WO2019184128A1 - 用于磁控直拉单晶的磁体线圈及磁控直拉单晶的方法 - Google Patents

用于磁控直拉单晶的磁体线圈及磁控直拉单晶的方法 Download PDF

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WO2019184128A1
WO2019184128A1 PCT/CN2018/094314 CN2018094314W WO2019184128A1 WO 2019184128 A1 WO2019184128 A1 WO 2019184128A1 CN 2018094314 W CN2018094314 W CN 2018094314W WO 2019184128 A1 WO2019184128 A1 WO 2019184128A1
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coil
single crystal
coils
sub
magnetic field
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PCT/CN2018/094314
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English (en)
French (fr)
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汤洪明
傅林坚
刘黎明
刘赛波
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苏州八匹马超导科技有限公司
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Priority to US16/617,073 priority Critical patent/US11578423B2/en
Publication of WO2019184128A1 publication Critical patent/WO2019184128A1/zh

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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
    • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
    • C30B15/20—Controlling or regulating
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F6/00—Superconducting magnets; Superconducting coils
    • H01F6/06—Coils, e.g. winding, insulating, terminating or casing arrangements therefor
    • 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
    • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
    • 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
    • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
    • C30B15/30—Mechanisms for rotating or moving either the melt or the crystal
    • C30B15/305—Stirring of the melt
    • 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
    • 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
    • C30B30/00—Production of single crystals or homogeneous polycrystalline material with defined structure characterised by the action of electric or magnetic fields, wave energy or other specific physical conditions
    • C30B30/04—Production of single crystals or homogeneous polycrystalline material with defined structure characterised by the action of electric or magnetic fields, wave energy or other specific physical conditions using magnetic fields
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
    • H01F27/38—Auxiliary core members; Auxiliary coils or windings

Definitions

  • the present disclosure relates to the field of semiconductor technology, for example, to a magnet coil for magnetically controlled Czochralski single crystal and a method of magnetron Czochralski single crystal.
  • the method of producing single crystal silicon includes a Czochralski method and a suspension zone melting method.
  • single crystal silicon is usually prepared by a Czochralski method, and a rod-shaped single crystal silicon is grown from a melt by a Czochralski method using a single crystal furnace.
  • the thermal convection of the melt causes macroscopic inhomogeneities and microscopic inhomogeneities of the impurities, thereby affecting the physical and chemical properties of the crystal. Therefore, suppressing the thermal convection of the melt is one of the important ways to improve the quality of single crystal silicon.
  • the magnetron-controlled single crystal technology has been gradually developed.
  • the Czochralski method by applying a strong magnetic field on the outside of the single crystal furnace, the thermal convection of the melt is suppressed, the impurity content of the crystal is lowered, and the uniformity of longitudinal and radial impurity distribution is improved to obtain a high quality single crystal. silicon.
  • the magnetic field generating device of the conventional magnetron-controlled direct drawing method generally uses a permanent magnet material and a conventional electromagnet, and the magnetron straight-drawing method is limited by the saturation magnetization of the permanent magnet material and the power of the conventional electromagnet, so that the magnetic field strength is generated. Often not high, the effect of heat convection suppression on the melt is more common. With the development of superconducting magnet technology, more and more superconducting magnets have replaced conventional electromagnets. The superconducting magnet can generate a stronger magnetic field, and the heat convection suppression effect of the melt is more obvious. With the corresponding crystal pulling process, a larger size or higher quality single crystal silicon can be prepared.
  • the magnetic field generated by the superconducting magnet in the magnetron Czochralski method is generally divided into a hook magnetic field, a transverse magnetic field, and a longitudinal magnetic field.
  • a hook magnetic field a transverse magnetic field
  • a longitudinal magnetic field a longitudinal magnetic field.
  • the direction of the magnetic field lines of the longitudinal magnetic field and the transverse magnetic field are both single directions, they only suppress the partial thermal convection perpendicular to the magnetic lines, but do not inhibit the thermal convection parallel to the magnetic lines, affecting the impurity content of the single crystal silicon. With uniformity.
  • a hook-shaped magnetic field which contains a divergent magnetic field of radial and longitudinal components, which can effectively suppress forced convection caused by thermal convection, single crystal and relative rotation of the crucible, thereby
  • the quality of crystalline silicon is further improved.
  • the requirement for the strength of the magnetic field increases, so that the weight and cost of the conventional magnet that generates the hook magnetic field increase.
