US3113841A - Floating zone melting method for semiconductor rods - Google Patents

Floating zone melting method for semiconductor rods Download PDF

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Publication number
US3113841A
US3113841A US23490A US2349060A US3113841A US 3113841 A US3113841 A US 3113841A US 23490 A US23490 A US 23490A US 2349060 A US2349060 A US 2349060A US 3113841 A US3113841 A US 3113841A
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US
United States
Prior art keywords
rod
silicon
zone
carbon
melting
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Expired - Lifetime
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US23490A
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English (en)
Inventor
Reuschel Konrad
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Siemens Schuckertwerke AG
Siemens AG
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Siemens AG
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    • 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
    • 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
    • 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
    • C30B13/00—Single-crystal growth by zone-melting; Refining by zone-melting
    • C30B13/16—Heating of the molten zone
    • C30B13/20—Heating of the molten zone by induction, e.g. hot wire technique
    • 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10S117/90—Apparatus characterized by composition or treatment thereof, e.g. surface finish, surface coating

Definitions

  • This method is employed, for example, in the production of hyperpure monocrystalline rods of silicon or other semiconductor substances or for pulling semiconductor cores of small cross section.
  • the rod-shapecl semiconductor material is preferably mounted vertically in holding means within a vacuum chamber.
  • a coil heated by high-frequency alternating current is moved along the rod axis, the rod being thereby melted throughout a narrow cross-sectional zone which in this manner can be passed through the rod, repeatedly if desired, in one and the same direction.
  • the semiconductor rod In order to initiate the zone-melting operation the semiconductor rod must first be preheated, because the slight conductance of the already extremely pure semiconductor material is not sufficient for inductive heating when the rod is cold.
  • a closed ring of tungsten or molybdenum sheet material or the like disposed around the semiconductor rod, at one end thereof. Such a ring is inductively heated by the above-mentioned heater coil and transmits the heat by radiation to the rod.
  • a spring for example of molybdenum, may be placed upon the semiconductor rod at one end thereof, to serve not only for clamping the rod fast in the holder but also to preheat the rod end by radiation and heat conductance when the spring is subjected to inductive heating by the said coil.
  • I provide one end of the semiconductor rod, which was preferably produced by precipitation from a gaseous compound, with a comparatively small body of hyperpure carbon, for example spectral carbon or hyperpure graphite.
  • the latter is fused together with the semiconductor material, or is otherwise joined with or molded into the rod end.
  • This terminal body of the rod has a much better electric conductance than the semiconductor material.
  • the hyperpure silicon is produced by precipitation from a gaseous silicon compound.
  • a gaseous silicon compound Such process is described in the copending application of Schweikert et 211., Serial No. 665,086, filed June 11, 1957, now Patent No. 3,011,877, and in my herewith cofiled application, Serial No. 23,524, filed April 20, 1960, now Patent No. 2,997,735.
  • a thin rod-shaped silicon core upon which further amounts of silicon are to be precipitated, by heat decomposition or reduction of the gaseous silicon compound is in most cases not inserted directly into the cooled holder that serves as conductor for the supply of electric current passing through the rod.
  • Silicon is therefore also precipitated upon the said rod end, and tightly envelopes this end.
  • the resulting fast bond of the carbon or graphite piece with the semi conductor material then permits an especially simplified method and means for the desired rapid heating-up of the silicon rod during the subsequent crucible-free zone melting.
  • the silicon rod, with the adherent piece of carbon is then mounted in the Zone-melting equipment, and the carbon piece is first heated inductively to a sulfieiently high temperature to place the adjacent silicon in incandescent condition.
  • the adjacent silicon thus becomes electrically good conducting, and hence capable of being heated inductively.
  • the heating power is at first kept so small that the silicon does not melt, and while supplying such heating power the good conducting zone is first moved to the other end of the rod. At that locality the heating power supplied to the inductive heater is increased and the glowing zone of silicon is melted. While this takes place, the silicon rod is preferably joined by melting to a seed piece of the same silicon material which is clamped fast in the adjacent holder.
  • the clamped piece may consist of a monocrystalline seed, so that the semiconductor rod is converted into a monocrystal by the subsequent zone-melting operation.
  • the invention will be further explained with reference to a preferred embodiment of an apparatus employed for its performance, as illustrated in the accompanying drawing.
  • the illustration is fragmentary but will be readily understood by persons skilled in the art or persons having knowledge of the many publications now available on zone melting of semiconductors.
  • the evacuated housing usually employed is not shown, and also the lower holder for the silicon rod and the customary mechanism for relative lengthwise displacement of the induction heating coil and said rod.
