JP3555661B2

JP3555661B2 - Single crystal growth method

Info

Publication number: JP3555661B2
Application number: JP05967594A
Authority: JP
Inventors: 和央蔵重; 靖倉田; 浩之石橋
Original assignee: Hitachi Chemical Co Ltd; Showa Denko Materials Co Ltd
Current assignee: Showa Denko Materials Co Ltd
Priority date: 1994-03-30
Filing date: 1994-03-30
Publication date: 2004-08-18
Anticipated expiration: 2019-08-18
Also published as: JPH07267779A

Description

【０００１】
【産業上の利用分野】
本発明は、電子機器等に用いられる単結晶の育成方法に関する。
【０００２】
【従来の技術】
るつぼを加熱することによりるつぼ内の原料を融液にし、融液に種結晶を接触させ、種結晶を徐々に引き上げながら透明な単結晶を育成する方法では、固液界面の形状は融液側に凸または平坦にして育成していた。（文献：高木一正他、ＧＧＧ：「実験物理学講座１３」Ｐ．３７３，１９８１）
【０００３】
【発明が解決しようとする課題】
しかし、この方法では、単結晶が育成冷却中に割れるという問題があった。本発明は割れ発生のない単結晶を得る方法を提供するものである。
【０００４】
【課題を解決するための手段】
上記目的を達成するために、本発明者らは、るつぼ内の原料を加熱して融液とし、その融液に種結晶の下端を接触させ、種結晶を引き上げながら透明な単結晶を育成する透明な単結晶が単斜晶系に属する単結晶及びセリウム付活珪酸ガドリニウム単結晶から選ばれる単結晶である少なくとも直径５０ｍｍ以上の単結晶育成において、結晶直胴部を育成する際の結晶回転速度を少なくとも５０ｒｐｍ以上にし、直胴部育成中の液界面の形状を結晶側に凸とすることにより、結晶直胴部の側面に圧縮の残留応力を発生させ、結晶の割れをふせぐ上記目的を達成できることを見出したことにより、本発明はなされたものである。直胴部育成中とは、融液に種結晶の下端を接触させ種結晶を引き上げながら単結晶を育成する場合、種結晶から目的径まで結晶径を広げ目的径になった後、直胴部として育成される段階を言う。
【０００５】
【作用】
るつぼ内の原料を加熱して融液とし、その融液に種結晶の下端を接触させ、種結晶を引き上げながら透明な単結晶を育成する透明な単結晶の育成において、液界面を結晶側に凸にする条件で透明な単結晶を育成することによって、割れの発生を防止できる原因は、次のように考えられる。
液界面形状を結晶側に凸にすると、結晶成長時には、結晶の回転中心の方が結晶の側面に比べ高温で育成される。従って、これを均一な温度分布中まで冷却すると、結晶側面に圧縮の残留応力が発生する。結晶が割れるのは、引っ張りの応力であるので、この圧縮の残留応力により割れが抑制される。
【０００６】
比較例
結晶系が単斜晶系に属するセリウム付活珪酸ガドリニウム単結晶（Ｃｅ：Ｇｄ_２ＳｉＯ_５）の場合の例を説明する。原料として、Ｇｄ_２Ｏ_３約３２４０ｇ、ＳｉＯ_２約５６０ｇ、ＣｅＯ_２約１０ｇを直径１００ｍｍのＩｒるつぼ中に採り、φ５０×１８０ｍｍの結晶をチョクラルスキー法で育成した。
高周波誘導加熱によりるつぼを加熱し原料を融液とし、１〜５ｍｍ／時間で引き上げながら結晶を成長させた。直胴部を育成する際、結晶の回転速度は３０〜４０ｒｐｍとした。この方法により、結晶のテールが０〜１０ｍｍ凸な結晶を１０本育成した。
【０００７】
実施例
従来例と同様にＧＳＯ単結晶をチョクラルスキー法で育成した。
セリウム付活珪酸ガドリニウム単結晶（Ｃｅ：Ｇｄ_２ＳｉＯ_５）の場合の例を説明する。原料として、Ｇｄ_２Ｏ_３約３２４０ｇ、ＳｉＯ_２約５６０ｇ、ＣｅＯ_２約１０ｇを直径１００ｍｍのＩｒるつぼ中に採り、φ５０×１８０ｍｍの結晶をチョクラルスキー法で育成した。
高周波誘導加熱によりるつぼを加熱し原料を融液とし、１〜５ｍｍ／時間で引き上げながら結晶を成長させた。直胴部を育成する際、結晶の回転速度は５０ｒｐｍとした。この方法により、結晶のテールが凹な結晶を３本育成した。
本発明の実施例で育成を行うことによる割れの発生率を、比較例の育成結果と比較した。その結果を表１に示す。
【０００８】
【表１】

