JP3570653B2

JP3570653B2 - Vapor phase thin film growth apparatus and vapor phase thin film growth method

Info

Publication number: JP3570653B2
Application number: JP35438096A
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: 2004-09-29
Anticipated expiration: 2016-12-19
Also published as: JPH10177959A

Description

【０００１】
【発明の属する技術分野】
本発明は気相薄膜成長装置及び気相薄膜成長方法に関し、特に、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汚染物の発生の少ない気相薄膜成長装置及び結晶欠陥が少なく均一な膜厚の薄膜を形成する気相薄膜成長方法に関する。
【０００２】
【従来の技術】
図８は、従来の気相成長装置の一例を示す概略説明図である。図８において、一般に円筒状の反応炉８０内の下部には、例えばシリコンウエハ等のウエハ基板８１を載置する回転基板ホルダー８２、回転基板ホルダー８２を回転させるための回転軸８３及び加熱用のヒータ８４が配設され、回転軸８３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８０底部には未反応ガス等を排気する複数の排気口８５、８５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８０の頂部には炉内に原料ガスやキャリアガスを供給する複数のガス供給管８６、８６と円盤状の整流板８７とが配設され、整流板８７には、ガスの流れを整える多数の孔８７ａ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８２上に載置された基板８１は、回転しながらヒータ８４により所定温度に加熱される。同時に、反応炉８０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８６、８６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なるように整流板８７の多数の孔８７ａを通過させ、回転基板ホルダー８２上のウエハ基板８１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、原料ガスやキャリアガスの反応炉への導入方法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とはいえず、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▼上記のように反応炉頂部より導入され均一な流速でウエハ基板８１上に供給されるシリコン原料ガス等の反応ガスは、ヒータ８４により加熱され上部より高温となっている反応炉８０の下部のウエハ基板８１近傍に到達し加熱される。その結果、図８に矢印で示したように、上昇ガス流が生じ、反応炉壁に沿って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８０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８２上のウエハ基板８１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。▲４▼更にまた、ウエハ基板近傍に流下した反応ガスの反応炉上方への舞上り現象は、ガス渦流の発生とは別に、回転基板ホルダー８２外周側に、いわゆる“ガス流の荒れ”といわれるガス流が複雑な流れとなる乱れが生じることになる。このガス流の荒れが生じると、排気口８５から排出されるべき未反応ガスが反応して回転基板ホルダー８２外周面に薄膜成分が析出したり、その回転基板ホルダー８２外周面に対向する反応炉壁にパーティクルが付着したりすることになる。
【０００６】
上記した各種の不都合を引き起こすガス渦流やガス流の荒れの発生は、従来法において回転基板保持体軸方向へのガス流速を約１ｍ／ｓ以上の極めて早い速度とすることによりある程度抑制可能である。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る。また、上記ガス渦流の発生を抑制するために反応炉上部の直径を下部に比べ細く絞り込みむことにより、高温の反応ガスが上昇する空間を閉塞することによりガス渦流の発生を防止することを試みた。しかし、この場合は反応炉上部等でのパーティクル付着等は防止できるが、下記する比較例に用いた反応炉上部径を細くした気相薄膜成長装置の概略説明図を示した図７で、例えば、矢印で図示したように、回転基板ホルダー外側に位置する反応炉径の拡大部分でガス渦流やガス流の荒れが発生することが知見された。径が拡大する部分でこのガス渦流やガス流の荒れが生じると、同様に反応炉下部周壁でパーティクルが付着したり、未反応ガスの反応により薄膜成分の析出が生じる等で問題発生の反応炉部域が変化するだけでメンテナンスサイクルが短縮する等の不都合が同様に生じることも明らかになった。
【０００７】
発明者らは上記知見に基づき、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縮等の不都合の原因が、反応炉内でのガスの上昇流のガス流の乱れにあることを見出すと共に、そのガス流の不都合が生じる上部空間部分を欠除させたり閉塞するのみでなく、径の異なる反応炉の上部と下部の連結部に整流ガス流出孔を設け径拡大部分にガス流を整流するため整流用ガスを積極的に導入させること、また、反応炉の上部径、下部径及び回転基板ホルダー径の比率を所定にすることにより、上記した従来の気相成長装置における反応炉壁や回転基板ホルダ反応炉下部で外周面へのパーティクルの多量の付着や薄膜成分の析出、ドーパントのウエハ外周部での取り込みを防止でき、そのためウエハ基板の品質低下を防止できることを見出し本発明を完成した。即ち、本発明は、シリコン原料ガスの均一核生成で発生したパーティクルが反応炉周壁で付着したり、薄膜成分の回転基板ホルダー外周部や炉内周壁への析出を防止する気相薄膜成長装置を提供し、同時に欠陥が少なく高品質で均一な薄膜をウエハ基板上に気相成長させる方法を提供するものである。
【０００８】
【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、内部上部に複数の孔が穿設された整流板を有し、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、前記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連結部により接続され中空内部が連続すると共に、該連結部に整流ガス流出孔を有し、前記整流板が反応炉上部内の上方に内周面に密接して配備され、前記回転基板保持体が反応炉下部内の該上部下端より所定の高低差を有して下方に位置して配設されることを特徴とする気相薄膜成長装置が提供される。
【０００９】
上記本発明の気相薄膜成長装置において、更に、前記連結部上に、前記整流ガス流出孔を気密に包囲してなる空間部が配設され、該空間部に整流ガス供給口を有することが好ましい。また、前記上部の側面が前記回転基板保持体上面に対し垂直であることが好ましく、前記空間部と上部とが二重環状に形成されており、前記空間部の外側面が連結部を介して前記下部上端に連続することが好ましい。更に、前記反応炉中空内部の水平断面が円形であって、前記上部直径（Ｄ₁）が、前記ウエハ基板の直径より大であり、且つ、前記回転基板保持体が円形でその直径（Ｄ_S）との比（Ｄ₁／Ｄ_S）が０．７〜１．２であることが好ましく、上部直径（Ｄ₁）と下部直径（Ｄ₂）との比（Ｄ₂／Ｄ₁）が１．２以上であることが好ましく、下部直径（Ｄ₂）と回転基板保持体直径（Ｄ_S）との比（Ｄ₂／Ｄ_S）が１．２以上であることが好ましい。更にまた、前記上部下端と回転基板保持体との高低差（Ｈ）が、該回転基板保持体上面上のガス流の遷移層厚（Ｔ）＝３．２２（ν／ω） ^1/2 （但し、νは反応炉内雰囲気ガスの動粘性係数（ｍｍ ² ／ｓ）を、ωは回転の角速度（ｒａｄ／ｓ）をそれぞれ表示する）より大であることが好ましい。
【００１０】
また、本発明によれば、上記の気相成長装置において、回転基板保持体上部のガス流の遷移層厚（Ｔ）＝３．２２（ν／ω） ^1/2 （但し、νは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）が、前記上部の下端と前記回転基板保持体上面との高低差（Ｈ）より小さくなるように、前記複数の反応ガス供給口から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て整流板の孔を通過させて前記ウエハ基板上に流通させると同時に、前記連結部の整流ガス流出孔を通過させて整流用ガスを導入することを特徴とする気相薄膜形成方法が提供される。また、本発明の気相薄膜成長方法において、前記キャリアガス流速（Ｇ_C）と前記連結部の整流ガス流出孔から導入される整流用ガス流速（Ｇ_I）の比（Ｇ_I／Ｇ_C）が０．０５〜２であることが好ましい。
