JP2008081337A - Single crystal growth apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single crystal growth apparatus controlling the temperature distribution of a melt. <P>SOLUTION: The single crystal growth apparatus comprises an electrically conductive crucible 16 to be filled with a raw material, an induction heating coil 20 that surrounds the side surface of the crucible 16 and heats the raw material in the crucible 16 to form a melt, a holder 28 that pulls up a single crystal from the melt, a support mount 24 that supports the crucible 16, an induction heating coil 30 that heats the holder 28, and an induction heating coil 32 that heats the support mount 24. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a single crystal growing apparatus for growing a single crystal used in an electronic device or the like.

  A single crystal used in an electronic device or the like is obtained by heating a crucible containing a single crystal raw material to melt the raw material, bringing the seed crystal into contact with the melt and pulling up the seed crystal. Can be produced by the so-called CZ method (Czochralski method). In order to obtain a high-quality single crystal having no defects by the CZ method, it is important to obtain a static liquid surface by managing the temperature distribution of the melt. Here, induction heating, resistance heating, and radiation heating are generally used for heating the crucible.

  Induction heating is excellent in energy efficiency since the crucible itself to be heated generates heat. On the other hand, in other heating methods, convection due to temperature distribution occurs in the melt due to the apparatus configuration. It becomes difficult to obtain a static liquid level by convection of the melt. In addition to this, heating by radiation has low energy efficiency, and resistance heating has an essential drawback that it cannot be heated above the melting point of the heating part.

  However, even with induction heating, the magnetic line density and its rate of change cannot be made uniform, and it is difficult to manage the temperature distribution of the melt. Further, (1) heat near the liquid surface of the melt is taken away by the heat of evaporation of the melt, (2) the heat emissivity from the melt surface or the crucible surface to the surroundings, and the heat transfer coefficient to the atmosphere are different. 3) In the case of an open system, heat is dissipated by gas diffusing to the surroundings, (4) Heat escapes from a support base for supporting and fixing a crucible, etc. (5) Atmosphere from a holder supporting a seed crystal -It is difficult to manage the temperature distribution of the melt because the heat escapes to the support device by radiation or heat transfer.

Cited Document 1 includes a high-frequency induction coil, a crucible heated by high-frequency induction, a heater that can be heated independently for high-frequency induction heating above the crucible, a refractory containing the crucible, and a single crystal pulling means. An apparatus for producing a single crystal is disclosed.
JP-A-6-92781

  The single crystal manufacturing apparatus disclosed in Patent Document 1 is intended to cool a single crystal while keeping it warm by a heater that can be independently heated for high-frequency induction heating in the course of cooling. It is not intended to heat the holder (single crystal pulling means) that pulls up the single crystal from, or the support base that supports the crucible, so it cannot prevent the heat from escaping from the holder or crucible, and the temperature of the melt. It is difficult to manage the distribution.

  An object of this invention is to provide the crystal growth apparatus which can obtain the high quality single crystal without a defect.

  In order to achieve the above object, the crystal growth apparatus of the present invention comprises a conductive crucible filled with a raw material and at least a side surface of the conductive crucible, and the raw material in the conductive crucible is heated and melted to melt. An induction heating coil that can be generated, a holder that pulls up the single crystal from the melt, a support that supports the conductive crucible, a first heating means that heats the support, and a second that heats the holder At least one of the heating means.

  The crystal growth apparatus of the present invention heats and melts the raw material for forming a single crystal in the conductive crucible by heating the conductive crucible by passing an alternating current through a dielectric heating coil surrounding at least the side surface of the conductive crucible. Thus, a melt is produced, and a single crystal is obtained from this melt. The crystal growth apparatus of the present invention using a dielectric heating coil to obtain a raw material melt is superior in heating energy efficiency as compared with the case of using heating by resistance heating / radiation as a heating means.

  Although heat may escape from the holder or support base constituting the crystal growth apparatus by radiation or heat transfer, the crystal growth apparatus of the present invention has a first heating means for heating the support base and a second heating means for heating the holder. Since at least one of the heating means is provided, the heating energy efficiency can be improved as compared with the case where only the conductive crucible is heated. Furthermore, by providing at least one of the first and second heating means, the temperature distribution of the melt can be easily managed.

