JP2016199416A - Method for manufacturing sapphire single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a sapphire single crystal, capable of suppressing the occurrence of voids in the lower portion of a growing crystal and the incorporation of metal particles into the growth crystal.SOLUTION: A method for manufacturing a sapphire single crystal includes manufacturing a sapphire single crystal 22 using a raw material melt 21 obtained by melting a sapphire raw material charged in a crucible 11 including one or more kinds of metal selected from molybdenum and tungsten. The ignition loss of the sapphire raw material is 0.01 wt% or less.SELECTED DRAWING: Figure 1

Description

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

  The sapphire single crystal is used as a light emitting diode (LED) substrate material, an optical crystal, and the like, and the demand for a sapphire single crystal substrate is increasing with the demand for light emitting diodes due to the recent demand for energy saving.

  As a method of manufacturing a large-sized sapphire single crystal used for a substrate material of a light emitting diode, a semiconductor wafer crystal, an optical crystal, etc., a Czochralski method (Cz method), a kilopross method, or an EFG method (Edge-defined Film- fed Growth) and the like are known.

  In the manufacture of sapphire single crystals, various studies have been made on device materials and device configurations so that large, high-quality bulk single crystals can be obtained at low cost.

  Specifically, for example, since the melting point of sapphire is high, the in-furnace material such as a crucible is selected and used from the viewpoint of heat resistance and the like.

  Examples of a crucible material that can be used for manufacturing a sapphire single crystal include iridium, molybdenum, tungsten, and alloys thereof. However, since iridium is very expensive, it is economically disadvantageous in terms of equipment, and a crucible made of molybdenum, tungsten, or an alloy thereof has been used to produce a large sapphire single crystal.

  However, when molybdenum, tungsten, or an alloy thereof is used for the crucible material, these materials are easily oxidized at a high temperature. Since the oxides of molybdenum and tungsten have high vapor pressure, the crystal surface grown by the oxide vapor and the raw material melt are contaminated, and the phenomenon that the crucible material is mixed into the crystal occurs. There were problems such as coloring and a decrease in purity.

  Therefore, the inventors of the present invention used a heat-resistant crucible containing no iridium as a crucible in Patent Document 1, and when the sapphire raw material powder was heated and melted, the atmosphere gas was replaced with an inert gas in advance, and subsequently Discloses a method for growing a sapphire single crystal in which a sufficient amount of inert gas is maintained to maintain a state in which substantially no oxygen is present in the chamber. Patent Document 1 also discloses that a molybdenum or tungsten crucible can be suitably used as a heat-resistant crucible not containing iridium.

  According to the method for growing a sapphire single crystal disclosed in Patent Document 1, a good sapphire single crystal that does not contain inclusions can be obtained.

JP 2008-007354 A

  However, when the inventors of the present invention repeated the growth of the sapphire single crystal by the method for producing a sapphire single crystal disclosed in Patent Document 1, when a large amount of voids occur in the lower part of the grown crystal, In some cases, uptake may occur.

  Therefore, in one aspect of the present invention, in view of the problems of the above-described conventional technology, a method for producing a sapphire single crystal capable of suppressing generation of voids in the lower portion of the grown crystal and incorporation of metal particles into the grown crystal is provided. Objective.

In order to solve the above-described problem, according to one aspect of the present invention, a sapphire single crystal using a raw material melt obtained by melting a sapphire raw material filled in a crucible containing one or more kinds of metals selected from molybdenum and tungsten. A method for producing a sapphire single crystal,
A method for producing a sapphire single crystal in which the ignition loss of the sapphire raw material is 0.01 wt% or less can be provided.

  According to one embodiment of the present invention, it is possible to provide a method for producing a sapphire single crystal that can suppress generation of voids at the lower portion of the grown crystal and incorporation of metal particles into the grown crystal.

Explanatory drawing of the structural example of a single crystal growth apparatus.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and the following embodiments are not departed from the scope of the present invention. Various modifications and substitutions can be made.

  One structural example of the manufacturing method of the sapphire single crystal of this embodiment is demonstrated below.

  The manufacturing method of the sapphire single crystal of this embodiment manufactures a sapphire single crystal using the raw material melt which melted the sapphire raw material with which the crucible containing one or more types of metals selected from molybdenum and tungsten was melted. The present invention relates to a method for producing a sapphire single crystal. And the sapphire raw material whose ignition loss is 0.01 wt% or less can be used.

