JP6390502B2 - Single crystal cooling method and manufacturing method - Google Patents

Description

  The present invention relates to a single crystal cooling method and manufacturing method, and a single crystal growing apparatus.

  An oxide single crystal such as an aluminum oxide single crystal is widely used as a crystal substrate for epitaxial growth when producing a blue LED or a white LED. These LEDs are expected to spread in the lighting field from the viewpoint of energy saving, and are attracting attention from various fields.

  As a method for producing a large single crystal of good quality as the above oxide single crystal, there are melt solidification methods such as the Czochralski method (Kzochralski-Method) and the Kyropoulos method (Industry), which are industrially used. Yes. In particular, the Czochralski method is most widely used because of its versatility and high technical perfection.

  In order to produce an oxide single crystal by the Czochralski method, first, an oxide raw material is filled in a crucible, and the raw material is melted by heating the crucible by a high frequency induction heating method or a resistance heating method (for example, Patent Document 1). After the raw material is melted, the seed crystal cut in a predetermined crystal orientation is brought into contact with the surface of the raw material melt, and the single crystal is grown by pulling upward at a predetermined speed while rotating the seed crystal at a predetermined rotation speed.

  However, when an oxide single crystal is crystal-grown by a melt solidification method represented by the Czochralski method, a low-angle grain boundary is likely to be generated in the crystal. If grain boundaries are formed on the wafer serving as the crystal substrate for epitaxial growth, the LED characteristics will be adversely affected, making it difficult to obtain the desired crystal substrate for epitaxial growth from the single crystal ingot obtained by the melt solidification method with high yield. It is.

  In order to reduce the grain boundary generated in the crystal, when growing the oxide single crystal by the melt solidification method, the composition of the heat insulating material around the crucible and the positional relationship between the crucible and the heater are adjusted, so that It is known that by increasing the temperature gradient in the vicinity of the liquid interface, generation of grain boundaries is suppressed, and high-quality crystals can be obtained. However, when the temperature gradient near the solid-liquid interface is large, the stress in the grown crystal becomes large, and if the crystal is cooled without removing the internal stress, cracks may occur in the crystal. Even when a crystal free of cracks is obtained, the substrate may be deformed or cracked due to residual stress in the crystal during the process of processing into a substrate for epitaxial growth, which may cause a significant decrease in yield.

  Therefore, as a method of removing the residual stress in the crystal, at the end of the single crystal growth, the crucible containing the raw material melt is lowered while the furnace temperature is lowered, and the straight body portion of the grown oxide single crystal is heated. A method has been proposed in which the oxide single crystal is separated by holding it so as to be lower than the upper end of the (side cylindrical heater) (see, for example, Patent Document 2). In the method described in Patent Document 2, heat treatment is performed by moving a grown crystal to a low temperature gradient region after the growth is completed in a crystal growing apparatus provided with a heating zone.

  According to the method described in Patent Document 2, the temperature inside the single crystal becomes uniform, and further, while maintaining this state, the stress inside the crystal accumulated during the growth is removed, and is generated after the single crystal is separated. Cracks are suppressed. Further, since the internal stress is relaxed, cracks generated during wafer deformation and processing are reduced, and a high-quality single crystal can be manufactured at low cost.

JP 2007-246320 A JP 2009-242150 A

  However, with the recent increase in the size of single crystals, even when the method for removing residual stress described in Patent Document 2 as described above is employed, distortion due to non-uniform temperature distribution in the crystals during single crystal cooling. Has increased, and cracks are likely to occur. In particular, when an aluminum oxide single crystal having a diameter of 8 inches or more is grown, cracks may occur from the bottom of the single crystal during cooling, and cracks may easily enter the single crystal. There has been a demand for a method for producing a single crystal that is less likely to occur.

  Then, an object of this invention is to provide the cooling method and manufacturing method of a single crystal which can prevent generation | occurrence | production of the crack at the time of cooling after single crystal growth, and a single crystal growth apparatus.

In order to achieve the above object, a cooling method of a single crystal according to one embodiment of the present invention is a cooling method of a single crystal for cooling a single crystal after growth,
In a state where the single crystal was separated from the raw material melt after development, a step of the raw material melt remaining in 坩堝内waits to solidify,
And lowering the grown single crystal and bringing it into contact with the raw material melt solidified in the crucible.

