2A and 2B Exemplary embodiments of this invention are illustrated in FIGS. 1A, 2A and 2B of which FIG. 1 is a functional diagram showing the correspondence of the several material elements of the apparatus, FIG. 2A is a derived cross-sectional drawing showing the actual relationship of the several aspects of the apparatus in an operational environment and FIG. 2B is an addendum to FIG. 2A for indicating means for adding planar movement of the material mounting platform relative to the capacitive point electrode.
  • a capacitor having plates 10 and 18 is connected to electrodes 20 and 22, respectively, of the arc discharge furnace.
  • the electrodes 20 and 22 are respectively the locations for the material to be treated and the determining point for the arc discharge.
  • a direct voltage source 34 charges the capacitor via a resistor 36.
  • the discharge of the capacitor is achieved by shock from plunger 24 driven by magnetic coil 26 which is powered from alternating current source 32.
  • the capacitor electrodes and the mechanical shock device are within the chamber of a cryogenic fluid dewar 30.
  • the embodiment presented in detailed cross-sectional view in FIG. 2A includes a capacitor having a base plate 10 and a top plate 12.
  • Superconducting superconductors such as tantalum or niobium are used for the base plate 10 and the top plate 12.
  • Base plate 10 and top plate 12 together comprise one electrode of the capacitor. Tantalum is especially suitable as the capacitor material because of the beneficial characteristics of the tantalum oxide, i.e., thinness and pin hole free. Further, the tantalum oxide is readily grown naturally on the tantalum surface in a high temperature oxidizing atmosphere.
  • the other electrode of the capacitor 18 is a thin tantalum sheet having a natural oxide or anodized oxide layer thereon.
  • the capacitor plate 18 is a thin membrane of tantalum of about 10 mils thickness.
  • the central electrode 18 of the capacitor and the two outer electrodes 10 and 12 comprise a transmission strip line which transmits the stored energy in the capacitor to the arc discharge at electrode 22.
  • the hearth 20 is shown in screw form for establishing the material to be vaporized in the cryogenic arc furnace.
  • the material 23 is established in the hearth adjacent to the point electrode 22.
  • the hearth 20 need not be a superconducting material, it is beneficial so as to minimize resistive losses in the arc discharge.
  • the screw 20 is positioned vertically in a manner which will be described hereinafter.
  • the discharge point electrode 22 is also a superconductor such as tantalum which is affixed to the capacitor membrane 18.
  • the discharge electrode 22 is welded or established in good electrical contact for conventional fabrication technique to the surface of the capacitor membrane 18.
  • the shape of the point electrode 22 is determined by the size of the discharge area to be formed on the surface of the hearth 20.
  • the impact slug is mounted in upper housing portion 12A established above discharge point electrode 22.
  • Drive coil 26 surrounds impact slug 24.
  • the drive coil 26 is connected to oscillator 22 which periodically drives the impact slug 24 against the membrane 18 causing point electrode 22 to approach the hearth 20.
  • the timing of the alternating voltage is coordinated with the mechanical recovery of the system comprising the capacitive membrane 18, point electrode 22 and impact slug 24.
  • the impact slug 24 is insulated from the capacitor 12 by an insulation sleeve 28 which may be, for example, of teflon or other suitable dielectric, providing insulation properties for the operation of the apparatus of FIG. 2A.
  • the electrical circuit for charging the capacitor comprises a battery 34 and resistor 36 connected by leads 35A and 358 to capacitor base plate 10. and capacitor membrane 18, it being understood that capacitor top plate 12 is electrically connected to base plate 10 and is therefore at the same electrical potential.
  • the cryogenic dewar 30 surrounds the capacitor and the drive mechanism and chamber 31 thereof is filled with cryogenic fluid, e.g., He, introduced into the dewar chamber 31 via entrance orifice 31A and removed therefrom via exit orifice 318.
  • cryogenic fluid e.g., He
  • Base plate 10 has orifices 40 from dewar chamber 31 into chamber 41 wherein .are located the point electrode 22 and hearth 20 with the material 23.
  • Probe superconductors and alloys may illustratively be Nb, Ta, Pb, NbTa, NbZr.
  • the reactants are placed in the electrode hearth 20 either as small grains or as evaporated layers.
  • a mechanical adjustment is made to set the electrodeelectrode distance both before and after impact by slug 24.
  • The'discharge spacing is set by varying the coil 26 drive power and the predischarge spacing is set by the hearth adjustment to be low current with field emission insufficient to cause heating or capacitor discharge, e.g., to 100,000A.
  • the capacitor is then charged to test voltage and the impact slug 24 is driven down onto the drumhead 18 surface giving sharp vertical motion to the probe 22 and discharging the capacitor into the arc plasma formed immediately above the surface of hearth 20.
  • the probe is tantalum with an oxide coating.
  • FIGS. 1, 2A and 2B Further details of the nature of the materials and the operation of the cryogenic arc furnace illustrated in FIGS. 1, 2A and 2B will now be presented.
  • the superconducting capacitor is charged to several hundred volts which is a few joules and then discharged through the high current leads, i.e., the positive leads 10 and 12 and the negative lead 18 of FIG. 2A.
  • the cryogenic fluid e.g., liquid He
  • the cryogenic fluid e.g., liquid He
  • the liquid helium in the chamber 41 causes the reactive products to recondense quickly, thereby freezing in the high temperature phases. Additionally, because of the mechanical vacuum properties of liquid helium, contamination of the reacted product is minimized.
  • the discharge time of the device is determined by the electrical circuit characteristics in the cryogenic environment. Important parameters are the superconducting electrode path between the capacitive region which is on the outside of the diaphragm to the central discharge point which is at the center. This is a superconducting waveguide with low losses up to discharge times being of the order of the energy gap frequency. The discharge may be increased to the gap frequency which is in the high microwave frequency region. Other than that the discharge time is determined solely by the geometrical waveguide properties of the capacitor.