  • the present application proposes a magnet coil for magnetically controlled Czochralski single crystal and a method of magnetically controlled Czochralski single crystal, which can meet the magnetic field strength requirement for manufacturing single crystal silicon, and can reduce the magnet of the conventional magnetic field generating the hook magnetic field. Weight and cost.
  • the present application provides a magnet coil for a magnetron Czochralski single crystal, comprising a first coil and a second coil disposed coaxially opposite to each other, and an auxiliary coil is disposed between the first coil and the second coil.
  • the distance from the first edge of the auxiliary coil adjacent to the first coil to the first coil is equal to the distance between the second edge of the auxiliary coil adjacent to the second coil and the second coil, the auxiliary coil a central axis, a central axis of the first coil, and a central axis of the second coil are coincident;
  • the direction of current in the first coil and the direction of current in the second coil are opposite to form a hook-shaped magnetic field, and a magnetic field generated by the current in the auxiliary coil is used to enhance the hook-shaped magnetic field.
  • the auxiliary coil includes a plurality of sub-coils; the plurality of sub-coils are sequentially connected in series and enclose a circle along a central axis of the auxiliary coil, and the sizes of the loops of the plurality of sub-coils are respectively different from the The size of one coil is the same as the size of the second coil.
  • the number of the plurality of sub-coils is an even number.
  • a preset distance is provided between adjacent ones of the plurality of sub-coils.
  • each of the sub-coils is a circular coil, and an end surface of each of the sub-coils is perpendicular to an end surface of the first coil and an end surface of the second coil, respectively.
  • the centers of the plurality of sub-coils are all located on a same circumference, and a center of the circumference is located on a central axis of the first coil and the second coil.
  • each of the sub-coils is an arc-shaped coil
  • the arc-shaped coil includes two vertical sides disposed in parallel and two arc-shaped sides disposed in parallel, and two ends of each vertical side are respectively connected The ipsilateral ends of the two curved sides.
  • a center of a circle surrounded by the curved sides of the plurality of sub-coils is located on a central axis of the first coil and the second coil.
  • the first coil, the second coil, and the auxiliary coil are all made of a superconducting material.
  • the application also provides a magnetically controlled Czochralski single crystal method, comprising:
  • a heater is disposed in the single crystal furnace, and the crucible containing the melt is heated in the heater so that the ingot in the crucible melts into a melt, and the liquid level of the melt is located in the auxiliary coil of the coil Center plane
  • the present application forms a hook magnetic field by coaxially setting a first coil and a second coil coaxially with a reverse current, and simultaneously adding an auxiliary coil between the first coil and the second coil, in a pair of coaxial reverse
  • the magnetic field generated by the auxiliary coil and the magnetic field generated by the pair of reverse coils are superimposed on each other, thereby enhancing the strength of the magnetic field, improving the quality of the single crystal silicon, reducing the weight of the magnet, and saving the manufacturing cost.
  • Embodiment 1 is a schematic structural view of a magnet coil for a magnetron Czochralski single crystal provided in Embodiment 1;
  • Embodiment 2 is a cross-sectional view of a magnet coil and a single crystal furnace for a magnetron Czochralski single crystal provided in Embodiment 1;
  • FIG. 3 is a schematic view showing a ferromagnetic periphery of a magnet coil for a magnetron CZ single crystal provided in Embodiment 1;
  • Embodiment 4 is a schematic structural view of a magnet coil for a magnetron Czochralski single crystal provided in Embodiment 2.
  • the magnetic field lines of the hook-shaped magnetic field are vertically symmetrical. Due to the coil power of the traditional hook-shaped magnetic field or the large repulsive force between the coils, the magnetic field strength is much lower than that of the magnetic field using the transverse magnetic field (20% of the transverse magnetic field ⁇ 50%). However, the transverse magnetic field destroys the symmetry of the original transverse heat convection of the Czochralski growth system, causing severe radial segregation and growth streaks of the rod-shaped single crystal silicon. However, due to the lower magnetic field generated by the magnetic field of the hook-shaped magnetic field, the quality of the prepared single crystal silicon is often close to that of the magnet using the transverse magnetic field. Therefore, increasing the magnetic field of the hook magnet is a method for effectively improving the quality of the single crystal silicon. In general, the magnetic field strength of the hook magnet at the melt level of the crucible sidewall is required to be 2000-4000 Gauss (GS).
  • the present embodiment provides a magnet coil for a magnetron Czochralski single crystal.
