JP2004123407A

JP2004123407A - Crystal growth apparatus and crystal growth method

Info

Publication number: JP2004123407A
Application number: JP2002286555A
Authority: JP
Inventors: Akira Otsuka; 大塚　晃; Takeshi Yamada; 山田　剛; Genichi Murakami; 村上　元一
Original assignee: Dowa Mining Co Ltd
Current assignee: Dowa Holdings Co Ltd
Priority date: 2002-09-30
Filing date: 2002-09-30
Publication date: 2004-04-22

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for facilitating cleaning of a crystal growth furnace. <P>SOLUTION: A circulating route 3 for extracting the in-furnace atmosphere in the crystal growth furnace 2 to the outside of the furnace and for returning the same again into the furnace is formed and an impurity trap 4 for catching the impurities in the in-furnace atmosphere is disposed at the circulating route 3. In growing a crystal from a raw material melt liquid, the atmosphere removed of the impurities is supplied into the furnace while the in-furnace atmosphere is extracted to the outside of the furnace. The load of cleaning work can be reduced and productivity can be improved according to the apparatus. Also, the fog of a peephole for in-furnace observation is reduced and the in-furnace visibility during crystal growth can be improved. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は，例えばシリコンや化合物半導体等の結晶を成長させる結晶成長装置と結晶成長方法に関する。
【０００２】
【従来の技術】
シリコンや化合物半導体の結晶成長炉では，原料や劣化した炉内部品から発生するダストや，原料から発生する気化成分などといった不純物が，炉内雰囲気中に含まれてしまう。特に化合物半導体の種類によっては，結晶成長中に半導体材料の高蒸気圧成分が気化することにより多量の不純物を発生する場合もある。このような不純物による悪影響を回避するために，結晶成長炉内のクリーニング作業が必要となる。
【０００３】
ここで，かようなクリーニング作業にかかる負荷をなるべく軽減することが望ましい。また，クリーニング作業に要する時間を短縮できれば，それだけ結晶成長炉の稼働回数を増やすことができ，生産性が向上する。更に，化合物半導体の種類などによっては，高蒸気圧成分は有害物質である場合もあり，結晶成長炉内のクリーニング作業はなるべく短時間でできることが好ましい。
【０００４】