Hereinafter, explanation will be given with specific examples. Single-crystal growth apparatus The single-crystal growth apparatus which can be used in the manufacturing method of the sapphire single crystal of this embodiment is not specifically limited, Various single-crystal growth apparatuses can be selected and used according to the manufacturing method of a single crystal. Here, FIG. 1 shows a configuration example of a single crystal growing apparatus by the Czochralski method (Cz method). FIG. 1 schematically shows a cross-sectional view of a surface passing through the central axis of a crucible disposed inside the single crystal growth apparatus.

  In the single crystal growing apparatus 10 shown in FIG. 1, a crucible 11 into which a single crystal raw material is placed can be disposed on a support shaft 13 in a chamber 12. In order to melt the single crystal raw material, for example, a side heater 14 can be provided on the side surface of the crucible 11. Further, a disc-shaped bottom heater 15 can be arranged below the crucible 11 so that the support shaft 13 penetrates.

  In addition, as a method for heating the crucible, there are a high-frequency heating method and a resistance heating method. In the high-frequency heating method, since the crucible itself generates heat, a temperature gradient in the diameter direction of the crucible increases. For this reason, the diameter of the crystal to be produced is about 50% of the diameter of the crucible, and the apparatus size is increased to produce a large crystal. In addition, since the temperature gradient during crystal growth is large, strain due to the temperature difference may enter the grown crystal.

  On the other hand, in the case of the resistance heating method, since the heater disposed around the crucible generates heat and the atmosphere around the crucible is heated, the temperature gradient in the crucible can be reduced as compared with the high frequency heating method. Therefore, when the crystal is grown by resistance heating method, the problem of high-frequency heating method that strain caused by temperature difference may enter the crystal is solved, and large sapphire single crystal can be manufactured at low cost. Become.

  For this reason, the method of heating the crucible in the single crystal growth apparatus used in the method for manufacturing a sapphire single crystal of this embodiment is a resistance heating method in which the crucible is directly heated by a heater as in the single crystal growth apparatus 10 shown in FIG. It is preferable that

  A heat insulating material 16 can be provided along the inner surface of the chamber 12 around the side heater 14 and below the bottom heater 15. A gas supply pipe 17 and a gas discharge pipe 18 for controlling the atmosphere in the chamber 12 can be provided on the top and bottom of the chamber 12. In addition, a pulling shaft 19 that can move up and down can be provided in the upper part of the crucible 11 so as to penetrate the heat insulating material 16. The pulling shaft 19 can be configured so that the seed crystal 20 can be fixed to the tip.

  The material of the crucible 11 can be a metal containing one or more selected from molybdenum and tungsten. In particular, the material of the crucible 11 is preferably molybdenum, tungsten, or an alloy thereof.

  The heater and / or the heat insulating material installed in the chamber 12 is preferably made of carbon. That is, in the case of the single crystal growth apparatus 10 shown in FIG. 1, it is preferable that any one or more of the side heater 14, the bottom heater 15, and the heat insulating material 16 is made of carbon. All of the side heater 14, the bottom heater 15, and the heat insulating material 16 can be made of carbon.

  This is because, in a single crystal growth apparatus, for example, a resistance heater made of tungsten is used as a heater, and a reflective plate made of a refractory metal such as tungsten or an alloy thereof may be used as a heat insulating material. Is brittle and expensive. For this reason, as described above, the heater and / or the heat insulating material is preferably made of carbon.

When the side heater 14 and / or the bottom heater 15 are made of carbon, a carbon particle or carbon fiber molded body can be used. Further, when the heat insulating material 16 is made of carbon, a carbon felt heat insulating material can be used.
2. Method for Producing Sapphire Single Crystal Next, a method for producing a sapphire single crystal will be described by taking the case of using the single crystal growth apparatus 10 shown in FIG. 1 as an example.

  In manufacturing a sapphire single crystal, first, a sapphire raw material as a single crystal raw material is filled in the crucible 11 of the single crystal growing apparatus 10 shown in FIG. 1, and the side heater 14 and the bottom heater 15 are operated to operate the sapphire. The raw material melt 21 can be formed by heating the raw material. Thereafter, seeding is performed in which the seed crystal 20 is brought into contact with the surface of the raw material melt 21, and then the sapphire single crystal as the growth crystal 22 can be grown while pulling up the seed crystal 20.

