Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B6/00—Heating by electric, magnetic or electromagnetic fields
  • H05B6/02—Induction heating
  • H05B6/22—Furnaces without an endless core
  • H05B6/24—Crucible furnaces
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/02—Silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B41/00—Obtaining germanium
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
  • C30B11/001—Continuous growth
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
  • C30B11/04—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method adding crystallising materials or reactants forming it in situ to the melt
  • C30B11/08—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method adding crystallising materials or reactants forming it in situ to the melt every component of the crystal composition being added during the crystallisation
  • C30B11/12—Vaporous components, e.g. vapour-liquid-solid-growth
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B23/00—Single-crystal growth by condensing evaporated or sublimed materials
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B23/00—Single-crystal growth by condensing evaporated or sublimed materials
  • C30B23/002—Controlling or regulating
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
  • C30B29/02—Elements
  • C30B29/06—Silicon
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/25—Process efficiency

Definitions

• This invention is in the field of materials and more particularly relates to the manufacture of high purity semiconductors.
• the silicon deposition rate is limited because the sili- ' con filament must be maintained at a temperature below the melting point of silicon, which is approximately 1440°C.
• this process is usually carried out within a quartz reaction vessel and the vaporized reactants often react with the inner walls of the reactor producing oxygen contamination of the silicon deposit.
• double-walled, water-cooled quartz reaction chambers have been developed to overcome this, such reactors are inherently fragile and are often thermally inefficient.
• power leads enter- ing the reaction chamber must be carefully selected to prevent reaction with the feed vapor or by-products.
• silicon deposition in this process is in ⁇ herently a batch operation which does not lend itself to modifications for continuous deposition.
• the rod After formation of a silicon rod by this process, the rod is typically removed from the reactor and subjected to float-zoning operations to purify it. Such operations not only enhance the possibility of introducing contami ⁇ nants, but are also time-consuming and costly. Although not widely practiced commercially, many other techniques for producing high purity silicon have
• a quartz reactor is employed which is divided into an upper and a lower chamber by the coaxially arranged hollow annular partition which is preferably formed of silver, and is kept cool by circu ⁇ lating water or other cooling fluid therethrough.
• the upper end of the seed crystal is melted by directly coupl ⁇ ing it to high frequency alternating currents applied through an annular coil surrounding the upper portion of the seed crystal.
• a solid liquid interface is main ⁇ tained in the lower chamber. Molten silicon contacts the inner walls of a central hole in the water-cooled partition.
• the Raymond method is particularly directed to the production of single crystal silicon and is limited to the production of relatively small quantities since the diameter of the hole in the annular partition must be kept relatively small to allow proper support of the molten silicon column.
• the patentees state that the inner walls of the annular partition are not wetted by molten silicon, it is likely that some molten silicon would contact these walls and become contaminated to a degree which is intolerable for many semiconductor device applications.
• cold crucibles are formed from a plurality of tubes which form a cage. Cooling fluid is circulated through the tubes to keep their surfaces cold and an electric induction coil is located outside of the cooling tubes to apply a high- frequency electromagnetic field to solid material located within the tubes.
• Such cold crucibles were originally employed in a crystal-growing technique known as the skull-melting technique because a very thin skull of solid material formed at the inner surface of the cooling tubes and all molten material was contained within this skull.
• OM such cold crucibles were employed to produce refractory oxides, such as hafnia, zirconia, sapphire and ruby.
• Rummel discloses in U. S. 3,759,670 the use of a cold crucible in much the same way but to form a molten mass of silicon from which a crystal of silicon can be pulled employing a seed crystal by the Czochralski method or any similar technique.
• Sterling et al. in ⁇ . 'S. 3,069,241 disclose a method for producing silicon in a cold crucible wherein an initial charge consisting of a silicon slug is introduced into a cold crucible, preheated to reduce its resistance and inductively heated by high-frequency alternating current to form a molten mass in the cold crucible. Silane gas is then bubbled through the molten silane from the bottom to build up the molten mass. When the molten mass reaches a certain level, the bubbling silane gas is discontinued and the crystal may be pulled by the Czochralski or other crystal pulling techniques. Silane gas is then used to regenerate the molten mass so that another crystal can be pulled.