The method for producing a single crystal according to another aspect of the present invention includes a step of heating the raw material melt in the crucible and growing the single crystal in the raw material melt,
Waiting until the raw material melt remaining in the crucible is solidified in a state where the single crystal after growth is separated from the raw material melt;
And lowering the grown single crystal and bringing it into contact with the raw material melt solidified in the crucible.

A single crystal growth apparatus according to another aspect of the present invention includes a crucible capable of storing a raw material melt,
A heating element provided around the crucible;
A single crystal pulling means capable of pulling a single crystal grown in the raw material melt onto the crucible;
A temperature detecting means provided in the crucible and capable of detecting the temperature of the stored raw material melt;
When the single crystal grows in the raw material melt, the single crystal pulling means separates the single crystal from the raw material melt, and the temperature of the raw material melt detected by the temperature detecting means It is determined whether or not the raw material melt has solidified, and when it is determined that the raw material melt has solidified, the single crystal is brought into contact with the raw material melt with the single crystal solidified by the single crystal pulling means. Control means for lowering.

  According to the present invention, it is possible to reduce the strain on the bottom surface of the grown single crystal and to suppress the generation of cracks.

It is the figure which showed an example of the oxide single crystal growth apparatus for enforcing the cooling method and manufacturing method of the oxide single crystal which concern on embodiment of this invention. It is the figure which showed the state which cut | disconnected the oxide single crystal from the raw material melt. It is the figure which showed an example of the time change of the temperature in the furnace which the thermocouple is monitoring. It is a figure for demonstrating the process after the solidification of a residual melt. It is the figure which showed the analysis result of the temperature change of the single crystal at the time of cooling. FIG. 5A is a diagram showing the analysis result of the temperature change of the single crystal in the initial stage of cooling. FIG. 5B is a diagram showing the analysis result of the temperature change of the single crystal in the middle of cooling. FIG.5 (c) is the figure which showed the analysis result of the temperature change in the furnace of the late cooling stage.

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

  The method for cooling and producing an oxide single crystal according to the present invention includes the steps of putting a raw material for a single crystal into a crucible in a furnace body, heating and melting the raw material for a single crystal with a heating body provided on the side and bottom of the crucible, In the melt-solidification method in which the seed crystal is brought into contact with the liquid and the grown crystal is pulled up, after confirming that the residual melt is completely solidified, the solidified raw material melt is brought into contact with the bottom of the single crystal to cool the single crystal. It is characterized by performing.

1. FIG. 1 is a diagram showing an example of an oxide single crystal growing apparatus for carrying out a cooling method and a manufacturing method of an oxide single crystal according to an embodiment of the present invention.

  In the oxide single crystal growing apparatus, a crucible 10 for containing a raw material for oxide single crystal is provided, and is placed on a crucible shaft 20 that can move up and down. The crucible 10 for melting the oxide single crystal raw material differs depending on the type of the oxide single crystal raw material and cannot be generally defined. However, if it is for an aluminum oxide single crystal, it has heat resistance equal to or higher than its melting point. The crucible 10 having a desired size according to the application can be used. A side cylindrical heater 31 is arranged around the side surface of the crucible 10 in order to melt the raw material for oxide single crystal. In addition, a disc-shaped bottom disc heater 32 is disposed below the crucible 10 so that the crucible shaft 20 passes therethrough. The side cylindrical heater 31 and the bottom disk heater 32 constitute the entire heater (heating body) 30 of the oxide single crystal growing apparatus. A heat insulating material 50 is provided around the side cylindrical heater 31 and below the bottom disk heater 32 along the chamber 60 of the oxide single crystal growth apparatus. A pulling shaft 40 that can move up and down is installed above the crucible 10. A seed crystal can be attached to the pulling shaft 40, and a heat insulating material 50 is provided so that the pulling shaft 40 penetrates the upper surface.