  • the charging time of the capacitor is determined by the RC time constant of the electrical circuit consisting of the external battery 34 and resistor 36 combination in series with the capacitor which must be fast enough to recharge the capacitor before the next discharge.
  • the discharge time (frequency) is in the order of milliseconds, the external charging time must be faster than this. Under high frequency discharges and large energy discharge of certain operational conditions the pressure in the discharge chamber may be sufficient to require relief of the pressure by additional vent holes or use ofa pump liquid system.
  • FIG. 28 illustrates a modification of the device as shown in FIG. 2A whereby the hearth screw 20, hearth 20A and material therein 23 is readily moved via seal 21 forpositioning any point thereof both vertically and horizontally relative to the probe point electrode 22.
  • the hearth screw 20 is shown expanded in size so that it may conveniently support a conventional X-Y adjustment table relative to the probe point electrode 22.
  • the X-Y table is indicated generally by the arrow 50.
  • the X-Y table and the controls therefor consist of X movement station 52 and Y movement station 54.
  • the hearth 20A and material 23 therein is supported on Y movement stage 54.
  • Control cable 56 is connected to the X stage 52 and via the hearth shaft 58 is conveyed to the knob 60 whose rotation controls the X stage movement.
  • the Y stage 54 is controlled by cable 62 which communicates via hearth shaft 58 to knob 64 whose rotation controls the Y movement.
  • the Z movement is controlled by rotation of the hearth screw 20 as is accomplished in the design
  • the tunneling trace before amorphous Ga formation showed the characteristic Schottky barrier type tunneling
  • the tunneling trace after formation of the amorphous gallium on one of the wafers showed the existence of the superconducting region.
  • the superconducting energy gap and the transition temperature of this region was determined by the tunneling method.
  • the superconducting transition temperature T was 8.2, in good agreement with the published data on amorphous gallium.
  • the superconducting energy gap ratio to T was 4.2, also in agreement with published data on amorphous gallium indicating that amorphous gallium had formed in a small region on the wafer.
  • the magnetic field characteristics indicated that the particle size of amorphous gallium created was somewhat less than 1,000A in diameter.
  • the lanthanum selenide system was also investigated by the technique of this invention.
  • the selenium rich phase, La,Se was converted to the lanthanum rich phase, La Se, by means of vaporizing in situ and fast recondense according to the principles of this invention.
  • the material properties were investigated by electron probe tunneling.
  • the current vs. voltage curves indicated the enhancement of superconductivity.
  • the lanthanum rich phase is a good superconductor with a transition temperature which depends on the density of vacancies in the material.
  • the vaporization temperature was greater than 2,000C and the formation temperature was in the l.35 to 4.2"K range.
  • the reactant material is made much more reactive than normally because it is ionized more and because there is more impact energy per collision.
  • the chemically inert element argon has been made in the prior art to form compounds by first heating it to high temperatures in an accelerator. It is believed that new compounds of the high melting point elements W, Os, Rh, Mo and Ta will be formed by the rapid quench technique of this invention.
  • the transition temperature of superconducting material is sensitive to the crystal phase and in the search for higher temperature superconductors, the high temperature crystal and amorphous phases of the binary, ternary and extended compositions of the presently known superconductors can be looked at. Namely, through using a hearth material which consists of various combinations of Nb, Si, Sn, Al, V, Ga, Ge and Zr, there may be provided unique superconductor materials.
  • a small region on a gallium arsenide wafer can be changed in its surface chemical state, e.g., 4GaAs+3O 2Ga O +A 5 or superconducting electrical elements of amorphous Ga, e.g., GaAs Ga+As, can be placed at preferred locations.
  • Superconductors with higher transition temperatures may be obtained by going to high temperature formation through the practice of this invention. It is known that amorphous material has lower phonon energy values than the corresponding crystalline material which enhance the superconducting correlations in the material thereby giving it a higher transition temperature. Examples are the crystalline gallium which has a transition temperature of a little over 1 and the amorphous gallium which has a transition temperature of 8.4K, an enhancement of about 7 times.
  • Apparatus for changing a material from one state to a different state comprising:
  • Apparatus for changing a material from one state to a different state comprising:
  • a capacitor having a first and second plate positioned on either side of said material to be changed
  • Apparatus for changing a material from one state to another state comprising:
  • a capacitor structure including two capacitor plates consisting of respective superconductive materials
  • said one capacitor plate includes two portions, one said portion mounting said hearth and said other portion mounting said mechanical means;
  • said portion mounting said hearth including a means for juxtaposing said hearth relative to said probe point;
  • said other capacitor plate being in membrane form
  • said mechanical means including:
  • electromagnetic coil means mounted on said other portion of said capacitor for mechanically driving said probe point to cause it to change relative position to said hearth;
  • Apparatus for generating a plasma comprising:
  • Apparatus asset forth in claim 10 wherein said means for discharging said electrical discharge circuit includes mechanical means.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Analytical Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Superconductor Devices And Manufacturing Methods Thereof (AREA)
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US00103086A 1970-12-31 1970-12-31 Cryogenic arc furnace and method of forming materials Expired - Lifetime US3720598A (en)