【００１１】
本発明の気相薄膜成長装置は上記のように構成されて、従来の気相薄膜成長装置における反応炉壁に沿って生じる反応ガスの舞上り現象によるガス渦流発生を、上部径を下部径より小さくするという炉形状を変更して発生空間を欠除させることで抑制できると同時に、反応炉上部での気相温度の上昇を防止できることから、シリコン等薄膜形成の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。そのため、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の原因となったり、直接付着パーティクルとなりウエハの品質を低下すること等が防止される。また、ガス渦流の発生抑制は、回転基板ホルダー上に載置されたウエハ直上のガス流が、ウエハ中心から外周部へウエハ面に平行に流れることを妨害されることなく均等となる。そのため基板外周部での気相中のドーパントの再取込が生じることもなく、面内抵抗値分布が均一な高品質な薄層形成ウエハ基板を得ることができる。更に、反応炉上部を細くしたことから、比較的少ないキャリアガス量で回転基板保持体軸方向のガス流速を高くすることができ、従来の装置に比しキャリアガス量が低減される。
【００１２】
また、反応炉の小径の上部の下端と大径の下部の上端とを連結する連結部に整流ガス流出孔を配備して、水素等の整流用ガスを所定流速で流出することができることから、回転基板ホルダー上に発生する中心から外周へのガス流れが整流されて、前記した反応炉上部径を下部より細くすることにより生じる回転基板ホルダー外周側の径の拡大する下部でのいわゆるガス流の荒れを抑制することができる。それにより、拡大径の連結部内壁や反応炉下部へのパーティクル付着や薄膜形成成分の析出を防止することができる。更に、反応炉上部径、反応炉下部径及び回転基板保持体直径の比率を所定とすることから、反応炉内のガスの上昇流を防止してパーティクル発生を減少させると共に、ガス渦流やガス流の荒れの発生を防止することができ、更に、炉壁に付着したパーティクルが回転基板保持体上のウエハ基板上に落下することを回避することができる。
【００１３】
更にまた、回転基板保持体を、反応炉下部で連結部の上端である反応炉の上部下端より下方に高低差を有して配設し、特に、回転基板保持体上面に形成されるガス流の遷移層厚より大きい高低差とすることから、上部下端が円滑なガス流れを妨害することがなく、また、ガスの上昇流を防止して、ガス渦流やガス流の荒れが発生することがなく、結晶欠陥がなく高品質の薄膜形成ウエハ基板を得ることができる。また、本発明の気相薄膜成長方法は、上記の装置を用いると共に、反応ガスの導入流速、連結部からの整流用ガスの流出流速及ぶ回転基板保持体の回転速度等を制御して、回転基板保持体上に形成されるガス流の遷移層厚より、回転基板保持体上面と反応炉上部下部との高低差を大きいすることから、同様に結晶欠陥がなく高品質の薄膜をウエハ基板上に気相成長させることができる。
なお、本発明において、遷移層とは、整流板を経て供給された原料ガス流が、回転基板保持体上において中心から外周辺部方向へのベクトルを有して流れるガス層をいい、遷移層厚は回転基板保持体上における上記ベクトルを有するガス流の厚さをいう。
【００１４】
【発明の実施の形態】
以下、本発明の一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。
図１は本発明の気相薄膜成長装置の一実施例の概略断面説明図である。図１において、反応炉１０は上部１と下部２とに区分され上部１が下部２より細く形成される。即ち、上部内径Ｄ_１が下部内径Ｄ_２より小さくＤ_１＜Ｄ_２である。反応炉１０を区分する上下部の各高さＨ_１及びＨ_２の比、即ち、区分比率は特に制限されるものでなく、下部２内に回転基板保持体等が所定に配設されればよい。通常、Ｈ_１／Ｈ_２＝０．５〜２．０である。反応炉１０は、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１８により接続され、上下部の径は異なるが反応炉の内部中空間が連続される。また、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１８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。本発明の気相薄膜成長装置の反応炉には、上記連結部１８には整流用ガスを流出するための整流ガス流出孔１８ａが複数穿設される。
【００１５】
図１において、更に、大径の反応炉下部２には、ウエハ基板１１を載置する回転基板保持体１２が回転軸１３により回転自在に支持され配設され、その下方には回転基板保持体１２及びその上に載置されるウエハ基板１１とを加熱するヒータ１４が配設される。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。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１０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、反応炉上部１には、頂部に複数の反応ガス供給口１６、１６が配設され、例えばシラン（ＳｉＨ_４）、ジクロロシラン（ＳｉＨ_２Ｃｌ_２）等の原料ガス及び水素（Ｈ_２）、ヘリウム（Ｈｅ）、アルゴン（Ａｒ）等のキャリアガスの反応ガスが供給される。反応炉上部１内の上方は頂部と所定の空間域Ｓを保持して複数の孔１７ａが穿設された円盤状の整流板１７が、供給ガスが偏流路を形成することがないように反応炉上部の内周面に密接して配備される。
【００１６】
上記連結部１８に穿設された整流ガス流出孔１８ａ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が流出される。整流用ガスとしては、一般に上記キャリアガスが用いられ、通常、反応炉頂部のガス供給口１６、１６から供給されるキャリアガスと同一のガスが流出される。これにより反応ガスがウエハ基板１１に達し薄膜成長に供された後、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外周側から円滑に流通して排気口１５、１５から排出することができる。整流ガス流出孔１８ａへの整流用ガスの導入は、各整流ガス流出孔１８ａから均等に整流用ガスが流出されればよく特に制限されない。例えば、整流ガス流出孔１８ａ毎に導入管を配備してそれぞれ各別に整流用ガスを導入することもできる。また、図１に示したように、連結部１８上に整流ガス流出孔１８ａを気密に包囲して、整流ガス供給口Ｉを有する整流ガス導入空間部１９を配設し、整流ガス導入空間部１９に整流用ガスを供給してもよい。この場合、整流ガス供給口Ｉ’を有する整流ガス導入空間部１９’のように、反応炉上部１の外周面全域を包囲して反応炉１０の上部を二重環形状に形成し、中空内部を反応炉上部１とし、中空環状部を整流ガス導入空間部とすることもできる。この二重環形状は、反応炉の製造上簡便であり好ましい。
【００１７】
本発明の気相薄膜成長装置は、上記のように回転基板保持体１２は、そ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を有する。この高低差Ｈは、通常、回転基板保持体１２上部に供給されるガス流の遷移層、即ち、図１に矢印にて示したように整流板１７を経て供給された原料ガス等のガス流が回転基板保持体１２上で中心から外周辺部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る。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１１の中心から外周部へのガス流れが、反応炉上部１の下端Ｂにより阻害され、反応炉内壁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ため、連結部１８や反応炉下部２の内壁への析出物が多量となるためである。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１８と同一水平面内にあることが好ましい。
【００１８】
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、流体力学において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は気相薄膜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。
【００１９】
また、本発明の気相薄膜成長装置の異なる径を有する上下部からなる反応炉において、反応炉上部１の小径Ｄ_１、下部２の大径Ｄ_２、回転基板保持体１２の直径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より小さいと、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が発生し、反応炉上部径を細くしてガス舞上り現象を防止しガス渦流の発生の抑制効果が低下するためである。