そこで従来より，結晶成長炉のクリーニング作業の負荷軽減，時間短縮等を目的として，種々のクリーニング方法が提案されてきた。例えば，特許文献１として示す特開平０６−３４０４９１号公報には，炉内部品を一括交換できる構造にして複数組み用意しておき，使用済み炉内部品と整備済み炉内部品を取り替える方法が開示されている。また，特開２０００−２１９５９１号公報には，排気管内に堆積した粉塵をクリーニングする方法が開示されている。また，特開２００１−３４８２９３号公報には，チャンバ内面をワイパーでクリーニングする方法が開示されている。
【０００５】
【特許文献１】
特開平６−３４０４９１号公報（例えば段落０００９，図１）
【特許文献２】
特開２０００−２１９５９１号公報（例えば段落０００６，図１）
【特許文献３】
特開２００１−３４８２９３号公報（例えば段落００２５，図１）
【０００６】
【発明が解決しようとする課題】
しかし，特許文献１の方法では，炉内部品が複数組必要になり，また，クリーニング専用の装置や，それらの保管スペースが余計に必要になる。また，炉内部品の交換作業にも手間がかかる。加えて，特許文献１の方法では，炉内に付着したダストなどは除去することができない。また，特許文献２や特許文献３の方法では，結晶成長炉の運転中はクリーニングができない。そのため，結晶成長炉の運転時間の他に，クリーニングの時間が余計にかかり，生産効率が向上できない。
【０００７】
本発明の目的は，結晶成長炉のクリーニングを容易にさせる手段を提供することにある。
【０００８】
【課題を解決するための手段】
この目的を達成するために，本発明の結晶成長装置は，原料融液から結晶を成長させる結晶成長炉を備え，炉内雰囲気を炉外に抜き出して，再び炉内に戻す循環経路を形成し，この循環経路に，炉内雰囲気中の不純物を捕捉する不純物トラップを設けている。前記循環経路は，炉内雰囲気を結晶成長炉の上部から抜き出し，結晶成長炉の下部に戻すように構成されていることが好ましい。前記循環経路には，送風機を設けても良い。
【０００９】
本発明では，結晶成長炉内において原料融液から結晶を成長させるにあたり，炉内雰囲気を炉外に抜き出しつつ，不純物が除去された雰囲気を炉内に供給する。この場合，炉外に抜き出した炉内雰囲気を，不純物を除去した後，再び炉内に戻すようにしても良い。なお，炉内雰囲気を結晶成長炉の上部から抜き出しつつ，不純物が除去された雰囲気を結晶成長炉の下部に供給することが好ましい。
【００１０】
【発明の実施の形態】
以下，本発明の好ましい実施の形態を，図面を参照にして説明する。図１は，本発明の実施の形態かかる結晶成長装置１の概略的な構成を示す説明図である。
【００１１】
結晶成長炉２は，例えばチョクラルスキー法やＬＥＣ法，ＶＧＦ法等によって，原料融液から例えばシリコンや化合物半導体等の結晶を成長させるものである。このため，結晶成長炉２の内部には，図示はしないが，原料融液を貯めておくためのるつぼや，結晶成長中に原料融液を加熱するためヒータなどが配置されている。
【００１２】
この結晶成長炉２の炉内雰囲気を一旦炉外に抜き出し，再び炉内に戻す循環経路３が形成されている。図示の例では，循環経路３の一端は結晶成長炉２の上部に接続され，循環経路３の他端は結晶成長炉２の下部に接続されている。結晶成長炉２内においては，ヒータ（図示せず）の加熱によって上昇気流が発生する。結晶成長炉２内において上昇した炉内雰囲気は，結晶成長炉２の上部に接続された循環経路３内に流れ込み，循環経路３の一端から他端に向って流れる間に温度降下し，結晶成長炉２の下部に戻される。こうして，結晶成長炉２内で発生する対流（上昇気流）を利用して，結晶成長炉２の下部→結晶成長炉２の上部→循環経路３の順に流れる循環流が形成される。
【００１３】
循環経路３には，炉内雰囲気中の不純物を捕捉する不純物トラップ４が設けてある。炉内雰囲気中には，結晶成長させる原料や劣化した炉内部品から発生するダストや，原料から発生する気化成分（高蒸気圧成分等）などといった不純物が含まれている。不純物トラップ４は，例えば邪魔板や冷却機構などを備えており，邪魔板によってダストを除去するとともに，循環経路３内を流れる炉内雰囲気を冷却機構で冷却して，炉内雰囲気中の気化成分を捕捉するようになっている。
【００１４】
