JP4930166B2 - Method for producing aluminum oxide single crystal - Google Patents

Description

  The present invention relates to a method for producing an aluminum oxide single crystal. More specifically, the present invention relates to a method for efficiently producing high-quality aluminum oxide while suppressing the occurrence of low-angle boundaries by a melt solidification method in which a grown crystal is pulled from a raw material melt. The present invention relates to a method for producing a single crystal.

  Aluminum oxide single crystals are often used as crystal substrates for epi-growth when producing blue LEDs or white LEDs. These LEDs are expected to spread in the lighting field from the viewpoint of energy saving, and are attracting attention from various fields.

  There are various methods for growing oxide single crystals, but most of the oxide single crystal materials such as LN, LT, YAG and aluminum oxide are obtained by melt solidification because their crystal characteristics and large crystal diameters are obtained. It is nurtured. In particular, the Czochralski method (Cz method), which is one of the melt solidification methods, is most widely used because of its versatility and high technical perfection.

In order to produce an oxide single crystal by the Czochralski method, first, an oxide raw material is filled in a crucible, and the raw material is melted by heating the crucible by a high frequency induction heating method or a resistance heating method. After the raw material is melted, a seed crystal cut in a predetermined crystal orientation is brought into contact with the surface of the raw material melt, and a single crystal is grown by pulling upward at a predetermined speed while rotating the seed crystal at a predetermined rotation speed (for example, , See Patent Document 1).
However, when an aluminum oxide single crystal is grown by a melt solidification method typified by the Czochralski method, a low-angle grain boundary is likely to be generated in the crystal. It is said that if a low-angle grain boundary (hereinafter simply referred to as a grain boundary) is formed on a wafer serving as a crystal substrate for epi growth, the LED characteristics will be adversely affected. It is difficult to obtain a crystal substrate.

When growing aluminum oxide single crystals by the melt solidification method so far, when the crystal orientation of the seed crystal is the c-axis, dislocations due to temperature distribution in the c-plane, which is a sliding surface, form grain boundaries. It is known. On the other hand, when the crystal is grown with the crystal orientation as the a-axis, the formation of grain boundaries is suppressed to some extent, so industrially, the crystal grown in the a-axis direction is cut out in the c-axis direction. Thus, a method for producing a substrate for epi growth is used.
However, even with a-axis growth, the generation of grain boundaries has not been sufficiently suppressed. In the case of a crystal with many grain boundaries, even when a crystal substrate for epi-growth is produced by cross-cutting in the c-axis direction, If this occurs, it cannot be used as a crystal substrate for epi growth, and there is a problem that the yield is greatly reduced. Patent Document 1 discloses a method of using a crystal rod (seed crystal) having a specific crystal orientation, inserting it into an alumina melt, and pulling up a massive single crystal that is crystallized at a specific rotation speed. However, it was not possible to produce a single crystal with few grain boundaries with good reproducibility.
JP-A-51-87197

  An object of the present invention is to provide a method for efficiently producing a high-quality aluminum oxide single crystal while suppressing the generation of a low-angle grain boundary (boundary) by a melt solidification method that pulls a growth crystal from a raw material melt. is there.

  The inventors of the present invention have made extensive studies to solve the above-described conventional problems, and observed the surface of the seed crystal in detail when growing the aluminum oxide single crystal by the melt-solidification method, and the tip of the seed crystal was significantly melted. When the crystal is grown in a state, that is, when the temperature of the melt is excessively high during seeding when the seed crystal is brought into contact with the melt, the surface of the seed crystal is melted and grain boundaries are easily generated. Even if it is obtained by a-axis growth, many grain boundaries will be generated. On the other hand, even if the melt temperature is too low, crystal growth will occur immediately after the seed crystal contacts the melt surface. Since it started, it was found that many grain boundaries were generated in the fast-growing portion and a good quality crystal could not be obtained, and the present invention was completed.

That is, according to the first aspect of the present invention, after the raw material for single crystal is put in the crucible in the furnace and heated and melted , the seed crystal having a Si concentration of 20 ppm or less is brought into contact with the raw material melt to raise the grown crystal. In a method for producing an aluminum oxide single crystal by melt solidification method, when the raw material melt is heated and the melt temperature is adjusted, the raw material is previously set to 5 ° C to 10 ° C higher than the melting point of the single crystal raw material. After heating the melt and holding the seed crystal for 2 hours or more, the temperature of the raw material melt is heated again, and the melt temperature is 15 ° C. to 50 ° C. higher than the melting point of the single crystal raw material. It was maintained so that, then, in a state where the surface of the seed crystal does not substantially melt, the material melt to contacting the seed crystal, characterized by pulling the growing crystal while suppressing the occurrence of grain boundary Manufacturing method of aluminum oxide single crystal There is provided.

