JP2019094251A - Method for manufacturing single crystal - Google Patents

Abstract

To provide a method for manufacturing a single crystal, having a high yield and capable of corresponding to increasing the size of a grown crystal.SOLUTION: The method for manufacturing a single crystal, capable of contacting a seed crystal to a raw material melt and pulling the seed crystal while rotating to grow a single crystal includes the single crystal growth step of growing the single crystal while controlling the rotational speed of the single crystal so that the bottom surface of the single crystal maintains a predetermined projection height and projects below. The single crystal growth step comprises first and second single crystal growth steps of controlling the rotational speed of the single crystal on the basis of two characteristics having different related characteristics showing a relation between the rotational speed and the projection height before and after a solidification rate solidified into the single crystal from the raw material melt and showing a weight ratio is a predetermined value.SELECTED DRAWING: Figure 4

Description

本発明は、単結晶製造方法に関する。   The present invention relates to a method of producing a single crystal.

単結晶の製造方法としては、原料を充填したルツボを加熱溶融した後に、原料融液表面から種結晶を接触させ、種結晶を上昇させながら結晶育成を行うチョクラルスキー法が広く普及している。   As a method of producing a single crystal, the Czochralski method is widely in widespread use, in which a crucible filled with a raw material is heated and melted, and then a seed crystal is brought into contact from the surface of the raw material melt and crystal growth is carried out while raising the seed crystal. .

結晶育成では、投入した原料からできるだけ長尺の単結晶を育成して固化率（投入した原料重量に対する育成された単結晶の重量比）を大きくした方が経済的である。しかし、長尺単結晶を育成すると、多結晶化しやすいという課題がある。   In crystal growth, it is more economical to grow a single crystal as long as possible from the input raw material and increase the solidification ratio (the weight ratio of the grown single crystal to the weight of the input raw material). However, there is a problem that when a long single crystal is grown, it tends to be polycrystalline.

長尺化により多結晶化が発生しやすくなる原因として、結晶内の温度差と結晶育成中の炉内温度分布の変化が考えられる。結晶内の温度差は、同一直径の結晶で比較すると、長尺化する分だけ、結晶上下の温度差が大きくなる。そのため、温度差に起因した熱ひずみが発生し、多結晶化が発生すると考えられる。また、結晶育成に伴い、結晶は上方に移動しかつ、原料融液表面位置は降下することとなる。そのため、結晶を長尺化するほど育成初期と結晶位置及び融液表面位置が乖離し、結晶育成が進行する結晶と融液の界面（固液界面）の温度環境がずれる。これにより、固液界面形状が変化し、多結晶化の起点になっていると考えられる。   Changes in the temperature difference in the crystal and the temperature distribution in the furnace during crystal growth can be considered as the causes of the tendency to cause polycrystallization due to the lengthening. The temperature difference in the crystal is larger in the temperature difference between the top and bottom of the crystal as the crystals having the same diameter are compared. Therefore, it is considered that thermal strain occurs due to the temperature difference and polycrystallization occurs. In addition, as the crystal grows, the crystal moves upward and the surface position of the raw material melt descends. Therefore, as the crystals become longer, the initial crystal position and the crystal position and the melt surface position deviate, and the temperature environment of the interface between the crystal and the melt (solid-liquid interface) where the crystal growth proceeds advances. Thereby, it is thought that the solid-liquid interface shape is changed, which is the starting point of polycrystallization.

結晶育成時の固液界面形状は重要である。結晶育成中に発生した転位は、固液界面に垂直方向に伝播する。そのため、固液界面形状が結晶側に凹形状、即ち結晶の底面が上方に窪んだ形状となると、結晶中の転位が成長とともに結晶引上げ軸方向に集積し、多結晶化現象が発生する。非特許文献１では、固液界面の形状、特に外周部の形状が結晶側に凹形状（結晶の底面が上方に窪んだ形状）かつ、その曲率中心が結晶の内側にある場合に、多結晶化することが示されている。それを解消するために、炉内の温度分布を調整し、結晶外周部に発生する凹形状の曲率中心を結晶の外側とし、結晶育成の開始から終了まで維持することで、長尺結晶を得ている。   The solid-liquid interface shape during crystal growth is important. Dislocations generated during crystal growth propagate in the direction perpendicular to the solid-liquid interface. Therefore, when the solid-liquid interface shape is concave toward the crystal, that is, the bottom of the crystal is recessed upward, dislocations in the crystal grow and accumulate in the crystal pulling axis direction, and a polycrystallization phenomenon occurs. In Non-Patent Document 1, when the shape of the solid-liquid interface, in particular, the shape of the outer peripheral portion is concave toward the crystal side (shape where the bottom of the crystal is recessed upward) and the center of curvature is inside the crystal, polycrystal Has been shown to In order to solve this, the temperature distribution in the furnace is adjusted, the concave curvature center generated in the crystal outer peripheral portion is made the outside of the crystal, and the crystal growth is maintained from the start to the end to obtain a long crystal. ing.

また、固液界面形状を維持するための方法として、特許文献１では、残融液の高さと直径の比から適切な回転数を求めることで、固化率が変化した場合にも適切な結晶回転数を決定し、固液界面を平坦かつ一定とする技術が開示されている。   In addition, as a method for maintaining the solid-liquid interface shape, Patent Document 1 determines the appropriate number of rotations from the ratio of the height of the residual liquid to the diameter of the residual melt, so that the crystal rotation is also appropriate even when the solidification rate changes. A technique for determining the number and making the solid-liquid interface flat and constant is disclosed.

特公昭６１−２９９１４号公報Japanese Examined Patent Publication No. 61-29914

Journal of Crystal Growth 128 (1993) 439-443Journal of Crystal Growth 128 (1993) 439-443

しかしながら、非特許文献１及び特許文献１に記載の方法で界面形状の維持を試みたが、実際には界面形状が変動した。非特許文献１に記載の方法では、特に、高固化率時に界面形状の変動が顕著になった。固化率が０．５程度であると従来技術により固液界面形状の制御が可能であり、歩留まりを高くすることができる。しかしながら、結晶長尺化の要請により、固化率が０．７以上の場合には、界面形状変動に起因して多結晶化が発生し、長尺単結晶の歩留まりが悪化した。   However, although the maintenance of the interface shape was attempted by the methods described in Non-Patent Document 1 and Patent Document 1, the interface shape fluctuated in practice. In the method described in Non-Patent Document 1, the variation of the interface shape becomes remarkable particularly at a high solidification rate. If the solidification rate is about 0.5, the solid-liquid interface shape can be controlled by the prior art, and the yield can be increased. However, due to the requirement of crystal lengthening, when the solidification rate is 0.7 or more, polycrystallization occurs due to interface shape fluctuation, and the yield of long single crystals is deteriorated.

また、特許文献１に記載の方法は、平坦な固液界面形状を維持する方法であり、わずかな条件の変化で、固液界面形状が結晶側に凹形状（結晶の底面が上方に窪む形状）となり、多結晶化や融液から切り離れてしまう現象が発生した。   Further, the method described in Patent Document 1 is a method of maintaining a flat solid-liquid interface shape, and the solid-liquid interface shape is concave toward the crystal side (the bottom of the crystal is recessed upward) with a slight change in conditions. And the phenomenon of being separated from polycrystallization and the melt.

