JP2019199375A - Crystal growth apparatus and manufacturing method of single crystal - Google Patents

Abstract

To provide a crystal growth apparatus capable of correcting a change in heat distribution caused by a crucible deformation accompanied by an increase in a number of growth of a crystal and preventing solidification of a raw material on a bottom of the crucible in a single crystal growth apparatus by Chokralsky method in consideration of above circumstances.SOLUTION: A crystal growth apparatus includes a metal crucible capable of reserving a raw material melt, a crucible table supporting the crucible from a bottom and having an auxiliary heater part arranged at a predetermined position outward of the crucible, an induction coil arranged around the crucible, and an auxiliary heater arranged in the auxiliary heater part when the crucible deforms in an outward direction.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a crystal growth apparatus and a method for producing a single crystal.

  As a method for producing an oxide single crystal, a crucible filled with a raw material to become an oxide single crystal is heated to a high temperature to melt the raw material, and a seed crystal is brought into contact with the liquid surface of the raw material melt in the crucible from above. Thereafter, a crystal growth method by the Czochralski method is widely practiced in which an oxide single crystal having the same orientation as that of the seed crystal is grown by rotating it while rotating.

  FIG. 1 is a diagram showing an example of a general crystal growth apparatus for performing crystal growth by the Czochralski method. In the oxide single crystal growth, as shown in FIG. 1, an induction coil 70 is disposed outside the crucible 10, and an eddy current is generated in the crucible 10 by causing a high-frequency current to flow through the induction coil 70, whereby the crucible 10 generates heat. And it is mainly performed by the method in which the raw material in the crucible 10 melts.

  Further, as the pulling progresses, the upper part of the single crystal is cooled by heat transfer from the seed rod (pickup shaft) 80 or heat radiation from the crystal surface. Since the temperature distribution in the growing single crystal becomes large, a device for keeping the upper part of the crucible 10 warm is devised. For example, a cylindrical after-heater 40 that is a heating element other than the crucible 10 is disposed above the crucible 10 in order to suppress cracking due to thermal stress accompanying a temperature difference in the crystal. In addition, a donut-shaped reflector 30 may be arranged to keep the upper part of the crucible 10 warm.

  In single crystal growth by the Czochralski method, a seed crystal is brought into contact with the raw material melting surface of the crucible 10 and rotated, and the crystal is grown while being gradually pulled up. In order to grow a crystal, it is necessary to dissipate the latent heat generated during crystal growth to the upper part of the crystal while keeping the melt interface temperature at the melting point. Therefore, as the crystal grows, the high-frequency power as a heating source must be reduced within an appropriate range.

  In these heating methods, a high frequency current is passed through the induction coil 70 installed in the furnace, thereby generating a high frequency magnetic field. Current is induced in the metal crucible 10 and the metal cylinder (after heater 40) by the high frequency magnetic field, and Joule heat is generated in the metal by the induced current.

  When the magnetic field distribution changes depending on the position of the induction coil 70 and the conductive material, and the shape of the conductive material, the amount of induced current and the amount of heat generation change accordingly. Since the heat generation distribution is determined by fixing these positions, the intensity of the heat generation distribution can be changed by increasing or decreasing the high frequency power.

  FIG. 2 is a diagram showing the result of calculating the magnetic field around the crucible 10 of the crystal growing apparatus shown in FIG. As shown in the calculation result of the magnetic field in FIG. 2, the magnetic field concentrates on the crucible 10 or the corner of the conductor. Therefore, the induced current at the corner increases, and the heat generation at the corner of the crucible 10 increases. Heat generation at the center of the crucible bottom and the body of the crucible is small.

  These heat generations are transferred by heat conduction or convection to determine the melt temperature distribution in the crucible. During crystal growth, the liquid level of the melt decreases with the growth of the crystal, and the high-frequency output is decreased so that the solid-liquid interface between the melt and the crystal maintains the melting point. Along with this, the temperature is lowered at the center of the crucible bottom, and in some cases, the phenomenon that the raw material melt is solidified from the center of the bottom of the crucible (melt solidification) may occur. In addition, if the crystal growth is continued in this state, the solidified crystal grows upward from the bottom of the crucible, and is fused with the crystal being grown, resulting in a situation where the growth must be stopped. There is also.