• the invention relates to a method and apparatus for producing high purity-semiconductors, such as silicon.
• the apparatus comprises a controlled-atmosphere chamber with a cold crucible located therein.
• Means for applying a high-frequency electromagnetic field to semiconductor contained in the cold crucible are provided together with means for introducing vaporous semiconductor into the controlled-atmosphere chamber.
• Means for exhausting vaporous species from the chamber, means for cooling a portion of molten semiconductor contained within the cold crucible, and means for withdrawing solidified semiconductor product are also provided.
• the method comprises placing a charge of solid semiconductor in the cold crucible contained within the controlled-atmosphere chamber.
• the controlled-atmosphere
• OMP cha ber may be flushed with a protective atmosphere, such as argon, and the initial charge may be preheated to improve electrical coupling.
• a protective atmosphere such as argon
• the elec ⁇ tric coil positioned around the cold crucible is ener- gized to apply ' a high-frequency electromagnetic field which is sufficient to melt the initial charge of semi ⁇ conductor contained within the reaction zone of the cold crucible -and to partially levitate the molten semiconductor so that it does not contact the walls of the cold crucible.
• a vapor stream which contains the semiconductor to be produced in elemental form is intro ⁇ quizzed into the controlled-atmosphere chamber and thereby contacts exposed surfaces of the molten mass of semiconductor contained in a partially levitated state in the reaction zone of the cold crucible. At least a portion of the vaporous semiconductor is ab ⁇ sorbed by the molten semiconductor which adds to the • total molten mass present. Relative translational movement between the molten semiconductor mass and cold crucible is provided which causes a portion of the molten mass to be withdrawn from the heated reaction zone of the cold crucible after which it solidifies as solid semiconductor product.
• the method and apparatus for producing high purity semiconductors described herein has many significant advantages. Among these is the fact that the deposition rate of semiconductor is not temperature limited, as is the case with the heated filament technique for producing silicon. In fact, molten silicon contained within the cold crucible employed in this process can be superheated to provide even further acceleration of the process, if desired.
• the partial levitation achieved in the cold crucible has the major advantage of preventing silicon contami ⁇ nation due to contact with the crucible walls coupled with its effect of providing maximum surface area for contact between vaporized semiconductor compound and molten semiconductor compound. Thus, partial levitation operates to eliminate 1 the major drawback of all prior processes involving crucibles other than cold crucibles while maximizing surface area available for contact with silicon vapor which increases production capacity.
• Another major advantage is that the method de ⁇ scribed herein be run continuously, or quasi-continuously by extracting solidified silicon from the bottom of the cold crucible at a rate equal to the rate of deposi ⁇ tion of vaporized semiconductor feed.
• the diameter of the molten semiconductor mass, and there ⁇ fore the resultant solidified product is limited only by the inner dimensions of the cold crucible structure and the power of the induction heater. This offers far greater latitude in producing large volumes of material than other techniques as the heated silicon filament technique.
• FIG. 1 is a schematic illustration of an apparatus for producing high purity semiconductor ma ⁇ terial according to the cold crucible deposition process described herein.
• a controlled-atmosphere chamber is provided which may be formed from a fluid-cooled reaction chamber jacket 10 fabricated from stainless steel, quartz or similar high-temperature materials. Chamber 10 can be cooled by water or other cooling fluid which enters at a cooling fluid inlet 12, circulates through the reaction chamber jacket 10, and exits from cooling fluid outlet 14-. Jacket 10 is cooled in this manner to mini ⁇ mize deposition of vaporous feed materials or by-products on its inner surfaces.
• Cold crucible 16 is contained within reactor chamber 10. It can be formed from a plurality of ver ⁇ tically oriented annular tubes 18 arranged to form a cage. Typically, tubes 18 are connected to one or more manifolds 20 which supply water or other cooling fluid to tubes 18 or collect such fluids therefrom.
• cold crucible 16 can have a variety of con ⁇ figurations, a ' particularly convenient configuration is one similar to the cold crucible described in Wenckus et al., ⁇ . S. 4,049,384, the teachings of which are hereby incorporated by reference.
• Vaporous feed materials enter reaction chamber through inlet 22.
