JP6206178B2

JP6206178B2 - Single crystal pulling method

Info

Publication number: JP6206178B2
Application number: JP2013270641A
Authority: JP
Inventors: 中村　剛; 中村　　剛; 拓也四ッ井
Original assignee: Sumco Corp
Current assignee: Sumco Corp
Priority date: 2013-12-27
Filing date: 2013-12-27
Publication date: 2017-10-04
Anticipated expiration: 2033-12-27
Also published as: TW201534773A; JP2015124127A; TWI624569B

Description

本発明は、ＣＺ法（チョクラルスキー法）によりシリコン単結晶やＧａＡｓ単結晶等の単結晶を引上げる方法に関するものである。 The present invention relates to a method for pulling a single crystal such as a silicon single crystal or a GaAs single crystal by a CZ method (Czochralski method).

従来、半導体単結晶の育成炉内においてルツボに収容した原料融液に、磁場印加装置により磁場を印加しながら、単結晶の引上げを行うＭＣＺ法（磁界下引上げ法）による半導体単結晶の製造方法が開示されている（例えば、特許文献１参照。）。この半導体単結晶の製造方法では、半導体単結晶の引上げ量の増加に合せて、融液の表面位置がほぼ一定となるようにルツボを上昇させるとともに、磁場印加装置をルツボに追従させて上昇させるように構成される。また磁場印加装置は、ルツボ内に存在している融液に印加される磁場の中心位置が、融液内に定められる目標位置に対してほぼ一定の関係が保持されるように上昇される。更にルツボ内の初期融液深さに基づいて初期目標位置を定め、磁場中心位置が初期目標位置と一致するように、磁場印加装置をルツボに対して位置決めし、その後、半導体単結晶の引上げ工程を開始するとともに、半導体単結晶の引上げ進行によりルツボ底位置が上昇して融液の深さが小さくなるのに伴い、目標位置を初期目標位置から上方に移動させるとともに、その移動する目標位置に対して磁場印加装置を追従上昇させる。 Conventionally, a method for producing a semiconductor single crystal by an MCZ method (pulling under a magnetic field) in which a single crystal is pulled while applying a magnetic field to a raw material melt stored in a crucible in a semiconductor single crystal growth furnace. Is disclosed (for example, see Patent Document 1). In this method of manufacturing a semiconductor single crystal, the crucible is raised so that the surface position of the melt is substantially constant as the semiconductor single crystal is pulled up, and the magnetic field application device is raised following the crucible. Configured as follows. In addition, the magnetic field applying device is raised so that the center position of the magnetic field applied to the melt existing in the crucible is maintained in a substantially constant relationship with the target position determined in the melt. Further, an initial target position is determined based on the initial melt depth in the crucible, the magnetic field application device is positioned with respect to the crucible so that the magnetic field center position coincides with the initial target position, and then the semiconductor single crystal pulling step As the crucible bottom position rises as the semiconductor single crystal pulls up and the melt depth decreases, the target position is moved upward from the initial target position and moved to the target position. On the other hand, the magnetic field applying device is raised.

このように構成された半導体単結晶の製造方法では、単結晶引上げに伴いルツボ中の融液量、即ち融液深さは減少するけれども、対流抑制等のために融液に磁場印加する際に、その磁場中心の最適位置は融液内にて刻々変化するので、その最適位置を目標位置とし、融液の深さが小さくなるに従い刻々変化するその目標位置に対して、磁場印加装置を追従移動させることにより、磁場を常に対流抑制等に関する最適位置に保持することができる。この結果、酸素濃度が低く均質な半導体単結晶が得ることができる。 In the method of manufacturing a semiconductor single crystal configured in this way, the amount of melt in the crucible, that is, the melt depth decreases as the single crystal is pulled, but when a magnetic field is applied to the melt to suppress convection. Since the optimum position of the magnetic field center changes every moment in the melt, the optimum position is set as the target position, and the magnetic field application device follows the target position that changes momentarily as the melt depth decreases. By moving the magnetic field, the magnetic field can always be held at the optimum position for convection suppression. As a result, a homogeneous semiconductor single crystal having a low oxygen concentration can be obtained.

また、製造する半導体単結晶の直径を一定に保ち易くするために、半導体単結晶の引上げ量の増加に伴い、融液の表面位置がほぼ一定となるようにルツボを上昇させる。この場合、磁場印加装置は、ルツボ内に存在している融液に印加される磁場の磁場中心位置が、融液内に定められる目標位置に対してほぼ一定の関係が保持されるように上昇させることが、融液中に発生する対流を抑制する上で望ましい。具体的には、ルツボ内に存在している融液の深さをＨＬとし、融液の表面から目標位置までの深さ方向の距離をＨＡとするとき、ＨＡ／ＨＬがほぼ一定となるように目標位置を定めるのがよい。例えば、目標位置を、ルツボ内の融液における深さ方向の中心部、又はこれより下方に位置するように（即ちＨＡ／ＨＬが０．５若しくはこれよりも少し大きい値となるように）設定し、磁場中心を該目標位置に合せることにより、単結晶引上げの全工程において、ルツボ内の融液のほぼ全体に所望の強度範囲の磁場を印加することができる。換言すれば、従来のＨＭＣＺ法に比べて、単結晶引上げの全工程において、ルツボ内の融液に印加する磁場の強度分布の均一性を向上させることができる。この結果、ルツボ内の融液の対流抑制効果が著しく高まり、酸素濃度が低く均一で、しかも欠陥の少ない大直径の単結晶を安定して製造できるようになっている。 Further, in order to easily keep the diameter of the semiconductor single crystal to be manufactured, the crucible is raised so that the surface position of the melt becomes substantially constant as the amount of the semiconductor single crystal pulled increases. In this case, the magnetic field application device raises the magnetic field center position of the magnetic field applied to the melt existing in the crucible so as to maintain a substantially constant relationship with the target position determined in the melt. It is desirable to suppress the convection generated in the melt. Specifically, when the depth of the melt existing in the crucible is HL and the distance in the depth direction from the melt surface to the target position is HA, HA / HL is substantially constant. It is better to set the target position. For example, the target position is set so as to be located at or below the center of the melt in the crucible in the depth direction (that is, HA / HL is 0.5 or slightly larger than this). By aligning the center of the magnetic field with the target position, a magnetic field having a desired intensity range can be applied to almost the entire melt in the crucible in all steps of pulling the single crystal. In other words, compared to the conventional HMCZ method, the uniformity of the strength distribution of the magnetic field applied to the melt in the crucible can be improved in all steps of pulling the single crystal. As a result, the effect of suppressing the convection of the melt in the crucible is remarkably increased, and a large-diameter single crystal having a low oxygen concentration and a uniform density with few defects can be stably produced.

国際公開第２００２／０１０４８５号パンフレット（請求項１〜３、第９頁第２７行〜第１０頁第４行、第１０頁第７行〜同頁第２３行、図７〜図１０）WO2002 / 010485 pamphlet (claims 1 to 3, page 9, line 27 to page 10, line 4, page 10, line 7 to line 23, page 7 to figure 10)

しかし、上記従来の特許文献１に示された半導体単結晶の製造方法では、表面の揺らぎによるバラツキが大きく、また表面がきらきら光ってしまい測定し難い融液の表面位置を基準として磁場中心位置を制御しているため、磁場中心位置を精度良く制御することが難しい不具合があった。 However, in the method for manufacturing a semiconductor single crystal disclosed in the above-mentioned conventional Patent Document 1, the magnetic field center position is determined based on the surface position of the melt, which is largely uneven due to surface fluctuations and is difficult to measure because the surface glitters. Due to the control, it was difficult to control the magnetic field center position with high accuracy.

一方、育成炉内に使用される部品としては、複数の円筒体を積重ねて形成された保温筒や、上端が保温筒の上端に取付けられ引上げ中の半導体単結晶を包囲する熱遮蔽体等が挙げられ、これらの部品は、ヒータにより融液を加熱する関係上、高温に曝されるため、断熱性及び耐熱性を有する黒鉛やカーボン等により形成される。また育成炉を用いて複数本の半導体単結晶を引上げるため、半導体単結晶を１本引上げる毎に育成炉内の加熱及び冷却が繰返され、育成炉内の各部品がＳｉＣ化したり或いは劣化する。更に融液に印加する水平磁場は、磁場中心に近付くほど磁場強度が大きくなって磁場の水平度が高くなり、磁場中心から離れるほど磁場強度が小さくなって磁場の水平度が低下する。このため、保温筒がＳｉＣ化したり或いは劣化することにより、保温筒の熱膨張量が次第に変化してその上端位置が次第に上昇したり或いは下降し、これに伴って熱遮蔽体の位置も鉛直方向に変化する。この結果、水平磁場の中心位置に対する熱遮蔽体の位置がずれてしまうため、引上げられる半導体単結晶の品質にバラツキが生じる問題点があった。 On the other hand, as parts used in the growth furnace, there are a heat insulating cylinder formed by stacking a plurality of cylindrical bodies, a heat shield that is attached to the upper end of the heat insulating cylinder and surrounds the semiconductor single crystal being pulled up, etc. Since these components are exposed to high temperatures in relation to heating the melt with a heater, they are formed of graphite or carbon having heat insulation and heat resistance. Also, since a plurality of semiconductor single crystals are pulled up using a growth furnace, heating and cooling in the growth furnace are repeated each time one semiconductor single crystal is pulled up, and each part in the growth furnace becomes SiC or deteriorates. To do. Furthermore, as the horizontal magnetic field applied to the melt is closer to the magnetic field center, the magnetic field strength increases and the magnetic field level increases, and as the distance from the magnetic field center increases, the magnetic field strength decreases and the magnetic field level decreases. For this reason, when the thermal insulation cylinder is changed to SiC or deteriorates, the thermal expansion amount of the thermal insulation cylinder gradually changes, and its upper end position gradually rises or falls, and accordingly, the position of the thermal shield is also in the vertical direction. To change. As a result, the position of the heat shield relative to the center position of the horizontal magnetic field is shifted, and there is a problem that the quality of the pulled semiconductor single crystal varies.

