JP2004196573A - Manufacturing method of compound semiconductor single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a compound semiconductor single crystal that is capable of efficiently obtaining a single crystal having excellent electrical properties by preventing poly-crystallization thereof. <P>SOLUTION: The manufacturing method of the compound semiconductor single crystal, which covers a whole of crucible storing a compound semiconductor raw material melt with an airtight container and grows the compound semiconductor single crystal by floating a sealant for preventing volatilization of a gas from the compound semiconductor raw material melt, is characterized in that the thickness of the sealant when the single crystal reach the predetermined diameter is in a range of 8 mm-15 mm. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、化合物半導体単結晶の製造方法、特に、液体封止チョクラルスキー法（ＬＥＣ法）によって半絶縁性ＧａＡｓ単結晶を製造するのに好適な化合物半導体単結晶の製造方法に関するものである。
【０００２】
【従来の技術】
ＬＥＣ法によるＧａＡｓ半導体単結晶の製造方法としては、図１に示すように、高圧容器１内にＧａ、Ａｓおよび種結晶６を配置したＰＢＮルツボ２にＧａＡｓ融液からのＡｓ揮発抑止のための封止剤として三酸化硼素７を入れ、真空、ガス置換を行い、続いて、高圧容器１内をヒータ３により加熱してＧａＡｓ融液８を形成し、ＰＢＮルツボ２を移動させてＧａＡｓ融液８最上面の位置をヒータ３の発熱部分の中心位置と一致させる。その後、種結晶６を下降させてＧａＡｓ融液８に接触させ、ヒータ３の出力を調整して高圧容器１内の温度を徐々に下げ、定径まで単結晶９を成長させる。単結晶９を成長させる際、図２に詳細を示すように、定径（一般的には、直径１１５ｍｍ）まで（肩部成長時）は、単結晶９の形状は引上方向に対して１００°である（例えば、特許文献１）。なお、図１において、４はシード軸、５はルツボ軸である。
【０００３】
【特許文献１】
特公平６−１０２５８８号公報
【０００４】
【発明が解決しようとする課題】
ＬＥＣ法による半絶縁性ＧａＡｓ単結晶の製造において、多結晶化の原因の一つに結晶成長初期段階（肩部成長時）においての固液界面の融液８側への凹面化による転位の集合が起点となることが挙げられる。前記した従来技術では、Ａｓ揮発を防止するという観点から、封止剤である三酸化硼素７の厚さｔを２５ｍｍ以上にしており、成長初期段階で結晶頭部付近からの放熱量が不足し、結晶頭部以外からの放熱量が多くなり、固液界面が凹面化し、転位が集中して多結晶化するという問題がある。
【０００５】
本発明は、上記に基づいてなされたものであり、多結晶化を防止することにより化合物半導体単結晶を効率良く得ることができる製造方法の提供を目的とする。
【０００６】
【課題を解決するための手段】
上記目的達成のため、本発明は、化合物半導体原料融液を収容したルツボ全体を気密容器で覆い、前記化合物半導体原料融液からのガスの揮発を抑止する封止剤を浮遊させて化合物半導体単結晶を成長させる化合物半導体単結晶の製造方法において、単結晶が定径に到達したときの前記封止剤の厚さが８ｍｍ〜１５ｍｍの範囲にあるようにした化合物半導体単結晶の製造方法を提供する。
【０００７】
【発明の実施の形態】
