JP2019189488A - Single crystal manufacturing method - Google Patents

Abstract

To provide a single crystal manufacturing method that suppresses quantity of deformation of a crucible without changing crucible shape.SOLUTION: The single crystal manufacturing method is provided in which raw material for a single crystal is charged into in a crucible 10 in a furnace body, the crucible 10 is heated by a high-frequency induction coil 50 for induction heating, then a seed crystal is brought into contact with raw material melt, thereby manufacturing a single crystal. The single crystal manufacturing method includes the steps of: preparing the raw material melt while a first relative position represents a height-directional relative position between a center position of coil length of the high-frequency induction coil 50 and a bottom surface 11 of the crucible; and growing the single crystal while a second relative position represents the height-directional relative position between the center position of coil length of the high-frequency induction coil 50 and the bottom surface 11 of the crucible. The distance between the center position of coil length of the high-frequency induction coil 50 and the bottom surface 11 of the crucible at the first relative position is longer than the distance between the center position of coil length of the high-frequency induction coil 50 and the bottom surface 11 of the crucible at the second relative position.SELECTED DRAWING: Figure 2

Description

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

  As a method for producing a single crystal, a pulling method represented by the Czochralski method (Cz method) has been conventionally used. For example, many crystals such as silicon and sapphire are produced by the pulling method. There are various forms of melting of the crystal raw material, but oxide single crystals such as sapphire and lithium tantalate have a high melting point, so refractory metals such as iridium, tungsten, molybdenum, and platinum, and alloys based on them are used. Used for crucibles.

  The crucible is often used repeatedly from the viewpoint of productivity and economy, and the crucible that has been used many times is deformed by repeated heating and cooling. A crucible exceeding a certain amount of deformation deteriorates the symmetry of the heat distribution, and the yield at the time of manufacturing a single crystal decreases due to convective changes accompanying the deterioration of the shape, so that the crucible needs to be replaced. As the number of single crystal productions up to the replacement of the crucible increases, the economic efficiency increases. Therefore, it is important to suppress crucible deformation.

  As a method of suppressing the amount of deformation of the crucible, in Patent Document 1, the amount of deformation is suppressed by increasing the thickness of the portion where the amount of deformation is large, which is excellent in strength and difficult to deform, and can withstand repeated use. , Running costs can be reduced. Further, in Patent Document 2, since the crucible structure is such that the plate thickness on the bottom side of the crucible is made thinner than the side surface direction and the deformation is released to the side surface on which the plate thickness is thin, the crucible is hardly deformed in the lateral direction.

JP 2017-214229 JP2012-250874A

  However, the conventionally proposed methods need to change the structure of the crucible itself, so that it is economical, such as an increase in the weight of the metal used for the crucible and an increase in processing costs due to the complicated crucible shape. The burden was large.

  Then, in view of the problem which the said prior art has, this invention aims at providing the manufacturing method of the single crystal which suppresses the deformation amount of a crucible, without accompanying a crucible shape change.

In order to achieve the above object, a method for producing a single crystal according to one embodiment of the present invention includes: placing a raw material for a single crystal in a crucible in a furnace body; and heating the crucible with a high-frequency induction coil for induction heating. In the method for producing a single crystal in which a single crystal is produced by bringing a seed crystal into contact with the raw material melt after heating and melting,
Producing a raw material melt with a relative position in the height direction between the center position of the coil length of the high-frequency induction coil and the bottom surface of the crucible as a first relative position;
And growing a single crystal with a relative position in the height direction between the center position of the coil length of the high-frequency induction coil and the bottom surface of the crucible as a second relative position.

  According to the present invention, the amount of deformation of the crucible can be suppressed even if the number of single crystal productions is repeated, and a single crystal can be obtained with high economic efficiency.

It is the schematic which showed an example of the crystal growth apparatus used for the manufacturing method of the single crystal which concerns on embodiment of this invention. It is a figure for demonstrating the relative position of a crucible and a high frequency induction coil in a raw material melting process. It is the figure which showed an example of the relative position of the crucible and the high frequency induction coil in a single crystal growth process. It is the figure which showed the positional relationship of the crucible at the time of the crystal raw material melting | fusing of the comparative example 2, and a high frequency induction coil.