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GB (1) GB1368972A (enExample)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3925177A (en) * 1973-01-30 1975-12-09 Boeing Co Method and apparatus for heating solid and liquid particulate material to vaporize or disassociate the material
US4036720A (en) * 1976-10-22 1977-07-19 The United States Of America As Represented By The Secretary Of The Navy Hydrogen isotope separation
US6730370B1 (en) 2000-09-26 2004-05-04 Sveinn Olafsson Method and apparatus for processing materials by applying a controlled succession of thermal spikes or shockwaves through a growth medium
US7126810B1 (en) * 2003-06-24 2006-10-24 Mueller Otward M Cryogenic capacitors

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU202359A1 (ru) * Электрод для формирования мощных электрических разрядов в жидкости
US2934631A (en) * 1955-06-30 1960-04-26 Imalis Rose Electrolytic metal shaping
US3122628A (en) * 1963-01-31 1964-02-25 Inone Kiyoshi Electrical discharge grinding apparatus with automatic electrode reshaping provision
US3384467A (en) * 1964-02-03 1968-05-21 Avco Corp Method of and means for converting coal
US3619549A (en) * 1970-06-19 1971-11-09 Union Carbide Corp Arc torch cutting process

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU202359A1 (ru) * Электрод для формирования мощных электрических разрядов в жидкости
US2934631A (en) * 1955-06-30 1960-04-26 Imalis Rose Electrolytic metal shaping
US3122628A (en) * 1963-01-31 1964-02-25 Inone Kiyoshi Electrical discharge grinding apparatus with automatic electrode reshaping provision
US3384467A (en) * 1964-02-03 1968-05-21 Avco Corp Method of and means for converting coal
US3619549A (en) * 1970-06-19 1971-11-09 Union Carbide Corp Arc torch cutting process

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3925177A (en) * 1973-01-30 1975-12-09 Boeing Co Method and apparatus for heating solid and liquid particulate material to vaporize or disassociate the material
US4036720A (en) * 1976-10-22 1977-07-19 The United States Of America As Represented By The Secretary Of The Navy Hydrogen isotope separation
US6730370B1 (en) 2000-09-26 2004-05-04 Sveinn Olafsson Method and apparatus for processing materials by applying a controlled succession of thermal spikes or shockwaves through a growth medium
US20040221812A1 (en) * 2000-09-26 2004-11-11 Sveinn Olafsson Method and apparatus for processing materials by applying a controlled succession of thermal spikes or shockwaves through a growth medium
US7126810B1 (en) * 2003-06-24 2006-10-24 Mueller Otward M Cryogenic capacitors

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GB1368972A (en) 1974-10-02
FR2120783A5 (enExample) 1972-08-18
JPS547966B1 (enExample) 1979-04-11
DE2164762A1 (de) 1972-07-27

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