本発明は、特に、ＬＥＣ法によって半絶縁性ＧａＡｓ単結晶を製造する場合において、Ａｓの揮発を抑止する封止剤として三酸化硼素を用いた場合に好適である。封止剤の厚さが８ｍｍに達しないときは、融液からガス（例えばＡｓ）が揮発するため融液自体の組成が変化し、結晶の電気特性に異常を来たすようになり、また、組成不良の融液を使用するため結晶成長中に結晶表面からガス（例えばＡｓ）が揮発し、多結晶化しやすくなる。１５ｍｍを越えると、結晶成長初期段階で結晶頭部からの放熱が不足し、固液界面形状が凹面形状となり、転位が集中して多結晶化しやすくなる。
【０００８】
（実施例１）
通常のＬＥＣ法の高圧炉を用い、Ｇａ１０，０００ｇ、Ａｓ１０，５００ｇおよび封止剤である三酸化硼素を、結晶径が定径（約１１５ｍｍ）に到達したとき（引上方向に対して１００°で増径の場合）１２ｍｍの厚さとなる重量をＰＢＮルツボ内に収納する。融点温度以上に加熱し、ＧａＡｓ融液を形成した後、単結晶の引上育成を行い、直径約１１５ｍｍで重量約１７，０００ｇのＧａＡｓ単結晶を作製した。同じ条件で２０本のＧａＡｓ単結晶を作製したが、結晶頭部からの放熱不足による多結晶化は発生しなかった。（製品歩留：１００％）
【０００９】
（実施例２）
三酸化硼素の厚さを８ｍｍにした以外は実施例１と同様にしてＧａＡｓ単結晶を作製した。２０本のＧａＡｓ単結晶を作製したところ、結晶頭部からの放熱不足による多結晶化は発生しなかった。（製品歩留：１００％）
【００１０】
（実施例３）
三酸化硼素の厚さを１５ｍｍにした以外は実施例１と同様にしてＧａＡｓ単結晶を作製した。２０本のＧａＡｓ単結晶を作製したところ、結晶頭部からの放熱不足による多結晶化は発生しなかった。（製品歩留：１００％）
【００１１】
（比較例１）
三酸化硼素の厚さを３ｍｍにした以外は実施例１と同様にしてＧａＡｓ単結晶を作製した。２０本のＧａＡｓ単結晶を作製したところ、１２本が電気特性不良で使用不可、３本が多結晶化した。（製品歩留：２５％）
【００１２】
（比較例２）
三酸化硼素の厚さを５ｍｍにした以外は実施例１と同様にしてＧａＡｓ単結晶を作製した。２０本のＧａＡｓ単結晶を作製したところ、１０本が電気特性不良で使用不可、４本が多結晶化した。（製品歩留：３０％）
【００１３】
（比較例３）
三酸化硼素の厚さを７ｍｍにした以外は実施例１と同様にしてＧａＡｓ単結晶を作製した。２０本のＧａＡｓ単結晶を作製したところ、２本が電気特性不良で使用不可、２本が多結晶化した。（製品歩留：８０％）
【００１４】
（比較例４）
三酸化硼素の厚さを１６ｍｍにした以外は実施例１と同様にしてＧａＡｓ単結晶を作製した。２０本のＧａＡｓ単結晶を作製したところ、３本が多結晶化した。（製品歩留：８８％）
【００１５】
（比較例５）
三酸化硼素の厚さを２０ｍｍにした以外は実施例１と同様にしてＧａＡｓ単結晶を作製した。２０本のＧａＡｓ単結晶を作製したところ、７本が多結晶化した。（製品歩留：６５％）
【００１６】
（比較例６）
三酸化硼素の厚さを２５ｍｍにした以外は実施例１と同様にしてＧａＡｓ単結晶を作製した。２０本のＧａＡｓ単結晶を作製したところ、１１本が多結晶化した。（製品歩留：４５％）
【００１７】
【発明の効果】
以上説明してきた通り、本発明は、化合物半導体原料融液を収容したルツボ全体を気密容器で覆い、前記化合物半導体原料融液からのガスの揮発を抑止する揮発封止剤を浮遊させて化合物半導体単結晶を成長させる化合物半導体単結晶の製造方法において、単結晶が定径に到達したときの前記封止剤の厚さが８ｍｍ〜１５ｍｍの範囲にあるようにした化合物半導体単結晶の製造方法を提供するものであり、これによって、多結晶化を防止して優れた電気特性を有する単結晶を効率良く得ることができるようになる。
【図面の簡単な説明】
【図１】ＬＥＣ法による化合物半導体単結晶の製造方法の説明図。
【図２】単結晶引上の要部説明図。
【符号の説明】
１：高圧容器
２：ＰＢＮルツボ
３：ヒータ
４：シード軸
５：ルツボ軸
６：種結晶
７：封止剤（三酸化硼素）
８：融液
９：単結晶[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a compound semiconductor single crystal, and more particularly to a method for producing a compound semiconductor single crystal suitable for producing a semi-insulating GaAs single crystal by a liquid-sealed Czochralski method (LEC method). .