本発明の目的は、水平磁場の中心位置を熱遮蔽体の鉛直方向の位置のずれ量に応じて調整することにより、引上げられる単結晶の品質のバラツキを低減できる、単結晶の引上げ方法を提供することにある。本発明の別の目的は、鉛直方向の位置を測定し易い固体である熱遮蔽体のずれ量に応じて水平磁場の中心位置を精度良く調整することにより、単結晶の品質のバラツキを更に低減できる、単結晶の引上げ方法を提供することにある。 An object of the present invention is to provide a method for pulling a single crystal that can reduce variations in the quality of the pulled single crystal by adjusting the center position of the horizontal magnetic field according to the amount of deviation in the vertical position of the heat shield. There is to do. Another object of the present invention is to further reduce the quality variation of the single crystal by accurately adjusting the center position of the horizontal magnetic field according to the amount of deviation of the heat shield, which is a solid whose position in the vertical direction is easy to measure. An object is to provide a method for pulling a single crystal.

本発明の第１の観点は、ＣＺ炉のチャンバに収容されたルツボに原料を入れる工程と、このルツボ内の原料をヒータで加熱してルツボに融液を貯留する工程と、このルツボ内の融液に水平磁場を印加した状態であって融液表面より上方に位置する熱遮蔽体が融液から引上げられる単結晶外周面を包囲してヒータによる単結晶外周面への輻射熱の照射を遮った状態で単結晶を引上げる方法において、ヒータによりルツボ内の融液を加熱した状態であってＣＺ炉での最初の単結晶の引上げ前に、熱遮蔽体のチャンバに対する鉛直方向の位置である熱遮蔽体の初回位置を測定する工程と、熱遮蔽体の初回位置を基準として水平磁場の中心位置をその設定位置に合せる工程と、ヒータによりルツボ内の融液を加熱した状態であってＣＺ炉での２本目以降の単結晶の引上げ前又は引上げ中に、熱遮蔽体の鉛直方向の位置を測定して熱遮蔽体が上記初回位置から鉛直方向にずれた量を算出する工程と、この熱遮蔽体の鉛直方向へのずれ量に応じて水平磁場の中心位置を鉛直方向に調整する工程とを含むことを特徴とする。 A first aspect of the present invention includes a step of putting a raw material in a crucible housed in a chamber of a CZ furnace, a step of heating the raw material in the crucible with a heater and storing a melt in the crucible, In a state where a horizontal magnetic field is applied to the melt, a heat shield positioned above the melt surface surrounds the outer surface of the single crystal pulled up from the melt and blocks the irradiation of radiant heat to the outer surface of the single crystal by the heater. In the method of pulling up the single crystal in a heated state, the position in the vertical direction with respect to the chamber of the heat shield is the state in which the melt in the crucible is heated by the heater and before the first single crystal is pulled in the CZ furnace. A step of measuring the initial position of the thermal shield, a step of adjusting the center position of the horizontal magnetic field to the set position with reference to the initial position of the thermal shield, and a state in which the melt in the crucible is heated by the heater, and CZ Second and later in the furnace Measuring the vertical position of the thermal shield before and during the pulling of the single crystal, and calculating the amount of deviation of the thermal shield in the vertical direction from the initial position, and the vertical direction of the thermal shield And a step of adjusting the center position of the horizontal magnetic field in the vertical direction in accordance with the amount of shift to.

本発明の第２の観点は、第１の観点に基づく発明であって、更に熱遮蔽体の下端部下面と融液の表面との距離が７０〜１５０ｍｍの範囲内であることを特徴とする。 A second aspect of the present invention is the invention based on the first aspect, wherein the distance between the lower surface of the lower end of the heat shield and the surface of the melt is in the range of 70 to 150 mm. .

本発明の第３の観点は、第１又は第２の観点に基づく発明であって、更にルツボの上部の内径をｄ₁ｍｍとし、引上げ中の単結晶の直胴部の直径をｄ₂ｍｍとし、熱遮蔽体の下端の半径方向の厚さをｔｍｍとするとき、熱遮蔽体の下端部内周面と引上げ中の単結晶の外周面との距離が、５０ｍｍ以上かつ［（ｄ₁−ｄ₂−２ｔ）／２］ｍｍ以下であることを特徴とする。 A third aspect of the present invention is the invention based on the first or second aspect, wherein the inner diameter of the upper part of the crucible is d ₁ mm, and the diameter of the straight body of the single crystal being pulled is d ₂ mm. When the thickness in the radial direction of the lower end of the heat shield is tmm, the distance between the inner peripheral surface of the lower end of the heat shield and the outer peripheral surface of the single crystal being pulled is 50 mm or more and [(d ₁ -d ₂ -2t) / 2] mm or less.

ＣＺ炉内の加熱及び冷却の繰返しにより、熱遮蔽体や保温筒等の各部品がＳｉＣ化したり或いは劣化し、保温筒の熱膨張量が次第に変化してその上端位置が次第に上昇したり或いは下降し、これに伴って熱遮蔽体の鉛直方向の位置も変化する。しかし、本発明の第１の観点の単結晶の引上げ方法では、ヒータによるルツボ内の融液の加熱状態でＣＺ炉での最初の単結晶の引上げ前に熱遮蔽体の初回位置を測定し、熱遮蔽体の初回位置を基準として水平磁場の中心位置をその設定位置に合せ、ヒータによるルツボ内の融液の加熱状態でＣＺ炉での２本目以降の単結晶の引上げ前又は引上げ中に熱遮蔽体が上記初回位置から鉛直方向にずれた量を測定し、更にこのずれ量に応じて水平磁場の中心位置を鉛直方向に調整するので、ＣＺ炉内の各部品の劣化等により熱遮蔽体の鉛直方向の位置が変化しても、水平磁場の中心位置を熱遮蔽体の鉛直方向の位置のずれ量に応じて調整できる。この結果、引上げられる単結晶の品質のバラツキを低減できる。 Due to repeated heating and cooling in the CZ furnace, each part such as the heat shield and the heat insulation cylinder becomes SiC or deteriorates, the thermal expansion amount of the heat insulation cylinder gradually changes, and its upper end position gradually rises or falls. Accordingly, the vertical position of the heat shield also changes. However, in the method for pulling a single crystal according to the first aspect of the present invention, the initial position of the heat shield is measured before pulling the first single crystal in the CZ furnace in the heated state of the melt in the crucible by the heater. The center position of the horizontal magnetic field is adjusted to the set position with respect to the initial position of the heat shield, and heat is applied before or during the pulling of the second and subsequent single crystals in the CZ furnace in the heated state of the melt in the crucible by the heater. Since the amount of deviation of the shield in the vertical direction from the initial position is measured, and the center position of the horizontal magnetic field is adjusted in the vertical direction according to the amount of deviation, the heat shield is caused by deterioration of each component in the CZ furnace. Even if the position in the vertical direction changes, the center position of the horizontal magnetic field can be adjusted in accordance with the amount of deviation in the vertical position of the heat shield. As a result, it is possible to reduce variations in the quality of the pulled single crystal.

また、表面の揺らぎによるバラツキが大きく、また表面がきらきら光ってしまい測定し難い融液の表面位置を基準として磁場中心位置を制御しているため、磁場中心位置を精度良く制御することが難しい従来の半導体単結晶の製造方法と比較して、本発明では、鉛直方向の位置を測定し易い固体である熱遮蔽体の鉛直方向の位置を測定しているため、この熱遮蔽体の鉛直方向の位置のずれ量を精度良く測定できる。この結果、本発明では、熱遮蔽体の鉛直方向の位置のずれ量に応じて水平磁場の中心位置を精度良く調整できるので、単結晶の品質のバラツキを更に低減できる。 In addition, it is difficult to control the magnetic field center position with high accuracy because the fluctuation of the surface is large and the magnetic field center position is controlled on the basis of the melt surface position that is difficult to measure because the surface glitters. In the present invention, since the vertical position of the heat shield, which is a solid that is easy to measure the vertical position, is measured in the present invention, The amount of positional deviation can be accurately measured. As a result, in the present invention, the center position of the horizontal magnetic field can be accurately adjusted according to the amount of deviation of the position of the thermal shield in the vertical direction, so that variations in the quality of the single crystal can be further reduced.

本発明実施形態、実施例及び比較例のシリコン単結晶引上げに用いたＣＺ炉の断面構成図である。It is a section lineblock diagram of a CZ furnace used for pulling up a silicon single crystal of an embodiment of the present invention, an example, and a comparative example. そのＣＺ炉を用いて複数本のシリコン単結晶を順次引上げる手順を示すフローチャート図である。It is a flowchart figure which shows the procedure which pulls up sequentially several silicon single crystal using the CZ furnace.

次に本発明を実施するための形態を図面に基づいて説明する。単結晶は、この実施の形態では、シリコン単結晶であり、このシリコン単結晶は図１に示すＣＺ炉を用いて引上げられる。ＣＺ炉は、内部を真空可能に構成されたメインチャンバ１２と、このチャンバ１２内の中央に設けられたルツボ１３とを備える。メインチャンバ１２は基台１４上に取付けられた円筒状の真空容器である。またルツボ１３は、図示しないが、石英により形成されシリコン融液１６が貯留される有底円筒状の内層容器と、黒鉛により形成され上記内層容器の外側に嵌合された有底円筒状の外層容器とからなる。外層容器の底部にはシャフト１７の上端が接続され、このシャフト１７の下端にはシャフト１７を介してルツボ１３を回転させかつ昇降させるルツボ駆動装置１８が設けられる。更にルツボ１３の外周面は円筒状のヒータ１９によりルツボ１３の外周面から所定の間隔をあけて包囲され、このヒータ１９の外周面は円筒状の保温筒２０によりヒータ１９の外周面から所定の間隔をあけて包囲される。 Next, an embodiment for carrying out the present invention will be described with reference to the drawings. In this embodiment, the single crystal is a silicon single crystal, and this silicon single crystal is pulled using the CZ furnace shown in FIG. The CZ furnace includes a main chamber 12 configured to be evacuated inside, and a crucible 13 provided in the center of the chamber 12. The main chamber 12 is a cylindrical vacuum vessel attached on a base 14. Although not shown, the crucible 13 is formed of quartz and has a bottomed cylindrical inner layer container in which the silicon melt 16 is stored, and a bottomed cylindrical outer layer formed of graphite and fitted to the outside of the inner layer container. A container. The upper end of the shaft 17 is connected to the bottom of the outer container, and a crucible driving device 18 that rotates and raises and lowers the crucible 13 through the shaft 17 is provided at the lower end of the shaft 17. Further, the outer peripheral surface of the crucible 13 is surrounded by a cylindrical heater 19 at a predetermined interval from the outer peripheral surface of the crucible 13, and the outer peripheral surface of the heater 19 is predetermined from the outer peripheral surface of the heater 19 by the cylindrical heat retaining cylinder 20. Surrounded at intervals.

