JP3597003B2

JP3597003B2 - Vapor phase growth apparatus and vapor phase growth method

Info

Publication number: JP3597003B2
Application number: JP35438196A
Authority: JP
Inventors: 忠大橋; 勝弘茶木; 平辛; 達男藤井; 勝行岩田; 慎一三谷; 恭章本多
Original assignee: Toshiba Machine Co Ltd
Current assignee: Shibaura Machine Co Ltd
Priority date: 1996-12-19
Filing date: 1996-12-19
Publication date: 2004-12-02
Anticipated expiration: 2016-12-19
Also published as: JPH10177960A

Description

【０００１】
【発明の属する技術分野】
本発明は気相成長装置及び気相成長方法に関し、詳しくは高品質が要求される半導体ウエハ基板の製造工程に適用される気相中のパーティクル及び炉壁への析出物の発生が少なく、均一な膜厚の薄膜が形成され、抵抗値のばらつきが無く均質で結晶欠陥の少ない半導体ウエハ基板が得られる気相成長装置及び気相成長方法に関する。
【０００２】
【従来の技術】
図７は、従来の気相成長装置の一例を示す概略説明図（Ａ）及びその装置内の（Ａ）に示した所定位置Ｂ、Ｃ及びＤにおけるそれぞれの垂直方向のガス流速分布図（Ｂ）、（Ｃ）及び（Ｄ）である。なお、（Ａ）中の矢印付きの線分は、装置内のガス流を模式的に示したガス流線図である。図７（Ａ）において、一般に円筒状の反応炉７１内の下部には、例えばシリコンウエハ等のウエハ基板Ｗを載置する回転基板ホルダー７２、回転基板ホルダー７２を回転させるための回転軸７３及び加熱用のヒータ７４が配設され、回転軸７３には回転駆動するモータ（図示せず）が接続されている。また、反応炉７１底部には未反応ガス等を排気する複数の排気口７５、７５が配設されて排気制御装置（図示せず）に接続されている。一方、反応炉７１の頂部には炉内に原料ガスやキャリアガスの反応ガスを供給する複数のガス供給管７６、７６と円盤状の整流板７７とが配設され、整流板７７には、ガスの流れを整える多数の孔７７ａが穿設されている。従来の気相成長装置は上記のように構成され、モータの回転駆動によって所定の回転数で回転する回転基板ホルダー７２上に載置された基板Ｗは、回転しながらヒータ７４により所定温度に加熱される。同時に、反応炉７１内には原料ガスやキャリアガス等の反応ガスを複数のガス供給管７６、７６を介して導入しガス運動量や圧力分布を均一化し、次いで反応炉内のガス流速分布が均一になるように整流板７７の多数の孔７７ａを通過させ、回転基板ホルダー７２上のウエハ基板Ｗに反応ガスを均一に供給して薄膜を気相成長させている。
【０００３】
上記したような半導体ウエハ上へ薄膜を形成する気相成長装置においては、薄膜形成ガスによるパーティクルの発生や反応炉内壁への析出物の付着を防止するため、また、薄膜形成時の不都合により結晶欠陥が生じないようにして薄膜が均質で且つ膜厚が均一な薄膜形成ウエハが得られるように各種の提案がなされている。例えば、特開平５−７４７１９号公報では原料ガスの供給流量を所定に制御して反応炉内の温度変化を防止することにより結晶欠陥の防止を図っている。特開平５−９０１６７号公報では薄膜形成時のウエハ基板の面内温度分布を均一にするように原料ガス量、炉内圧力、回転基板ホルダの回転数等を所定に制御してスリップの防止を図っている。特開平６−２１６０４５号公報では析出物が生じ易い反応炉内壁の一部に内周面を平滑に維持して遮蔽管を配設し、薄膜形成操作を行った後の反応炉洗浄を容易にすると共に、ガス流を層流状態に維持して均質な薄膜の形成を図るものである。また、特開平７−５０２６０号公報では、反応炉上部に複数の孔を有する整流板上への原料ガスやキャリアガスの導入を複数の供給管を介して行うと共に流入方向を所定にすることにより、ガス運動量やガス圧を均一にして均一な流速で原料ガス等を基板上に供給して薄膜厚の均一化を図るものである。
【０００４】
【発明が解決しようとする課題】
しかしながら、上記の各種提案の従来の気相成長装置においても、薄膜成長させたウエハ基板で、結晶欠陥が生じたり、パーティクル付着等の不都合が十分に防止できるまでには到っていない。また、特に近年の半導体における超高集積化に伴い、ウエハ基板は、ますます高品質化が要求されるようになったことから、薄膜形成ウエハ基板の僅かな欠陥の品質低下も問題になることが多くなっている。本発明は、このような従来の気相成長装置による気相成長薄膜形成でのウエハ基板の品質低下に鑑み、それらを解決する目的でなされたものである。発明者らは、先ず、従来の気相成長装置で生じている現象について詳細に検討した。その結果、反応炉壁にパーティクルが多く付着する現象が観察され、そのため、メンテナンスサイクルを短縮させたり、この反応炉壁に付着したパーティクルが、ウエハ基板に付着し結晶欠陥の原因となったり、付着パーティクルとして直接にウエハ品質の低下をもたらす原因となっていることを知見した。
【０００５】
発明者らは、上記知見から、更に、反応炉壁でのパーティクル多量付着現象の原因を見出すべく、反応炉内での原料ガス流れ等を検討した。その結果、下記する現象が反応炉内で生じることが更に明らかになった。即ち、▲１▼上記図７に示した従来の反応炉７１において、シリコン原料ガス等の反応ガスは頂部より導入され均一な流速でウエハ基板Ｗ上に供給され薄膜形成に供されると同時に、反応炉下部がヒータ７４で加熱されていることから、ウエハ基板Ｗ近傍に到達した反応ガスも加熱昇温される。その結果、図７の（Ａ）のガス流線図、また（Ｂ）、（Ｃ）及び（Ｄ）の流速分布で示したように、炉内（Ｂ）域ではガスはほぼ均一な流速で流下するが、（Ｃ）域では炉内周壁付近でガス流速が低下し、（Ｄ）域では反応炉内周壁に沿ってガス流が上昇流に転じる。このため、反応ガスの舞上り現象が生じ、ガス渦流の発生が起こる。▲２▼また、加温された反応ガスが上昇することから、反応炉７１内全域の温度も上昇し気相中での薄膜形成原料ガスの均一核生成が増大し、気相中でのパーティクル発生が増大する。▲３▼更に、上記ガス渦流が発生すると、回転基板ホルダー７２上のウエハ基板Ｗの外周部で反応ガス中のドーパントの再取込が起こるおそれがあり、得られるウエハ基板の面内抵抗値分布の不均一化の原因ともなる。
【０００６】
上記した各種の不都合を引き起こすガス渦流の発生は、従来の反応炉において、回転基板保持体の軸方向へのガス流速を約１ｍ／ｓ以上の極めて速くすることである程度は抑制できる。しかし、そのためには大量のキャリアガスを流す必要があり、工業的には実用性に乏しいものとなる。このため、発明者らは前記した薄層形成ウエハ基板の品質低下や反応炉のメンテナンスサイクルの短期化等の不都合の原因が、主に反応炉内でのガスの上昇流によるガス渦流の発生とガス流の乱れにあるとして、これらガス渦流発生を防止するべく鋭意検討した。その結果、反応ガスを均一な流速で回転基板保持体上に供給するために配設される整流板の開口率が、従来、全域で均等に約１０％に調整されていたのに対し、所定領域で開口率を変化させることにより上昇ガス流を効果的に抑制できることから、上記したパーティクルの多量発生、炉壁へのパーティクルの多量付着、薄膜形成成分の析出を防止でき、それによりウエハ基板の結晶欠陥の減少やドーパントのウエハ外周部での取込みを防止でき、結晶欠陥が少なく高品質で均一膜厚の薄膜が気相成長したウエハ基板を得られることを見出し本発明を完成した。
【０００７】
【課題を解決するための手段】
本発明によれば、中空の反応炉の頂部に複数の反応ガス供給口、底部に排気口、内部にウエハ基板を載置する回転基板保持体、及び、内部上部に天井部と空間域を形成して複数のガス孔が穿設された整流板を有して、内部に反応ガスを供給して回転基板保持体上のウエハ基板表面に薄膜を気相成長させる気相成長装置において、炉内の中央部と外周部とのガス流速が異なるように形成されてなることを特徴とする気相成長装置が提供される。
【０００８】
上記本発明の気相成長装置において、前記整流板が炉内周壁に密接し、前記ガス孔の開口率が、その整流板に正投影される前記回転基板保持体の投影形状の外周縁から径方向の外部域で他の領域より大きくなるようにして、炉内中央部と外周部とのガス流速が異なるようにすることが好ましい。または、前記整流板外周縁と炉内周壁とが間隙を有し、該整流板外周縁が、前記整流板に正投影される前記回転基板保持体の投影形状の外周縁から径方向の外部域にあるようにして、炉内中央部と外周部とのガス流速が異なるようにすることが好ましい。これらの場合、前記外部域が、前記反応炉内周壁から所定の間隔幅を有し、前記間隔幅（Ｘ）と前記整流板相当半径（Ｒ_Ｄ）と前記投影形状の相当半径（Ｒ_Ｐ）の差（Ｙ＝Ｒ_Ｄ −Ｒ_Ｐ）との比（Ｘ／Ｙ）が０．０２〜１．０、好ましくは０．０５〜０．５であることが好ましい。また、前記反応炉の水平断面が円形であり、前記整流板と前記回転基板保持体とが同心状に配設されることが好ましい。即ち、上記開口率を大きくする、また、炉内周と間隙を有する整流板外周縁が位置する外部域の炉内壁からの間隔幅が、整流板と回転基板保持体の各半径の差に等しいか、または、その差の０．０２倍以上にあることが好ましい。
【０００９】
また、上記本発明の気相成長装置において、前記空間域が、その内部で前記整流板に正投影される前記回転基板保持体の投影形状の外周縁から径方向の外部域に配置される仕切部材により少なくとも二区分されると共に、各区分に２以上の反応ガス供給口がそれぞれ配設されて、炉内中央部と外周部とのガス流速が異なるようにすることが好ましい。これらの場合、前記外部域が、前記反応炉内周壁から所定の間隔幅を有し、前記間隔幅（Ｘ）と前記整流板相当半径（Ｒ_Ｄ）と前記投影形状の相当半径（Ｒ_Ｐ）の差（Ｙ＝Ｒ_Ｄ −Ｒ_Ｐ）との比（Ｘ／Ｙ）が０．０２〜１．０、好ましくは０．０５〜０．５であることが好ましい。また、前記反応炉の水平断面が円形であり、前記整流板と前記回転基板保持体とが同心状に配設されることが好ましい。即ち、仕切板が配設される外部域の炉内壁からの間隔幅が、整流板と回転基板保持体の各半径の差に等しいか、または、その差の０．０２倍以上にあることが好ましい。また、前記区分毎に、前記反応ガス供給口を介して別個の反応ガス供給系統が連絡されて炉内中央部と外周部とのガス流速が異なるようにすることが好ましい。
【００１０】
更に、上記の本発明の気相成長装置において、反応炉の中空内部が、相当内径が異なる上下部に区分され、上部の相当内径が下部の相当内径より小さく、且つ、上部下端と下部上端とが接続されて中空内部が連続するように形成することができる。
【００１１】
また、本発明によれば、上記の気相成長装置を用いて反応ガスを前記整流板を流通させて整流すると共に、流通整流後の反応ガス流速が、前記他の領域より前記外部域で高速となって前記回転基板保持体上のウエハ基板表面上に供給されることを特徴とする気相成長方法が提供される。この気相成長方法において、前記外部域のガス流速（Ｖ_Ｘ）と前記他の領域のガス流速（Ｖ_Ｚ）との流速比（Ｖ_Ｘ／Ｖ_Ｚ）が５〜３０で、好ましくは１０〜２０の範囲にあることが好ましい。
【００１２】
更に、本発明は、中空の反応炉内に上方より反応ガスを供給し整流後、下方の支持回転されるウエハ基板上に反応ガスを流下させてウエハ基板表面に薄膜を気相成長させる方法であって、前記整流後に、反応炉内壁周辺域のガス流速（Ｖ_Ｘ）がウエハ基板上方域のガス流速（Ｖ_Ｚ）より高速となるように反応ガスを供給することを特徴とする気相成長方法を提供する。この気相成長方法において、反応炉内壁周辺域のガス流速（Ｖ_Ｘ）とウエハ基板上方域のガス流速（Ｖ_Ｚ）との流速比（Ｖ_Ｘ／Ｖ_Ｚ）が５〜３０で、好ましくは１０〜２０の範囲にあることが好ましい。
【００１３】
