US3177051A - Method of treating meltable material by floating zone-melting - Google Patents

Method of treating meltable material by floating zone-melting Download PDF

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Publication number
US3177051A
US3177051A US115757A US11575761A US3177051A US 3177051 A US3177051 A US 3177051A US 115757 A US115757 A US 115757A US 11575761 A US11575761 A US 11575761A US 3177051 A US3177051 A US 3177051A
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United States
Prior art keywords
zone
rod
region
molten
zones
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Expired - Lifetime
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US115757A
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English (en)
Inventor
Scholte Joannes Wilhel Andreas
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US Philips Corp
North American Philips Co Inc
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US Philips Corp
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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
    • C30B13/06—Single-crystal growth by zone-melting; Refining by zone-melting the molten zone not extending over the whole cross-section

Definitions

  • Floating zone-melting methods are known also, in which a partial molten zone is passed through a rod, by which is understood here a zone which does not occupy the whole cross-section of the rod but in which a preferably eccentric part thereof, hereinafter termed unmelted core, remains in the solid state so that the parts of the rod on either side of such a partial zone are permanently linked together.
  • a zone which does not occupy the whole cross-section of the rod but in which a preferably eccentric part thereof, hereinafter termed unmelted core, remains in the solid state so that the parts of the rod on either side of such a partial zone are permanently linked together.
  • it has been proposed in addition to pass the zone through the rod along a helical line having a short pitch In order to purify the material throughout its cross-section by passing one partial zone, it has been proposed in addition to pass the
  • the invention which consequently relates to a method of zone-melting a rod without the use of a crucible, in which two or more partial zones are simultaneously passed through the rod in the longitudinal direction, has inter alia for its object to miti ate the above drawbacks.
  • these zones in the longitudinal direction of the rod which is in a vertical position, overlap each other in a manner such that together they cover at least once the whole cross-section of the rod.
  • more than two partial molten zones are simultaneously passed through the rod, in which each time two successive zones together cover at least the whole cross-section of the rod.
  • the non-melted cores associated with two successive zones are preferably situated on either side of the axis of the red but may also be arranged in a different manner.
  • a complete molten zone situated behind the other zones is also passes through the rod so as to remove inhomogeneities, if any.
  • each partial zone will be the surest Patented Apr. 6, 19%5 larger according as an area of the cross-section of the unmelted core associated with each zone is smaller.
  • this area should be large enough to form a rigid connection between the parts of the rod on either side of the zone.
  • this area is at most one fourth and at least one'hundredth of the area of the cross-section of the rod. lit has appeared that for practical purposes the choice from one tenth to one twentieth is readily usable.
  • FIGURE 1 diagrammatically shows a vertical sectional view of a device for floating zone melting
  • FIGURE 2 is a horizontal sectional view of this device taken along the line Ill-11 of FIGURE 1.
  • FIGURE 1 is a vertically provided rod-shaped body of meltable material, such as a meltable metal or semi-conductive material, for example silicon, which is rigidly secured at its upper end to a holder 2 and at its lower end to a holder 3.
  • the device further comprises four coils which are connected to a high-frequency generator not shown.
  • the coils 4, 5 and 6 enclose a plane of a somewhat elongated shape (see FIGURE 2) and are provided eccentrically with respect to the axis of the rod, shown in FIGURE 1 by the dot and dash line X-X, while the smaller lower coil 7 is circular and provided coaxially with respect to this axis of the rod.
  • the coils 4 and 6 are provided strai ht below one another, while the coil 5 assumes a position with respect to these coils shifted through an angle of 180 about the axis X-X of the rod.
  • coil 7 may have a diameter of 35 mm. and the-longer and shorter dimensions of the coils 4 to 6 may be 55 and 35 mm. respectively. As shown in FIGURE 2, the coils 4 to 6 may be arranged so that the rod 1 is approximately concentric with one end of the coil.
  • the coils are connected in series but they may alternatively be connected in a different manner, if desired. They are preferably connected so that the highfrequency current from the generator will flow through each pair of successive coils in a mutually opposite dire"- tion of rotation.
  • the set of coils is gradually moved upwards with respect to that rod.
  • a typical rate for moving all of the coils for silicon may be about 0.2 cm. a minute.
  • the molten zones transverse successive the rod-shaped body from the bottom to the top.
  • the parts of the rod 15, I6 and 17 lying between the zones are firmly connected to the uppermost part of the rod 18 which is attached to the holder 2 by the unrnelted cores l2, l3 and 14 while the part of the rod 3.? connected to the lower holder 3 is separated from the uppermost parts by the molten zone 11.
  • the holder 3 with the part of the rod 19 may be rotated, if desired.
  • the holder 2 with the parts l518 connected to it is not rotated.
  • the materialof the core 12 is melted again by the zone 9, the material of the core 13 by the zone 10, and the material of the core 14 by the zone 11.
  • the concentration change of an impurity in this material after passing each zone is to be indicated by a constant factor per zone, the so-called reduction factor at.
  • This concentration change may be'the result of segregation and/ or evaporation of the impurity.
  • V the reduction factor at has a different value for each impurity in the meltable material. In general, it will be smaller than unity.
  • the concentration of an impurity in the treated material will have become a value of aC in which formula C is the initial concentration of the impurity.
  • partial molten zones are used which only partly occupy the cross-section of the rod.
  • the relation between the area of the cross-section of the unmelted core of each of these partial zones and the area of the total cross-section of the rod is indicated by the factor x.
  • the factor x is the same for all the partial zones.
  • the partial zones are chosen so that each pair of successive zones occupies at least the whole cross-section of the rod and three of such partial zones are used.
  • Table I the concentrations of an impurity after passing each of these zones is summarized in formulae.
  • a rod-like body of meltable material selected from the group consisting of metals and semiconductors comprising the steps of supporting the body in a vertical position, establishing in a first transverse region of the body a first molten zone that occupies more than half but less than the whole cross sectional area of the body leaving a first solid unmelted region in said first transverse region, establishing in a second transverse region of the body spaced above the first transverse region a second molten zone that lies directly above the first unmelted region adjacent the first molten zone and that also occupies more than half but less than the whole cross sectional area of the body at the second transverse region leaving a second solid unmelted region in the said second transverse region that lies directly above the first molten zone, and simultaneously passing the two spaced molten zones longitudinally through the body maintaining the overlying relationship of the molten zones and unmelted regions in the different transverse regions such that the molten zone in each transverse region sweeps through the same section of the rodlike body that remains unmelted in the other transverse region
  • a method as set forth in claim 1 wherein there is established, spaced from the other molten zones, a third molten zone that occupies the whole cross sectional area of the body, and all three molten zones are simultaneously passed through the body in a direction such that the third molten zone follows after the first and second zones.
  • a method of floating-zone melting and treating of a rod-like body of meltable material selected from the group consisting of metals and semiconductors and having a longitudinal axis comprising the steps of supporting the body in a vertical position, establishing in a first transverse region of the body a first molten zone that occupies more than half but less than the whole cross sectional area of the body leaving a first solid unmelted region in the first transverse region located off the longitudinal axis, establishing in a second transverse region of the body spaced above the first transverse region a second molten zone that lies directly above the first unmelted region adjacent the first molten zone and that also occupies more than half but less than the whole cross sectional area of the body atthe second transverse region leaving a second solid unmelted region in the second transverse region that lies directly above the first molten zone and is also located 1 off the longitudinal axis, and simultaneously passing the two spaced molten zones longitudinally through the body maintaining the overlying relationship of the molten zones and unmelted regions in the mol