  • the drawing illustrates the upper portion of an elongated thickened cylindrical semiconductor rod 2 produced by precipitation of silicon from a gaseous silicon compound onto an original thin core rod 3 of the same silicon material.
  • the thin silicon rod 3 was originally inserted into the axial center bore of an intermediate cylindrical piece of high-purity carbon 4, preparatory to said precipitation. During the said preceding precipitation process the thin rod 3 is thickened, thus producing thick rod 2, and causing the dotted end of the carbon piece 4 to become solidly embedded in the end of the thick rod 2.
  • the carbon piece 4 thus attached to the rod 2 is inserted into a cylindrical rod holder 5, the inner diameter of the latter being sufficiently large to accommodate the intermediate carbon 3 piece 4 with a sliding fit.
  • the carbon piece 4 is firmly secured to the holder 5 by means of screws 6. It will be understood that the lower end of the rod 2 (not shown) is inserted and clamped in a corresponding holder which, however, may remain fixed during the zone-melting operation.
  • the rod holder 5 is connected with a drive shaft 7 which rotates the upper portion of the silicon rod during the zone-melting operation.
  • the latter is to be carried out within a vacuum vessel (not shown).
  • the device is provided with a heating coil 8 to be supplied with highfrequency alternating current.
  • the coil is designed as a flat spiral with three winding turns. It surrounds the carbon piece 4 and can be displaced in the direction of the rod axis by the customary means.
  • the coil 3 may consist of silver tubes, which during operation are traversed by cooling water supplied through bores of the current-supply terminals 9.
  • the invention offers the advantage that the silicon rod 2 can be inductively heated to the operating temperature within a shorter time than heretofore required and without any additional auxiliary means, that is exclusively with the aid of the heating coil 8 of the floating zone melting operation. Only a few seconds are required to inductively heat the intermediate carbon piece 4 to a temperature at which the adjacent end of the silicon rod 2 commences to glow. The glowing zone is then shifted toward the other end of the silicon rod by downward displacement of the terminal and coil assembly 89 until the glowing zone reaches the end point where a crystal seed is to be bonded to the rod 2. When the zone melting serves for drawing the rod to a thinner diameter, the glowing zone is run downward to the free rod end. Said drawing of the rod is accomplished by employing known devices for displacing the opposite holders away from each other.
  • the intermediate carbon piece 4 is preferably given a circular cross section of a predetermined diameter.
  • the semiconductor rod 2 can readily be placed into the holder 5 whose bore matches the cross section of the carbon piece, thus greatly reducing the amount of time required for the preparatory work, as compared with the time required for mounting the auxiliary devices heretofore required for preheating the silicon rod.
  • the method also results in saving of semiconductor material because, as explained in the introductory part of this specification, heretofore the preheating of the rod required the use of molybdenum springs, or like auxiliary devices, which covered an appreciable portion of the rod end and thus prevented this end from being processed by zone melting.
  • the temperature of inductive heating is increased by correspondingly increasing the high-frequency currents supplied to the heater coil 8, thus causing a narrow zone of the rod 2 to melt, this zone being thereafter shifted upwardly toward the carbon piece 4 by upward displacement of the coil assembly 8.
  • a method of crucible-free floating zone melting of a silicon rod in which the rod is supported in a vertical position, and a transversely extending molten zone is formed in the rod by inductive heating, the melt being supported by adherence to the adjacent solid rod portions, and in which said zone is caused to move lengthwise of the rod
  • said zone melting comprising previously precipitating silicon upon a silicon rod and about an end portion of a piece of hyperpure carbon attached to said silicon rod, so that one end of said carbon end portion becomes embedded in precipitated silicon, attaching the exposed end of said carbon end portion to a support and supporting the silicon rod in the zone melting in vertical position, and initiating the zone melting process by inductive heating of said carbon end portion sufficient to heat the adjacent end portion of the silicon rod to a temperature causing a zone thereof to become electroconductive and heatable by electric induction but not to melt it, and displacing the said Zone away from the carbon and thereafter raising the temperature of said zone to melting temperature.
  • the improvement in said zone melting comprising first precipitating the silicon upon a silicon rod and about an end portion of a piece of hyperpure carbon attached to said silicon rod by passing an electric current through the said silicon rod and attached piece of carbon to heat the rod, and passing a gaseous compound of silicon in contact with the heated rod to decompose the compound to silicon and one end of the carbon end portion becomes embedded in the precipitated silicon, thereafter attaching the exposed end of said carbon end portion to a support to support the silicon rod in a Zone-melting apparatus in vertical position, initiating the zone-melting process by inductive heating of the carbon end portion sufficient to heat the adjacent end portion of the silicon rod to a temperature causing a zone thereof to become electroconductive