  • the coil includes a first coil 1 and a second coil 2 disposed coaxially opposite to each other, and the first coil 1 and the second coil
  • An auxiliary coil 3 is disposed between the coils 2, and the distance between the first edge of the auxiliary coil 3 close to the first coil 1 and the first coil 1 is equal to the distance between the second edge of the auxiliary coil 3 close to the second coil 2 and the second coil 2,
  • the central axis of the auxiliary coil 3, the central axis of the first coil 1 and the central axis of the second coil 2 are coincident; when energized, the direction of the current in the first coil 1 and the direction of the current in the second coil 2 are opposite to form a hook shape
  • the magnetic field, the magnetic field generated by the current in the auxiliary coil 3, is used to enhance the hook magnetic field.
  • the first coil 1 and the second coil 2 are coaxially disposed and a reverse current is applied to form a hook-shaped magnetic field including radial and longitudinal magnetic field components, and at the same time, the first coil 1 and the second coil 2
  • An auxiliary coil 3 is interposed between the magnetic field generated by the auxiliary coil 3 and the magnetic field generated by the pair of reverse coils on the basis of a pair of coaxial reverse coils, thereby enhancing the strength of the magnetic field.
  • the uniformity of the magnetic field can be adjusted, so that the suppression of the thermal convection of the melt in the single crystal furnace 10 is uniform, so that the obtained single crystal silicon is high.
  • the purity makes the impurity distribution in the single crystal silicon more uniform and improves the quality of the single crystal silicon.
  • the first coil 1 may be disposed above the second coil 2.
  • the distance between the first edge of the auxiliary coil 3 adjacent to the first coil 1 and the first coil 1 is equal to the distance between the second edge of the auxiliary coil 3 close to the second coil 2 and the second coil 2 to increase the first coil 1 and the The strength of the magnetic field at the axial zero magnetic plane formed by the two coils 2, thereby improving the quality of the single crystal silicon.
  • the auxiliary coils 3 are equally spaced from the first coil 1 and the second coil 2, respectively.
  • the auxiliary coil 3 includes not less than two sub-coils 31, and the sub-coils 31 are connected in series, and the sub-coils 31 are spaced apart, that is, a predetermined distance is provided between adjacent ones of the plurality of sub-coils 31.
  • the number of the sub-coils 31 is not limited in this embodiment, and may be adjusted according to actual production requirements to adjust the uniformity of the magnetic field, thereby consistently suppressing the thermal convection of the melt in the single crystal furnace 10.
  • the single crystal silicon obtained has high purity, and the impurity distribution in the single crystal silicon is more uniform, thereby improving the quality of the single crystal silicon.
  • the plurality of sub-coils 31 are uniformly arranged annularly along the central axis of the auxiliary coil 3 to further ensure uniformity of the magnetic field.
  • the current in the sub-coil 31 can be the same as the current magnitude and direction of the first coil 1.
  • the current in the sub-coil 31 can also be the same as the current and direction in the second coil 2. This is not limited.
  • each of the sub-coils 31 is a circular coil, and the axis of the sub-coil 31 is perpendicular to the axis of the auxiliary coil 3, that is, the end faces of each of the sub-coils 31 are perpendicular to the end faces of the first coil 1 and the end faces of the second coil 2, respectively, and
  • the centers of the plurality of sub-coils 31 are all located on the same circumference, and the center of the circumference is located on the central axes of the first coil 1 and the second coil 2.
  • the first coil 1, the second coil 2, and the auxiliary coil 3 are all made of a superconducting material.
  • the first coil 1, the second coil 2, and the auxiliary coil 3 are all set as superconducting coils in a low temperature environment. Under the superconducting state, it can carry higher current than the conventional coil and generate a higher magnetic field, thus ensuring the quality of the single crystal silicon.
  • the first coil 1, the second coil 2, and the auxiliary coil 3 are all located outside the single crystal furnace 10.
  • the coil further includes a cryogenic vessel 4, and the cryocontainer 4 is disposed outside the single crystal furnace 10, and the first coil 1, the second coil 2, and the auxiliary coil 3 are both disposed in the cryocontainer 4.
  • the cryogenic vessel 4 is filled with a cryogenic liquid, and the coil is placed in the cryogenic liquid.
  • the cryocontainer 4 is provided with a vacuum interlayer, and the cryocontainer 4 is further provided with a vacuum valve (not shown), online After the coil is energized, the vacuum valve can ensure the vacuum environment outside the cryogenic liquid, thereby achieving the effect of heat insulation, so that the low temperature liquid is in a zero consumption state.
  • the cryogenic liquid is liquid helium
  • the vacuum layer is liquid helium dewar.