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

  First, a configuration example of a crystal growth apparatus suitable for carrying out the method for producing a single crystal according to the embodiment of the present invention will be described below.

  FIG. 1 is a schematic diagram showing an example of a crystal growth apparatus used in a method for producing a single crystal according to an embodiment of the present invention. As shown in FIG. 1, the crystal growing apparatus includes a crucible 10, a crucible base 20, a crucible shaft 21, a crucible shaft drive motor 22, a reflector 30, an after heater 40, a high-frequency induction coil 50, and heat insulation. A material 60, a furnace body 70, a pulling shaft 80, a seed crystal holding jig 81, a pulling shaft driving motor 82, a weight measuring unit 90, a thermometer 100, and a control unit 110 are provided.

  Further, in the crucible 10, the raw material melt 140 is stored, the seed crystal 120 held in the seed crystal holding jig 81, and the single crystal 130 pulled up by the pulling shaft 80 are shown.

  In the crystal growing apparatus, the crucible 10 is placed on the crucible base 20. A crucible shaft 21 is connected to the lower surface of the crucible base 20 and is configured to be rotatable by a crucible shaft drive motor 22.

  An after heater 40 is installed above the crucible 10 via a reflector 30. A high frequency induction coil 50 is provided so as to surround the crucible 10, the reflector 30, and the after heater 40. Further, a heat insulating material 60 is installed so as to surround the crucible 10, the reflector 30, the after heater 40 and the high frequency induction coil 50. A furnace body 70 is provided outside the heat insulating material 60 to cover the entire periphery of the heat insulating material 60.

  A pulling shaft 80 is provided above the crucible 10. The pulling shaft 80 has a seed crystal holding jig 81 at the lower end, and is configured to be lifted and lowered by a pulling shaft driving motor 82. At the upper end of the pulling shaft 80, a weight measuring unit 90 is provided so that the weight of the single crystal 130 can be measured. Further, a control unit 110 is provided outside the furnace body 70.

  Although not shown, a power source for supplying power to the high-frequency induction coil 50 and the entire crystal growth apparatus is provided outside the furnace body 70.

  Next, individual components will be described.

  The crucible 10 is a container for storing and holding the raw material melt 140 and growing the single crystal 130. The crystal raw material is held in a raw material melt 140 in which a metal to be crystallized is melted. The material of the crucible 10 is made of heat-resistant platinum, iridium, platinum rhodium or the like although it depends on the crystal raw material.

  The crucible table 20 is provided as a mounting table 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 high-frequency induction coil 50 and durability to support the crucible 10.

  The crucible shaft 21 is an elevating mechanism for elevating the crucible base 20, and includes an elevating mechanism such as a ball screw that converts the horizontal rotation of the crucible shaft 21 into an elevating operation. That is, when the crucible shaft 21 rotates, the crucible base 20 can be moved up and down by a ball screw or the like.

  The crucible shaft drive motor 22 is a rotational drive mechanism that rotates the crucible shaft 21, and is configured so that the crucible 10 placed on the crucible table 20 moves up and down by the vertical movement of the crucible table 20.

  The reflector 30 is a heat reflecting means for reflecting the heat in the heated crucible 10 and returning it to the crucible 10. The reflector 30 is attached to the upper end of the side surface of the crucible 10 so as to cover the peripheral edge of the upper end of the side surface of the crucible 10. Provided. Therefore, the reflector 30 has an annular shape. The reflector 30 is also made of a metal material. The reflector 30 may be made of various metal materials, but may be made of iridium, platinum, or the like having excellent heat resistance, for example, like the crucible 10.

  Since the single crystal 130 to be grown moves away from the crucible 10 as the pulling of the single crystal 130 progresses, the temperature distribution of the single crystal 130 becomes large, and problems such as cracking of the single crystal 130 may occur. In order to improve this, the above-mentioned after heater 40 is installed above the crucible 10 to maintain an appropriate temperature distribution.

