JP2013006758A - Apparatus and method for producing single crystal and single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for producing a single crystal and the like where the single crystal excellent in crystallinity and corresponding to different diameters can be easily grown.SOLUTION: A single crystal pulling apparatus 1 comprises: a cylindrical wall 22 standing up from the surrounding of a bottom 21; a disc-like cover 23 set on the top of the wall 22 and having an opening 23a in a center part; a crucible 20 to hold an alumina melt 300; an upper heater 30 to heat the crucible 20 from the wall 22; a lower heater 35 set at the lower part of the crucible 20 and heating the crucible 20 from the bottom 21; a pulling rod 40 to pull a sapphire ingot 200 from the alumina melt 300; an upper heater power source 90 to supply electric power to the upper heater 30; and a lower heater power source 95 to supply electric power to the lower heater 35.

Description

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

Known methods for producing single crystals include the Czochralski method (Czochralski method, Cz method), the heat exchange method (HEM method), the kiloporous method (Kyropoulos method), and the like.
The Cz method is a method of growing a cylindrical single crystal ingot by melting a raw material in a container, bringing a seed crystal into contact with the surface of the melt, and then pulling up the seed crystal while rotating it.
The HEM method is a method in which a raw material is melted in a container, and all the melt in the container is crystallized while cooling a seed crystal set at the bottom of the container.
The kiloporous method is a method in which a seed crystal is brought into contact with a raw material melt, and the crystal is grown from the seed crystal by slowly cooling the melt.

Patent Document 1 discloses a method for growing a sapphire single crystal in which a sapphire raw material powder is charged into a crucible installed in a chamber, heated and melted by a direct heating method using a heater, and the grown crystal is pulled up from the raw material melt. In addition, a heat-resistant crucible containing no iridium is used as the crucible, and when the sapphire raw material powder is heated and melted, the atmosphere gas is replaced with an inert gas in advance, and oxygen substantially exists in the chamber. A method for growing a sapphire single crystal is described in which a sufficient amount of inert gas is maintained to maintain a non-performing state.
In Patent Document 2, aluminum oxide is melted in a container, a seed crystal is brought into contact with the surface of the aluminum oxide melt in the container, and a sapphire single crystal is grown in the aluminum oxide melt. The pulling distance of the seed crystal is set to 0 to less than 20% of the liquid level height of the aluminum oxide melt at the initial growth stage, and after bringing the seed crystal into contact with the aluminum oxide melt, the furnace temperature is set to 0.2 to A method for producing a sapphire single crystal characterized by growing while lowering at 2 ° C./hr is described.
In Patent Document 3, when a lithium triborate single crystal is grown from a melt in a crucible using a <001> -axis seed crystal by a high-temperature solution top seeding method or a chiloporous method, it leads to a seed crystal (001 ) A method for producing a lithium triborate single crystal in which the ratio of the width of the growth ridge formed parallel to the <100> orientation and the <010> orientation on the growth surface is larger than 1: 3 is described.
Patent Document 4 describes a method for producing a sapphire single crystal in which the single crystal sapphire is grown by tilting the growth axis of the sapphire single crystal within a range of 0.1 to 15 degrees from the C axis ([0001] direction). ing. Here, the sapphire single crystal is manufactured by the pulling method or the kilopross method, and the tilting direction may be any of the a-axis direction, the m-axis direction, or the direction in which the a-axis direction and the m-axis direction are combined. Is described.
In Patent Document 5, a crucible for containing a melted raw material, a pull-up shaft provided on the upper surface of the crucible and movable up and down, and provided on a side surface and / or a bottom surface of the crucible for heating the raw material are disclosed. And a reflecting plate provided above the surface of the melted raw material by a distance of ½ or less of the diameter of the crystal to be grown and having an opening through which the crystal can pass. An apparatus for producing oxide single crystals is described.
In Patent Document 6, when growing a high-resolved pressure compound semiconductor single crystal by a liquid capsule pulling method, a ring that covers the crucible inner / outer portion is provided at the upper end of the crucible containing the raw material melt, and an upper surface of the ring is provided. An apparatus for producing a semiconductor single crystal positioned below the upper end of a crucible holding container is described.

JP 2008-7354 A JP 2008-31019 A JP-A-7-315993 JP 2008-56518 A Japanese Patent Laid-Open No. 3-97690 JP 58-41796 A

By the way, in the Cz method, the diameter of the single crystal to be pulled is regulated by the size of the crucible, mainly the inner diameter. For this reason, a crucible corresponding to the diameter of the single crystal to be pulled up was prepared. For this reason, when changing the diameter of the single crystal to be pulled, it is necessary to replace the crucible. Providing a plurality of crucibles of different sizes has a problem of increasing costs and complicating management. On the other hand, when manufacturing single crystals of various diameters with a large crucible, the control is difficult, the fluctuation of the diameter of the single crystal is large, and the quality of the single crystal is deteriorated.
In the Cz method, since the single crystal is formed on the surface of the raw material melt, the temperature gradient in the vicinity of the interface between the single crystal and the raw material melt on the liquid surface of the raw material melt and in the single crystal increases. The single crystal formed by the Cz method has a problem that distortion and crystal defects are likely to occur due to a temperature gradient and it is difficult to obtain a good quality crystal.
An object of the present invention is to provide a single crystal manufacturing apparatus and the like that are excellent in crystallinity and can easily grow single crystals having different diameters.

For this purpose, a single crystal manufacturing apparatus to which the present invention is applied is provided with a bottom portion, a wall portion provided on the bottom portion in contact with the bottom portion, and an opening portion provided in contact with or away from the upper side of the wall portion. And a crucible for holding a melt obtained by melting the raw material by heat by the bottom and the wall, and surrounding the crucible wall from outside, heat is generated by current, and the crucible is radiated by heat. A first heating element that heats from the wall, a second heating element that is provided below the bottom of the crucible, generates heat by current, and heats the crucible from the bottom by radiant heat, and a melt held in the crucible, A shoulder portion in which the area of the cross section perpendicular to the pulling direction gradually increases in the direction opposite to the pulling direction, and a trunk portion extending from the shoulder portion, and a change in the cross sectional area perpendicular to the pulling direction is smaller than that of the shoulder portion A pulling portion for pulling up a single crystal comprising: Current supplies to one of the heating element, and a first power supply for controlling to gradually reduce the power supplied to the first heating element in the formation of the body portion of the single crystal.
In this single crystal manufacturing apparatus, the opening of the lid portion of the crucible may be provided corresponding to the shape of the cross section of the body portion of the single crystal perpendicular to the pulling direction.
Also, the crucible lid portion reflects the radiant heat radiated from the melt surrounding the single crystal body being pulled up toward the melt and keeps the melt above the melting point. It can be characterized by being provided corresponding to the melt surrounding.
Further, the apparatus further includes a second power source that supplies current to the second heating element and controls the power supplied to the second heating element to be gradually reduced in forming the single crystal body. It can be.
Furthermore, the crucible is characterized in that it is made of molybdenum (Mo), tungsten (W), iridium (Ir), platinum (Pt), tantalum (Ta) or an alloy containing at least one of these. it can.
And the difference of the thermal expansion coefficient of the material which comprises the trunk | drum and bottom part of a crucible, and a cover part can be characterized by being 3 * 10 < ^-6 > / K or less.
In addition, the ratio D2 / D1 between the inner diameter D1 of the crucible and the inner diameter D2 of the opening of the lid portion may be 0.5 to 0.9.
Further, the melt may be an alumina melt obtained by melting aluminum oxide, and the single crystal may be a sapphire single crystal.
From another point of view, the single crystal manufacturing method to which the present invention is applied includes a bottom part, a wall part provided on the bottom part in contact with the bottom part, an opening part, and an upper part of the wall part. An electric current is passed through a crucible provided with a lid provided to a first heating element provided so as to surround the crucible wall from the outside and a second heating element provided below the bottom of the crucible. The crucible was heated by radiant heat to melt the raw material held by the bottom and the wall to form a melt, and provided at one end of the lifting rod on the liquid level of the melt held in the crucible The seeding step for bringing the seed crystal into contact and the lower part of the seed crystal so that the section perpendicular to the pulling direction gradually increases from the seed crystal in the plane in which the opening is projected in the pulling direction while pulling the pulling bar vertically upward. A shoulder forming process for forming a single crystal shoulder on the While gradually raising the raising rod vertically, at least the power supplied to the first heating element is gradually reduced and the radiant heat from the melt surrounding the single crystal is reflected by the crucible lid so that the melt exceeds the melting point. A body part forming step of forming a single crystal body part below the shoulder part on the surface of the melt and below the surface of the melt in a plane that is held and projected in the pulling direction; A pulling step of pulling up the pulling bar vertically upward and pulling the formed single crystal through the opening of the lid of the crucible in a state where the melt surrounding the crystal body is above the melting point.
In the shoulder forming step, the lifting rod can be rotated.
And in a trunk | drum formation process, it can be characterized by rotating a raising rod.
Further, the crucible may be rotated in the shoulder forming step.
Furthermore, the crucible may be rotated in the body forming step.
And in a trunk | drum formation process, it can further be characterized by further reducing gradually the electric power supplied to a 2nd heat generating body.
Furthermore, from another viewpoint, the single crystal produced by the single crystal manufacturing method to which the present invention is applied is characterized in that the interference fringes corresponding to the crystal strain observed in the polarization observation method are substantially concentric circles. It can be.
Further, the single crystal may be a hexagonal crystal, and the observation surface of the single crystal in the polarization observation method may be a (0001) plane.
The single crystal may be sapphire.
In addition, the single crystal may be cylindrical and have a diameter of 100 mm or more.