  Further, a thermocouple 70 is provided so as to penetrate the chamber 60 and not penetrate the heat insulating material 50. The thermocouple 70 is a temperature detector for detecting and monitoring the temperature change of the raw material melt 90 by detecting the temperature change in the furnace, more specifically, the temperature change around the crucible 10 and the heating body 30. It is. The thermocouple 70 can detect a temperature change of the raw material melt 90 to detect whether the raw material melt 90 is solidified, that is, whether it is in a molten state or a solidified state. The thermocouple 70 is provided outside the heater 30 rather than in the crucible 10 or in the region inside the heater 30 because the raw material melt 90 has a high temperature of 2000 ° C. or higher. That is, the thermocouple 70 is provided outside the raw material melt 90, but if the temperature of the raw material melt 90 changes, the ambient temperature also changes and the temperature in the heat insulating material 50 also changes. In order to detect the temperature change of the melt 90 and determine whether or not the melt 90 is solidified, if it is provided in the heat insulating material 50, it can sufficiently fulfill its role. In this embodiment, an example in which three thermocouples 70 are provided in the heat insulating material 50 is given as an example of the temperature detector. However, it is possible to detect whether or not the raw material melt 90 has solidified. If possible, an arbitrary number of various temperature sensors can be provided at an arbitrary location according to the application.

  Moreover, the oxide single crystal growth apparatus according to the present embodiment includes a control unit 80 that controls the operation of the entire oxide single crystal growth apparatus in order to perform the cooling method and the manufacturing method of the single crystal according to the present embodiment. . The controller 80 gives an operation command to each component of the oxide single crystal growth apparatus and controls the operation of each component. For example, the control unit 80 controls the vertical movement of the lifting shaft 40 and its timing. Although details will be described later, in the cooling method and the manufacturing method of the single crystal according to the present embodiment, after the single crystal 100 is separated from the raw material melt 90, the pulling shaft 40 is stopped in the separated state and detected by the thermocouple 70. When it is determined from the measured temperature that the raw material melt 90 has solidified, an operation of lowering the pulling shaft 40 is performed. Therefore, since the control unit 80 has a function of controlling the vertical movement of the pulling shaft 40 by inputting at least the detected temperature of the thermocouple 70, the thermocouple 70 and the pulling shaft 40 are at least electrically connected. Further, the vertical movement of the lifting shaft 40 is provided with an actuator for the lifting shaft 40 (not shown), and the controller 80 issues an operation command to the actuator of the lifting shaft 40 to control the operation of the lifting shaft 40. The control unit 80 may have various configurations as long as it has an arithmetic processing function. For example, a storage unit such as a CPU (Central Processing Unit) and a ROM (Read Only Memory) or a RAM (Random Access Memory) And an ASIC (Application Specific Integrated Circuit) formed as an integrated circuit for a specific application.

  The seed crystal is an oxide crystal with high purity. For example, if it is an aluminum oxide crystal, it is preferably obtained by a production method such as the Czochralski method, Kilopros, or HEM, and is appropriately selected depending on the use of the single crystal product. can do.

  The oxide single crystal growth apparatus is not limited to the above-described configuration. For example, an L-shaped or cup-shaped side heater may be used instead of the bottom disk-type heater 32, and there is no bottom disk-type heater 32. Only the cylindrical heater 31 may be used. In addition, the oxide single crystal growth apparatus can be provided with means for reducing the pressure inside the furnace, means for monitoring the degree of pressure reduction, and means for supplying nitrogen or an inert gas into the furnace, as necessary.

2. Melting of Oxide Single Crystal Raw Material In the oxide single crystal cooling method and manufacturing method according to the embodiment of the present invention, first, the oxide single crystal raw material is put into the crucible 10 using the above-described oxide single crystal growth apparatus. After putting, the crucible 10 is heated by the side cylindrical heater 31 and the bottom disk heater 32 to melt the raw material.

  As the raw material for oxide single crystal, various oxide powders such as aluminum oxide powder, lithium tantalate powder, or niobium oxide powder can be used. The aluminum oxide powder preferably used in the embodiment of the present invention is an aluminum oxide powder substantially composed of two elements of Al and O.

  The raw material for oxide single crystal is put into the crucible 10 and the crucible 10 is heated by the side cylindrical heater 31 and the bottom disk heater 32 to melt the raw material. The heating rate until the oxide single crystal raw material reaches the melting point is not particularly limited, but it is rapidly heated to suppress bumping phenomenon caused by uneven heating of the oxide single crystal raw material. It is better to heat gradually over a long period of time. Therefore, it is desirable to heat gradually, for example over 10 hours, especially over 12 hours. Next, even after melting the raw material for oxide single crystal, the obtained raw material melt 90 is heated for 3 hours or more, particularly 5 hours or more so that the furnace temperature is increased by 10 to 20 ° C. The temperature at this time is measured using a thermocouple inserted into a heat insulating material on the outer periphery of the heater.