  In recent years, attempts have been made to increase the number of times the crucible is used as much as possible in order to reduce the cost of manufacturing the single crystal as described above. However, there has been a problem that as the number of times the crucible is used increases, the deformation of the crucible progresses, the corner portion of the crucible becomes round, and the heat generation at the corner portion decreases, so that solidification of the melt at the center of the crucible bottom tends to occur.

  In Patent Document 1, the crucible deformation progresses as the number of crucible uses increases, and depending on how the crucible is deformed, the problem that the yield decreases or voids are included in the single crystal is pointed out. For example, a crucible structure has been proposed in which the thickness on the bottom surface side of the crucible is made thinner than the thickness in the side surface direction to allow deformation to escape to the bottom surface side.

JP2012-250874A

  However, in the configuration described in Patent Document 1, even if the deformation is released to the bottom side, the heat generation at the corner of the crucible bottom is reduced, and the problem of melt solidification at the center of the crucible bottom is not solved.

  Therefore, in view of the above circumstances, the present invention corrects a change in heat generation distribution due to crucible deformation accompanying an increase in the number of crystal growths in a single crystal growth apparatus using the Czochralski method, and efficiently solidifies the raw material at the bottom of the crucible. It is an object of the present invention to provide a crystal growth apparatus that can prevent the problem.

In order to achieve the above object, a crystal growth apparatus according to one aspect of the present invention includes a metal crucible capable of storing and holding a raw material melt,
A crucible base for supporting the crucible from below and having an auxiliary heater installation portion provided at a predetermined position outside the crucible;
An induction coil provided around the crucible;
And an auxiliary heater installed in the auxiliary heater installation portion when the crucible is deformed outward.

  ADVANTAGE OF THE INVENTION According to this invention, even if the frequency | count of crystal growth increases, the single crystal growth apparatus which can be grown without melt solidification from the crucible bottom center can be provided.

It is the schematic which showed an example of the crystal growth apparatus before the crucible deformation | transformation which concerns on embodiment of this invention. It is the figure which showed the result of having calculated the magnetic field around the crucible of the crystal growth apparatus shown in FIG. It is the figure which showed the result of having calculated the magnetic field strength distribution around the crucible of the crystal growth apparatus shown in FIG. It is the figure which showed an example of the crystal growth apparatus which has the crucible which the deformation | transformation produced. It is the figure which showed the result of having calculated the heat generation density of the crucible shown in FIG. 1 and FIG. It is the figure which showed the temperature distribution of the crucible and melt at the time of seeding. It is the schematic which showed an example of the crystal growth apparatus which concerns on embodiment of this invention after a crucible deformation | transformation.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

A crystal growth apparatus using a chocsky method according to an embodiment of the present invention includes lithium niobate LiNbO ₃ (hereinafter referred to as LN) and lithium tantalate LiTaO ₃ grown in the atmosphere or an inert gas atmosphere containing oxygen. (Hereinafter referred to as LT) and a crystal growth apparatus used for manufacturing oxide single crystals such as yttrium aluminum garnet Y ₃ Al ₅ O ₁₂ (hereinafter referred to as YAG). The Czochralski method is called a seed cut out according to a certain crystal orientation. Usually, the tip of a single crystal of about several millimeters is infiltrated into a melt of the same composition, and is gradually pulled up while rotating, thereby producing a seed crystal. This is a method for producing a single crystal having the same orientation.

  FIG. 1 is a schematic diagram showing an example of a crystal growing apparatus before crucible deformation according to an embodiment of the present invention. In the crystal growth apparatus according to the present embodiment, a crystal growth apparatus having the same configuration as that of a conventional crystal growth apparatus is used before the crucible is deformed. Therefore, the crystal growth apparatus of FIG. 1 is demonstrated as a crystal growth apparatus which concerns on this embodiment before a crucible deformation | transformation.

  As shown in FIG. 1, the crystal growing apparatus according to the present embodiment includes a crucible 10, a crucible base 20, a reflector 30, an after heater 40, heat insulating materials 50 and 60, an induction coil 70, and a lifting A shaft 80, a mounting table 90, and a chamber 100 are provided.

  A seed crystal holding portion 81 is provided at the lower end of the pulling shaft 80 to hold the seed crystal 120. In addition, the raw material melt 130 is stored and held in the crucible 10.

