JP2010150052A - Apparatus for growing sapphire single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for growing a sapphire single crystal, wherein bubbles are hardly incorporated into a sapphire single crystal being grown. <P>SOLUTION: The apparatus for growing a sapphire single crystal includes: a crucible 1 in which a sapphire raw material is filled; a carbon heater 30 having a cylindrical heater part 3 and a disk-like heater part 4 for heating the crucible; a heat insulating space chamber 6 for keeping the crucible warm; insulating cylinders 8 provided at the bottom face part 60 of the heat insulating space chamber 6; and heater electrodes 5 each inserted into the insulating cylinder 8 and connected to each carbon heater so as to supply an electric power, and is constituted so that the sapphire single crystal is produced from a sapphire raw material melt 10 by a rotary pulling method, wherein the thickness of a heat insulating material for constituting the bottom face part 60 of the heat insulating space chamber 6 is set to be ≥90 mm and the distance from the surface of the bottom face part 60 of the heat insulating space chamber 6 to the lower end of the disk-like heater part 4 is set to be ≥10 mm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sapphire single crystal growing apparatus for producing a sapphire single crystal from a sapphire raw material melt by a rotational pulling method, and more particularly to an improvement of a sapphire single crystal growing apparatus in which bubbles are not easily contained inside the grown sapphire single crystal. Is.

  There is a sapphire substrate as a substrate used for obtaining an optical material, and this substrate is often used as a base for growing a light emitting layer of a light emitting diode. The main method for producing a sapphire single crystal to obtain a sapphire substrate is to grow a single crystal by melting a sapphire raw material in a crucible and bringing the seed crystal into contact with the raw material melt surface and gradually pulling it up. The Czochralski method (Cz method), the Cairo porous method (Kyropulous method), and the like are known. The grown sapphire single crystal is processed into a substrate shape, and the surface is polished to produce a sapphire substrate.

  In order to manufacture a sapphire single crystal from the sapphire raw material melt by a rotational pulling method, a sapphire single crystal growing apparatus as shown in FIG. 2 is used.

  That is, this sapphire single crystal growing apparatus includes a crucible 1 filled with a sapphire raw material, a cylindrical heater portion 3 for heating the outer peripheral surface of the crucible 1 and a discoid heater for heating the bottom surface of the crucible 1 as shown in FIG. A heater 30 made of carbon having a portion 4, a heat insulating space 6 made of a heat insulating material made of carbon and containing at least the crucible 1 and the carbon heater 30 to keep the crucible 1 warm, and a bottom surface of the heat insulating space 6 An insulating cylinder 8 made of aluminum oxide inserted into an opening provided in the section 60, and inserted into the insulating cylinder 8 and the tip side thereof is connected to the cylindrical heater section 3 of the carbon heater 30 to supply electric power. The cylindrical heater electrode 5 made of carbon and the insulating cylinder 8 fitted in the opening provided in the bottom surface portion 60 of the heat insulating space 6 are inserted into the insulating cylinder 8 and the tip side is inserted into the carbon heater. The cylindrical heater electrode 5 made of carbon that is connected to the 30 disk-shaped heater portions 4 and supplies power, and is provided so as to pass through the opening of the bottom surface portion 60 and the opening of the disk-shaped heater portion 4. A support shaft 2 that supports the crucible 1 and a pulling shaft 9 that is inserted into an opening provided in the upper surface portion 61 of the heat insulation space chamber 6 and to which a seed crystal 11 is attached at the tip, the heat insulation space chamber 6 being a furnace body. 7, and a sapphire single crystal 12 is grown from the raw material melt 10 in the crucible 1 by a rotary pulling method.

  However, when a sapphire single crystal is grown using the sapphire single crystal growth apparatus shown in FIG. 2, the resulting crystal is colorless and transparent, but there are often those containing a lump of bubbles inside the crystal. When a substrate is manufactured from such a crystal, there is a possibility that bubbles are included in the substrate or on the substrate surface. Since the light emitting layer of the light emitting diode is grown on the sapphire substrate as described above, it is desirable that the surface of the sapphire substrate has as few defects as possible.