According to the second invention of the present invention, in the first invention, when the raw material melt is heated to a temperature 5 to 10 ° C. higher than the melting point of the single crystal raw material, the position of the seed crystal is There is provided a method for producing an aluminum oxide single crystal, characterized in that the aluminum oxide single crystal is 350 mm to 400 mm away from the melt surface.
According to the third invention of the present invention, in the first or second invention, when the temperature of the raw material melt is raised to 5 to 10 ° C. higher than the melting point of the single crystal raw material, the seed crystal is gradually added. A method for producing an aluminum oxide single crystal is provided, characterized in that the aluminum oxide single crystal is brought close to the melt surface and positioned 100 to 150 mm away from the melt surface after the temperature rise.
According to the fourth invention of the present invention, in the first invention, when the seed crystal is brought into contact with the raw material melt, the melt temperature is adjusted within a temperature range lower than the temperature at which the seed crystal surface melts or 2 ° C. A method for producing an aluminum oxide single crystal is provided.
Furthermore, according to the fifth aspect of the present invention, in the first aspect, the melt temperature is measured by a platinum rhodium alloy B thermocouple installed at a position within 20 mm below the bottom of the crucible. The manufacturing method of the aluminum oxide single crystal characterized by these is provided.

According to the present invention, when growing an aluminum oxide single crystal in the a-axis direction using the seed crystal cut in the a-axis direction, the raw material melt is heated, and the melt temperature is the melting point of the single crystal raw material. Since the seed crystal is also heated by adjusting the temperature to 15 ° C to 50 ° C, the melting of the seed crystal surface is suppressed during seeding, and crystal growth can be started in an optimal seeding state. As a result of the occurrence of dislocation being suppressed at the boundary between the crystal and the melt, the generation of grain boundaries is reduced, and a high-quality single crystal can be produced.
By using the single crystal thus obtained, electronic component materials and optical component materials having excellent characteristics can be provided.

  Hereinafter, the manufacturing method of the aluminum oxide single crystal of this invention is demonstrated in detail using drawing.

That is, in the method for producing an aluminum oxide single crystal of the present invention, a raw material for single crystal is put in a crucible in a furnace and heated and melted, and then a seed crystal having a Si concentration of 20 ppm or less is brought into contact with the raw material melt to obtain a grown crystal. In the method of producing an aluminum oxide single crystal by the melt-solidification method of pulling up, when the raw material melt is heated and the melt temperature is adjusted, the temperature is 5 to 10 ° C. higher than the melting point of the single crystal raw material in advance. After the raw material melt is heated and the seed crystal is heated by holding it for 2 hours or more, the raw material melt is heated again and the melt temperature is 15 ° C. to 50 ° C. higher than the melting point of the single crystal raw material. After maintaining at a high temperature , the seed crystal is then brought into contact with the raw material melt in a state where the surface of the seed crystal is not substantially melted, and the grown crystal is pulled up while suppressing the generation of grain boundaries. To do.

In the present invention, an ordinary aluminum oxide powder is used as a raw material for a single crystal. The aluminum oxide powder is aluminum oxide substantially composed of two elements of Al and O. In addition to Al and O, Ti, Cr, Si, Ca, Mg, and the like may be included in accordance with the type of target aluminum oxide single crystal. Among these, Si, Ca, Mg and the like can be inevitably contained as components of the sintering aid, but the content is desirably as small as possible. In particular, Si is desirably 10 ppm by weight or less. The diameter and density of aluminum oxide are not particularly limited, but for handling, for example, the diameter is preferably 10 mm or less, preferably 5 mm or less, and the density is 5 g / cm ³ or less, preferably 3 g / cm. What is ³ or less is good.

If the single crystal raw material is an aluminum oxide sintered body, a commercially available product for semiconductor production can be used, but it can also be produced by the following method. For example, α alumina particles are added as seeds to a sol or gel of an α alumina precursor that is converted to α alumina when baked, and after the sol is gelled, the gel of the α alumina precursor to which the seed crystal is added is 900 to Sinter at a temperature of 1350 ° C. and grind the resulting sintered product. A crackle raw material obtained by pulverizing a raw material for aluminum oxide single crystal produced by the Bernoulli method to a diameter of 20 mm or less can also be used. This is a very small specific surface area of less than 0.1 m ² / g, and there is little adsorbed gas.