  • the cooling liquid and the vacuum interlayer in the embodiment may be other types, and the coil is cooled by a cryogenic liquid, or may be directly cooled by a refrigerator, and is not limited in this embodiment.
  • the coil provided in this embodiment may further include an iron screen 5, wherein the iron screen 5 is coated on the outside of the cryocontainer 4 to reduce the influence of the leakage magnetic field on the equipment of the single crystal furnace 10, and meet the magnetic field requirements of the human body. Further increase the magnetic field strength at the melt level to improve the quality of the single crystal silicon.
  • the embodiment further provides a method for magnetron controlled Czochralski single crystal, the method of magnetron Czochralski single crystal comprising the following steps:
  • Step 1 The coil is placed outside the single crystal furnace 10, and the magnet coil is energized.
  • the energizing the coil includes energizing the first coil 1, the second coil 2, and the auxiliary coil 3.
  • the first coil 1 and the second coil 2 have opposite currents in the opposite direction.
  • the current in each of the coils 3 in the coil 3 may be the same as the current of the first coil 1, or may be different from the current of the first coil 1.
  • Step 2 a heater is arranged in the single crystal furnace 10, and the crucible 20 in which the ingot is placed is placed in the heater for heating, so that the ingot in the crucible 20 is melted into a melt, and the liquid level of the melt is located in the auxiliary coil 3 The center plane.
  • the ingot is heated to be in a molten state, and a melt is formed.
  • the hook-shaped magnetic field provided by the first coil 1, the second coil 2 and the auxiliary coil 3 acts on the melt, and the melt has a uniform suppression of the thermal convection of the melt in the single crystal furnace 10 under the action of a uniform magnetic field, so that The obtained single crystal silicon has high purity, and the impurity distribution in the single crystal silicon is more uniform, thereby improving the quality of the single crystal silicon.
  • Step 3 Single crystal silicon is obtained by a Czochralski method.
  • the magnetic field requirement of the superconducting magnet for Czochralski single crystal is that the magnetic field strength at the melt level of the sidewall of the crucible 20 is 2000-5000 GS.
  • the higher the magnetic field strength the higher the effect of suppressing the thermal convection of the melt.
  • the quality of crystalline silicon is better. Under the action of strong magnetic field, forced convection caused by relative convection of heat convection, single crystal and crucible 20 can be effectively suppressed, so that the quality of crystalline silicon is further improved.
  • the Czochralski method means that after heating the melt to a molten state, a chemically etched seed crystal is lowered and the seed crystal is rotated to bring the seed crystal into contact with the melt, and the melt is on the seed crystal. Crystallize continuously until a certain diameter of single crystal silicon is reached.
  • the present embodiment provides a magnet coil for a magnetically controlled Czochralski single crystal, and another form of the sub-coil 31 is provided. As shown in FIG. 4, the sub-coil 31 provided in this embodiment is an arc-shaped coil.
  • each of the curved coils comprises two vertical sides arranged in parallel and two curved sides arranged in parallel, and two ends of each vertical side respectively connect the same side ends of the two curved sides, and a plurality of sub-edges
  • the center of the circle surrounded by the curved sides of the coil 31 is located on the central axes of the first coil 1 and the second coil 2.
  • the number of the sub-coils 31 in the embodiment is two, and the sub-coils 31 of the two curved coils are formed with two open circular coils.
  • the number of the sub-coils 31 may be four or six.
  • the number of the sub-coils 31 is not limited in this embodiment, and may be adjusted according to actual needs.
  • the sub-coil 31 may also be a spiral tube or an ellipse or the like, and the number of the coils may be adjusted according to the requirements of the strength of the magnetic field when the single crystal silicon is fabricated, which is not limited thereto.
  • the uniformity of the magnetic field can be adjusted, thereby suppressing the thermal convection of the melt in the single crystal furnace, and the obtained single crystal silicon has high purity, and The impurity distribution in the single crystal silicon is more uniform; even when the original magnetic field strength is constant, the repulsive force between the coils can be reduced by reducing the amount of the superconducting coil, thereby reducing the weight of the magnet and saving the manufacturing cost.