  ADVANTAGE OF THE INVENTION According to this invention, the single crystal manufacturing apparatus etc. which are excellent in crystallinity and can grow a single crystal of a different diameter easily can be provided.

It is a figure for demonstrating an example of a structure of the single crystal manufacturing apparatus with which this Embodiment is applied. It is a figure explaining an example of composition of a crucible in this embodiment. It is a figure explaining an example of composition of a sapphire ingot manufactured using a single crystal manufacturing device. It is a flowchart for demonstrating the method (manufacturing method) which manufactures a sapphire ingot using a single crystal manufacturing apparatus. It is a cross-sectional schematic diagram explaining the growth mechanism of the sapphire ingot in this Embodiment. It is a figure explaining the method of controlling the diameter of a sapphire ingot, without changing the internal diameter of a crucible. It is sectional drawing for demonstrating the crucible and sapphire ingot of an Example. It is a schematic diagram which shows the result by the polarization observation method of an Example sample and a comparative example sample. It is a figure which shows the electric power supplied to the upper heater and the lower heater in the shoulder part formation process and trunk | drum formation process of the sapphire ingot of an Example.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[Single crystal manufacturing equipment 1]
FIG. 1 is a diagram for explaining an example of the configuration of a single crystal manufacturing apparatus 1 to which the present embodiment is applied.
This single crystal manufacturing apparatus 1 has a heating furnace 10 for growing a columnar sapphire ingot 200 made of a sapphire single crystal as an example of a single crystal. The heating furnace 10 has a cylindrical outer shape, and includes a heat insulating container 11 in which a cylindrical space is formed. And the heat insulation container 11 is comprised by assembling the components which consist of carbon heat insulating materials, for example. The heating furnace 10 further includes a chamber 14 that houses the heat insulating container 11 in an internal space. Furthermore, the heating furnace 10 is formed through the side surface of the chamber 14, the gas supply pipe 12 supplying gas from the outside of the chamber 14 through the chamber 14, and the through-hole formed in the side surface of the chamber 14. And a gas discharge pipe 13 for discharging gas to the outside.

Further, a support base 15 having a disk-like outer shape is disposed below the inside of the heat insulating container 11 so that one surface (surface) faces upward. The support 15 is made of, for example, molybdenum (Mo).
Furthermore, the support bar 16 is fixed to the other surface (back surface) of the support base 15 and has one end drawn out of the chamber 14 through a through hole provided in the bottom of each of the heat insulating container 11 and the chamber 14. Is provided. The support bar 16 is attached so as to be rotatable around an axis. Further, a sealing material (not shown) is provided between the support rod 16 and the through hole of the chamber 14.

In addition, a crucible 20 for accommodating an alumina melt 300 as an example of a melt obtained by melting aluminum oxide as a raw material is disposed below the inside of the heat insulating container 11 and on the support base 15. .
The crucible 20 is provided in contact with the bottom portion 21 in contact with the support base 15, a cylindrical wall portion 22 rising from the periphery of the bottom portion 21, and provided on the wall portion 22, and has an opening 23 a at the center. And a disk-shaped lid portion 23 having the same.
The bottom portion 21 and the wall portion 22 are configured as one body and hold the alumina melt 300.
Although the crucible 20 (the bottom portion 21, the wall portion 22, and the lid portion 23) will be described in detail later, in FIG. 1, the lid portion 23 is shown so as to be held in contact with the wall portion 22.

  The crucible 20 (bottom portion 21, wall portion 22, lid portion 23) is supported by a support base 15, and the support base 15 is supported by a support bar 16. The support bar 16 is provided outside the chamber 14 and is supported by a rotation mechanism (not shown) that rotates the support bar 16. Therefore, the crucible 20 and the support base 15 rotate in the direction of arrow C as the support bar 16 rotates. The crucible 20 may be rotated in the direction opposite to the arrow C.

Furthermore, the heating furnace 10 faces the wall portion 22 of the crucible 20 and surrounds (encloses) the wall portion 22 of the crucible 20 between the inside of the side surface of the heat insulating container 11 and the outside of the wall portion 22 of the crucible 20. The upper heater 30 as an example of the provided 1st heat generating body is provided.
The upper heater 30 is made of, for example, carbon (C) such as graphite (graphite) or a material containing carbon (C), generates heat by current (energization), and heats the crucible 20 from the wall portion 22 by radiant heat.
The upper heater 30 may be formed in a spiral shape so that a current flow path surrounds the wall portion 22 of the crucible 20, and is configured to be folded up and down at the upper end portion and the lower end portion of the wall portion 22 of the crucible 20. May be. In addition, in order to supply an electric current to the upper heater 30, although several wiring is provided through the chamber 14 and the heat insulation container 11, description of these wiring is abbreviate | omitted in FIG.

  In FIG. 1, it is shown that the upper end of the upper heater 30 is above the upper surface of the lid portion 23 of the crucible 20, but the upper end of the upper heater 30 and the upper surface of the lid portion 23 coincide with each other. The upper end of the upper heater 30 may be located below the upper surface of the lid portion 23, that is, at the position of the wall portion 22. Similarly, in FIG. 1, the lower end of the upper heater 30 is shown as being below the lower surface of the bottom 21 of the crucible 20, but the lower end of the upper heater 30 and the lower surface of the bottom 21 may coincide with each other. The lower end of the upper heater 30 may be at the position of the wall portion 22 of the crucible 20.

  Furthermore, the heating furnace 10 is an example of a second heating element provided below the bottom portion 21 of the crucible 20 and between the bottom portion 21 and the inner bottom portion of the heat insulating container 11 so as to face the bottom portion 21. The lower heater 35 is provided. It should be noted that the outer shape of the lower heater 35 is a disc shape with the center portion hollowed out when roughly grasped. The support bar 16 is passed through an opening in the center.

  Similarly to the upper heater 30, the lower heater 35 is made of carbon (C) such as graphite or a material containing carbon (C) as an example, generates heat by current (energization), and causes the crucible 20 to be radiated by radiant heat. Heat from the bottom 21. The lower heater 35 may be configured in a spiral shape so that the current flow path surrounds the support rod 16, or may be configured to be alternately folded at the periphery and the center of the bottom 21 of the crucible 20. . In order to supply current to the lower heater 35, a plurality of wirings are provided through the chamber 14 and the heat insulating container 11. However, these wirings are not shown in FIG.

In FIG. 1, the peripheral portion of the lower heater 35 is illustrated as being outside the outer periphery of the bottom portion 21 of the crucible 20, but the peripheral portion of the lower heater 35 and the outer periphery of the bottom portion 21 may coincide with each other. The peripheral part of the lower heater 35 may be inside the outer periphery of the bottom part 21. Similarly, in FIG. 1, the central portion of the lower heater 35 is inside the outer peripheral portion of the support base 15, but the central portion of the lower heater 35 may coincide with the outer peripheral portion of the support base 15. The central portion may be outside the outer peripheral portion of the support base 15.
Each shape of the upper heater 30 and the lower heater 35 may be any shape that allows the crucible 20 to be efficiently heated by the upper heater 30 and the lower heater 35.