  By the way, the cause of the bubbles is the uptake of gas components present in the raw material melt at the crystal growth interface. And since the gas component existing on the growth interface is not taken into the single crystal, the present inventor has confirmed that the gas component can be prevented from being taken into the crystal by strengthening the convection in the melt in the past. This is empirically obtained as knowledge. As this method, Patent Document 1 discloses a method of enhancing the convection of the melt by performing crystal growth in a low oxygen concentration atmosphere.

And when crystal growth is performed by the method described in Patent Document 1, as a result of enhancing the convection, the bubbles taken into the crystal are surely reduced, but the characteristics of growing the sapphire single crystal by the pulling method Another problem is that the crystal growth of the convex portion below the crucible is promoted. And when the said convex-shaped part adheres to a crucible bottom part, since a big force will be applied to a sapphire seed crystal, there existed a problem which it will fracture | rupture finally and a crystal will fall in a crucible and it will become difficult to continue crystal growth.
JP 09-278592 A

Therefore, the present inventor considered a new method for reducing the gas component existing in the raw material melt on the premise that the bubbles in the crystal are gas components existing in the raw material melt. When the constituent components of the bubbles taken in were investigated, most of them were found to be carbon monoxide gas. And this inventor estimated as follows about the mechanism in which carbon monoxide gas is taken in in raw material melt.
(1) The aluminum oxide raw material melt decomposes at high temperature and low oxygen partial pressure.

Al ₂ O ₃ (m) → Al ₂ O (g) + O ₂ (g)
(2) Carbon scattered in the furnace comes into contact with decomposed alumina in the raw material melt, and reacts with the alumina to generate carbon monoxide gas.

Al ₂ O (g) + C (s) → CO (g) + 2Al (g)
(3) The carbon monoxide gas is carried to the vicinity of the crystal growth interface by the convection of the melt, and is taken into the crystal at the time of crystallization.

  According to the mechanism described above, it is considered that suppressing the contact between the carbon scattered in the furnace and the raw material melt leads to a reduction in the incorporation of bubbles into the crystal.

  Here, as a carbon scattering source, a carbon heater itself, a carbon heater electrode exposed to a high temperature, a carbon heat insulating material surrounding the crucible, or the like can be considered.

  And when the external appearance of each member after crystal growth was observed, it was confirmed that carbon was scattered as fine powder from the carbon heater electrode and was clearly thin. This is because the power input to the carbon heater is large, so the amount of heat transferred from the heater to the carbon heater electrode is large, so the temperature of the carbon heater electrode reaches a high temperature, and the carbon heater electrode and this heater electrode are inserted. This is probably because a discharge phenomenon occurred between the aluminum oxide insulating cylinder. The above discharge phenomenon can be suppressed by lowering the input power to the carbon heater. However, if the growth is carried out below the power suitable for crystal growth, rapid growth of the crystal or crystal There has been a problem in that a phenomenon such as sticking between the crucible and the bottom of the crucible occurs.

  In view of this, the inventor has intensively studied a method for reducing the input power to the carbon heater without impairing the heat retaining property around the crucible, and as a result, escaped heat from the carbon heater through the carbon heater electrode. By increasing the thickness of the bottom surface in the heat-insulated space chamber, which is expected to be large, it is possible to reduce the input power to the carbon heater required for crystal growth and to generate carbon fine powder. It came to discover that it can suppress.

  The present invention has been completed through such technical studies, and the problem is that the above-mentioned problems are solved, the growth yield is high, and no bubbles are contained in the grown sapphire single crystal. The object is to provide a sapphire single crystal growth apparatus.