  In the crystal growth apparatus according to the present embodiment, the crucible 10 is placed on the crucible base 20. An after heater 40 is installed above the crucible 10 through a reflector 30. Insulating materials 50 and 60 are provided so as to surround the crucible 10, the reflector 30, and the after heater 40. Furthermore, an induction coil 70 is provided so as to surround the crucible 10, the crucible base 20, the reflector 30, the after heater 40, and the heat insulating materials 50 and 60. A chamber 100 is provided outside the induction coil 70 and covers the entire periphery of the heat insulating material 50 and the induction coil 70.

  A pulling shaft 80 is provided above the crucible 10. The pulling shaft 80 has a seed crystal holding portion 81 at the lower end and is configured to be lifted and lowered by a pulling shaft drive motor (not shown). A mounting table 90 is provided below the heat insulating material 50 and in the chamber 100, and supports the whole other than the chamber 100.

  Although not shown, a control unit for controlling the operation of the entire crystal growth apparatus and a power source for supplying power to the induction coil 70 and the entire crystal growth apparatus are provided outside the chamber 100.

  Next, individual components will be described.

  The crucible 10 is a container for storing and holding a crystal raw material and growing a single crystal. Since the crucible becomes a heating element by high frequency induction heating, a metal with low resistance is used. Since oxide crystals such as LT are grown in an atmosphere containing oxygen, they are made of a noble metal that does not react with oxygen and does not react with oxygen, a simple substance such as Pt (platinum), Rh (rhodium), Ir (iridium), or an alloy thereof. It is preferable to become.

  The crucible base 20 is provided as a support base that supports the crucible 10 from below. The crucible base 20 may be made of various materials as long as it has sufficient heat resistance to withstand the heating of the induction coil 70 and durability to support the crucible 10.

  The crucible base 20 of the crystal growth apparatus according to the present embodiment is provided with an auxiliary heater installation portion after the crucible 10 is deformed, and a crucible base on which the auxiliary heater can be installed is used. You may use the crucible base 20 which does not have such an auxiliary heater installation part.

  Since the reflector 30 and the after-heater 40 are also required to have the same characteristics as the crucible 10, it is preferable that the reflector 30 and the after-heater 40 are made of a noble metal, a simple substance such as Pt, Rh, Ir, or an alloy thereof.

  Sintered refractories such as alumina, zirconia, magnesia, and calcia are used for the heat insulating material 50 and the crucible base 20. On the other hand, the heat insulating material 60 around the crucible is preferably powder of alumina, zirconia, magnesia, calcia or the like that can be deformed during heating and cooling.

  The induction coil 70 is a means for heating the crucible 10, the reflector 30, and the after heater 40, and is disposed so as to surround the crucible 10, the reflector 30, and the after heater 40. The induction coil 70 may have any form as long as the crucible 10, the reflector 30, and the after heater 40 can be induction-heated. For example, the induction coil 70 is configured as a high-frequency induction heating device including a high-frequency heating coil.

  The pulling shaft 80 is a means for holding the seed crystal 120, bringing the seed crystal 120 into contact with the surface of the raw material melt 130 held in the crucible 10, and pulling the single crystal while rotating. The pulling shaft 80 has a seed crystal holding portion 81 for holding the seed crystal 120 at its lower end, and includes a pulling shaft driving motor (not shown). The pulling shaft drive motor is a rotation drive mechanism for performing the pulling operation while rotating the crystal when pulling the crystal.

  The chamber 100 plays a role of keeping heat generated by the crucible 10 and the induction coil 70 of the after-heater 40 inside and preventing discharge to the outside. The chamber 100 is made of a material having high heat resistance. The heat insulating material 50 and the chamber 100 have openings 51 and 101 on the ceiling surface, and are configured so that the lifting shaft 80 can be inserted.

  The mounting table 90 is a support means for supporting the whole including the heat insulating material 50.

