JP2009051679A - Device and method for growing single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and method for growing a single crystal which facilitate the growth of a large-sized single crystal. <P>SOLUTION: The single crystal growing device for growing the single crystal by forming a melting zone 31 in a contact part by heating the contact part wherein a hollow single crystal precursor 21 and a seed crystal 22 are brought into contact includes: a seed crystal holding part 19 which can hold the seed crystal 22; precursor holding parts 11 and 18 which can hold the single crystal precursor having a hollow part to be an energy transmitting route to be contacted with the seed crystal 22; a first heating part which is composed of a halogen lamp 17 and an elliptic mirror 16 and heats the melting zone by irradiating it with the first heating energy; and a second heating part for heating the melting zone 31 by irradiating it with the second heating energy (laser beams) different from the first heating energy from a laser beam source 41 through optical fibers 42 and through the energy transmitting route in the single crystal precursor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a single crystal growth apparatus and a single crystal growth method for growing a single crystal by heating a contact portion between a single crystal raw material and a seed crystal to form a melting zone in the contact portion.

  In addition to the pulling method represented by the Czochralski method, there are a floating zone (FZ: Floating Zone) melting method using light heating, a Bridgman method, a flux method, and the like as a bulk single crystal growth method.

  In the pulling method, growing a 12-inch Si ingot is industrially put into practical use. However, in the case of an oxide crystal that melts at a high temperature, usable crucible materials are limited by the oxidation resistance of the crucible. Also, contamination by impurities from the crucible can cause problems.

  The floating zone melting method includes a heating method that uses a high frequency and an electron beam, and a condensing heating method that is widely used for growing oxide crystals and the like. This method uses a halogen lamp or a xenon lamp as a light source and a heat source, condenses the light of the lamp at the focal position by a spheroidal reflector (one, two, or four), and the raw material installed at the focal position Is melted at a high temperature.

  The floating zone melting method does not require a crucible material, has an advantage that unintended impurities are hardly mixed, impurities can be added uniformly, and the atmosphere can be easily controlled.

  As a related art related to the present invention, in the floating zone melting method, the tip portion of the melted raw material rod is held by the surface tension and must be controlled so as not to sag. For this purpose, there is a method of reducing the length of the melting zone by reducing the length of the melting zone by providing a light shielding plate (see, for example, Patent Literature 1, Patent Literature 2, and Patent Literature 3). Further, there is a method of making the temperature distribution uniform by moving the reflecting mirror (see, for example, Patent Document 4). Moreover, there exists a system which makes temperature distribution uniform by using a flat filament (for example, refer patent document 5 and patent document 6).

Further, in the floating zone melting method, there is a method using a laser as a light source instead of a halogen lamp (see, for example, Patent Document 7). Moreover, there exists a system which irradiates a molten zone with a laser as assistance of infrared heating (for example, refer patent document 8). In addition, there is a method for producing a group III oxide single crystal for obtaining a single crystal having a high purity and a large diameter (see, for example, Patent Document 9).
Japanese Patent No. 2982642 JP-A-8-11716 Japanese Patent No. 2550344 JP-A-8-208368 Japanese Patent Laid-Open No. 5-17885 JP-A-9-235171 JP 2001-261478 A JP 7-315979 A JP 2006-273684 A

However, it has been difficult to grow a large single crystal by a conventional light heating type floating zone melting method. Therefore, the use of the conventional floating zone melting method has been limited to research use, such as growing a single crystal having a diameter of several millimeters and using it for measuring physical properties. Commercially, TiO ₂ single crystal (rutile) having a diameter of 1 inch was the largest.

  In addition, since the heating method described above introduces light from the horizontal direction and condenses and heats, the light traveling toward the center is absorbed while passing through the melting zone and does not reach the center. Therefore, the central portion of the raw material bar is hardly melted, and the central portion of the crystal is solidified before the outer peripheral portion. Such an unmelted portion of the raw material rod and a solidified portion at the center of the crystal are called a core.

  FIG. 4 is a cross-sectional view showing an example of a core in a conventional single crystal growth apparatus. This figure shows a raw material rod 121, a melting zone 131, and a single crystal 132 in a conventional single crystal growth apparatus. This figure also shows a cross section including the rotation axis of the raw material rod 121 and the single crystal 132. In the melting zone 131, a broken-line triangle (conical cross section) in contact with the bottom of the raw material rod 121 indicates the core on the raw material rod 121 side. Similarly, a broken-line triangle (conical cross section) in contact with the single crystal 132 in the melting zone 131 indicates a core on the single crystal 132 side. When the upper and lower cores come into contact with each other, the raw material rod 121 and the melting zone 131 become unstable. Therefore, it is necessary to prevent the upper and lower cores from contacting each other.