そこで、本発明は、上記事情に鑑み、歩留まりが高く、育成結晶の長尺化に対応できる単結晶製造方法を提供することを目的とする。   Then, in view of the above-mentioned circumstances, an object of the present invention is to provide a single crystal manufacturing method which has a high yield and can cope with the lengthening of grown crystals.

上記目的を達成するため、本発明の一態様に係る単結晶製造方法は、原料融液に種結晶を接触させてから該種結晶を回転させながら引き上げて単結晶を育成する単結晶製造方法であって、
前記単結晶の底面が下方に所定の突出高さを維持して突出するように前記単結晶の回転速度を制御しながら前記単結晶を育成する単結晶育成工程を有し、
該単結晶育成工程は、前記原料融液から前記単結晶に固化した重量比率を示す固化率が所定の値となった前後において、前記回転速度と前記突出高さとの関係を示す関係特性が異なる２つの特性に基づいて前記単結晶の回転速度を制御する第１及び第２の単結晶育成工程を含む。 In order to achieve the above object, a single crystal production method according to an aspect of the present invention is a single crystal production method in which a seed crystal is brought into contact with a raw material melt and then pulled while rotating the seed crystal to grow a single crystal. There,
And a single crystal growing step of growing the single crystal while controlling the rotational speed of the single crystal such that the bottom surface of the single crystal protrudes downward while maintaining a predetermined protruding height.
In the single crystal growing step, the relationship characteristic indicating the relationship between the rotational speed and the protrusion height is different before and after the solidification ratio indicating the weight ratio of the raw material melt solidified to the single crystal becomes a predetermined value. The method includes first and second single crystal growing steps of controlling the rotation speed of the single crystal based on two characteristics.

本発明の一態様によれば、低コストで歩留まりが高く、育成結晶の長尺化に対応できる単結晶製造方法を提供することができる。   According to one aspect of the present invention, it is possible to provide a method for producing a single crystal which is low in cost, has a high yield, and can cope with the lengthening of grown crystals.

本発明の実施形態に係る結晶育成装置の一例を示した概要図である。FIG. 1 is a schematic view showing an example of a crystal growth apparatus according to an embodiment of the present invention. 単結晶と原料融液との間の固液界面形状の例を示した図である。It is a figure showing an example of solid-liquid interface shape between a single crystal and a raw material melt. 固化率０．７以上の結晶育成を行った結果を示した図である。It is the figure which showed the result of having performed crystal growth of solidification rate 0.7 or more. 固化率が所定値以上の場合の単結晶の回転速度と底面の突出高さとの関係を示した図である。It is the figure which showed the relationship between the rotational speed of the single crystal in case the solidification rate is more than predetermined value, and the protrusion height of a bottom face. 固化率が所定値未満の場合の単結晶の回転速度と底面の突出高さとの関係を示した図である。It is the figure which showed the relationship between the rotational speed of the single crystal in case a solidification rate is less than predetermined value, and the protrusion height of the bottom face.

以下、図面を参照して、本発明を実施するための形態の説明を行う。   Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

チョクラルスキー法は、ある結晶方位に従って切り出された種結晶と呼ばれる単結晶の先端を、原料融液に接触させ、回転しながら徐々に引上げることによって、種結晶の性質を伝播しながら大口径化して単結晶を製造する方法である。   In the Czochralski method, the tip of a single crystal called a seed crystal cut out according to a certain crystal orientation is brought into contact with the raw material melt, and pulled gradually while rotating, thereby propagating the properties of the seed crystal while large diameter Method to produce a single crystal.

図１は、本発明の実施形態に係る結晶育成装置の一例を示した概要図である。図１に示されるように、本実施形態に係る結晶育成装置は、ルツボ１０と、支持台２０と、耐火物３０と、高周波誘導コイル４０と、引き上げ軸５０と、を備える。そして、ルツボ１０、耐火物３０及び高周波誘導コイル４０を含めた全体を、チャンバー６０が覆っている。高周波誘導コイル４０は、ルツボ１０を加熱する加熱手段である。また、更にチャンバー６０の外側には、高周波誘導コイル４０に高周波電力を供給するために電源７０と、結晶育成装置の全体の動作を制御する制御部８０が設けられている。また、ルツボ１０内には原料融液９０が貯留されており、引上げ軸５０の下端には、種結晶１００が保持されている。更に、引上げ軸５０の上部には、引上げ軸５０を回転させる回転機構としてモーター５１が設けられ、図示されていないが、モーター５１とほぼ同じ位置に、単結晶の重量を測定するロードセルが設けられている。   FIG. 1 is a schematic view showing an example of a crystal growth apparatus according to an embodiment of the present invention. As shown in FIG. 1, the crystal growth apparatus according to the present embodiment includes a crucible 10, a support 20, a refractory 30, a high frequency induction coil 40, and a pulling shaft 50. And the chamber 60 covers the whole including the crucible 10, the refractory 30, and the high frequency induction coil 40. The high frequency induction coil 40 is a heating means for heating the crucible 10. Furthermore, outside the chamber 60, a power supply 70 for supplying high frequency power to the high frequency induction coil 40 and a control unit 80 for controlling the overall operation of the crystal growth apparatus are provided. The raw material melt 90 is stored in the crucible 10, and the seed crystal 100 is held at the lower end of the pulling shaft 50. Furthermore, a motor 51 is provided above the pulling shaft 50 as a rotating mechanism for rotating the pulling shaft 50, and although not shown, a load cell for measuring the weight of a single crystal is provided at substantially the same position as the motor 51. ing.

次に、個々の構成要素について説明する。   Next, individual components will be described.

ルツボ１０は、原料融液９０を貯留保持し、単結晶を育成するための容器である。結晶原料は、結晶化する金属等が溶融した原料融液９０の状態で保持される。ルツボ１０の材質は、結晶原料の種類にもよるが、例えば、耐熱性のある白金やイリジウム等で作製される。   The crucible 10 is a container for storing the raw material melt 90 and growing a single crystal. The crystal raw material is held in the state of the raw material melt 90 in which the metal or the like to be crystallized is melted. The material of the crucible 10 is made of, for example, heat-resistant platinum or iridium although it depends on the kind of crystal raw material.

支持台２０は、ルツボ１０を下方から支持する載置台として設けられる。支持台２０は、高周波誘導コイル４０の加熱に耐え得る十分な耐熱性及びルツボ１０を支持する耐久性を有すれば、種々の材料から構成されてよい。図１に示される通り、支持台２０は、ルツボ１０の他、耐火物３０も支持するように構成されてもよい。   The support table 20 is provided as a mounting table for supporting the crucible 10 from below. The support 20 may be made of various materials as long as it has sufficient heat resistance to withstand the heating of the high frequency induction coil 40 and durability to support the crucible 10. As shown in FIG. 1, the support 20 may be configured to support the refractory 30 as well as the crucible 10.