【００２０】
（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より大きいと、Ｄ_２／Ｄ_１比が１．２より小さい場合と同様に、反応炉内壁に沿ってガス流が上方への舞上り現象が生じガス渦流の発生が起こる等の不都合があるためである。（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外側のガス流の荒れが抑制できないため、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するためである。
【００２１】
上記したように本発明の気相薄膜成長装置は、反応炉が上下部で区分されて異なる径を有して連続する中空筒体で、異なる径の上下部の連結部に整流ガス流出孔を有し、且つ、各部材を上記した所定に配設する以外は、前記の従来の気相薄膜成長装置の同一径の中空筒体からなる反応炉とほぼ様にして設計、製造することができる。また、本発明の気相薄膜成長装置を用いて行う気相成長方法も同様に行うことができる。上記のように構成された本発明の気相薄膜成長装置において、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１０内を排気し、炉内圧力、例えば原料ガスやキャリアガスの反応ガスで２０〜５０ｔｏｒｒに調整する。一方、回転基板保持体１２はモータを稼働し回転軸１３の回転駆動により回転し、その上のウエハ基板１１が同時に回転させられると同時に、ヒータ１４により回転基板保持体１２上のウエハ基板１１は、例えば約９００〜１２００℃に加熱される。また同時に、複数の反応ガス供給口１６、１６からは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１０内に供給する。複数の反応ガス供給口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の孔１７ａを通過することにより反応炉内のガス流速分布を均一にして基板上に供給され、基板上に薄膜を均一に気相成長させることができる。本発明の気相薄膜成長装置においては、上記反応ガスの供給と同時に、連結部１８の整流ガス流出口１８ａから整流用ガスとして通常キャリアガスと同一ガスを流出する。
【００２２】
この場合、反応ガス供給口１６からの反応ガス流速（Ｇ_Ｃ）と連結部１８の整流ガス流出孔から導入される整流用ガス流速（Ｇ_Ｉ）の比（Ｇ_Ｉ／Ｇ_Ｃ）が０．０５〜２（０．０５≦Ｇ_Ｉ／Ｇ_Ｃ ≦２）となるように流出することが好ましい。Ｇ_Ｉ／Ｇ_Ｃ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の拡大部分でガス流の荒れが生じるため好ましくない。また、Ｇ_Ｉ／Ｇ_Ｃが２を超えると、同様に回転基板保持体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上での回転基板保持体１２中心から外周への円滑なガス流れを阻害するため、均一厚で均質な薄膜成長ができず好ましくない。反応ガス供給口からの反応ガスとの比率Ｇ_Ｉ／Ｇ_Ｃが上記範囲内で整流用ガスを連結部１８の整流ガス流出孔１８ａより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に行われる。これにより、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。
【００２３】
上記連結部に設けられる整流ガス流出孔の配置は、上方へのガスの舞上りによるガス渦流の発生と反応炉の径拡大部でのガス流の荒れの発生を防止できればよく、反応炉の容量、反応ガスの種類、反応ガス流速、回転基板保持体の回転速度等反応条件に応じて適宜選択することができ、特に制限されるものでない。通常、図１の矢印で示した整流ガス流れのように、ガス流出速度が均等に分布するように連結部１８全域に同一径の流出孔を均等に配置する。また、整流用ガスの流出速度分布に勾配をもたせるために、整流ガス流出孔の孔径が所定の分布で孔径を変化させて配置してもよい。例えば、図２に示す気相薄膜成長装置の他の実施例の模式図において、連結部２８の整流ガス流出孔２８ａからの整流ガスの流れを矢印で示したように、連結部からの整流ガス流速が反応炉下部２の内周壁側で速く中心側で遅くなるように流速分布に勾配を有するように流出させることができる。なお、図２において、図１に示した装置と同様の部材は、一の位の数値を同一にして付すか、又は同一の符号で示した（以下、同様とする）。上記のような内周壁側から中心方向へ流速が遅くなる整流用ガス流に勾配を持たせるためには、例えば、図３の連結部２８部分の平面模式図に示したように整流ガス流出孔２８ａを配置することができる。即ち、流出孔を内周壁側に多く中心側に少なく配置して穿設する方式である。このように整流用ガスを所定の流速勾配を有するように流出することにより、ガス渦流やガス流の荒れの発生を防止し反応ガスの流れを整流して、未反応ガスを反応炉下部から円滑に排気するために効果的である。
【００２４】
本発明において、整流用ガスの流出方向は特に制限されない。通常、上記の図１及び図２に示したように回転基板保持体面に垂直に流出させる。しかし、必要に応じて垂直方向以外の方向に流出することもできる。即ち、連結部に整流ガス流出孔を回転基板保持体の回転軸に平行な垂直方向でなく角度を有するように穿設させることにより、その整流ガス流出孔から整流用ガスを回転基板保持体の回転軸に対して所定角度で流出させることができる。例えば、図４は連結部領域の一例の拡大部分断面説明図である。図４において、連結部４８の整流ガス流出孔４８ａは、反応炉の内周壁方向へ所定角度で傾斜して穿設されている。整流ガス流出孔４８ａからの整流ガスは、内周壁方向へ回転軸から遠ざかるように流出する。このような整流ガス流出孔構造は、回転体近傍のガス流れを荒ささないため好ましい。この場合の傾斜角度は、通常、回転基板保持体の回転軸に対し約１０〜８０度で反応炉の内周壁方向へ傾斜させる。回転軸方向へ傾斜させた場合は回転体近傍から掃き出されたガス流れを荒すため好ましくない。
【００２５】
また、整流用ガスを回転基板保持体の回転方向と一致して流出させてもよい。例えば、図５は、円環状連結部５８の整流ガス流出孔５８ａを周方向に所定角度で傾斜させ穿設した連結部部分の一例を一部切欠いて示した斜視模式図である。図５において、ガス流入面の整流ガス流出孔５８ａの孔口５８Ｘから周方向に傾斜して裏面のガス流出面の孔口５８Ｙに連通するように穿設されている。整流ガス流出孔５８ａからの整流用ガスは、回転基板保持体の回転と同一の周方向に流出する。この整流ガス流出孔構造は、回転体近傍のガス流れを荒さないため好ましい。この場合の傾斜角度も、通常、連結部のガス流入面に対し約１０〜８０度で周方向に傾斜させる。更に、整流ガス流出孔を周方向に傾斜すると同時に径の中心方向にも傾斜させて、回転基板保持体の回転方向に整流用ガスを流出することもできる。図６は円環状連結部６８の整流ガス流出孔６８ａを周方向及び円環中心方向に所定角度で傾斜させ穿設した連結部部分の一例を示した平面模式図である。図６において、ガス流入面６Ｆの整流ガス流出孔６８ａの孔口６８Ｘから周方向及び円環中心方向に傾斜して裏面のガス流出面の孔口６８Ｙに連通するように穿設されている。整流ガス流出孔６８ａから整流用ガスは、回転基板保持体の回転方向と同一方向に回転するように流出する。この整流ガス流出孔構造は、回転体近傍のガス流れを荒さないため好ましい。この場合の傾斜角度は、通常、連結部のガス流入面に対し約１０〜８０度で、且つ、周方向に対し約１０〜８０度に傾斜させる。
【００２６】
【実施例】
実施例１〜３
前記図１に示した反応炉と同様に中空円筒に構成され、反応炉上部内径Ｄ_１、下部内径Ｄ_２及び回転基板保持体直径Ｄ_Ｓがそれぞれ表１に示した径を有し、また、上部下端Ｂと回転基板保持体上面とが表１に示した高低差Ｈを有するように配設した気相成長装置を用いた。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、それぞれ表１に示した流量で供給すると共に、連結部からキャリアガスと同じＨ_２ガスを整流用ガスとして表１に示した流量で垂直方向に均一に流出した。反応ガス流速（ｍ／ｓ）と整流用ガス流速（ｍ／ｓ）との比（Ｇ_Ｉ／Ｇ_ｃ）、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。
【００２７】
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連結部及び反応炉下部内周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（ウエハ表面レーザー散乱体）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Ｃ−Ｖ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。
【００２８】
【表１】