[0002]
[Prior art]
As a method of manufacturing a GaAs semiconductor single crystal by the LEC method, as shown in FIG. 1, a PBN crucible 2 in which Ga, As, and a seed crystal 6 are arranged in a high-pressure vessel 1 is used to suppress volatilization of As from a GaAs melt. Boron trioxide 7 is charged as a sealant, and vacuum and gas replacement are performed. Subsequently, the inside of the high-pressure vessel 1 is heated by the heater 3 to form a GaAs melt 8, and the PBN crucible 2 is moved to move the GaAs melt. 8 The position of the uppermost surface is matched with the center position of the heat generating portion of the heater 3. Thereafter, the seed crystal 6 is lowered and brought into contact with the GaAs melt 8, the output of the heater 3 is adjusted, the temperature in the high-pressure vessel 1 is gradually lowered, and the single crystal 9 is grown to a constant diameter. As shown in detail in FIG. 2, when growing the single crystal 9, up to a constant diameter (generally, a diameter of 115 mm) (during shoulder growth), the shape of the single crystal 9 is 100 with respect to the pulling direction. ° (for example, Patent Document 1). In FIG. 1, 4 is a seed axis, and 5 is a crucible axis.
[0003]
[Patent Document 1]
Japanese Patent Publication No. 6-102588
[Problems to be solved by the invention]
In the production of a semi-insulating GaAs single crystal by the LEC method, one of the causes of polycrystallization is the aggregation of dislocations due to the concave surface of the solid-liquid interface toward the melt 8 at the initial stage of crystal growth (during shoulder growth). Is a starting point. In the prior art described above, from the viewpoint of preventing As volatilization, the thickness t of the boron trioxide 7 as the sealing agent is set to 25 mm or more, and the amount of heat radiated from the vicinity of the crystal head is insufficient at the initial stage of growth. In addition, there is a problem that the amount of heat radiation from portions other than the crystal head increases, the solid-liquid interface becomes concave, dislocations are concentrated, and polycrystals are formed.
[0005]
The present invention has been made based on the above, and an object of the present invention is to provide a manufacturing method capable of efficiently obtaining a compound semiconductor single crystal by preventing polycrystallization.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a method for covering a whole crucible containing a compound semiconductor raw material melt with an airtight container and suspending a sealing agent for suppressing volatilization of a gas from the compound semiconductor raw material melt to float the compound semiconductor raw material. In a method for producing a compound semiconductor single crystal for growing a crystal, a method for producing a compound semiconductor single crystal is provided in which the thickness of the sealant when the single crystal reaches a constant diameter is in the range of 8 mm to 15 mm. I do.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is particularly suitable when a semi-insulating GaAs single crystal is manufactured by the LEC method, and when boron trioxide is used as a sealing agent for suppressing volatilization of As. When the thickness of the sealant does not reach 8 mm, gas (for example, As) volatilizes from the melt, so that the composition of the melt itself changes and the electrical characteristics of the crystal become abnormal. Since a defective melt is used, gas (for example, As) is volatilized from the crystal surface during crystal growth, and polycrystals are easily formed. If it exceeds 15 mm, the heat radiation from the crystal head will be insufficient at the initial stage of crystal growth, the solid-liquid interface shape will be concave, and dislocations will be concentrated and polycrystals will be easily formed.