図示の例では，循環経路３には，不純物トラップ４の他に，送風機５，流量計６，流量調整弁７が設けてある。循環経路３おいて，不純物トラップ４が最も上流側に位置し，その下流に送風機５，流量計６，流量調整弁７が設けてある。
【００１５】
この結晶成長装置１にあっては，結晶成長炉２内において原料融液から結晶を成長させるにあたり，結晶成長炉２内において上昇した炉内雰囲気を，結晶成長炉２の上部→循環経路３→結晶成長炉２の下部の順に循環させる。この循環流の形成は，結晶成長炉２内に発生する対流（上昇気流）に任せても良いが，循環流量が大きすぎる場合は，流量調整弁７の開度を絞り，流量を調整すると良い。また，結晶成長炉２内の上昇気流だけでは循環流量が少なすぎる場合は，送風機５を稼動させれば良い。なお，送風機５の稼動で強制循環させる場合，流量調整弁７によって，循環流量を任意の値に自動制御することもできる。
【００１６】
こうして結晶成長炉２内の炉内雰囲気を，循環経路３を介して循環させながら，不純物トラップ４によって，循環経路３内を流れる炉内雰囲気中からダストや気化成分といった不純物を捕捉する。そして，不純物を除去した炉内雰囲気を，結晶成長炉２の下部に供給することにより，結晶成長炉２内において，不純物の除去された雰囲気で結晶成長を行うことが可能となる。また，結晶成長炉２の内壁や炉内部品に付着堆積する不純物が少なくなり，クリーニング作業が容易になる。
【００１７】
以上，本発明の好ましい実施の形態の一例を示したが，本発明はここで説明した形態に限定されない。例えば，結晶成長炉２の炉内雰囲気は必ずしも循環させる必要はなく，炉内雰囲気を結晶成長炉２外に抜き出しつつ，別の供給源から不純物が除去された雰囲気を結晶成長炉２内に供給するようにしても良い。なお，結晶成長炉２では上昇気流が発生するので，炉内雰囲気を結晶成長炉２の上部から抜き出しつつ，不純物が除去された雰囲気を結晶成長炉２の下部に供給することが好ましい。また，結晶成長炉２において行う結晶成長方法は，チョクラルスキー法やＬＥＣ法，ＶＧＦ法等，何れでも良い。
【００１８】
なお，不純物トラップ４は，クリーニング頻度を少なくするために，ある程度量のダストを溜めておける容量を持っていることが望ましい。また，循環経路３には，不純物トラップ４を複数設置しても良い。この場合，複数の不純物トラップ４を直列に配置しても良いが，循環経路３を並列に分岐させ，各分岐経路に不純物トラップ４をそれぞれ設置しても良い。そうすれば，一つの不純物トラップ４をクリーニング中においても，他の分岐経路に設置された不純物トラップ４に結晶成長炉２内の雰囲気を循環させ，不純物を除去することができ，連続的な操業を行うことが可能となる。
【００１９】
【実施例】
次に，本発明の実施例を説明する。図２は，実施例に用いた結晶成長装置１０の説明図である。この実施例では，液体封止引上法（ＬＥＣ法）による化合物半導体結晶成長炉（以下「ＬＥＣ炉」）１１を用いた。
【００２０】
ＬＥＣ炉１１の内部には，原料融液が充填（チャージ）されるるつぼ１２が設けてある。るつぼ１２はサセプタ１３で保持され，サセプタ１３は，回転及び昇降可能なるつぼ軸１４の上端に支持される。るつぼ１２の上方には，結晶を上方に引上げるための結晶軸１５が配置される。るつぼ１２の周囲には，ヒータ１６や，それを囲む断熱材１７などが配置される。これらは，通常のＬＥＣ炉１１と同様の構成である。この実施例のＬＥＣ炉１１は，上部部材２０，中部部材２１，下部部材２２で構成されて，開閉可能である。
【００２１】
ＬＥＣ炉１１の炉内雰囲気をＬＥＣ炉１１の上部から一旦炉外に抜き出し，ＬＥＣ炉１１の下部から再び炉内に戻す循環経路２５が形成され，この循環経路２５に，２つの不純物トラップ２６，２６と，その下流側に配置されたブロワ容器２７内のブロア（送風機）２８及び流量計２９が設置されている。結晶成長中，ＬＥＣ炉１１内は高温，高圧となっており，炉内雰囲気は，ＬＥＣ炉１１の上部から，２つの不純物トラップ２６，２６，ブロワ容器２７，流量計２９の順に循環経路２５内を流れ，再びＬＥＣ炉１１の下部に循環供給される。
【００２２】