  An electromagnetic field analysis was performed when a high-frequency current was passed through the coil of the crystal growth furnace having the configuration shown in FIG. FIG. 2 shows the magnetic field line distribution, and FIG. 3 shows the magnetic field intensity distribution. The magnetic field strength is strongest in the region A shown in FIG. 3, and the magnetic field strength is gradually decreased in the order of region B, region C, region D, region E, and region F. 2 and 3, the magnetic field energy cannot enter the region surrounded by the conductor such as the crucible 10 or the after heater 40 or the region below the bottom of the crucible 10 or the magnetic field lines are sparse. I understand that it is small.

  If there is a conductive material near the high-frequency magnetic field lines, an eddy current is generated in the conductive material. Since the conductive material has electric resistance, Joule heat proportional to the square of the current is generated, and the conductive material self-heats. Since the eddy current increases as the magnetic field strength increases, the magnetic field energy concentrates on the outer periphery of the bottom surface of the crucible 10 and the outer periphery of the reflector 30 as shown in FIG. Since the magnetic field lines cannot penetrate into the conductor, if there is a conductive material that blocks the magnetic field lines, the magnetic field energy around it will be reduced.

  FIG. 4 is a diagram showing an example of a crystal growth apparatus having a crucible 10a in which deformation has occurred. When the production of a single crystal is repeated using the crystal growth apparatus shown in FIG. 1, the crucible 10 is deformed by the heat load of heating and cooling. There are many deformations of the crucible 10 such that the vicinity of the bottom surface of the crucible 10 protrudes outward or spreads out. That is, as shown in FIG. 4, when the crucible 10 is further deformed, the corner of the bottom of the crucible (the angle formed by the bottom and the side) becomes round, and deformation occurs such that the cylindrical portion below the crucible swells.

FIG. 5 is a diagram showing the calculation results of the heat generation density of the crucible shown in FIGS. 1 and 4. 5, the horizontal axis is the distance from the crucible bottom in the height direction (mm), the vertical axis indicates the mean value of the heat density at the height position of the horizontal axis (W / m ^3). As shown in FIG. 5, the crucible 10 without deformation has a high heat generation density at the crucible bottom (0 mm), whereas the crucible 10a with deformation has a high heat generation density at a position higher than the bottom of the crucible. However, the heat generation density near the bottom of the crucible is lower than in the case without crucible deformation. That is, it can be seen from FIG. 5 that when the crucible 10 is deformed, the heat generation density in the vicinity of the bottom is significantly reduced.

  FIG. 6 is a diagram showing the temperature distribution of the crucible and the melt during seeding. 6A shows the temperature distribution of the raw material melt 130 when the crucible 10 is not deformed, and FIG. 6B shows the temperature distribution of the raw material melt 130 when the crucible 10 is deformed. The temperature is highest in the region A, and gradually decreases in the order of the region B, the region C, the region D, the region E, the region F, the region G, and the region H. Calculation was performed so that the seed (seed crystal 120) and melt interface temperature coincided with the melting point of LT. It can be seen that the temperature distribution of FIG. 6A without deformation is in a higher temperature range than the temperature distribution of FIG. 6B with deformation. Thus, it can be seen from FIG. 6 that when the crucible 10 is deformed, the temperature at the bottom end of the crucible is lowered and the temperature of the entire melt is also low.

  The heat generation of the crucible 10 is increased by increasing the high-frequency current. However, in the case of one induction coil 70 as shown in FIG. 1, the heat generation of the after heater 40 and the reflector 30 increases due to the increase in current. The balance with the heat generation of 10 is lost. Therefore, it is not preferable to adjust the reduction in heat generation due to crucible deformation with the coil current.

  On the other hand, by adjusting the length of the induction coil 70, it is possible to relatively reduce the magnetic field strength of the after-heater 40, increase the high-frequency current, and adjust the heat generation reduction due to deformation by the coil current. However, since the reflector 30 is positioned between the crucible 10 and the after-heater 40, if the heat generation of the crucible 10 is increased, the heat generation becomes large, and it is difficult to adjust the length of the induction coil 70 and the coil current to make the heat generation constant.

  Therefore, a conductor was installed as an auxiliary heater outside the crucible bottom and below the crucible bottom, and heating with the auxiliary heater was examined. That is, since the auxiliary heater is also a conductor, it is heated by the induction coil 70.