  In the present invention, in order to grow an aluminum oxide single crystal, a conventional oxide single crystal growing apparatus based on the Czochralski method can be used. For example, a crucible formed of a noble metal, a furnace material formed of alumina or the like as a heat insulating material around the crucible, and an apparatus in which a high-frequency induction coil as a heating device is disposed outside the furnace material. The apparatus is provided with a window for observing the melt surface and a CCD camera for monitoring seed crystals and grown crystals.

  Since the melting point of alumina, which is a single crystal raw material, is 2050 ° C., it is preferable to use an iridium-made crucible. A heat insulating material such as foamed zirconia may be filled as a heat insulating material. Above the crucible, a pulling device for pulling up the single crystal from the material melt is provided, and the furnace material is shielded by a shielding plate. The heating temperature of the crucible is measured with a platinum rhodium alloy B thermocouple installed at a position within 20 mm below the bottom of the iridium crucible.

  First, the raw material for single crystal described above is put in a crucible, and then the crucible is heated by a high frequency induction coil to melt the raw material to obtain a raw material melt. The heating rate until the raw material reaches the melting point is not particularly limited, but it is possible to suppress the incorporation of bubbles into the single crystal by heating gradually over a long time without rapidly heating. For example, it is desirable to heat gradually over 10 hours, especially over 12 hours.

Next, even after melting the raw material for single crystal, the obtained melt is heated for 3 hours or more, particularly 5 hours or more after the melting of the raw material. At this time, the oxygen concentration is preferably 10 to 500 Pa, particularly 100 to 300 Pa in terms of oxygen partial pressure. When the raw material is sufficiently melted, the seed crystal is brought into contact with the melt surface to start seeding. However, if the melt temperature is raised too much, the seed crystal surface is melted. For this reason, the temperature adjustment after melting the raw material is maintained at a high temperature of 5 to 10 ° C. from the melting point, and then the crucible is gradually heated so that the melt temperature is 15 to 50 ° C. higher than the melting point of the single crystal raw material. It is preferable to prevent the seed crystal surface from melting and to obtain an optimum seeding state by setting the temperature to a two-stage temperature maintained at an optimum seeding temperature within the range. The optimum seeding temperature is preferably in the range of 15 ° C. to 40 ° C., more preferably in the range of 15 ° C. to 30 ° C., higher than the melting point of the single crystal raw material. The melt is heated in the first stage in advance, and at the same time as the temperature of the melt is raised, the seed crystal is also heated. By preliminarily heating in this manner, it becomes easier to adjust the melt temperature in the second stage.
In the two-step temperature increase of the melt, first, the seed crystal is held 350 mm to 400 mm above the melt surface, and at least 2 to 5 ° C. from the temperature at which the raw material melts (melting point). Hold for more than an hour. If the position of the seed crystal is closer than 350 mm from the melt surface, the temperature of the seed crystal will rise too much, and if it is above 400 mm or if the holding time is less than 2 hours, the temperature of the seed crystal cannot be raised sufficiently. Neither is efficient. After the first stage heating, the seed crystal held 350 mm to 400 mm above the melt surface is desirably lowered to a position 50 to 100 mm above the melt surface, for example, over 1 hour.
Thereafter, the crucible is gradually heated, and at the same time, the seed crystal is lowered to just above the surface of the melt so that the melt temperature is 15 ° C. to 50 ° C. higher than the melting point of the single crystal raw material. If the melt temperature is outside this range and the melt temperature is not 15 ° C higher than the melting point of the single crystal raw material, or if it is higher than 50 ° C, the subsequent temperature rise and fall will be lost, and the seed crystal Hard to seed at the proper temperature. Even during the growth of this single crystal, the oxygen concentration is preferably 10 to 500 Pa, particularly 100 to 300 Pa in terms of oxygen partial pressure.
Thus, in the present invention, after 3 hours or more, especially 5 hours or more have elapsed from the melting of the raw material, the optimum temperature is increased by increasing the melt temperature while maintaining the temperature range sufficiently low so that the surface of the seed crystal during heating does not melt. It is important to set the ding temperature.