上記保温筒２０は、グラファイト（黒鉛）や成型断熱材（カーボン繊維製）等により形成された高さの低い３種類の円筒体２１〜２３を積重ねることにより形成される。即ち、保温筒２０は、基台１４に載置され上部内周縁にリング状凹部２１ａが形成された下部円筒体２１と、最上段に位置し下部内周縁にリング状突起２２ａが形成された上部円筒体２２と、下部円筒体２１と上部円筒体２２との間に積重ねられ上部内周縁にリング状凹部２３ａが形成されかつ下部内周縁にリング状突起２３ｂが形成された中間円筒体２３とからなる。この実施の形態では、先ず下部円筒体２１のリング状凹部２１ａに中間円筒体２３のリング状突起２３ｂを係合させて、下部円筒体２１上に中間円筒体２３を積重ねる。次にこの中間円筒体２３のリング状凹部２３ａに別の中間円筒体２３のリング状突起２３ｂを係合させて、中間円筒体２３上に別の中間円筒体２３を積重ねる。更にこの別の中間円筒体２３のリング状凹部２３ａに上部円筒体２２のリング状突起２２ａを係合させて、中間円筒体２３上に上部円筒体２２を積重ねる。これにより積重ね後の各円筒体２１〜２３の横ずれを防止できるようになっている。なお、各円筒体２１〜２３のうち内側部分がグラファイト（黒鉛）により形成され、外側部分が成型断熱材（カーボン繊維製）が形成されることが好ましい。 The heat insulating cylinder 20 is formed by stacking three types of cylindrical bodies 21 to 23 having a low height formed of graphite (graphite), a molded heat insulating material (made of carbon fiber), or the like. That is, the heat retaining cylinder 20 is placed on the base 14 and has a lower cylindrical body 21 in which an upper inner peripheral edge is formed with a ring-shaped concave portion 21a, and an upper part that is positioned on the uppermost stage and has a lower inner peripheral edge formed with a ring-shaped protrusion 22a. A cylindrical body 22, and an intermediate cylindrical body 23 stacked between the lower cylindrical body 21 and the upper cylindrical body 22 and having an upper inner peripheral edge formed with a ring-shaped recess 23a and a lower inner peripheral edge formed with a ring-shaped protrusion 23b. Become. In this embodiment, first, the ring-shaped protrusion 23 b of the intermediate cylindrical body 23 is engaged with the ring-shaped recess 21 a of the lower cylindrical body 21, and the intermediate cylindrical body 23 is stacked on the lower cylindrical body 21. Next, the ring-shaped protrusion 23 b of another intermediate cylinder 23 is engaged with the ring-shaped recess 23 a of the intermediate cylinder 23, and the other intermediate cylinder 23 is stacked on the intermediate cylinder 23. Further, the ring-shaped protrusion 22 a of the upper cylindrical body 22 is engaged with the ring-shaped recess 23 a of the other intermediate cylindrical body 23, and the upper cylindrical body 22 is stacked on the intermediate cylindrical body 23. Thereby, the lateral displacement of each cylindrical body 21 to 23 after stacking can be prevented. In addition, it is preferable that an inner part is formed with graphite (graphite) among each cylindrical body 21-23, and a molded heat insulating material (product made from a carbon fiber) is formed in an outer part.

一方、メインチャンバ１２の上端には、内部が連通するようにメインチャンバ１２より小径の円筒状のプルチャンバ２１が接続される。このプルチャンバ２１の上端には引上げ回転装置２２が設けられる。この引上げ回転装置２２は、下端にシードチャック２３が取付けられたワイヤからなる引上げ軸２４を昇降させるとともに、この引上げ軸２４をその軸線を中心に回転させるように構成される。また上記シードチャック２３には種結晶２５が着脱可能に装着される。この種結晶２５の下端をシリコン融液１５中に浸漬した後、種結晶２５を引上げ回転装置２２により回転させかつ引上げるとともに、ルツボ１３をルツボ駆動装置１６により回転させかつ上昇させることにより、種結晶２５の下端からシリコン単結晶１１を引上げて引上げるように構成される。 On the other hand, a cylindrical pull chamber 21 having a smaller diameter than the main chamber 12 is connected to the upper end of the main chamber 12 so as to communicate with the inside. A pulling and rotating device 22 is provided at the upper end of the pull chamber 21. The pulling and rotating device 22 is configured to move up and down a pulling shaft 24 made of a wire having a seed chuck 23 attached to the lower end, and to rotate the pulling shaft 24 around the axis. A seed crystal 25 is detachably attached to the seed chuck 23. After immersing the lower end of the seed crystal 25 in the silicon melt 15, the seed crystal 25 is rotated and pulled by the pulling and rotating device 22, and the crucible 13 is rotated and lifted by the crucible driving device 16. The silicon single crystal 11 is pulled up and pulled up from the lower end of the crystal 25.

一方、シリコン融液１６には水平磁場を印加しながらシリコン単結晶１１を引上げるように構成される。この水平磁場は、同一のコイル直径を有する第１及び第２コイル３１，３２を、ルツボ１３の外周面から水平方向に所定の間隔をあけた外側方に、ルツボ１３を中心として互いに対向するように配設し、これらのコイル３１，３２にそれぞれ同一向きの電流を流すことにより発生する。ここで、図１中の符号３３は上記水平磁場の中心位置を示す。また、第１及び第２コイル３１，３２はコイル昇降装置３４により昇降可能に構成される。このコイル昇降装置３４は、第１及び第２コイル３１，３２を載置するリング部材３６と、基台１４の下面に減速機３７を介して取付けられたロータリエンコーダ付きのコイル昇降モータ３８と、減速機３７から上方に突設されてリング部材３６に螺合するボールねじ３９とを有する。上記コイル昇降モータ３８が回転すると、この回転速度が減速機３７により減速されてボールねじ３９に伝達され、ボールねじ３９がリング部材３６を昇降させることにより、第１及び第２コイル３１，３２が昇降するようになっている。 On the other hand, the silicon melt 16 is configured to pull up the silicon single crystal 11 while applying a horizontal magnetic field. This horizontal magnetic field causes the first and second coils 31 and 32 having the same coil diameter to face each other around the crucible 13 outward from the outer peripheral surface of the crucible 13 in a horizontal direction. It is generated by flowing currents in the same direction through these coils 31 and 32, respectively. Here, reference numeral 33 in FIG. 1 indicates the center position of the horizontal magnetic field. The first and second coils 31 and 32 are configured to be moved up and down by a coil lifting device 34. The coil elevating device 34 includes a ring member 36 on which the first and second coils 31 and 32 are placed, a coil elevating motor 38 with a rotary encoder attached to the lower surface of the base 14 via a speed reducer 37, A ball screw 39 projecting upward from the speed reducer 37 and screwed into the ring member 36; When the coil raising / lowering motor 38 rotates, the rotational speed is reduced by the speed reducer 37 and transmitted to the ball screw 39. The ball screw 39 raises and lowers the ring member 36, whereby the first and second coils 31, 32 are moved. It is designed to go up and down.

一方、メインチャンバ１２内にはアルゴンガス等の不活性ガスが流通される。プルチャンバ２４の周壁にはガス供給パイプ４１の一端が接続され、このガス供給パイプ４１の他端は不活性ガスを貯留するタンク（図示せず）に接続される。また基台１４にはガス排出パイプ４２の一端が接続され、このガス排出パイプ４２の他端は真空ポンプ（図示せず）の吸入口に接続される。タンク内の不活性ガスは、ガス供給パイプ４１を通ってプルチャンバ２４内に導入され、メインチャンバ１２内を通った後、ガス排出パイプ４２を通ってメインチャンバ１２から排出されるように構成される。なお、ガス供給パイプ４１及びガス排出パイプ４２にはこれらのパイプを流れる不活性ガスの流量を調整する入口側流量調整弁４３及び出口側流量調整弁４４がそれぞれ設けられる。 On the other hand, an inert gas such as argon gas is circulated in the main chamber 12. One end of a gas supply pipe 41 is connected to the peripheral wall of the pull chamber 24, and the other end of the gas supply pipe 41 is connected to a tank (not shown) for storing an inert gas. Further, one end of a gas discharge pipe 42 is connected to the base 14, and the other end of the gas discharge pipe 42 is connected to a suction port of a vacuum pump (not shown). The inert gas in the tank is introduced into the pull chamber 24 through the gas supply pipe 41, passes through the main chamber 12, and is then discharged from the main chamber 12 through the gas discharge pipe 42. . The gas supply pipe 41 and the gas discharge pipe 42 are respectively provided with an inlet side flow rate adjustment valve 43 and an outlet side flow rate adjustment valve 44 that adjust the flow rate of the inert gas flowing through these pipes.

またメインチャンバ１２内には、シリコン融液１６から引上げられるシリコン単結晶１１外周面へのヒータ１９の輻射熱の照射を遮るとともに、上記不活性ガスを整流するための熱遮蔽体４６が設けられる。この熱遮蔽体４６はグラファイト（黒鉛）や成型断熱材（カーボン繊維製）等により形成される。また熱遮蔽体４６は、下方に向うに従って直径が次第に小さくなりかつシリコン融液１６から引上げられるシリコン単結晶１１の外周面をこの外周面から所定の間隔をあけて包囲する円錐台状の筒体４６ａと、この筒体４６ａの上縁に連設され外方に略水平方向に張り出すアッパフランジ部４６ｂと、上記筒体４６ａの下縁に連設され内方に略水平方向に張り出すロアフランジ部４６ｃとを有する。熱遮蔽体４６の上端は保温筒２０の上端に取付けられる。この実施の形態では、熱遮蔽体４６のアッパフランジ部４６ｂが保温筒２０の上面に載置される。これによりロアフランジ部４６ｃ下面がシリコン融液１６表面から所定のギャップをあけて上方に位置するように構成される。 In the main chamber 12, a heat shield 46 is provided for blocking radiation of the radiant heat of the heater 19 to the outer peripheral surface of the silicon single crystal 11 pulled up from the silicon melt 16 and rectifying the inert gas. The heat shield 46 is formed of graphite (graphite), molded heat insulating material (made of carbon fiber), or the like. The heat shield 46 has a truncated cone-like cylindrical body that gradually decreases in diameter as it goes downward and surrounds the outer peripheral surface of the silicon single crystal 11 pulled up from the silicon melt 16 at a predetermined interval from the outer peripheral surface. 46a, an upper flange portion 46b that is connected to the upper edge of the cylindrical body 46a and projects outward in a substantially horizontal direction, and a lower flange that is connected to the lower edge of the cylindrical body 46a and projects inward in a substantially horizontal direction Part 46c. The upper end of the heat shield 46 is attached to the upper end of the heat insulating cylinder 20. In this embodiment, the upper flange portion 46 b of the heat shield 46 is placed on the upper surface of the heat retaining cylinder 20. Thus, the lower surface of the lower flange portion 46c is configured to be positioned above the surface of the silicon melt 16 with a predetermined gap.