本発明は上記のように構成され、原料ガス及びキャリアガス等の反応ガスを複数のガス供給口より空間域に供給することによりガスの運動量や圧力分布を均一化すると共に、整流板のガス孔の穿設開口率が整流板面内の所定の外周域で、その他の領域（主に中心域）より大きくなるようにガス孔を穿設配置することから、整流板より下方の反応炉内壁周辺での反応ガス流速を速くすることができる。このことから反応ガス流は、回転基板保持体上のウエハ基板表面近くに達し、径方向への方向性を有して流通し、その後、未反応ガスは炉内壁周辺の高速のガス流により、前記従来法と異なり、炉壁沿いの上昇流を形成することなく回転基板保持体の外周側から反応炉底部の排気口へ円滑に流通する。従って、炉内ガスの温度上昇が抑制され均一核生成が減少し、パーティクル発生が低減され、炉壁へのパーティクル付着や薄膜形成成分析出、付着パーティクルの落下付着等によるウエハ基板の結晶欠陥の形成を防止することができる。また、円滑なガス流れが維持されることからドーパントのウエハ基板外周部での再取込みが防止でき、ウエハ面内抵抗値のも均一となり、高品質の薄膜形成ウエハ基板を得ることができる。これらは従来の反応炉に配設された整流板が、ガス孔を全域に均等な開口率で穿設形成し、整流板下方の反応炉内で均一な流速となるように調整していたのとは全く異なるものであり、本発明により初めて提案されるものである。
【００１４】
【発明の実施の形態】
以下、本発明の実施例を図面に基づきに詳細に説明する。但し、本発明は下記実施例により制限されるものでない。なお、下記実施例においては、便宜上、反応炉の水平断面形状が円形の円筒状中空の反応炉について説明するが、水平断面形状は特に制限されるものでなく角状等でもよい。また、回転基板保持体も同様である。一般的には、円筒状中空反応炉及び円形回転基板保持体が好適に用いられる。
【００１５】
図１は本発明の気相成長装置の一実施例の概略断面説明図（Ａ）及び装置内の（Ａ）に示した所定位置Ｂ、Ｃ及びＤにおけるそれぞれの垂直方向のガス流速分布図（Ｂ）、（Ｃ）及び（Ｄ）である。なお、（Ａ）中の矢印付きの線分は、前記の図７と同様に装置内のガス流を模式的に示したガス流線図である。図２は図１に配備される整流板の平面模式図である。図１（Ａ）及び図２において、反応炉１１は、前記した従来の気相成長装置の反応炉とほぼ同様に構成され、炉内の下部には、ウエハ基板Ｗを載置する回転体１２が、回転軸１３により回転自在に支持され配設され、その下方には回転体１２及びその上に載置されるウエハ基板Ｗとを加熱するヒータ１４が配設される。回転軸１３には回転駆動するモータ（図示せず）が接続される。また、反応炉１１底部には未反応ガス等を排気する複数の排気口１５、１５が配設される。一方、反応炉１１の頂部には、例えばシラン（ＳｉＨ_４）、ジクロロシラン（ＳｉＨ_２Ｃｌ_２）等の原料ガスや、水素（Ｈ_２）、アルゴン（Ａｒ）、ヘリウム（Ｈｅ）等のキャリアガスからなる反応ガスを供給する複数のガス供給口１６、１６が配設される。反応炉内部の上部には天井部と所定の空間域Ｓを保持し、小径のガス孔１７ａ及び大径のガス孔１７ｂがそれぞれ複数穿設された円盤状の整流板１７が、供給される反応ガスが偏流することがないように反応炉１１の内周面に密接して配備される。
【００１６】
本発明において、上記反応炉の上部に配備される整流板は、ガス供給口１６、１６から流入された反応ガスを、多数穿設されたガス孔１７ａ及び１７ｂから反応炉内に流入する。この場合、従来の整流板の均一な開口率と異なり、整流板１７の所定の外部域（Ｘ域）の開口率が、それ以外の領域、主に中心領域（以下、単に中心域またはＺ域とする）より大きくなるようにガス孔を適宜穿設する。この場合、外部域開口率（Ｏ_Ｘ）と中心域開口率（Ｏ_Ｚ）の比は、各領域のガス孔を通過して整流された後の反応ガスの流速が後記するような比率（Ｖ_Ｘ／Ｖ_Ｚ）となるようにするのが好ましい。通常、Ｏ_Ｘ／Ｏ_Ｚ比が１０〜２６００に各域のガス孔をそれぞれ穿設する。また、ガス孔の孔形状や穿設配置は、特に制限されるものでなく反応炉の形状や反応条件に応じて適宜選択することができる。例えば、図１及び２に示したように、大小異なる開口径のガス孔を穿設することにより開口率を変化させる方式がある。図１及び図２において、整流板１７の中心域には小径のガス孔１７ａが均等に配置され、外部域には大径のガス孔１７ｂが適宜配置されている。図２に示した大径のガス孔１７ｂの開口部は周方向に長円状に延びた形状であるが、孔形状は円孔や角孔でもよい。また、図３に示したように、同一形状で同一開口径のガス孔１７ｃを、外部域において単位面積あたりのガス孔の穿設数を中心域より多くすることにより外部域の開口率を大きくすることもできる。更に、本発明の整流板の中心域に穿設するガス孔１７ａは、いずれの場合においても、中心域のガス孔１７ａを通過した反応ガスが整流されて、回転基板保持体１２上のウエハ基板Ｗ表面に均一な流速で流下するように、ほぼ均等に配置される。
【００１７】
本発明において、上記した開口率を大きくする外部域は、図２に示したように、反応炉下方に配設される回転基板保持体１２が正投影して描く投影形状の外周縁Ｐより径方向に位置する領域を指すものである。即ち、円盤状の回転基板保持体１２の正投影により描かれる投影形状の半径Ｒ_Ｐは、回転基板保持体１２の半径（Ｒ_Ｓ）に等しい。本発明の外部域と中心域との境界は、整流板半径Ｒ_Ｄと投影形状の半径Ｒ_Ｐの差Ｙ（＝Ｒ_Ｄ −Ｒ_Ｐ）に等しいか、それより小さくなるようにする。即ち、外部域と中心域との境界は、整流板外周部、即ち、整流板が密接する炉内壁から間隔距離（幅）Ｘを有し、且つ、中心から距離Ｚを有して位置する場合、Ｘ≦Ｙである。従って、Ｘ＝Ｙであれば、Ｚ＝Ｒ_Ｐで投影形状の外周縁Ｐに一致し、Ｘ＜ＹであればＺ＞Ｒ_Ｐで外周縁Ｐより径方向に位置する。更に、外部域の間隔幅Ｘと上記差Ｙとの比が０．０２〜１．０（０．０２≦Ｘ／Ｙ≧１．０）の範囲、好ましくは０．０５〜０．５の範囲となるようするのが好ましい。このＸ／Ｙ比が０．０２未満であると、反応炉壁に沿ってガス流の上方への舞上り現象が生じ、ガス渦流の発生を抑制できない。一方、１．０を超え上記投影形状の外周縁Ｐ内まで大きな開口率とすると回転基板保持体までの反応炉内で、好適な均一な流速分布を有する反応ガス流を得ることができず、結晶欠陥のない高品質の薄膜形成ウエハ基板を製造することができない。
【００１８】
本発明の気相成長装置において、反応炉内上部に配設される整流板は、上記したように外部域（Ｘ域）で中心域（Ｚ域）より開口率が大きくなるようにガス孔が穿設形成され、且つ、中心域のガス孔は通過した反応ガスが均一な流速で流下するように均一に配置される。従って、反応炉頂部の複数のガス供給口１６、１６より空間域Ｓに導入された反応ガスは、整流板１７の各ガス孔を通過して整流されると同時に、Ｘ域とＺ域とは流速を異にして流下する。また、開口率の大きなＸ域と開口率の小さなＺ域との境界は、上記のように回転基板保持体の正投影した投影形状の外周縁Ｐにほぼ一致させるか、その外周縁Ｐから炉内壁方向に位置させる。このため、投影形状の外周縁Ｐより中心側のほぼ回転基板保持体の上方に位置されて均一に配置されたガス孔１７ａを通過する反応ガスは、前記したように回転基板保持体１２上のウエハ基板Ｗ表面に所定の均一な流速（流量）で流下供給される。一方、投影形状外周縁Ｐより外側に位置するＸ域のガス孔１７ｂを通過する反応ガスは、開口率が大であることからＺ域のガス孔１７ａ通過のガス量より多量となり速い流速で流下することになる。
【００１９】
上記のように構成された本発明の気相成長装置を用い、回転基板保持体１２上にウエハ基板Ｗを載置し、その後、排気口１５、１５に接続されている排気制御装置により反応炉１１内を排気し、例えばシランガス等の原料ガスを供給して炉内圧を２０〜５０ｔｏｒｒに調整する。一方、モータを稼働して回転軸１３を回転駆動させて回転基板保持体１２を回転し、その上のウエハ基板Ｗが同時に回転させられる。同時に、ヒータ１４により回転基板保持体１２上のウエハ基板Ｗは、例えば、約９００〜１２００℃に加熱昇温される。また、同時に、ガス供給口１６、１６から流量を所定に制御しながら原料ガス及びキャリアガスからなる反応ガスを反応炉１１内の空間域Ｓに供給する。複数のガス供給口１６、１６から空間域Ｓに供給されるガス流は、運動量や圧力分布が均一化され、更に、整流板１７に所定域に応じた開口率で複数穿設されたガス孔１７ａ及び１７ｂを通過して整流され流下する。また、整流板通過後の反応ガスは、供給されるガス量及び開口率に応じ所定流速となる。更に、前記のように回転基板保持体の投影形状の外周縁Ｐ近辺より中心側のＺ域では、同一径のガス孔１７ａが均等に穿設されることから、反応ガスはほぼ均一なガス流速でウエハ基板上に流下し、ウエハ基板上に均質な薄膜を均一に気相成長させることができる。
【００２０】
本発明の反応炉の整流板を通過する反応ガスは、上記の通り、回転基板保持体の投影形状の外周縁Ｐ近辺を境として開口率に大小の差のある外部域（Ｘ域）と中心域（Ｚ域）とで流速が異なり、反応炉内でガス流速分布に勾配を生じる。例えば、反応ガス流は、図１の（Ａ）のガス流線図、また（Ｂ）、（Ｃ）及び（Ｄ）の流速分布で示したように、開口率の大きな反応炉内壁周辺のＸ域で反応ガス流量が多く高流速でほぼ垂直に流下する。この反応炉内壁周辺に形成される流速の速いガス流により、前記した従来の反応炉で観察された反応炉壁に沿うガス流上昇の舞上り現象が抑制され、ガス渦流の発生も防止される。更に、昇温ガスの上昇がないことから反応炉内気相温度が上ることも防止できる。そのため、反応ガス中の原料ガスによる薄膜形成成分の均一核生成が抑制され、炉内気相中で発生するパーティクルが減少する。従って、気相中で発生したパーティクルが、反応炉壁に付着しメンテナンスサイクルを短縮させたり、ウエハに付着し結晶欠陥を生起させたり、付着パーティクルとしてウエハ品質の直接低下をもたらすこと等の従来法での不都合が防止される。
【００２１】
一方、整流板の中心側のＺ域内を流通する反応ガスは、Ｘ域に比し開口率が小さくほぼ均等に配置されたガス孔１７ａを通過して、その中央部においてＸ域の流速より緩やかでほぼ垂直に均一な流速で流下しウエハ基板上に供給され、従来法と同様に均一な薄膜を形成することができる。図１の（Ａ）に示したように、Ｚ域の最外周部では、Ｘ域に隣接することからＸ域の多量に流出する反応ガスの影響を受け、一旦、ガス流線は中心方向に押されるように屈曲する。しかし、炉内壁周辺のＸ域においてガス舞上り現象やガス渦流の発生がないため、その後はＸ域を流通するガス流に吸引されるように、ウエハ基板上で径方向へ流通し、Ｚ域の中央部をほぼ垂直に流下した反応ガスと共に径方向へ流れガス流遷移層を形成して、排気口１５へ流通することが確認されている。従って、回転基板保持体上のウエハ基板直上では、径方向へのガス流通が妨げられことなく円滑化され、ウエハ基板の中心から外周部へ均等にガスが流通する。このため、ウエハ基板外周部でのドーパントの再取込が生起されることがない。従って、気相成長により均一な薄膜が形成されたウエハ基板の面内抵抗値分布も均一となり、高品質のウエハ基板を得ることができる。
【００２２】
本発明において、整流板の外部域（Ｘ域）と他の領域（Ｚ域）のガス孔を通過して流下する反応ガスのそれぞれの流速Ｖ_Ｘ及びＶ_Ｚは、上記した通り整流板のガス孔の開口径や配置数等を適宜調整して開口率を所定にすることにより、Ｖ_ＸがＶ_Ｚより大きくなるように設定される。好ましくは、Ｘ域の流速Ｖ_ＸとＺ域の流速Ｖ_Ｚとの比（Ｖ_Ｘ／Ｖ_Ｚ）が５〜３０、好ましくは１０〜２０となるように設定する。この流速比が５未満であると、反応炉壁に沿って上方へのガス流の舞上り現象及びガス渦流が発生し好ましくない。一方、３０を超えると炉壁周辺のＸ域（外部域）のガス流速が速過ぎるため、回転基板保持体上の回転基板の中央から外周部への遷移層を形成するガス流れを阻害するため好ましくない。本発明において、Ｚ域ガス流速は、一般に０．０５〜０．７ｍ／ｓとすることが好ましい。０．０５ｍ／ｓ未満であると、Ｘ域に隣接する回転基板保持体上のＺ域の最外部のガス流が中央側に押されるだけでなく、回転基板保持体上の回転基板の中央から外周部へのガス流れが阻害されるため好ましくない。また、０．７ｍ／ｓを超えてもより以上の効果は得られない。従来の気相成長装置では、反応ガスを通常比較的速い０．７〜１．０ｍ／ｓで流していたのに対して、本発明の気相成長装置は０．７ｍ／ｓ以下の流速により従来法で生じていたガス舞上り現象やガス渦流を防止でき、キャリアガスを多量に流す必要がなく工業的に極めて実用性が高い。この場合、Ｘ域のガス流速は、上記Ｖ_Ｘ／Ｖ_Ｚの比率で所定に設定すればよい。
【００２３】