【００２９】
比較例１〜２
整流用ガスを表１に示したように極少量（比較例１）または大量（比較例２）に連結部から流出した以外は、実施例１の反応炉と同様に構成された気相薄膜成長装置を用い、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、装置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１に示した。
【００３０】
比較例３〜１３
図７に概略断面説明図を示した気相薄膜成長装置の反応炉７０を用いて実施例１と同様にウエハ基板上にシリコン薄膜を気相成長させた。図７において、反応炉７０は、小径の上部１’と大径の下部２’の上下部の内径が異なり、上下部を接続する連結部７８に整流ガス流出孔が設けられていない以外は実施例１の気相薄膜成長装置の反応炉と全く同様に構成されている。図１に示した装置と同様の部材は、一の位の数値を同一番号として示すか、または同一の符号で示した。反応炉７０において、反応炉上部内径Ｄ_１、下部内径Ｄ_２及び回転基板保持体直径Ｄ_Ｓの比率を表２及び表３に示したように変化させ、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、装置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２、表３及び表４に示した。
【００３１】
【表２】

【００３２】
【表３】

【００３３】
比較例１４〜１５
前記図８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、上下部に区分がなく上下同径で連結部の無い反応炉８０と同様に構成された反応炉を用い、表４に示した実施例１と同様の気相成長反応条件下で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、装置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４に示した。
【００３４】
【表４】

【００３５】
上記実施例及び比較例より明らかなように、反応炉を径の異なる上下部に区分し上下部の径が拡大する連結部から整流用ガスを所定に流出させることにより、得られる薄膜形成ウエハ基板表面の結晶相のＬＰＤ個数も、１００以下で同一条件で従来の気相成長装置を用いた比較例１４に比し、約１／３００以下に低減されることが分かる。更に、形成される薄膜厚の均一性が１以下で極めて均一な薄膜が形成されることが明らかである。また、抵抗値の均一性も４．４以下と結晶相の欠陥のなさと共にドーパントの再取込みも防止され均質な薄膜が形成されることも分かる。また、比較例１５のように従来の装置でキャリアガス流量を大量に流通させた場合は、膜厚は比較的均一でＬＰＤも少なく結晶相も比較的良好であるが、抵抗値の均一性が劣り、回転基板保持体の外周側でガス流の荒れが生じたことが推定できる。また、反応炉下部で析出物が多く炉のメンテナンスサイクルが短縮されることが予測できる。
【００３６】
一方、比較例３〜１３のように、上下部の径が異なり区分された反応炉を用いた場合でも、連結部からの整流用ガスの流出を行わない場合は、実施例と同様の径比率の比較例３においては、従来の通常のキャリアガス流量の場合（比較例１４）より、膜均一性、抵抗値均一性、ＬＰＤ個数、反応炉下部の析出物量の多少のいずれも優れるものであるが、整流用ガスを流出した実施例に比して低下していることが明らかである。また、炉上下部の径と回転基板保持体の直径との比率を各種変化させた場合でも、実施例に比して良好な結果を得ることができないことが分かる。なお、下部径を上部径に比し３〜４倍に大きくした比較例８及び９においては比較的良好な薄膜が形成されるが、装置寸法が大きくなりすぎる等の不都合があり、また、連結部での析出物があり結晶相の欠陥が多少増加し、反応炉のメンテナンスサイクルも短縮されることから好ましくない。また、反応炉の上部下端Ｂと回転基板保持体上面との高低差を５ｍｍと近接させた比較例１２においては、ＬＰＤ個数が著しく増加し、結晶相の欠陥、薄膜厚の均一性、抵抗値の均一性が著しく損なわれることが分かる。
【００３７】
更に、比較例１〜２によれば、本発明の気相薄膜成長装置の反応炉を用いて、連結部からの整流用ガスの流速が反応ガスの流速に比して少ない場合は、得られる薄膜は比較的良好であるのに対し、反応ガスの３倍の流出量ではＬＰＤ個数が著しく増加し、連結部の析出物はないが反応炉下部での析出量が増大し、得られる薄膜性状も低下することが分かる。
なお、上記実施例及び比較例における遷移層厚Ｔは、上記式（１）によりω＝２０９ｒａｄ／ｓ、ν＝６６０８〜８８１１ｍｍ^２／ｓを導入した算出値が１８〜２１ｍｍであった。
【００３８】
【発明の効果】
本発明の気相薄膜成長装置は、反応炉を小径の上部と大径の下部とで上下部を区分し上部下端と下部上端を接合して中空内部空間を連続させて構成し、反応ガスの上昇空間が欠除することから、反応ガスの上方への舞上り現象を防止できる。また、そのため反応ガスの温度上昇も抑止でき、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、上下部接合の連結部にガス流出孔を設け、反応ガスと同時に整流用ガスを流出させ、反応炉下部の排気口へのガス流れを整流に安定化することから、ウエハ基板を載置する回転基板保持体上のガス渦流の発生を防止すると共に、その外周側で反応ガス流が乱流となりガス流の荒れを防止でき、連結部は反応炉下部での析出物を防止することでき、反応炉のメンテナンスサイクルを長期に維持できる。
結局、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て、炉内壁へのパーティクルの付着もなく、ウエハへの付着パーティクルの増加を防止して結晶欠陥がなく高品質で膜厚が均一な薄膜形成ウエハ基板を得ることができ、高集積化用として好適なウエハ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一実施例の概略断面説明図
【図２】本発明の気相薄膜成長装置の他の実施例のガス流れを示す断面模式図
【図３】図２の気相薄膜成長装置における連結部の平面模式図
【図４】本発明の気相薄膜成長装置の他の実施例における連結部領域の断面模式図
【図５】本発明の気相薄膜成長装置の他の実施例における連結部の一部切欠き斜視模式図
【図６】本発明の気相薄膜成長装置の他の実施例における連結部の平面模式図
【図７】本発明の比較例に用いた気相薄膜成長装置の概略断面説明図
【図８】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】
１０、２０、７０、８０反応炉
１１、２１、４１、５１、７１、８１ウエハ基板
１２、２２、４２５２、７２、８２回転基板保持体
１３、２３、４３、７３、８３回転軸
１４、２４、４４７４、８４ヒータ
１５、２５、７５、８５排気口
１６、２６、７６、８６ガス供給口
１７、２７、７７、８７整流板
１７ａ、２７ａ、７７ａ、８７ａ整流孔
１８、２８、７８連結部
１８ａ、２８ａ、７８ａ整流ガス流出孔
１９、１９’、２９整流ガス導入空間
１、１’ 反応炉上部
２、２’ 反応炉下部
Ｓ空間部
Ｂ上部下端
Ｕ下部上端
Ｉ、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
The present invention relates to a vapor-phase thin-film growth apparatus and a vapor-phase thin-film growth method, and more particularly, to a vapor-phase thin-film growth apparatus and a method for reducing the occurrence of contaminants applied to the manufacturing process of a semiconductor wafer substrate requiring high quality. The present invention relates to a vapor phase thin film growth method for forming a thin film having a uniform thickness.
[0002]
[Prior art]
FIG. 8 is a schematic explanatory view showing an example of a conventional vapor phase growth apparatus. 8, a rotary substrate holder 82 on which a wafer substrate 81 such as a silicon wafer is mounted, a rotary shaft 83 for rotating the rotary substrate holder 82, and a heating A heater 84 is provided, and a rotating motor (not shown) is connected to the rotating shaft 83. Further, a plurality of exhaust ports 85 for exhausting unreacted gas and the like are provided at the bottom of the reaction furnace 80 and connected to an exhaust control device (not shown). On the other hand, a plurality of