各不純物トラップ２６は，冷却水を利用した水冷容器３０を備え，水冷容器３０の上面には，循環経路２５内を流れる炉内雰囲気の入口３１と出口３２が形成されている。また，水冷容器３０の内部空間は，下端においてのみ流通可能な邪魔板３３によって，入口３１側と出口３２側に仕切られている。そして，各不純物トラップ２６においては，入口３１から入った炉内雰囲気は，水冷容器３０内の入口３１側を下降し，邪魔板３３の下側を通過した後，水冷容器３０内の出口３２側を上昇して行く。このように，炉内雰囲気が不純物トラップ２６を通過する際に，邪魔板３３によって炉内雰囲気中のダストが除去されるとともに，原料などから発生した炉内雰囲気中の気化成分（高蒸気圧成分など）が，水冷容器３０の内面で冷却されて捕捉されるようになっている。こうして不純物トラップ２６で捕捉されたダストや気化成分などの不純物は，水冷容器３０の底部に溜まるようになっている。
【００２３】
ブロア２８は電動式であり，流量計２９と連動し，任意の循環流量に自動調整することができる。循環経路２５を構成する配管や，各不純物トラップ２６の筐体，ブロワ容器２７などは何れもステンレス製であり，各シール部にはＯリング等を配置することにより，循環経路２５内を循環する炉内雰囲気が外部に漏れ出ない構成になっている。
【００２４】
この結晶成長装置１０のＬＥＣ炉１１を用いて，ＧａＡｓ単結晶を成長させた。ＧａとＡｓをるつぼ１２にチャージし，ＧａＡｓを合成後，単結晶を引上げる直接合成方式とした。ＬＥＣ炉１１，循環経路２５，２つの不純物トラップ２６，２６，ブロワ容器２７をあわせた循環系内の容量は約０．８ｍ^３である。ＧａＡｓ直接合成時の圧力は６ＭＰａ，結晶成長時の炉内圧力は２．５ＭＰａ，炉内雰囲気循環流量は，直接合成時では０．２〜０．３Ｎｍ^３／ｍｉｎ，結晶成長時では０．１Ｎｍ^３／ｍｉｎとなるようにブロワ２８を稼動した。ＬＥＣ炉１１の上部部材２０，中部部材２１，下部部材２２について炉内のダスト付着量を評価すると，ブロワ２８の稼働時と非稼働時では，以下のようになった。
【００２５】
ブロワ非稼働時
上部部材２０：中部部材２１：下部部材２２：ダストトラップ
＝５：３：２：０
ブロワ稼働時
上部部材２０：中部部材２１：下部部材２２：ダストトラップ
＝３：２：０：５
【００２６】
ブロワ２８の稼働時では，循環経路２５に炉内雰囲気が循環されることにより，炉内雰囲気中のダストや気化成分といった不純物が不純物トラップ２６，２６で捕捉され，ＬＥＣ炉１１内の付着量が減った。特に下部部材２２についてはクリーニングの必要が無くなった。不純物トラップ２６，２６に溜まった不純物は，１０Ｒｕｎに１回程度クリーニングすれば良く，ＬＥＣ炉１１に比べて小さいのでクリーニング作業も簡単である。なお，ＬＥＣ炉１１には炉内観察の為の覗き窓が付いているが，ブロワ２８を稼動させることにより覗き窓に付着する不純物が減少し，炉内視認性が高まった。
【００２７】
【発明の効果】
本発明によれば，結晶成長炉のクリーニングを容易にすることが可能となる。このため，クリーニング作業の負荷を軽減でき，生産性も向上する。また，チョクラルスキー法やＬＥＣ法のように，炉内観察用の覗き窓が付いている結晶成長炉では，窓の曇りを軽減し，結晶成長時の炉内視認性を向上することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態かかる結晶成長装置の概略的な構成を示す説明図である。
【図２】実施例に用いた結晶成長装置の説明図である。
【符号の説明】
１　　結晶成長装置
２　　結晶成長炉
３　　循環経路
４　　不純物トラップ
５　　送風機
６　　流量計
７　　流量調整弁
１０　結晶成長装置
１１　ＬＥＣ炉
１２　るつぼ
１３　サセプタ
１４　るつぼ軸
１５　結晶軸
１６　ヒータ
１７　断熱材
２０　上部部材
２１　中部部材
２２　下部部材
２５　循環経路
２６　不純物トラップ
２７　ブロワ容器
２８　ブロア
２９　流量計
３０　水冷容器
３１　入口
３２　出口
３３　邪魔板[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a crystal growth apparatus and a crystal growth method for growing a crystal such as silicon or a compound semiconductor.