Below, the example of 1 structure of the specific procedure of the manufacturing method of a sapphire single crystal is demonstrated.
(Raw material melt forming process)
First, aluminum oxide, which is a sapphire raw material, is filled into the crucible 11 and placed in the chamber 12.

  Next, the sapphire raw material in the crucible 11 is heated and melted.

  When the sapphire material in the crucible 11 is heated and melted, the atmosphere in the chamber 12 is not particularly limited. However, when the crucible 11 is made of a metal containing molybdenum or tungsten, or when carbon is used for a heater or a heat insulating material, the above metal or Carbon may oxidize.

  When the metal or carbon is oxidized, it may cause impurities to be mixed in the grown crystal, or it may be difficult to grow a good sapphire single crystal. For this reason, it is preferable that after the chamber 12 is sealed, an inert gas atmosphere is made to flow through the gas supply pipe 17 into the chamber 12. Note that the inert gas can be supplied after evacuating the chamber 12 with a vacuum pump (not shown) before supplying the inert gas into the chamber 12.

  Although it does not specifically limit as an inert gas, Argon or helium can be used suitably. It is particularly preferable to use argon from an economical viewpoint.

  From the viewpoint of particularly suppressing the oxidation of the components in the chamber 12, it is preferable to maintain a state in which oxygen is not substantially present in the chamber 12. Then, by passing a sufficient amount of inert gas through the chamber 12, it is possible to maintain a state in which oxygen is not substantially present in the chamber 12.

  For this reason, it is preferable to supply the inert gas into the chamber 12 at a rate of 0.2% or more with respect to the volume in the chamber 12 per minute. This is because it is possible to more reliably prevent oxygen from being mixed into the chamber 12 by setting the flow rate of the inert gas to 0.2% / min or more with respect to the volume in the chamber 12.

  The upper limit of the flow rate of the inert gas is not particularly limited, but is preferably supplied into the chamber 12 at a rate of 1.3% or less per minute with respect to the volume in the chamber 12. This is because the heat balance in the chamber 12 can be stabilized by setting the flow rate of the inert gas to 1.3% / min or less with respect to the volume in the chamber 12, and as a result, a good sapphire single crystal This is because it is possible to train.

  After the supply of the inert gas into the chamber 12 is started, the gas can be discharged from the gas discharge pipe 18 so as not to be overpressurized.

  The pressure in the chamber 12 at the time of heating and melting the sapphire raw material is preferably normal pressure, that is, atmospheric pressure. This is because when the pressure in the chamber 12 is reduced, metals such as molybdenum constituting the crucible 11 are likely to sublime and the raw material melt may be contaminated. Further, when the pressure in the chamber 12 is increased, sublimation of molybdenum can be suppressed, but the apparatus needs to be designed to withstand pressure, which is not preferable from the viewpoint of economy.

  After making the inside of the chamber 12 an inert atmosphere as described above, for example, the side heater 14 and the bottom heater 15 are operated and heated to melt the sapphire raw material at a temperature equal to or higher than the melting point of sapphire (2040 ° C.). Can be obtained.

After forming the raw material melt, the seeding process described later can be carried out. However, after forming the raw material melt, seeding is performed immediately and crystal growth is started. Bubbles may be generated. The gas that causes bubbles is also generated by the decomposition of the sapphire raw material, but the gas components adsorbed or contained in the raw material are not completely removed before the raw material is melted and remain in the raw material melt, which becomes the growth crystal. Many are taken into bubbles. Therefore, after melting the sapphire raw material in the crucible, it is desirable to maintain heating for a sufficient period of time to discharge the bubbles and then perform a seeding process.
(Seeding process)
The seeding step can be performed by lowering the pulling shaft 19 holding the seed crystal 20 while rotating it and bringing the seed crystal 20 into contact with the raw material melt 21. After the seed crystal 20 is brought into contact with the raw material melt 21 in the seeding step, the seed crystal 20 can be sufficiently adjusted to the raw material melt 21 at an appropriate temperature, and then the pulling can be started.

In addition, before implementing a seeding process, it is preferable to discharge | emit the bubble in a raw material melt by maintaining heating from melting | fusing of a sapphire raw material in a raw material melt formation process as mentioned above. For this reason, it is preferable to carry out the seeding process after elapse of 3 hours or more, for example, from the melting of the sapphire raw material, and it is more preferable to perform the seeding process after elapse of 5 hours or more.
(Single crystal growth process)
The single crystal growing step can be carried out by adjusting the number of rotations and pulling speed of the pulling shaft 19 to form a neck portion and a shoulder portion of the single crystal to be grown, and subsequently forming a straight body portion.