上記熱遮蔽体４６のロアフランジ部４６ｃ下面とシリコン融液１６の表面との距離は、７０〜１５０ｍｍの範囲内であることが好ましく、７０〜１００ｍｍの範囲内であることが更に好ましい。また、ルツボ１３の上部の内径をｄ₁ｍｍとし、引上げ中のシリコン単結晶１１の直胴部の直径をｄ₂ｍｍとし、熱遮蔽体４６のロアフランジ部４６ｃの半径方向の厚さをｔｍｍとするとき、熱遮蔽体４６のロアフランジ部４６ｃ内周面と引上げ中のシリコン単結晶１１の外周面との距離が、５０ｍｍ以上かつ［（ｄ₁−ｄ₂−２ｔ）／２］ｍｍ以下であることが好ましく、５０〜１２０ｍｍの範囲内であることが更に好ましい。ここで、熱遮蔽体４６のロアフランジ部４６ｃ下面とシリコン融液１６の表面との距離を７０〜１５０ｍｍの範囲内に限定したのは、７０ｍｍ未満では、ヒータ１９からの輻射熱の減少により、シリコン融液１６の温度勾配が上昇してしまい、磁場位置の変化によって生じるシリコン融液１６の対流の変化が、熱対流や強制対流の変化よりも無視できるほど小さくなるため、磁場位置の調整によりシリコン単結晶１１の品質のバラツキを低減するという効果が得られず、１５０ｍｍを超えるとシリコン単結晶１１を安定して引上げることができないからである。また、熱遮蔽体４６のロアフランジ部４６ｃ内周面と引上げ中のシリコン単結晶１１の外周面との距離を５０ｍｍ以上かつ［（ｄ₁−ｄ₂−２ｔ）／２］ｍｍ以下の範囲内に限定したのは、５０ｍｍ未満では、ヒータ１９からの輻射熱の減少により、シリコン融液１６の温度勾配が上昇してしまい、磁場位置の変化によって生じるシリコン融液１６の対流の変化が、熱対流や強制対流の変化よりも無視できるほど小さくなるため、磁場位置の調整によりシリコン単結晶１１の品質のバラツキを低減するという効果が得られず、［（ｄ₁−ｄ₂−２ｔ）／２］ｍｍを超えると熱遮蔽体４６の下部がルツボ１３より大きくなってしまうからである。 The distance between the lower surface of the lower flange portion 46c of the heat shield 46 and the surface of the silicon melt 16 is preferably in the range of 70 to 150 mm, and more preferably in the range of 70 to 100 mm. Also, the inner diameter of the upper part of the crucible 13 is d ₁ mm, the diameter of the straight body part of the silicon single crystal 11 being pulled is d ₂ mm, and the radial thickness of the lower flange part 46c of the heat shield 46 is tmm. In this case, the distance between the inner peripheral surface of the lower flange portion 46c of the heat shield 46 and the outer peripheral surface of the silicon single crystal 11 being pulled is 50 mm or more and [(d ₁ −d ₂ −2t) / 2] mm or less. It is preferable that it is in the range of 50-120 mm. Here, the distance between the lower surface of the lower flange portion 46c of the heat shield 46 and the surface of the silicon melt 16 is limited to the range of 70 to 150 mm. The temperature gradient of the liquid 16 rises, and the change in the convection of the silicon melt 16 caused by the change in the magnetic field position is negligibly smaller than the change in the thermal convection and forced convection. This is because the effect of reducing the variation in quality of the crystal 11 cannot be obtained, and if it exceeds 150 mm, the silicon single crystal 11 cannot be pulled up stably. Further, the distance between the inner peripheral surface of the lower flange portion 46c of the heat shield 46 and the outer peripheral surface of the silicon single crystal 11 being pulled is in the range of 50 mm or more and [(d ₁ −d ₂ −2t) / 2] mm or less. The limitation is that if the thickness is less than 50 mm, the temperature gradient of the silicon melt 16 increases due to a decrease in the radiant heat from the heater 19, and the change in the convection of the silicon melt 16 caused by the change in the magnetic field position causes the heat convection and Since it is negligibly smaller than the change of forced convection, the effect of reducing the quality variation of the silicon single crystal 11 by adjusting the magnetic field position cannot be obtained, and [(d ₁ −d ₂ −2t) / 2] mm. This is because the lower part of the heat shield 46 becomes larger than the crucible 13 if the temperature exceeds.

更にルツボ１３内のシリコン融液１６がヒータ１９により加熱された状態であって、シリコン単結晶１１を引上げる直前における熱遮蔽体４６のロアフランジ部４６ｃ上面のメインチャンバ１２に対する鉛直方向の位置が位置測定具４７により測定される。位置測定具４７は、この実施の形態では、２次元ＣＣＤカメラである。この２次元ＣＣＤカメラ４７の撮影した画像は画像処理装置（図示せず）により処理される。この画像処理装置の処理出力はコントローラ４８の制御入力に接続される。またコントローラ４８の制御出力は、ルツボ駆動装置１８、ヒータ１９、引上げ回転装置２６、第１コイル３１、第２コイル３２、真空ポンプ、コイル昇降モータ３８、入口側流量調整弁４３及び出口側流量調整弁４４に接続される。また、コントローラ４８にはメモリ４８ａが設けられ、このメモリ４８ａには２次元ＣＣＤカメラ４７が測定し画像処理装置により処理されたロアフランジ部４６ｃの鉛直方向の初回位置Ｐ１等が記憶される。 Further, the silicon melt 16 in the crucible 13 is heated by the heater 19, and the position in the vertical direction with respect to the main chamber 12 on the upper surface of the lower flange portion 46 c of the heat shield 46 just before pulling up the silicon single crystal 11 is located. It is measured by the measuring tool 47. In this embodiment, the position measuring tool 47 is a two-dimensional CCD camera. An image captured by the two-dimensional CCD camera 47 is processed by an image processing device (not shown). The processing output of this image processing apparatus is connected to the control input of the controller 48. The control output of the controller 48 includes a crucible driving device 18, a heater 19, a pulling and rotating device 26, a first coil 31, a second coil 32, a vacuum pump, a coil raising / lowering motor 38, an inlet side flow rate adjustment valve 43, and an outlet side flow rate adjustment. Connected to valve 44. The controller 48 is provided with a memory 48a, and the memory 48a stores the initial position P1 in the vertical direction of the lower flange portion 46c measured by the two-dimensional CCD camera 47 and processed by the image processing apparatus.

このように構成されたＣＺ炉１０を用いてシリコン単結晶１１を引上げる方法を図２のフローチャート図に基づいて説明する。先ず室温でＣＺ炉１０を組立てる。このときＣＺ炉１０内の各部品は、ヒータ１９でルツボ１３内のシリコン融液１６を加熱することによる熱膨張を考慮して、設計・作製されて組立てられる。そしてＣＺ炉１０のメインチャンバ１２に収容されたルツボ１３にシリコン原料を入れる。このシリコン原料はシリコン多結晶又はシリコン単結晶のいずれか一方又は双方からなる。次いで上記ルツボ１３内のシリコン原料をヒータ１９で加熱して融解することにより、ルツボ１３にシリコン融液１６を貯留する。このシリコン融液１６から１本目のシリコン単結晶１１を引上げる直前に、熱遮蔽体４６のロアフランジ部４６ｃ上面の初回位置Ｐ１を２次元ＣＣＤカメラ４７により測定する。具体的には、２次元ＣＣＤカメラ４７によりロアフランジ部４６ｃを撮影し、この２次元ＣＣＤカメラ４７の撮影した画像を画像処理装置により処理することにより、ロアフランジ部４６ｃ上面の初回位置Ｐ１を測定する。コントローラ４８は、このロアフランジ部４６ｃ上面の初回位置Ｐ１をメモリ４８ａに記憶する。 A method of pulling up the silicon single crystal 11 using the CZ furnace 10 configured as described above will be described with reference to the flowchart of FIG. First, the CZ furnace 10 is assembled at room temperature. At this time, each component in the CZ furnace 10 is designed, fabricated and assembled in consideration of thermal expansion caused by heating the silicon melt 16 in the crucible 13 with the heater 19. Then, silicon raw material is put into the crucible 13 accommodated in the main chamber 12 of the CZ furnace 10. This silicon raw material is composed of one or both of silicon polycrystal and silicon single crystal. Next, the silicon raw material in the crucible 13 is heated and melted by the heater 19 to store the silicon melt 16 in the crucible 13. Immediately before pulling up the first silicon single crystal 11 from the silicon melt 16, the initial position P 1 on the upper surface of the lower flange portion 46 c of the heat shield 46 is measured by the two-dimensional CCD camera 47. Specifically, the lower flange portion 46c is photographed by the two-dimensional CCD camera 47, and the image photographed by the two-dimensional CCD camera 47 is processed by an image processing device, whereby the initial position P1 on the upper surface of the lower flange portion 46c is measured. The controller 48 stores the initial position P1 of the upper surface of the lower flange portion 46c in the memory 48a.