  If the output of the heating source is increased in order to prevent contact between the upper and lower wicks and melt the wick, the surface portion of the melting zone is further heated even when the melting point is exceeded, and a substance with a high vapor pressure (such as gallium oxide) ) Evaporation becomes intense. As a result, the quartz tube becomes cloudy and cannot be condensed and heated.

  Moreover, when the outer peripheral part of a fusion zone becomes higher than melting | fusing point, the fall of surface tension will be caused. If the output of the heating source increases in this state, the raw material in the molten state increases, the molten zone becomes larger, and it cannot be supported by the surface tension.

  As described above, when trying to grow a large single crystal by the floating zone melting method, the melting zone was unstable.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a single crystal growth apparatus and a single crystal growth method that facilitate the growth of a large single crystal.

  In order to solve the above-described problems, one embodiment of the present invention is a single crystal growth apparatus for growing a single crystal by heating a contact portion between a single crystal raw material and a seed crystal to form a melting zone at the contact portion. A seed crystal holding part capable of holding the seed crystal, a raw material holding part capable of holding a single crystal raw material having an energy transmission path in contact with the seed crystal, and A first heating unit that heats the melting zone by irradiating one heating energy; and a second heating energy different from the first heating energy to the melting zone through an energy transmission path in the single crystal raw material. And a second heating unit that heats the melting zone.

  Another embodiment of the present invention is a single crystal growing method for growing a single crystal by heating a contact portion between a single crystal raw material and a seed crystal to form a melting zone at the contact portion, And holding the single crystal raw material having an energy transmission path so as to be in contact with the seed crystal, irradiating the melting zone with a first heating energy, and heating the melting zone. The melting zone is heated by irradiating the melting zone with a second heating energy different from the first heating energy through an energy transmission path in the crystal raw material.

  According to the present invention, it is easy to grow a large single crystal.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the present embodiment, a single crystal growth apparatus for growing a single crystal using a floating zone melting method will be described.

  First, the configuration of the single crystal growth apparatus according to the present embodiment will be described.

  FIG. 1 is a cross-sectional view showing an example of the configuration of the single crystal growth apparatus according to the present embodiment. This single crystal growing apparatus includes an upper shaft 11, a lower shaft 12, a quartz tube 13, an atmospheric gas inlet 14, an atmospheric gas outlet 15, an elliptical mirror 16, a halogen lamp 17, a refractory metal wire 18, and a seed crystal holder. 19, a laser light source 41, an optical fiber 42, a window member 43, an upper shaft drive unit 45, a lower shaft drive unit 46, and a control unit 47. Moreover, this figure shows a cross section including the rotation axes of the upper shaft 11 and the lower shaft 12.

  Further, at the time of single crystal growth, the raw material rod 21 and the seed crystal 22 are installed in the single crystal growth apparatus, and a molten zone 31 and a single crystal 32 are formed between the raw material rod 21 and the seed crystal 22.

The raw material rod 21 according to the present embodiment is hollow. Here, an example of manufacturing a raw material rod for growing a β-Ga ₂ O ₃ single crystal will be described and described with respect to a method for manufacturing the raw material rod 21.

First, a Tamman tube (inner diameter X, length Y) made of dense alumina ceramics (such as SSA-S) is filled with raw material β-Ga ₂ O ₃ powder while extruding air, and Z smaller than X Insert a protective tube with the outside diameter into the center of the Tamman tube. Here, for example, X is 17 mm, Y is 100 mm, and Z is 6 mm. Next, by pulling out the protective tube from the Tamman tube, the tubular raw material remains in the Tamman tube. Next, the raw material rod 21 is manufactured by sintering the raw material in an electric furnace.

  The raw material bar 21 may have a shape in which the upper end is open and the lower end is closed. For example, the lower end of the above-described tubular raw material rod 21 may be melted and closed by a floating zone melting method. Further, instead of a Tamman tube or a protective tube, a dedicated die may be manufactured and a die taken by pressing may be used as the raw material rod 21. Alternatively, a plurality of raw material rods bundled and having a space at the center of the bundle may be used as the raw material rod 21.

  The seed crystal 22 is preferably attached to the seed crystal holder 19 so as to grow in the <100>, <010>, or <001> direction. In particular, the (100) plane is a cleavage plane, and when crystal growth is performed in the <010> and <001> directions, a flat (100) plane appears on the crystal surface, and the crystal cross section becomes flat. When the crystal is grown in the <100> direction, the aspect ratio becomes the smallest compared to other orientations, so the <100> direction is most preferable for heating the molten zone uniformly to obtain a large single crystal.