  The after heater 40 is a heating means for heating the single crystal pulled up from the crucible 10. The after heater 40 is provided on the reflector 30 and has a cylindrical shape. Since the reflector 30 is thin, the after heater 40 is provided substantially continuously above the crucible 10 in the height direction.

  That is, the single crystal raw material filled in the crucible 10 can be melted by heating to produce the raw material melt 140. However, in order to improve heat retention and adjust the temperature gradient, the cylindrical afterheater 40 is used. Is placed above the crucible 1.

  The after heater 40 is also made of a metal material. The after-heater 40 may also be composed of various metal materials. For example, like the crucible 10, it may be composed of iridium, platinum, etc. excellent in heat resistance, and is composed of the same material as the crucible 10. Also good.

  The high frequency induction coil 50 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 high frequency induction coil 50 may be in any form as long as the crucible 10, the reflector 30, and the after heater 40 can be induction heated. For example, the high frequency induction coil 50 is configured as a high frequency induction heating device including a high frequency heating coil.

  The high frequency induction coil 50 may be configured to be driven in the vertical direction. Thereby, the relative position of the high frequency induction coil 50 with respect to the crucible 10 can be arbitrarily changed. Further, it can be driven at a constant speed by program control.

  As will be described in detail later, the crystal growing apparatus is configured to be able to change the relative position between the crucible 10 and the high-frequency induction coil 50. As described above, the crucible base 20 may be configured to be movable up and down, or the high-frequency induction coil 50 may be configured to be movable up and down. Further, both the crucible base 20 and the high frequency induction coil 50 may be configured to be movable up and down. That is, the crystal growing apparatus used in the method for producing a single crystal according to the embodiment of the present invention is configured such that at least one of the crucible base 20 and the high frequency induction coil 50 can be moved up and down.

  The ratio of the height of the high frequency induction coil 50 to the crucible 10 and the after heater 40 is such that when the height of the after heater is 1, the high frequency induction coil 50 has a height of 3.5 to 4.5, The height can be set to a ratio of 2.5 to 3.5.

  The heat insulating material 60 is a means for covering the periphery of the crucible 10 and suppressing the release of heat to the outside.

  The furnace body 70 holds the heat generated by the high-frequency induction coil 50 of the crucible 10 and the after heater 40 inside, and plays a role of preventing discharge to the outside. The furnace body 70 is made of a material having high heat resistance. The furnace body 70 has an opening 61 on the ceiling surface, and is configured such that the lifting shaft 80 can be inserted.

  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 140 held in the crucible 10, and pulling up the single crystal 130 while rotating. The pulling shaft 80 has a seed crystal holding jig 81 for holding the seed crystal 120 at the lower end portion, and includes a pulling shaft driving motor 82 including a motor as a rotation mechanism. The motor is a rotation drive mechanism for performing an operation of pulling up the crystal while rotating the crystal.

  The weight measuring unit 90 is a weight measuring unit for measuring the weight of the single crystal 130.

  The thermometer 100 is temperature measuring means for measuring the temperature of the bottom surface of the crucible 10. The thermometer 100 functions as a means for knowing that the raw material in the crucible 10 has melted into the raw material melt 140 by measuring the temperature of the bottom surface of the crucible 10. In FIG. 1, a configuration in which the thermometer 100 is disposed so as to be embedded in the central portion of the crucible base 20 is shown, but the thermometer 100 can be variously arranged and arranged as long as the bottom surface temperature of the crucible 10 can be measured. It can be configured.

  The controller 110 is a means for controlling the entire crystal growth apparatus, and controls the operation of the entire crystal growth apparatus including the crystal growth process. For example, the control unit 110 includes a CPU (Central Processing Unit), a central processing unit, and a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and may be configured by a microcomputer that operates according to a program. However, it may be composed of an electronic circuit such as an ASIC (Application Specified Integrated Circuit) developed for a specific application.