gas supply pipes

86, 86 for supplying a raw material gas and a carrier gas into the furnace and a disk-shaped current plate 87 are provided at the top of the reaction furnace 80. Many holes 87a are provided for adjusting the height. The conventional vapor phase epitaxy apparatus is configured as described above, and the substrate 81 placed on the rotating substrate holder 82 that rotates at a predetermined rotation speed by the rotation of the motor is heated to a predetermined temperature by the heater 84 while rotating. Is done. At the same time, a reaction gas such as a raw material gas and a carrier gas is introduced into the reaction furnace 80 through a plurality of gas supply pipes 86 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 81 on the rotating substrate holder 82 by passing through a large number of holes 87a of the current plate 87 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 method of introducing a source gas and a carrier gas into a reaction furnace is set to a predetermined value, thereby making the gas momentum and the gas pressure uniform so that the source gas and the like are deposited on the substrate at a uniform flow rate. It is intended to make the thickness of the thin film uniform.
[0004]
[Problems to be solved by the invention]
However, even in the conventional vapor-phase growth apparatuses of the above-mentioned various proposals, it is not possible to say that crystal defects are generated on a wafer substrate on which a thin film is grown, or that inconveniences such as particle adhesion can not be sufficiently prevented. With ultra-high integration in semiconductors, wafer substrates have been required to have higher and higher quality, and the quality of slight defects in thin-film-formed wafer substrates has often become a problem. . 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)} a reaction gas such as a silicon source gas introduced from the top of the reaction furnace and supplied onto the wafer substrate 81 at a uniform flow rate as described above is heated by the heater 84 and has a higher temperature than the upper part of the reaction furnace. It reaches the vicinity of the wafer substrate 81 below the substrate 80 and is heated. As a result, as shown by an arrow in FIG. 8, a rising gas flow is generated, a rising phenomenon of the reaction gas is generated along the reactor wall, and a gas vortex is generated. {Circle around (2)} Since the heated reaction gas rises, the temperature of the entire region inside the reaction furnace 80 also rises, and 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 above-mentioned gas vortex is generated, the dopant in the reaction gas may be re-introduced at the outer peripheral portion of the wafer substrate 81 on the rotating substrate holder 82, and the in-plane resistance value distribution of the obtained wafer substrate may be generated. Causes non-uniformity. {Circle around (4)} Further, the soaring phenomenon of the reactant gas flowing down near the wafer substrate to the upper part of the reactor is called "roughness of gas flow" on the outer peripheral side of the rotary substrate holder 82, separately from the generation of gas vortex. The turbulence that the gas flow becomes a complicated flow will occur. When the gas flow becomes rough, the unreacted gas to be discharged from the exhaust port 85 reacts to deposit a thin film component on the outer peripheral surface of the rotating substrate holder 82 or a reaction furnace facing the outer peripheral surface of the rotating substrate holder 82. Particles may adhere to walls.
[0006]
The generation of the gas vortex and the roughening of the gas flow which cause the various inconveniences described above can be suppressed to some extent by setting the gas flow velocity in the axial direction of the rotating substrate holder to an extremely high speed of about 1 m / s or more in the conventional method. . However, for that purpose, it is necessary to flow a large amount of carrier gas. In addition, in order to suppress the generation of the gas vortex, the diameter of the upper part of the reactor is narrowed down compared to the lower part, so as to block the space where the high temperature reaction gas rises, and try to prevent the generation of the gas vortex. Was. However, in this case, it is possible to prevent particles from adhering to the upper part of the reaction furnace and the like, but FIG. 7 is a schematic explanatory view of a vapor phase thin film growth apparatus having a reduced diameter of the upper part of the reaction furnace used in the comparative example described below. As shown by arrows, it was found that gas swirling and roughening of the gas flow occur at the enlarged portion of the reactor diameter located outside the rotary substrate holder. If this gas vortex or gas flow becomes rough in the area where the diameter increases, the reactor also causes problems such as particles adhering to the lower peripheral wall of the reactor and deposition of thin film components due to the reaction of unreacted gas. It has also been clarified that inconveniences such as shortening of the maintenance cycle also occur simply by changing the area.
[0007]
Based on the above knowledge, the inventors have found that the cause of 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 is turbulence of the gas flow of the upward flow of gas in the reactor. In addition to finding out and closing the upper space where the inconvenience of the gas flow occurs, a rectifying gas outlet hole is provided in the upper and lower connecting parts of the reactors having different diameters, and gas is increased in the enlarged diameter part. By introducing a rectifying gas actively to rectify the flow, and by setting the ratio of the upper diameter, the lower diameter, and the rotating substrate holder diameter of the reaction furnace to a predetermined value, the reaction in the above-described conventional vapor phase growth apparatus is performed. Prevents a large amount of particles from adhering to the outer peripheral surface, deposition of thin film components, and incorporation of dopants at the outer peripheral part of the wafer at the furnace wall and the lower part of the rotating substrate holder reactor, thereby preventing deterioration of the quality of the wafer substrate. And completed the present invention found that the kill. That is, the present invention provides a vapor phase thin film growth apparatus that prevents particles generated by uniform nucleation of a silicon source gas from adhering on the peripheral wall of a reaction furnace and preventing deposition of thin film components on the outer peripheral part of the rotating substrate holder and the inner peripheral wall of the furnace. The present invention also provides a method for vapor-phase growing a high quality and uniform thin film on a wafer substrate with few defects.
[0008]
[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 for mounting a wafer substrate inside, and a plurality of holes are provided at the top inside. In a vapor phase growth apparatus having a rectifying plate for supplying a reaction gas into the inside and vapor-phase growing a thin film on the surface of a wafer substrate on a rotating substrate holder, the inside of the hollow of the reaction furnace has upper and lower The upper part has an equivalent inner diameter smaller than the lower part, and the upper lower end and the lower upper end are connected by a connecting part, the hollow interior is continuous, and the connecting part has a rectifying gas outlet hole,The straightening vane is disposed closely above the inner peripheral surface in the upper part of the reactor,An apparatus for growing a vapor phase thin film is provided, wherein the rotating substrate holder is disposed below a lower end of the upper portion of the reactor with a predetermined height difference.
[0009]
In the above-mentioned vapor phase thin film growth apparatus of the present invention, a space portion surrounding the rectification gas outflow hole in an airtight manner may be provided on the connection portion, and the space portion may have a rectification gas supply port. preferable. Further, it is preferable that a side surface of the upper portion is perpendicular to an upper surface of the rotating substrate holder, the space portion and the upper portion are formed in a double annular shape, and an outer surface of the space portion is connected via a connecting portion. Preferably, it is continuous with the lower upper end. Furthermore, the horizontal cross section inside the reactor hollow is circular, and the upper diameter (D₁) Is larger than the diameter of the wafer substrate, and the rotating substrate holder is circular and has a diameter (D_S) And the ratio (D₁/ D_S) Is preferably 0.7 to 1.2, and the upper diameter (D₁) And lower diameter (D_Two) And the ratio (D_Two/ D₁) Is preferably 1.2 or more, and the lower diameter (D_Two) And the rotating substrate holder diameter (D_S) And the ratio (D_Two/ D_S) Is preferably 1.2 or more. Further, the height difference (H) between the upper and lower ends and the rotating substrate holder is determined by the transition layer thickness (T) of the gas flow on the upper surface of the rotating substrate holder.= 3.22 (ν / ω) ^1/2 (Where ν is the kinematic viscosity coefficient of the atmosphere gas in the reactor (mm ^Two / S) and ω indicates the angular velocity of rotation (rad / s) respectively)Is preferred.