図４は、本発明の気相成長装置の他の実施例の概略断面説明図である。図４においては、反応炉４１内上部の天井部と整流板１７とで形成される空間域が、仕切板１８により周部空間域Ｓ_Ｘと中央空間域Ｓ_Ｚとに二区分される以外は図１の装置と同様に構成される。なお、図１と同一の部材には同一符号を付し説明を省略する。仕切板１８は、一般に、前記図１に示した整流板の開口率の変化する外部域と他の領域との境界、即ち、開口率が大きく反応ガス流速の速い外部域（Ｘ域）と、開口率が小さく反応ガス流速の遅い他の領域（Ｚ域）との境界に配設され、外部域の炉内周壁からの間隔幅は、前記と同様である。通常、回転基板保持体１２の整流板１７への正投影形状の外周縁Ｐ近辺に位置して配設される。空間域Ｓ_Ｘにはガス供給口１６、１６が、また、空間域Ｓ_Ｚにはガス供給口１９がそれぞれ別個に配設され、更に、ガス供給口１６、１６と１９には、別々のガス供給システムＧ_Ｘ及びＧ_Ｚがそれぞれ別個に連絡される。これにより仕切板１８により区分された各空間域Ｓ_Ｘ及びＳ_Ｚには、原料ガス、キャリアガス等の反応ガスを別々に供給することができ、要すれば、反応ガスの種類、また混合ガスであればその混合比率、ガス供給時の温度、圧力、流量等の供給条件を種々変化させて供給することができる。例えば、図４においては、図１と同様に整流板１７は仕切板１８を境にして開口率が異なるように、Ｘ域では大径のガス孔１７ｂを、Ｚ域では小径のガス孔１７ａが穿設されている。また、この方式においては、整流板１７全域の開口率を均等にガス孔を穿設して、仕切板１８により区分された空間域Ｓ_Ｘ及びＳ_Ｚに、ガス供給システムＧ_Ｘ及びＧ_Ｚからそれぞれ異なるガス流量で薄膜形成原料ガス及びキャリアガスからなる反応ガスを供給し、整流板１７を通過後のガス流が反応炉内のＸ域でＺ域より速い流速となるようにしてもよい。また、Ｘ域にはキャリアガスのみを流通させることもできる。
【００２４】
図５は本発明の気相成長装置の他の実施例の概略断面説明図である。図５において、中空の反応炉５１内が、上部１と下部２とに区分され上部１が下部２より細く形成され、上部内径Ｄ_１が下部内径Ｄ_２より小さくＤ_１＜Ｄ_２であり、大径の下部２の上端部Ｕと小径の上部１の下端部Ｂとが連結部２０により接続され、炉内空間が連続される以外は図１の装置と同様に構成される。なお、図１と同一の部材には同一符号を付し説明を省略する。図５の反応炉５１において、回転基板保持体１２は上面が反応炉上部下端Ｂより所定の高低差（Ｈ）を有して下方に位置して配設される。反応炉上部１の側壁面は、通常、下部２の側壁面と平行に垂直に形成され、回転基板保持体１２上面に対し垂直に形成される。上記の上部下端Ｂと下部上端Ｕとの連結部２０は、通常、水平に形成するが、特に制限されるものでなく傾斜状や曲面状に形成してもよい。上記のように構成された反応炉５１では、図１の反応炉１１と同様に回転基板保持体１２の整流板１７への投影形状の外周縁Ｐ近辺を境に炉内の外部域（Ｘ域）でのガス流速を速くすることで、ガス流の舞上り現象やガス渦流の発生が抑制されると共に、炉上部１の内径Ｄ_１が細くなっていることから、ガス流の上方への舞上り現象をより一層抑制でき、相乗的に気相パーティクルの発生が抑制され、炉壁への付着やウエハ基板への影響を防止でき薄膜形成ウエハ基板の品質が向上し、メンテナンスサイクルも長期となり、工業的利点が著しい。
【００２５】
また、図５の反応炉において、反応炉上部内径Ｄ_１、下部内径Ｄ_２、回転基板保持体１２の径Ｄ_Ｓとが、それぞれ下記のような比率関係にあることが好ましい。例えば、Ｄ_１がウエハ直径より大きく、（１）Ｄ_２／Ｄ_１比が１．２以上（Ｄ_２／Ｄ_１ ≧１．２）である。Ｄ_１がウエハ直径より小さいと、炉上部１内壁面から脱落したパーティクルが、回転基板保持体１２上に載置したウエハ基板に付着し易く、結果的にＬＰＤ（ウエハ表面レーザー散乱体（パーティクルを含む））として計測される結晶欠陥が増加するためである。また、通常気相薄膜成長工程で行われるウエハ基板外周部の赤外線による非接触温度測定が困難となるためである。一方、Ｄ_２／Ｄ_１比が１．２より大きいと、反応域のＸ域とＺ域のガス流速比が比較的小さくても、ガス流の上方への舞上り現象を抑制することができる。（２）Ｄ_１／Ｄ_Ｓ比が０．７〜１．２（０．７≦Ｄ_１／Ｄ_Ｓ ≦１．２）にある。Ｄ_１／Ｄ_Ｓ比が０．７〜１．２であれば反応炉のＸ域とＺ域のガス流速比が比較的小さくても、ガス流の上方への舞上り現象を抑制することができる。Ｄ_１／Ｄ_Ｓ比が０．７より小さいと、上部１の壁面が回転基板保持体１２上に載置されたウエハ基板に近接し過ぎて炉内壁面から脱落したパーティクルがウエハ基板に付着し易くなる。そのため、上記Ｄ_１がウエハ基板直径より小さい場合と同様に、ＬＰＤとして測定される結晶欠陥が増加し薄膜形成ウエハ基板の品質が低下するためである。一方、Ｄ_１／Ｄ_Ｓ比が１．２より大きくしても、それ以上の効果の向上は得られない。（３）Ｄ_２／Ｄ_Ｓ比が１．２以上（Ｄ_２／Ｄ_Ｓ ≧１．２）である。Ｄ_２／Ｄ_Ｓ比が１．２より小さいと、回転基板保持体１２上を流通したＺ域のガス流が円滑に排気管に流れにくくなるため、回転基板保持体１２外側に対向する反応炉内壁にパーティクルが付着したり、未反応ガスが回転基板保持体１２の下方で反応して反応炉下部２の内壁に薄膜形成成分が析出しメンテナンスサイクルが短期化するためである。
【００２６】
更に、図５の反応炉５１は、上記のように回転基板保持体１２の上面が反応炉上部１の下端Ｂより下方で所定の高低差Ｈを有して配設される。この高低差Ｈは、通常、回転基板保持体１２上のＺ域でのガス流が形成する遷移層、即ち、図５に矢印にて示したように整流板１７のガス孔１７ａを通過して供給された原料ガス等のガス流が回転基板保持体１２上で中心から外周方向へのベクトルを有するガス層の厚さ（Ｔ）より大きくなるようにすのが好ましい。この高低差Ｈが遷移層厚Ｔより小さいと、回転基板保持体１２上のウエハ基板Ｗの中心から径方向へのガス流が、反応炉上部１の下端Ｂにより阻害され、反応炉上部１の側面に沿って上方への舞上り現象が生じ、ガス渦流の発生を助長する。また、回転基板保持体１２上面は、反応炉上部１と下部２の連結部２０と、平行であることが好ましい。
【００２７】
また、上記の回転基板保持体１２上でのガス流の遷移層厚さＴは、従来から用いられる一般的な反応炉において、主に反応炉内の雰囲気ガスの種類、反応炉内圧力、回転基板保持体の回転数により変化するが、下記式（１）で算出することができる。下記式（１）は、流体力学により一般的に示されるものである。
Ｔ＝３．２２（ν／ω）^１／２（１）
（但し、νは反応炉内反応ガスの動粘性係数（ｍｍ^２／ｓ）を、ωは回転の角速度（ｒａｄ／ｓ）をそれぞれ表示する。）この場合、ωは気相成長装置での薄膜形成稼働中の最小値を採るものとする。例えば、原料ガスがシランガス、キャリアガスが水素ガスであり、回転基板保持体の回転数が５００〜２０００ｒｐｍ（５２〜２０９ｒａｄ／ｓ）である場合は、遷移層厚Ｔは約５〜５０ｍｍとなる。従って、小径の反応炉上部１の下端Ｂから上記のＴ値より大きな高低差Ｈで回転基板保持体上面が位置するように配設することが好ましい。これにより、ウエハ基板上の中心から外周へのガス流れがより一層円滑となり、炉内壁に薄膜形成原料のパーティクルの付着がなく、また得られる薄膜形成ウエハは結晶相に欠陥が無く均一な薄膜が形成される。
【００２８】
図６は本発明の気相成長装置の他の実施例の概略断面説明図である。図６において、小径上部１と大径下部２とに反応炉６１が上下に区分され、上部１と下部２との連結部２０に整流用ガスを流出するための整流ガス流出孔２０ａが複数穿設されると共に、反応炉上部１の外周面全域を包囲して二重環状になし、中空環状部２１により整流ガス流出孔２０ａが穿設された連結部２０を気密に包囲し、中空環状部２１に整流ガス供給口Ｉを設けた以外は、図５の装置と同様に構成される。なお、図５と同一の部材には同一符号を付し説明を省略する。図６の反応炉５１において、上記連結部２０に穿設された整流ガス流出孔２０ａからは、未反応ガスの排気口１５、１５への流れを円滑に行うために整流用ガスを流出することができる。整流用ガスは一般に上記キャリアガスが用いられ、通常、反応炉のガス供給口１６、１６から導入されるキャリアガスと同一ガスを流出する。この整流ガス流出により、Ｘ域の高流速の反応ガスとの相乗効果により、ウエハ基板Ｗに達し薄膜成長に供された後の未反応ガスが、ガス渦流やガス流の荒れを生じることなく回転基板保持体１２外周側を流通し円滑に排気口１５、１５から排出され、反応炉下部での薄膜形成成分の析出もなく、炉のメンテナンスサイクルの長期化を図ることができる。
【００２９】
図６の反応炉６１において、Ｘ域の反応ガスの流速（Ｖ_Ｘ）と整流ガス流出孔２０ａからの整流用ガスの流速（Ｖ_Ｉ）との比（Ｖ_Ｉ／Ｖ_Ｘ）が０．０５〜２（０．０５≦Ｖ_Ｉ／Ｖ_Ｘ ≦２）となるように流出することが好ましい。Ｖ_Ｉ／Ｖ_Ｘ比が上記範囲内となるように、連結部２０の整流ガス流出孔２０ａより整流用ガスを流出することにより、回転基板保持体上の反応ガスの流れ及び回転基板保持体外周側から反応炉下部中空間への未反応ガスの流れが、ガス渦流やガス流れ荒れを生じることなく円滑となり、結晶欠陥が少なく均質な高品質の薄膜形成ウエハ基板を得ることができる。Ｖ_Ｉ／Ｖ_Ｘが０．０５未満であると、回転基板保持体１２外側に位置する反応炉下部の径拡大部分の２０ａからの整流用ガスを流す効果が得られない。また、Ｖ_Ｉ／Ｖ_Ｘが２を超えると、回転基板保持体１２外側の径拡大部分でのガス流速が早くなりすぎ、回転基板保持体１２上での中心から外周への円滑なガス流れが阻害され、均一厚で均質な薄膜成長ができないため好ましくない。
【００３０】
【実施例】
実施例１〜３
前記図１に示した中空の反応炉と同様に構成した断面円形の気相成長装置を用いてウエハ基板上に薄膜を形成した。整流板１７は、開口率の大きい外部域（Ｘ域）の反応炉内壁からの間隔幅Ｘと、整流板１７の半径（Ｒ_Ｄ）と回転基板保持体１２の半径、即ち整流板１７への正投影図形の半径（Ｒ_Ｐ）との差Ｙとが、表１に示した比率（Ｘ／Ｙ）となるようにＸ域とＺ域の境界を設定し、整流板のＺ域には、それぞれ表１に示した直径のガス孔１７ａと開口率（％）で、Ｘ域には表１に示した直径の１７ｂと開口率（％）で、それぞれ穿設して形成し、反応炉に配設した。原料ガスとしてＳｉＨ_４ガスを、キャリアガスとしてＨ_２ガスを、また、ドーパントとしてジボラン（Ｂ_２Ｈ_６）をＨ_２ガス中０．１ｐｐｍ含有させたガスを、Ｘ域の反応ガスの流速（Ｖ_Ｘ）とＺ域の流速（Ｖ_Ｚ）を表１に示した比（Ｖ_Ｘ／Ｖ_Ｚ）となるように流量を調整して供給した。また、反応温度、反応圧力及び回転基板保持体の回転数を表１に併せて示した。
【００３１】
表１に示した気相成長条件下でシリコンウエハ上にＢ_２Ｈ_６ドーパントシリコン薄膜の気相成長を行った。気相成長薄膜を形成した後、使用した気相薄膜成長装置の反応炉内壁のパーティクル付着を目視観察し、その多少を表１に示した。また、得られた薄膜形成ウエハ基板面の結晶相の性状についてテンコール社製サーフスキャン６２００を用い０．１３５μｍ以上のＬＰＤの個数を計測し、その結果をウエハ当たりの個数として表１に示した。また、形成薄膜の膜厚を赤外干渉膜厚計により測定し、その最大厚さ（Ｆ_ｍａｘ）及び最低厚さ（Ｆ_ｍｉｎ）を求め、薄膜厚さの均一性を（Ｆ_ｍａｘ −Ｆ_ｍｉｎ）／（Ｆ_ｍａｘ＋Ｆ_ｍｉｎ）×１００として算出して表１に示した。また、得られた薄膜形成ウエハ基板の抵抗値をＣＶ法を用いて測定し、その最大値（Ｒ_ｍａｘ）及び最低値（Ｒ_ｍｉｎ）を求め、ドーパント取込みによる抵抗値の均一性を（Ｒ_ｍａｘ −Ｒ_ｍｉｎ）／（Ｒ_ｍａｘ＋Ｒ_ｍｉｎ）×１００として算出して表１に示した。
【００３２】
実施例４
前記図４に示した中空の反応炉と同様に構成した断面円形の気相成長装置を用いてウエハ基板上に薄膜を形成した。整流板１７は、全体が表２に示した開口率を有するものを配設した。また、整流板上の空間域には、回転基板保持体のと同一径の円外縁部に仕切板１８を設置し、上部空間域をＳ_Ｘ域とＳ_Ｚ域に二区分した。Ｓ_Ｚ域には実施例１と同様の反応ガスを表２に示した条件で供給した流入し、Ｓ_Ｘ域にはＨ_２ガスを表２に示した流量で供給し、シリコンウエハ上にＢ_２Ｈ_６ドーパントシリコン薄膜の気相成長を行った。反応炉内の観察及び得られた薄膜形成ウエハ基板について実施例１と同様に測定した結果を表２に示した。
【００３３】
実施例５〜６
前記図５（実施例５）及び図６（実施例６）に示した中空の反応炉と同様に構成した断面円形の気相成長装置を用いてウエハ基板上に薄膜を形成した。表２に示した条件で装置を形成した。実施例６では連結部２０からＹ域にＨ_２ガスを表２に示した流量で、Ｘ域の反応ガスの流速（Ｖ_Ｘ）とＹ域の流速（Ｖ_Ｙ）を表２に示した比（Ｖ_Ｘ／Ｖ_Ｙ）となるように調整して供給し、シリコンウエハ上にＢ_２Ｈ_６ドーパントシリコン薄膜の気相成長を行った。反応炉内の観察及び得られた薄膜形成ウエハ基板について実施例１と同様に測定した結果を表２に示した。
【００３４】
【表１】