  In addition to the members shown in FIG. 1, various members necessary for growing a single crystal can be provided in the crystal growing apparatus. For example, in order to control the atmosphere in the furnace body 70, gas supply means, exhaust means, pressure measurement means, and the like can be provided. In addition, in order to control the output by the heating body, a temperature measuring means is provided at an arbitrary place in the furnace body 70, and observation for confirming the state of the raw material melt 140 and seed crystal in the furnace body 70 A window or the like can also be provided.

  Next, a method for producing a single crystal according to an embodiment of the present invention will be described. An example using the crystal growth apparatus shown in FIG. 1 will be described.

  In the method for producing a single crystal according to the present embodiment, the relative position in the height direction between the crucible 10 and the high frequency induction coil 50 is changed during melting of the raw material and during crystal growth. Specifically, the relative position between the bottom surface of the crucible 10 and the center position of the coil length of the high frequency induction coil 50 is changed. That is, at the time of crystal growth, the relative position between the crucible 10 and the high frequency induction coil 50 is determined and standardized to some extent from existing processes from the viewpoint of manufacturing a single crystal having a certain quality.

  On the other hand, when the raw material is melted, there is no specific condition at the relative position between the crucible 10 and the high frequency induction coil 50 as long as the raw material can be melted. In other words, there is no detailed process condition because it is a preparatory step before a specific single crystal manufacturing process is performed. Therefore, when the raw material is melted, the relative position between the crucible 10 and the high frequency induction coil 50 is not necessarily the same as that during the growth of the single crystal.

  The crucible 10 can be deformed by repeating heating and cooling. In order to suppress such deformation, it is preferable to reduce the amount of heating applied to the crucible 10 as much as possible. Therefore, in the method for producing a single crystal according to the present embodiment, the distance between the high-frequency induction coil 50 and the crucible 10 is increased during raw material melting, the amount of heating to the crucible 10 is reduced, and the load on the crucible 10 is reduced. Let

  More specifically, the present inventors have intensively studied to solve such conventional problems, and have found that the amount of deformation of the crucible 10 is suppressed by controlling the amount of heat generated on the side of the crucible.

  In the single crystal growth, the positions of the crucible 10 and the high-frequency induction coil 50 are adjusted so that an optimum temperature environment is obtained during crystal growth. By adjusting the positional relationship between the crucible 10 and the high-frequency induction coil 50, it is possible to adjust the convection of the molten raw material in the crucible 10 and the temperature gradient in the space above the crucible to the optimum conditions for single crystal growth, and manufacture products with high yield. Is possible.

  The amount of heat generated by the crucible 10 is determined by the magnitude of current generated during induction heating. In the case of the high-frequency induction coil 50 with equal winding intervals, the magnetic flux is most concentrated in the state where the crucible 10 and the after-heater 40 are not arranged, that is, the central portion from the beginning of winding to the end of winding, that is, half the coil length. Position. In single crystal growth, the amount of heat generated by the crucible 10 is adjusted by aligning the central axes of the crucible 10 and the high-frequency induction coil 50 and moving the position of the high-frequency induction coil 50 relative to the crucible 10. Usually, when the coil center and the crucible center are aligned, the magnetic flux concentrates on the end of the crucible bottom, and the crucible lower portion tends to become high temperature.

  Since an appropriate convection and temperature gradient are required during single crystal growth, the amount of heat generated by the crucible is generally larger as it is closer to the bottom of the crucible and smaller as it is closer to the upper end of the crucible. In the case of the arrangement of the crucible and the high-frequency induction coil that can achieve the above-described conditions, the crucible lower portion having a higher temperature is more easily deformed than the crucible upper portion having a lower temperature.

  When crystal melting is performed at a crucible position suitable for crystal growth on the work coil, magnetic flux concentrates at the lower part of the crucible, and the lower part of the crucible becomes unnecessarily high. In this state, the weight of the raw material melt is added to the lower part of the crucible softened at a high temperature, which causes deformation of the crucible. Therefore, by using a method of lowering the position of the crucible with respect to the work coil and melting the raw material by melting the raw material by melting the raw material of the crystal, it is found that excessive heating of the lower portion of the crucible can be prevented and deformation can be suppressed. It came.