  The control unit 47 controls the upper shaft drive unit 45, the lower shaft drive unit 46, the laser light source 41, and the halogen lamp 17. The control unit 47 may control each unit according to an operation by the user, or may control each unit according to a preset schedule. The upper shaft drive unit 45 rotates the upper shaft 11 or moves the upper shaft 11 up and down in accordance with an instruction from the control unit 47. Similarly, the lower shaft drive unit 46 rotates the lower shaft 12 or moves the lower shaft 12 up and down in accordance with an instruction from the control unit 47.

  A refractory metal wire 18 for suspending the raw material rod 21 is provided at the lower end of the upper shaft 11. The refractory metal wire 18 is made of, for example, Pt. A seed crystal holder 19 for holding the seed crystal 22 is provided at the upper end of the lower shaft 12. The upper shaft 11, the material rod 21, the seed crystal 22, and the lower shaft 12 can rotate around a common axis.

  An optical fiber 42 is provided on the axis of the upper shaft 11. A window member 43 is provided at the lower end of the optical fiber 42. The window member 43 is made of quartz glass, sapphire glass, or the like, and transmits the laser light from the optical fiber 42 and separates the upper shaft 11 from the quartz rod 13. Accordingly, the laser light generated by the laser light source 41 is guided into the raw material rod 21 through the optical fiber 42 and the window member 43 on the axis of the upper shaft 11. Further, the laser beam passes through the space on the axis of the raw material bar 21 as shown by the broken arrow in the raw material bar 21 in FIG. 1 and is guided to the melting zone 31 without being shielded. A laser light source 41 is provided in the upper shaft 11 and laser light may be irradiated downward without using the optical fiber 42, or laser light may be introduced into the raw material rod 21 using a mirror instead of the optical fiber 42. It may be introduced and irradiated to the melting zone 31. Further, it is more preferable that a lens is combined with the window member 43 so that the lens expands the luminous flux of the laser light in the melting zone 31 to the same extent as the diameter of the hollow portion of the raw material rod 21.

  In the present embodiment, two sets of halogen lamps 17 and elliptical mirrors 16 are provided. The elliptical mirror 16 is a reflecting mirror having a spheroid. One focal point of the elliptical mirror 16 is the position of the halogen lamp 17, and the other focal point is the position of the melting zone 31. The halogen lamp 17 is installed at one focal point of the elliptical mirror 16. As indicated by the broken arrow from the halogen lamp 17 in FIG. 1, the halogen lamp light generated by the halogen lamp 17 is reflected by the elliptical mirror 16 and collected in the melting zone 31. The position of the halogen lamp 17 may be adjusted based on the shape of the melting zone 31.

  The atmospheric gas flows into the quartz tube 13 from the atmospheric gas inlet 14 and flows out of the quartz tube 13 from the atmospheric gas outlet 15. The atmospheric gas is, for example, pressurized dry air.

  During single crystal growth, the raw material rod 21 is suspended from the upper shaft 11 by the refractory metal wire 18. The seed crystal 22 is fixed to the lower shaft 12 by a seed crystal holder 19.

  Next, the operation of the single crystal growth apparatus according to the present embodiment will be described.

  FIG. 2 is a flowchart showing an example of the operation of the single crystal growth apparatus according to the present embodiment. First, the control unit 47 moves the upper shaft 11 and the lower shaft 12 upward or downward, and moves the lower end of the raw material rod 21 and the upper end of the seed crystal 22 to the vicinity of the focal point of the elliptical mirror 16 (S11). Next, the controller 47 rotates the upper shaft 11 and the lower shaft 12 in opposite directions, condenses and heats the halogen lamp 17 light, and gradually increases the output of the halogen lamp 17 (S12). By this processing, the temperature near the focal point of the elliptical mirror 16 is raised.

  Next, after the raw material rod 21 and the seed crystal 22 are melted, the control unit 47 moves the upper shaft 11 and the lower shaft 12 upward or downward to bring the raw material rod 21 and the seed crystal 22 into contact (S13). ). Next, after the melting zone 31 is stabilized, the control unit 47 lowers the upper shaft 11 and the lower shaft 12 (S14). By this treatment, crystal growth is started.

  Next, the control unit 47 performs necking as necessary (S15). Necking is a process in which the crystal orientation is aligned by narrowing the crystal once, and the quality of the crystal grown thereafter is improved. Next, while appropriately increasing the output of the halogen lamp 17, the descending speed of the upper shaft 11 is appropriately controlled to gradually increase the diameter of the single crystal 32 (S16).