耐火物３０は、ルツボ１０の高周波誘導コイル４０による発熱を内部に保持し、外部への放出を防ぐ役割を果たす。耐火物３０は、耐熱性の高い材料で構成される。よって、耐火物３０は、ルツボ１０を取り囲むように設けられる。耐火物３０も、支持台２０上に載置されて設けられてよい。また、耐火物３０は、天井面に開口３１を有し、引き上げ軸５０を挿入可能に構成される。   The refractory 30 holds the heat generated by the high frequency induction coil 40 of the crucible 10 internally, and plays a role in preventing the release to the outside. The refractory 30 is made of a material having high heat resistance. Thus, the refractory 30 is provided to surround the crucible 10. The refractory 30 may also be mounted on the support 20. Moreover, the refractory 30 has the opening 31 in a ceiling surface, and is comprised so that insertion of the pulling-up axis | shaft 50 is possible.

高周波誘導コイル４０は、ルツボ１０を誘導加熱するための手段であり、ルツボ１０及び耐火物３０の周囲を囲むように配置される。高周波誘導コイル４０は、ルツボ１０を誘導加熱できればその種類や形態は問わない。誘導加熱コイル４０は、交流電流によりルツボ１０に渦電流を発生させ、そのジュール熱でルツボ１０を加熱する。   The high frequency induction coil 40 is a means for inductively heating the crucible 10, and is disposed to surround the crucible 10 and the refractory 30. The type and the form of the high frequency induction coil 40 are not limited as long as the crucible 10 can be inductively heated. The induction heating coil 40 generates an eddy current in the crucible 10 by an alternating current, and heats the crucible 10 by the Joule heat.

電源７０は、高周波誘導コイル４０に高周波電力を供給する高周波電源として構成される。電源８０は、高周波誘導コイル４０のみならず、結晶育成装置全体に電源供給を行う。   The power supply 70 is configured as a high frequency power supply that supplies high frequency power to the high frequency induction coil 40. The power supply 80 supplies power not only to the high frequency induction coil 40 but also to the entire crystal growth apparatus.

引き上げ軸５０は、種結晶１００を保持し、ルツボ１０に貯留された原料融液９０の表面に種結晶１００を接触させ、回転しながら単結晶を引き上げるための手段である。引き上げ軸５０は、種結晶１００を下端部に保持するとともに、回転機構であるモーター５１を備える。なお、モーター５１は、単結晶の引き上げの際、単結晶を回転させながら引き上げる動作を行うための回転駆動機構である。また、上述のように、モーター５１とほぼ同じ位置に、単結晶の重量を計測するロードセル（図示せず）が設けられている。   The pulling shaft 50 is a means for holding the seed crystal 100, bringing the seed crystal 100 into contact with the surface of the raw material melt 90 stored in the crucible 10, and pulling the single crystal while rotating. The pulling shaft 50 holds the seed crystal 100 at the lower end, and includes a motor 51 which is a rotation mechanism. The motor 51 is a rotational drive mechanism for performing an operation of pulling up the single crystal while rotating the single crystal when pulling up the single crystal. Further, as described above, a load cell (not shown) for measuring the weight of the single crystal is provided at substantially the same position as the motor 51.

チャンバー６０は、ルツボ１０及び高周波誘導コイル４０の高熱を遮断するとともに、これらを収容し、内部の雰囲気を保持する機能を有する。チャンバー６０は、熱を外部に逃さないため、図示しない水冷ジャケットが壁面の内部に設けられており、水冷ジャケットを水が循環することにより冷却される。   The chamber 60 has a function of blocking the high heat of the crucible 10 and the high frequency induction coil 40, accommodating the same, and maintaining the internal atmosphere. In order to prevent heat from being dissipated to the outside, the chamber 60 is provided with a water cooling jacket (not shown) inside the wall and is cooled by circulating water through the water cooling jacket.

制御部８０は、結晶育成装置全体の制御を行うための手段であり、結晶育成プロセスを含めて結晶育成装置全体の動作を制御する。制御手段は、例えば、ＣＰＵ（Central Processing Unit、中央処理装置、及びＲＯＭ（Read Only Memory）、ＲＡＭ（Random Access Memory）等のメモリを備え、プログラムにより動作するマイクロコンピュータから構成されてもよいし、特定の用途のために開発されたＡＳＩＣ（Application Specified Integra Circuit）等の電子回路から構成されてもよい。   The control unit 80 is a means for controlling the entire crystal growth apparatus, and controls the operation of the entire crystal growth apparatus including the crystal growth process. The control means may be constituted by a microcomputer operated by a program, for example, including a memory such as a central processing unit (CPU), a central processing unit, and a read only memory (ROM) and a random access memory (RAM). It may be comprised of an electronic circuit such as an Application Specified Integra Circuit (ASIC) developed for a specific application.

なお、制御部８０は、引上げ軸５０の回転速度を制御してもよい。例えば、モーター５１の回転速度を制御することにより、引上げ軸５０の回転速度を制御し、種結晶１００及び単結晶の回転速度を制御することができる。   The control unit 80 may control the rotational speed of the pulling shaft 50. For example, by controlling the rotation speed of the motor 51, the rotation speed of the pulling shaft 50 can be controlled, and the rotation speeds of the seed crystal 100 and the single crystal can be controlled.

本実施形態に係る結晶育成装置は、種々の結晶原料に適用することができ、結晶原料の種類は問わないが、例えば、タンタル酸リチウム原料を用いてもよい。その他、種々の酸化物単結晶を育成するための結晶原料を用いることができる。   The crystal growth apparatus according to the present embodiment can be applied to various crystal raw materials, and there is no limitation on the type of the crystal raw material. For example, a lithium tantalate raw material may be used. In addition, crystal raw materials for growing various oxide single crystals can be used.

次に、単結晶の製造方法の全体的な流れについて説明する。   Next, the entire flow of the method of manufacturing a single crystal will be described.

単結晶の製造では、単結晶原料を充填したルツボ１０を、高周波誘導コイル４０を用いた高周波誘導加熱により加熱させ、原料融液９０を得る。その後、引上げ軸５０の下端に保持された種結晶１００を回転させながら原料融液９０の表面に接触させ、種結晶１００を引上げ軸５０で回転させながら引き上げ、単結晶の製造を行う。結晶育成方法は特に限定されず、公知の技術が利用できる。   In the production of a single crystal, a crucible 10 filled with a single crystal raw material is heated by high frequency induction heating using a high frequency induction coil 40 to obtain a raw material melt 90. Thereafter, the seed crystal 100 held at the lower end of the pulling shaft 50 is brought into contact with the surface of the raw material melt 90 while being rotated, and the seed crystal 100 is pulled while being rotated by the pulling shaft 50 to produce a single crystal. The crystal growth method is not particularly limited, and known techniques can be used.

次に、本実施形態に係る単結晶製造方法において実施する制御方法について説明する。   Next, a control method implemented in the method of manufacturing a single crystal according to the present embodiment will be described.