  FIG. 2 is a view for explaining the relative positions of the crucible 10 and the high-frequency induction coil 50 at the time of raw material melting, that is, in the raw material melting step. In FIG. 2, in order to explain the relative position in the height direction, in order to facilitate understanding, a configuration in which the after heater 40 is provided directly above the crucible 10 instead of the upper inside of the crucible 10 is shown. Yes.

  When a single crystal is grown by the crystal growing apparatus having the configuration described with reference to FIG. 1, first, the raw material for single crystal filled by heating the crucible 10 with the high-frequency induction coil 50 is melted to produce a raw material melt 140. In the method for producing a single crystal according to the present embodiment, when this raw material melt is produced, the half position (0.5 L) of the coil length L of the high frequency induction coil 50 sets the bottom surface 11 of the crucible 10 to 0%. The upper end 41 of the after heater 40 is disposed so as to fall within a range of 45% (0.45H) to 55% (0.55H) when the upper end 41 is 100% (H).

  In FIG. 2, the center position (0.5 L) of the coil length of the high frequency induction coil 50 is exactly half the height when the height from the bottom surface 11 of the crucible 10 to the upper end 41 of the after heater 40 is H. The arrangement | positioning arrange | positioned so that it may correspond to the position of 0.5H which becomes is shown.

  As shown in FIG. 2, the center position (0.5 L) of the coil length (coil height) of the high-frequency induction coil 50 is the height H between the bottom surface 11 of the crucible 10 and the upper end 41 of the after heater 40. The raw material in the crucible 10 is melted by heating the high-frequency induction coil 50 while maintaining the relative position within the range of 45% (0.45H) to 55% (0.55H), and the raw material melt 140 is generated. The state of the raw material melt 140 can be known by the thermometer 100 that measures the bottom surface of the crucible 10. That is, the temperature at which the raw material is melted to become the raw material melt 140 is grasped in advance, and the target temperature is set to a temperature higher than that. That is, the target temperature of the bottom surface of the crucible 10 is set so that the raw material is surely melted and the raw material melt 140 is in a prepared state.

  The relative position between the crucible 10 and the high frequency induction coil 50 in the raw material melting step is referred to as a first relative position.

  FIG. 3 is a diagram showing an example of a relative position between the crucible 10 and the high-frequency induction coil 50 in the single crystal growing step. Before entering the single crystal growth step, the crucible base 20 or the high frequency induction coil 50 is moved to change the relative positions of the crucible 10 and the high frequency induction coil 50 in the height direction. Specifically, for example, the relative position is changed as shown in FIG. In FIG. 3, the height or distance from the bottom surface 11 of the crucible 10 to the upper end 41 of the after heater 40 is set to H at the center position or half position (0.5 L) in the coil length L of the high frequency induction coil 50. As an example, a relative position where a position of 37% (0.37H) is disposed when the bottom surface 11 of 10 is 0% and the upper end 41 of the after heater 40 is 100% is shown.

  The relative position shown in FIG. 3 is a state in which the distance in the height direction between the bottom surface 11 of the crucible 10 and the high frequency induction coil 50 is shorter than that in FIG. In the single crystal growth step, conditions for growing the single crystal 130 with high quality are established, and the conditions for the relative positions of the crucible 10 and the high frequency induction coil 50 are often established. Therefore, in the single crystal growing step, the relative position between the crucible 10 and the high frequency induction coil 50 is set according to such established conditions. On the other hand, since the conditions of the raw material melting step do not directly affect the quality of the single crystal 130, if the purpose of melting the raw material to obtain the molten raw material 140 can be achieved, Since there is no problem even if the heat load on the crucible 10 is reduced by increasing the distance, a different relative position is set in the raw material melting step and the single crystal growth step.

  In addition, the relative positions of the crucible 10 and the after heater 40 when growing the single crystal can be variously arranged depending on the application. The position of 0.37H shown in FIG. 3 is only an example until it gets tired, and an appropriate relative position can be determined according to the application and process conditions.