  In FIG. 1, the area where the support base 15 is in contact with the bottom 21 of the crucible 20 is made smaller than the area of the bottom 21 of the crucible 20 so that the bottom 21 of the crucible 20 is efficiently heated by the radiant heat from the lower heater 35. It has become.

  Furthermore, the heating furnace 10 includes a pulling rod 40 that extends downward from above through through holes provided in the upper surfaces of the heat insulating container 11 and the chamber 14, respectively. The pulling rod 40 is attached so as to be able to move in the vertical direction (arrow A direction) and rotate around the axis (arrow B direction). A sealing material (not shown) is provided between the through hole provided in the chamber 14 and the lifting rod 40. A holding member 41 for attaching and holding a seed crystal 210 (see FIG. 3 to be described later) as a base for growing the sapphire ingot 200 is attached to an end portion of the pulling bar 40 on the vertically lower side. Yes.

The single crystal manufacturing apparatus 1 also includes a pulling drive unit 50 for pulling up the pulling bar 40 vertically upward and a pulling bar rotation driving unit 60 for rotating the pulling bar 40. Here, the pulling drive unit 50 is configured by a motor or the like, and can adjust the pulling speed of the pulling rod 40. Further, the lifting rod rotation drive unit 60 is also constituted by a motor or the like, and the rotation speed of the lifting rod 40 can be adjusted.
Here, the arrow A direction is referred to as a pulling direction.

  Further, the single crystal manufacturing apparatus 1 includes a gas supply unit 70 that supplies gas into the chamber 14 via the gas supply pipe 12. In the present embodiment, the gas supply unit 70 can supply an inert gas such as argon.

  On the other hand, the single crystal manufacturing apparatus 1 includes a gas discharge unit 80 that discharges gas from the inside of the chamber 14 via the gas discharge pipe 13. The gas discharge unit 80 includes, for example, a vacuum pump or the like, and can reduce the pressure in the chamber 14 or exhaust the gas supplied from the gas supply unit 70.

Furthermore, the single crystal manufacturing apparatus 1 includes an upper heater power source 90 as an example of a first power source that supplies current to the upper heater 30. The upper heater power supply 90 can set the presence / absence of current supply to the upper heater 30 and the power (current and / or voltage) to be supplied.
The single crystal manufacturing apparatus 1 includes a lower heater power source 95 as an example of a second power source that supplies current to the lower heater 35. The lower heater power supply 95 can set the presence / absence of supply of current to the lower heater 35 and the power (current and / or voltage) to be supplied.

The single crystal manufacturing apparatus 1 includes a crucible rotation driving unit 110 that rotates the support rod 16 to rotate the crucible 20 supported by the support base 15. The crucible rotation drive unit 110 is also composed of a motor or the like, and the rotation speed of the crucible 20 can be adjusted.
Furthermore, the single crystal manufacturing apparatus 1 includes a weight detection unit 120 that detects the weight of the sapphire ingot 200 that grows on the lower side of the pulling rod 40 via the pulling rod 40. The weight detection unit 120 includes, for example, a weight sensor.

  The single crystal manufacturing apparatus 1 includes a control unit 100 that controls the above-described pulling drive unit 50, pulling rod rotation driving unit 60, gas supply unit 70, gas discharge unit 80, upper heater power supply 90, and lower heater power supply 95. ing. Further, the control unit 100 calculates the crystal diameter of the sapphire ingot 200 to be pulled up based on the weight signal output from the weight detection unit 120 and feeds back to the upper heater power supply 90 and the lower heater power supply 95.

  In the present embodiment, the lifting rod 40, the lifting drive portion 50, and the lifting rod rotation driving portion 60 constitute a lifting portion.

[Crucible 20]
FIG. 2 is a diagram for explaining an example of the configuration of the crucible 20 in the present embodiment.
As described above, the crucible 20 includes the bottom portion 21, the wall portion 22, and the lid portion 23. At least the bottom portion 21 and the wall portion 22 are integrally formed so that the alumina melt 300 can be held.
In FIG. 1, the lid portion 23 is composed of a member different from the bottom portion 21 and the wall portion 22, and is placed on the wall portion 22 so that the peripheral portion of the lid portion 23 is in contact with the upper end portion of the wall portion 22. Yes. And the cover part 23 is disk shape, Comprising: It has the circular opening part 23a in the center part.
The inner diameter D2 of the opening 23a is set corresponding to the diameter of the sapphire ingot 200 formed as described later.

A plurality of pins 23 b penetrating the lid portion 23 may be provided in the peripheral portion of the lid portion 23 so that the position of the lid portion 23 does not shift with respect to the wall portion 22. The pin 23b prevents the lid 23 from being displaced due to the portion that penetrates the lid 23 coming into contact with the inside of the wall 22.
Further, a hole that accommodates a portion of the pin 23 b that penetrates the lid portion 23 may be provided in the upper end portion of the wall portion 22. In addition, although the screw may be provided on the pin 23b and screwed to the wall portion 22, it is not necessary to screw the pin portion 23b in order to suppress the displacement of the lid portion 23.

In addition, when not replacing | exchanging the cover part 23, you may comprise the cover part 23 integrally with the bottom part 21 and the wall part 22. FIG. Furthermore, when the lid portion 23 is not replaced, the lid portion 23 disposed so as to contact the upper end portion of the wall portion 22 may be fixed to the wall portion 22 by heat or the like.
Furthermore, the lid portion 23 may be arranged at a predetermined distance without contacting the wall portion 22. At this time, a lid holding member (not shown) for holding the lid 23 at a predetermined distance from the wall 22 may be provided.

Moreover, in FIG. 2, the cover part 23 was made into the disk shape which has the circular opening part 23a in the center. However, the shape of the opening 23a is not necessarily circular, as long as it reflects the radiant heat from the alumina melt 300 as described later, and may be a polygon or the like.
The lid portion 23 may be convex upward from the peripheral portion toward the opening 23a (side away from the bottom portion 21), and downward from the peripheral portion toward the central portion (side toward the bottom portion 21). It may be convex.

The crucible 20 (bottom portion 21, wall portion 22, lid portion 23) only needs to be made of a refractory metal having a melting point higher than that of the single crystal raw material. Molybdenum (Mo), tungsten (W), iridium (Ir), platinum (Pt), tantalum (Ta), or an alloy containing at least one of these may be used.
In the crucible 20, the bottom 21 and the wall 22 (configured integrally) and the lid 23 are preferably made of the same material from the viewpoint of reducing stress due to thermal expansion, but may be made of different materials.
Hereinafter, the crucible 20 will be described as being composed of molybdenum (Mo) having a melting point (2617 ° C.) higher than that of aluminum oxide (2054 ° C.).

If a sapphire wafer having a diameter of 100 mm is cut out from the sapphire ingot 200, the sapphire ingot 200 needs to have a diameter D0 (see FIG. 3 described later) of 110 mm.
Taking the case where the sapphire ingot 200 having a diameter D0 of 110 mm is taken as an example, the inner diameter D1 of the wall portion 22 of the crucible 20 (the inner diameter D1 of the crucible 20) is preferably 180 mm, for example. For example, the inner height H1 of the crucible 20 is preferably 200 mm. And the thickness of the bottom part 21 and the wall part 22 is 10 mm, for example.
On the other hand, the inner diameter D2 of the opening 23a of the lid 23 is preferably 125 mm, for example. The thickness of the lid part 23 is 2 mm, for example.
These numerical values are merely examples, and the inner diameter D1 and height H of the crucible 20 and the inner diameter D2 of the lid portion 23 may be set according to the diameter and length of the sapphire ingot 200 to be manufactured.
As will be described later, the inner diameter D2 of the opening 23a of the lid 23 is related to the diameter D0 (see FIG. 3 described later) of the sapphire ingot 200 to be manufactured, and is 1.1 to 1 of the diameter D0 of the sapphire ingot 200. .2 is preferably set.