結晶直径制御の手段として、上述のロードセルを用いて重量変化量を計測し、この重量変化量をもとに直径を計算している（演算直径）。この演算直径と目標直径を比較し、投入出力を調整することで、所望の結晶形状を得ている。この演算直径を計算する場合に、固液界面形状は一定の形状と仮定している。そのため、固液界面形状の変化により生じる重量変化も演算直径に反映される。よって、演算直径が一定であっても固液界面形状が変動した場合には、得られる結晶の直径が一定とならない。   As a means of crystal diameter control, the weight change amount is measured using the above-mentioned load cell, and the diameter is calculated based on this weight change amount (calculated diameter). A desired crystal shape is obtained by comparing the calculated diameter with the target diameter and adjusting the input output. When calculating this operation diameter, the solid-liquid interface shape is assumed to be a constant shape. Therefore, the change in weight caused by the change in the solid-liquid interface shape is also reflected in the calculated diameter. Therefore, even if the calculated diameter is constant, when the solid-liquid interface shape changes, the diameter of the obtained crystal does not become constant.

固液界面形状が変動することにより、得られた単結晶に直径変動が生じる。この直径変動によりウエハ切断時の歩留まりの低下が発生する。また、固液界面形状が変動し、部分的であっても結晶側に凹形状となり、単結晶の底面が窪んだ形状となった場合には、転位の集積による多結晶化発生のリスクが高まる。そのため、結晶育成開始から終了までは単結晶の底面を下方に略円錐状に突出させ、固液界面形状を融液側に凸形状とし、一定に保つことが理想である。   Fluctuation in the solid-liquid interface shape causes diameter fluctuation in the obtained single crystal. The variation in diameter causes a reduction in yield at the time of wafer cutting. In addition, the shape of the solid-liquid interface fluctuates, and even if it is partial, it becomes concave on the crystal side, and when the bottom of the single crystal is recessed, the risk of occurrence of polycrystallization due to dislocation accumulation increases. . Therefore, from the crystal growth start to the end, it is ideal that the bottom surface of the single crystal protrudes downward in a substantially conical shape, and the solid-liquid interface shape is convex on the melt side and kept constant.

図２は、単結晶と原料融液９０との間の固液界面形状の例を示した図である。図２（ａ）に示されるように、原料融液９０（以下、単に「融液９０」と呼んでもよいこととする。）と単結晶１１０との界面は、種々の形状となり得る。図２（ｂ）に示されるように、単結晶１１０の底面が下に突出するような形状が好ましい。図２（ｃ）に示されるような単結晶１１０の底面が上方に窪んだ形状は、多結晶化のリスクが高まり、好ましくない形状と言える。   FIG. 2 is a view showing an example of the solid-liquid interface shape between the single crystal and the raw material melt 90. As shown in FIG. 2A, the interface between the raw material melt 90 (hereinafter simply referred to as "melt 90") and the single crystal 110 can have various shapes. As shown in FIG. 2 (b), a shape in which the bottom of the single crystal 110 protrudes downward is preferable. The shape in which the bottom surface of the single crystal 110 is recessed upward as shown in FIG. 2C increases the risk of polycrystallization and can be said to be an undesirable shape.

なお、凸形状及び凹形状の限定は特に無いが、凸形状及び凹形状の双方とも円錐形状に近似した形状となり、中心部が最も大きく突出するか又は窪み、テーパー形状をなすように凸形状及び凹形状が形成される。   Although there is no particular limitation on the convex shape and the concave shape, both the convex shape and the concave shape are similar to a conical shape, and the central portion projects most greatly or is a convex shape so as to form a recess or a tapered shape. A concave shape is formed.

固液界面形状は、融液９０内の温度分布を反映しており、等温線の形状となると考えられる。そのため、固液界面形状を一定とするためには、育成開始から終了まで融液９０内の固液界面近傍の温度分布を一定にすることが望まれる。しかし、結晶育成に伴い育成単結晶１１０（以下、単に「結晶１１０」と呼んでもよいこととする。）は上方に移動しかつ、融液９０の表面位置は低下する。このような炉内の変化により融液内温度分布が変化し、固液界面形状も変化してしまう。   The solid-liquid interface shape reflects the temperature distribution in the melt 90, and is considered to be an isotherm shape. Therefore, in order to make the solid-liquid interface shape constant, it is desirable to make the temperature distribution in the vicinity of the solid-liquid interface in the melt 90 constant from the start to the end of the growth. However, along with crystal growth, the grown single crystal 110 (hereinafter, simply referred to as "crystal 110") moves upward, and the surface position of the melt 90 decreases. Such a change in the furnace changes the temperature distribution in the melt and also changes the shape of the solid-liquid interface.

融液９０内には、ルツボ壁で加熱された融液が温度差（密度差）に起因してルツボ壁から結晶１１０に向かって流れる自然対流が存在する。また、融液９０と接触した結晶１１０を回転することにより、強制対流が発生する。強制対流は、結晶１１０の回転につられて回りながら自然対流と逆向きに流れる対流である。強制対流は、結晶１１０の回転数（回転速度）に比例して大きくなる。この強制対流の大きさを結晶回転数（結晶回転速度）により制御することで固液界面近傍の融液温度分布を変化させて、固液界面形状を制御することが可能となる。強制対流が大きい状態では、ルツボ１０の下方及び径方向へ強制対流の領域が広がり、固液界面近傍と比較して温度の高い融液９０が固液界面に移動することになる。そのため、固液界面形状は、融液９０側に凸状（結晶１１０の底面が突出）の場合には、その高さが減少する。さらに強制対流が大きくなると結晶側に凹形状（結晶１１０の底面中央部が上方に窪む）の固液界面形状へと変化する。   In the melt 90, there is a natural convection in which the melt heated by the crucible wall flows from the crucible wall toward the crystal 110 due to the temperature difference (density difference). Also, by rotating the crystal 110 in contact with the melt 90, forced convection occurs. Forced convection is convection that flows in the opposite direction of natural convection as it is rotated as the crystal 110 rotates. The forced convection increases in proportion to the number of rotations (rotational speed) of the crystal 110. By controlling the magnitude of this forced convection with the crystal rotation number (crystal rotation speed), it becomes possible to change the melt temperature distribution in the vicinity of the solid-liquid interface and to control the solid-liquid interface shape. In a state where the forced convection is large, the area of the forced convection spreads downward and in the radial direction of the crucible 10, and the melt 90 whose temperature is higher than that near the solid-liquid interface moves to the solid-liquid interface. Therefore, in the case where the solid-liquid interface shape is convex toward the melt 90 (the bottom of the crystal 110 protrudes), the height thereof decreases. Furthermore, when the forced convection becomes large, it changes to a solid-liquid interface shape having a concave shape (the central portion of the bottom of the crystal 110 is recessed upward) on the crystal side.