  Even if there is no problem with the heat resistance of the holder or the support base for the current crystal growth apparatus provided with the conductive crucible, the induction heating coil, the holder and the support base, the structure of the apparatus is not greatly changed. The present invention can be applied only by adding a heating means.

  In the crystal growth apparatus of this invention, you may provide both the 1st heating means which heats a support stand, and the 2nd heating means which heats a holder. Thereby, heating energy efficiency can further be improved.

  In the crystal growing apparatus of the present invention, the first heating means and the second heating means may be induction heating coils.

  When induction heating coils are used as the first heating means and the second heating means, an induction heating coil surrounding at least a side surface of the conductive crucible, and an induction heating coil constituting the first heating means and the second heating means, The alternating currents applied to and may have the same frequency and the same phase. Thereby, since interference and cancellation of an electric field can be prevented, heating energy efficiency can be improved.

  When the induction heating coil is used as the first heating means and the second heating means, the induction heating coil that surrounds at least the side surface of the conductive crucible so that the directions of the generated magnetic fields are the same, the first heating means and the first heating means You may arrange | position the induction heating coil which comprises a 2nd heating means. By making the direction of the generated magnetic field the same, interference and cancellation of the electric field can be prevented, so that the heating energy efficiency can be improved.

  When induction heating coils are used as the first heating means and the second heating means, the induction heating coils constituting the first heating means and the second heating means are arranged at positions where the melt does not affect the magnetic field. May be.

  When an oxide melt is generated using oxide as a raw material, the Lorentz force by the induction heating coil as the first heating means and the second heating means is the Lorentz force by the induction heating coil surrounding at least the side surface of the conductive crucible. Unlike the oxide melt, it may directly affect the center of the oxide melt. In this case, the quality of the single crystal may be seriously affected. This is because it is not affected by the Lorentz force on the oxide melt but is not zero. Therefore, each induction heating coil may be arranged so that the magnetic field generated from the induction heating coil as the first heating means and the second heating means does not affect the melt.

  The crystal growth apparatus of the present invention may further include at least one of a first cooling means for cooling the support base and a second cooling means for cooling the holder. By providing the external cooling means, the temperature distribution of the melt can be easily managed.

  ADVANTAGE OF THE INVENTION According to this invention, the crystal growth apparatus which can obtain the high quality single crystal without a defect is provided.

  The crystal growth apparatus of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an embodiment of the crystal growth apparatus of the present invention. A crystal growth apparatus 10 according to the present embodiment includes an inner cylinder 12 and an outer cylinder 14 made of quartz arranged in a nested manner.

  Inside the inner cylinder 12, a graphite-made conductive crucible 16, a graphite lid 18 which covers the opening of the conductive crucible 16 and absorbs radiant heat from the melt, and a conductive crucible 16 are provided. A non-magnetic radiant heat absorbing plate 22 is disposed so as to cover the periphery and prevent heat from being conducted to the induction heating coil 20 described later. The conductive crucible 16 is rotatably supported by a support base 24 made of a magnetic material.

  On the upper side of the conductive crucible 16, a magnetic holder 28 having a seed crystal 26 at the tip is disposed. The holder 28 can be moved up and down by a holder lifting means (not shown). An induction heating coil 20 is disposed outside the outer cylinder 14 so as to surround the side surface of the conductive crucible 16.

  The induction heating coil 32 that is the first heating means for heating the support 24 and the induction heating coil 30 and the induction heating coil 20 that are the second heating means for heating the holder 28 have the same direction of the generated magnetic field. Thus, it arrange | positions so that there may be no concentric circle and an overlapping part. In addition, in order to make the alternating current applied to the induction heating coil 20, the induction heating coil 30, and the induction heating coil 32 have the same frequency and the same phase, these coils are connected to the same AC power source.

  In addition, the induction heating coil 30 and the induction heating coil 32 are disposed at positions sufficiently away from the conductive crucible 16 so as not to affect the melt generated in the conductive crucible 16 by the magnetic field.