【００３５】
【表２】

【００３６】
比較例１〜２
Ｖ_Ｘ／Ｖ_Ｚが所定より小さい比較例１について、表２に示した条件で整流板を形成し、また、Ｘ／Ｙ比が所定より大きい比較例２について、表２に示した条件で整流板を形成し、反応炉に配設した以外は、実施例１の反応炉と同様に構成した気相成長装置を用い、実施例１と同様にしてシリコンウエハ上にＢ_２Ｈ_６ドーパントシリコン薄膜の気相成長を行った。その後、反応炉内の観察及び得られた薄膜形成ウエハ基板について同様に測定した結果を表３に示した。
【００３７】
比較例３〜４
前記図７に示した従来の気相薄膜成長装置の反応炉と同様に、即ち、整流板の開口率が均等に形成されて構成された気相成長装置を用い、表２に示した気相成長反応条件下で実施例１と同様にしてシリコンウエハ表面上にＢ_２Ｈ_６ドーパントシリコン薄膜を形成した。その後、反応炉内の観察及び得られた薄膜形成ウエハ基板について同様に測定した結果を表３に示した。
【００３８】
【表３】

【００３９】
上記実施例及び比較例より明らかなように、反応炉内壁周辺の所定幅のＸ域の反応ガス流速を中心のＺ域より所定比率で速くした場合には、得られる薄膜形成ウエハ基板表面の結晶相のＬＰＤ個数が１０００以下で良好な薄膜形成ウエハ基板が得られる。このＬＰＤ個数は、流速比が所定比率より低い比較例１及び従来方式でキャリアガスを本実施例と同様に流通させた比較例３に比し約１／５０以下であり、また、所定幅より広い領域を流速の速い反応ガスを流した比較例２に比しては約１／１３０以下である。また、従来方式でキャリアガスを２００リットル／分で流通させた比較例４でも１０００個以上であることからも、本発明の気相成長による薄膜形成が優れることが分かる。また、形成される薄膜厚の均一性も、比較例４のものよりは低いものの良好であり、抵抗値の均一性は比較例４に比しても優れることが明らかであり、キャリアガスを多量に用いることなく、高品質の薄膜形成ウエハ基板を得ることができる。
【００４０】
【発明の効果】
本発明の気相成長装置は、反応炉へ導入する反応ガス流が中央部と外周部とで流速を異ならせて、外周部でのガス流速が大きくなるようにすることから、種々の不都合を生じさせていた反応ガスの上方への舞上り現象を防止できる。そのため反応ガスの温度上昇が抑止でき、薄膜形成原料ガスの均一核生成が抑制され、気相中で発生するパーティクルが減少する。従って、反応炉壁に付着しメンテナンスサイクルを短縮させたり、ウエハに付着し結晶欠陥の原因となるパーティクルが減少することから、高品質の薄膜形成ウエハ基板を製造することができる。また、本発明の気相薄膜成長装置による気相薄膜成長は、反応炉内のガス流れをパーティクルの発生もなく、乱流や偏流を生じることなく安定に維持し、円滑に反応炉内を流通させることができ薄膜を形成するウエハ基板上でも停滞することなく円滑に流通するため、ドーパントの再取込み等も起こらず、得られるウエハ基板の面内抵抗値も均一となり、高集積化用として好適なウエハ基板を得ることができる。
【図面の簡単な説明】
【図１】本発明の気相薄膜成長装置の反応炉の一実施例の概略断面説明図
【図２】本発明の整流板の一実施例の平面説明図
【図３】本発明の整流板の他の実施例の平面説明図
【図４】本発明の気相薄膜成長装置の他の実施例の概略断面説明図
【図５】本発明の気相薄膜成長装置の他の実施例の概略断面説明図
【図６】本発明の気相薄膜成長装置の他の実施例の概略断面説明図
【図７】従来の気相薄膜成長装置の一例の概略断面説明図
【符号の説明】
１反応炉上部
２反応炉下部
１１、４１、５１、６１、７１反応炉
１２、７２回転基板保持体
１３、７３回転軸
１４、７４ヒータ
１５、７５排気口
１６、１９、７６ガス供給口
１７、７７整流板
１７ａ、１７ｂ、１７ｃ、７７ａ整流孔
１８仕切板
１９、１９’、２９整流ガス導入空間
２０連結部
２０ａ整流ガス孔
Ｂ上部下端
Ｕ下部上端
Ｗウエハ基板
Ｓ、Ｓ_Ｘ、Ｓ_Ｚ空間部
Ｇ_Ｘ、Ｇ_Ｚガス供給システム
Ｉ整流ガス導入口
Ｄ_１反応炉上部内径
Ｄ_２反応炉下部内径
Ｄ_Ｓ回転基板保持体直径[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a vapor phase growth apparatus and a vapor phase growth method, and in particular, reduces generation of particles in a vapor phase and deposits on a furnace wall applied to a manufacturing process of a semiconductor wafer substrate requiring high quality, and is uniform. The present invention relates to a vapor-phase growth apparatus and a vapor-phase growth method capable of forming a semiconductor wafer substrate having a uniform thickness and a small number of crystal defects without forming a thin film having a small thickness.
[0002]
[Prior art]
FIG. 7 is a schematic explanatory view (A) showing an example of a conventional vapor phase growth apparatus, and a vertical gas flow rate distribution diagram (B) at predetermined positions B, C and D shown in FIG. ), (C) and (D). Note that a line segment with an arrow in (A) is a gas flow diagram schematically showing a gas flow in the apparatus. In FIG. 7A, a rotating substrate holder 72 on which a wafer substrate W such as a silicon wafer is placed, a rotating shaft 73 for rotating the rotating substrate holder 72, A heater 74 for heating is provided, and a motor (not shown) for rotationally driving is connected to the rotating shaft 73. Further, a plurality of exhaust ports 75 for exhausting unreacted gas and the like are provided at the bottom of the reaction furnace 71 and connected to an exhaust control device (not shown). On the other hand, at the top of the reaction furnace 71, a plurality of