  At this time, the inside of the furnace is an inert gas atmosphere, but the pressure may be reduced if necessary. However, when oxygen is introduced, the heater is oxidized and rapidly deteriorates. Therefore, it is desirable to dissolve the raw material for single crystal in a low oxygen concentration atmosphere containing almost no oxygen.

3. Single crystal growth and pulling In the growth of the single crystal 100, the upper end position of the crucible 10 is set to a range from 2 cm lower to 6 cm higher than the upper end of the side cylindrical heater 31, and 2 cm or more above the particularly matched position. It is desirable to start the growth of the single crystal by melting the raw material in accordance with the position. Thereby, after the growth of the single crystal 100 is completed, the crucible shaft 20 is lowered to facilitate separation of the grown oxide crystal and the raw material melt.

  In order to suppress the generation of grain boundaries in the oxide single crystal 100, it is necessary to increase the temperature gradient in the pulling axis direction in the vicinity of the solid-liquid interface. For this purpose, the crucible is a side cylindrical type in the vicinity of the solid-liquid interface. It is preferable to start crystal growth after disposing it in a shape that blocks radiation from the heater.

  FIG. 1 shows a state where the oxide single crystal 100 is grown from the raw material melt 90. As shown in FIG. 1, after the raw material is melted, the seed crystal is brought into contact with the raw material melt 90 to pull up the grown single crystal 100. According to a conventional method, the number of rotations and the pulling speed are adjusted to form the neck portion and the shoulder portion of the single crystal 100, and then the straight body portion is formed. At this time, it is preferable to measure the temperature of the melt surface in the vicinity of the interface between the single crystal 100 and the raw material melt 90 using a radiation thermometer or the like. The crystal shape can be adjusted by measuring the crystal weight during growth, deriving the diameter, growth speed, and the like by calculation, and adjusting the rotation speed and pulling speed. The seed crystal is preferably rotated at 0.2 to 20 rpm. The rotation speed of the seed crystal is preferably 1 to 10 rpm. In addition, the melt temperature can be controlled by feeding back the change in crystal weight.

4). Then, when the oxide single crystal 100 is sufficiently grown, the oxide crystal is separated from the raw material melt 90. At this time, in a state where the temperature gradient near the solid-liquid interface is large, stress is generated in the grown crystal, and internal stress is accumulated in the single crystal 100 during the growth. Therefore, the crucible shaft 20 is lowered at the end of growth, and the grown oxide single crystal 100 and the raw material melt 90 are separated.

  At that time, as shown in FIG. 2, the single crystal 100 is held such that the straight body upper end 101 of the grown single crystal 100 is positioned below the upper end of the side cylindrical heater 31. If the straight barrel upper end 101 of the grown single crystal 100 is in a range located below the upper end of the side cylindrical heater 31, the crucible shaft 20 is lowered and the pulling shaft 40 is moved upward to move the single crystal It may be possible to raise 100 and increase the separation speed.

  The separation distance of the single crystal 100 by the movement of the crucible 10 is 1 to 15 cm, preferably 2 to 10 cm. If it is less than 1 cm, if the single crystal 100 is large, the single crystal 100 cannot be completely separated from the raw material melt 90. If the distance exceeds 15 cm, it is not preferable because a large moving space for the crucible 10 must be secured. It is.

5. Cooling of the oxide single crystal After the oxide single crystal 100 is cut off, when the electric power supplied to the heater 30 is gradually lowered, the temperature in the furnace is also lowered, and the residual melt 90 remaining at the bottom of the crucible 10 is solidified. To do. When the residual melt 90 is solidified, solidification heat is generated, and the temperature indicated by the thermocouple 70 monitoring the inside of the furnace (around the crucible 10) rises once regardless of being cooled, and the residual melt 90 When solidifies completely, the temperature in the furnace starts to drop.