A crystal used as a seed crystal was obtained by cutting an aluminum oxide single crystal lump obtained by a production method such as the Czochralski method, Kilopros, or HEM into a predetermined crystal orientation, that is, in either the a-axis direction or the c-axis direction. And can be appropriately selected depending on the intended use of the obtained single crystal product. Moreover, the Si concentration in the crystal is 20 ppm by weight or less, preferably 15 ppm by weight or less. The analysis of Si can be performed, for example, by a method described in Japanese Patent Application Laid-Open No. 2007-33221. In this method, an aluminum oxide seed crystal sample, which is difficult to be made into a solution, is made into a solution by eliminating impurities and contamination as much as possible, and a trace element in the aluminum oxide single crystal is quantified. In this trace element determination method, a sample is decomposed by an acid decomposition method or an alkali melting method, and the trace element in the obtained solution is measured by flow injection introduction-ICP / mass spectrometry. As a measuring condition in ICP / mass spectrometry, the Si element, the mass number 30, it is desirable that the gas species _{H 2.}

A state in which the seed crystal is seeded by contacting the surface of the melt is shown in FIG. In the present invention, as described above, when the grown crystal is pulled up, the surface of the seed crystal must be maintained in an unmelted state. In addition, at the boundary between the seed crystal and the melt, the shape of the meniscus having a diameter smaller than the size of the four sides of the seed crystal is melted at an angle in contact with the melt at the tip of the seed crystal. It is desirable to maintain the state.
If the melt temperature is appropriate, the tip neck portion of the single crystal pulled up by the seed crystal is in a state as shown in (1) in FIG. The melt temperature at this time substantially corresponds to the melting point of the seed crystal, which is hereinafter also referred to as an appropriate seeding temperature. The proper seeding temperature varies depending on the concentration of Si contained in the crystal and the degree of deterioration of the heat insulating material around the crucible, but is within a range of 15 ° C. to 50 ° C. from the melting point. Therefore, the melt is heated to adjust the melt temperature to be within this range, and then the seed crystal is brought into contact with the melt. After fully blending the seed crystal with the melt, the single crystal is grown by starting the pulling while rotating the seed crystal with a pulling device. As a result, the tip neck portion of the single crystal pulled up in contact with the seed crystal and the melt is formed thin enough to not hinder the progress of crystal growth.
Even if the melt temperature is further increased and 2 ° C higher than the appropriate seeding temperature, after the seed crystal is sufficiently mixed with the melt, the pulling is started while rotating the seed crystal with the pulling device. A single crystal can be grown. Thereby, the tip neck portion (4) of the single crystal pulled up by the seed crystal is formed narrower. In this case, a grain boundary is generated by melting the surface of the seed crystal. If the seeding temperature is too high, crystal growth does not proceed after the start of pulling, and the seeding temperature is separated from the melt. That is, when the melt temperature rises by 3 ° C or more from the appropriate seeding temperature, melting starts at the tip of the seed crystal, and when the melt temperature rises by 4 ° C or more, melting of the seed crystal surface proceeds rapidly. . For this reason, it is necessary to adjust the heating temperature of the melt so that the melt temperature does not become too high.
In order to adjust the seed crystal to an appropriate seeding temperature and maintain the surface of the seed crystal in an unmelted state, a method of precisely adjusting the melt temperature is generally used. There is also a way to reduce the degree. It is also possible to suppress the melting of the seed crystal by adjusting the relative position of the iridium crucible and the high frequency induction coil, or by devising the structure of the heat insulating material around the crucible to increase the vertical temperature gradient.

On the other hand, when the seeding temperature is 3 ° C. lower than the appropriate seeding temperature, crystal growth starts immediately after the seed crystal comes into contact with the melt surface, and the tip neck portion of the single crystal to be pulled up becomes as shown in (3). Due to defects such as the occurrence of many grain boundaries in the fast part, good quality crystals cannot be obtained. This tendency becomes more prominent when the melt temperature becomes lower. For example, when the temperature is lower by 4 ° C. or more than the appropriate seeding temperature, the tip neck of the single crystal to be pulled becomes as shown in (2), and crystal growth occurs. Grain boundaries are generated in the fast part. For this reason, it is necessary to adjust the melt temperature so that the melt temperature does not become too low.
Thus, in the present invention, the seeding temperature when the seed crystal is brought into contact with the surface of the raw material melt is precisely adjusted, and the melt temperature is adjusted in the range of 15 ° C. to 50 ° C. higher than the melting point of the single crystal raw material. Thus, it is most preferable that the temperature falls within a range from a temperature at which the seed crystal melts to a temperature lower by 2 ° C.