[0010]
Further, according to the present invention, in the above-described vapor phase growth apparatus, the transition layer thickness (T) of the gas flow above the rotating substrate holder is provided.= 3.22 (ν / ω) ^1/2 (Where ν is the kinematic viscosity coefficient of the reaction gas (mm ^Two / S), and ω indicates the angular velocity of rotation (rad / s).)Is supplied from a plurality of reaction gas supply ports to supply a reaction gas comprising a thin film forming raw material gas and a carrier gas so that the height difference between the lower end of the upper portion and the upper surface of the rotating substrate holder is smaller than the height difference (H). A gas phase thin film forming method is provided, wherein a gas for rectification is introduced through a rectification gas outflow hole of the connecting portion while passing through a hole of a plate and flowing on the wafer substrate. Further, in the vapor phase thin film growth method of the present invention,,The carrier gas flow rate (G_C) And the flow velocity of the rectifying gas (G_I) Ratio (G_I/ G_C) Is preferably from 0.05 to 2.
[0011]
The vapor phase thin film growth apparatus of the present invention is configured as described above, and generates gas vortex flow due to the reaction gas rising phenomenon occurring along the reaction furnace wall in the conventional vapor phase thin film growth apparatus. By suppressing the generation space by changing the furnace shape to make it smaller, it is possible to suppress the rise of the gas phase temperature in the upper part of the reactor and at the same time, the uniform nucleation of the raw material gas for thin film formation such as silicon is suppressed. As a result, particles generated in the gas phase are reduced. Therefore, it is possible to prevent the particles from adhering to the reaction furnace wall and shortening the maintenance cycle, from adhering to the wafer to cause crystal defects, and from directly adhering particles and deteriorating the quality of the wafer. Further, the generation of the gas vortex is suppressed uniformly without obstructing the gas flow immediately above the wafer placed on the rotating substrate holder from flowing from the center of the wafer to the outer periphery in parallel with the wafer surface. Therefore, a high-quality thin-layer-formed wafer substrate having a uniform in-plane resistance value distribution can be obtained without re-incorporation of the dopant in the gas phase at the outer peripheral portion of the substrate. Further, since the upper portion of the reactor is made thinner, the gas flow rate in the axial direction of the rotating substrate holder can be increased with a relatively small amount of carrier gas, and the amount of carrier gas is reduced as compared with the conventional apparatus.
[0012]
In addition, a rectifying gas outlet is provided at a connecting portion connecting the lower end of the upper portion of the small diameter and the upper end of the lower portion of the large diameter of the reactor, so that a rectifying gas such as hydrogen can flow out at a predetermined flow rate. The gas flow from the center to the outer periphery generated on the rotating substrate holder is rectified, and the so-called gas flow at the lower portion where the diameter of the outer periphery of the rotating substrate holder is increased by making the reactor upper diameter smaller than the lower portion. Roughness can be suppressed. As a result, it is possible to prevent particles from adhering to the inner wall of the connecting portion having an enlarged diameter or the lower part of the reaction furnace and the deposition of the thin film forming component. Furthermore, since the ratio of the upper diameter of the reactor, the lower diameter of the reactor, and the diameter of the rotating substrate holder is set to a predetermined value, the upward flow of gas in the reactor is prevented to reduce the generation of particles, and the gas vortex and gas flow This makes it possible to prevent the occurrence of roughening, and also to prevent particles adhering to the furnace wall from falling onto the wafer substrate on the rotating substrate holder.
[0013]
Furthermore, the rotating substrate holder is disposed with a difference in height below the upper lower end of the reactor, which is the upper end of the connecting portion, at the lower part of the reactor, and particularly, the gas flow formed on the upper surface of the rotating substrate holder. Since the height difference is larger than the transition layer thickness, the upper and lower ends do not obstruct the smooth gas flow, and also prevent the gas from flowing upward, so that the gas vortex and the gas flow may be roughened. It is possible to obtain a high quality thin film formed wafer substrate without any crystal defects. Further, the vapor phase thin film growth method of the present invention uses the above-described apparatus and controls the rotation speed of the rotating substrate holder by controlling the flow velocity of the reaction gas, the flow velocity of the rectifying gas from the connection part, and the rotation speed of the rotating substrate holder. Since the height difference between the upper surface of the rotating substrate holder and the lower part of the reactor is larger than the transition layer thickness of the gas flow formed on the substrate holder, a high-quality thin film with no crystal defects is similarly deposited on the wafer substrate. Vapor phase growth.
In the present invention, the transition layer refers to a gas layer in which the source gas flow supplied via the current plate flows with a vector from the center to the outer peripheral direction on the rotating substrate holder. The thickness refers to the thickness of the gas flow having the above vector on the rotating substrate holder.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment 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.
FIG. 1 is a schematic sectional explanatory view of one embodiment of the vapor phase thin film growth apparatus of the present invention. In FIG. 1, a reactor 10 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. That is, the upper inner diameter D₁ Is the lower inner diameter D₂ Smaller D₁ <D₂ It is. Each height H of the upper and lower parts dividing the reactor 10₁ And H₂ , That is, the division ratio is not particularly limited, and it is sufficient that a rotating substrate holder or the like is provided in the lower portion 2 in a predetermined manner. Usually H₁ / H₂ = 0.5 to 2.0. In the reactor 10, the upper end U of the large-diameter lower portion 2 and the lower end B of the small-diameter upper portion 1 are connected by a connecting portion 18, and the inner space of the reactor is continuous although the upper and lower portions have different diameters. In addition, the side wall surface of the upper portion 1 of the reactor is usually formed perpendicular to the side wall surface of the lower portion 2 and perpendicular to the upper surface of the rotating substrate holder. The connecting portion 18 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 of the vapor phase thin film growth apparatus according to the present invention, a plurality of rectifying gas outlet holes 18a for rectifying gas to flow out are formed in the connecting portion 18.
[0015]
In FIG. 1, a rotary substrate holder 12 on which a wafer substrate 11 is mounted is rotatably supported by a rotary shaft 13 and is disposed below the large-diameter reactor lower portion 2. A heater 14 for heating the wafer 12 and the wafer substrate 11 placed thereon is provided. The rotating substrate holder 12 is disposed such that the upper surface is located below the lower end B of the reactor with a predetermined height difference (H). 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 10. On the other hand, a plurality of reaction