  In the seeding process and the single crystal growing process, it is preferable to keep the inside of the chamber 12 in an inert gas atmosphere as in the raw material melt forming process.

  The method for controlling the crystal shape of the crystal being grown is not particularly limited. For example, the weight of the growing crystal is measured by a weight measuring means (not shown) connected to the pulling shaft 19, the diameter of the growing crystal, the growing speed, and the like are calculated, and the rotational speed of the pulling shaft 19 is calculated based on this. And the lifting speed can be adjusted. Further, the change in crystal weight can be fed back to the input power to the side heater 14 and / or the bottom heater 15 to control the temperature of the raw material melt 21.

  Thus, when the sapphire single crystal is grown in the crucible 11 and grown to a preset crystal length, the grown crystal 22 is separated from the raw material melt 21, and the single crystal growing step can be completed.

  The method for separating the grown crystal 22 from the raw material melt 21 is not particularly limited, but can be carried out, for example, by pulling up the pulling shaft 19 or moving the crucible 11 downward. You may carry out by pulling up the pulling shaft 19 and moving the position of the crucible 11 downward.

  After the completion of the single crystal growth step, a cooling step of lowering the temperature to room temperature or near room temperature can be performed by a sequence pattern of a control device (not shown).

In addition, although the manufacturing method of the sapphire single crystal using Cz method was demonstrated here as an example, it is not limited to the said form, The melt solidification methods, such as a chilo porous method (KY method) and a Bridgman method, etc. The manufacturing method of various sapphire single crystals which produce | generate a raw material melt in the crucible of this can be applied.
3. Sapphire Raw Material Next, a sapphire raw material that can be suitably used in the method for producing a sapphire single crystal of the present embodiment will be described. In the method for producing a sapphire single crystal of the present embodiment, a sapphire raw material having an ignition loss of 0.01 wt% or less can be used.

Aluminum oxide can be used as the sapphire raw material, and α-alumina (Al ₂ O ₃ ) is particularly preferably used as the sapphire raw material.

  The form of the sapphire raw material is not particularly limited. For example, an alumina powder, a sintered body obtained by sintering the alumina powder, or a sapphire raw material containing one or more selected from alumina particles can be used. Examples of the alumina particles include granules.

  As described above, aluminum oxide can be used as the sapphire raw material, and the material purity is preferably 99.95 wt% or more and 99.998 wt% or less, for example. In addition, the sapphire raw material may contain Ti, Cr, Si, Ca, Mg, etc. in addition to Al and O according to the kind of the target sapphire 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.

  The particle size and density of the alumina particles are not particularly limited, but for handling, for example, the particle size is preferably 10 mm or less, and more preferably 5 mm or less.

  The shape, size, and density of the sintered body obtained by sintering the alumina powder are not particularly limited, but when filling the crucible size to be used or alumina powder in addition to the sintered body, the alumina powder and alumina to be filled simultaneously. It is preferable to select so as to increase the packing density according to the grains and the like. However, if the thickness of the sintered body is thick, volatile components such as internal moisture remain during sintering, and the purity of the raw material may be reduced. For this reason, the alumina sintered body preferably has a thickness of 10 mm or less.

Further, the density of the sapphire raw material is close to the theoretical density of α-alumina of 4 g / cm ³ , which is advantageous when filling the raw material. Therefore, the density of the sapphire raw material to be used is preferably 2 g / cm ³ or more, and more preferably 3 g / cm ³ or more.

  In the method for producing a sapphire single crystal of the present embodiment, it is preferable to use a sapphire raw material with an ignition loss (igloss) of 0.01 wt% or less, and use a sapphire raw material with an ignition loss of 0.005 wt% or less. It is more preferable.

  The ignition loss can be calculated from the change in weight before and after heating when the measurement sample is placed in a heating furnace heated up to 1000 ° C. in an air atmosphere and heated for 1 hour.

  According to the study of the inventors of the present invention, when the loss on ignition exceeds 0.01 wt%, during the heating of the sapphire raw material or during the dissolution of the sapphire raw material, The crucible may be eroded by moisture such as Japanese water, crystal water, adsorbed water or the like. This is because the erosion of the crucible causes the metal particles to be taken into the grown crystal, that is, the inclusion of the metal particles is generated, or a large amount of voids are generated below the grown crystal.