  A space surrounded by the outer wall of the inner cylinder 12 and the inner wall of the outer cylinder 14 is a cooling water flow path, and the heat of the conductive crucible 16 heated by the action of the induction heating coil 20 is transmitted to the induction heating coil 20. Is to prevent.

  An inner side of the inner cylinder 12 is an inert gas flow path so that oxidation of the conductive crucible 16 and the melt can be prevented.

  A single crystal can be obtained using the crystal growth apparatus 10 as follows. First, by applying an AC current from an AC power source (not shown) to the induction heating coil 20, the conductive crucible 16 is heated and the single crystal raw material filled in the conductive crucible 16 is heated and melted, and the melt 34. Is generated.

  The seed crystal 26 is brought into contact with the melt 34 rotated at a predetermined rotational speed by the rotation of the conductive crucible 16, and the single crystal is obtained by gradually pulling it up at a predetermined ascent rate.

  At this time, since the holder 28 and the support 24 that can be a heat escape path from the conductive crucible 16 are heated by the induction heating coil 30 and the induction heating coil 32, respectively, the temperature distribution of the melt can be kept uniform. As a result, a high-quality single crystal can be obtained.

  The material of the conductive crucible 16 that can be used in the present invention is not particularly limited, and a high melting point, high electrical conductivity magnetic material such as Pt, Ta, W, or graphite can be used. It is preferable to use graphite for the reason of temperature characteristics of conductivity and electrical conductivity.

The kind of single crystal applicable to the crystal growth apparatus of the present invention is not particularly limited, and examples thereof include oxide single crystals such as LiNbO ₃ and LiTaO ₃ .

  In the crystal growth apparatus of this embodiment, the conductive crucible 16 is rotatably supported by the support base 24, but the holder 28 may be rotatable.

  In the crystal growth apparatus of this invention, you may further provide the electric energy control means which controls the electric energy applied to the induction heating coil 20, the induction heating coil 30, and the induction heating coil 32 as needed. Accordingly, the heat generation amount of the conductive crucible 16, the support base 24, and the holder 28 can be controlled so that the melt 34 has a desired temperature distribution.

  For the purpose of giving the melt 34 a desired temperature distribution, at least one of a first cooling means for cooling the support base 24 and a second cooling means for cooling the holder 28 may be further provided. As a cooling means in this case, for example, a water cooling device can be used.

It is sectional drawing which shows one Embodiment of the crystal growth apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Crystal growth apparatus 12 Inner cylinder 14 Outer cylinder 16 Conductive crucible 18 Lid 20, 30, 32 Induction heating coil 22 Radiation heat absorption plate 24 Support stand 26 Seed crystal 28 Holder 34 Melt

Claims (7)

A conductive crucible filled with raw materials;
An induction heating coil that surrounds at least a side surface of the conductive crucible, and that can heat and melt a raw material in the conductive crucible to generate a melt;
A holder for pulling up the single crystal from the melt;
A support for supporting the conductive crucible;
At least one of a first heating means for heating the support base and a second heating means for heating the holder;
Crystal growth apparatus equipped with   The crystal growth apparatus according to claim 1, comprising both the first heating unit and the second heating unit.   The crystal growth apparatus according to claim 1 or 2, wherein the first heating means and the second heating means are induction heating coils.   The alternating currents applied to the induction heating coil surrounding at least the side surface of the conductive crucible and the induction heating coil constituting the first heating means and the second heating means have the same frequency and the same phase. The crystal growth apparatus according to claim 3.   An induction heating coil that surrounds at least a side surface of the conductive crucible and an induction heating coil that constitutes the first heating means and the second heating means are arranged so that the directions of the generated magnetic fields are the same. The crystal growth apparatus according to claim 3 or 4.   The crystal growth according to any one of claims 3 to 5, wherein an induction heating coil constituting the first heating means and the second heating means is disposed at a position where the melt does not affect the magnetic field. apparatus.   The crystal growth apparatus according to any one of claims 1 to 6, further comprising at least one of a first cooling means for cooling the support base and a second cooling means for cooling the holder.

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