That is, the invention according to claim 1
A crucible filled with a sapphire raw material, a carbon heater having a cylindrical heater portion for heating the outer peripheral surface of the crucible and a disk-like heater portion for heating the bottom surface of the crucible, and a crucible and a carbon heater composed of a heat insulating material made of carbon A heat-insulating space chamber in which the crucible is kept warm, an insulating cylinder fitted into an opening provided in the bottom surface of the heat-insulating space chamber, and a distal end side connected to the carbon heater inserted into the insulating cylinder In a sapphire single crystal growing apparatus for producing a sapphire single crystal from a melt of the sapphire raw material by a rotational pulling method,
The thickness of the heat insulating material constituting the bottom surface portion of the heat insulation space chamber is set to 90 mm or more, and the distance from the surface of the bottom surface portion of the heat insulation space chamber to the lower end of the disk-shaped heater portion is set to 10 mm or more. Is.

According to the sapphire single crystal growing apparatus of the present invention according to claim 1,
Since the thickness of the heat insulating material constituting the bottom surface portion in the heat insulating space chamber in which the crucible and the carbon heater are accommodated is set to be 90 mm or more, the heat insulating property in the bottom surface portion is improved, and the carbon heater is changed to carbon. The amount of heat released to the outside of the heat insulating space through the heater electrode can be reduced, and the input power to the carbon heater can be reduced accordingly.

  And, by reducing the input power, the above-described discharge phenomenon between the carbon heater electrode and the insulating cylinder into which the heater electrode is inserted can be suppressed, and further, the distance from the bottom surface of the heat insulating space chamber to the lower end of the disk-shaped heater is reduced. Since it is set to 10 mm or more, the discharge phenomenon between the bottom surface portion and the disk-shaped heater portion can also be suppressed, so that carbon monoxide can be prevented from being taken into the raw material melt due to carbon scattering during crystal growth. This makes it possible to obtain a high-quality sapphire single crystal that does not contain bubbles.

  Therefore, the yield of the product can be improved and a great economic effect can be obtained, and the damage to the heater electrode and the insulating cylinder can be reduced by suppressing the discharge phenomenon, so that the manufacturing cost of the sapphire single crystal is greatly improved. It becomes possible to do.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, the sapphire single crystal growing apparatus according to the present invention heats a crucible 1 filled with a sapphire raw material, a cylindrical heater portion 3 for heating the outer peripheral surface of the crucible 1 and the bottom surface of the crucible 1 as shown in FIG. A carbon heater 30 having a disk-shaped heater portion 4, a heat insulating space chamber 6 made of carbon heat insulating material and containing at least the crucible 1 and the carbon heater 30 to keep the crucible 1 warm; and a heat insulating space chamber An insulating cylinder 8 made of aluminum oxide that is fitted into an opening provided in the bottom surface portion 6 of the battery 6, and a distal end side of the insulating cylinder 8 that is inserted into the insulating cylinder 8 and connected to the cylindrical heater portion 3 of the carbon heater 30 is connected to the electric power. The cylindrical heater electrode 5 made of carbon and the insulating cylinder 8 inserted in the opening provided in the bottom surface portion 60 of the heat insulating space 6 are inserted into the insulating cylinder 8 and the tip side is made of carbon. The cylindrical heater electrode 5 made of carbon that is connected to the disk-shaped heater portion 4 of the heater 30 and supplies power, and is also provided so as to penetrate the opening of the bottom surface portion 60 and the opening of the disk-shaped heater portion 4. A support shaft 2 that supports the crucible 1 and a pulling shaft 9 that is inserted into an opening provided in the upper surface portion 61 of the heat insulation space chamber 6 and to which a seed crystal 11 is attached at the tip. Along with the inner surface of the furnace body 7, a sapphire single crystal 12 is grown from the raw material melt 10 in the crucible 1 by a rotary pulling method.

  Note that the sapphire single crystal growing apparatus according to the present invention is not limited to the structure shown in FIG. For example, in the sapphire single crystal growing apparatus of FIG. 1, the carbon heater 30 includes a cylindrical heater unit 3 that heats the outer peripheral surface of the crucible 1 and a disc-shaped heater unit 4 that heats the bottom surface of the crucible 1. Although the heater is configured, the carbon heater 30 may be configured by a single carbon heater having a substantially L-shaped cross section or a cup type in place of the disk-shaped heater portion 4 that heats the bottom surface of the crucible 1.