また、コントローラ４８は、上記ロアフランジ部４６ｃ上面の位置Ｐ１を基準として、水平磁場の中心位置３３をその設定位置に合せる。具体的には、コントローラ４８がコイル昇降モータ３８を駆動することにより、コイル昇降モータ３８の回転力が減速機３７で減速されてボールねじ３９に伝達される。このボールねじ３９の回転によりリング部材３６が昇降し、第１及び第２コイル３１，３２が昇降して、水平磁場の中心位置３３がその設定位置に合せられる。このときコイル昇降モータ３８はロータリエンコーダによりその回転角度が正確に検出されているため、水平磁場の中心位置３３をその設定位置に正確に合せることができる。更に、コントローラ４８は、ルツボ１３内のシリコン融液１６の表面位置と熱遮蔽体４６のロアフランジ部４６ｃ下面とのギャップが所定値になるように、ルツボ駆動装置１８によりルツボ１３を昇降させて調整する。そしてコントローラ４８は第１及び第２コイル３１，３２に通電してルツボ１３内のシリコン融液１６に水平磁場を印加する。この状態で１本目のシリコン単結晶１１を引上げる。そして所定長さのシリコン単結晶１１が引上げられると、シリコン単結晶１１の引上げは完了するので、シリコン単結晶１１の引上げを停止してＣＺ炉１０内を冷却した後に、シリコン単結晶１１をＣＺ炉１０から取出す。 The controller 48 adjusts the horizontal magnetic field center position 33 to the set position with reference to the position P1 on the upper surface of the lower flange portion 46c. Specifically, when the controller 48 drives the coil lifting / lowering motor 38, the rotational force of the coil lifting / lowering motor 38 is decelerated by the speed reducer 37 and transmitted to the ball screw 39. The ring member 36 is moved up and down by the rotation of the ball screw 39, the first and second coils 31 and 32 are moved up and down, and the center position 33 of the horizontal magnetic field is adjusted to the set position. At this time, since the rotation angle of the coil raising / lowering motor 38 is accurately detected by the rotary encoder, the center position 33 of the horizontal magnetic field can be accurately adjusted to the set position. Further, the controller 48 adjusts the crucible 13 by raising and lowering the crucible 13 with the crucible driving device 18 so that the gap between the surface position of the silicon melt 16 in the crucible 13 and the lower surface of the lower flange portion 46c of the heat shield 46 becomes a predetermined value. To do. The controller 48 energizes the first and second coils 31 and 32 to apply a horizontal magnetic field to the silicon melt 16 in the crucible 13. In this state, the first silicon single crystal 11 is pulled up. When the silicon single crystal 11 having a predetermined length is pulled up, the pulling of the silicon single crystal 11 is completed. Therefore, after the pulling of the silicon single crystal 11 is stopped and the inside of the CZ furnace 10 is cooled, the silicon single crystal 11 is moved to the CZ. Remove from furnace 10.

次に上記ＣＺ炉１０のルツボ１３に新たにシリコン原料を入れた後、このルツボ１３内のシリコン原料をヒータ１９で加熱して融解することにより、ルツボ１３にシリコン融液１６を貯留する。このシリコン融液１６から２本目のシリコン単結晶１１を引上げる直前に、熱遮蔽体４６のロアフランジ部４６ｃ上面の現在位置Ｐ２を２次元ＣＣＤカメラ４７により測定する。そして、コントローラ４８は、上記現在位置Ｐ２から初回位置Ｐ１を引いた値δを算出する。ここで、ロアフランジ部４６ｃ上面の現在位置Ｐ２が初回位置Ｐ１と異なるのは、次の理由に基づく。熱遮蔽体４６の上端であるアッパフランジ部４６ｂが、複数の円筒体２１〜２３を積重ねて形成された保温筒２０の上端に取付けられるため、ＣＺ炉１０内の加熱及び冷却の繰返しにより、熱遮蔽体４６や保温筒２０がＳｉＣ化したり或いは劣化する。このため保温筒２０の熱膨張量が次第に変化することにより、その上端位置が次第に上昇したり或いは下降し、これに伴って熱遮蔽体４６の位置も鉛直方向に変化するためである。 Next, after a silicon raw material is newly put into the crucible 13 of the CZ furnace 10, the silicon raw material in the crucible 13 is heated and melted by the heater 19 to store the silicon melt 16 in the crucible 13. Immediately before pulling up the second silicon single crystal 11 from the silicon melt 16, the current position P 2 on the upper surface of the lower flange portion 46 c of the heat shield 46 is measured by the two-dimensional CCD camera 47. Then, the controller 48 calculates a value δ obtained by subtracting the initial position P1 from the current position P2. Here, the reason why the current position P2 on the upper surface of the lower flange portion 46c is different from the initial position P1 is as follows. Since the upper flange portion 46b, which is the upper end of the heat shield 46, is attached to the upper end of the heat insulating cylinder 20 formed by stacking a plurality of cylindrical bodies 21 to 23, the heat and the cooling in the CZ furnace 10 are repeatedly performed. The shield 46 and the heat insulating cylinder 20 are changed to SiC or deteriorated. For this reason, the amount of thermal expansion of the heat retaining cylinder 20 gradually changes, so that the upper end position thereof gradually rises or falls, and accordingly, the position of the heat shield 46 also changes in the vertical direction.

コントローラ４８は、現在位置Ｐ２から初回位置Ｐ１を引いた値δ、即ち熱遮蔽体４６のロアフランジ部４６ｃ上面の鉛直方向へのずれ量δに応じて水平磁場の中心位置３３を鉛直方向に調整する。具体的には、コントローラ４８がコイル昇降モータ３８を駆動することにより、コイル昇降モータ３８の回転力が減速機３７を介してボールねじ３９に伝達されて、第１及び第２コイル３１，３２がリング部材３６とともに昇降する。これによりロアフランジ部４６ｃがずれた方向に上記ずれ量δだけ第１及び第２コイル３１，３２が鉛直方向にずれるので、水平磁場の中心位置３３のロアフランジ部４６ｃに対する鉛直方向の相対位置が所定値に保たれる。また、コントローラ４８は、ルツボ１３内のシリコン融液１６の表面位置と熱遮蔽体４６のロアフランジ部４６ｃ下面とのギャップが所定値になるように、ルツボ駆動装置１８によりルツボ１３を昇降させて調整する。そしてコントローラ４８は第１及び第２コイル３１，３２に通電してルツボ１３内のシリコン融液１６に水平磁場を印加する。この状態で２本目のシリコン単結晶１１を引上げる。そして所定長さのシリコン単結晶１１が引上げられると、シリコン単結晶１１の引上げは完了するので、シリコン単結晶１１の引上げを停止してＣＺ炉１０内を冷却した後に、シリコン単結晶１１をＣＺ炉１０から取出す。このように引上げられたシリコン単結晶１１は、熱遮蔽体４６の鉛直方向の位置が変化しても、水平磁場の中心位置３３及びシリコン融液１６の表面位置が、ロアフランジ部４６ｃの鉛直方向の位置のずれ量に応じて調整されるため、品質のバラツキを低減できる。 The controller 48 adjusts the horizontal magnetic field center position 33 in the vertical direction according to the value δ obtained by subtracting the initial position P1 from the current position P2, that is, the amount of shift δ in the vertical direction of the upper surface of the lower flange 46c of the heat shield 46. . Specifically, when the controller 48 drives the coil lifting / lowering motor 38, the rotational force of the coil lifting / lowering motor 38 is transmitted to the ball screw 39 via the speed reducer 37, and the first and second coils 31 and 32 are moved. It moves up and down together with the ring member 36. As a result, the first and second coils 31 and 32 are shifted in the vertical direction by the shift amount δ in the direction in which the lower flange portion 46c is shifted. Therefore, the vertical relative position of the horizontal magnetic field center position 33 to the lower flange portion 46c is a predetermined value. To be kept. Further, the controller 48 adjusts the crucible 13 by raising and lowering the crucible 13 with the crucible driving device 18 so that the gap between the surface position of the silicon melt 16 in the crucible 13 and the lower surface of the lower flange portion 46c of the heat shield 46 becomes a predetermined value. To do. The controller 48 energizes the first and second coils 31 and 32 to apply a horizontal magnetic field to the silicon melt 16 in the crucible 13. In this state, the second silicon single crystal 11 is pulled up. When the silicon single crystal 11 having a predetermined length is pulled up, the pulling of the silicon single crystal 11 is completed. Therefore, after the pulling of the silicon single crystal 11 is stopped and the inside of the CZ furnace 10 is cooled, the silicon single crystal 11 is moved to the CZ. Remove from furnace 10. Even if the vertical position of the heat shield 46 changes in the silicon single crystal 11 pulled up in this way, the horizontal magnetic field center position 33 and the surface position of the silicon melt 16 are in the vertical direction of the lower flange 46c. Since the adjustment is made according to the amount of positional deviation, the quality variation can be reduced.

また、表面の揺らぎによるバラツキが大きく、また表面がきらきら光ってしまい測定し難いシリコン融液１６の表面位置を基準として水平磁場の中心位置３３を制御するのではなく、鉛直方向の位置を測定し易い固体である熱遮蔽体４６のロアフランジ部４６ｃの鉛直方向の位置を測定しているため、このロアフランジ部４６ｃ上面の鉛直方向へのずれ量に応じて水平磁場の中心位置３３を精度良く調整することができる。この結果、シリコン単結晶１１の品質のバラツキを更に低減できる。 In addition, the center position 33 of the horizontal magnetic field is not controlled with reference to the surface position of the silicon melt 16 that is largely uneven due to surface fluctuations and the surface glitters and is difficult to measure, but the position in the vertical direction is measured. Since the vertical position of the lower flange portion 46c of the heat shield 46, which is an easy solid, is measured, the center position 33 of the horizontal magnetic field is accurately adjusted according to the amount of vertical displacement of the upper surface of the lower flange portion 46c. be able to. As a result, the quality variation of the silicon single crystal 11 can be further reduced.