• Electric coil 26 surrounds cold crucible 16 and is used to apply a high-frequency electromagnetic field to semiconductor contained therein.
• a wide range of frequencies and powers are satisfactory.
• frequen ⁇ cies in the range of 200-250 KHz and applied powers of 25-50 KW are satisfactory. It should be noted that significant superheating cannot only be tolerated, but
• OMPI can be preferable in some cases.
• Pedestal " 28 is provided at the lower end of reac ⁇ tion chamber 10 to support a rod of solid semiconductor 30. Pedestal 28 may be moved up and down to move the semiconductor material longitudinally with respect to cold crucible 16.
• the shaft of pedestal 28 has a pressur tight seal with reaction chamber 10 so that the pressure within chamber 10 can be elevated or.reduced without leaks around the pedestal shaft.
• the apparatus is used as- follows.
• a solid charge of semiconductor material 30, such as a rod of poly- crystalline silicon, is placed on retractable pedestal 28. Pedestal 28 is then elevated to its upper most position. At this point, the reactor is flushed with a protective atmosphere such as argon, hydrogen, or a combination of both.
• solid semiconductor 30 is preheated to reduce its electrical resistance and permit and/or increase the efficiency of Rf coupling. This can be done by employing a radiant heater or by other known means. After preheating, coil 26 is energized and an Rf energy field is applied to heat solid semiconductor 30.
• molten semiconductors such as silicon do not contact the cold crucible walls if an appropriate field is applied, and thus, are referred to herein as being “partially levitated. " They are not totally levitated, of course, because their bottom portion rests on the solid semiconductor 30. The Rf input is adjusted to stabilize this partially levitated condition.
• vaporous feed is introduced through inlet 22 to the reaction chamber.
• Vaporous feed suitable for producing silicon would be a gaseous silicon com ⁇ pound, such as SiH., Sil, or SiBr..
• Any silicon compound is suitable as long as it is vaporous or vaporizable, capable of being purified to the degree required in the final semiconductor material, and as long as its breakdown products don't serve as impurities in the silicon being produced.
• carrier and/or diluent gases which don't interfere with the purity of the semiconductor being formed can be employed with the vaporous silicon feed.
• the vaporous feed such as SiH. gas
• the reaction chamber When the vaporous feed, such as SiH. gas, enters the reaction chamber and contacts hot molten silicon, it undergoes thermal cracking into pure silicon and vaporous by-products. Pure silicon vapor is absorbed by the molten silicon thereby adding to the mass of pure molten silicon.
• the method can be carried on continuously by lower ⁇ ing support pedestal 28 thereby extracting molten semi- conductor from cold crucible 16 whereupon it solidifies as part of solid semiconductor 30.
• Solid semiconductor 30 can be withdrawn from cold crucible" 16 and the reaction chamber, if desirable, at a rate of approximately equal to the rate of deposition of vaporous semiconductor feed into molten semiconductor 32.
• sensors could be used to monitor the height of the molten semiconductor column and to transmit a signal electronically to lower support pedestal 28.
• reaction- chambe 10 Gaseous by-products of the operation, as well as excess vaporous feed riot absorbed into the molten semi ⁇ conductor, can be exhausted through exhaust outlet 24.
• the pressure within reaction- chambe 10 can be maintained at atmosphereic pressure, or in the alternative can be elevated or reduced. It may be desirable in some cases, for example, to run the process at elevated pressure to obtain more throughput for a given reaction chamber size. On the other hand, reduced pressures may also be desirable under some circumstances, particu ⁇ larly if it is desirable to minimize the formation of a boundary layer of gas around the surface of the molten semiconductor. In cases where elevated or reduced pressures are employed, appropriate pressure-tight- seals should be employed at locations where elements extend through the walls of. reaction chamber 10 to prevent leaks out of or into reaction chamber 10.
• This invention has industrial applicability in the production of high purity semiconductors.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Crystallography & Structural Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Inorganic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Silicon Compounds (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)

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• 1980
  • 1980-01-18 WO PCT/US1980/000046 patent/WO1980001489A1/en unknown
  • 1980-07-29 EP EP80900353A patent/EP0023509A1/de not_active Withdrawn

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