つまり、自然対流と強制対流のバランスを維持し、固液界面近傍の融液温度分布を一定に保つことが固液界面形状を一定に維持するために必要であると考えられる。仮に、育成開始から終了までに同じ結晶回転数（結晶回転速度）で結晶育成を行うと、融液高さ減少に伴い自然対流が小さくなるため、強制対流の影響が徐々に大きくなる。その場合、育成開始時に結晶１１０が融液９０側に凸状であれば、その凸部の高さ（結晶１１０の底面を基準として下方に延びる凸部の高さ、又は鉛直方向における凸部の長さを意味し、以後、「突出高さ」とも呼ぶ）が結晶育成とともに減少して行くことになる。このため、固液界面形状の変化に伴う結晶直径の変動や固液界面の部分的な凹形状化に起因した多結晶化が発生しやすくなる。そこで、融液高さ低下に伴う自然対流の変化に合わせて、結晶回転数（結晶回転速度）を減少させて、強制対流の影響により凸部の高さが小さくなることを抑えながら固液界面形状を維持することを行っていた。しかし、この方法により固化率０．７以上の結晶育成を行ったところ、固液界面形状（凸部の高さ）を維持できなかった。そこで、固化率０．７以上の結晶育成で、固液界面形状の融液側に凸状になった凸部の高さと結晶回転数について調査を行った。その結果、従来と逆の結果となった。つまり、固液界面形状の融液側に凸状になった凸部の高さを減少させるために、結晶回転数を大きくしたところ凸部の高さが高くなる現象が見られた。結晶回転数を小さくしたところ、凸部の高さが低くなった。   That is, it is considered that maintaining the balance between natural convection and forced convection and keeping the melt temperature distribution in the vicinity of the solid-liquid interface constant is necessary to maintain the solid-liquid interface shape constant. If crystal growth is performed at the same crystal rotational speed (crystal rotation speed) from the start to the end of growth, natural convection decreases as the melt height decreases, so the influence of forced convection gradually increases. In that case, if the crystal 110 is convex toward the melt 90 at the start of growth, the height of the convex (the height of the convex extending downward with reference to the bottom of the crystal 110, or the convex in the vertical direction This means the length, and hereinafter also referred to as the “projecting height”) will decrease with the crystal growth. For this reason, the polycrystallisation resulting from the fluctuation | variation of the crystal diameter accompanying the change of solid-liquid interface shape and the partial concave shape formation of a solid-liquid interface becomes easy to generate | occur | produce. Therefore, the crystal rotation number (crystal rotation speed) is reduced according to the change in natural convection due to the decrease in melt height, and the solid-liquid interface is suppressed while suppressing the reduction in height of the convex portion due to the effect of forced convection. I was going to maintain the shape. However, when crystal growth with a solidification rate of 0.7 or more was performed by this method, the solid-liquid interface shape (height of the convex portion) could not be maintained. Therefore, the height and crystal rotation number of the convex portion convex to the melt side of the solid-liquid interface shape were investigated by crystal growth with a solidification rate of 0.7 or more. As a result, the result is the reverse of the conventional one. That is, in order to reduce the height of the convex portion convex toward the melt side of the solid-liquid interface shape, a phenomenon was observed in which the height of the convex portion increased as the number of crystal rotations was increased. When the number of crystal rotations was reduced, the height of the projections decreased.

図３は、固化率０．７以上の結晶育成を行った結果を示した図である。図３は、直径１００ｍｍのタンタル酸リチウム結晶を固化率０．７５の状態で得たデータである。結晶回転数（結晶回転速度、ｒｐｍ）と固液界面形状の凸部の高さ（下方への突出高さ）に相関がみられることから、強制対流と固液界面形状の相関と読み取ることも出来る。例えば結晶直径を１５０ｍｍとした場合には、結晶径増大により強制対流の影響が大きくなると考えられる。よって、図３で得られた直線の傾きが大きくなり、結晶回転数の影響が大きくなると推察される。   FIG. 3 is a view showing the results of crystal growth with a solidification rate of 0.7 or more. FIG. 3 shows data obtained from a lithium tantalate crystal with a diameter of 100 mm at a solidification rate of 0.75. Since there is a correlation between the crystal rotation speed (crystal rotation speed, rpm) and the height of the convex part of the solid-liquid interface shape (projecting height downward), it is also possible to read the correlation between forced convection and solid-liquid interface shape It can. For example, in the case where the crystal diameter is 150 mm, it is considered that the influence of forced convection is increased by the increase in crystal diameter. Therefore, it is presumed that the inclination of the straight line obtained in FIG. 3 becomes large, and the influence of the crystal rotation number becomes large.

また、固化率がさらに上昇した場合には、融液高さの減少により、自然対流の影響が小さくなり、同一の結晶回転数であっても相対的に強制対流の影響が大きくな。この場合にも、図３で得られた直線の傾きが大きくなり、結晶回転数の影響が大きくなる。   In addition, when the solidification rate further increases, the influence of natural convection becomes small due to the decrease of the melt height, and the influence of forced convection becomes relatively large even at the same crystal rotation number. Also in this case, the slope of the straight line obtained in FIG. 3 becomes large, and the influence of the crystal rotation number becomes large.

いずれの場合においても、図３と同様な結晶回転数と固液界面の凸部の高さ（下方への突出高さ）の関係を調査することで、所望の固液界面形状を得るための結晶回転数を容易に求めることが可能である。   In any case, the desired solid-liquid interface shape can be obtained by investigating the relationship between the number of crystal rotations and the height of the convex portion at the solid-liquid interface (the downward protrusion height) as in FIG. It is possible to easily determine the crystal rotation number.

固化率が０．７よりも小さく、残融液高さが十分である場合、強制対流は、育成結晶１１０の固液界面下方からルツボ壁に向かう流れとなる。そのため、強制対流が強い（結晶回転数が大きい）条件下の固液界面近傍は、下方から温度が高い融液９０が輸送され温度が上昇し、凸部の高さが減少する。   When the solidification rate is smaller than 0.7 and the residual liquid height is sufficient, forced convection flows from below the solid-liquid interface of the grown crystal 110 toward the crucible wall. Therefore, in the vicinity of the solid-liquid interface under strong forced convection (high crystal rotation speed) conditions, the melt 90 having a high temperature is transported from below to raise the temperature, and the height of the convex portion decreases.

一方、固化率０．７以上の場合には、残融液高さが低い状態にある。この場合にも、結晶回転により強制対流が発生する。しかし、残融液高さが小さい場合の強制対流は、結晶回転に沿ってのみ発生する。そのため、固液界面下方から温度の高い融液９０がルツボ壁に輸送されることは無い。また、結晶１１０に沿って周回しながらルツボ１０の下方へ融液９０が流れるため、融液９０は固液界面近傍で冷却され、ルツボ１０の底部に流れる。そのため、固液界面の凸部下方の温度が低下し、結晶１１０は下方へ成長しやすくなり、凸部の高さが高くなりやすい。この様な下方への結晶成長は、強制対流が強い（結晶回転数が大きい）場合に促進される。その結果、固化率が０．７以上の場合には、固液界面の凸部の高さは結晶回転数に比例することになる。そのため、結晶回転数が大きすぎる場合には、凸部の高さが高くなりすぎて、最終的には残融液の高さと等しくなると、ルツボ底部と接触し結晶育成の継続が出来なくなる。   On the other hand, when the solidification rate is 0.7 or more, the residual melt height is low. Also in this case, forced convection occurs due to crystal rotation. However, forced convection when the retentate height is small occurs only along the crystal rotation. Therefore, the melt 90 having a high temperature from below the solid-liquid interface is not transported to the crucible wall. Further, since the melt 90 flows downward to the crucible 10 while circulating along the crystal 110, the melt 90 is cooled near the solid-liquid interface and flows to the bottom of the crucible 10. Therefore, the temperature below the convex part at the solid-liquid interface decreases, and the crystal 110 is easily grown downward, and the height of the convex part tends to be high. Such downward crystal growth is promoted when forced convection is strong (crystal rotation number is large). As a result, when the solidification rate is 0.7 or more, the height of the convex portion at the solid-liquid interface is proportional to the crystal rotation number. Therefore, when the crystal rotation number is too large, the height of the convex portion becomes too high, and eventually, when the height of the residual liquid is equal, the bottom of the crucible contacts and the crystal growth can not be continued.