  In the sapphire single crystal growing apparatus according to the present invention shown in FIG. 1, the minimum value of the thickness X of the carbon heat insulating material constituting the bottom surface portion 60 of the heat insulating space 6 is 90 mm in the sapphire single crystal growing preparation stage. (In the conventional sapphire single crystal growing apparatus shown in FIG. 2, the thickness of the heat insulating material is 80 mm, and the thickness of the heat insulating material can be added in units of 10 mm), and the thickness X of the heat insulating material made of carbon The maximum value is appropriately adjusted to a value within a range where the distance from the surface of the bottom surface portion 60 to the lower end of the disk-shaped heater portion 4 is at least 10 mm. If the thickness X of the heat insulating material made of carbon is set larger than necessary, and the distance from the surface of the bottom surface portion 60 to the lower end of the disk-shaped heater portion 4 becomes less than 10 mm, the heat insulating material made of carbon is used. Since there is a risk that a discharge phenomenon occurs between the bottom surface portion 60 and the disc-like heater portion 4, the device cannot be used due to device restrictions.

  In the sapphire single crystal growing apparatus according to the present invention, the thickness of the heat insulating material constituting the bottom surface portion 60 in the heat insulating space chamber 6 in which the crucible 1 and the carbon heater 30 are accommodated is set to be as thick as 90 mm or more. The heat insulating property in the bottom surface portion 60 is improved, and the amount of heat released from the carbon heater 30 to the outside of the heat insulating space 6 through the carbon heater electrode 5 can be reduced. Input power can be reduced.

  Further, by reducing the input power, the discharge phenomenon between the carbon heater electrode 5 and the insulating cylinder 8 into which the heater electrode is inserted can be suppressed, and further, from the surface of the bottom surface portion 60 of the heat insulating space 6 to the lower end of the disk-shaped heater portion 4. Is set to 10 mm or more, so that the discharge phenomenon between the bottom surface portion 60 and the disc-like heater portion 4 is also suppressed, so that the oxidation into the raw material melt caused by the scattering of carbon during crystal growth Incorporation of carbon is prevented, which makes it possible to obtain a high-quality sapphire single crystal that does not contain bubbles.

  Examples of the present invention will be described in detail below with reference to comparative examples, but the present invention is not limited to these examples. Further, among the obtained substrates, those containing 10% or less of bubbles are regarded as acceptable.

[Example 1]
In the sapphire single crystal growing apparatus of FIG. 1 in which the carbon heater 30 having the cylindrical heater portion 3 and the disc heater portion 4 is incorporated, the thickness of the carbon heat insulating material constituting the bottom surface portion 60 is set to 90 mm, and the crucible 1 And the heat insulating space 6 in which the carbon heater 30 is accommodated. At this time, the distance between the bottom surface portion 60 made of the carbon heat insulating material and the disk-shaped heater portion 4 was 30 mm.

  Then, about 23 kg of high-purity (6N) alumina is put in the crucible 1 as a raw material, the carbon heater 30 having the cylindrical heater part 3 and the disk-like heater part 4 is operated and heated to 2050 ° C. or higher, A high purity alumina melt was produced. In addition, the input electric power at the time of crystal growth was 27.12 kW for the cylindrical heater portion 3 and 16.08 kW for the disk-like heater portion 4, for a total of 43.20 kW.

  Next, using a sapphire single crystal as the seed crystal 11, the sapphire single crystal is grown by lowering the temperature at a rate in the range of 0.10 ° C. to 0.30 ° C./hour while pulling it in contact with the raw material melt 10. It was.

  When the carbon heater 30 having the cylindrical heater portion 3 and the disc-like heater portion 4 and the carbon columnar heater electrode 5 were observed after the completion of the crystal growth, adhesion of fine carbon powder was not observed.

  Furthermore, when the sapphire single crystal taken out from the sapphire single crystal growing apparatus was processed into a substrate and subjected to appearance inspection, it was found that all the obtained substrates did not contain bubbles.