[0002]
[Prior art]
In a silicon or compound semiconductor crystal growth furnace, impurities such as dust generated from raw materials and deteriorated furnace components and vaporized components generated from the raw materials are contained in the furnace atmosphere. Particularly, depending on the type of the compound semiconductor, a large amount of impurities may be generated due to vaporization of a high vapor pressure component of the semiconductor material during crystal growth. In order to avoid such adverse effects due to impurities, a cleaning operation in the crystal growth furnace is required.
[0003]
Here, it is desirable to reduce the load on such cleaning work as much as possible. Further, if the time required for the cleaning operation can be reduced, the number of times of operation of the crystal growth furnace can be increased accordingly, and the productivity is improved. Further, depending on the type of the compound semiconductor, the high vapor pressure component may be a harmful substance, and it is preferable that the cleaning operation in the crystal growth furnace can be performed in a short time.
[0004]
Therefore, conventionally, various cleaning methods have been proposed for the purpose of reducing the load of the cleaning operation of the crystal growth furnace and shortening the time. For example, Japanese Unexamined Patent Publication No. Hei 06-340481, which is disclosed in Patent Document 1, discloses a method of replacing a used furnace part with a repaired furnace part by preparing a plurality of sets with a structure in which furnace parts can be replaced collectively. Have been. Japanese Patent Application Laid-Open No. 2000-219591 discloses a method of cleaning dust accumulated in an exhaust pipe. Japanese Patent Application Laid-Open No. 2001-348293 discloses a method of cleaning the inner surface of a chamber with a wiper.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 6-340493 (for example, paragraph 0009, FIG. 1)
[Patent Document 2]
JP 2000-219591 A (for example, paragraph 0006, FIG. 1)
[Patent Document 3]
JP 2001-348293 A (for example, paragraph 0025, FIG. 1)
[0006]
[Problems to be solved by the invention]
However, the method of Patent Document 1 requires a plurality of sets of components in the furnace, and further requires a dedicated device for cleaning and an additional storage space for them. In addition, it takes time to replace parts in the furnace. In addition, with the method of Patent Document 1, dust or the like adhering to the inside of the furnace cannot be removed. Further, according to the methods of Patent Documents 2 and 3, cleaning cannot be performed during operation of the crystal growth furnace. Therefore, in addition to the operation time of the crystal growth furnace, cleaning time is additionally required, and the production efficiency cannot be improved.
[0007]
An object of the present invention is to provide means for facilitating cleaning of a crystal growth furnace.
[0008]
[Means for Solving the Problems]
In order to achieve this object, the crystal growth apparatus of the present invention is provided with a crystal growth furnace for growing a crystal from a raw material melt, and forms a circulation path for extracting the atmosphere in the furnace out of the furnace and returning it to the inside of the furnace again. An impurity trap for trapping impurities in the furnace atmosphere is provided in this circulation path. It is preferable that the circulation path is configured to extract the atmosphere in the furnace from the upper part of the crystal growth furnace and return the atmosphere to the lower part of the crystal growth furnace. A blower may be provided in the circulation path.
[0009]
In the present invention, when growing a crystal from a raw material melt in a crystal growth furnace, an atmosphere from which impurities have been removed is supplied into the furnace while extracting the furnace atmosphere from the furnace. In this case, the atmosphere in the furnace extracted from the furnace may be returned to the furnace again after removing impurities. It is preferable to supply the atmosphere from which impurities have been removed to the lower part of the crystal growth furnace while extracting the furnace atmosphere from the upper part of the crystal growth furnace.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram illustrating a schematic configuration of a crystal growth apparatus 1 according to an embodiment of the present invention.