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Inorganic Chemistry (AREA)
  • Silicon Compounds (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
US23490A 1959-05-08 1960-04-20 Floating zone melting method for semiconductor rods Expired - Lifetime US3113841A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DES62919A DE1094711B (de) 1959-05-08 1959-05-08 Verfahren zum tiegelfreien Zonenschmelzen von Halbleiterstaeben, insbesondere aus Silizium

Publications (1)

Publication Number Publication Date
US3113841A true US3113841A (en) 1963-12-10

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US23490A Expired - Lifetime US3113841A (en) 1959-05-08 1960-04-20 Floating zone melting method for semiconductor rods

Country Status (6)

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US (1) US3113841A (sk)
CH (1) CH386116A (sk)
DE (1) DE1094711B (sk)
FR (1) FR1261240A (sk)
GB (1) GB907764A (sk)
NL (2) NL251304A (sk)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3241924A (en) * 1960-02-05 1966-03-22 Philips Corp Devices for carrying out rotary movements under the action of magnetic forces
US3251658A (en) * 1963-02-26 1966-05-17 Monsanto Co Zone refining start-up
US3275417A (en) * 1963-10-15 1966-09-27 Texas Instruments Inc Production of dislocation-free silicon single crystals
US3310384A (en) * 1964-06-23 1967-03-21 Siemens Ag Method and apparatus for cruciblefree zone melting
US3351433A (en) * 1962-12-12 1967-11-07 Siemens Ag Method of producing monocrystalline semiconductor rods
US3522014A (en) * 1965-11-30 1970-07-28 Siemens Ag Eccentrically rotated rod holder for crucible-free zone melting
US3901499A (en) * 1973-05-07 1975-08-26 Siemens Ag Mounting device for crystalline rods

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL258961A (sk) * 1959-12-23
DE1209550B (de) * 1961-03-20 1966-01-27 Licentia Gmbh Halterung fuer zonenzuschmelzende Staebe

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2792317A (en) * 1954-01-28 1957-05-14 Westinghouse Electric Corp Method of producing multiple p-n junctions
US2855335A (en) * 1955-01-14 1958-10-07 Int Standard Electric Corp Method of purifying semiconductor material
US2901325A (en) * 1955-07-22 1959-08-25 Bell Telephone Labor Inc Method of preparing silicon
US2972525A (en) * 1953-02-26 1961-02-21 Siemens Ag Crucible-free zone melting method and apparatus for producing and processing a rod-shaped body of crystalline substance, particularly semiconductor substance
US2990261A (en) * 1958-12-11 1961-06-27 Bell Telephone Labor Inc Processing of boron compact
US3011877A (en) * 1956-06-25 1961-12-05 Siemens Ag Production of high-purity semiconductor materials for electrical purposes

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1119039A (fr) * 1954-03-09 1956-06-14 Siemens Ag Procédé pour la préparation d'un corps cristallin, en particulier d'un corps semiconducteur

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2972525A (en) * 1953-02-26 1961-02-21 Siemens Ag Crucible-free zone melting method and apparatus for producing and processing a rod-shaped body of crystalline substance, particularly semiconductor substance
US2792317A (en) * 1954-01-28 1957-05-14 Westinghouse Electric Corp Method of producing multiple p-n junctions
US2855335A (en) * 1955-01-14 1958-10-07 Int Standard Electric Corp Method of purifying semiconductor material
US2901325A (en) * 1955-07-22 1959-08-25 Bell Telephone Labor Inc Method of preparing silicon
US3011877A (en) * 1956-06-25 1961-12-05 Siemens Ag Production of high-purity semiconductor materials for electrical purposes
US2990261A (en) * 1958-12-11 1961-06-27 Bell Telephone Labor Inc Processing of boron compact

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3241924A (en) * 1960-02-05 1966-03-22 Philips Corp Devices for carrying out rotary movements under the action of magnetic forces
US3351433A (en) * 1962-12-12 1967-11-07 Siemens Ag Method of producing monocrystalline semiconductor rods
US3251658A (en) * 1963-02-26 1966-05-17 Monsanto Co Zone refining start-up
US3275417A (en) * 1963-10-15 1966-09-27 Texas Instruments Inc Production of dislocation-free silicon single crystals
US3310384A (en) * 1964-06-23 1967-03-21 Siemens Ag Method and apparatus for cruciblefree zone melting
US3522014A (en) * 1965-11-30 1970-07-28 Siemens Ag Eccentrically rotated rod holder for crucible-free zone melting
US3901499A (en) * 1973-05-07 1975-08-26 Siemens Ag Mounting device for crystalline rods

Also Published As

Publication number Publication date
NL112832C (sk)
DE1094711B (de) 1960-12-15
NL251304A (sk)
FR1261240A (fr) 1961-05-19
GB907764A (en) 1962-10-10
CH386116A (de) 1964-12-31

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