  The above seeding temperature is measured by a platinum rhodium alloy B thermocouple installed at the bottom of the crucible. Since the melting point of alumina as a raw material is about 2050 ° C., the thermocouple to be installed must be installed away from the crucible bottom even if it is a high-temperature thermocouple. However, if the distance is too large, the behavior of the raw material such as heat of fusion cannot be observed precisely, so the distance away from the crucible bottom is 20 mm or less. While looking at the thermocouple output installed at the bottom of the crucible, change the input power of the high frequency induction coil to adjust to the appropriate seeding temperature.

  Single crystals are grown by using crystals with a Si concentration of 20 ppm by weight or less as seed crystals, forming the neck as described above, and then adjusting the rotation speed and pulling speed to form the shoulder. Subsequently, the straight body portion is formed. The crystal shape is adjusted by measuring the crystal weight during growth, deriving the diameter, growth rate, and the like by calculation, and adjusting the rotation speed and pulling speed. Also, the melt temperature can be controlled by feeding back the change in crystal weight to the power applied to the high frequency induction coil. The rotational speed and the lifting speed are not particularly limited, but the rotational speed is preferably 2 to 5 revolutions per minute, and the lifting speed is preferably 1 to 2 mm / h.

In the present invention, when the melt is heated, the surface of the seed crystal is maintained in an unmelted state, the melt temperature is precisely adjusted, and the aluminum oxide single crystal is gradually grown at an appropriate seeding temperature. Furthermore, the amount of grain boundaries generated at the tip neck of the single crystal pulled up by the seed crystal is reduced, and a high-quality single crystal can be manufactured.
When a crystal having a Si concentration of 20 ppm by weight or less, preferably 15 ppm by weight or less is used as a seed crystal, the seed crystal surface melts even if the seeding temperature slightly deviates from −2 ° C. to + 2 ° C. Does not occur, and the formation of small-angle grain boundaries in the grown crystal is significantly reduced.
The reason why a high-quality single crystal can be produced by using a low concentration seed crystal in which the Si concentration in the crystal is 20 ppm by weight or less has not yet been fully elucidated. Although there may be an influence due to Ca, Mg, etc. contained as impurities, the more the Si crystal used in the seed crystal, the more easily the seed crystal surface melts during seeding. When it comes into contact with the melt, it enters the crystal lattice of pure aluminum oxide, which is considered to cause the propagation of grain boundaries.

  By slicing the wafer from this single crystal and polishing it, it is possible to obtain a crystal substrate for epi growth. In single crystals, there are very few low-angle grain boundaries, and since there are few pits and microbubbles, it is possible to provide electronic component materials and optical component materials having excellent characteristics.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[Example 1]
10 kg of 4N (99.99%, Si concentration: 10 wt ppm>) Al ₂ O ₃ raw material was charged into an iridium crucible of an oxide single crystal growing apparatus by the Czochralski method. As a seed crystal, an aluminum oxide single crystal cut in the a-axis direction from a crystal having a Si concentration of 15 ppm was used.
The Al ₂ O ₃ raw material was gradually heated over 12 hours until reaching the melting point. After melting the raw material, the melt temperature is maintained at a high temperature of 10 ° C. from the melting point for 2 hours, and the seed crystal held 400 mm above the melt surface is rotated at a speed of 15 rpm while rotating at a speed of 2 revolutions per minute. It was lowered to 100 mm above the melt surface. Three hours after the melting of the raw material, the crucible started to be gradually heated, and at the same time, the seed crystal was lowered to just above the melt surface. Five hours after the melting of the raw material, seeding was started by bringing the tip of the seed crystal into contact with the melt when the melt temperature was 30 ° C. higher than the melting point.
The state of seeding was observed with a CCD camera, the melt temperature was adjusted so that the seeding temperature was in an appropriate state, and the neck portion was in the state indicated by (1) in FIG. The melt temperature at this time was 35 ° C. higher than the melting point of the Al ₂ O ₃ raw material. After confirming that the surface of the seed crystal was not melted, crystal growth was performed by raising the seed crystal at a pulling speed of 2 mm / h.
As a result, a crystal having a diameter of 106 mm and a length of the straight body portion of 122 mm was obtained. When the appearance of the crystal was observed, no grain boundary was observed. Further, when this crystal was used as a wafer and an X-ray topographic image was observed, grain boundaries could not be confirmed.