  FIG. 7 is a schematic diagram showing an example of a crystal growth apparatus according to an embodiment of the present invention after the crucible is deformed. As shown in FIG. 7, in the crystal growing apparatus according to the present embodiment, the crucible base 20a is provided instead of the crucible base 20 of FIG. 1 after the crucible 10a is deformed. The crucible base 20a has a larger area in top view than the crucible 10a and includes the crucible 10a. And it has the auxiliary heater installation part 21a in the part outside the crucible 10a. The auxiliary heater installation portion 21a is preferably provided outside the crucible 10a and below the bottom surface of the crucible 10a. The auxiliary heater installation portion 21a is configured, for example, as an annular horizontal step surface having a lower height than the support surface supporting the crucible 10a of the crucible base 20a at the outer edge of the crucible base 20a. And the auxiliary heater 110 is installed on the auxiliary heater installation part 21a which makes a horizontal surface.

  The material of the auxiliary heater 110 is made of heat-resistant and oxidation-resistant platinum, rhodium, iridium and their alloys. For this reason, considering the cost, it is possible to manufacture an auxiliary heater at a lower cost when the thickness is thinner. Therefore, the thickness of the auxiliary heater 110 is preferably in the range of 0.5 mm to 3 mm, and more preferably in the range of 1 mm to 2 mm.

  Even if the deformation of the crucible 10a is not a large deformation, an influence appears when the angle formed between the bottom surface of the crucible and the side wall of the crucible becomes larger than 90 degrees. When the angle formed between the bottom of the crucible and the side wall of the crucible exceeds 100 degrees, solidification at the bottom of the crucible is accelerated, and the crystal size is affected at 120 degrees or more. Therefore, it is desirable to install the auxiliary heater 110 when the angle formed with the side surface of the bottom surface of the crucible reaches 100 degrees. As this angle increases, the amount of heat generated in the crucible 10a decreases.

  Therefore, the position of the auxiliary heater 110 is set so as to obtain a predetermined heat generation amount according to this angle. In particular, it is preferable to arrange the auxiliary heater 110 so that the vicinity of the corner of the crucible bottom generates heat (the heat generation density increases). For example, if the auxiliary heater 110 is brought closer to the induction coil 70 side in the horizontal direction, the amount of heat generation increases. Moreover, the installation position in the up-down direction of the auxiliary heater 110 can adjust the heat generation position of the crucible (the position where the heat generation density reaches the maximum value). By setting the crucible bottom (the support surface supporting the crucible 10a) below the crucible bottom, it is possible to lower the heat generation position (closer to the corner of the crucible).

  The auxiliary heater 110 has an annular shape. The size of the auxiliary heater 110 is preferably such that the position of the outer diameter of the auxiliary heater 110 is larger than the outer diameter of the crucible 10 by 5 mm or more and 20 mm or less on one side, and more preferably 10 mm or more and 15 mm or less. If the position of the outer diameter of the auxiliary heater 110 is smaller than the outer diameter of the crucible, the magnetic field strength is weak and heat generation is not sufficient. If the position of the outer diameter exceeds 20 mm on one side from the outer diameter of the crucible, the distance to the crucible 10a is too long and the heat transfer efficiency is deteriorated. Further, the temperature of the outer peripheral portion of the auxiliary heater 110 rises and cracks are likely to occur.

  The position of the inner diameter of the auxiliary heater is preferably larger than 0 on one side and larger by 10 mm or less than the outer diameter of the crucible. The annular width of the auxiliary heater 110 is preferably 5 mm or more and 20 mm or less.

  When the auxiliary heater 110 and the crucible 10a come into contact with each other, it becomes a continuous conductor and the magnetic field strength in the vicinity of the crucible is lowered. The thickness of the auxiliary heater 110 is preferably 0.5 mm or more and 3 mm or less, and more preferably 1 mm or more and 2 mm or less. If the thickness of the auxiliary heater 110 exceeds 3 mm, the heat capacity increases and the temperature decreases. However, if the thickness of the auxiliary heater 110 decreases, the temperature becomes high and heating can be performed efficiently. On the other hand, if the thickness of the auxiliary heater 110 is less than 0.5 mm, the strength of the auxiliary heater 110 itself is low, and the auxiliary heater 110 is easily damaged.