[0011]
The crystal growth furnace 2 grows a crystal such as silicon or a compound semiconductor from a raw material melt by, for example, the Czochralski method, the LEC method, the VGF method, or the like. For this reason, a crucible for storing the raw material melt, a heater for heating the raw material melt during crystal growth, and the like are arranged inside the crystal growth furnace 2 (not shown).
[0012]
A circulation path 3 is formed in which the atmosphere in the furnace of the crystal growth furnace 2 is once extracted out of the furnace and returned to the inside of the furnace again. In the illustrated example, one end of the circulation path 3 is connected to the upper part of the crystal growth furnace 2, and the other end of the circulation path 3 is connected to the lower part of the crystal growth furnace 2. In the crystal growth furnace 2, an ascending airflow is generated by heating a heater (not shown). The atmosphere in the furnace that has risen in the crystal growth furnace 2 flows into the circulation path 3 connected to the upper part of the crystal growth furnace 2, and the temperature drops while flowing from one end of the circulation path 3 to the other end. It is returned to the lower part of the furnace 2. Thus, a circulating flow that flows in the order of the lower part of the crystal growth furnace 2 → the upper part of the crystal growth furnace 2 → the circulation path 3 is formed by utilizing the convection (ascending current) generated in the crystal growth furnace 2.
[0013]
The circulation path 3 is provided with an impurity trap 4 for capturing impurities in the furnace atmosphere. The furnace atmosphere contains impurities such as raw materials for crystal growth, dust generated from deteriorated furnace components, and vaporized components (high vapor pressure components and the like) generated from the raw materials. The impurity trap 4 is provided with, for example, a baffle plate and a cooling mechanism. The baffle plate removes dust, and cools the furnace atmosphere flowing in the circulation path 3 by the cooling mechanism, thereby evaporating the vaporized components in the furnace atmosphere. Is to be captured.
[0014]
In the illustrated example, a blower 5, a flow meter 6, and a flow control valve 7 are provided in the circulation path 3 in addition to the impurity trap 4. In the circulation path 3, the impurity trap 4 is located at the most upstream side, and a blower 5, a flow meter 6, and a flow control valve 7 are provided downstream thereof.
[0015]
In the crystal growth apparatus 1, when growing a crystal from a raw material melt in the crystal growth furnace 2, the atmosphere in the furnace raised in the crystal growth furnace 2 is changed from the upper part of the crystal growth furnace 2 to the circulation path 3 →. It is circulated in the order of the lower part of the crystal growth furnace 2. The formation of this circulating flow may be left to the convection (updraft) generated in the crystal growth furnace 2, but if the circulating flow is too large, the opening of the flow control valve 7 may be reduced to adjust the flow. . If the circulating flow rate is too small by only the rising airflow in the crystal growth furnace 2, the blower 5 may be operated. In the case of forced circulation by operation of the blower 5, the circulating flow can be automatically controlled to an arbitrary value by the flow regulating valve 7.
[0016]
Thus, while circulating the atmosphere in the crystal growth furnace 2 through the circulation path 3, the impurity trap 4 captures impurities such as dust and vaporized components from the atmosphere in the furnace flowing in the circulation path 3. By supplying the furnace atmosphere from which impurities have been removed to the lower portion of the crystal growth furnace 2, it becomes possible to perform crystal growth in the crystal growth furnace 2 in an atmosphere from which impurities have been removed. Further, the amount of impurities adhering and depositing on the inner wall of the crystal growth furnace 2 and components inside the furnace is reduced, and the cleaning operation is facilitated.
[0017]
The preferred embodiment of the present invention has been described above, but the present invention is not limited to the embodiment described here. For example, the atmosphere in the furnace of the crystal growth furnace 2 does not necessarily need to be circulated, and the atmosphere in which impurities are removed from another supply source is supplied into the crystal growth furnace 2 while extracting the atmosphere inside the furnace from the crystal growth furnace 2. You may do it. Since an upward air flow is generated in the crystal growth furnace 2, it is preferable to supply the atmosphere from which impurities are removed to the lower part of the crystal growth furnace 2 while extracting the furnace atmosphere from the upper part of the crystal growth furnace 2. The crystal growth method performed in the crystal growth furnace 2 may be any of the Czochralski method, the LEC method, the VGF method, and the like.