[Example 2]
In the same manner as in Example 1, except that the melt temperature was lowered by 2 ° C. from the place where the appropriate seeding temperature was reached in Example 1 and the seeding was performed in a state where the neck portion was close to (3) in FIG. Made growth. No melting of the seed crystal surface was observed during seeding.
As a result, a crystal having a diameter of 105 mm and a length of the straight body portion of 124 mm was obtained. When the appearance of the crystal was observed, grain boundaries were observed in the region from the shoulder portion to the straight body portion of 22 mm. A wafer was prepared from a region where no crystal grain boundary was observed, and when an X-ray topographic image was observed, no grain boundary could be confirmed.

[Comparative Example 1]
Crystal growth was carried out in the same manner as in Example 1 except that the melt temperature was raised by 3 ° C. from the place where the appropriate seeding temperature was reached in Example 1 and the seeding was performed in the state of (4) in FIG. Went. Melting was observed on the surface of the tip of the seed crystal during seeding.
As a result, a crystal having a diameter of 108 mm and a length of the straight body portion of 125 mm was obtained. When the appearance of the crystal was observed, a grain boundary was observed in the region of 85 mm from the seeding portion to the straight barrel portion. A wafer was produced from this crystal and an X-ray topographic image was observed. As a result, grain boundaries were confirmed on 35 out of 50 wafers.

[Comparative Example 2]
The same procedure as in Example 1 was performed except that the melt temperature was lowered by 4 ° C. from the place where the appropriate seeding temperature was reached in Example 1 and the seeding was performed in the state of (2) in FIG. . No melting of the seed crystal surface was observed during seeding.
As a result, a crystal having a diameter of 106 mm and a length of the straight body portion of 123 mm was obtained. When the appearance of the crystal was observed, grain boundaries were observed in the region of 123 mm from the seeding portion to the straight barrel portion. A wafer was produced from this crystal and an X-ray topographic image was observed. As a result, grain boundaries were confirmed in 50 out of 50 wafers.

It is explanatory drawing which shows the seeding state in case seeding temperature differs.

Explanation of symbols

1 Neck when growing a single crystal at an appropriate seeding temperature 2 Neck when growing a single crystal at 4 ° C or more lower than the appropriate seeding temperature 3 A single crystal at a temperature 2 ° C lower than the appropriate seeding temperature Neck 4 when grown 4 Neck when a single crystal is grown at a temperature 3 ° C higher than the appropriate seeding temperature

Claims (5)

In a method for producing an aluminum oxide single crystal by a melt solidification method in which a raw material for a single crystal is put in a crucible in a furnace and heated and melted, and then a seed crystal having a Si concentration of 20 ppm or less is brought into contact with the raw material melt to pull up the grown crystal ,
When the raw material melt is heated and the melt temperature is adjusted, the raw material melt is heated in advance so as to be 5 ° C. to 10 ° C. higher than the melting point of the single crystal raw material, and kept for 2 hours or longer. After heating the crystal, the raw material melt is heated again to maintain the melt temperature at 15 ° C. to 50 ° C. higher than the melting point of the single crystal raw material , and then the surface of the seed crystal A method for producing an aluminum oxide single crystal, wherein the seed crystal is brought into contact with the raw material melt in a state in which the material does not substantially melt, and the grown crystal is pulled up while suppressing the generation of grain boundaries. When the raw material melt is heated to a temperature higher by 5 ° C. to 10 ° C. than the melting point of the single crystal raw material, the position of the seed crystal is 350 mm to 400 mm away from the melt surface. The manufacturing method of the aluminum oxide single crystal of Claim 1 . When the temperature of the raw material melt is raised to 5 ° C to 10 ° C higher than the melting point of the single crystal raw material, the seed crystal is gradually brought closer to the melt surface, and after the temperature rise, it is 100 to 150 mm away from the melt surface. The method for producing an aluminum oxide single crystal according to claim 1 , wherein the aluminum oxide single crystal is at a position.   2. The production of an aluminum oxide single crystal according to claim 1, wherein when the seed crystal is brought into contact with the raw material melt, the melt temperature is adjusted within a temperature range from a temperature at which the surface of the seed crystal melts to 2 ° C. Method.   The method for producing an aluminum oxide single crystal according to claim 1, wherein the melt temperature is measured by a B thermocouple made of a platinum rhodium alloy placed at a position within 20 mm below the bottom of the crucible.

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