[Example 2]
The heat insulating space 6 in which the crucible 1 and the carbon heater 30 are accommodated was assembled in the same manner as in Example 1 except that the thickness of the carbon heat insulating material constituting the bottom surface portion 60 of the heat insulating space 6 was 110 mm. . At this time, the distance between the bottom surface portion 60 made of the carbon heat insulating material and the disk-shaped heater portion 4 was 10 mm.

  And when it carried out similarly to Example 1 except the above, the input electric power at the time of crystal growth was 26.81 kW for the cylindrical heater part 3 and 15.74 kW for the disk-shaped heater part 4, and was a total of 42.55 kW. .

  When the carbon heater 30 having the cylindrical heater portion 3 and the disc-like heater portion 4 and the carbon columnar heater electrode 5 were observed after the completion of the crystal growth, adhesion of fine carbon powder was not observed.

  Furthermore, when the sapphire single crystal taken out from the sapphire single crystal growing apparatus was processed into a substrate and subjected to appearance inspection, it was found that 10% of the substrate contained bubbles.

[Comparative Example 1]
The heat insulating space 6 in which the crucible 1 and the carbon heater 30 are housed is the same as in Example 1 except that the thickness of the carbon heat insulating material constituting the bottom surface portion 60 of the heat insulating space 6 is 80 mm. Assembled. At this time, the distance between the bottom surface portion 60 made of the carbon heat insulating material and the disk-shaped heater portion 4 was 40 mm.

  And when it carried out similarly to Example 1 except having mentioned above, the input electric power at the time of crystal growth was 28.08 kW for the cylindrical heater part 3 and 16.55 kW for the disk-shaped heater part 4, and was a total of 44.63 kW. .

  After the completion of crystal growth, the carbon heater 30 having the cylindrical heater portion 3 and the disk-like heater portion 4 and the carbon columnar heater electrode 5 were observed, and adhesion of fine carbon powder was observed.

  Furthermore, when the sapphire single crystal taken out from the sapphire single crystal growing apparatus was processed into a substrate and subjected to appearance inspection, it was found that 50% of the substrate contained bubbles.

  According to the sapphire single crystal growing apparatus according to the present invention, the incorporation of carbon monoxide into the raw material melt caused by the scattering of carbon during crystal growth is prevented, whereby a high quality sapphire single crystal that does not contain bubbles. Therefore, it has the industrial applicability used as a board | substrate for obtaining an optical material.

Explanatory drawing which shows schematic structure of the sapphire single crystal growth apparatus which concerns on this invention. Explanatory drawing which shows schematic structure of the sapphire single crystal growth apparatus which concerns on a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crucible 2 Support shaft 3 Cylindrical heater part 4 Disc shaped heater part 5 Columnar heater electrode 6 Heat insulation space room 7 Furnace body 8 Insulating cylinder 9 Pulling shaft 10 Raw material melt 11 Seed crystal 12 Sapphire single crystal 30 Carbon heater 60 Heat insulation Bottom portion of space chamber 61 61 Top surface portion of heat insulation space chamber 6

Claims (1)

A crucible filled with a sapphire raw material, a carbon heater having a cylindrical heater portion for heating the outer peripheral surface of the crucible and a disk-like heater portion for heating the bottom surface of the crucible, and a crucible and a carbon heater composed of a heat insulating material made of carbon A heat-insulating space chamber in which the crucible is kept warm, an insulating cylinder fitted into an opening provided in the bottom surface of the heat-insulating space chamber, and a distal end side connected to the carbon heater inserted into the insulating cylinder In a sapphire single crystal growing apparatus for producing a sapphire single crystal from a melt of the sapphire raw material by a rotational pulling method,
The thickness of the heat insulating material constituting the bottom surface portion of the heat insulation space chamber is set to 90 mm or more, and the distance from the surface of the bottom surface portion of the heat insulation space chamber to the lower end of the disk-shaped heater portion is set to 10 mm or more. Sapphire single crystal growth equipment.

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