  The vertical installation position of the auxiliary heater 110 is preferably 0 to 35 mm below the support surface that supports the crucible 10a. If the installation position exceeds 35 mm below the support surface, the distance to the crucible 10a is too long, resulting in poor heat transfer efficiency. As described above, it is preferable that the installation position of the auxiliary heater 110 in the vertical direction is appropriately arranged so that the vicinity of the corner of the bottom of the crucible generates heat according to the angle at which the crucible 10a is deformed.

  In order to sufficiently heat the auxiliary heater 110, it is preferable to arrange the auxiliary heater 110 at least 30 mm above the lower end of the induction coil.

  Further, the auxiliary heater installation portion 21a of the crucible base 20a is not limited to a configuration having a recessed flat surface, as long as the auxiliary heater 110 can be disposed at an appropriate position.

  In this embodiment, the crucible base 20 that does not have the auxiliary heater installation portion 21a is used before the crucible 10 is deformed, and the auxiliary heater is used by using the crucible base 20a that has the auxiliary heater installation portion 21a after the crucible 10 is deformed. Although the crucible base 20a is used from the beginning, the auxiliary heater 110 is not installed before the crucible 10 is deformed, and the auxiliary heater 110 is installed after the crucible 10a is deformed. It is. However, since the crucible base 20a is larger in volume than the crucible base 20 and leads to an increase in cost, a method of using the crucible base 20a and the auxiliary heater 110 is sufficient only for the crucible 10a after deformation. However, the purpose is not limited to this method of use, and the crucible base 20a may be used before deformation.

[Example]
Next, examples in which the crystal growth apparatus and the method for producing a single crystal according to the present embodiment are implemented will be described. In the following examples, components corresponding to the present embodiment will be described with the same reference numerals for easy understanding.

[Example 1]
A 6-inch LT crystal was grown in the same growth apparatus as in FIG. 7 using the crucible 10a and the auxiliary heater 110 that were used 50 times or more for crystal growth. The deformation angle of the bottom of the crucible was 145 degrees in a circumferential shape. In addition, the deformation angle of the crucible 10 was an average value of four places divided arbitrarily. The auxiliary heater 110 made of iridium was annular, having a thickness of 1.5 mm, a width of 10 mm, an inner diameter position that was 5 mm on one side from the outer diameter of the crucible, and an outer diameter position that was 15 mm larger on one side than the outer shape of the crucible. The vertical installation position of the auxiliary heater 110 was the same as the support surface supporting the crucible 10a.

  During crystal growth, in order to monitor the solidification from the bottom of the crucible, a temperature change was confirmed when a thermocouple was installed near the bottom of the crucible and solidified at the bottom of the crucible to confirm the occurrence of solidification. Further, when solidification was confirmed at the bottom of the crucible, the crystal growth was completed.

  Further, the crystallization rate was calculated from the crystal weight of LT by the following formula (1).

Crystallization rate = crystal weight / raw material weight (1)
When solidification occurred at the bottom of the crucible, the crystal weight at that time was calculated to terminate the growth when the solidification occurred. When solidification did not occur, it was grown to a predetermined crystal length and calculated as the crystal weight.

  In addition, after the completion of the growth, the status of the auxiliary heater 110 was confirmed. As a result, in Example 1, no solidification signal was generated during growth, and a crystal with a solidification rate of 45% could be grown.

[Example 2]
An annular iridium auxiliary heater 110 having a width of 5 mm was installed such that the inner diameter position was 5 mm on one side from the outer diameter of the crucible and the outer position was 10 mm on one side from the outer diameter of the crucible. Other than that, the pulling-up test was conducted in the same manner as in Example 1. In Example 2, no solidification signal was generated during the growth, and crystals with a solidification rate of 44% could be grown.

[Example 3]
A pulling-up test was conducted in the same manner as in Example 1 except that the auxiliary heater 110 was installed 20 mm below the support surface supporting the crucible 10a. In Example 3, no solidification signal was generated during the growth, and crystals with a solidification rate of 45% could be grown.

[Example 4]
A crucible 110a having a crucible bottom and a deformation angle of 125 degrees and having a circumferential shape was used. Other than that, the pulling-up test was conducted in the same manner as in Example 1. In Example 4, no solidification signal was generated during the growth, and crystals with a solidification rate of 46% could be grown.