  In contrast, by setting the ignition loss of the sapphire raw material to 0.01 wt% or less, the crucible is prevented from being eroded in the raw material melt forming step, and the incorporation of the metal particles into the grown crystal is suppressed, And it becomes possible to suppress that a lot of voids arise in the growth crystal lower part.

  And the ignition loss of a sapphire raw material shall be 0.005 wt% or less, and especially it can suppress taking in to a growth crystal of metal particles, and generation of a void under the growth crystal.

  Therefore, in order to produce a sapphire single crystal with suppressed inclusion of metal particles and voids in the lower part of the grown crystal, the ignition loss is measured before starting the production of the sapphire single crystal. It is preferable to select a material having 0.01 wt% or less.

  As described above, an alumina sintered body or granular granule can be used as the sapphire raw material, but the alumina sintered body or granule has a high water content. This is because the granule uses hydrolysis and underwater spark discharge in its production stage, so that it easily contains moisture, and the sintered body has a large surface area and easily adsorbs moisture in the air. For this reason, especially when using granules or sintered bodies, the ignition loss is measured before being used in the raw material melt forming step, and a material with an ignition loss of 0.01 wt% or less is selected. It is preferable to use it.

  Moreover, in order to make ignition loss 0.01 wt% or less, the sapphire raw material previously heated in the vacuum atmosphere can also be used as the sapphire raw material used with the manufacturing method of the sapphire single crystal of this embodiment. Specifically, for example, the sapphire raw material is preferably heated in advance in a vacuum atmosphere at 500 ° C. or more for 1 hour or more, and more preferably preliminarily heated in a vacuum atmosphere at 1000 ° C. or more for 1 hour or more. This can be done by heating in advance in a vacuum atmosphere at a temperature of 500 ° C. or more for 1 hour or longer to burn off the material adhering to and / or adsorbing to the sapphire raw material and to obtain a predetermined ignition loss. This is because it can.

  The sapphire single crystal obtained by the sapphire single crystal manufacturing method of the present embodiment described above is a single crystal containing two elements of aluminum and oxygen. For example, a crystal wafer for epitaxial growth can be obtained by slicing and polishing a wafer from this single crystal.

  The sapphire single crystal obtained by the method for producing a sapphire single crystal of the present embodiment can suppress the generation of voids in the lower portion of the crystal and the incorporation of metal particle inclusions. For this reason, the electronic component material and optical component material which have the outstanding characteristic can be provided by using the wafer produced from this sapphire single crystal.

Specific examples and comparative examples will be described below, but the present invention is not limited to these examples.
[Example 1]
A sapphire single crystal was manufactured using the single crystal growth apparatus 10 shown in FIG.
(Raw material melt forming process)
In the single crystal growth apparatus 10 shown in FIG. 1, a carbon felt heat insulating material is used as the heat insulating material 16, and a carbon heater is used as the side heater 14 and the bottom heater 15. As the crucible 11, a crucible made of molybdenum having a diameter of 160 mm, a height of 160 mm, and a thickness of 2 mm was used. The thickness here refers to the thickness of the crucible 11.

  And after filling the crucible 11 with the sapphire raw material and closing the opening part of the chamber 12, the inside of the chamber 12 was made into argon atmosphere. Specifically, argon gas was flowed at a flow rate of 0.6% per minute with respect to the volume in the chamber 12 to replace the gas in the chamber 12. The argon gas was continuously supplied at the above flow rate until the grown sapphire single crystal was taken out.

Thereafter, the crucible 11 was directly heated by the side heater 14 and the bottom heater 15 at normal pressure for 20 hours or more to melt the sapphire raw material and form the raw material melt 21. After the sapphire raw material was melted, the temperature was maintained for 5 hours until the seeding step described later was performed, and the gas in the raw material melt was removed.
(Seeding process)
Next, a seeding process was performed in which the seed crystal 20 was brought into contact with the raw material melt 21 formed in the raw material melt forming process by lowering the pulling shaft 19 while rotating.
(Single crystal growth process)
After the seeding step, the temperature of the raw material melt 21 was adjusted so that the temperature was appropriate for the pulling of the crystal, and the pulling was started. The pulling speed was 1.4 mm / hour and the crystal rotation speed was 2 rpm. Thereafter, the crystal diameter was controlled to a desired diameter using an automatic diameter control device, the crystal was pulled up to a desired length, and then the grown crystal 22 was separated from the raw material melt 21 and cooled for about 15 hours.