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Abstract

一种用于磁控直拉单晶的磁体线圈，包括：同轴相对设置的第一线圈（1）和第二线圈（2），第一线圈（1）和第二线圈（2）之间设置有辅助线圈（3），辅助线圈（3）靠近第一线圈（1）的第一边缘与第一线圈（1）的距离等于辅助线圈（3）靠近第二线圈（2）的第二边缘与第二线圈（2）的距离，辅助线圈（3）的中心轴线、第一线圈（1）的中心轴线以及第二线圈（2）的中心轴线重合；通电时，第一线圈（1）中的电流方向和第二线圈（2）中的电流方向相反，以形成勾形磁场，辅助线圈（3）中的电流产生的磁场用于增强勾形磁场。

Description

用于磁控直拉单晶的磁体线圈及磁控直拉单晶的方法 技术领域
本公开涉及半导体技术领域，例如涉及一种用于磁控直拉单晶的磁体线圈及磁控直拉单晶的方法。
背景技术
随着半导体微电子器件和大规模集成电路等器件制造技术的迅速发展，对半导体材料单晶硅的制备要求越来越高。单晶硅中的有害杂质及其不均匀性是制约单晶硅质量提高的主要因素之一，因此减少单晶硅的缺陷和杂质含量，提高氧、碳等杂质以及掺杂剂在晶体中分布的均匀性为制备单晶硅的重要指标。
单晶硅的制法包括直拉法和悬浮区熔法。目前单晶硅通常采用直拉法来制备，直拉法使用单晶炉从熔体中生长出棒状单晶硅。在直拉法生长晶体的过程中，熔体的热对流使杂质产生宏观不均匀性和微观不均匀性，从而影响晶体的物理性质和化学性质。因此，抑制熔体的热对流是提高单晶硅质量重要途径之一。
为了解决上述问题，逐步发展了磁控拉单晶技术。在直拉法的基础上，通过在单晶炉外侧施加强磁场，对熔体的热对流进行抑制，降低晶体的杂质含量，提高纵向和径向杂质分布均匀性，以得到高品质的单晶硅。
传统的磁控直拉法的磁场产生装置一般使用永磁材料及常规电磁铁，该磁控直拉方法由于受限于永磁材料的饱和磁化强度及常规电磁铁的功率，使得产生的磁场强度往往不高，对熔体的热对流抑制效果较为普通。随着超导磁体技 术的发展，越来越多的超导磁体替代了常规电磁铁。超导磁体可以产生更强的磁场，对熔体的热对流抑制效果更为明显，配合相应的拉晶工艺，可以制备出更大尺寸或更高品质的单晶硅。
磁控直拉法中的超导磁体产生的磁场一般分为勾形磁场、横向磁场、纵向磁场。其中，纵向磁场对熔体的热对流的抑制效果不是很明显，已经被勾形磁场和横向磁场所替代。
由于纵向磁场和横向磁场的磁力线方向都是单一方向，它们仅对与磁力线垂直的部分热对流起抑制作用，而对与磁力线平行的热对流起不到抑制作用，影响了单晶硅的杂质含量与均匀性。
为了进一步提高单晶的品质，人们提出一种勾形磁场，该勾形磁场包含径向和纵向分量的发散型磁场，可有效地抑制热对流、单晶体和坩埚相对旋转产生的强迫对流，从而使晶体硅的品质得到进一步改善。随着单晶硅尺寸的增大，对磁场强度的要求增大，使得传统的产生勾形磁场的磁体重量和成本增大。
发明内容
本申请提出一种用于磁控直拉单晶的磁体线圈及磁控直拉单晶的方法，能够达到生产制造单晶硅的磁场强度要求，同时能够降低传统的产生勾形磁场的磁体的重量和成本。
本申请提供一种用于磁控直拉单晶的磁体线圈，包括同轴相对设置的第一线圈和第二线圈，所述第一线圈和所述第二线圈之间设置有辅助线圈，所述辅助线圈靠近所述第一线圈的第一边缘与所述第一线圈的距离等于所述辅助线圈靠近所述第二线圈的第二边缘与所述第二线圈的距离，所述辅助线圈的中心轴线、所述第一线圈的中心轴线以及所述第二线圈的中心轴线重合；
通电时，所述第一线圈中的电流方向和所述第二线圈中的电流方向相反，以形成勾形磁场，所述辅助线圈中的电流产生的磁场用于增强所述勾形磁场。
可选的，所述辅助线圈包括多个子线圈；所述多个子线圈依次串联并且沿所述辅助线圈的中心轴线围成一个圈，所述多个子线圈围成的圈的大小分别与所述第一线圈的大小和所述第二线圈的大小相同。