gas supply ports

16, 16 are disposed on the top of the reactor upper part 1, and for example, silane (SiH₄ ), Dichlorosilane (SiH₂ Cl₂ ) And hydrogen (H₂ ), A reaction gas of a carrier gas such as helium (He) or argon (Ar) is supplied. The upper part of the upper part of the reaction furnace 1 holds a top part and a predetermined space area S, and a disk-shaped rectifying plate 17 having a plurality of holes 17a formed therein reacts so that the supply gas does not form an uneven flow path. It is arranged close to the inner peripheral surface of the furnace upper part.
[0016]
A rectifying gas flows out of the rectifying gas outlet 18a formed in the connecting portion 18 in order to smoothly flow the unreacted gas to the

exhaust ports

15, 15. As the rectifying gas, the above-mentioned carrier gas is generally used, and usually the same gas as the carrier gas supplied from the gas supply ports 16 at the top of the reactor is discharged. As a result, after the reactant gas reaches the wafer substrate 11 and is used for thin film growth, the unreacted gas flows smoothly from the outer peripheral side of the rotating substrate holder 12 without generating a gas swirl or a rough gas flow, and the exhaust port 15. 15 can be discharged. The introduction of the rectifying gas into the rectifying gas outlets 18a is not particularly limited as long as the rectifying gas flows out uniformly from the respective rectifying gas outlets 18a. For example, an introduction pipe can be provided for each rectification gas outlet 18a, and rectification gas can be separately introduced. As shown in FIG. 1, a rectifying gas introduction space 19 having a rectification gas supply port I is provided on the connecting portion 18 so as to hermetically surround the rectification gas outlet 18a. A rectifying gas may be supplied to 19. In this case, the upper part of the reactor 10 is formed in a double annular shape so as to surround the entire outer peripheral surface of the reactor upper part 1 like a rectifying gas introduction space part 19 ′ having a rectifying gas supply port I ′, May be used as the upper portion 1 of the reaction furnace, and the hollow annular portion may be used as a rectifying gas introduction space. This double ring shape is preferable because it is simple in the production of the reactor.
[0017]
In the vapor phase thin film growth apparatus of the present invention, as described above, the upper surface of the rotary substrate holder 12 has a predetermined height difference H below the lower end B of the upper portion 1 of the reactor. This height difference H is usually caused by a transition layer of the gas flow supplied to the upper part of the rotary substrate holder 12, that is, the gas flow such as the raw material gas supplied through the rectifying plate 17 as shown by an arrow in FIG. Is larger than the thickness (T) of the gas layer having a vector from the center to the outer peripheral portion on the rotating substrate holder 12. When the height difference H is smaller than the transition layer thickness T, the gas flow from the center of the wafer substrate 11 on the rotating substrate holder 12 to the outer peripheral portion is hindered by the lower end B of the reactor upper portion 1 and along the reactor inner wall. This is because a rising phenomenon occurs to promote the generation of a gas vortex, so that a large amount of precipitates are formed on the connecting portion 18 and the inner wall of the reactor lower part 2. Further, it is preferable that the upper surface of the rotating substrate holder 12 be in the same horizontal plane as the connecting portion 18 between the upper part 1 and the lower part 2 of the reactor.
[0018]
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 reactor, the pressure in the reactor, Although it changes depending on the number of rotations of the body, it can be calculated by the following equation (1). Equation (1) below is generally expressed in hydrodynamics.
T = 3.22 (ν / ω)^1/2                          (1)
(Where ν is the kinematic viscosity coefficient (mm²  / 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 thin film 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 of the wafer substrate is smooth, and no particles of the thin film forming material adhere to the inner wall of the furnace, and the obtained thin film forming wafer has no defect in the crystal phase and a uniform thin film is formed. You.
[0019]
Further, in the reactor having the upper and lower portions having different diameters in the vapor phase thin film growth apparatus of the present invention, the small diameter D₁  , Large diameter D of lower part 2₂  The diameter D of the rotating substrate holder 12_S  Are preferably in the following ratio relationships. For example, D₁  Is larger than the wafer diameter, and (1) D₂  / D₁  When the ratio is 1.2 or more (D₂  / D₁  ≧ 1.2). D₁  Is smaller than the wafer diameter, particles that have fallen from the inner wall surface of the furnace upper part 1 are likely 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, D₂  / D₁  If the ratio is smaller than 1.2, a gas upward flow phenomenon occurs along the reactor wall and a gas vortex occurs, and the diameter of the upper part of the reactor is reduced to prevent the gas upward phenomenon and reduce the gas vortex flow. This is because the effect of suppressing generation is reduced.
[0020]
(2) D₁  / D_S  When the ratio is 0.7 to 1.2 (0.7 ≦ D₁  / D_S  ≤ 1.2). D₁  / 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 D₁  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, D₁  / D_S  If the ratio is greater than 1.2, D₂  / D₁  This is because, like the case where the ratio is smaller than 1.2, there is an inconvenience that the gas flow rises upward along the inner wall of the reaction furnace and the gas vortex occurs. (3) D₂  / D_S  When the ratio is 1.2 or more (D₂  / D_S  ≧ 1.2). D₂  / D_S  If the ratio is less than 1.2, the roughness of the gas flow outside the rotating substrate holder 12 cannot be suppressed, so that particles adhere to the inner wall of the reaction furnace facing the outside of the rotating substrate holder 12 or unreacted gas is removed from the rotating substrate holder 12. This is because a thin film forming component is precipitated on the inner wall of the lower portion 2 of the reactor by reacting below the holding body 12.
[0021]
As described above, in the vapor phase thin film growth apparatus of the present invention, the reaction furnace is a continuous hollow cylindrical body having different diameters which are divided into upper and lower portions, and rectifying gas outflow holes are formed at upper and lower connecting portions having different diameters. It can be designed and manufactured in substantially the same manner as the above-mentioned conventional gas-phase thin-film growth apparatus having a hollow cylindrical body having the same diameter, except that the respective members are arranged in a predetermined manner. . A vapor phase growth method using the vapor phase thin film growth apparatus of the present invention can be similarly performed. In the vapor phase thin film growth apparatus of the present invention configured as described above, the inside of the reaction furnace 10 is evacuated by the exhaust control device connected to the