gas supply pipes

76, 76 for supplying a reaction gas such as a raw material gas and a carrier gas into the furnace and a disk-shaped current plate 77 are provided. A number of holes 77a for regulating the flow of gas are formed. The conventional vapor phase epitaxy apparatus is configured as described above, and the substrate W placed on the rotating substrate holder 72 that rotates at a predetermined rotation speed by the rotation of the motor is heated to a predetermined temperature by the heater 74 while rotating. Is done. At the same time, a reaction gas such as a raw material gas or a carrier gas is introduced into the reaction furnace 71 through a plurality of gas supply pipes 76 to make the gas momentum and pressure distribution uniform, and then the gas flow velocity distribution in the reaction furnace becomes uniform. Thus, the reaction gas is uniformly supplied to the wafer substrate W on the rotating substrate holder 72 by passing through a large number of holes 77a of the current plate 77 so that the thin film is vapor-phase grown.
[0003]
In the vapor phase growth apparatus for forming a thin film on a semiconductor wafer as described above, in order to prevent the generation of particles due to the gas for forming the thin film and the attachment of the precipitate to the inner wall of the reaction furnace, and the inconvenience in forming the thin film, the crystal is formed. Various proposals have been made to obtain a thin film-formed wafer having a uniform thin film and a uniform film thickness without causing defects. For example, in Japanese Patent Application Laid-Open No. Hei 5-74719, a crystal flow is prevented by controlling the supply flow rate of a raw material gas to a predetermined value to prevent a temperature change in a reactor. In Japanese Patent Application Laid-Open No. 5-90167, the amount of source gas, the pressure in the furnace, the number of rotations of the rotary substrate holder, and the like are controlled to a predetermined value so as to make the in-plane temperature distribution of the wafer substrate uniform when forming a thin film, thereby preventing slip. I'm trying. In Japanese Patent Application Laid-Open No. 6-216045, a shield tube is provided on a part of the inner wall of the reactor where precipitates are liable to be formed, while keeping the inner peripheral surface smooth, and the reactor is easily cleaned after performing a thin film forming operation. At the same time, the gas flow is maintained in a laminar state to form a uniform thin film. Further, in Japanese Patent Application Laid-Open No. 7-50260, a source gas and a carrier gas are introduced through a plurality of supply pipes onto a flow straightening plate having a plurality of holes in an upper portion of a reaction furnace, and the inflow direction is made predetermined. In addition, the gas momentum and the gas pressure are made uniform to supply a source gas or the like at a uniform flow rate onto the substrate, thereby achieving a uniform thin film thickness.
[0004]
[Problems to be solved by the invention]
However, even in the conventional vapor phase growth apparatuses proposed in the above-mentioned various proposals, crystal defects do not occur on the wafer substrate on which the thin film is grown, or inconveniences such as adhesion of particles are not sufficiently prevented. In addition, with the recent high integration of semiconductors in recent years, the quality of wafer substrates has been required to be further improved. Is increasing. SUMMARY OF THE INVENTION The present invention has been made in view of such a problem that the quality of a wafer substrate is degraded in the formation of a vapor-growth thin film by such a conventional vapor-phase growth apparatus. The inventors first studied in detail a phenomenon occurring in a conventional vapor phase growth apparatus. As a result, a phenomenon was observed in which a large amount of particles adhered to the reaction furnace wall, and therefore, the maintenance cycle was shortened, and the particles adhered to the reaction furnace wall adhered to the wafer substrate and caused crystal defects. It has been found that the particles directly cause the deterioration of the wafer quality.
[0005]
The inventors further studied the flow of the raw material gas in the reactor in order to find out the cause of the large amount of particles attached to the reactor wall from the above findings. As a result, it has been further clarified that the following phenomenon occurs in the reactor. That is, {circle around (1)} In the conventional reaction furnace 71 shown in FIG. 7, a reaction gas such as a silicon source gas is introduced from the top and supplied at a uniform flow rate onto the wafer substrate W to be used for thin film formation. Since the lower part of the reaction furnace is heated by the heater 74, the reaction gas that has reached the vicinity of the wafer substrate W is also heated and heated. As a result, as shown in the gas flow diagram of FIG. 7 (A) and the flow velocity distributions of (B), (C) and (D), the gas in the furnace (B) region has a substantially uniform flow velocity. In the area (C), the gas flow rate decreases near the inner wall of the furnace, and in the area (D), the gas flow turns into an upward flow along the inner wall of the reactor. For this reason, a rising phenomenon of the reaction gas occurs, and a gas vortex occurs. {Circle around (2)} Since the heated reaction gas rises, the temperature of the whole area inside the reaction furnace 71 also rises, so that uniform nucleation of the thin film forming raw material gas in the gas phase increases, and particles in the gas phase increase. Occurrence increases. {Circle around (3)} When the gas vortex flows, the dopant in the reaction gas may be re-introduced at the outer peripheral portion of the wafer substrate W on the rotary substrate holder 72, and the in-plane resistance value distribution of the obtained wafer substrate may be obtained. Causes non-uniformity.
[0006]
The generation of the gas vortex that causes the various inconveniences described above can be suppressed to some extent by making the gas flow velocity in the axial direction of the rotating substrate holder extremely high at about 1 m / s or more in the conventional reactor. However, for this purpose, a large amount of carrier gas needs to be flowed, which is industrially poor in practical use. For this reason, the inventors of the present invention have the above-mentioned inconveniences such as the deterioration of the quality of the thin-layer-formed wafer substrate and the shortening of the maintenance cycle of the reactor, mainly due to the generation of the gas vortex due to the upward flow of the gas in the reactor. Assuming that the gas flow is turbulent, diligent studies were conducted to prevent the generation of these gas eddies. As a result, while the aperture ratio of the current plate arranged to supply the reaction gas onto the rotating substrate holder at a uniform flow rate is conventionally adjusted to about 10% uniformly over the entire area, a predetermined Since the rising gas flow can be effectively suppressed by changing the aperture ratio in the region, it is possible to prevent the generation of a large amount of the above-described particles, the adhesion of a large amount of the particles to the furnace wall, and the deposition of the thin film forming component, thereby preventing the wafer substrate from being formed. It has been found that a reduction in crystal defects and the incorporation of dopants at the outer periphery of the wafer can be prevented, and a wafer substrate on which a thin film having high crystal quality and a uniform thickness can be obtained with few crystal defects can be obtained.
[0007]
[Means for Solving the Problems]
According to the present invention, a plurality of reaction gas supply ports are provided at the top of a hollow reaction furnace, an exhaust port is provided at the bottom, a rotating substrate holder on which a wafer substrate is placed, and a ceiling and a space are formed at the top inside. In a vapor phase growth apparatus having a rectifying plate having a plurality of gas holes formed therein and supplying a reaction gas thereinto to vapor-phase grow a thin film on a wafer substrate surface on a rotating substrate holder, a furnace Wherein the gas flow rates of the central portion and the outer peripheral portion are different from each other.
[0008]
In the vapor phase growth apparatus of the present invention, the rectifying plate is in close contact with an inner peripheral wall of the furnace, and an opening ratio of the gas holes has a diameter from an outer peripheral edge of a projected shape of the rotating substrate holder that is orthogonally projected on the rectifying plate. It is preferable to make the gas flow rate different between the central part and the outer peripheral part in the furnace by making the outer part in the direction larger than other areas. Alternatively, there is a gap between the outer peripheral edge of the straightening plate and the inner peripheral wall of the furnace, and the outer peripheral edge of the straightening plate is radially outward from the outer peripheral edge of the projected shape of the rotating substrate holder that is orthogonally projected on the straightening plate. It is preferable that the gas flow rates in the central portion and the outer peripheral portion in the furnace are different from each other. In these cases, the outer region has a predetermined interval width from the inner peripheral wall of the reactor, and the interval width (X) and the rectifier plate equivalent radius (R _D ) And the equivalent radius of the projected shape (R _P ) Difference (Y = R _D -R _P ) Is preferably 0.02 to 1.0, and more preferably 0.05 to 0.5. Further, it is preferable that a horizontal cross section of the reaction furnace is circular, and the current plate and the rotating substrate holder are disposed concentrically. That is, the opening ratio is increased, and the width of the gap from the furnace inner wall in the outer region where the outer periphery of the straightening plate having the gap with the inner periphery of the furnace is located is equal to the difference between the respective radii of the straightening plate and the rotating substrate holder. Or it is preferably at least 0.02 times the difference.
[0009]
Further, in the vapor phase growth apparatus of the present invention, the partition is disposed in an outer region in a radial direction from an outer peripheral edge of a projected shape of the rotating substrate holder, which is orthogonally projected on the rectifying plate therein. It is preferable that at least two sections are provided by the member, and that two or more reaction gas supply ports are provided in each section so that the gas flow rates in the central portion and the outer peripheral portion in the furnace are different. In these cases, the outer region has a predetermined interval width from the inner peripheral wall of the reactor, and the interval width (X) and the rectifier plate equivalent radius (R _D ) And the equivalent radius of the projected shape (R _P ) Difference (Y = R _D -R _P ) Is preferably 0.02 to 1.0, and more preferably 0.05 to 0.5. Further, it is preferable that a horizontal cross section of the reaction furnace is circular, and the current plate and the rotating substrate holder are disposed concentrically. That is, the width of the space between the outer wall where the partition plate is disposed and the inner wall of the furnace is equal to the difference between the respective radii of the current plate and the rotating substrate holder, or is at least 0.02 times the difference. preferable. In addition, it is preferable that a separate reaction gas supply system is connected to each of the sections via the reaction gas supply port so that the gas flow rates in the central portion and the outer peripheral portion in the furnace are different.
[0010]
Furthermore, in the above-described vapor phase growth apparatus of the present invention, the hollow interior of the reactor is divided into upper and lower portions having different equivalent inner diameters, the equivalent inner diameter of the upper part is smaller than the equivalent inner diameter of the lower part, and the upper and lower ends and the lower and upper ends are different. Are connected to form a continuous hollow interior.
[0011]
Further, according to the present invention, the reaction gas is circulated and rectified by flowing through the rectifying plate by using the above-described vapor phase growth apparatus, and the flow rate of the reaction gas after the flow rectification is higher in the outer region than in the other region. Wherein the wafer is supplied onto the surface of the wafer substrate on the rotating substrate holder. In this vapor phase growth method, the gas flow rate (V _X ) And the gas flow rates (V _Z ) And the flow rate ratio (V _X / V _Z ) Is 5 to 30, preferably 10 to 20.
[0012]
Further, the present invention provides a method in which a reaction gas is supplied from above into a hollow reaction furnace, rectified, and then the reaction gas is caused to flow down onto a lower supported and rotated wafer substrate to vapor-phase grow a thin film on the wafer substrate surface. After the rectification, the gas flow velocity (V _X ) Is the gas flow velocity (V _Z A) providing a vapor phase growth method characterized by supplying a reaction gas at a higher speed. In this vapor phase growth method, the gas flow rate (V _X ) And the gas flow velocity (V _Z ) And the flow rate ratio (V _X / V _Z ) Is 5 to 30, preferably 10 to 20.
[0013]
The present invention is configured as described above, and supplies a reaction gas such as a raw material gas and a carrier gas to a space region from a plurality of gas supply ports to make the momentum and pressure distribution of the gas uniform, and to improve the gas holes of the current plate. The gas holes are drilled and arranged so that the opening ratio of the hole is larger than the other region (mainly the center region) in the predetermined outer peripheral area in the plane of the current plate. The reaction gas flow rate can be increased. From this, the reaction gas flow reaches near the surface of the wafer substrate on the rotating substrate holder, and flows with directivity in the radial direction.After that, unreacted gas flows due to the high-speed gas flow around the inner wall of the furnace. Unlike the above-described conventional method, the gas flows smoothly from the outer peripheral side of the rotating substrate holder to the exhaust port at the bottom of the reactor without forming an upward flow along the furnace wall. Therefore, the temperature rise of the gas in the furnace is suppressed, uniform nucleation is reduced, and particle generation is reduced, and crystal defects on the wafer substrate due to particle adhesion to the furnace wall, deposition of thin-film forming components, and adhesion of adhered particles falling, etc. Formation can be prevented. Further, since the smooth gas flow is maintained, re-uptake of the dopant at the outer peripheral portion of the wafer substrate can be prevented, the in-plane resistance value of the wafer becomes uniform, and a high-quality thin film-formed wafer substrate can be obtained. In these, the straightening plate arranged in the conventional reactor was formed such that gas holes were formed in the entire region at a uniform opening ratio, so that a uniform flow rate was obtained in the reactor below the straightening plate. Are completely different from those described above and are proposed for the first time by the present invention.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited by the following examples. In the following examples, for the sake of convenience, a cylindrical hollow reactor having a circular horizontal cross-sectional shape is described, but the horizontal cross-sectional shape is not particularly limited and may be a square shape or the like. The same applies to the rotating substrate holder. Generally, a cylindrical hollow reactor and a circular rotating substrate holder are preferably used.
[0015]
FIG. 1 is a schematic cross-sectional explanatory view of an embodiment of a vapor phase growth apparatus according to the present invention (A), and a gas flow distribution diagram in a vertical direction at predetermined positions B, C and D shown in FIG. B), (C) and (D). Note that the line segment with an arrow in (A) is a gas flow diagram schematically showing the gas flow in the apparatus as in FIG. 7 described above. FIG. 2 is a schematic plan view of the current plate provided in FIG. 1A and 2, a reactor 11 has substantially the same configuration as that of the above-described conventional vapor phase growth apparatus, and a rotating body 12 on which a wafer substrate W is mounted is provided at a lower portion in the furnace. Is rotatably supported by a rotating shaft 13, and a heater 14 for heating the rotating body 12 and the wafer substrate W mounted thereon is provided below the rotating body 12. The rotating shaft 13 is connected to a motor (not shown) that is driven to rotate. A plurality of exhaust ports 15 for exhausting unreacted gas and the like are provided at the bottom of the reactor 11. On the other hand, for example, silane (SiH ₄ ), Dichlorosilane (SiH ₂ Cl ₂ ) And hydrogen (H ₂ ), A plurality of gas supply ports 16 for supplying a reaction gas composed of a carrier gas such as argon (Ar) and helium (He). At the upper part inside the reaction furnace, a disk-shaped rectifying plate 17 holding a ceiling and a predetermined space area S and having a plurality of small-diameter gas holes 17a and a plurality of large-diameter gas holes 17b is provided. It is provided close to the inner peripheral surface of the reactor 11 so that the gas does not drift.
[0016]
In the present invention, the flow straightening plate provided at the upper part of the reaction furnace allows the reaction gas flowing from the

