US3175891A - Method for the production of dislocation-free monocrystalline silicon by floating zone melting - Google Patents

Method for the production of dislocation-free monocrystalline silicon by floating zone melting Download PDF

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Publication number
US3175891A
US3175891A US157033A US15703361A US3175891A US 3175891 A US3175891 A US 3175891A US 157033 A US157033 A US 157033A US 15703361 A US15703361 A US 15703361A US 3175891 A US3175891 A US 3175891A
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United States
Prior art keywords
zone
seed crystal
silicon rod
rod
melting
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Expired - Lifetime
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US157033A
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English (en)
Inventor
Kelier Wolfgang
Ziegler Gunther
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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
    • C30B13/00—Single-crystal growth by zone-melting; Refining by zone-melting
    • C30B13/28—Controlling or regulating
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H85/00—Protective devices in which the current flows through a part of fusible material and this current is interrupted by displacement of the fusible material when this current becomes excessive
    • H01H85/02—Details
    • H01H85/38—Means for extinguishing or suppressing arc
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H85/00—Protective devices in which the current flows through a part of fusible material and this current is interrupted by displacement of the fusible material when this current becomes excessive
    • H01H85/02—Details
    • H01H85/38—Means for extinguishing or suppressing arc
    • H01H2085/386—Means for extinguishing or suppressing arc with magnetic or electrodynamic arc-blowing
    • 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
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10T117/10—Apparatus
    • Y10T117/1024—Apparatus for crystallization from liquid or supercritical state
    • Y10T117/1076—Apparatus for crystallization from liquid or supercritical state having means for producing a moving solid-liquid-solid zone
    • 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
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10T117/10—Apparatus
    • Y10T117/1024—Apparatus for crystallization from liquid or supercritical state
    • Y10T117/1076—Apparatus for crystallization from liquid or supercritical state having means for producing a moving solid-liquid-solid zone
    • Y10T117/1084—Apparatus for crystallization from liquid or supercritical state having means for producing a moving solid-liquid-solid zone having details of a stabilizing feature
    • 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
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10T117/10—Apparatus
    • Y10T117/1024—Apparatus for crystallization from liquid or supercritical state
    • Y10T117/1076—Apparatus for crystallization from liquid or supercritical state having means for producing a moving solid-liquid-solid zone
    • Y10T117/1088—Apparatus for crystallization from liquid or supercritical state having means for producing a moving solid-liquid-solid zone including heating or cooling details