  As described above, when the relative position between the crucible 10 and the high frequency induction coil 50 when the single crystal is grown is referred to as a second relative position, the second relative position is obtained after melting the raw material at the first relative position. At least one of the crucible base 20 and the high-frequency induction coil 50 is moved so as to be set as follows. And it waits for the predetermined time in the state which maintained the 2nd relative position. This standby time is a time for waiting for the temperature state of the raw material melt 140 to reach a predetermined temperature state, whereby the temperature of the raw material melt 140 due to the relative movement between the crucible 10 and the high frequency induction coil 50. Wait for the fluctuations to disappear. Such a waiting time is set to about 2 to 5 hours, for example.

  Next, seeding can be performed by lowering the pulling shaft 80 and bringing the seed crystal 120 fixed to the tip of the seed crystal holding jig 81 into contact with the raw material melt 140. In the seeding operation in which the seed crystal 120 is brought into contact with the raw material melt 140, the seed crystal 120 is pulled at a predetermined speed after the seed crystal 120 is brought into contact with the raw material melt 140. The pulling speed can take an arbitrary value in order to obtain a predetermined diameter of the single crystal 130, but a pulling speed of 1 mm / hr to 20 mm / hr is preferable.

  Then, after performing the seeding operation, the single crystal 130 can be grown by operating the pulling shaft 80 and raising the seed crystal 120 while rotating it.

  In order to finish the crystal growth after the single crystal 13 having a desired size is obtained, an operation of separating the single crystal 13 and the raw material melt 14 is performed. This operation is performed by raising the pulling shaft 7 or lowering the crucible shaft 2 or both. After separating the raw material melt 140 and the grown single crystal 130, it is cooled and the single crystal 130 grown from the furnace body 70 can be taken out.

  However, since an apparatus equipped with the driving of the crucible shaft 21 is expensive and not economical, the detaching operation may be performed by only raising the pulling shaft 80 or combining lowering the crucible shaft 21.

  Next, an example of the set time in the raw material melting step of the method for producing a single crystal according to this embodiment will be described while comparing with a conventional example.

  Table 1 is a table showing an example of the set time in the raw material melting step of the method for producing a single crystal according to the present embodiment in comparison with the conventional example.

表１において、原料融解工程と坩堝移動工程（待機工程も含む）における設定時間の一例が示されている。設定時間としては、原料融解工程においては、昇温時間、目標温度到達時間、待機（保持）時間、原料融解合計時間が示されており、坩堝移動工程においては、坩堝移動時間と坩堝移動後待機時間が項目として示されている。また、表１の左側の欄は従来例であり、右側は本実施形態に係る単結晶製造方法の例である。なお、従来例とは、原料融解工程と単結晶育成工程における坩堝１０と高周波誘導コイル５０との相対位置が同一である例であり、本実施形態に係る単結晶の製造方法における例は、原料融解工程における坩堝１０と高周波誘導コイルとの相対位置と、単結晶育成工程における坩堝１０と高周波誘導コイルとの相対位置とが異なる例である。

In Table 1, an example of the set time in the raw material melting step and the crucible moving step (including the standby step) is shown. As the set time, the temperature raising time, target temperature arrival time, standby (holding) time, and raw material melting total time are shown in the raw material melting step, and in the crucible moving step, the crucible moving time and standby after crucible moving Time is shown as an item. Moreover, the left column of Table 1 is a conventional example, and the right column is an example of a single crystal manufacturing method according to the present embodiment. The conventional example is an example in which the relative positions of the crucible 10 and the high frequency induction coil 50 in the raw material melting step and the single crystal growing step are the same, and the example in the method for manufacturing a single crystal according to this embodiment is a raw material This is an example in which the relative position between the crucible 10 and the high frequency induction coil in the melting step and the relative position between the crucible 10 and the high frequency induction coil in the single crystal growing step are different.

  The temperature raising time is a time required for raising the temperature from the output zero state to the high frequency output set at the time of melting, and is 1 hour in the conventional example, and 0.75 hour in the present embodiment. Is set slightly shorter.

  The target temperature arrival time means a point where the temperature of the bottom surface 11 of the crucible 10 has risen completely, and for example, both are set to 7.5 hours.