[Sapphire Ingot 200]
FIG. 3 is a diagram illustrating an example of the configuration of a sapphire ingot 200 manufactured using the single crystal manufacturing apparatus 1.
The sapphire ingot 200 includes a seed crystal 210 that serves as a base for growing the sapphire ingot 200, a shoulder 220 that extends under the seed crystal 210 and is integrated with the seed crystal 210, and a lower portion of the shoulder 220. A trunk portion 230 extending and integrated with the shoulder portion 220 is provided. In the sapphire ingot 200, a single crystal is grown in the c-axis direction of hexagonal sapphire from the upper side, that is, from the seed crystal 210 side, to the lower side, that is, from the trunk portion 230 side. That is, in the sapphire ingot 200, a single crystal of sapphire is grown in the direction of arrow A in FIG.

Here, the shoulder portion 220 has a shape in which the diameter gradually increases from the seed crystal 210 side toward the body portion 230 side. Moreover, the trunk | drum 230 has a shape from which the diameter becomes substantially the same toward the downward direction from upper direction.
The diameter of the body 230 is set to a value slightly larger than the diameter of the desired sapphire single crystal wafer. The body portion 230 has an end portion 240a having a surface perpendicular to the direction of sapphire single crystal growth (the direction of pulling). In addition, when the growth conditions are changed, the trunk portion 230 has an end portion 240b whose central portion is convex with respect to the growth direction of the single crystal of sapphire, and an end portion whose central portion is concave. 240c may be included.

In the present embodiment, the reason why the sapphire ingot 200 having a crystal grown in the c-axis direction is manufactured is as follows.
In general, in a substrate material for a GaN-based optical device, a polarizer holding member for a liquid crystal projector, a substrate for attaching a silicon device, the surface perpendicular to the c-axis ((0001) surface) of the sapphire single crystal is the main surface. In many cases, a wafer cut from an ingot is used. Therefore, from the viewpoint of yield, it is preferable to use a sapphire single crystal ingot grown in the c-axis direction for cutting out the wafer. For this reason, in the present embodiment, the sapphire ingot 200 in which the crystal is grown in the c-axis direction is manufactured in consideration of the convenience in the subsequent process.

[Method for Manufacturing Sapphire Ingot 200]
FIG. 4 is a flowchart for explaining a method (manufacturing method) for manufacturing the sapphire ingot 200 using the single crystal manufacturing apparatus 1.
In manufacturing the sapphire ingot 200, first, a melting step is performed in which solid aluminum oxide filled in the crucible 20 in the chamber 14 is melted (melted) by heating (step 101).
Next, a seeding step is performed in which temperature adjustment is performed in a state where the lower end portion of the seed crystal 210 is in contact with the aluminum oxide melt, that is, the alumina melt 300 (step 102).
Next, the shoulder crystal forming step is performed in which the shoulder crystal 220 is formed below the seed crystal 210 by pulling upward while rotating the seed crystal 210 in contact with the alumina melt 300 (step 103).
Subsequently, a trunk portion forming step is performed in which the trunk portion 230 is formed below the shoulder portion 220 while the shoulder portion 220 is pulled upward while rotating through the seed crystal 210 (step 104).
Subsequently, a pulling process is performed in which the body 230 is rotated upward through the seed crystal 210 and the shoulder 220 while being pulled up and pulled out from the alumina melt 300 (step 105).
And the cooling process which stops and cools the heating of the crucible 20 is performed (step 106), and after the obtained sapphire ingot 200 is cooled, it is taken out of the chamber 14 to complete a series of manufacturing processes.

  The sapphire ingot 200 thus obtained is first cut at the boundary between the shoulder 220 and the trunk 230, and the trunk 230 is cut out. Next, the cut out body portion 230 is further cut along a plane orthogonal to the growth direction of the single crystal of sapphire to form a sapphire single crystal wafer. At this time, since the sapphire ingot 200 of this embodiment is crystal-grown in the c-axis direction, the main surface of the obtained wafer is the c-plane ((0001) plane). The obtained wafer is used for manufacturing GaN-based optical devices and polarizers.

  Then, each process mentioned above is demonstrated concretely. However, here, the description will be made in order from the preparation process executed before the melting process of step 101.

(Preparation process)
In the preparation step, first, a <0001> c-axis seed crystal 210 is prepared. Next, the seed crystal 210 is attached to the holding member 41 of the pulling rod 40 and set at a predetermined position. Subsequently, the lower heater 35 is installed in the chamber 14. Then, the support base 15 is attached to the support rod 16.
Next, the crucible 20 is installed on the support base 15. The crucible 20 is filled with an aluminum oxide raw material, that is, an alumina raw material. In addition, when the cover part 23 of the crucible 20 is comprised separately from the wall part 22, after filling the crucible 20 (bottom part 21 and wall part 22) with an alumina raw material, the cover part 23 is placed on the wall part 22 You may install in.
And the upper heater 30 is installed so that the wall part 22 of the crucible 20 may be surrounded. Thereafter, the heat insulating container 11 is assembled in the chamber 14.
Then, the control unit 100, the pulling drive unit 50, the pulling rod rotation driving unit 60, the gas supply unit 70, the gas discharge unit 80, the upper heater power supply 90, the lower heater power supply 95, the crucible rotation driving unit 110, and the weight detection unit 120. Energize to. As a result, the control unit 100 causes the pulling drive unit 50, the pulling rod rotation driving unit 60, the gas supply unit 70, the gas discharge unit 80, the upper heater power supply 90, the lower heater power supply 95, the crucible rotation driving unit 110, and the weight detection unit 120. It will be in the state to control. All operations described below are performed based on the control of the control unit 100. Therefore, the description “based on the control of the control unit 100” is omitted.

  In a state where the gas supply from the gas supply unit 70 is not performed, the gas discharge unit 80 decompresses the inside of the chamber 14. Thereafter, the gas supply unit 70 supplies a predetermined gas into the chamber 14 to bring the inside of the chamber 14 to normal pressure.

(Melting process)
In the melting step, the gas supply unit 70 supplies a predetermined gas into the chamber 14. Note that the gas supplied in the melting step may be the same as or different from that in the preparation step. At this time, the lifting rod rotation driving unit 60 rotates the lifting rod 40 at the first lifting rod rotation speed (in the direction of arrow B in FIG. 1). And the crucible rotation drive part 110 rotates the support rod 16 (arrow C direction of FIG. 1), and rotates the crucible 20 at the 1st crucible rotational speed.
Here, the rotation direction (arrow B direction) of the pulling bar 40 and the rotation direction (arrow C direction) of the crucible 20 may be opposite to each other as shown in FIG. .

  The upper heater power supply 90 supplies current to the upper heater 30 to cause the upper heater 30 to generate heat and heat the wall portion 22 of the crucible 20. Similarly, the lower heater power source 95 supplies current to the lower heater 35 to cause the lower heater 35 to generate heat and heat the bottom 21 of the crucible 20.

  In this way, the bottom 21 and the wall 22 of the crucible 20 are heated, and the aluminum oxide accommodated in the crucible 20 is heated to exceed its melting point (2054 ° C.). The alumina raw material, that is, aluminum oxide is melted to form an alumina melt 300.

(Seeding process)
In the seeding process, the gas supply unit 70 supplies a predetermined gas into the chamber 14. Note that the gas supplied in the seeding step may be the same as or different from that in the melting step.
Then, the pulling drive unit 50 lowers the pulling rod 40 to a position where the lower end of the seed crystal 210 attached to the holding member 41 comes into contact with the alumina melt 300 in the crucible 20 to stop. In this state, the upper heater power supply 90 adjusts the current supplied to the upper heater 30 based on the weight signal from the weight detection unit 120. Similarly, the lower heater power supply 95 adjusts the current supplied to the lower heater 35. Note that power (current and voltage) may be adjusted instead of current. Below, it describes with an electric current (electric power).

(Shoulder formation process)
In the shoulder forming step, the upper heater power supply 90 adjusts the current (power) supplied to the upper heater 30, and the lower heater power supply 95 adjusts the current (electric power) supplied to the lower heater 35, and then the alumina melt 300. Hold for a while until the temperature stabilizes. Thereafter, the current (electric power) supplied to the upper heater 30 and the electric current (electric power) supplied to the lower heater 35 are adjusted so that the temperature of the alumina melt 300 is slightly lowered, and the lifting rod 40 is rotated at the first lifting rod rotation speed. 1 is pulled up at the first pulling speed while rotating at (in the direction of arrow A in FIG. 1). The crucible rotation drive unit 110 rotates the crucible 20 at the first crucible rotation speed.