Definitions

  • dislo- 40 cations may cause a non-uniform alloy formation or nonuniform depth of penetration of the alloy being formed. It is, therefore, desirable to avoid the occurrence of dis locations.
  • the seed crystal used for crucible-free zone melting operations of the above-mentioned type can be given a considerably smaller cross section than the semiconductor rod to which the seed is attached.
  • the axial temperature gradient from the semiconductor rod to the seed crystal becomes considerably more shallow which in turn results in a reduction of any dislocations and considerable reduction in the possibility that dislocations may grow from the seed crystal into the semiconductor rod.
  • a silicon rod such as any polycrystalline rod
  • crucible-free zone melting while the rod is vertically mounted between holders and a melting zone is repeatedly passed from one end of the rod to the other, always commencing at an end where a monocrystalline seed crystal is used together with the rod.
  • the seed crystal is given a considerably smaller cross section than the rod to be converted, and all zone-melting passes are commenced in the seed crystal.
  • the traveling speed of the zone in the seed crystal is kept between 7 and mm. per minute, and the silicon cross section at the junction of seed and rod is contracted. by temporarily pulling the rod ends apart at a speed greater than mm. per minute.
  • FIG. 1 is a partial sectional and perspective View of apparatus for carrying out the instant process.
  • FIG. 2 shows a detail of the instant invention.
  • the housing 2 of the apparatus shown in FIG. 1 generally has the shape of a vertical elongated prism of approximately square cross section.
  • the front wall of the housing is formed by a closure plate 3 which forms the door.
  • the walls of the housing as well as the door are preferably provided with cooling means consisting, for example, of copper tubing (not illustrated) soldered to the walls and the door in order to pass a flow of cooling water through the tubes during operation of the device.
  • An inspection window extends approximately the entire length of the semiconductor rod to be processed and permits observation of the zone-melting operation.
  • a duct 4 for connection to a Vacuum-pump device 5 is mounted on the rear wall of the housing and thence communicates with the interior of the housing through an opening 4a of large diameter and extending over the predominant portion of the horizontal housing width.
  • the opening 4a and the exhaust duct 4 are both located above the bottom surface of the vacuum chamber so that any particles or substances dropping into the bottom of the device cannot enter into the vacuum equipment.
  • the silicon semiconductor rod 6 is mounted in the processing chamber by means of two holders '7 of which with clamping screws 7b and are mounted in vertical coaxial alignment on respective coaxial shafts 8 and 8awhich pass through respective vacuum-type sealing bushings 8b and 8c of the housing bottom and top to the outside where they are connected with driving and control devices (not shown) which permit displacing the holders longitudinal and/or imparting rotation thereto.
  • the device is further provided with a ring-shaped zone heater consisting of a flat induction coil 11 mounted on terminal blocks 12 of a shifting device 13 which permits movement of the axially narrow heater 11 vertically along rod 6 in order to melt a correspondingly narrow zone of the rod and to displace the molten zone gradually along the rod axis.
  • a semicircular shield 14 of sheet metal protects the device 13 from heat radiation coming from the molten zone and also from deposition 'of evaporated material. Details of the heater and shifting (displacing) device,
  • a gripper device comprising two vertical shafts 18, 18a is mounted along another edge of the prismatic processing chamber, preferably and as shown, near one of the two edges remote from the door.
  • Gripper 15 is fastened by means of set screws to shaft 13 and is longitudinally displaceable so that it can be secured to any desired height.
  • Shaft 18a carries a similar gripper device (not shown) which is likewise longitudinally displaceable.
  • the shafts 18 and 18a carry respective spur gears both shown at 19 which are in mesh with each other and are driven from the outside.
  • the ends of the grippers are both provided with tubular pieces 16 of heat resistant and wear resistant material, which is preferably quartz.
  • the door-like closure plate 3 carries a rubber gasket 28' which is fitted in a swallow-tail groove or otherwise fastened to the door.
  • the door is joined with the housing by double-type hinges 21 whose two hinge axes are approximately located in the plane of the door when the door is closed and tightened. This alfords obtaining a vacuum-tight sealing of the door under the effect of ambient pressure without encountering lateral displacement of the door as a consequence of pressure changes.
  • the door is provided with a handle (not shown) and an observation window 30.
  • FIG. 2 shows a semiconductor rod 6 in which a molten zone 10 is located.
  • the zone is produced by the heater device, which is, for example, an induction winding 11.
  • 22 is a seed crystal fused to the lower end of the silicon rod 6 and 23 is a melt-down portion as will be further described hereinbelow.
  • the induction winding 11 is energized with high-frequency current for example 4 megacycles per second and is preferably a flat spiral coil as illustrated. This has the advantage that the melting zone can be given a particularly short dimension in the axial direction of the rod, induction winding 4 can be guided along the entire length of the rod wit-h the aid of a transporting or shifting device 13.
  • the seed crystal 22 which is fused to the lower end of silicon rod 6 has a considerably smaller cross section than the silicon rod.
  • the silicon rod 6 may have a diameter of 12 mm. and a seed-crystal diameter of 3 to The upper end of rod 6 as Well as the lower end of the seed crystal 22 are clamped in respective holders'of which one is shown. These holders can be moved relative to one another in the axial direction of the rod.
  • a hyperpure silicon rod d of such extreme purity that it is practically non-conducting at room temperature.
  • the further heating can then be effected with the aid of the heater winding 11 by high-frequency current.
  • the preheating c-an be effected by heat radiation, or by mounting a conducting material, for example a body of molybdenum, at the upper clamping or holding location of the silicon rod 6, which conducting body can then be heated by means of the induction winding 11 and in turn heats the adjacent semiconductor material by heat conductance.
  • the entire method is preferably performed in a highvacuum chamber (as shown) but can also be performed under a protective gas atmosphere.
  • a glowing zone is passed downwardly through the silicon rod 6 until it reaches the fusion point of the seed crystal 22. At this point the silicon rod is subjected to sufiicient heating until the seed crystal 22 becomes molten. It is preferable to give the junction between the thick silicon rod 6 and the thin seed crystal 22 tl1c shape of a cone as shown on the drawing.
  • the melting zone is passed upwardly through the entire silicon rod up to its upper end. Thereafter a glowing zone is passed downwardly back to the seed crystal, and this method is repeated several times.
  • the travel speed of the heater winding during upward motion of the melting zone may be for example, 3 mm. per minute, Whereas the downward return motion of a glowing but solid zone may occur at a much higher speed, for example of 260 mm. per minute.
  • the last zone-melting pass is performed in the fol-lowing manner.
  • the glow zone traveling downward, has arrived at the seed crystal, the travel motion of the heater winding is stopped, but the heating by high-frequency current is continued.
  • the heater winding 4 is moved upward at a speed greater than 5 per minute, for example 10 mm. per minute.
  • the melting zone reaches the location 23 at which the seed crystal 22 merges with the shallow conical portion of the rod 6, the, rod ends are moved apart at a speed of at least 25 mm. per minute until the diameter of the silicon rod at this location is narrowed down to about 2 mm.
  • the travel speed of the heater winding is continuously reduced. This continuous reduction preferably extends over the length of the conical portion of the rod.
  • the travel speed of the heater winding has become less than 7 mm. per minute, and is for example 4 mm. per minute. This speed is then kept constant until the melting zone has reached the upper end of the rod. If one of the rod holders, for example the lower one, is placed in rotation during zone melting, such rotation must be free of vibration. Otherwise, such rotation must be discontinued during the last zone-melting pass in order to prevent jarring.
  • Silicon monocrystals produced by the method described above were found to be completely free of dislocations.
  • a process for producing dislocation-free monocrystalline silicon by crucible-free zone meiting which comprises:
  • step (e) repeating step (d) several times:
  • step (d) commencing the last repetition of step (d) in the seed crystal at a rate between 7 and mm. per minute;
  • step (7) as the molten zone of step (7) moves through the junction of said seed crystal and said silicon rod, moving the end of said seed crystal and said silicon rod axially apart at a rate above mm. per minute, to produce a contracted cross section of about 2 mm.;
  • a process for producing dislocation-free monocrystalline silicon by crucible-free zone melting which comprises:
  • step (e) repeating step (d) several times;
  • step (d) commencing the last repetition of step (d) in the seed crystal at a rate between 7 and 15 mm. per
  • step (1) moves through the junction of said seed crystal and said silicon rod, moving the end of said seed crystal and said silicon rod axially apart at a rate above 25 mm. per minute, to produce a contracted cross section of about 2 mm;
  • step (g) (12) after the said contracted cross section of step (g) is produced, stopping the axial movement of said silicon rod and seed crystal;
  • a process for producing dislocation-free monocrystalline silicon by crucible-free zone melting which comprises:
  • step (e) repeating step (d) several times;
  • step (d) commencing the last repetition of step (d) in the seed crystal at the rate between 7 and 15 mm. per minute;
  • step (1) moves through the junction of said seed crystal and said silicon rod, moving the end of said seed crystal and said silicon rod axially apart at a rate above 25 mm. per minute, until a contracted cross section of about 2 mm. is produced;
  • step (g) after the said contracted cross section of step (g) is produced, stopping the axial movement of said silicon rod and seed crystal;
  • a process for producing dislocation-free monocrystalline silicon by crucible-free zone melting which comprises:
  • step (e) repeating step (:1) several times;
  • step (d) commencing the last repetition of step (d) in the seed crystal at a rate between 7 and 15 mm. per minute;
  • step (1) as the molten zone of step (1) moves through the junction of said seed crystal and said silicon rod, temporarily moving the end of said seed crystal and said silicon rod axially apart at a rate above 25 mm. per minute, until a contracted cross section of about 2 mm. is produced;
  • step (g) (/1) after the said contracted cross section of step (g) is produced, stopping the axial movement of said silicon rod and seed crystal;