[0018]
It is desirable that the impurity trap 4 has a capacity for storing a certain amount of dust in order to reduce the frequency of cleaning. Further, a plurality of impurity traps 4 may be provided in the circulation path 3. In this case, a plurality of impurity traps 4 may be arranged in series, or the circulation path 3 may be branched in parallel, and the impurity traps 4 may be installed in each branch path. By doing so, even while one impurity trap 4 is being cleaned, the atmosphere in the crystal growth furnace 2 can be circulated to the impurity trap 4 installed in the other branch path to remove impurities, and continuous operation can be performed. Can be performed.
[0019]
【Example】
Next, embodiments of the present invention will be described. FIG. 2 is an explanatory diagram of the crystal growth apparatus 10 used in the embodiment. In this embodiment, a compound semiconductor crystal growth furnace (hereinafter referred to as “LEC furnace”) 11 using a liquid sealing pull-up method (LEC method) was used.
[0020]
A crucible 12 is provided inside the LEC furnace 11 to be charged (charged) with the raw material melt. The crucible 12 is held by a susceptor 13, and the susceptor 13 is supported on the upper end of a crucible shaft 14 that can rotate and move up and down. Above the crucible 12, a crystal axis 15 for pulling the crystal upward is arranged. Around the crucible 12, a heater 16 and a heat insulating material 17 surrounding the heater 16 are arranged. These have the same configuration as the normal LEC furnace 11. The LEC furnace 11 of this embodiment includes an upper member 20, a middle member 21, and a lower member 22, and can be opened and closed.
[0021]
A circulation path 25 is formed in which the atmosphere inside the LEC furnace 11 is once extracted from the upper part of the LEC furnace 11 and returned to the furnace from the lower part of the LEC furnace 11, and two impurity traps 26, 26, a blower (blower) 28 and a flow meter 29 in a blower container 27 arranged downstream thereof are provided. During the crystal growth, the inside of the LEC furnace 11 is at a high temperature and high pressure, and the atmosphere in the furnace is from the top of the LEC furnace 11 in the circulation path 25 in the order of the two impurity traps 26, 26, the blower vessel 27, and the flow meter 29. And is circulated and supplied again to the lower part of the LEC furnace 11.
[0022]
Each impurity trap 26 is provided with a water cooling container 30 using cooling water, and an inlet 31 and an outlet 32 of a furnace atmosphere flowing in the circulation path 25 are formed on the upper surface of the water cooling container 30. Further, the internal space of the water-cooled container 30 is partitioned into an inlet 31 side and an outlet 32 side by a baffle plate 33 which can be circulated only at the lower end. In each of the impurity traps 26, the furnace atmosphere entered from the inlet 31 descends on the inlet 31 side in the water-cooled vessel 30, passes under the baffle plate 33, and then exits on the outlet 32 side in the water-cooled vessel 30. Go up. As described above, when the furnace atmosphere passes through the impurity trap 26, dust in the furnace atmosphere is removed by the baffle plate 33, and vaporized components (high vapor pressure components) in the furnace atmosphere generated from raw materials and the like. ) Are cooled and captured by the inner surface of the water-cooled container 30. Thus, impurities such as dust and vaporized components trapped by the impurity trap 26 accumulate at the bottom of the water-cooled vessel 30.
[0023]
The blower 28 is electrically driven and interlocks with a flow meter 29 so that the blower 28 can be automatically adjusted to an arbitrary circulation flow rate. The piping constituting the circulation path 25, the housing of each impurity trap 26, the blower container 27, etc. are all made of stainless steel, and are circulated in the circulation path 25 by disposing an O-ring or the like in each seal portion. The atmosphere in the furnace does not leak to the outside.