  In the present Example, the raw material before a heating was used among the raw materials 1 shown in Table 1 as a sapphire raw material. The ignition loss of the raw material 1 before heating is 0.001 wt% as shown in Table 1.

  The loss on ignition means the rate of weight reduction before and after heating the sapphire raw material when the sapphire raw material is placed in a heating furnace preheated to 1000 ° C. in an air atmosphere and heated for 1 hour.

  Specifically, the ignition loss of the sapphire raw material was measured by the following procedure.

  First, the sapphire raw material to be measured was weighed in a platinum dish. When the sapphire raw material was weighed in a platinum dish, the mass of the sapphire raw material including the platinum dish was measured as the mass before heating (W1). Moreover, the mass (W3) of the platinum dish was also measured in advance before weighing the sapphire raw material. When measuring mass, it measured to 0.1 mg. Hereinafter, when measuring mass, it is measuring to 0.1 mg similarly.

  The temperature in the test furnace was raised to 1000 ° C. in advance.

  Next, the sapphire raw material weighed in the platinum dish was inserted into a test furnace and heated for 1 hour.

  In addition, since the temperature in a test furnace fell when putting a sapphire raw material into a test furnace, after inserting the sapphire raw material, it heated for 1 hour after the temperature in a test furnace became 1000 degreeC.

  After heating for 1 hour, the in-furnace temperature of the test furnace was lowered to 600 ° C., and the sapphire raw material was taken out from the furnace together with the platinum plate, and the heat was removed in a desiccator dried with silica gel. When the temperature dropped to room temperature, the sapphire raw material was taken out together with the platinum dish from the desiccator, and the mass of the sapphire raw material including the platinum dish was measured as the mass (W2) after heating.

  From the results measured by the above procedure, the ignition loss was calculated by the following formula.

B = (W1-W2) / (W1-W3) × 100
In the above formula, B represents ignition loss (%), W1 represents mass before heating (g), W2 represents mass after heating (g), and W3 represents mass (g) of the platinum dish.

In the following examples and comparative examples, the ignition loss was measured under the same conditions.
[Example 2]
A sapphire single crystal was produced in the same manner as in Example 1 except that the raw material 2 shown in Table 1 was used as a sapphire raw material, except that the raw material before heating was used.
[Example 3]
As a sapphire raw material, a sapphire single crystal was produced in the same manner as in Example 1 except that a raw material after heating was used among the raw materials 3 shown in Table 1.

  In addition, the raw material after the heating of the raw material 3 means the raw material after heat-processing the raw material 3 of the raw material 3 shown in Table 1 on the heating conditions (1000 degreeC, 2 hours, vacuum atmosphere) shown in Table 1. To do. As shown in Table 1, the ignition loss of the raw material 3 after heating is 0.005 wt%.

In the following examples, when it is referred to as a raw material after heating, it refers to a sapphire raw material that is heat-treated under the heating conditions shown in Table 1 for the sapphire raw material having the ignition loss shown as the raw material before heating in Table 1 for each raw material. . And the ignition loss after heating of each raw material is shown in Table 1 as a raw material after a heating.
[Example 4]
As a sapphire raw material, a sapphire single crystal was produced in the same manner as in Example 1 except that a raw material after heating was used among the raw materials 4 shown in Table 1.
[Example 5]
As a sapphire raw material, a sapphire single crystal was produced in the same manner as in Example 1 except that a raw material after heating was used among the raw materials 5 shown in Table 1.
[Example 6]
As a sapphire raw material, a sapphire single crystal was produced in the same manner as in Example 1 except that a raw material after heating was used among the raw materials 6 shown in Table 1.
[Example 7]
A sapphire single crystal was produced in the same manner as in Example 1 except that the raw material 3 shown in Table 1 was used as the sapphire raw material before heating.
[Example 8]
As a sapphire raw material, a sapphire single crystal was produced in the same manner as in Example 1 except that a raw material before heating was used among the raw materials 4 shown in Table 1.
[Comparative Example 1]
As a sapphire raw material, a sapphire single crystal was produced in the same manner as in Example 1 except that the raw material 5 before heating was used among the raw materials 5 shown in Table 1.
[Comparative Example 2]
As a sapphire raw material, a sapphire single crystal was produced in the same manner as in Example 1 except that a raw material before heating was used among the raw materials 6 shown in Table 1.