可选的，所述多个子线圈的数量为偶数。
可选的，所述多个子线圈中的相邻的子线圈之间设有预设距离。
可选的，每个所述子线圈为圆形线圈，每个所述子线圈的端面分别与所述第一线圈的端面和所述第二线圈的端面垂直。
可选的，所述所述多个子线圈的圆心均位于同一圆周上，所述圆周的圆心位于所述第一线圈和所述第二线圈的中心轴线上。
可选的，每个所述子线圈为弧形线圈，所述弧形线圈包括相对平行设置的两条竖边和相对平行设置的两条弧形边，每条竖边的两端分别连接所述两条弧形边的同侧端。
可选的，所述多个子线圈的弧形边围成的圆的圆心位于所述第一线圈和所述第二线圈的中心轴线上。
可选的，所述第一线圈、所述第二线圈以及所述辅助线圈均由超导材料制作而成。
本申请还提供了一种磁控直拉单晶的方法，包括：
将上述的线圈布置于单晶炉外，并对所述线圈通电；
在单晶炉内设置加热器，并将容纳有熔体的坩埚至于加热器内进行加热，使得坩埚内的晶块熔融为熔体，所述熔体的液面位于上述线圈中的辅助线圈的中心平面；
通过直拉法得到单晶硅。
本申请通过将第一线圈和第二线圈同轴设置且通入反向电流，以形成勾形磁场，同时，在第一线圈和第二线圈之间增设辅助线圈，在一对同轴反向线圈的基础上，使辅助线圈产生的磁场与一对反向线圈产生的磁场相互叠加，从而增强了磁场的强度，提高了单晶硅的品质，且减轻磁体的重量，节省制造成本。
附图说明
图1是实施例一提供的用于磁控直拉单晶的磁体线圈的结构示意图；
图2是实施例一提供的用于磁控直拉单晶的磁体线圈与单晶炉的剖视图；
图3是实施例一提供的用于磁控直拉单晶的磁体线圈外设铁磁的示意图；
图4是实施例二提供的用于磁控直拉单晶的磁体线圈的结构示意图。
图中：
10、单晶炉；20、坩埚；
1、第一线圈；2、第二线圈；3、辅助线圈；31、子线圈；
4、低温容器；5、铁屏。
具体实施方式
勾形磁场的磁力线分布为上下对称，由于传统的勾形磁场的线圈功率或线圈之间的巨大斥力，其磁场强度与采用横向磁场的磁场强度相比要低很多(为横向磁场的20％～50％)。但是，横向磁场破坏了直拉生长系统原有横向热对流的对称性，引起了严重的径向分凝，棒状单晶硅出现生长条纹。但由于勾形磁场位型的磁体产生磁场较低，其制备的单晶硅的品质往往与采用横向磁场的磁体相近。因此，提高勾形磁体的磁场，是有效提高单晶硅品质的一种方法。一般 的，要求勾形磁体在坩埚侧壁熔体液面处的磁场强度为2000-4000高斯(GS)。
本实施例提供了一种用于磁控直拉单晶的磁体线圈，如图1所示，该线圈包括同轴相对设置的第一线圈1和第二线圈2，第一线圈1和第二线圈2之间设置有辅助线圈3，辅助线圈3靠近第一线圈1的第一边缘与第一线圈1的距离等于辅助线圈3靠近第二线圈2的第二边缘与第二线圈2的距离，辅助线圈3的中心轴线、第一线圈1的中心轴线以及第二线圈2的中心轴线重合；通电时，第一线圈1中的电流方向和第二线圈2中的电流方向相反，以形成勾形磁场，辅助线圈3中的电流产生的磁场用于增强勾形磁场。
本实施例通过将第一线圈1和第二线圈2同轴设置且通入反向电流，以形成包含径向和纵向磁场分量的勾形磁场，同时，在第一线圈1和第二线圈2之间增设辅助线圈3，在一对同轴反向线圈的基础上，使辅助线圈3产生的磁场与一对反向线圈产生的磁场相互叠加，从而增强了磁场的强度。此外，通过调整辅助线圈3和辅助线圈3的电流，能够调节磁场的均匀度，从而对单晶炉10内的熔体热对流的抑制具有一致性，从而使制得的单晶硅具有很高的纯度，使单晶硅内的杂质分布更加均匀，提高了单晶硅的品质。
在一实施例中，第一线圈1可以设置在第二线圈2的上方。上述辅助线圈3靠近第一线圈1的第一边缘与第一线圈1的距离等于辅助线圈3靠近第二线圈2的第二边缘与第二线圈2的距离，以增加在第一线圈1和第二线圈2形成的轴向零磁面处的磁场强度，从而提高单晶硅的品质。