Then, the seed crystal 210 is pulled up while being rotated with its lower end immersed in the alumina melt 300, and a shoulder 220 that expands vertically downward is formed at the lower end of the seed crystal 210. It will be done.
Note that the diameter of the shoulder 220 grows to a value slightly smaller than the inner diameter D2 of the opening 23a of the lid 23. For example, when the inner diameter D2 of the opening 23a is 125 mm, the diameter of the shoulder 220 (diameter D0 in FIG. 3) is 110 mm. That is, D0 / D2 = 0.88.

(Body formation process)
In the body forming step, the gas supply unit 70 supplies a predetermined gas into the chamber 14. In addition, the gas supplied in a trunk | drum formation process may be the same as a shoulder part formation process, and may differ.
Further, the upper heater power supply 90 continues to supply current to the upper heater 30, and the lower heater power supply 95 supplies current to the lower heater 35 to heat the alumina melt 300 through the crucible 20. At this time, control is performed such that the current (power) supplied to the upper heater 30 and the current (power) supplied to the lower heater 35 are gradually reduced. The current (electric power) supplied to the lower heater 35 can be made constant.
Further, the pulling drive unit 50 pulls the pulling rod 40 at the second pulling speed. Here, the second pulling speed may be the same speed as the first pulling speed in the shoulder forming step, or may be a different speed.
Furthermore, the lifting rod rotation drive unit 60 rotates the lifting rod 40 at the second lifting rod rotation speed. Here, the second pulling bar rotation speed may be the same speed as the first pulling bar rotation speed in the shoulder forming step, or may be a different speed.
Then, the crucible rotation drive unit 110 rotates the crucible 20 at the second crucible rotation speed. Here, the second crucible rotation speed may be the same speed as the first crucible rotation speed in the shoulder forming step, or may be a different speed.

The shoulder 220 integrated with the seed crystal 210 is pulled up while being rotated while the lower end of the shoulder 220 is immersed in the alumina melt 300. Therefore, the shoulder 220 preferably has a cylindrical body at the lower end. 230 is formed.
Since the electric power supplied to the upper heater 30 and the electric current (electric power) supplied to the lower heater 35 are controlled to be gradually reduced, the trunk portion 230 is not only a portion on the liquid surface of the alumina melt 300, It also grows in the alumina melt 300. Here, the current (power) supplied to the lower heater 35 can be kept constant without being reduced.
The growth of the sapphire ingot 200 in the trunk forming step will be described in detail later.

(Drawing process)
In the drawing process, the gas supply unit 70 supplies a predetermined gas into the chamber 14. In addition, the gas supplied in a drawing process may be the same as that of a trunk | drum formation process, and may differ.
Further, the upper heater power source 90 continues to supply current to the upper heater 30 to heat the alumina melt 300 through the wall portion 22 of the crucible 20. Similarly, the lower heater power source 95 supplies current to the lower heater 35 and heats the alumina melt 300 via the bottom 21 of the crucible 20. Thus, the alumina melt 300 surrounding (surrounding) the formed sapphire ingot 200 is controlled to be in a state higher than the melting point.
When the weight detection unit 120 detects that the weight of the sapphire ingot 200 has reached a predetermined value, the pulling drive unit 50 pulls the pulling rod 40 at the third pulling speed, and the sapphire ingot 200 is melted with alumina. Pull out from 300.
Here, the third pulling speed is higher than the first pulling speed in the shoulder forming process or the second pulling speed in the trunk forming process, and is a speed for pulling out the sapphire ingot 200 from the alumina melt 300.
At this time, the lifting rod rotation driving unit 60 rotates the lifting rod 40 at the third lifting rod rotation speed. Here, the third pulling rod rotation speed may be the same as or different from the first pulling rod rotation speed in the shoulder forming step or the second pulling rod rotation speed in the trunk forming step. May be.
Then, the crucible rotation drive unit 110 rotates the crucible 20 at the third crucible rotation speed. Here, the third crucible rotation speed may be the same speed as the first crucible rotation speed in the shoulder forming process or the second crucible rotation speed in the trunk forming process, or may be a different speed. Applying rotation to the crucible 20 is desirable because the shape (columnar shape) of the sapphire ingot 200 is stable.
Thereby, the sapphire ingot 200 shown in FIG. 3 is obtained.

(Cooling process)
In the cooling process, the gas supply unit 70 supplies a predetermined gas into the chamber 14. Note that the gas supplied in the cooling step may be the same as or different from that in the drawing step.
Further, the upper heater power supply 90 stops supplying current to the upper heater 30. Similarly, the supply of current from the lower heater power supply 95 to the lower heater 35 is stopped, and the heating of the alumina melt 300 via the crucible 20 is stopped.
Further, the pulling drive unit 50 stops the pulling of the pulling rod 40, and the pulling rod rotation driving unit 60 stops the rotation of the pulling rod 40. Then, the crucible rotation drive unit 110 stops the rotation of the crucible 20.

At this time, a small amount of aluminum oxide that did not form the sapphire ingot 200 remains as the alumina melt 300 in the crucible 20. For this reason, the alumina melt 300 in the crucible 20 with the stop of heating is gradually cooled and solidified in the crucible 20 after falling below the melting point of aluminum oxide to become aluminum oxide solid.
Then, the sapphire ingot 200 is taken out from the chamber 14 with the sapphire ingot 200 and the chamber 14 sufficiently cooled.

In addition, as for the rotational speed (1st pulling bar rotational speed, 2nd pulling bar rotational speed, 3rd pulling bar rotational speed) of the raising rod 40 mentioned above, 0-20 rpm is preferable. Although it is not necessary to rotate the lifting rod 40 (0 rpm), in order to make the shape of the trunk portion 230 of the sapphire ingot 200 cylindrical, it is better to rotate it. For this reason, the rotation speed of the lifting rod 40 is more preferably 3 to 10 rpm.
Moreover, as for the rotational speed (1st crucible rotational speed, 2nd crucible rotational speed, 3rd crucible rotational speed) of the crucible 20, 0-3 rpm is preferable. Further, the rotational speed of the crucible 20 (first crucible rotational speed, second crucible rotational speed, third crucible rotational speed) is more preferably 0.3 to 1 rpm. Like the pulling rod 40, the crucible 20 need not be rotated (0 rpm), but in order to make the body 230 of the sapphire ingot 200 cylindrical, it is better to rotate it. Therefore, the rotational speed of the crucible 20 is more preferably 0.1 to 1 rpm.
The lifting speed (first lifting speed, second lifting speed) of the lifting rod 40 is preferably 0.5 to 5 mm / hour.

Here, the growth mechanism of the sapphire ingot 200 in the present embodiment will be described.
FIG. 5 is a schematic cross-sectional view for explaining the growth mechanism of the sapphire ingot 200 in the present embodiment. FIGS. 5A, 5B, and 5C sequentially show the growth of the sapphire ingot 200 in the trunk portion forming step (step 104) shown in FIG.

FIG. 5A shows a state immediately after the shoulder forming process (step 103 in FIG. 4) is completed and the process proceeds to the trunk forming process (step 104), and the upper end of the trunk 230 of the sapphire ingot 200 is fused with alumina. A state in which the liquid surface of the liquid 300 coincides is shown.
An isothermal surface 300a, which is a surface having the same temperature in the alumina melt 300 at this time, is indicated by a one-dot chain line in FIG. 5A (the same applies to FIGS. 5B and 5C). The isothermal surface 300a is generally cylindrical concentric with the cylinder formed by the wall portion 22 of the crucible 20, or a cylindrical shape whose diameter gradually decreases from the upper side to the lower side. It is considered that the temperature decreases as the distance from the wall portion 22 increases (center portion). Further, the interval between the isothermal surfaces 300a is narrow in the vicinity of the surface obtained by projecting the opening 23a of the lid 23 in the vertical direction, and is wide in other portions.

It is considered that the alumina melt 300 has such a temperature distribution because the crucible 20 includes the lid portion 23. That is, the radiant heat radiated from the heated alumina melt 300 is reflected by the back surface (inside the crucible 20) of the lid portion 23 and returns to the alumina melt 300. Thereby, the wall part 22 side of the alumina melt 300 in the range where the upper part is covered with the lid part 23 is maintained at the melting point or higher. On the other hand, the radiant heat radiated from the alumina melt 300 in the range not covered with the lid 23 is hardly reflected and returned, and the alumina melt 300 in the range not covered with the lid 23 is near the melting point or The temperature tends to be below the melting point.
From these facts, in the vicinity of the surface in which the opening 23a of the lid portion 23 is projected in the vertical direction, the interval between the isothermal surfaces 300a is narrow on both sides (the wall 22 side and the center side), and is considered wide in other portions. It is done.