[0008]
(Example 1)
Using a normal LEC high-pressure furnace, 10,000 g of Ga, 10,500 g of As, and boron trioxide as a sealant were removed when the crystal diameter reached a constant diameter (about 115 mm) (100 ° with respect to the pulling direction). In the case of increasing the diameter, the weight of 12 mm is stored in the PBN crucible. After heating to a melting point temperature or higher to form a GaAs melt, a single crystal was pulled and grown to produce a GaAs single crystal having a diameter of about 115 mm and a weight of about 17,000 g. Although 20 GaAs single crystals were produced under the same conditions, polycrystallization did not occur due to insufficient heat radiation from the crystal head. (Product yield: 100%)
[0009]
(Example 2)
A GaAs single crystal was produced in the same manner as in Example 1 except that the thickness of boron trioxide was changed to 8 mm. When 20 GaAs single crystals were produced, polycrystallization did not occur due to insufficient heat radiation from the crystal head. (Product yield: 100%)
[0010]
(Example 3)
A GaAs single crystal was produced in the same manner as in Example 1 except that the thickness of boron trioxide was changed to 15 mm. When 20 GaAs single crystals were produced, polycrystallization did not occur due to insufficient heat radiation from the crystal head. (Product yield: 100%)
[0011]
(Comparative Example 1)
A GaAs single crystal was produced in the same manner as in Example 1 except that the thickness of boron trioxide was changed to 3 mm. When 20 GaAs single crystals were produced, 12 were unusable due to poor electrical characteristics and 3 were polycrystallized. (Product yield: 25%)
[0012]
(Comparative Example 2)
A GaAs single crystal was produced in the same manner as in Example 1 except that the thickness of boron trioxide was changed to 5 mm. When 20 GaAs single crystals were produced, 10 were unusable due to poor electrical characteristics and 4 were polycrystalline. (Product yield: 30%)
[0013]
(Comparative Example 3)
A GaAs single crystal was produced in the same manner as in Example 1 except that the thickness of boron trioxide was changed to 7 mm. When 20 GaAs single crystals were produced, 2 of them were unusable due to poor electrical characteristics and 2 were polycrystalline. (Product yield: 80%)
[0014]
(Comparative Example 4)
A GaAs single crystal was produced in the same manner as in Example 1 except that the thickness of boron trioxide was changed to 16 mm. When 20 GaAs single crystals were produced, three were polycrystallized. (Product yield: 88%)
[0015]
(Comparative Example 5)
A GaAs single crystal was produced in the same manner as in Example 1, except that the thickness of boron trioxide was changed to 20 mm. When 20 GaAs single crystals were produced, 7 were polycrystallized. (Product yield: 65%)
[0016]
(Comparative Example 6)
A GaAs single crystal was produced in the same manner as in Example 1 except that the thickness of boron trioxide was changed to 25 mm. When 20 GaAs single crystals were produced, 11 were polycrystallized. (Product yield: 45%)
[0017]
【The invention's effect】
As described above, the present invention provides a compound semiconductor by covering an entire crucible containing a compound semiconductor raw material melt with an airtight container and suspending a volatile sealing agent for suppressing volatilization of gas from the compound semiconductor raw material melt. In the method for producing a compound semiconductor single crystal for growing a single crystal, the method for producing a compound semiconductor single crystal, wherein the thickness of the sealant when the single crystal reaches a constant diameter is in a range of 8 mm to 15 mm. Accordingly, a single crystal having excellent electric characteristics can be efficiently obtained by preventing polycrystallization.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a method for manufacturing a compound semiconductor single crystal by an LEC method.
FIG. 2 is an explanatory view of a main part of pulling a single crystal.
[Explanation of symbols]
1: High pressure vessel 2: PBN crucible 3: Heater 4: Seed shaft 5: Crucible shaft 6: Seed crystal 7: Sealant (boron trioxide)
8: Melt 9: Single crystal

Claims (3)

化合物半導体原料融液を収容したルツボ全体を気密容器で覆い、前記化合物半導体原料融液からのガスの揮発を抑止する封止剤を浮遊させて化合物半導体単結晶を成長させる化合物半導体単結晶の製造方法において、単結晶が定径に到達したときの前記封止剤の厚さが８ｍｍ〜１５ｍｍの範囲にあるようにしたことを特徴とする化合物半導体単結晶の製造方法。Production of a compound semiconductor single crystal in which the entire crucible containing the compound semiconductor material melt is covered with an airtight container, and a sealing agent for suppressing volatilization of gas from the compound semiconductor material melt is floated to grow the compound semiconductor single crystal. A method for producing a compound semiconductor single crystal, wherein the thickness of the sealant when the single crystal reaches a constant diameter is in the range of 8 mm to 15 mm. 前記化合物半導体原料融液は、ＧａＡｓ融液である請求項１記載の化合物半導体単結晶の製造方法。The method for producing a compound semiconductor single crystal according to claim 1, wherein the compound semiconductor raw material melt is a GaAs melt. 前記封止剤は、三酸化硼素である請求項１記載の化合物半導体単結晶の製造方法。The method for producing a compound semiconductor single crystal according to claim 1, wherein the sealing agent is boron trioxide.

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