  The melting time is the timing when the total amount of raw materials is dissolved in the melt, and is set to 7 hours in both the conventional example and this embodiment.

  The standby (holding) time is a time for adjusting to the seeding temperature after reaching the target temperature, and is set to 2.5 hours in the conventional example and 3.5 hours in the present embodiment. It is set longer by 1 hour. This is because the fluctuation due to the change in the relative position between the crucible 10 and the high frequency induction coil 50 is taken into consideration, and the standby time in this embodiment is longer than the conventional example in order to secure a sufficient time until the temperature fluctuation is settled. Is also set longer.

  The total raw material melting time is the total time of the target temperature arrival time and the standby time. The standby time is 1 hour longer, and this embodiment is 11 hours longer than the conventional example, and the conventional example is 10 hours. .

  In the crucible moving step, for example, the crucible moving time in this embodiment is set to 0.15 hours, that is, 9 minutes. In addition, the moving speed of the crucible 10 is set to 5 mm / min, for example. In the conventional example, since the relative position between the crucible 10 and the high frequency induction coil 50 is not changed, the crucible moving time is not set.

  The waiting time after the movement of the crucible is a time for which the crucible 10 waits after the movement, and is set to 3.35 hours, for example. This time is waited for the temperature of the raw material melt 140 to become constant. The total of the crucible moving time and the crucible moving standby time is 3.5 hours, which is the same as 3.5 hours in the raw material melting step. This means that the movement of the crucible 10 and the standby time are included in the standby time of the raw material melting step, and the movement of the crucible 10 is performed during the standby time of raw material melting.

  Therefore, even if the time for moving the crucible 10 is added, the time for the raw material melting step does not become much longer than that of the conventional one, but only extends for one hour. If it is about 1 hour, even if the time of the single crystal growth process is shortened by 1 hour, the overall throughput is not greatly affected. Therefore, as a whole, the amount of heating to the crucible 10 can be reduced without affecting the throughput.

  In addition, the time of Table 1 is the time given as an example until it gets tired, and the time listed in Table 1 can be variously changed depending on the use depending on the type of single crystal, the structure of the crystal growth apparatus, and the like. .

  As described above, according to the method for producing a single crystal according to the present embodiment, the relative distance between the crucible 10 and the high-frequency induction coil 50 is increased during raw material melting, the heating load on the crucible 10 is reduced, and the crucible 10 is deteriorated. Can be suppressed. Moreover, there is no significant influence on the growth time of the single crystal, and the life of the crucible 10 can be extended without reducing the throughput.

  Specific examples and comparative examples will be described below, but the present invention is not limited to these examples. FIG. 2 shows the positional relationship between the crucible 10 and the high-frequency induction coil 50 during melting of the crystal material of Examples 1 to 3, FIG. 3 to Comparative Example 1, and FIG. In the following description, for ease of understanding, components corresponding to those described in the embodiments so far are described with the same reference numerals.

(Example 1)
A lithium tantalate single crystal was grown using the crystal apparatus having the configuration shown in FIG. Half of the total length H (350 mm) of the length of the crucible 10 (250 mm) and the length of the after heater 40 (100 mm) at a position (0.5 L) of the coil length L (400 mm) of the high-frequency induction coil 50 Position (0.5H) was arranged (first relative position). The crucible 10 was filled with lithium tantalate powder, and the high frequency induction coil 50 was operated to produce a raw material melt 140. After producing the raw material melt 140, the half position (0.5L) of the high frequency induction coil 50 is the second relative position where the temperature gradient is optimal for crystal growth, that is, the bottom surface 11 of the crucible 10 is set to 0%, The crucible base 20 was moved so that the upper end 41 of the after-heater 40 would be 37% (0.37H) when 100%.

  As a result of repeating the single crystal growth 100 times under the above conditions, the maximum crucible diameter with respect to the minimum crucible diameter was 106%.