  In such a case, as shown in FIG. 5A, the body 230 of the sapphire ingot 200 continues to grow below the shoulder 220, and the temperature of the crucible 20 having a low temperature also in the alumina melt 300. In the central part, it grows in the direction opposite to the pulling direction (arrow A).

Moreover, since the radiant heat radiated | emitted from the alumina melt 300 is reflected by the cover part 23 of the crucible 20, the alumina melt 300 of the side close | similar to the wall part 22 is hold | maintained more than melting | fusing point, Therefore The diameter cannot be larger than the inner diameter D2 of the opening 23a of the lid 23 (the diameter of the surface in which the opening 23a is projected in the vertical direction with respect to the liquid surface of the alumina melt 300). Further, the diameter D0 of the trunk portion 230 following the shoulder portion 220 may also be larger than the inner diameter D2 of the opening portion 23a (the diameter of the surface in which the opening portion 23a is projected in the vertical direction with respect to the liquid surface of the alumina melt 300). Can not.
In the present embodiment, the diameter D0 of the sapphire ingot 200 is determined by the inner diameter D2 of the opening 23a of the lid portion 23 of the crucible 20. For this reason, it is not necessary to control the diameter D0 of the sapphire ingot 200.
Further, as the growth of the sapphire ingot 200 progresses, the shoulder portion 220 approaches the lid portion 23, thereby narrowing the heat dissipation path between the opening 23 a of the lid portion 23 and the sapphire ingot 200. That is, the space in the crucible 20 (region filled with the gas in the crucible 20) is kept warm. Thereby, the grown sapphire ingot 200 becomes difficult to be cooled, and the temperature gradient in the sapphire ingot 200 becomes small. Strain and crystal defects due to thermal stress are less likely to occur due to a small temperature gradient, and in particular, a large-diameter ingot (crystal) has a great effect of obtaining a crystal with few strains and crystal defects.

In the conventional Cz method, the entire alumina melt 300 has a melting point or higher so that the body 230 of the sapphire ingot 200 is formed on the surface of the alumina melt 300 and is not formed in the alumina melt 300. The temperature is controlled to be maintained. For this reason, the temperature gradient at the interface between the sapphire ingot 200 and the alumina melt 300 on the surface of the alumina melt 300 becomes large. Therefore, a large thermal stress is applied to the sapphire ingot 200, and strain and crystal defects are generated. In particular, when the sapphire ingot 200 has a large diameter, the occurrence of strain and crystal defects becomes significant.
On the other hand, in the present embodiment, the body portion 230 of the sapphire ingot 200 is formed not only on the surface of the alumina melt 300 but also in the alumina melt 300. Therefore, the temperature gradient at the interface between the sapphire ingot 200 and the alumina melt 300 is kept small.

FIG. 5B shows a state in which the growth of the sapphire ingot 200 has further advanced from the state shown in FIG. In addition, since the pulling rod 40 is pulled up at the second pulling speed in the body forming step, the sapphire ingot 200 is further lifted in the pulling direction (arrow A direction) from the state shown in FIG. ing.
As the growth of the sapphire ingot 200 proceeds, the shoulder 220 of the sapphire ingot 200 approaches the opening 23a. Thereby, the heat dissipation path between the opening 23a of the lid 23 and the sapphire ingot 200 is gradually narrowed. As a result, heat radiation from the surface of the alumina melt 300 is reduced, the temperature difference in the vertical direction in the alumina melt 300 is reduced, and the isothermal surface 300a approaches more vertically. Therefore, the sapphire ingot 200 grows in the alumina melt 300 such that the portion grown on the side opposite to the pulling direction (arrow A direction) becomes thicker toward the wall 22 side of the crucible 20.

FIG. 5C shows a state in which the growth of the sapphire ingot 200 has further progressed from the state shown in FIG. 5B and immediately before the growth of the sapphire ingot 200 is completed. Since the shoulder 220 of the sapphire ingot 200 is further closer to the opening 23a, the heat dissipation path is further narrowed. As a result, the isothermal surface 300a in the alumina melt 300 is substantially vertical. 230 further grows toward the wall 22 side of the crucible 20. In addition, since the pulling rod 40 is pulled up at the second pulling speed in the body forming step, the sapphire ingot 200 is further lifted in the pulling direction (arrow A direction) from the state shown in FIG. ing.
The body 230 of the sapphire ingot 200 has a diameter D0 on the surface of the alumina melt 300 and in the alumina melt 300.

  When the weight detection unit 120 detects a predetermined weight or when a predetermined growth time has elapsed, the sapphire ingot 200 is extracted from the alumina melt 300 (the extraction process of step 105 in FIG. 4).

In the conventional single crystal formation by the Cz method, the body 230 of the sapphire ingot 200 is grown while being pulled up from the surface of the alumina melt 300. For this reason, the temperature was controlled so that the entire alumina melt 300 was maintained at the melting point or higher.
On the other hand, in the present embodiment, the temperature of the alumina melt 300 is controlled so that a part of the body 230 is grown in the alumina melt 300.

Note that the alumina melt 300 in the vicinity of the bottom 21 in the crucible 20 is heated by the lower heater 35 and held at the melting point or higher so that the end 240a (see FIG. 3) of the sapphire ingot 200 is the bottom 21 of the crucible 20. To avoid contact.
Thereby, the length of the ingot (for example, the sapphire ingot 200) can be maximized, and the productivity is improved.
That is, in the present embodiment, the diameter D0 of the sapphire ingot 200 is determined by the inner diameter D2 of the opening 23a of the lid portion 23 of the crucible 20, and the length H0 of the sapphire ingot 200 is determined by the inner length H1 of the crucible 200. Determined. Therefore, the control of the diameter D0 and the length H0 of the sapphire ingot 200 is easier than when the lid portion 23 is not provided.

As shown in FIGS. 5A, 5 </ b> B, and 5 </ b> C, the shoulder portion 220 is controlled so as not to come out of the lid portion 23 of the crucible 20 in the trunk portion forming step. Thereby, it is suppressed that the growing sapphire ingot 200 is cooled rapidly.
Further, since the gap between the opening 23a of the lid portion 23 of the crucible 20 and the shoulder portion 220 becomes narrow, the outside air enters the crucible 20 and the alumina melt 300 and the sapphire ingot 200 are cooled. Is suppressed.
Further, most of the body 230 of the sapphire ingot 200 is grown in the alumina melt 300.
For these reasons, the sapphire ingot 200 grown in the single crystal manufacturing apparatus 1 to which the present embodiment is applied has a gentler temperature gradient during formation as compared to the conventional Cz method. As a result, the internal stress of the sapphire ingot 200 is reduced, and the occurrence of distortion is suppressed. Moreover, it is excellent in shape control and can respond to a large-diameter ingot (for example, sapphire ingot 200).

Next, a method for controlling the diameter D0 of the sapphire ingot 200 in the single crystal manufacturing apparatus 1 to which the present exemplary embodiment is applied will be described.
As described above, it has been described that the diameter D0 of the sapphire ingot 200 is determined by the inner diameter D2 of the opening 23a of the lid 23 of the crucible 20. This is because the radiant heat radiated from the alumina melt 300 is reflected by the back surface of the lid portion 23 and returns to the alumina melt 300, so that the alumina melt 300 is held above the melting point.
Therefore, the diameter of the sapphire ingot 200 (diameter D0 in FIG. 3) can be changed by changing the inner diameter of the opening 23a of the lid 23 of the crucible 20 (inner diameter D2 in FIG. 2).