一方、３本目以降のシリコン単結晶１１を引上げるときも、上記２本目のシリコン単結晶１１を引上げるときと同様に、ヒータ１９によりルツボ１３内のシリコン融液１６を加熱した状態であってＣＺ炉１０での３本目以降のシリコン単結晶１１の引上げ直前に、熱遮蔽体４６のロアフランジ部４６ｃの鉛直方向の位置を測定して、熱遮蔽体４６が初回位置Ｐ１から鉛直方向にずれた量を算出し、ロアフランジ部４６ｃの鉛直方向へのずれ量に応じて水平磁場の中心位置３３とシリコン融液１６の表面位置を鉛直方向にそれぞれ調整する。この結果、各バッチにおいて引上げられるシリコン単結晶１１の品質のバラツキを低減できる。 On the other hand, when the third and subsequent silicon single crystals 11 are pulled up, the silicon melt 16 in the crucible 13 is heated by the heater 19 in the same manner as when the second silicon single crystal 11 is pulled up. Immediately before the pulling of the third and subsequent silicon single crystals 11 in the CZ furnace 10, the vertical position of the lower flange portion 46 c of the thermal shield 46 was measured, and the thermal shield 46 was shifted from the initial position P 1 in the vertical direction. The amount is calculated, and the center position 33 of the horizontal magnetic field and the surface position of the silicon melt 16 are adjusted in the vertical direction according to the amount of displacement of the lower flange portion 46c in the vertical direction. As a result, variations in the quality of the silicon single crystal 11 pulled up in each batch can be reduced.

なお、上記実施の形態では、単結晶としてシリコン単結晶を挙げたが、ＧａＡｓ単結晶、ＩｎＰ単結晶、ＺｎＳ単結晶、ＺｎＳｅ単結晶等でもよい。また、上記実施の形態では、位置測定具として２次元ＣＣＤカメラを挙げたが、位置測定具はレーザ光や計測治具（例えば変位センサ）等でもよい。また、上記実施の形態では、熱遮蔽体のロアフランジ部の鉛直方向の位置を測定したが、熱遮蔽体のアッパフランジ部又は円筒部の鉛直方向の位置を測定してもよい。但し、熱遮蔽体の測定位置は、熱膨張による誤差が小さくなるため、シリコン融液の表面に近い位置で測定した方が好ましい。また、上記実施の形態では、一つのルツボを用いて１本のシリコン単結晶を引上げた後、チャンバ内を冷却してシリコン単結晶を取出し、チャンバ内を冷却した状態で上記ルツボに再びシリコン原料を供給して別のシリコン単結晶を引上げるバッチ引上げ処理におけるバッチ間に本発明を適用したが、一つのルツボを用いて１本のシリコン単結晶を引上げた後に、チャンバ内を冷却せずにシリコン単結晶を取出し、チャンバ内を加熱した状態でルツボに再びシリコン原料を供給して別のシリコン単結晶を引上げるマルチ引上げ処理におけるシリコン単結晶の引上げ処理の間に本発明を適用してもよい。更に、上記実施の形態では、バッチ毎に水平磁場の中心位置を鉛直方向に調整したが、単結晶の引上げ中であっても所定時間毎に水平磁場の中心位置を鉛直方向に調整してもよい。 In the above embodiment, a silicon single crystal is used as the single crystal. However, a GaAs single crystal, an InP single crystal, a ZnS single crystal, a ZnSe single crystal, or the like may be used. In the above embodiment, the two-dimensional CCD camera is used as the position measuring tool. However, the position measuring tool may be a laser beam, a measuring jig (for example, a displacement sensor), or the like. Moreover, in the said embodiment, although the position of the vertical direction of the lower flange part of a heat shield was measured, you may measure the position of the vertical direction of the upper flange part or cylindrical part of a heat shield. However, the measurement position of the thermal shield is preferably measured at a position close to the surface of the silicon melt because errors due to thermal expansion are reduced. Further, in the above embodiment, after pulling up one silicon single crystal using one crucible, the inside of the chamber is cooled to take out the silicon single crystal, and the silicon raw material is again put into the crucible while the inside of the chamber is cooled. The present invention was applied between batches in a batch pulling process in which another silicon single crystal was pulled by supplying a single silicon crystal, but after one silicon single crystal was pulled using one crucible, the inside of the chamber was not cooled. Even if the present invention is applied during the pulling process of the silicon single crystal in the multi-pulling process in which the silicon single crystal is taken out, the silicon raw material is supplied again to the crucible while the chamber is heated, and another silicon single crystal is pulled up. Good. Furthermore, in the above embodiment, the center position of the horizontal magnetic field is adjusted in the vertical direction for each batch, but even if the single crystal is being pulled up, the center position of the horizontal magnetic field can be adjusted in the vertical direction every predetermined time. Good.

次に本発明の実施例を比較例とともに詳しく説明する。 Next, examples of the present invention will be described in detail together with comparative examples.

＜実施例１＞
図１に示すＣＺ炉１０を用い、図２に示すフローチャート図に基づいてシリコン単結晶１１を引上げた。具体的には、先ずＣＺ炉１０のメインチャンバ１２に収容されたルツボ１３に３６０ｋｇのシリコン原料を入れた。次いで上記ルツボ１３内のシリコン原料をヒータ１９で加熱して融解しシリコン融液１６にした。このシリコン融液１６から１本目のシリコン単結晶１１を引上げる直前に、熱遮蔽体４６のロアフランジ部４６ｃ上面のメインチャンバ１２に対する鉛直方向の位置である熱遮蔽体４６の初回位置Ｐ１を２次元ＣＣＤカメラ４７により測定し、このロアフランジ部４６ｃ上面の初回位置Ｐ１をメモリ４８ａに記憶した。また、コントローラ４８は、上記ロアフランジ部４６ｃ上面の位置Ｐ１を基準として、水平磁場の中心位置３３をその設定位置に合せた。更に、コントローラ４８は、ルツボ１３内のシリコン融液１６の表面位置と熱遮蔽体４６のロアフランジ部４６ｃ下面とのギャップが４０ｍｍになるように、ルツボ駆動装置１８によりルツボ１３を昇降させて調整した。そしてコントローラ４８は第１及び第２コイル３１，３２に通電してルツボ１３内のシリコン融液１６に水平磁場を印加し、全長が１８００ｍｍであって直胴部の直径が３００ｍｍである１本目のシリコン単結晶１１を引上げた。ここで、熱遮蔽体４６のロアフランジ部４６ｃの内周縁とシリコン単結晶１１の外周面との距離は３０ｍｍであった。 <Example 1>
The CZ furnace 10 shown in FIG. 1 was used to pull up the silicon single crystal 11 based on the flowchart shown in FIG. Specifically, first, 360 kg of silicon raw material was put in the crucible 13 accommodated in the main chamber 12 of the CZ furnace 10. Next, the silicon raw material in the crucible 13 was heated and melted by the heater 19 to obtain a silicon melt 16. Immediately before pulling up the first silicon single crystal 11 from the silicon melt 16, the initial position P1 of the heat shield 46, which is the position in the vertical direction with respect to the main chamber 12 on the upper surface of the lower flange portion 46c of the heat shield 46, is two-dimensional. The measurement was performed by the CCD camera 47, and the initial position P1 of the upper surface of the lower flange portion 46c was stored in the memory 48a. The controller 48 matched the center position 33 of the horizontal magnetic field with the set position with reference to the position P1 on the upper surface of the lower flange portion 46c. Further, the controller 48 adjusts the crucible 13 by raising and lowering the crucible 13 with the crucible driving device 18 so that the gap between the surface position of the silicon melt 16 in the crucible 13 and the lower surface of the lower flange portion 46c of the heat shield 46 becomes 40 mm. . Then, the controller 48 energizes the first and second coils 31 and 32 to apply a horizontal magnetic field to the silicon melt 16 in the crucible 13, and has a total length of 1800 mm and a straight body having a diameter of 300 mm. The silicon single crystal 11 was pulled up. Here, the distance between the inner peripheral edge of the lower flange portion 46c of the heat shield 46 and the outer peripheral surface of the silicon single crystal 11 was 30 mm.

次に上記ＣＺ炉１０のルツボ１３に新たに３６０ｋｇのシリコン原料を入れた後、このルツボ１３内のシリコン原料をヒータ１９で加熱して融解しシリコン融液にした。このシリコン融液１６から２本目のシリコン単結晶１１を引上げる直前に、熱遮蔽体４６のロアフランジ部４６ｃ上面の現在位置Ｐ２を２次元ＣＣＤカメラ４７により測定した。そして、コントローラ４８は、上記現在位置Ｐ２から初回位置Ｐ１を引いた値δ（上方に１ｍｍ）を算出し、ロアフランジ部４６ｃがずれた方向に上記ずれ量δ（上方に１ｍｍ）だけ第１及び第２コイル３１，３２を鉛直方向にずらした。これにより水平磁場の中心位置３３のロアフランジ部４６ｃに対する鉛直方向の相対位置を所定値に保った。また、コントローラ４８は、ルツボ１３内のシリコン融液１６の表面位置と熱遮蔽体４６のロアフランジ部４６ｃ下面とのギャップが４０ｍｍになるように、ルツボ駆動装置１８によりルツボ１３を昇降させて調整した。そしてコントローラ４８は第１及び第２コイル３１，３２に通電してルツボ１３内のシリコン融液１６に水平磁場を印加し、全長が１８００ｍｍであって直胴部の直径が３００ｍｍである２本目のシリコン単結晶１１を引上げた。この２本目のシリコン単結晶１１を実施例１とした。なお、熱遮蔽体４６のロアフランジ部４６ｃの内周縁とシリコン単結晶１１の外周面との距離は３０ｍｍであった。 Next, after 360 kg of silicon raw material was newly added to the crucible 13 of the CZ furnace 10, the silicon raw material in the crucible 13 was heated and melted by the heater 19 to form a silicon melt. Immediately before pulling up the second silicon single crystal 11 from the silicon melt 16, the current position P <b> 2 on the upper surface of the lower flange portion 46 c of the heat shield 46 was measured by the two-dimensional CCD camera 47. Then, the controller 48 calculates a value δ (1 mm upward) obtained by subtracting the initial position P1 from the current position P2, and the first and first shifts δ (1 mm upward) in the direction in which the lower flange portion 46c is displaced. The two coils 31, 32 were shifted in the vertical direction. As a result, the vertical relative position of the horizontal magnetic field center position 33 to the lower flange portion 46c was kept at a predetermined value. Further, the controller 48 adjusts the crucible 13 by moving it up and down with the crucible driving device 18 so that the gap between the surface position of the silicon melt 16 in the crucible 13 and the lower surface of the lower flange portion 46c of the heat shield 46 becomes 40 mm. . Then, the controller 48 energizes the first and second coils 31 and 32 to apply a horizontal magnetic field to the silicon melt 16 in the crucible 13, and has a total length of 1800 mm and a straight body having a diameter of 300 mm. The silicon single crystal 11 was pulled up. This second silicon single crystal 11 was taken as Example 1. The distance between the inner peripheral edge of the lower flange portion 46c of the heat shield 46 and the outer peripheral surface of the silicon single crystal 11 was 30 mm.