以上の各実施例および比較例で育成したサファイア単結晶について、金属粒子内包物、ボイドの有無に関しての評価と、サファイア単結晶育成後の坩堝について浸食の有無について評価を行った。
（金属粒子内包物）
金属粒子内包物は育成したサファイア単結晶をスライスしてウエハー状とした際に、ウエハー表面の突起物として観察される。

The sapphire single crystals grown in the above examples and comparative examples were evaluated for inclusion of metal particle inclusions and voids, and for the presence or absence of erosion of the crucible after sapphire single crystal growth.
(Metal particle inclusions)
The metal particle inclusions are observed as protrusions on the wafer surface when the grown sapphire single crystal is sliced into a wafer.

Therefore, in evaluating the presence / absence of the inclusion of metal particles, first, the sapphire single crystals prepared in each Example and Comparative Example were sliced and processed into a wafer shape, and then the main surface of the wafer was mirror-polished. Then, a laser beam is scanned over the mirror-finished wafer main surface, the surface irregularities are observed from the reflected light, and the case where the area occupied by the foreign matter forming the protrusion is 0.5% or less of the measurement area is 0, 0 A case of more than 5% and less than 2% was evaluated as Δ, and a case of 2% or more was evaluated as ×.
(Crystal lower void)
In evaluating the void under the crystal, first, the grown sapphire single crystal was sliced and processed into a wafer, and then the main surface of the wafer was mirror polished. The main surface of the mirror-polished wafer was evaluated by visual inspection and magnifier inspection. As a result, the case where the void generation rate was 3% or less was evaluated as ◯, the case where it was more than 3% and less than 5%, and the case where it was 5% or more were evaluated as ×.
(Crucible erosion)
Regarding the erosion of the crucible, after the sapphire single crystal was manufactured, the crucible 11 was taken out and evaluated by visually observing its inner surface. As a result of visual inspection, ◯ indicates that there was no erosion on the crucible surface, △ indicates that erosion occurred on part of the inner wall of the crucible, and erosion occurred on the entire surface of the crucible inner wall that was in contact with the raw material melt. Was evaluated as x.

  Table 2 shows the evaluation results for the sapphire single crystals obtained in the above Examples and Comparative Examples.

表２の結果から明らかなように、実施例１〜実施例６は、強熱減量が０．００５ｗｔ％以下のサファイア原料を使用したため、坩堝の浸食は発生せず、育成結晶の金属粒子内包物や、育成結晶下部のボイドの発生も十分に抑制されており、良好な結果であった。

As is apparent from the results in Table 2, since Examples 1 to 6 used a sapphire raw material with a loss on ignition of 0.005 wt% or less, no erosion of the crucible occurred, and the inclusion of metal particles in the grown crystal In addition, the generation of voids in the lower part of the grown crystal was sufficiently suppressed, and good results were obtained.

  Regarding Example 7 and Example 8, the ignition loss of the used sapphire raw material was 0.009 wt%, which was slightly higher than that of the sapphire raw material used in Examples 1 to 6. For this reason, although the void of the crystal | crystallization lower part and the inclusion of a metal particle were a little more than the case of Example 1- Example 6, it was a practical level.

  Regarding Comparative Example 1, since the ignition loss of the used sapphire raw material exceeded 0.012 wt% and 0.01 wt%, the amount of erosion of the crucible was large, and a large amount of voids were generated at the bottom of the grown crystal. The evaluation of the inclusion of the grown crystal metal particles was Δ, which was a practical level.

  Regarding Comparative Example 2, since the ignition loss of the used sapphire raw material was a very high value of 0.019 wt%, the erosion of the crucible was intense, and both the inclusion of the grown crystal in the metal particles and the large amount of voids at the bottom of the grown crystal were large. It was confirmed that this occurred.

11 Crucible 21 Raw material melt

Claims (3)

A method for producing a sapphire single crystal using a raw material melt obtained by melting a sapphire raw material filled in a crucible containing one or more kinds of metals selected from molybdenum and tungsten,
The manufacturing method of the sapphire single crystal whose ignition loss of the said sapphire raw material is 0.01 wt% or less.   The method for producing a sapphire single crystal according to claim 1, wherein the sapphire raw material is previously heated in a vacuum atmosphere at 500 ° C or higher for 1 hour or longer.   The method for producing a sapphire single crystal according to claim 1 or 2, wherein the sapphire raw material includes one or more selected from alumina powder, a sintered body of alumina powder, and alumina particles.

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