一实施例中，辅助线圈3分别与第一线圈1和第二线圈2等间隔设置。
辅助线圈3包括不少于两个子线圈31，子线圈31依次串联，且所述子线圈31间隔设置，即：多个子线圈31中相邻的子线圈31之间设有预设距离。在一实施例中，本实施例对子线圈31的数量不作限定，可以根据实际的生产需要进 行调整，以调节磁场的均匀度，从而对单晶炉10内的熔体热对流的抑制具有一致性，使制得的单晶硅具有很高的纯度，单晶硅内的杂质分布更加均匀，提高单晶硅的品质。此外，所述多个子线圈31沿所述辅助线圈3的中心轴线环形均匀设置，以进一步地保证磁场的均匀性。在一实施例中，子线圈31内的电流可以与第一线圈1的电流大小和方向相同，子线圈31内的电流也可以与第二线圈2内的电流大小和方向相同，本实施例对此不作限定。
其中，每个子线圈31为圆形线圈，子线圈31的轴线垂直于辅助线圈3的轴线，即：每个子线圈31的端面分别与第一线圈1的端面和第二线圈2的端面垂直，且多个子线圈31的圆心均位于同一圆周上，该圆周的圆心位于第一线圈1和第二线圈2的中心轴线上。
第一线圈1、第二线圈2及辅助线圈3均由超导材料制作而成，本实施例通过将第一线圈1、第二线圈2及辅助线圈3均设置为超导线圈，在低温环境下能够达到超导状态，能够承载比常规线圈更高的电流，产生更高的磁场，从而保证了单晶硅制造时的品质。
如图2所示，第一线圈1、第二线圈2及辅助线圈3均位于单晶炉10外。
如图2和图3所示，线圈还包括低温容器4，低温容器4设置于单晶炉10外，第一线圈1、第二线圈2及辅助线圈3均设置于低温容器4内。其中，低温容器4内填充有低温液体，线圈置于低温液体内，在一实施例中，低温容器4内设置有真空夹层，低温容器4上还设置真空阀门(图中未示出)，在线圈通电后，通过真空阀门可以保证低温液体外部的真空环境，从而起到隔热的效果，使低温液体处于零消耗状态。其中，低温液体为液氦，真空层为液氦杜瓦。在一实施例中，本实施例中的冷却液和真空夹层还可以为其他类型，线圈由低温液体冷却，也可以采用制冷机直接冷却等形式，本实施例对此均不作限定。
此外，本实施例提供的线圈还可包括铁屏5，其中，铁屏5包覆于低温容器4的外部，减小漏磁场对单晶炉10设备的影响，满足人体安全的磁场要求，同时进一步增加熔体液面处的磁场强度，提升单晶硅的品质。
本实施例还提供了一种磁控直拉单晶的方法，该磁控直拉单晶的方法包括以下步骤：
步骤一：将上述线圈设置于单晶炉10外，并对磁体线圈通电。其中，对线圈通电包括对第一线圈1、第二线圈2以及辅助线圈3进行通电，当对磁铁的线圈进行通电时，第一线圈1和第二线圈2内通有方向相反的电流，辅助线圈3中的每个子线圈31内的电流可与第一线圈1的电流大小相同，也可以与第一线圈1的电流大小不相同。
步骤二：单晶炉10内设置加热器，并将放置有晶块的坩埚20置于加热器内进行加热，使得坩埚20内的晶块熔融为熔体，熔体的液面位于辅助线圈3的中心平面。通过对晶块加热使其成为熔融状态，并形成熔体。第一线圈1、第二线圈2以及辅助线圈3提供的勾形磁场作用于熔体，熔体在均匀磁场的作用下，对单晶炉10内的熔体热对流的抑制具有一致性，使制得的单晶硅具有很高的纯度，单晶硅内的杂质分布更加均匀，从而提高了单晶硅的品质。
步骤三：通过直拉法得到单晶硅。直拉单晶用的超导磁体的磁场要求为在坩埚20侧壁熔体液面处的磁场强度为2000～5000GS，磁场强度越高，对熔体的热对流抑制效果更高，制备的单晶硅品质更好。在强磁场的作用下，可有效地抑制热对流、单晶体和坩埚20相对旋转产生的强迫对流，从而使晶体硅的品质得到进一步改善。
其中，直拉法指的是，将熔体加热至熔融状态后，将一个用化学方法刻蚀的籽晶降下来并旋转籽晶，使籽晶与熔体相接触，熔体在籽晶上不断结晶成长， 直至达到一定直径的单晶硅。
实施例二
本实施例提供了一种用于磁控直拉单晶的磁体线圈，还提供了子线圈31的另外一种形式，如图4所示，本实施例提供的子线圈31为弧形线圈。