[0024]
Using the LEC furnace 11 of the crystal growth apparatus 10, a GaAs single crystal was grown. Ga and As were charged into the crucible 12 to synthesize GaAs, and then the single crystal was pulled up to form a direct synthesis method. The capacity in the circulation system including the LEC furnace 11, the circulation path 25, the two impurity traps 26, 26, and the blower container 27 is about 0.8 m ³ . The pressure during direct GaAs synthesis is 6 MPa, the furnace pressure during crystal growth is 2.5 MPa, and the atmosphere circulation flow rate in the furnace is 0.2 to 0.3 Nm ³ / min during direct synthesis and 0.1 Nm during crystal growth. ^The blower 28 was operated at ³ / min. When the amount of dust adhering in the furnace was evaluated for the upper member 20, the middle member 21, and the lower member 22 of the LEC furnace 11, the following results were obtained when the blower 28 was operated and not operated.
[0025]
Blower non-operating upper member 20: middle member 21: lower member 22: dust trap = 5: 3: 2: 0
Blower operating upper member 20: middle member 21: lower member 22: dust trap = 3: 2: 0: 5
[0026]
During the operation of the blower 28, the furnace atmosphere is circulated through the circulation path 25, so that impurities such as dust and vaporized components in the furnace atmosphere are captured by the impurity traps 26, 26, and the amount of adhesion in the LEC furnace 11 is reduced. decreased. In particular, the lower member 22 does not need to be cleaned. The impurities trapped in the impurity traps 26, 26 need only be cleaned about once every 10 Runs, and are smaller than the LEC furnace 11, so that the cleaning operation is simple. The LEC furnace 11 is provided with a viewing window for observation inside the furnace. By operating the blower 28, impurities adhering to the viewing window were reduced, and visibility in the furnace was improved.
[0027]
【The invention's effect】
According to the present invention, it is possible to easily clean the crystal growth furnace. Therefore, the load of the cleaning operation can be reduced, and the productivity can be improved. In a crystal growth furnace with a viewing window for observation inside the furnace, such as the Czochralski method or the LEC method, fogging of the window can be reduced and visibility in the furnace during crystal growth can be improved. .
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a schematic configuration of a crystal growth apparatus according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of a crystal growth apparatus used in an example.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 crystal growth apparatus 2 crystal growth furnace 3 circulation path 4 impurity trap 5 blower 6 flow meter 7 flow control valve 10 crystal growth apparatus 11 LEC furnace 12 crucible 13 susceptor 14 crucible shaft 15 crystal shaft 16 heater 17 heat insulating material 20 upper member 21 middle part Member 22 Lower member 25 Circulation path 26 Impurity trap 27 Blower container 28 Blower 29 Flow meter 30 Water cooling container 31 Inlet 32 Outlet 33 Baffle plate

Claims

Equipped with a crystal growth furnace for growing crystals from the raw material melt,
A crystal growth apparatus, comprising: forming a circulation path for extracting an atmosphere in a furnace to the outside of the furnace and returning it to the inside of the furnace again; and an impurity trap for trapping impurities in the atmosphere in the furnace is provided in the circulation path.

The crystal growth apparatus according to claim 1, wherein the circulation path is configured to extract an atmosphere in the furnace from an upper part of the crystal growth furnace and return the atmosphere to a lower part of the crystal growth furnace.

3. The crystal growth apparatus according to claim 1, wherein a blower is provided in the circulation path.

In growing a crystal from a raw material melt in a crystal growth furnace,
A crystal growth method, wherein an atmosphere from which impurities are removed is supplied into the furnace while extracting the furnace atmosphere from the furnace.

5. The crystal growth method according to claim 4, wherein the furnace atmosphere extracted outside the furnace is returned to the furnace again after removing impurities.

6. The crystal growth method according to claim 4, wherein an atmosphere from which impurities are removed is supplied to a lower portion of the crystal growth furnace while extracting an atmosphere in the furnace from an upper portion of the crystal growth furnace.