また、固化率が０．７以上の場合には、残融液高さが低く、結晶先端部とルツボ底部の距離が近づく。ルツボ底部は、ルツボ１０を支える支持台２０からの放熱があるため、温度が低くなりやすい。そのため、固化率が高い状態では、固液界面の凸部高さが高くなりやすい傾向にある。仮に、結晶回転数を同一とした場合には、上述の理由により固化率が上昇すると凸部の高さが高くなる傾向にある。さらに、結晶回転による強制対流の影響を受けることで、前記のように高固化率の状態では、結晶回転数の増加により結晶下部の融液温度が低下し、凸部の高さは高くなりやすい傾向であった。   When the solidification rate is 0.7 or more, the height of the residual liquid is low, and the distance between the crystal front end and the crucible bottom approaches. The temperature at the bottom of the crucible tends to be low because there is heat radiation from the support 20 supporting the crucible 10. Therefore, in the state where the solidification rate is high, the height of the convex portion at the solid-liquid interface tends to be high. If the number of crystal rotations is the same, if the solidification rate increases due to the above-mentioned reason, the height of the projections tends to increase. Furthermore, under the influence of forced convection due to crystal rotation, the melt temperature in the lower part of the crystal is lowered due to the increase of the crystal rotation number in the state of high solidification rate as described above, and the height of the convex portion tends to be high. It was a trend.

すなわち、固化率が小さく、融液高さが高い状態では、固液界面の凸部の高さと結晶回転数は反比例の関係にあるが、固化率が０．７以上の状態ではその関係は比例の関係にあることが分かった。そこで、固液界面形状の凸部の高さＨ（突出高さ）と結晶回転数ωの関係を次式（１）により求め、高固化率の状態で固液界面形状を制御する必要がある。   That is, when the solidification ratio is small and the melt height is high, the height of the convex portion at the solid-liquid interface is in inverse proportion to the crystal rotation number, but when the solidification ratio is 0.7 or more, the relationship is proportional It turned out that it is in relation. Therefore, it is necessary to obtain the relationship between the height H (protruding height) of the convex part of the solid-liquid interface shape and the crystal rotational speed ω by the following equation (1) to control the solid-liquid interface shape in a high solidification rate state .

Ｈ＝ａω＋ｂ・・・（１）
ここで、ａ、ｂは実験により求められる定数であり、０＜ａである。 H = aω + b (1)
Here, a and b are constants obtained by experiments, and 0 <a.

図４に、（１）式をグラフ化した図を示す。即ち、図４は、固化率が所定位置以上、例えば固化率が０．７以上の場合の単結晶の回転速度と底面の突出高さ（凸部高さＨ）との関係を示した図である。   FIG. 4 shows a graph of the equation (1). That is, FIG. 4 is a view showing the relationship between the rotational speed of the single crystal and the protruding height of the bottom surface (convex height H) when the solidification rate is equal to or higher than a predetermined position, for example, the solidification rate is 0.7 or higher. is there.

図４に示される通り、固化率が大きくなり、例えば０．７以上の場合には、（１）式を満たす関係にあり、結晶１１０の回転速度が高くなる程、結晶１１０の底面の下方への突出高さが増加する。よって、突出高さを所定の値、例えば１０〜２０ｍｍの間の所定値に維持したい場合には、回転速度を徐々に遅くする制御を行うことになる。   As shown in FIG. 4, the solidification ratio increases, and for example, in the case of 0.7 or more, the relationship is satisfied with equation (1), and the lower the bottom of crystal 110 as the rotation speed of crystal 110 increases. The protrusion height of is increased. Therefore, in order to maintain the projection height at a predetermined value, for example, a predetermined value between 10 and 20 mm, control is performed to gradually reduce the rotational speed.

図５は、固化率が所定値未満、例えば０．７未満の場合の結晶１１０の回転速度と底面の突出高さ（凸部高さＨ）との関係を示した図である。固化率が所定値未満の場合には、下記の（２）式を満たす関係にある。   FIG. 5 is a view showing the relationship between the rotational speed of the crystal 110 and the protruding height of the bottom surface (convex height H) when the solidification rate is less than a predetermined value, for example, less than 0.7. If the solidification rate is less than the predetermined value, the relationship (2) below is satisfied.

Ｈ＝ｃ／ω＋ｄ・・・（２）
ここで、ｃ、ｄは実験により求められる定数であり、０＜ｃである。 H = c / ω + d (2)
Here, c and d are constants obtained by experiments, and 0 <c.

図５に示されるように、固化率が０．７未満のときには、単結晶１１０の底面の突出高さは、単結晶１１０の回転速度に反比例する。つまり、回転速度を高くすると、単結晶１１０の底面が上方に窪んでゆく傾向があるので、徐々に回転速度を低くする制御を行うことにより、単結晶１１０の底面の突出高さを一定の値に保つことができる。   As shown in FIG. 5, when the solidification rate is less than 0.7, the protrusion height of the bottom of the single crystal 110 is inversely proportional to the rotation speed of the single crystal 110. That is, when the rotational speed is increased, the bottom surface of the single crystal 110 tends to be recessed upward. Therefore, the protrusion height of the bottom surface of the single crystal 110 is set to a constant value by performing control to gradually reduce the rotational speed. You can keep

このように、本実施形態に係る単結晶製造方法では、所定の固化率の前後において、単結晶１１０の回転速度と単結晶１１０の底面の下方突出高さとの関係特性が異なる２つの特性を用いて、引上げ軸５０及び単結晶１１０の回転速度の制御を行う。即ち、固化率が所定値未満のときには、単結晶１１０の回転速度と単結晶１１０の底面の下方突出高さとの関係特性が反比例の関係にある特性（図５）に基づいて回転速度の制御を行い、固化率が所定値以上のときには、単結晶１１０の回転速度と単結晶１１０の底面の下方突出高さとの関係特性が比例関係にある特性（図４）に基づいて回転速度の制御を行う。このような２段階の回転速度制御を採用することにより、単結晶１１０の底面の突出高さを一定とし、多結晶化を防ぎつつ単結晶１１０の長尺化を達成することができる。   As described above, in the single crystal manufacturing method according to the present embodiment, two characteristics having different relationship characteristics between the rotation speed of the single crystal 110 and the downward protruding height of the bottom surface of the single crystal 110 are used before and after the predetermined solidification ratio. Then, control of the rotational speed of the pulling shaft 50 and the single crystal 110 is performed. That is, when the solidification rate is less than the predetermined value, the control of the rotational speed is performed based on the characteristic (FIG. 5) in which the relationship between the rotational speed of the single crystal 110 and the downward protruding height of the bottom of the single crystal 110 is inversely proportional. If the solidification rate is equal to or higher than the predetermined value, the rotational speed is controlled based on the characteristic (FIG. 4) in which the relationship between the rotational speed of the single crystal 110 and the downward protruding height of the bottom of the single crystal 110 is proportional. . By adopting such two-step rotational speed control, the protrusion height of the bottom surface of the single crystal 110 can be made constant, and enlargement of the single crystal 110 can be achieved while preventing polycrystallization.