  FIG. 3 is a diagram showing an example of a temporal change in the temperature in the furnace monitored by the thermocouple 70. In FIG. 3, the horizontal axis represents time, and the vertical axis represents the detected temperature (° C.) of the thermocouple 70. As shown in FIG. 3, the detected temperature is affected by the heat of solidification generated when the residual raw material melt 90 is solidified, and has a peak point P that rapidly increases and then rapidly decreases. And time T1 when temperature fell after the peak point P passed has shown the time of the residual melt 90 solidifying. When the controller 80 recognizes that the temperature change of the residual melt 90 indirectly monitored by the thermocouple 70 has a peak point P as shown in FIG. 3, the residual melt 90 has solidified. judge.

  FIG. 4 is a view for explaining the processing after the residual melt 90 is solidified.

  As described above, when the temperature in the furnace is monitored and it is confirmed that the residual melt 90 is completely solidified, the control unit 80 controls the pulling shaft 40 and moves the pulling shaft 40 downward as shown in FIG. Move to. Then, the solidified raw material melt 91 and the bottom of the single crystal 100 are brought into contact with each other to cool the single crystal 100. That is, the pulling shaft 40 is lowered, and when the bottom of the single crystal 100 comes into contact with the solidified upper surface of the raw material melt 91, the pulling shaft 40 is stopped.

  Thereafter, the separated oxide single crystal 100 is cooled to near room temperature at a cooling rate of 1 ° C. to 3 ° C./min, and then the oxide single crystal 100 is taken out from the single crystal growth apparatus.

  In this way, by bringing the bottom surface of the single crystal 100 into contact with the surface of the solidified residual material melt 91, the lower portion of the single crystal 100 is integrated with the residual raw material melt 91 that has been thermally solidified, and a uniform temperature distribution is obtained. The area becomes wider. That is, not only the route through the upper pulling shaft 40 but also the route through the lower residual material melt 91 and the crucible shaft 20 are added as a transmission path for releasing heat. Thereby, the heat of the single crystal 100 can be released to the outside from above and below. Thereby, the distortion of the bottom face of the single crystal 100 is reduced, and the generation of cracks is suppressed. Further, during the cooling of the single crystal 100, the single crystal 100 is not in a state in which only the neck portion is supported by the pulling shaft 40, but is in a state in which the lower surface is supported from below by the solidified residual material melt 91. It is possible to prevent the neck portion from being damaged and falling from the pulling shaft 40.

〔Example〕
Next, examples in which the single crystal cooling method and the manufacturing method according to the present embodiment are implemented using the single crystal growth apparatus according to the present embodiment will be described.

  The structure of the crystal growth furnace and the position of the crystal during cooling are shown in FIG. For ease of understanding, the same reference numerals are assigned to the same components as those described in the present embodiment.

  A crucible 10 having a diameter of 300 mm and a height of 300 mm is installed in the growth furnace, and a resistance heating type side cylindrical heater 31 and a bottom disk type heater 32 are attached to the side surface and the lower portion, respectively. Around the crucible 10, a carbon felt is installed as a heat insulating material 50.

  An aluminum oxide single crystal 100 having a diameter of about 200 mm and a length of 280 mm was grown from the aluminum oxide raw material melt 90 in the crucible 10. As shown in FIG. 2, after the growth of the single crystal, the aluminum oxide single crystal 100 is raised 1 cm above the surface of the raw material melt 90, and the position of the crucible 10 is lowered by 10 cm, whereby the single crystal 100 is removed from the raw material melt. Disconnected from 90, cooling was started by gradually decreasing the output of the heater.

  Thereafter, as shown in FIG. 3, the thermocouple 70 monitoring the temperature change in the furnace solidifies the raw material melt 90 remaining in the crucible 10 to generate heat of solidification, and the temperature is When a temperature change that once rises and then turns down is detected, as shown in FIG. 4, the pulling shaft 40 is moved downward by a command from the control unit 80, and the solidified raw material melt 91 and the bottom of the single crystal 100 are moved. The single crystal 100 was cooled by contact.

  During cooling, the output of the heater 30 was lowered linearly to be 0 in 20 hours, and after cooling, the single crystal 100 taken out was observed, and no cracks were observed.

[Comparative example]
When a single crystal was grown under the same conditions as in the example and cooled while being held at a position separated from the surface of the raw material melt, cracks were generated in the single crystal that was taken out. When the diameter of the aluminum oxide single crystal was 300 mm, almost all cracks were generated.