其中，每个弧形线圈包括相对平行设置的两条竖边和相对平行设置的两条弧形边，每条竖边的两端分别连接所述两条弧形边的同侧端，多个子线圈31的弧形边围成的圆的的圆心位于第一线圈1和第二线圈2的中心轴线上。
可选的，本实施例中的子线圈31的数量为两个，两个弧形线圈的子线圈31形成有两个开口的圆形线圈。在一实施例中，子线圈31的数量还可以为四个或六个，本实施例对子线圈31的数量不作限定，可根据实际需要进行调整。
在一实施例中，子线圈31还可以为螺线管状或椭圆形等，且线圈的数量可以根据单晶硅制作时对磁场强度的要求进行调整，对此不作限定。
本实施例中的其他结构与实施例一中的其他结构相同，在此不再一一赘述。
本实施例通过设置辅助线圈调节和优化磁场，能够调节磁场的均匀度，从而对单晶炉内的熔体热对流的抑制具有一致性，使制得的单晶硅具有很高的纯度，以及单晶硅内的杂质分布更加均匀；即使在原有磁场强度不变的情况下，可通过降低超导线圈的用量，减小线圈之间的排斥力，进而减轻磁体的重量，节省制造成本。

Claims (10)

  1. 一种用于磁控直拉单晶的磁体线圈，包括：同轴相对设置的第一线圈(1)和第二线圈(2)，所述第一线圈(1)和所述第二线圈(2)之间设置有辅助线圈(3)，所述辅助线圈(3)靠近所述第一线圈(1)的第一边缘与所述第一线圈(1)的距离等于所述辅助线圈(3)靠近所述第二线圈(2)的第二边缘与所述第二线圈(2)的距离，所述辅助线圈(3)的中心轴线、所述第一线圈(1)的中心轴线以及所述第二线圈(2)的中心轴线重合；
    通电时，所述第一线圈(1)中的电流方向和所述第二线圈(2)中的电流方向相反，以形成勾形磁场，所述辅助线圈(3)中的电流产生的磁场用于增强所述勾形磁场。
  2. 根据权利要求1所述的线圈，其中，所述辅助线圈(3)包括多个子线圈(31)；所述多个子线圈(31)依次串联并且沿所述辅助线圈(3)的中心轴线围成一个圈，所述多个子线圈(31)围成的圈的大小分别与所述第一线圈(1)的大小和所述第二线圈(2)的大小相同。
  3. 根据权利要求2所述的线圈，其中，所述多个子线圈(31)的数量为偶数。
  4. 根据权利要求2或3所述的线圈，其中，所述多个子线圈(31)中的相邻的子线圈(31)之间设有预设距离。
  5. 根据权利要求2、3或4所述的线圈，其中，每个所述子线圈(31)为圆形线圈，每个所述子线圈(31)的端面分别与所述第一线圈(1)的端面和所述第二线圈(2)的端面垂直。
  6. 根据权利要求5所述的线圈，其中，所述多个子线圈(31)的圆心均位于同一圆周上，所述圆周的圆心位于所述第一线圈(1)和所述第二线圈(2) 的中心轴线上。
  7. 根据权利要求2、3或4所述的线圈，其中，每个所述子线圈(31)为弧形线圈，所述弧形线圈包括相对平行设置的两条竖边和相对平行设置的两条弧形边，每条竖边的两端分别连接所述两条弧形边的同侧端。
  8. 根据权利要求7所述的线圈，其中，所述多个子线圈(31)的弧形边围成的圆的圆心位于所述第一线圈(1)和所述第二线圈(2)的中心轴线上。
  9. 根据权利要求1-8任一项所述的线圈，其中，所述第一线圈(1)、所述第二线圈(2)以及所述辅助线圈(3)均由超导材料制成。
  10. 一种磁控直拉单晶的方法，包括：
    将权利要求1-9任一项所述的线圈设置于单晶炉(10)外，并对所述磁体线圈通电；
    在单晶炉(10)内设置加热器，并将放置有晶块的坩埚(20)置于加热器内进行加热，使得坩埚(20)内的晶块熔融为熔体，所述熔体的液面位于权利要求1-9任一项所述的线圈中的辅助线圈(3)的中心平面；
    通过直拉法得到单晶硅。
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