なお、本実施形態に係る単結晶製造方法は、固化率が０．７以上の所定値である場合に好適に適用可能であるが、製造プロセスの条件により種々変化し、０．６以上の所定値であれば適用できる場合もある。所定値となる固化率の上限は特に限定されないが、固化率が０．６以上０．９５以下の所定値、好ましくは０．７以上０．９５以下の範囲の固化率に好適に適用することができる。   In addition, although the single crystal manufacturing method which concerns on this embodiment is suitably applicable when a solidification rate is predetermined value or more of 0.7, it changes variously with the conditions of a manufacturing process, and the predetermined | prescribed value of 0.6 or more It may be applicable if it is a value. The upper limit of the solidification ratio to be a predetermined value is not particularly limited, but the solidification ratio is suitably applied to a predetermined value of 0.6 or more and 0.95 or less, preferably 0.7 or more and 0.95 or less. Can.

また、回転速度は、上述のように、制御部８０がモーター５２を制御することにより制御してよい。また、原料融液９０の固化率は、上述のように、ロードセルで単結晶１１０の重量を測定し、計算により求めることができる。   Also, the rotational speed may be controlled by the control unit 80 controlling the motor 52 as described above. Further, as described above, the solidification rate of the raw material melt 90 can be obtained by calculation by measuring the weight of the single crystal 110 with a load cell.

次に、本実施形態に係る単結晶製造方法を実施した実施例について説明する。   Next, an example in which the method for producing a single crystal according to the present embodiment is implemented will be described.

以下、本発明の実施例について比較例を挙げて具体的に説明する。以下の説明では、一例としてタンタル酸リチウム単結晶育成方法について説明する。また、理解の容易のため、図１で説明した結晶育成装置の構成要素に対応する構成要素には、同一の参照符号を付して説明する。   Hereinafter, examples of the present invention will be specifically described with reference to comparative examples. In the following description, a lithium tantalate single crystal growth method will be described as an example. Further, in order to facilitate understanding, the same reference numerals are assigned to components corresponding to the components of the crystal growth apparatus described in FIG.

イリジウム製のルツボ１０にタンタル酸リチウムの原料が充填され、ルツボ１０を銅製の高周波誘導コイル４０によって加熱する。ルツボ１０内のタンタル酸リチウム原料を融解させて原料融液９０とした。そして、イリジウム製の引上げ軸５０の下端に保持した種結晶１００を原料融液９０に接触させ、引上げ軸５０を１〜２０ｒｐｍで回転させながら１〜５ｍｍ/ｈの速度で垂直に引き上げることによって、種結晶１００から連続的に単結晶を得た。具体的には、シーディング時の結晶回転数を２０ｒｐｍとし、結晶成長の進行とともに結晶回転数を減少させた。固化率０．７までに結晶回転数を３ｒｐｍまで下げた。この操作により育成中結晶１１０の固液界面の凸部高さが１５ｍｍに一定となった。   A crucible 10 made of iridium is filled with a lithium tantalate raw material, and the crucible 10 is heated by a high frequency induction coil 40 made of copper. The lithium tantalate raw material in the crucible 10 was melted to form a raw material melt 90. Then, the seed crystal 100 held at the lower end of the pulling shaft 50 made of iridium is brought into contact with the raw material melt 90, and pulled vertically at a speed of 1 to 5 mm / h while rotating the pulling shaft 50 at 1 to 20 rpm, A single crystal was obtained continuously from the seed crystal 100. Specifically, the crystal rotation number at seeding was set to 20 rpm, and the crystal rotation number was decreased with the progress of crystal growth. The crystal rotation number was reduced to 3 rpm until the solidification rate was 0.7. By this operation, the height of the convex portion of the solid-liquid interface of the crystal 110 became constant at 15 mm during the growth.

ここで、固化率が０．７以上となった時に、（１）式中のａ＝３．３、ｂ＝１２．９の値を得た。育成初期の固液界面形状の凸部の高さを維持するために、原料融液減少とともに結晶回転数を減少させた。具体的には、固化率が０．７５のときには、育成初期と同様の凸部の高さ（１５ｍｍ）となるように（１）式で求めた結晶回転数１ｒｐｍにより育成を実施した。   Here, when the solidification rate became 0.7 or more, values of a = 3.3 and b = 12.9 in the formula (1) were obtained. In order to maintain the height of the convex portion of the solid-liquid interface shape in the initial stage of growth, the number of crystal rotations was decreased along with the decrease in the raw material melt. Specifically, when the solidification rate was 0.75, the growth was performed at a crystal rotation number of 1 rpm obtained by the equation (1) so that the height of the convex portion (15 mm) was the same as in the initial stage of growth.

結晶育成の結果、固化率が０．７以上でも直径変動や多結晶化の発生が無く単結晶を得ることが出来た。
［比較例１］ As a result of crystal growth, even when the solidification rate was 0.7 or more, it was possible to obtain a single crystal without occurrence of diameter fluctuation and polycrystallization.
Comparative Example 1

原料融液減少とともに結晶回転数を減少させ、固化率が０．７となった時に、回転数を３ｒｐｍに一定として結晶育成を継続させたこと以外は、実施例と同様の操作を行った。   The same operation as in the example was performed except that the crystal rotation number was decreased with the decrease of the raw material melt, and when the solidification rate was 0.7, the rotation number was kept constant at 3 rpm and the crystal growth was continued.

結晶育成の結果、固化率が０．７以上の部分から結晶直径が減少し、多結晶化した。また、固化率０．７５で結晶成長を終了し、固液界面形状を確認すると、固液界面形状の凸部の高さが育成初期よりも大きくなり、約２２ｍｍとなった。
［比較例２］ As a result of crystal growth, the crystal diameter decreased from the portion where the solidification rate was 0.7 or more, and polycrystallized. Further, when crystal growth was finished at a solidification rate of 0.75 and the solid-liquid interface shape was confirmed, the height of the convex portion of the solid-liquid interface shape became larger than the initial stage of growth, and became about 22 mm.
Comparative Example 2

原料融液減少とともに結晶回転数を減少させ、固化率が０．７以上となったところで、育成初期の固液界面形状を維持する目的で、結晶回転数を３ｒｐｍから５ｒｐｍに上げて凸部高さが低くなるように操作したこと以外は、実施例と同様の操作を行った。   The crystal rotation number is reduced with the decrease of the raw material melt, and when the solidification rate is 0.7 or more, the crystal rotation number is increased from 3 rpm to 5 rpm for the purpose of maintaining the solid-liquid interface shape at the initial stage of growth. The same operation as in the example was performed except that the operation was performed so as to be low.