  Thus, according to the Example of this invention, it was shown that generation | occurrence | production of a crack is suppressed compared with a comparative example.

  In addition, inventors etc. started from the analysis of the temperature change of the single crystal in the growth furnace at the time of cooling in creating this invention. That is, when the present inventors analyzed the temperature change of the single crystal in the growth furnace during cooling, in the cooling process, the heat escapes through the seed crystal holder at the top of the single crystal, and the temperature at the bottom of the single crystal decreases. The temperature is lowered by radiation to the melt surface and heat transfer through the gas in the gap between the residual raw material melt surface and the bottom surface of the single crystal.

  FIG. 5 is a diagram showing the analysis result of the temperature change of the single crystal during cooling performed by the inventors. FIG. 5A shows the analysis results of the temperature change in the furnace at the initial stage of cooling, FIG. 5B shows the middle period of cooling, and FIG. 5A to 5C, regions A, B, C, D, and E are shown in the order of higher temperatures.

  As shown in FIGS. 5 (a) to 5 (c), from this analysis result, the temperature of the central part of the lower part of the single crystal is the highest in the single crystal, and a temperature gradient is generated in the vertical direction around this central part. And the knowledge that a temperature gradient became large with progress of cooling time was acquired.

  The cause of cracks in the single crystal is the temperature distribution in the single crystal during cooling. If this temperature distribution is large, distortion due to thermal shrinkage occurs, and it can be estimated that cracks will occur when the ultimate tensile stress is reached. Therefore, it is considered that reducing the temperature while keeping the temperature in the single crystal uniform leads to reducing the occurrence of cracks due to thermal strain. In particular, since cracks are generated on the bottom surface of the single crystal, it is important to make the temperature at the bottom of the single crystal uniform.

  The present invention has been made based on such knowledge, and at the time of cooling after growing a single crystal, after the surface of the raw material melt remaining in the crucible solidified, the position of the single crystal was lowered and solidified. By cooling the single crystal by bringing the raw material melt into contact with the bottom of the single crystal, the lower portion of the single crystal is thermally integrated with the residual raw material melt, and the uniform temperature distribution region is widened, thereby reducing the distortion of the bottom surface of the single crystal. And the occurrence of cracks is suppressed.

  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 crucible 20 crucible shaft 30 heater (heating body)
31 Side cylindrical heater 32 Bottom disk type heater 40 Lifting shaft 50 Heat insulating material 60 Chamber 70 Thermocouple 80 Control unit 90, 91 Raw material melt 100 Single crystal

Claims (8)

A method of cooling a single crystal that cools the grown single crystal,
In a state where the single crystal was separated from the raw material melt after development, a step of the raw material melt remaining in 坩堝内waits to solidify,
A step of lowering the grown single crystal and bringing it into contact with the raw material melt solidified in the crucible.   The method for cooling a single crystal according to claim 1, wherein the solidification of the raw material melt is determined by monitoring a temperature change of the raw material melt.   The method for cooling a single crystal according to claim 2, wherein it is determined that the raw material melt has solidified when the temperature change shows a peak that rapidly increases and then decreases rapidly. Around the crucible, a heating body for heating the crucible is provided,
The single crystal after growth waits for the raw material melt remaining in the crucible to solidify in a state where the straight body portion is at a position below the upper end of the heating body. The method for cooling a single crystal according to any one of the above. Heating the raw material melt in the crucible and growing a single crystal in the raw material melt;
Waiting until the raw material melt remaining in the crucible is solidified in a state where the single crystal after growth is separated from the raw material melt;
Lowering the grown single crystal and bringing it into contact with the raw material melt solidified in the crucible.   The method for producing a single crystal according to claim 5, wherein the solidification of the raw material melt is determined by monitoring a temperature change of the raw material melt.   The method for producing a single crystal according to claim 6, wherein it is determined that the raw material melt has solidified when the temperature change shows a peak that rapidly increases and then decreases rapidly. Around the crucible, a heating body for heating the crucible is provided,
The grown single crystal waits for the raw material melt remaining in the crucible to solidify in a state where the straight body portion is at a position below the upper end of the heating body. The manufacturing method of the single crystal as described in any one of these .