gas supply ports

16 and 16 to flow into the reaction furnace through the

gas holes

17a and 17b formed therein. In this case, unlike the uniform aperture ratio of the conventional current plate, the aperture ratio of the predetermined outer region (X region) of the current plate 17 is changed to the other region, mainly the central region (hereinafter simply referred to as the central region or the Z region). Gas holes are appropriately formed so as to be larger. In this case, the external area aperture ratio (O _X ) And center area aperture ratio (O _Z The ratio (V) is such that the flow rate of the reaction gas after being rectified through the gas holes in each region is described later. _X / V _Z ) Is preferable. Usually O _X / O _Z Gas holes in each area are formed at a ratio of 10 to 2600, respectively. The shape and arrangement of the gas holes are not particularly limited, and can be appropriately selected according to the shape of the reaction furnace and the reaction conditions. For example, as shown in FIGS. 1 and 2, there is a method of changing the aperture ratio by forming gas holes having different opening diameters. In FIGS. 1 and 2, small-diameter gas holes 17 a are uniformly arranged in the central region of the current plate 17, and large-diameter gas holes 17 b are appropriately arranged in the outer region. The opening of the large-diameter gas hole 17b shown in FIG. 2 has a shape extending in the shape of an ellipse in the circumferential direction, but the hole shape may be a circular hole or a square hole. Further, as shown in FIG. 3, by increasing the number of gas holes 17c having the same shape and the same opening diameter per unit area in the outer region than in the center region, the opening ratio of the outer region is increased. You can also. Further, in any case, the gas holes 17a drilled in the central region of the current plate are rectified by the reaction gas that has passed through the gas holes 17a in the central region, and the wafer substrate on the rotating substrate holder 12 is rectified. They are arranged almost uniformly so as to flow down at a uniform flow rate on the W surface.
[0017]
In the present invention, as shown in FIG. 2, the outer area for increasing the aperture ratio has a diameter larger than the outer peripheral edge P of the projected shape drawn by the rotary substrate holder 12 disposed below the reaction furnace. It indicates a region located in the direction. That is, the radius R of the projected shape drawn by orthographic projection of the disk-shaped rotating substrate holder 12 _P Is the radius of the rotating substrate holder 12 (R _S )be equivalent to. The boundary between the outer region and the center region of the present invention is defined by a rectifying plate radius R _D And the radius R of the projected shape _P Difference Y (= R _D -R _P ) Or less. That is, when the boundary between the outer region and the center region is located at an interval distance (width) X from the outer periphery of the current plate, that is, the inner wall of the furnace where the current plate is in close contact, and at a distance Z from the center. , X ≦ Y. Therefore, if X = Y, Z = R _P To the outer peripheral edge P of the projected shape, and if X <Y, Z> R _P And is located radially from the outer peripheral edge P. Further, the ratio of the interval width X of the outer region to the difference Y is in the range of 0.02 to 1.0 (0.02 ≦ X / Y ≧ 1.0), preferably in the range of 0.05 to 0.5. It is preferable that If the X / Y ratio is less than 0.02, the gas flow will rise upward along the reactor wall, and the generation of gas vortex cannot be suppressed. On the other hand, if the opening ratio is set to be larger than 1.0 and the inside of the outer peripheral edge P of the projection shape, a reaction gas flow having a suitable uniform flow velocity distribution cannot be obtained in the reaction furnace up to the rotating substrate holder, A high-quality thin film-formed wafer substrate without crystal defects cannot be manufactured.
[0018]
In the vapor phase growth apparatus according to the present invention, the gas flow plate disposed in the upper part of the reactor has gas holes such that the aperture ratio is larger in the outer region (X region) than in the central region (Z region) as described above. The gas holes in the center area are formed so as to be uniformly arranged so that the passed reaction gas flows down at a uniform flow rate. Therefore, the reaction gas introduced into the space S through the plurality of gas supply ports 16 at the top of the reaction furnace passes through the gas holes of the flow straightening plate 17 and is rectified. Flow down at different flow rates. Also, the boundary between the X region having a large aperture ratio and the Z region having a small aperture ratio substantially coincides with the outer peripheral edge P of the orthographically projected shape of the rotating substrate holder as described above, or the furnace is moved from the outer peripheral edge P to Position it toward the inner wall. For this reason, the reaction gas passing through the gas holes 17a, which are located substantially above the rotating substrate holder on the center side with respect to the outer peripheral edge P of the projected shape and pass through the uniformly arranged gas holes 17a, The wafer is supplied to the surface of the wafer substrate W at a predetermined uniform flow rate (flow rate). On the other hand, the reactant gas passing through the gas holes 17b in the X region located outside the outer peripheral edge P of the projection shape has a large aperture ratio and is larger than the gas amount passing through the gas holes 17a in the Z region and flows down at a high flow velocity. Will do.
[0019]
Using the vapor phase growth apparatus of the present invention configured as described above, the wafer substrate W is placed on the rotating substrate holder 12, and thereafter, the reaction furnace is controlled by the exhaust control device connected to the

exhaust ports

15, 15. The inside of the furnace 11 is evacuated, and a source gas such as silane gas is supplied to adjust the furnace pressure to 20 to 50 torr. On the other hand, the motor is operated to rotate the rotating shaft 13 to rotate the rotating substrate holder 12, and the wafer substrate W thereon is simultaneously rotated. At the same time, the temperature of the wafer substrate W on the rotary substrate holder 12 is heated to about 900 to 1200 ° C. by the heater 14. At the same time, a reaction gas composed of a raw material gas and a carrier gas is supplied to the space S in the reaction furnace 11 while controlling the flow rate to a predetermined value from the

gas supply ports

16, 16. The gas flow supplied from the plurality of gas supply ports 16 to the space area S has a uniform momentum and pressure distribution, and a plurality of gas holes formed in the current plate 17 with an opening ratio corresponding to a predetermined area. After passing through 17a and 17b, it is rectified and flows down. The flow rate of the reaction gas after passing through the straightening plate has a predetermined flow rate according to the supplied gas amount and the aperture ratio. Further, as described above, the gas holes 17a having the same diameter are uniformly formed in the Z region closer to the center from the vicinity of the outer peripheral edge P of the projected shape of the rotating substrate holder, so that the reaction gas has a substantially uniform gas flow rate. Thus, a uniform thin film can be uniformly vapor-phase-grown on the wafer substrate.
[0020]
As described above, the reaction gas passing through the straightening plate of the reaction furnace of the present invention is, as described above, centered on the outer region (X region) having a difference in aperture ratio from the vicinity of the outer peripheral edge P of the projected shape of the rotating substrate holder. The flow rate differs in the zone (Z zone), and a gradient occurs in the gas flow rate distribution in the reactor. For example, as shown in the gas flow diagram of FIG. 1A and the flow velocity distributions of FIGS. 1B, 1C, and 1D, the reaction gas flow is X around the inner wall of the reactor having a large aperture ratio. The flow rate of the reaction gas is large in the region, and flows down almost vertically at a high flow rate. Due to the high-velocity gas flow formed around the inner wall of the reactor, the rising phenomenon of the gas flow rising along the reactor wall observed in the above-mentioned conventional reactor is suppressed, and the generation of gas vortex is also prevented. . Furthermore, since there is no rise in the temperature-raising gas, it is possible to prevent the gas phase temperature in the reactor from rising. Therefore, uniform nucleation of thin film forming components due to the source gas in the reaction gas is suppressed, and particles generated in the gas phase in the furnace are reduced. Therefore, conventional methods such as particles generated in the gas phase adhere to the reactor wall to shorten the maintenance cycle, adhere to the wafer to cause crystal defects, and directly reduce the wafer quality as adhered particles. Inconvenience is prevented.
[0021]
On the other hand, the reactant gas flowing in the Z region on the center side of the current plate passes through the gas holes 17a having a smaller opening ratio than the X region and arranged almost evenly, and has a gentler flow rate in the center than the flow velocity in the X region. Then, it flows down almost vertically at a uniform flow rate and is supplied onto the wafer substrate, so that a uniform thin film can be formed as in the conventional method. As shown in FIG. 1 (A), the outermost peripheral portion of the Z region is affected by a large amount of reactant gas flowing out of the X region because it is adjacent to the X region, so that the gas streamlines once move toward the center. Bend to be pushed. However, since there is no gas rising phenomenon or gas vortex in the X region around the inner wall of the furnace, thereafter, the gas flows in the radial direction on the wafer substrate so as to be sucked by the gas flow flowing in the X region, and the Z region. It has been confirmed that the gas flows radially with the reaction gas flowing down the center portion of the gas flow in the radial direction to form a gas flow transition layer and flows to the exhaust port 15. Therefore, immediately above the wafer substrate on the rotating substrate holder, the gas flow in the radial direction is smooth without being hindered, and the gas flows uniformly from the center of the wafer substrate to the outer peripheral portion. For this reason, re-uptake of the dopant in the outer peripheral portion of the wafer substrate does not occur. Therefore, the in-plane resistance value distribution of the wafer substrate on which a uniform thin film is formed by vapor phase growth becomes uniform, and a high-quality wafer substrate can be obtained.
[0022]
In the present invention, the respective flow velocities V of the reactant gas flowing down through the gas holes in the outer region (X region) and the other region (Z region) of the current plate. _X And V _Z As described above, by appropriately adjusting the opening diameter and the number of arrangement of the gas holes of the current plate, and setting the opening ratio to a predetermined value, V _X Is V _Z Set to be larger. Preferably, the flow velocity V in the X region _X And the flow velocity V in the Z region _Z And the ratio (V _X / V _Z ) Is set to be 5 to 30, preferably 10 to 20. If the flow velocity ratio is less than 5, a gas flow rising phenomenon and a gas vortex flow along the reactor wall are undesirably generated. On the other hand, if it exceeds 30, the gas flow velocity in the X region (external region) around the furnace wall is too high, and this impedes the gas flow that forms a transition layer from the center to the outer periphery of the rotating substrate on the rotating substrate holder. Not preferred. In the present invention, the gas flow velocity in the Z region is generally preferably 0.05 to 0.7 m / s. When the velocity is less than 0.05 m / s, the outermost gas flow in the Z region on the rotating substrate holder adjacent to the X region is not only pushed to the center side, but also from the center of the rotating substrate on the rotating substrate holder. This is not preferable because gas flow to the outer peripheral portion is hindered. Further, even if it exceeds 0.7 m / s, no further effect can be obtained. In the conventional vapor phase epitaxy apparatus, the reaction gas is usually flowed at a relatively high speed of 0.7 to 1.0 m / s, whereas the vapor phase epitaxy apparatus of the present invention has a flow rate of 0.7 m / s or less. It is possible to prevent the gas rising phenomenon and the gas vortex that occur in the conventional method, and it is not necessary to flow a large amount of the carrier gas, so that the present invention is extremely practical in industrial use. In this case, the gas flow rate in the X region is V _X / V _Z May be set at a predetermined ratio.
[0023]
FIG. 4 is a schematic sectional explanatory view of another embodiment of the vapor phase growth apparatus of the present invention. In FIG. 4, a space formed by a ceiling part in the upper part of the reactor 41 and the rectifying plate 17 is divided into a peripheral space S by a partition plate 18. _X And central space S _Z The configuration is the same as that of FIG. The same members as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The partition plate 18 generally has a boundary between the external region where the aperture ratio of the current plate shown in FIG. 1 changes and another region, that is, an external region (X region) having a large aperture ratio and a high reaction gas flow rate; It is disposed at the boundary with another region (Z region) having a small opening ratio and a low reaction gas flow rate, and the width of the space between the outer region and the inner peripheral wall of the furnace is the same as described above. Usually, it is disposed near the outer peripheral edge P of the orthographic shape of the rotating substrate holder 12 on the rectifying plate 17. Space S _X Have