[Comparative Example 1]
A pulling-up test was performed in the same manner as in Example 1 except that the outer diameter position of the auxiliary heater 110 was increased by 25 mm on one side from the outer diameter of the crucible and the annular width was 10 mm. There was no generation of a solidification signal during growth, and crystals with a solidification rate of 25% were grown. The crystal shape was poor, and cracks occurred in the outer peripheral portion of the auxiliary heater 110.

[Comparative Example 2]
The inner diameter position of the auxiliary heater 110 was made 10 mm smaller than the outer diameter of the crucible, the outer position was the same as the outer diameter of the crucible, and the annular width was 10 mm. Other than that, the pulling-up test was conducted in the same manner as in Example 1. A solidification signal was generated at the bottom of the crucible at a solidification rate of 28% during growth. It is considered that the heat generation at the bottom of the deformed crucible 10a has decreased.

[Comparative Example 3]
A pull-up test was performed in the same manner as in Example 1 except that the auxiliary heater 110 was installed 40 mm below the support surface supporting the crucible 10 a in the vertical position of the auxiliary heater 110. A solidification signal at the bottom of the crucible was generated at a solidification rate of 27% during the growth. It is considered that the heat generation at the bottom of the deformed crucible 10a has decreased.

[Comparative Example 4]
A pulling-up test was performed in the same manner as in Example 1 except that the auxiliary heater 110 was not used. A solidification signal was generated at the bottom of the crucible at a solidification rate of 19% during growth.

  The results of Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 1. As shown in Table 1, in Examples 1 to 4, a high solidification rate of 44 to 46% was obtained, but in Comparative Examples 1 to 4, the solidification rate was as low as 19 to 28%. Further, in Examples 1 to 4, no crack was generated and no solidification signal was generated. However, in Comparative Examples 1 to 4, a crack was generated in Comparative Example 1, and a solidification signal was generated in Comparative Examples 2 to 3. did. Moreover, although evaluation of Examples 1-4 was a pass, evaluation of Comparative Examples 1-4 was disqualified.

Thus, according to the present embodiment, it was shown that a high-quality single crystal with a high solidification rate can be manufactured by installing the auxiliary heater 110 after the crucible 10a is deformed.

  The preferred embodiments and examples of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments and examples, and the above-described embodiments and examples can be performed without departing from the scope of the present invention. Various modifications and substitutions can be made to the embodiments.

10, 10a Crucible 20, 20a Crucible base 21a Auxiliary heater installation part 30 Reflector 40 After heater 50, 60 Heat insulating material 70 Induction coil 80 Pulling shaft 100 Chamber 110 Auxiliary heater 120 Seed crystal 130 Raw material melt

Claims (6)

A metal crucible capable of storing and holding the raw material melt;
A crucible base for supporting the crucible from below and having an auxiliary heater installation portion provided at a predetermined position outside the crucible;
An induction coil provided around the crucible;
A crystal growth apparatus comprising: an auxiliary heater installed in the auxiliary heater installation section when the crucible is deformed outward.   The crystal growth apparatus according to claim 1, wherein the auxiliary heater is provided on the same side as or below the support surface that supports the crucible.   The crystal growth apparatus according to claim 2, wherein the auxiliary heater is horizontally installed outside the outer diameter of the crucible.   The crystal growth apparatus according to claim 3, wherein the auxiliary heater has an annular planar shape. A single crystal growth step in which the seed crystal is brought into contact with the raw material melt stored and held in the crucible heated by the induction coil and pulled up while growing the single crystal;
A single crystal acquisition step of acquiring the single crystal by removing the grown single crystal;
Washing and cooling the crucible, and preparing a single crystal growth preparation for the next single crystal growth;
The single crystal mass production process for continuously producing a single crystal by cyclically repeating the single crystal growth process, the single crystal acquisition process and the single crystal growth preparation process,
An auxiliary heater installation step of installing an auxiliary heater in a predetermined auxiliary heater installation portion provided in a crucible base that supports the crucible when the crucible is deformed in an outward direction by performing the single crystal mass production step;
A single-crystal mass-production continuation step of performing the single-crystal mass-production step in a state where the auxiliary heater is installed on the crucible base. Before the crucible is deformed, a second crucible base that does not have the auxiliary heater installation portion is used.
The method for producing a single crystal according to claim 5, wherein the crucible base is used after the crucible is deformed.