  Next, the controller 47 increases the output of the laser light source 41 to melt the laser light before the melting zone 31 sags and before the solidified portion at the center of the single crystal 32 contacts the raw material rod 21. The light is incident on the band 31 (S21). By this treatment, the single crystal can be enlarged.

  FIG. 3 is a cross-sectional view showing an example of a core in the single crystal growing apparatus according to the present embodiment. This figure shows the part of the raw material rod 21, the melting zone 31, and the single crystal 32 in FIG. Further, two broken triangles in contact with the bottom of the raw material rod 21 in the melting zone 31 indicate the core on the raw material rod 21 side. Similarly, a broken-line triangle in contact with the single crystal 32 in the melting zone 31 indicates a core on the single crystal 32 side.

  As in the prior art, when the melting zone 31 is heated only with the halogen lamp light from the side surface, it is difficult to heat the central axis (rotation axis) near the distance from the surface, but according to the present embodiment, By the process S21, since the vicinity of the central axis is heated at the lower part of the raw material bar 31, the core is easily melted. Therefore, the height of the core on the raw material rod 21 side is lower than the core on the raw material rod 121 side in FIG.

  Next, when the remaining amount of raw material bars 21 is reduced, the control unit 47 decreases the lowering speed of the upper shaft 11 (S22). By this process, the volume of the melting zone 31 is reduced and the diameter of the upper part of the single crystal 32 is reduced. Next, the controller 47 decreases the outputs of the laser light source 41 and the halogen lamp 17 (S23). Next, the control unit 47 separates the raw material rod 21 and the single crystal 32 (S24), and this flow ends.

  Conventionally, when the height of the melting zone is increased in order to prevent the contact of the core, the melting zone cannot be supported by the surface tension and the melting zone has dripped, but according to the present embodiment, the lower end of the raw material rod is irradiated with laser light. By heating the core, the core on the raw material rod side can be made smaller, and thereby the height of the melting zone can be reduced. In addition, since the amount of the melt zone is suppressed, the melt zone is less likely to sag even when the single crystal is enlarged.

  Conventionally, the halogen lamp output is increased to prevent the contact of the core, and as a result, the surface of the melting zone is overheated and the evaporation becomes intense and the quartz tube becomes cloudy. By reducing the core by heating with laser light, it is possible to suppress halogen lamp light and prevent overheating of the melt zone surface. Further, since the fogging of the quartz tube is suppressed, the energy input efficiency of the halogen lamp light can be improved. Further, according to the present embodiment, since the raw material rod is hollow, the area of the raw material rod in contact with the melting zone is reduced, and heat loss due to heat conduction from the melting zone to the raw material rod is suppressed.

  Further, conventionally, when the raw material is vaporized and decomposed, bubbles are generated in the melting zone, and when the gradually increasing bubbles are blown, the melting zone 31 is made unstable, making crystal growth difficult. According to the present embodiment, destabilization of the melting zone 31 can be suppressed by the gas generated in the melting zone 31 passing through the space in the raw material rod.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is shown by the scope of claims, and is not restricted by the text of the specification. Further, all modifications, various improvements, alternatives and modifications belonging to the equivalent scope of the claims are all within the scope of the present invention.

  The single crystal raw material corresponds to the raw material rod in the embodiment. Moreover, the raw material holding | maintenance part respond | corresponds to the upper shaft shaft and refractory metal wire in embodiment. The energy transmission path in the raw material holding unit corresponds to the optical fiber and window material in the embodiment. The seed crystal holding unit corresponds to the lower shaft and the seed crystal holder in the embodiment. The first heating unit corresponds to the halogen lamp and the elliptical mirror in the embodiment. The second heating unit corresponds to the laser light source in the embodiment. The first heating energy corresponds to the halogen lamp light in the embodiment. The second heating energy corresponds to the laser light in the embodiment.

It is sectional drawing which shows an example of a structure of the single crystal growth apparatus which concerns on this Embodiment. It is a flowchart which shows an example of operation | movement of the single crystal growth apparatus which concerns on this Embodiment. It is sectional drawing which shows an example of the core in the single crystal growth apparatus which concerns on this Embodiment. It is sectional drawing which shows an example of the core in the conventional single crystal growth apparatus.