gas supply ports

16 and 16 and a space area S _Z Are provided with separate gas supply ports 19, and the

gas supply ports

16, 16 and 19 are provided with separate gas supply systems G _X And G _Z Are contacted separately. Thereby, each space area S divided by the partition plate 18 _X And S _Z The reaction gas such as a raw material gas and a carrier gas can be supplied separately to each other, and if necessary, the type of the reaction gas, and if it is a mixed gas, its mixing ratio, temperature, pressure, flow rate, etc. at the time of gas supply Can be supplied with various supply conditions. For example, in FIG. 4, as in FIG. 1, the rectifying plate 17 has a large-diameter gas hole 17 b in the X region and a small-diameter gas hole 17 a in the Z region so that the aperture ratio differs at the partition plate 18. Has been drilled. Further, in this method, gas holes are formed so that the aperture ratio of the entire rectifying plate 17 is uniform, and the space area S divided by the partition plate 18 is formed. _X And S _Z And gas supply system G _X And G _Z , A reactant gas composed of a thin film forming raw material gas and a carrier gas may be supplied at different gas flow rates so that the gas flow after passing through the rectifying plate 17 has a flow velocity higher in the X region in the reaction furnace than in the Z region. . Further, only the carrier gas can be circulated in the X region.
[0024]
FIG. 5 is a schematic sectional explanatory view of another embodiment of the vapor phase growth apparatus of the present invention. In FIG. 5, the inside of a hollow reactor 51 is divided into an upper part 1 and a lower part 2, and the upper part 1 is formed thinner than the lower part 2. ₁ Is the lower inner diameter D ₂ Smaller D ₁ <D ₂ 1, except that the upper end portion U of the large-diameter lower portion 2 and the lower end portion B of the small-diameter upper portion 1 are connected by the connecting portion 20 and the furnace space is continuous. The same members as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the reaction furnace 51 shown in FIG. 5, the rotating substrate holder 12 is disposed such that the upper surface is located below the lower end B of the reaction furnace at a predetermined height difference (H). The side wall surface of the upper part 1 of the reaction furnace is usually formed perpendicular to the side wall surface of the lower part 2 and perpendicular to the upper surface of the rotating substrate holder 12. The connecting portion 20 between the upper lower end B and the lower upper end U is generally formed horizontally, but is not particularly limited and may be formed in an inclined shape or a curved shape. In the reaction furnace 51 configured as described above, similarly to the reaction furnace 11 of FIG. 1, an outer region (X region) of the inside of the furnace is bordered by the vicinity of the outer peripheral edge P of the shape of the rotating substrate holder 12 projected onto the rectifying plate 17. By increasing the gas flow velocity in (1), the rise of the gas flow and the generation of the gas vortex are suppressed, and the inner diameter D of the furnace upper part 1 is reduced. ₁ The thinner film can further suppress the rising phenomenon of the gas flow, synergistically suppress the generation of gas phase particles, and prevent adhesion to the furnace wall and influence on the wafer substrate. The quality of the formed wafer substrate is improved, the maintenance cycle is long, and the industrial advantages are remarkable.
[0025]
Further, in the reactor shown in FIG. ₁ , Lower inner diameter D ₂ , The diameter D of the rotating substrate holder 12 _S Are preferably in the following ratio relationships. For example, D ₁ Is larger than the wafer diameter, and (1) D ₂ / D ₁ When the ratio is 1.2 or more (D ₂ / D ₁ ≧ 1.2). D ₁ Is smaller than the wafer diameter, particles that have fallen from the inner wall surface of the furnace upper part 1 tend to adhere to the wafer substrate placed on the rotating substrate holder 12, and as a result, LPD (wafer surface laser scatterer (including particles) This is because crystal defects measured as ()) increase. Further, it is difficult to measure the non-contact temperature of the outer peripheral portion of the wafer substrate using infrared rays, which is usually performed in the vapor phase thin film growth step. On the other hand, D ₂ / D ₁ When the ratio is larger than 1.2, the upward rise of the gas flow can be suppressed even if the gas flow rate ratio between the X zone and the Z zone in the reaction zone is relatively small. (2) D ₁ / D _S When the ratio is 0.7 to 1.2 (0.7 ≦ D ₁ / D _S ≤ 1.2). D ₁ / D _S If the ratio is 0.7 to 1.2, even if the gas flow rate ratio between the X region and the Z region of the reactor is relatively small, the upward flow phenomenon of the gas flow can be suppressed. D ₁ / D _S If the ratio is less than 0.7, particles that fall off the furnace inner wall surface because the wall surface of the upper part 1 is too close to the wafer substrate placed on the rotating substrate holder 12 are likely to adhere to the wafer substrate. Therefore, the above D ₁ Is smaller than the wafer substrate diameter, the crystal defects measured as LPD increase, and the quality of the thin film-formed wafer substrate deteriorates. On the other hand, D ₁ / D _S Even if the ratio is larger than 1.2, no further improvement in the effect can be obtained. (3) D ₂ / D _S When the ratio is 1.2 or more (D ₂ / D _S ≧ 1.2). D ₂ / D _S When the ratio is smaller than 1.2, the gas flow in the Z region flowing on the rotating substrate holder 12 is difficult to flow smoothly to the exhaust pipe, so that particles adhere to the inner wall of the reaction furnace facing the outside of the rotating substrate holder 12. This is because unreacted gas reacts below the rotating substrate holder 12 to deposit a thin film forming component on the inner wall of the lower portion 2 of the reactor, thereby shortening the maintenance cycle.
[0026]
Further, the reaction furnace 51 shown in FIG. 5 is provided with the predetermined height difference H below the lower end B of the reaction furnace upper part 1 with the upper surface of the rotating substrate holder 12 as described above. This height difference H usually passes through a transition layer formed by a gas flow in the Z region on the rotating substrate holder 12, that is, through a gas hole 17a of the rectifying plate 17 as shown by an arrow in FIG. It is preferable that the supplied gas flow such as the source gas is larger than the thickness (T) of the gas layer having a vector from the center to the outer periphery on the rotating substrate holder 12. If the height difference H is smaller than the transition layer thickness T, the gas flow in the radial direction from the center of the wafer substrate W on the rotating substrate holder 12 is obstructed by the lower end B of the reactor upper part 1, A soaring phenomenon occurs along the side surface, which promotes the generation of gas vortex. Further, it is preferable that the upper surface of the rotary substrate holder 12 is parallel to the connecting portion 20 between the upper part 1 and the lower part 2 of the reactor.
[0027]
The transition layer thickness T of the gas flow on the rotating substrate holder 12 is mainly determined by the type of atmospheric gas in the reaction furnace, the pressure in the reaction furnace, Although it changes depending on the number of rotations of the substrate holder, it can be calculated by the following equation (1). Equation (1) below is generally expressed by hydrodynamics.
T = 3.22 (ν / ω) ^1/2 (1)
(Where ν is the kinematic viscosity coefficient (mm ² / S) and ω indicates the angular velocity of rotation (rad / s). In this case, ω takes the minimum value during the operation of forming a thin film in the vapor phase growth apparatus. For example, when the source gas is silane gas, the carrier gas is hydrogen gas, and the rotation speed of the rotating substrate holder is 500 to 2,000 rpm (52 to 209 rad / s), the transition layer thickness T is about 5 to 50 mm. Therefore, it is preferable to dispose the upper surface of the rotating substrate holder at a height difference H larger than the T value from the lower end B of the small-diameter reactor upper portion 1. As a result, the gas flow from the center to the outer periphery on the wafer substrate becomes even smoother, the particles of the thin film forming raw material do not adhere to the inner wall of the furnace, and the obtained thin film forming wafer has a uniform thin film without defects in the crystal phase. It is formed.
[0028]
FIG. 6 is a schematic sectional explanatory view of another embodiment of the vapor phase growth apparatus of the present invention. In FIG. 6, a reactor 61 is vertically divided into a small-diameter upper part 1 and a large-diameter lower part 2, and a plurality of rectifying gas outlet holes 20a for discharging rectifying gas into a connecting portion 20 between the upper part 1 and the lower part 2. And a double annular portion surrounding the entire outer peripheral surface of the upper portion 1 of the reaction furnace, and the hollow annular portion 21 hermetically surrounds the connecting portion 20 in which the rectifying gas outflow hole 20a is formed. The configuration is the same as that of the apparatus in FIG. The same members as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. In the reaction furnace 51 shown in FIG. 6, the rectifying gas flows out from the rectifying gas outlet hole 20a formed in the connecting portion 20 in order to smoothly flow the unreacted gas to the

exhaust ports

15, 15. Can be. The above-mentioned carrier gas is generally used as the rectifying gas, and the same gas as the carrier gas introduced from the gas supply ports 16 of the reactor is usually discharged. The flow of the rectified gas causes a synergistic effect with the high-velocity reaction gas in the X region, so that the unreacted gas that has reached the wafer substrate W and has been subjected to thin film growth rotates without causing a gas vortex or a rough gas flow. The gas flows through the outer peripheral side of the substrate holder 12 and is smoothly discharged from the