FIG. 6 is a diagram for explaining a method for controlling the diameter D0 of the sapphire ingot 200 without changing the inner diameter D1 of the crucible 20. 6A shows the case where the opening 23a of the lid 23 has an inner diameter D2a, FIG. 6B shows the inner diameter D2b, and FIG. 6C shows the inner diameter D2c. Here, D2a>D2b> D2c.
By doing so, a sapphire ingot 200 having a diameter D0a in FIG. 6A, a diameter D0b in FIG. 6B, and a diameter D0c in FIG. 6C grows. Here, D0a>D0b> D0c.
That is, in the single crystal manufacturing apparatus 1 to which the present embodiment is applied, by replacing the lid 23 having a different diameter (inner diameter D2 in FIG. 2) of the opening 23a without changing the inner diameter D1 of the crucible 20, Sapphire ingots 200 having different diameters (diameter D0 in FIG. 3) can be grown. Thereby, it is not necessary to prepare a plurality of crucibles 20 having different inner diameters D1.
The range of the ratio D2 / D1 between the inner diameter D1 of the crucible 20 and the inner diameter D2 of the opening 23a is preferably 0.5 to 0.9, and more preferably 0.6 to 0.8. If the ratio is less than 0.5, the obtained ingot (eg, sapphire ingot 200) is smaller than the melt (eg, alumina melt 300), resulting in lower productivity and higher cost. When the ratio is larger than 0.9, the effect of the lid portion 23 is small, and the wall portion 22 of the crucible 20 and the outer periphery of the ingot growing in the melt are close to each other. Crystal strain increases.

Moreover, in this Embodiment, the cover part 23 of the crucible 20 should just reflect the radiant heat radiated | emitted from the alumina melt 300, return to the alumina melt 300, and the alumina melt 300 should just hold | maintain more than melting | fusing point. Therefore, as described above, the lid portion 23 of the crucible 20 does not necessarily have to be provided in contact with the wall portion 22 of the crucible 20, and may be disposed apart from the wall portion 22.
Furthermore, as described above, the lid portion 23 of the crucible 20 has a disk shape having a circular opening 23a at the center, but the opening 23a does not have to be circular, and may be a polygon or the like. Further, the lid portion 23 may be convex upward from the peripheral portion toward the opening 23a (side away from the bottom portion 21), and downward from the peripheral portion toward the central portion (side toward the bottom portion 21). It may be convex. When the lid portion 23 is convex upward, the radiant heat is reflected to the sapphire ingot 200 together with the alumina melt 300, so the diameter D0 of the sapphire ingot 200 becomes smaller. On the contrary, if the cover part 23 is convex downward, the reflection of the radiant heat to the alumina melt 300 close to the sapphire ingot 200 is reduced, and the diameter D0 of the sapphire ingot 200 is further increased.
When the material of the lid part 23 is the same material as the bottom part 21 and the wall part 22 (configured integrally) of the crucible 20, the space between the melt (for example, alumina melt 300) and the lid part 23 is used. This is desirable because the thermal environment can be made uniform. Moreover, when it comprises the material with a near thermal expansion coefficient, the mechanical stress at the time of a heating and cooling becomes small, and the deformation | transformation and damage of the cover part 23, the bottom part 21 of the crucible 20, and the wall part 22 can be prevented. In particular, when growing an ingot (for example, sapphire ingot 200) at a high temperature of 2000 ° C. or higher, the difference in thermal expansion coefficient between the lid portion 23 and the bottom portion 21 of the crucible 20 and the wall portion 22 is 3 × 10 ⁻⁶ / K or less. More preferably, a combination of 2 × 10 ⁻⁶ / K or less (for example, molybdenum and tungsten) is desirable.

Hereinafter, the present invention will be specifically described based on examples. However, the present invention is not limited to the examples.
(Example)
FIG. 7 is a cross-sectional view for explaining the crucible 20 and the sapphire ingot 200 of the embodiment. FIG. 7A shows the state of the seeding process (step 102 in FIG. 4), and FIG. 7B shows the state after the trunk forming process (step 104 in FIG. 4). In FIG. 7, (
The numbers in parentheses) are dimensions in mm in the crucible 20 of the example.
As shown in FIG. 7A, the crucible 20 was made of molybdenum, the inner diameter D1 was 180 mm, and the internal height H1 was 200 mm. The lid 23 of the crucible 20 has an inner diameter D2 of the opening 23a of 125 mm.
The crucible 20 was filled with 13000 g of alumina raw material.

The rotational speed of the lifting rod 40 (= first lifting rod rotational speed = second lifting rod rotational speed = third lifting rod rotational speed) was 5 rpm. The rotational speed of the crucible 20 (= first crucible rotational speed = second crucible rotational speed = third crucible rotational speed) was 0.5 rpm. That is, the rotation speed of the pulling rod 40 and the rotation speed of the crucible 20 were the same in the melting process, the seeding process, the shoulder forming process, the trunk forming process, and the drawing process (see FIG. 4).
The direction of rotation of the pulling bar 40 (arrow B in FIG. 1) and the direction of rotation of the crucible 20 (arrow C in FIG. 1) were opposite.
The lifting speed of the lifting rod 40 (= first lifting speed = second lifting speed) was 2 mm / hour. That is, the pulling speed was the same in the shoulder forming process and the trunk forming process.
Then, after the seeding step, the lifting rod 40 was lifted by 30 mm to form a sapphire ingot 200 in the c-axis direction.

  As shown in FIG. 7B, the grown sapphire ingot 200 had a trunk portion 230 with a diameter D0 of 110 mm and a trunk portion 230 with a length H0 of 168 mm. The 52 mm portion above the body 230 was exposed above the surface of the alumina melt 300, and the lower 116 mm portion was below the surface of the alumina melt 300. At this time, the shoulder 220 was 20 mm in length.

  As described above, in the embodiment, 2/3 of the length H1 of the body 230 of the sapphire ingot 200 is grown in the alumina melt 300. The diameter D0 (110 mm) of the sapphire ingot 200 is slightly smaller than the inner diameter D2 (125 mm) of the opening 23a of the lid 23 due to the effect that the alumina melt 300 is held above the melting point by the lid 23. It was. That is, the ratio between the inner diameter D2 of the opening 23a of the lid 23 and the diameter D0 of the trunk 230 of the sapphire ingot 200 was 1.14. This ratio is in the range of 1.1 to 1.2.

FIG. 9 is a diagram illustrating electric power supplied to the upper heater 30 and the lower heater 35 in the shoulder forming process and the trunk forming process of the sapphire ingot 200 of the example. In FIG. 9, the horizontal axis indicates the elapsed time (minutes) in the shoulder forming step and the trunk forming step, and the vertical axis indicates the power (kW) supplied to each of the upper heater 30 and the lower heater 35.
The electric power supplied to the upper heater 30 gradually decreases from 36 kW at the start of the shoulder 220 formation (elapsed time 0 minutes) to 33.1 kW at the end of formation of the body 230 (elapsed time 1600 minutes). I am letting. The power supplied to the lower heater 35 is slightly from 15.5 kW at the start of the shoulder 220 formation (elapsed time 0 minutes) to 14.7 kW at the end of formation of the body 230 (elapsed time 1600 minutes). It is decreasing.
That is, the power supplied to the upper heater 30 is reduced more than the power supplied to the lower heater 35. By doing so, the sapphire ingot 200 is grown in the alumina melt 300 while keeping the temperature gradient in the alumina melt 300 gentle.

(Comparative example)
A sapphire ingot 200 of a comparative example was grown by a conventional Cz method using the crucible 20 having no lid 23. In the sapphire ingot 200 of the comparative example, the body portion 230 was grown above the liquid surface of the alumina melt 300. Similar to the sapphire ingot 200 of the example, the sapphire ingot 200 of the comparative example was grown in the c-axis direction.

(Contrast between Example and Comparative Example)
From the grown sapphire ingot 200 of the example, an example sample was prepared by cutting a ring on a surface perpendicular to the pulling direction (arrow A direction) and polishing both sides. Both surfaces (observation surfaces in the polarization observation method described later) of the example samples are C surfaces ((0001) surfaces).
In the same manner as in the example, a comparative sample was made from the sapphire ingot 200 of the comparative example by cutting the ring on a surface perpendicular to the pulling direction (arrow A direction) and polishing both surfaces. Both surfaces (observation surfaces in the polarization observation method described later) of the comparative sample are C surfaces ((0001) surfaces).
FIG. 8 is a schematic diagram showing the results of the polarization observation method of the example sample and the comparative example sample. FIG. 8A shows an example sample, and FIG. 8B shows a comparative example sample.
The polarization observation method is a method in which polarized light is transmitted from one surface and light emitted from the other surface is observed in each of the example sample and the comparative sample.