結晶育成の結果、固化率が０．７以上の部分で結晶直径が減少し多結晶化した。また、固化率０．７５で結晶成長を終了し、固液界面形状を確認すると、固液界面形状の凸部の高さが育成初期よりも大きくなり約２５ｍｍとなった。   As a result of crystal growth, the crystal diameter decreased and polycrystallized at a portion where the solidification rate was 0.7 or more. Further, when the crystal growth was completed at a solidification rate of 0.75 and the solid-liquid interface shape was confirmed, the height of the convex portion of the solid-liquid interface shape became larger than the initial stage of growth, and became about 25 mm.

このように、本実施例によれば、固化率が０．７以上の長尺化した結晶を製造する場合であっても、多結晶化されない良質な単結晶を得ることができる。   As described above, according to the present embodiment, even in the case of producing a crystal in which the solidification ratio is elongated 0.7 or more, it is possible to obtain a good-quality single crystal which is not polycrystalline.

以上、本発明の好ましい実施形態及び実施例について詳説したが、本発明は、上述した実施形態及び実施例に制限されることはなく、本発明の範囲を逸脱することなく、上述した実施例に種々の変形及び置換を加えることができる。   Although the preferred embodiments and examples of the present invention have been described above in detail, the present invention is not limited to the above-described embodiments and examples, and can be applied to the above-described embodiments without departing from the scope of the present invention. Various modifications and substitutions can be made.

１０ ルツボ
２０ 支持台
３０ 耐火物
４０ 高周波誘導コイル
５０ 引き上げ軸
５１ モーター
６０ チャンバー
７０ 電源
８０ 制御部
９０ 原料融液
１００ 種結晶
１１０ 単結晶 Reference Signs List 10 crucible 20 support base 30 refractory 40 high frequency induction coil 50 pulling shaft 51 motor 60 chamber 70 power supply 80 control unit 90 raw material melt 100 seed crystal 110 single crystal

上記目的を達成するため、本発明の一態様に係る単結晶製造方法は、原料融液に種結晶を接触させてから該種結晶を回転させながら引き上げて単結晶を育成する単結晶製造方法であって、
前記単結晶の底面が下方に所定の突出高さを維持して突出するように前記単結晶の回転速度を制御しながら前記単結晶を育成する単結晶育成工程を有し、
該単結晶育成工程は、前記回転速度と前記単結晶の底面の前記突出高さとの関係特性が、前記原料融液から前記単結晶に固化した重量比率を示す固化率の所定の値の前後において異なっており、前記所定の値により分けられる各領域において、異なる前記関係特性に基づいて、前記単結晶の回転速度を制御する第１及び第２の単結晶育成工程を含む。
In order to achieve the above object, a single crystal production method according to an aspect of the present invention is a single crystal production method in which a seed crystal is brought into contact with a raw material melt and then pulled while rotating the seed crystal to grow a single crystal. There,
And a single crystal growing step of growing the single crystal while controlling the rotational speed of the single crystal such that the bottom surface of the single crystal protrudes downward while maintaining a predetermined protruding height.
In the single crystal growing step, the relationship characteristic between the rotation speed and the protruding height of the bottom surface of the single crystal is before and after a predetermined value of a solidification ratio indicating a weight ratio solidified from the raw material melt to the single crystal. different and in each region is divided by the predetermined value, based on the relational characteristics different, including first and second single crystal growth step of controlling the rotational speed of the single crystal.

Claims (6)

原料融液に種結晶を接触させてから該種結晶を回転させながら引き上げて単結晶を育成する単結晶製造方法であって、
前記単結晶の底面が下方に所定の突出高さを維持して突出するように前記単結晶の回転速度を制御しながら前記単結晶を育成する単結晶育成工程を有し、
該単結晶育成工程は、前記原料融液から前記単結晶に固化した重量比率を示す固化率が所定の値となった前後において、前記回転速度と前記突出高さとの関係を示す関係特性が異なる２つの特性に基づいて前記単結晶の回転速度を制御する第１及び第２の単結晶育成工程を含む単結晶製造方法。 A method for producing a single crystal, comprising bringing a seed crystal into contact with a raw material melt and pulling it while rotating the seed crystal to grow a single crystal,
And a single crystal growing step of growing the single crystal while controlling the rotational speed of the single crystal such that the bottom surface of the single crystal protrudes downward while maintaining a predetermined protruding height.
In the single crystal growing step, the relationship characteristic indicating the relationship between the rotational speed and the protrusion height is different before and after the solidification ratio indicating the weight ratio of the raw material melt solidified to the single crystal becomes a predetermined value. A single crystal manufacturing method comprising first and second single crystal growing steps of controlling the rotation speed of the single crystal based on two characteristics. 前記固化率を示す前記所定の値は、０．７以上である請求項１に記載の単結晶製造方法。   The method according to claim 1, wherein the predetermined value indicating the solidification rate is 0.7 or more. 前記第２の単結晶育成工程では、前記回転速度と前記単結晶の底面の前記突出高さとの関係特性が比例関係にある特性に基づいて前記回転速度を制御する請求項１又は２に記載の単結晶製造方法。   In the second single crystal growth step, the rotational speed is controlled based on the characteristic that the relative characteristic between the rotational speed and the protrusion height of the bottom surface of the single crystal is in a proportional relation. Single crystal manufacturing method. 前記比例関係にある特性は、前記単結晶の底面の前記突出高さをＨ、前記単結晶の回転速度をωとしたときに、下記の（１）式で示される請求項３に記載の単結晶製造方法。
Ｈ＝ａω＋ｂ （１）
但し、ａ、ｂは実験により定まる定数であり、０＜ａを満たす。 The characteristic according to the proportional relationship is expressed by the following equation (1), wherein H is the height of the protrusion of the bottom of the single crystal and ω is the rotational speed of the single crystal. Crystal manufacturing method.
H = aω + b (1)
However, a and b are constants determined by experiment and satisfy 0 <a. 前記第１の単結晶育成工程では、前記回転速度と前記単結晶の底面の前記突出高さとの関係特性が反比例関係にある特性に基づいて前記回転速度を制御する請求項１乃至４のいずれか一項に記載の単結晶製造方法。   The rotational speed is controlled based on the characteristic in which the relative characteristic between the rotational speed and the protrusion height of the bottom surface of the single crystal is inversely proportional in the first single crystal growth step. The single crystal manufacturing method as described in one term. 前記反比例関係にある特性は、前記単結晶の底面の前記突出高さをＨ、前記単結晶の回転速度をωとしたときに、下記の（２）式で示される請求項５に記載の単結晶製造方法。
Ｈ＝ｃ／ω＋ｄ （２）
但し、ｃ、ｄは実験により定まる定数であり、０＜ｃを満たす。 The characteristic according to the inverse relationship is expressed by the following equation (2), wherein H is the height of the protrusion of the bottom of the single crystal and ω is the rotational speed of the single crystal. Crystal manufacturing method.
H = c / ω + d (2)
However, c and d are constants determined by experiment and satisfy 0 <c.

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