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Silicon Compounds (AREA)
  • Fuses (AREA)
US157033A 1960-11-25 1961-11-24 Method for the production of dislocation-free monocrystalline silicon by floating zone melting Expired - Lifetime US3175891A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DES71415A DE1128413B (de) 1960-11-25 1960-11-25 Verfahren zur Herstellung von zersetzungsfreiem einkristallinem Silicium durch tiegelfreies Zonenschmelzen

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Publication Number Publication Date
US3175891A true US3175891A (en) 1965-03-30

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US157033A Expired - Lifetime US3175891A (en) 1960-11-25 1961-11-24 Method for the production of dislocation-free monocrystalline silicon by floating zone melting

Country Status (7)

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US (1) US3175891A (xx)
BE (1) BE610603A (xx)
CH (1) CH395554A (xx)
DE (1) DE1128413B (xx)
GB (2) GB926487A (xx)
NL (2) NL266876A (xx)
SE (1) SE306303B (xx)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3972684A (en) * 1972-10-03 1976-08-03 Elphiac Apparatus for fabricating monocrystals
US4042454A (en) * 1973-11-12 1977-08-16 Siemens Aktiengesellschaft Method of producing homogeneously doped n-type Si monocrystals by thermal neutron radiation

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL6411697A (xx) * 1963-10-15 1965-04-20
DE1224273B (de) * 1964-06-23 1966-09-08 Siemens Ag Vorrichtung zum tiegelfreien Zonenschmelzen

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3972684A (en) * 1972-10-03 1976-08-03 Elphiac Apparatus for fabricating monocrystals
US4042454A (en) * 1973-11-12 1977-08-16 Siemens Aktiengesellschaft Method of producing homogeneously doped n-type Si monocrystals by thermal neutron radiation

Also Published As

Publication number Publication date
GB926487A (en) 1963-05-22
SE306303B (xx) 1968-11-25
BE610603A (fr) 1962-05-22
CH395554A (de) 1965-07-15
NL139006B (nl) 1973-06-15
DE1128413B (de) 1962-04-26
NL266876A (xx)
GB926497A (en) 1963-05-22

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