＜実施例２＞
熱遮蔽体のロアフランジ部下面とシリコン融液表面との距離を７０ｍｍとしたこと以外は、実施例１と同様にして、全長が１８００ｍｍであって直胴部の直径が３００ｍｍである１本目及び２本目のシリコン単結晶を順次引上げた。２本目のシリコン単結晶を実施例２とした。 <Example 2>
In the same manner as in Example 1, except that the distance between the lower surface of the lower flange portion of the heat shield and the surface of the silicon melt was set to 70 mm, the first and second ones having a total length of 1800 mm and a straight body portion having a diameter of 300 mm The first silicon single crystal was pulled up sequentially. The second silicon single crystal was taken as Example 2.

＜実施例３＞
熱遮蔽体のロアフランジ部の内周縁と引上げ中のシリコン単結晶の外周面との距離を５０ｍｍとしたこと以外は、実施例１と同様にして、全長が１８００ｍｍであって直胴部の直径が３００ｍｍである１本目及び２本目のシリコン単結晶を順次引上げた。２本目のシリコン単結晶を実施例３とした。 <Example 3>
Except that the distance between the inner peripheral edge of the lower flange portion of the heat shield and the outer peripheral surface of the silicon single crystal being pulled was 50 mm, the total length was 1800 mm and the diameter of the straight body portion was the same as in Example 1. The first and second silicon single crystals of 300 mm were pulled up sequentially. The second silicon single crystal was taken as Example 3.

＜実施例４＞
先ず実施例１と同様にして、１本目のシリコン単結晶１１を引上げた。次にＣＺ炉１０のルツボ１３に新たに３６０ｋｇのシリコン原料を入れた後、このルツボ１３内のシリコン原料をヒータ１９で加熱して融解しシリコン融液にした。このシリコン融液１６から２本目のシリコン単結晶１１を引上げる直前に、熱遮蔽体４６のロアフランジ部４６ｃ上面の現在位置Ｐ２を２次元ＣＣＤカメラ４７により測定した。そして、コントローラ４８は、上記現在位置Ｐ２から初回位置Ｐ１を引いた値δ（上方に２ｍｍ）を算出し、ロアフランジ部４６ｃがずれた方向に上記ずれ量δ（上方に２ｍｍ）だけ第１及び第２コイル３１，３２を鉛直方向にずらした。これにより水平磁場の中心位置３３のロアフランジ部４６ｃに対する鉛直方向の相対位置を所定値に保った。また、コントローラ４８は、ルツボ１３内のシリコン融液１６の表面位置と熱遮蔽体４６のロアフランジ部４６ｃ下面とのギャップが４０ｍｍになるように、ルツボ駆動装置１８によりルツボ１３を昇降させて調整した。そしてコントローラ４８は第１及び第２コイル３１，３２に通電してルツボ１３内のシリコン融液１６に水平磁場を印加し、全長が１８００ｍｍであって直胴部の直径が３００ｍｍである２本目のシリコン単結晶１１を引上げた。この２本目のシリコン単結晶１１を実施例４とした。なお、熱遮蔽体４６のロアフランジ部４６ｃの内周縁とシリコン単結晶１１の外周面との距離は３０ｍｍであった。 <Example 4>
First, in the same manner as in Example 1, the first silicon single crystal 11 was pulled up. Next, after 360 kg of silicon raw material was newly added to the crucible 13 of the CZ furnace 10, the silicon raw material in the crucible 13 was heated and melted by the heater 19 to form a silicon melt. Immediately before pulling up the second silicon single crystal 11 from the silicon melt 16, the current position P <b> 2 on the upper surface of the lower flange portion 46 c of the heat shield 46 was measured by the two-dimensional CCD camera 47. Then, the controller 48 calculates a value δ (2 mm upward) obtained by subtracting the initial position P1 from the current position P2, and the first and first shifts δ (2 mm upward) in the direction in which the lower flange portion 46c is displaced. The two coils 31, 32 were shifted in the vertical direction. As a result, the vertical relative position of the horizontal magnetic field center position 33 to the lower flange portion 46c was kept at a predetermined value. Further, the controller 48 adjusts the crucible 13 by moving it up and down with the crucible driving device 18 so that the gap between the surface position of the silicon melt 16 in the crucible 13 and the lower surface of the lower flange portion 46c of the heat shield 46 becomes 40 mm. . Then, the controller 48 energizes the first and second coils 31 and 32 to apply a horizontal magnetic field to the silicon melt 16 in the crucible 13, and has a total length of 1800 mm and a straight body having a diameter of 300 mm. The silicon single crystal 11 was pulled up. This second silicon single crystal 11 was taken as Example 4. The distance between the inner peripheral edge of the lower flange portion 46c of the heat shield 46 and the outer peripheral surface of the silicon single crystal 11 was 30 mm.

＜実施例５＞
熱遮蔽体のロアフランジ部下面とシリコン融液表面との距離を７０ｍｍとしたこと以外は、実施例４と同様にして、全長が１８００ｍｍであって直胴部の直径が３００ｍｍである１本目及び２本目のシリコン単結晶を順次引上げた。２本目のシリコン単結晶を実施例５とした。 <Example 5>
In the same manner as in Example 4 except that the distance between the lower surface of the lower flange portion of the heat shield and the surface of the silicon melt was set to 70 mm, the first and second ones having an overall length of 1800 mm and a straight body portion of 300 mm in diameter. The first silicon single crystal was pulled up sequentially. The second silicon single crystal was taken as Example 5.

＜実施例６＞
熱遮蔽体のロアフランジ部の内周縁と引上げ中のシリコン単結晶の外周面との距離を５０ｍｍとしたこと以外は、実施例１と同様にして、全長が１８００ｍｍであって直胴部の直径が３００ｍｍである１本目及び２本目のシリコン単結晶を順次引上げた。２本目のシリコン単結晶を実施例６とした。 <Example 6>
Except that the distance between the inner peripheral edge of the lower flange portion of the heat shield and the outer peripheral surface of the silicon single crystal being pulled was 50 mm, the total length was 1800 mm and the diameter of the straight body portion was the same as in Example 1. The first and second silicon single crystals of 300 mm were pulled up sequentially. The second silicon single crystal was taken as Example 6.

＜比較例１＞
２本目のシリコン単結晶を引上げる直前に、熱遮蔽体のロアフランジ部上面の現在位置Ｐ２が初回位置Ｐ１からずれていても、熱遮蔽体の鉛直方向の位置を調整しなかったこと以外は、実施例１と同様にして、全長が１８００ｍｍであって直胴部の直径が３００ｍｍである１本目及び２本目のシリコン単結晶を順次引上げた。２本目のシリコン単結晶を比較例１とした。 <Comparative Example 1>
Immediately before pulling up the second silicon single crystal, even if the current position P2 of the upper surface of the lower flange portion of the heat shield is deviated from the initial position P1, the vertical position of the heat shield is not adjusted. In the same manner as in Example 1, the first and second silicon single crystals having a total length of 1800 mm and a diameter of the straight body portion of 300 mm were sequentially pulled up. The second silicon single crystal was designated as Comparative Example 1.

＜比較例２＞
２本目のシリコン単結晶を引上げる直前に、熱遮蔽体のロアフランジ部上面の現在位置Ｐ２が初回位置Ｐ１からずれていても、熱遮蔽体の鉛直方向の位置を調整しなかったこと以外は、実施例１と同様にして、全長が１８００ｍｍであって直胴部の直径が３００ｍｍである１本目及び２本目のシリコン単結晶を順次引上げた。２本目のシリコン単結晶を比較例２とした。 <Comparative example 2>
Immediately before pulling up the second silicon single crystal, even if the current position P2 of the upper surface of the lower flange portion of the heat shield is deviated from the initial position P1, the vertical position of the heat shield is not adjusted. In the same manner as in Example 1, the first and second silicon single crystals having a total length of 1800 mm and a diameter of the straight body portion of 300 mm were sequentially pulled up. The second silicon single crystal was designated as Comparative Example 2.

＜比較例３＞
熱遮蔽体のロアフランジ部の内周縁と引上げ中のシリコン単結晶の外周面との距離を５０ｍｍとしたこと以外は、比較例１と同様にして、全長が１８００ｍｍであって直胴部の直径が３００ｍｍである１本目及び２本目のシリコン単結晶を順次引上げた。２本目のシリコン単結晶を比較例３とした。 <Comparative Example 3>
Except that the distance between the inner peripheral edge of the lower flange part of the heat shield and the outer peripheral surface of the silicon single crystal being pulled was 50 mm, the total length was 1800 mm and the diameter of the straight body part was the same as in Comparative Example 1. The first and second silicon single crystals of 300 mm were pulled up sequentially. The second silicon single crystal was designated as Comparative Example 3.

＜比較試験１及び評価＞
実施例１〜６及び比較例１〜３のシリコン単結晶の製品ロスを測定した。具体的には、各シリコン単結晶の直胴部において、無欠陥とならなかった部分、即ちＣＯＰ若しくは転位クラスタが存在する部分の体積を測定し、シリコン単結晶の直胴部全体を１００質量％とするときの上記無欠陥とならなかった部分の体積割合を算出した。その結果を表１に示す。なお、表１において、「調整量」とは、２本目のシリコン単結晶を引上げる直前に、熱遮蔽体のロアフランジ部上面の現在位置Ｐ２から初回位置Ｐ１を引いた値δだけ、ロアフランジ部４６ｃがずれた方向に第１及び第２コイル３１，３２を鉛直方向にずらした量である。また、表１において、「熱遮蔽体−液面」とは、熱遮蔽体のロアフランジ部下面とシリコン融液の表面との距離であり、「熱遮蔽体−単結晶」とは、熱遮蔽体のロアフランジ部内周面と引上げ中のシリコン単結晶の外周面との距離である。 <Comparative test 1 and evaluation>
The product loss of the silicon single crystals of Examples 1 to 6 and Comparative Examples 1 to 3 was measured. Specifically, in the straight body portion of each silicon single crystal, the volume of the portion that was not defect-free, that is, the portion where COP or dislocation cluster exists was measured, and the entire straight body portion of the silicon single crystal was 100% by mass. The volume ratio of the portion that was not free of defects was calculated. The results are shown in Table 1. In Table 1, “adjustment amount” means the lower flange portion 46c by a value δ obtained by subtracting the initial position P1 from the current position P2 on the upper surface of the lower flange portion of the heat shield immediately before pulling up the second silicon single crystal. This is the amount by which the first and second coils 31 and 32 are shifted in the vertical direction in the direction in which they are shifted. In Table 1, “thermal shield-liquid level” is the distance between the lower surface of the lower flange portion of the thermal shield and the surface of the silicon melt, and “thermal shield-single crystal” is the thermal shield. The distance between the inner peripheral surface of the lower flange portion and the outer peripheral surface of the silicon single crystal being pulled.