In the example sample shown in FIG. 8A, a stripe pattern (interference fringe) due to concentric interference based on the uniform crystal quality is observed. Furthermore, a discontinuous pattern showing crystal distortion is not observed. Subgrain boundaries and grain boundaries were not observed throughout the crystal.
On the other hand, in the comparative example sample shown in FIG. 8B, in addition to the irregular stripe pattern (interference fringe) due to the nonuniformity of the crystal quality, discontinuity due to crystal distortion, sub-boundary, and grain boundary. A pattern is scattered in portions indicated by α, β, γ, and δ on the outer peripheral portion of the comparative example sample. This is presumably because the sapphire ingot 200 of the comparative example has a large temperature gradient during growth, and the crystal is distorted.

Furthermore, the single crystal manufacturing apparatus 1 to which this Embodiment is applied is demonstrated.
In the single crystal manufacturing apparatus 1 to which the present exemplary embodiment is applied, since the crucible 20 includes the lid portion 23, the melting step (step 101 in FIG. 4) for melting the alumina raw material and / or the alumina melt 300 is cooled. In the cooling step (step 106), even if a part of the alumina melt 300 bounces, the bounced alumina melt 300 is blocked by the lid portion 23 and is prevented from jumping out of the crucible 20. Therefore, damage to the upper heater 30, the lower heater 35, and the heat insulating material constituting the heat insulating container 11 is suppressed.
On the other hand, if the crucible 20 is not provided with the lid 23, in the melting step (step 101 in FIG. 4) for melting the alumina raw material and / or the cooling step (step 106) for cooling the alumina melt 300, the alumina melt 300 is obtained. It is possible that a part of the spring jumps and jumps out of the crucible 20. The high-temperature alumina melt 300 that protrudes adheres to the upper heater 30, the lower heater 35, and further the heat insulating material constituting the heat insulating container 11, or a part of these members is melted and damaged. Will give.

In the single crystal manufacturing apparatus 1 to which the present exemplary embodiment is applied, the sapphire ingot 200 having a crystal grown in the c-axis direction is manufactured as an example. However, for example, the sapphire ingot 200 having a crystal grown in the a-axis direction may be manufactured. Is possible. In addition to sapphire, various oxide single crystals such as lithium triborate (LiB ₃ O ₅ ), cesium borate compounds (CsB ₃ O _5, etc.), potassium niobate (KNbO ₃ ), etc. can also be produced. Furthermore, it is also possible to produce single crystals other than oxides.

DESCRIPTION OF SYMBOLS 1 ... Single crystal manufacturing apparatus, 10 ... Heating furnace, 11 ... Heat insulation container, 12 ... Gas supply pipe, 13 ... Gas discharge pipe, 14 ... Chamber, 15 ... Support stand, 16 ... Support rod, 20 ... Crucible, 21 ... Bottom , 22 ... wall part, 23 ... lid part, 24 ... opening part, 30 ... upper heater, 35 ... lower heater, 40 ... lifting rod, 50 ... lifting drive part, 60 ... lifting rod rotation drive part, 70 ... gas supply part , 80 ... Gas discharge part, 90 ... Upper heater power supply, 95 ... Lower heater power supply, 100 ... Control part, 110 ... Crucible rotation drive part, 120 ... Weight detection part, 200 ... Sapphire ingot, 210 ... Seed crystal, 220 ... Shoulder Part, 230 ... trunk part, 300 ... alumina melt

Claims (18)

A bottom part, a wall part provided on the bottom part in contact with the bottom part, and a lid part having an opening and provided in contact with or apart from the upper side of the wall part, the bottom part and the wall part, A crucible holding a melt obtained by melting the raw material by heat,
A first heating element which is provided so as to surround the wall portion of the crucible from outside, generates heat by current, and heats the crucible from the wall portion by radiant heat;
A second heating element that is provided below the bottom of the crucible, generates heat by current, and heats the crucible from the bottom by radiant heat;
From the melt held in the crucible, a shoulder whose cross-sectional area perpendicular to the pulling direction gradually increases in a direction opposite to the pulling direction, and extends from the shoulder, and is perpendicular to the pulling direction. A pulling portion for pulling up a single crystal having a trunk portion whose cross-sectional area is smaller than that of the shoulder, and
A single power source for supplying current to the first heating element and controlling the power supplied to the first heating element to be gradually reduced in forming the body portion of the single crystal. Crystal manufacturing equipment.   2. The single crystal manufacturing apparatus according to claim 1, wherein the opening of the lid portion of the crucible is provided corresponding to a cross-sectional shape of the body portion of the single crystal perpendicular to the pulling direction. .   The lid portion of the crucible reflects radiant heat radiated from the melt surrounding the body portion of the single crystal being pulled up toward the melt, so that the melt is maintained at a melting point or higher. The single crystal manufacturing apparatus according to claim 1, wherein the single crystal manufacturing apparatus is provided corresponding to the melt surrounding the body portion of the single crystal.   A second power source for supplying a current to the second heating element and controlling to gradually reduce the power supplied to the second heating element in the formation of the body portion of the single crystal; The single crystal manufacturing apparatus according to any one of claims 1 to 3.   The crucible is made of molybdenum (Mo), tungsten (W), iridium (Ir), platinum (Pt), tantalum (Ta) or an alloy containing at least one of these. 5. The single crystal production apparatus according to claim 4. The difference between the thermal expansion coefficients of the materials constituting the body part, the bottom part, and the lid part of the crucible is 3 × 10 ⁻⁶ / K or less, respectively. The single crystal manufacturing apparatus according to claim 1.   The ratio D2 / D1 between the inner diameter D1 of the crucible and the inner diameter D2 of the opening of the lid portion of the crucible is 0.5 to 0.9, according to any one of claims 1 to 6. The single crystal manufacturing apparatus described.   The single crystal manufacturing apparatus according to any one of claims 1 to 7, wherein the melt is an alumina melt obtained by melting aluminum oxide, and the single crystal is a sapphire single crystal. A crucible having a bottom part, a wall part provided on the bottom part in contact with the bottom part, and a lid part provided with an opening and in contact with or away from the upper side of the wall part, the crucible of the crucible The crucible is heated by radiant heat by passing a current through a first heating element provided so as to surround the wall from the outside and a second heating element provided below the bottom of the crucible, and the bottom and A melting step of melting the raw material held by the wall portion into a melt;
A seeding step of bringing a seed crystal provided at one end of a pull-up rod into contact with the liquid level of the melt held in the crucible;
While pulling up the pulling bar vertically upward, a shoulder of a single crystal below the seed crystal so that a section perpendicular to the pulling direction gradually increases from the seed crystal in a plane projected in the pulling direction of the opening. Shoulder forming step to form a part;
While pulling up the pulling bar vertically upward, gradually reduce at least the power supplied to the first heating element, and reflect the radiant heat from the melt surrounding the single crystal by the lid of the crucible. The single crystal is held below the shoulder portion on the liquid surface of the melt and below the liquid surface of the melt in a plane in which the melt is held above the melting point and the opening is projected in the pulling direction. A trunk forming step for forming the trunk,
In the state where the melt surrounding the body portion of the single crystal is above the melting point, the pulling rod is pulled up vertically, and the single crystal formed is pulled through the opening of the lid portion of the crucible. A single crystal manufacturing method including a process.   The single crystal manufacturing method according to claim 9, wherein the pulling rod is rotated in the shoulder forming step.   The method for producing a single crystal according to claim 9 or 10, wherein the pulling rod is rotated in the body forming step.   The single crystal manufacturing method according to claim 9, wherein the crucible is rotated in the shoulder forming step.   The single crystal manufacturing method according to claim 9, wherein the crucible is rotated in the body forming step.   14. The method for producing a single crystal according to claim 9, further comprising gradually reducing electric power supplied to the second heating element in the body forming step.   A single crystal produced by the method for producing a single crystal according to any one of claims 9 to 14, wherein the interference fringes corresponding to the crystal strain observed in the polarization observation method are substantially concentric circles. .   The single crystal according to claim 15, wherein the single crystal is a hexagonal crystal, and an observation plane of the single crystal in the polarization observation method is a (0001) plane.   The single crystal according to claim 15 or 16, wherein the single crystal is sapphire.   The single crystal according to any one of claims 15 to 17, wherein the single crystal is cylindrical and has a diameter of 100 mm or more.

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