exhaust ports

15, 15, without deposition of thin film forming components at the lower part of the reaction furnace, and the maintenance cycle of the furnace can be lengthened.
[0029]
In the reaction furnace 61 of FIG. 6, the flow rate (V _X ) And the flow rate of the rectifying gas from the rectifying gas outlet 20a (V _I ) And the ratio (V _I / V _X ) Is 0.05 to 2 (0.05 ≦ V _I / V _X It is preferable to flow out so as to satisfy ≦ 2). V _I / V _X The flow of the rectifying gas from the rectifying gas outlet hole 20a of the connecting portion 20 so that the ratio is within the above range, the flow of the reaction gas on the rotating substrate holder and the lower part of the reactor from the outer peripheral side of the rotating substrate holder. The flow of the unreacted gas into the inner space is smooth without generating a gas vortex and a rough gas flow, and a uniform high-quality thin film-formed wafer substrate having few crystal defects can be obtained. V _I / V _X Is less than 0.05, the effect of flowing the rectifying gas from the enlarged diameter portion 20a at the lower portion of the reaction furnace located outside the rotary substrate holder 12 cannot be obtained. Also, V _I / V _X Exceeds 2, the gas flow velocity at the enlarged diameter portion on the outside of the rotating substrate holder 12 becomes too fast, so that a smooth gas flow from the center to the outer periphery on the rotating substrate holder 12 is impeded, and the thickness is uniform and uniform. It is not preferable because a thin film cannot be grown.
[0030]
【Example】
Examples 1-3
A thin film was formed on a wafer substrate by using a vapor-phase growth apparatus having a circular cross section configured similarly to the hollow reaction furnace shown in FIG. The current plate 17 has a gap X from the inner wall of the reactor in an outer region (X region) having a large aperture ratio and a radius (R) of the current plate 17. _D ) And the radius of the rotating substrate holder 12, that is, the radius (R _P The boundary between the X region and the Z region is set so that the difference Y with the ratio (X / Y) shown in Table 1 is obtained. Gas holes 17a and opening ratios (%) were formed in the X region, and holes 17a and opening ratios (%) shown in Table 1 were formed in the X region. SiH as source gas ₄ Gas as carrier gas H ₂ Gas and diborane (B ₂ H ₆ ) To H ₂ The gas containing 0.1 ppm in the gas is supplied at a flow rate (V _X ) And the flow rate in the Z region (V _Z ) In Table 1 (V _X / V _Z ). Table 1 also shows the reaction temperature, the reaction pressure, and the number of rotations of the rotating substrate holder.
[0031]
B on a silicon wafer under the vapor phase growth conditions shown in Table 1. ₂ H ₆ Vapor-phase growth of a dopant silicon thin film was performed. After the vapor-phase growth thin film was formed, the adherence of particles to the inner wall of the reaction furnace of the vapor-phase growth apparatus used was visually observed. The number of LPDs of 0.135 μm or more was measured for the properties of the crystal phase on the surface of the obtained thin film-formed wafer substrate using a Surfscan 6200 manufactured by Tencor Co., and the results are shown in Table 1 as the number per wafer. Further, the thickness of the formed thin film was measured by an infrared interference film thickness meter, and the maximum thickness (F _max ) And minimum thickness (F _min ) And determine the uniformity of the thin film thickness by (F _max -F _min ) / (F _max + F _min ) × 100 and shown in Table 1. Further, the resistance value of the obtained thin film-formed wafer substrate was measured by the CV method, and the maximum value (R _max ) And the lowest value (R _min ) And determine the uniformity of the resistance value due to dopant incorporation (R _max -R _min ) / (R _max + R _min ) × 100 and shown in Table 1.
[0032]
Example 4
A thin film was formed on a wafer substrate by using a vapor-phase growth apparatus having a circular cross section configured similarly to the hollow reaction furnace shown in FIG. The current plate 17 having the aperture ratio shown in Table 2 as a whole was disposed. In the space above the current plate, a partition plate 18 is installed at the outer edge of the circle having the same diameter as that of the rotating substrate holder, and the upper space is defined as S. _X Area and S _Z It was divided into two areas. S _Z The same reaction gas as in Example 1 was supplied under the conditions shown in Table 2 and flowed into the zone. _X H in the area ₂ The gas was supplied at the flow rate shown in Table 2 and B ₂ H ₆ Vapor-phase growth of a dopant silicon thin film was performed. Table 2 shows the results of observation in the reactor and measurement of the obtained thin film-formed wafer substrate in the same manner as in Example 1.
[0033]
Examples 5 to 6
A thin film was formed on a wafer substrate by using a vapor-phase growth apparatus having a circular cross section configured similarly to the hollow reactor shown in FIG. 5 (Example 5) and FIG. 6 (Example 6). The apparatus was formed under the conditions shown in Table 2. In the sixth embodiment, H ₂ The flow rate of the reaction gas in the X region (V _X ) And the flow rate in the Y region (V _Y ) In Table 2 (V _X / V _Y ), And supply B on a silicon wafer. ₂ H ₆ Vapor-phase growth of a dopant silicon thin film was performed. Table 2 shows the results of observation in the reactor and measurement of the obtained thin film-formed wafer substrate in the same manner as in Example 1.
[0034]
[Table 1]

[0035]
[Table 2]

[0036]
Comparative Examples 1-2
V _X / V _Z A rectifying plate was formed under the conditions shown in Table 2 for Comparative Example 1 where is smaller than the predetermined value, and a rectifying plate was formed under the conditions shown in Table 2 for Comparative Example 2 where the X / Y ratio was larger than the predetermined value. A vapor phase epitaxy apparatus constructed in the same manner as the reaction furnace of Example 1 except that it was placed in the reaction furnace was used. ₂ H ₆ Vapor-phase growth of a dopant silicon thin film was performed. Thereafter, the results of observation in the reaction furnace and measurement of the obtained thin film-formed wafer substrate in the same manner are shown in Table 3.
[0037]
Comparative Examples 3 and 4
A gas phase growth apparatus shown in Table 2 was used in the same manner as in the reaction furnace of the conventional vapor phase thin film growth apparatus shown in FIG. Under the growth reaction conditions, B was placed on the silicon wafer surface in the same manner as in Example 1. ₂ H ₆ A dopant silicon thin film was formed. Thereafter, the results of observation in the reaction furnace and measurement of the obtained thin film-formed wafer substrate in the same manner are shown in Table 3.
[0038]
[Table 3]

[0039]
As is clear from the above Examples and Comparative Examples, when the flow rate of the reaction gas in the X region having a predetermined width around the inner wall of the reaction furnace is made higher by a predetermined ratio than the Z region in the center, the crystal on the surface of the obtained thin film-formed wafer substrate is obtained. When the number of LPDs in the phase is 1,000 or less, a good thin film-formed wafer substrate can be obtained. The number of LPDs is about 1/50 or less as compared with Comparative Example 1 in which the flow velocity ratio is lower than the predetermined ratio and Comparative Example 3 in which the carrier gas is circulated in the same manner as in the present embodiment by the conventional method. It is about 1/130 or less as compared with Comparative Example 2 in which the reaction gas having a high flow rate was flowed in a wide area. In Comparative Example 4 in which the carrier gas was circulated at 200 liters / minute in the conventional method, the number was 1000 or more, indicating that the thin film formation by vapor phase growth of the present invention was excellent. Also, the uniformity of the formed thin film is good although it is lower than that of Comparative Example 4, and it is clear that the uniformity of the resistance value is superior to that of Comparative Example 4. , A high quality thin film formed wafer substrate can be obtained.
[0040]
【The invention's effect】
The vapor phase growth apparatus of the present invention has various disadvantages because the reaction gas flow introduced into the reaction furnace has different flow rates in the central portion and the outer peripheral portion so that the gas flow speed in the outer peripheral portion is increased. It is possible to prevent the generated reactant gas from rising upward. Therefore, a rise in the temperature of the reaction gas can be suppressed, uniform nucleation of the thin film forming material gas is suppressed, and particles generated in the gas phase are reduced. Accordingly, since the number of particles that adhere to the reaction furnace wall and shorten the maintenance cycle or particles that adhere to the wafer and cause crystal defects are reduced, a high-quality thin film-formed wafer substrate can be manufactured. In the vapor phase thin film growth by the vapor phase thin film growth apparatus of the present invention, the gas flow in the reactor is maintained stably without generating particles, without generating turbulence or drift, and smoothly flowing through the reactor. It can flow smoothly without stagnation even on a wafer substrate on which a thin film is formed, so that re-incorporation of dopants does not occur, the in-plane resistance value of the obtained wafer substrate becomes uniform, and it is suitable for high integration. A simple wafer substrate can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic sectional explanatory view of one embodiment of a reaction furnace of a vapor phase thin film growth apparatus of the present invention.
FIG. 2 is an explanatory plan view of an embodiment of the current plate of the present invention.
FIG. 3 is an explanatory plan view of another embodiment of the current plate of the present invention.
FIG. 4 is a schematic sectional explanatory view of another embodiment of the vapor phase thin film growth apparatus of the present invention.
FIG. 5 is a schematic sectional explanatory view of another embodiment of the vapor phase thin film growth apparatus of the present invention.
FIG. 6 is a schematic sectional explanatory view of another embodiment of the vapor phase thin film growth apparatus of the present invention.
FIG. 7 is a schematic sectional view illustrating an example of a conventional vapor phase thin film growth apparatus.
[Explanation of symbols]
1 Upper part of reactor
2 Lower part of reactor
11, 41, 51, 61, 71 reactor
12,72 Rotating substrate holder
13, 73 Rotation axis
14, 74 heater
15, 75 Exhaust port
16, 19, 76 Gas supply port
17, 77 Rectifier plate
17a, 17b, 17c, 77a Rectifying hole
18 Partition plate
19, 19 ', 29 Rectifying gas introduction space
20 Connecting part
20a Rectifying gas hole
B Upper and lower end
U lower upper end
W wafer substrate
S, S _X , S _Z Space
G _X , G _Z Gas supply system
I Rectifying gas inlet
D ₁ Reactor upper inside diameter
D ₂ Reactor lower inside diameter
D _S Rotating substrate holder diameter

Claims

A plurality of reaction gas supply ports at the top of the hollow reaction furnace, an exhaust port at the bottom, a rotating substrate holder for mounting a wafer substrate inside, and a plurality of gas holes by forming a ceiling and a space in the upper inside. In a vapor phase growth apparatus having a rectifying plate with perforations, supplying a reaction gas inside and vapor-phase growing a thin film on the wafer substrate surface on the rotating substrate holder,
The hollow interior of the reaction furnace is divided into upper and lower portions having different equivalent inner diameters, the upper equivalent inner diameter is smaller than the lower equivalent inner diameter, and the upper and lower ends and the lower upper end are connected to form a continuous hollow interior. , vapor deposition apparatus, wherein a gas flow rate between the central portion and the peripheral portion in the furnace is formed differently.

The rectifying plate is in close contact with the furnace inner peripheral wall, and the opening ratio of the gas holes is an outer area in a radial direction from an outer peripheral edge of a projected shape of the rotating substrate holder that is orthogonally projected on the rectifying plate, and is more than other regions. 2. The vapor phase growth apparatus according to claim 1, wherein the size is increased.

The outer region has a predetermined interval width from the inner peripheral wall of the reaction furnace, and a difference (Y) between the interval width (X), the equivalent radius of the straightening plate ( _RD ), and the equivalent radius of the projected shape ( _RP ). = R _D -R _P) and the ratio (X / Y) is vapor deposition apparatus according to claim 2 wherein 0.02 to 1.0.

The vapor phase growth apparatus according to claim 2 or 3 , wherein the horizontal cross section of the reactor is circular, and the current plate and the rotating substrate holder are concentrically arranged.

The space area is divided into at least two sections by a partition member disposed in an outer area in a radial direction from an outer peripheral edge of a projected shape of the rotating substrate holder that is orthogonally projected on the rectifying plate therein, and is divided into each section. The vapor phase growth apparatus according to claim 1, wherein two or more reaction gas supply ports are provided.

The outer region has a predetermined interval width from the inner peripheral wall of the reaction furnace, and a difference (Y) between the interval width (X), the equivalent radius of the straightening plate ( _RD ), and the equivalent radius of the projected shape ( _RP ). = R _D -R _P) and the ratio (X / Y) is vapor deposition apparatus according to claim 5, wherein 0.02 to 1.0.

7. The vapor phase growth apparatus according to claim 5 , wherein the horizontal cross section of the reaction furnace is circular, and the current plate and the rotating substrate holder are concentrically arranged.

The vapor phase growth apparatus according to claim 5, 6 or 7 , wherein a separate reaction gas supply system is connected to the respective sections via the reaction gas supply port.

A plurality of reaction gas supply ports at the top of the hollow reaction furnace, an exhaust port at the bottom, a rotating substrate holder for mounting a wafer substrate inside, and a plurality of gas holes by forming a ceiling and a space in the upper inside. Using a vapor phase growth apparatus for supplying a reaction gas therein and vapor-growing a thin film on the surface of the wafer substrate on the rotating substrate holder by using a gas flow growth apparatus having The flow rate of the reaction gas after flow rectification in the radially outer region from the outer peripheral edge of the projected shape of the rotating substrate holder, which is orthogonally projected on the flow straightening plate, is higher than that of the other regions. In the vapor phase growth method, which is supplied on the wafer substrate surface on the rotating substrate holder,
The gas flow rate (V _XX ) And the gas flow rates (V _ZZ ) And the flow rate ratio (V _{X X} / V _ZZ ) Is in the range of 5 to 30.

The reaction gas is circulated and rectified by flowing through the rectifier plate using the vapor phase growth apparatus according to any one of claims 2 to 8, and the flow rate of the reaction gas after the flow rectification is higher in the outer region than in the other region. In the vapor phase growth method characterized by being supplied on the wafer substrate surface on the rotating substrate holder at a high speed,
The gas flow rate (V _XX ) And the gas flow rates (V _ZZ ) And the flow rate ratio (V _{X X} / V _ZZ ) Is in the range of 5 to 30.

A method of supplying a reaction gas from above into a hollow reaction furnace and rectifying, and then causing the reaction gas to flow down on a lower supported and rotated wafer substrate to vapor-phase grow a thin film on the wafer substrate surface, after the rectification. , The gas flow rate around the inner wall of the reactor (V _XX ) Is the gas flow velocity (V _{Z Z} ) In the vapor phase growth method of supplying the reaction gas so as to be faster,
The gas flow velocity (V _XX ) And the gas flow rate (V _ZZ ) And the flow rate ratio (V _XX / V _ZZ ) Is in the range of 5 to 30.