Explanation of symbols

11 Upper shaft, 12 Lower shaft, 13 Quartz tube, 14 Atmospheric gas inlet, 15 Atmospheric gas outlet, 16 Elliptical mirror, 17 Halogen lamp, 18 High melting point metal wire, 19 Seed crystal holder, 21 Raw material rod, 22 Seed crystal, 31 melting zone, 32 single crystal, 41 laser light source, 42 optical fiber, 43 window material, 45 upper shaft drive unit, 46 lower shaft drive unit, 47 control unit.

Claims (20)

A single crystal growing apparatus for heating a contact portion between a single crystal raw material and a seed crystal to form a melting zone at the contact portion and growing the single crystal,
A seed crystal holding part capable of holding the seed crystal;
A raw material holding part capable of holding a single crystal raw material having an energy transmission path in contact with the seed crystal;
A first heating unit for heating the melting zone by irradiating the melting zone with a first heating energy;
A second heating unit that heats the melting zone by irradiating the melting zone with a second heating energy different from the first heating energy through an energy transmission path in the single crystal raw material;
A single crystal growing apparatus. In the single crystal growth apparatus according to claim 1,
The single crystal raw material is hollow,
The energy transmission path in the said single crystal raw material is a single crystal growth apparatus which is a hollow part in the said single crystal raw material. In the single crystal growth apparatus according to claim 2,
The single crystal growing apparatus is a single crystal growth apparatus in which the single crystal raw material is a tube having both ends open. In the single crystal growth apparatus according to claim 2,
The single crystal raw material is a tube having one end closed and the other end open.
The apparatus for growing a single crystal, wherein the second heating energy enters the single crystal raw material from the opening. In the single crystal growth apparatus according to any one of claims 1 to 4,
The energy transmission path is an optical transmission path,
The single crystal growing apparatus, wherein the second heating energy is laser light. In the single crystal growth apparatus according to any one of claims 1 to 5,
The raw material holding part has an energy transmission path,
The second heating unit is an apparatus for growing a single crystal that irradiates the melting zone with the second heating energy through an energy transmission path in the raw material holding unit and an energy transmission path in the single crystal raw material. In the single crystal growth apparatus according to claim 6,
The energy transmission path in the raw material holding unit is a single crystal growing apparatus that is an optical fiber. In the single crystal growing apparatus according to claim 6 or 7,
The seed crystal holding unit and the raw material holding unit are single crystal growing apparatuses that can rotate around a common rotation axis. In the single crystal growth apparatus according to claim 8,
An energy transmission path in the single crystal raw material is a single crystal growth apparatus provided on the rotating shaft. In the single crystal growth apparatus according to claim 9,
The energy transmission path in the raw material holding unit is a single crystal growing apparatus provided on the rotating shaft. A method of growing a single crystal by heating a contact portion between a single crystal raw material and a seed crystal to form a melting zone in the contact portion, and growing a single crystal,
Holding the seed crystal and holding a single crystal raw material having an energy transmission path in contact with the seed crystal,
The melting zone is heated by irradiating the melting zone with a first heating energy, and the second heating zone is different from the first heating energy to the melting zone through an energy transmission path in the single crystal raw material. A method for growing a single crystal, wherein the melting zone is heated by irradiating energy. The method for growing a single crystal according to claim 11,
The single crystal raw material is hollow,
The energy transmission path in the said single crystal raw material is a single crystal growth method which is a hollow part in the said single crystal raw material. The method for growing a single crystal according to claim 12,
The method for growing a single crystal, wherein the single crystal raw material is a tube having both ends open. The method for growing a single crystal according to claim 12,
The single crystal raw material is a tube having one end closed and the other end open.
The method for growing a single crystal, wherein the second heating energy is incident on the single crystal raw material from the opening. In the method for growing a single crystal according to any one of claims 11 to 14,
The energy transmission path is an optical transmission path,
The method for growing a single crystal, wherein the second heating energy is laser light. In the method for growing a single crystal according to any one of claims 11 to 15,
The raw material holding part for holding the single crystal raw material has an energy transmission path,
A single crystal growing method in which the second heating energy is irradiated to the melting zone through an energy transmission path in the raw material holding part and an energy transmission path in the single crystal raw material. The method for growing a single crystal according to claim 16,
The energy transmission path in the raw material holding part is a single crystal growing method in which an optical fiber is used. In the method for growing a single crystal according to claim 16 or claim 17,
A single crystal growth method in which the seed crystal and the single crystal raw material are rotated about a common rotation axis. The method for growing a single crystal according to claim 18,
An energy transmission path in the single crystal raw material is a single crystal growth method provided on the rotating shaft. The method for growing a single crystal according to claim 19,
The energy transmission path in the raw material holding part is a single crystal growing method provided on the rotating shaft.

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