【０００９】
この表からわかるように、従来例の固液界面の形状が融液方向に凸な育成方法では、８０％割れが発生した。実施例の固液界面の形状が結晶方向に凸な育成条件で育成を行うことによって、割れの発生を完全に防止することができることがわかる。
本発明の実施例では、結晶径が単斜晶系に属するセリウム付活珪酸ガドリニウム単結晶について述べたが、他の透明な単結晶についても同様な効果が期待できる。また、割れにくい結晶についても、本発明により内部歪みが減少することは望ましいことである。
【００１０】
【発明の効果】
本発明の育成方法により、割れが発生しやすい透明な結晶について、割れの発生を防止することができる。[0001]
[Industrial applications]
The present invention relates to a method for growing a single crystal used for electronic equipment and the like.
[0002]
[Prior art]
In the method in which the material in the crucible is melted by heating the crucible, a seed crystal is brought into contact with the melt, and a transparent single crystal is grown while gradually pulling up the seed crystal. They were raised to be convex or flat. (Literature: Kazumasa Takagi et al., GGG: "Experimental Physics Course 13" P.373, 1981)
[0003]
[Problems to be solved by the invention]
However, this method has a problem that the single crystal is broken during the growth and cooling. The present invention provides a method for obtaining a single crystal having no cracks.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, the present inventors heat a raw material in a crucible into a melt, contact the lower end of the seed crystal with the melt, and grow a transparent single crystal while pulling up the seed crystal. In the case of growing a single crystal having a diameter of at least 50 mm, which is a single crystal in which the transparent single crystal belongs to a monoclinic single crystal and a cerium-activated gadolinium silicate single crystal, the crystal rotation speed when growing a crystal body portion At least 50 rpm or more, and the shape of the liquid interface during the growth of the straight body portion is made convex toward the crystal side, thereby generating a compressive residual stress on the side surface of the straight body portion of the crystal and achieving the above object of preventing cracking of the crystal. The present invention has been made by finding out what can be done. When growing a single crystal while bringing the seed crystal into contact with the lower end of the seed crystal and pulling the seed crystal up, the crystal diameter is expanded from the seed crystal to the target diameter until the target diameter is reached. The stage that is cultivated as.
[0005]
[Action]
The raw material in the crucible is heated to form a melt, the lower end of the seed crystal is brought into contact with the melt, and a transparent single crystal is grown while pulling up the seed crystal. The reason why the generation of cracks can be prevented by growing a transparent single crystal under the convex condition is considered as follows.
If the shape of the liquid interface is convex toward the crystal, the center of rotation of the crystal grows at a higher temperature than the side surface of the crystal during crystal growth. Therefore, when this is cooled down to a uniform temperature distribution, a compressive residual stress is generated on the crystal side surface. Since the crystal cracks due to tensile stress, cracking is suppressed by the residual stress of this compression.
[0006]
Comparative Example An example in which the crystal system is a cerium-activated gadolinium silicate single crystal (Ce: Gd ₂ SiO ₅ ) belonging to a monoclinic system will be described. As raw materials, about 3240 g of Gd ₂ O ₃ , about 560 g of SiO ₂ , and about 10 g of CeO ₂ were taken in an Ir crucible having a diameter of 100 mm, and crystals of φ50 × 180 mm were grown by the Czochralski method.
The crucible was heated by high-frequency induction heating to obtain a melt as a raw material, and a crystal was grown while being pulled at 1 to 5 mm / hour. When growing the straight body, the rotation speed of the crystal was 30 to 40 rpm. By this method, ten crystals with crystal tails having a convexity of 0 to 10 mm were grown.
[0007]
Example A GSO single crystal was grown by the Czochralski method as in the conventional example.
An example of a cerium-activated gadolinium silicate single crystal (Ce: Gd ₂ SiO ₅ ) will be described. As raw materials, about 3240 g of Gd ₂ O ₃ , about 560 g of SiO ₂ , and about 10 g of CeO ₂ were taken in an Ir crucible having a diameter of 100 mm, and crystals of φ50 × 180 mm were grown by the Czochralski method.
The crucible was heated by high-frequency induction heating to obtain a melt as a raw material, and a crystal was grown while being pulled at 1 to 5 mm / hour. When growing the straight body, the rotation speed of the crystal was 50 rpm. By this method, three crystals with concave crystal tails were grown.
The rate of occurrence of cracks caused by growing in the example of the present invention was compared with the growth result of the comparative example. Table 1 shows the results.
[0008]
[Table 1]

[0009]
As can be seen from this table, the conventional growth method in which the shape of the solid-liquid interface is convex in the direction of the melt caused 80% cracking. It can be seen that cracking can be completely prevented by growing under the growth conditions in which the shape of the solid-liquid interface in the example is convex in the crystal direction.
In the embodiments of the present invention, a cerium-activated gadolinium silicate single crystal having a crystal diameter belonging to a monoclinic system has been described. However, similar effects can be expected with other transparent single crystals. It is also desirable that the present invention reduces the internal strain of a crystal that is difficult to crack.
[0010]
【The invention's effect】
According to the growing method of the present invention, it is possible to prevent the occurrence of cracks in a transparent crystal in which cracks are likely to occur.

Claims

The raw material in the crucible is heated to form a melt, the lower end of the seed crystal is brought into contact with the melt, and the single crystal that grows a transparent single crystal while pulling up the seed crystal belongs to the monoclinic single crystal and cerium. In the method for growing a single crystal having a diameter of at least 50 mm, which is a single crystal selected from active gadolinium silicate single crystals, the crystal rotation speed when growing the crystal body is set to at least 50 rpm, and the solid-liquid interface during the growth of the body is increased. A method for growing a single crystal, characterized in that by making the shape convex toward the crystal side, a compressive residual stress is generated on the side surface of the straight body of the crystal to prevent cracking of the crystal.