表１から明らかなように、２本目のシリコン単結晶を引上げる直前における調整量が０ｍｍである比較例１〜３では、即ち２本目のシリコン単結晶を引上げる直前に、熱遮蔽体のロアフランジ部上面の現在位置Ｐ２が初回位置Ｐ１からずれていても、熱遮蔽体の鉛直方向の位置を調整しなかった比較例１〜３では、製品ロスが３．０〜５．０質量％と多かった。これらに対し、２本目のシリコン単結晶を引上げる直前における調整量が１ｍｍ又は２ｍｍである実施例１〜６では、即ち２本目のシリコン単結晶を引上げる直前に、熱遮蔽体のロアフランジ部上面の現在位置Ｐ２から初回位置Ｐ１を引いた値δ（１ｍｍ又は２ｍｍ）を算出し、ロアフランジ部がずれた方向に上記ずれ量δ（１ｍｍ又は２ｍｍ）だけ第１及び第２コイルを鉛直方向にずらした実施例１〜６では、製品ロスが１．５〜２．１質量％と少なくなった。 As is apparent from Table 1, in Comparative Examples 1 to 3 in which the adjustment amount immediately before pulling up the second silicon single crystal is 0 mm, that is, immediately before pulling up the second silicon single crystal, the lower flange of the heat shield In Comparative Examples 1 to 3, in which the vertical position of the heat shield was not adjusted even if the current position P2 on the top surface of the part was shifted from the initial position P1, the product loss was as high as 3.0 to 5.0% by mass. It was. In contrast, in Examples 1 to 6 in which the adjustment amount immediately before pulling up the second silicon single crystal is 1 mm or 2 mm, that is, immediately before pulling up the second silicon single crystal, the upper surface of the lower flange portion of the heat shield The value δ (1 mm or 2 mm) obtained by subtracting the initial position P1 from the current position P2 is calculated, and the first and second coils are shifted in the vertical direction by the above-mentioned deviation amount δ (1 mm or 2 mm) in the direction in which the lower flange portion is displaced. In Examples 1 to 6, the product loss was reduced to 1.5 to 2.1% by mass.

一方、熱遮蔽体−液面、即ち熱遮蔽体のロアフランジ部下面とシリコン融液の表面との距離が４０ｍｍと小さく、かつ熱遮蔽体−単結晶、即ち熱遮蔽体のロアフランジ部内周面と引上げ中のシリコン単結晶の外周面との距離が３０ｍｍと小さい場合、比較例１の製品ロスに対する実施例１の製品ロスの減少割合は１．５／３．０＝０．５と比較的少なく、比較例１の製品ロスに対する実施例２の製品ロスの減少割合は１．２／３．０＝０．４と比較的少なかった。これらに対し、熱遮蔽体−単結晶、即ち熱遮蔽体のロアフランジ部内周面と引上げ中のシリコン単結晶の外周面との距離が３０ｍｍと上記の場合と同一であるけれども、熱遮蔽体−液面、即ち熱遮蔽体のロアフランジ部下面とシリコン融液の表面との距離が７０ｍｍと大きい場合、比較例２の製品ロスに対する実施例２の製品ロスの減少割合は１．８／４．５＝０．４と上記比較例１の製品ロスに対する実施例１の製品ロスの減少割合より多くなり、比較例２の製品ロスに対する実施例５の製品ロスの減少割合は１．３／４．５≒０．２２と上記比較例１の製品ロスに対する実施例４の製品ロスの減少割合より多くなった。また、熱遮蔽体−液面、即ち熱遮蔽体のロアフランジ部下面とシリコン融液の表面との距離が４０ｍｍと上記の場合と同一であるけれども、熱遮蔽体−単結晶、即ち熱遮蔽体のロアフランジ部内周面と引上げ中のシリコン単結晶の外周面との距離が５０ｍｍと大きい場合、比較例３の製品ロスに対する実施例４の製品ロスの減少割合は２．１／５．０＝０．４２と上記比較例１の製品ロスに対する実施例１の製品ロスの減少割合より多くなり、比較例３の製品ロスに対する実施例６の製品ロスの減少割合は１．５／５．０≒０．３と上記比較例１の製品ロスに対する実施例４の製品ロスの減少割合より多くなった。上述のことから、熱遮蔽体−液面、即ち熱遮蔽体のロアフランジ部下面とシリコン融液の表面との距離を７０ｍｍと大きくしたり、或いは熱遮蔽体−単結晶、即ち熱遮蔽体のロアフランジ部内周面と引上げ中のシリコン単結晶の外周面との距離を５０ｍｍと大きくすると、製品ロスの減少割合が大きくなることが分かった。 On the other hand, the distance between the heat shield-liquid surface, that is, the lower surface of the lower flange portion of the heat shield and the surface of the silicon melt is as small as 40 mm, and the heat shield-single crystal, that is, the inner peripheral surface of the lower flange portion of the heat shield is pulled up. When the distance from the outer peripheral surface of the silicon single crystal in the inside is as small as 30 mm, the reduction rate of the product loss of Example 1 with respect to the product loss of Comparative Example 1 is relatively small as 1.5 / 3.0 = 0.5, The reduction rate of the product loss of Example 2 with respect to the product loss of Comparative Example 1 was relatively small, 1.2 / 3.0 = 0.4. On the other hand, although the distance between the heat shield-single crystal, that is, the inner peripheral surface of the lower flange portion of the heat shield and the outer peripheral surface of the silicon single crystal being pulled is the same as the above case, the heat shield-liquid When the distance between the surface, that is, the lower surface of the lower flange portion of the heat shield and the surface of the silicon melt is as large as 70 mm, the reduction ratio of the product loss of Example 2 to the product loss of Comparative Example 2 is 1.8 / 4.5 = 0.4, which is higher than the product loss reduction rate of Example 1 with respect to the product loss of Comparative Example 1, and the product loss reduction rate of Example 5 with respect to the product loss of Comparative Example 2 is 1.3 / 4.5≈ 0.22 and the reduction rate of the product loss of Example 4 with respect to the product loss of Comparative Example 1 was larger. Further, although the distance between the heat shield-liquid level, that is, the lower surface of the lower flange portion of the heat shield and the surface of the silicon melt is 40 mm, which is the same as the above case, the heat shield-single crystal, that is, the heat shield When the distance between the inner peripheral surface of the lower flange portion and the outer peripheral surface of the silicon single crystal being pulled is as large as 50 mm, the reduction rate of the product loss of Example 4 relative to the product loss of Comparative Example 3 is 2.1 / 5.0 = 0. 42 and the product loss reduction rate of Example 1 with respect to the product loss of Comparative Example 1, and the product loss reduction rate of Example 6 to the product loss of Comparative Example 3 is 1.5 / 5.0≈0. 3 and the reduction rate of the product loss of Example 4 with respect to the product loss of Comparative Example 1 was larger. From the above, the distance between the heat shield-liquid level, that is, the lower surface of the lower flange portion of the heat shield and the surface of the silicon melt is increased to 70 mm, or the heat shield-single crystal, ie, the lower flange of the heat shield. It has been found that when the distance between the inner peripheral surface of the part and the outer peripheral surface of the silicon single crystal being pulled is increased to 50 mm, the reduction rate of the product loss increases.

１０ＣＺ炉
１１シリコン単結晶（単結晶）
１２メインチャンバ（チャンバ）
１３ルツボ
１６シリコン融液（融液）
１９ヒータ
２０保温筒
２４プルチャンバ（チャンバ） 10 CZ furnace 11 Silicon single crystal (single crystal)
12 Main chamber (chamber)
13 Crucible 16 Silicon melt (melt)
19 Heater 20 Thermal insulation cylinder 24 Pull chamber (chamber)

Claims

A step of putting a raw material in a crucible housed in a chamber of a CZ furnace, a step of heating the raw material in the crucible with a heater and storing a melt in the crucible, and a horizontal magnetic field applied to the melt in the crucible A single crystal in a state where a heat shield positioned above the melt surface surrounds the outer peripheral surface of the single crystal pulled up from the melt and blocks the irradiation of radiant heat to the outer peripheral surface of the single crystal by a heater In the method of pulling up
Before the first single crystal is pulled in the CZ furnace in a state in which the melt in the crucible is heated by the heater, the first time of the thermal shield is the vertical position of the thermal shield with respect to the chamber. Measuring the position;
Matching the center position of the horizontal magnetic field to the set position with reference to the initial position of the thermal shield;
While the melt in the crucible is heated by the heater and before or during the pulling of the second and subsequent single crystals in the CZ furnace, the vertical position of the thermal shield is measured to measure the heat Calculating the amount that the shield is displaced in the vertical direction from the initial position;
And a step of adjusting a center position of the horizontal magnetic field in a vertical direction according to a deviation amount of the thermal shield in a vertical direction.

The method for pulling a single crystal according to claim 1, wherein the distance between the lower surface of the lower end of the heat shield and the surface of the melt is in the range of 70 to 150 mm.

When the inner diameter of the upper part of the crucible is d ₁ mm, the diameter of the straight body of the single crystal being pulled is d ₂ mm, and the radial thickness of the lower end of the heat shield is tmm, the heat The single unit according to claim 1 or 2, wherein the distance between the inner peripheral surface of the lower end portion of the shield and the outer peripheral surface of the single crystal being pulled is 50 mm or more and [(d ₁ -d ₂ -2t) / 2] mm or less. Crystal pulling method.