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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)
  • General Induction Heating (AREA)
  • Liquid Deposition Of Substances Of Which Semiconductor Devices Are Composed (AREA)
  • Manufacture And Refinement Of Metals (AREA)
US115757A 1960-06-28 1961-06-08 Method of treating meltable material by floating zone-melting Expired - Lifetime US3177051A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3271118A (en) * 1961-10-18 1966-09-06 Monsanto Co Seed crystals and methods using the same
US3449087A (en) * 1966-06-27 1969-06-10 Commerce Usa Purification by selective crystallization and remelt
US3622280A (en) * 1967-04-29 1971-11-23 Siemens Ag Adjustable heating device for crucible-free zone melting a crystalline rod
US3773499A (en) * 1968-04-03 1973-11-20 M Melnikov Method of zonal melting of materials
US4126509A (en) * 1975-11-14 1978-11-21 Siemens Aktiengesellschaft Process for producing phosophorous-doped silicon monocrystals having a select peripheral dopant concentration along a radial cross-section of such monocrystal

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2692995C (en) 2010-02-01 2016-06-28 Kudu Industries Inc. A system and method for induction heating a helical rotor using a coil
CN112357894A (zh) * 2020-11-17 2021-02-12 昆明理工大学 一种粗碲结晶提纯方法

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3023091A (en) * 1959-03-02 1962-02-27 Raytheon Co Methods of heating and levitating molten material

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE510303A (en)) * 1951-11-16
DE1062431B (de) * 1953-02-14 1959-07-30 Siemens Ag Verfahren und Vorrichtung zum Umschmelzen von langgestreckten Koerpern durch Zonenschmelzen

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3023091A (en) * 1959-03-02 1962-02-27 Raytheon Co Methods of heating and levitating molten material

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3271118A (en) * 1961-10-18 1966-09-06 Monsanto Co Seed crystals and methods using the same
US3449087A (en) * 1966-06-27 1969-06-10 Commerce Usa Purification by selective crystallization and remelt
US3622280A (en) * 1967-04-29 1971-11-23 Siemens Ag Adjustable heating device for crucible-free zone melting a crystalline rod
US3773499A (en) * 1968-04-03 1973-11-20 M Melnikov Method of zonal melting of materials
US4126509A (en) * 1975-11-14 1978-11-21 Siemens Aktiengesellschaft Process for producing phosophorous-doped silicon monocrystals having a select peripheral dopant concentration along a radial cross-section of such monocrystal

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GB910078A (en) 1962-11-07
NL104013C (en))
DE1220389B (de) 1966-07-07
NL253184A (en))

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