(Example 2)
When producing the raw material melt 140, when the bottom surface 11 of the crucible 10 is set to 0% and the upper end 41 of the after heater 40 is set to 100% at a position (0.5 L) of the coil length L of the high-frequency induction coil 50 A single crystal was grown in the same manner as in Example 1 except that the 45% position (0.45H) was arranged.

  As a result of repeating the single crystal growth 100 times under the above conditions, the maximum crucible diameter with respect to the minimum crucible diameter was 108%.

(Example 3)
When producing the raw material melt 140, when the bottom surface 11 of the crucible 10 is set to 0% and the upper end 41 of the after heater 40 is set to 100% at a position (0.5 L) of the coil length L of the high-frequency induction coil 50 A single crystal was grown in the same manner as in Example 1 except that the 55% position (0.55H) was arranged.

  As a result of repeating the single crystal growth 100 times under the above conditions, the maximum crucible diameter with respect to the minimum crucible diameter was 106%.

(Comparative Example 1)
37% position (0.37H) when the bottom surface 11 of the crucible 10 is 0% and the upper end 41 of the after heater 40 is 100% at a position (0.5 L) of the coil length L of the high frequency induction coil 50. The single crystal growth was performed in the same manner as in Example 1 except that the positional relationship between the high-frequency induction coil 50 and the crucible 10 was not changed between the melting of the crystal raw material and the crystal growth.

  As a result of repeating the single crystal growth 100 times under the above conditions, the maximum crucible diameter with respect to the minimum crucible diameter was 114%. Since the amount of deformation was large, repair processing was performed to correct the shape of the crucible 10.

(Comparative Example 2)
As shown in FIG. 4, the bottom surface 11 of the crucible 10 is set to 0% and the upper end 41 of the after heater 40 is set to 100% at a position (0.5 L) of the coil length L of the high-frequency induction coil 50. The same operation as in Example 1 was performed except that the 60% position (0.6H) was arranged.

  Under the above conditions, the raw material at the bottom of the crucible 10 remained unmelted, and crystal growth could not be started.

  Thus, according to this example, it was shown that the method for producing a single crystal according to this embodiment can reduce the thermal load on the crucible 10 and suppress the deformation of the crucible 10.

  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 11 bottom 20 crucible base 21 crucible shaft 22 crucible shaft drive motor 30 reflector 40 after heater 41 upper end 50 high frequency induction coil 60 heat insulating material 70 furnace body 80 pulling shaft 81 seed crystal holding jig 82 pulling shaft driving motor 90 weight measuring unit 100 Thermometer 110 Control unit 120 Seed crystal 130 Single crystal 140 Raw material melt

Claims (5)

A single crystal raw material is put into a crucible in a furnace, and the crucible is heated by a high frequency induction coil for induction heating to heat and melt the single crystal raw material, and then a seed crystal is brought into contact with the raw material melt to produce a single crystal. In the method for producing a single crystal,
Producing a raw material melt with a relative position in the height direction between the center position of the coil length of the high-frequency induction coil and the bottom surface of the crucible as a first relative position;
And a step of growing the single crystal using a relative position in the height direction of the center position of the coil length of the high-frequency induction coil and the bottom surface of the crucible as a second relative position.   The distance between the center position of the coil length of the high-frequency induction coil at the first relative position and the bottom surface of the crucible is the center of the coil length of the high-frequency induction coil at the second relative position. The method for producing a single crystal according to claim 1, wherein the distance is longer than a distance between the position and the bottom surface of the crucible. An after heater is provided above the crucible, and when the distance in the height direction from the bottom surface of the crucible to the upper end of the after heater is 100%,
The first relative position is such that the center position of the coil length of the high-frequency induction coil is such that the distance in the height direction from the bottom surface of the crucible to the upper end of the after heater is 45% or more and 55% or less. The method for producing a single crystal according to claim 1, wherein the position is set so as to be disposed inside.   The method for producing a single crystal according to any one of claims 1 to 3, further comprising a step of moving the crucible up and down between the step of producing the raw material melt and the step of growing the single crystal.   The method for producing a single crystal according to claim 4, further comprising a step of waiting while maintaining the second relative position between the step of moving the crucible up and down and the step of growing the single crystal.

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