exhaust ports

15, 15, and the furnace pressure, for example, the source gas and the carrier gas The reaction gas is adjusted to 20 to 50 torr. On the other hand, the rotating substrate holder 12 is rotated by the rotation of the rotating shaft 13 by operating the motor, and the wafer substrate 11 thereon is simultaneously rotated. At the same time, the wafer substrate 11 on the rotating substrate holder 12 is For example, it is heated to about 900 to 1200 ° C. At the same time, a reaction gas composed of a source gas and a carrier gas is supplied into the reaction furnace 10 from the plurality of reaction gas supply ports 16 while controlling the flow rate to a predetermined value. The gas flow supplied to the space area S from the plurality of reaction

gas supply ports

16 and 16 has a uniform momentum and pressure distribution, and furthermore, a gas flow rate distribution in the reaction furnace by passing through the holes 17 a of the current plate 17. Is supplied onto the substrate so that the thin film can be uniformly vapor-phase grown on the substrate. In the vapor phase thin film growth apparatus of the present invention, the same gas as the normal carrier gas flows out as a rectifying gas from the rectifying gas outlet 18a of the connecting portion 18 simultaneously with the supply of the reaction gas.
[0022]
In this case, the reaction gas flow rate (G_C  ) And the flow velocity of the rectifying gas (G_I  ) Ratio (G_I  / G_C  ) Is 0.05 to 2 (0.05 ≦ G_I  / G_C  It is preferable to flow out so as to satisfy ≦ 2). G_I  / G_C  Is less than 0.05, it is not preferable because the gas flow becomes rough at a portion where the diameter of the lower portion of the reactor located outside the rotary substrate holder 12 is increased. G_I  / G_C  Exceeds 2, the gas flow velocity at the enlarged diameter portion on the outer side of the rotating substrate holder 12 becomes too fast, and a smooth gas flow from the center of the rotating substrate holder 12 to the outer periphery on the rotating substrate holder 12 is similarly increased. Therefore, it is not preferable because a uniform thin film having a uniform thickness cannot be grown. Ratio G to reaction gas from reaction gas supply port_I  / G_C  Flows out of the rectifying gas through the rectifying gas outlet hole 18a of the connecting portion 18 within the above range, so that the flow of the reaction gas on the rotating substrate holder and the flow of the reacting gas from the outer peripheral side of the rotating substrate holder to the inner space of the lower part of the reactor are not completed. The flow of the reaction gas is smoothly performed without causing a gas vortex or a rough gas flow. As a result, a uniform high-quality thin film-formed wafer substrate having few crystal defects can be obtained.
[0023]
The arrangement of the straightening gas outflow holes provided in the above-mentioned connecting portion is only required to prevent generation of a gas vortex due to upward rising of gas and generation of a rough gas flow in the enlarged diameter portion of the reactor, and the capacity of the reactor The reaction gas can be appropriately selected according to the reaction conditions such as the type of the reaction gas, the flow rate of the reaction gas, the rotation speed of the rotating substrate holder, and is not particularly limited. Normally, like the rectified gas flow indicated by the arrow in FIG. 1, outflow holes having the same diameter are uniformly arranged throughout the connecting portion 18 so that the gas outflow speed is evenly distributed. Further, in order to make the outflow velocity distribution of the rectifying gas have a gradient, the rectifying gas outflow holes may be arranged so that the hole diameters are changed in a predetermined distribution. For example, in the schematic diagram of another embodiment of the vapor phase thin film growth apparatus shown in FIG. 2, the flow of the rectifying gas from the rectifying gas outlet hole 28a of the connecting portion 28 is indicated by an arrow, as shown by the arrow. The flow can be discharged so as to have a gradient in the flow velocity distribution so that the flow velocity is high on the inner peripheral wall side of the lower portion of the reactor 2 and slow on the central side. In FIG. 2, the same members as those in the apparatus shown in FIG. 1 are given the same numerical value in the first place or are given the same reference numerals (the same applies hereinafter). In order to have a gradient in the rectifying gas flow in which the flow velocity decreases from the inner peripheral wall side toward the center as described above, for example, as shown in a schematic plan view of the connecting portion 28 in FIG. 28a can be arranged. In other words, a method is used in which a large number of outflow holes are provided on the inner peripheral wall side and a small number are provided on the center side. By flowing the rectifying gas in such a manner as to have a predetermined flow velocity gradient, it is possible to prevent the occurrence of gas vortex and rough gas flow, rectify the flow of the reaction gas, and smoothly flow the unreacted gas from the lower part of the reactor. It is effective for exhausting.
[0024]
In the present invention, the outflow direction of the rectifying gas is not particularly limited. Normally, as shown in FIGS. 1 and 2 above, the liquid is discharged perpendicular to the surface of the rotating substrate holder. However, it can also flow out in a direction other than the vertical direction as needed. In other words, by rectifying gas outflow holes in the connecting portion so as to have an angle instead of a vertical direction parallel to the rotation axis of the rotating substrate holder, the rectifying gas flows out of the rectifying gas outflow holes of the rotating substrate holder. It can be discharged at a predetermined angle with respect to the rotation axis. For example, FIG. 4 is an enlarged partial cross-sectional explanatory view of an example of the connecting portion region. In FIG. 4, the straightening gas outlet hole 48a of the connecting portion 48 is formed so as to be inclined at a predetermined angle toward the inner peripheral wall of the reaction furnace. The rectifying gas from the rectifying gas outlet hole 48a flows away from the rotation axis in the direction of the inner peripheral wall. Such a rectifying gas outlet hole structure is preferable because the gas flow near the rotating body is not roughened. In this case, the inclination angle is usually about 10 to 80 degrees with respect to the rotation axis of the rotating substrate holder, and is inclined toward the inner peripheral wall of the reactor. It is not preferable to incline in the direction of the rotation axis because the gas flow swept out from the vicinity of the rotating body is roughened.
[0025]
Further, the rectifying gas may be caused to flow out in accordance with the rotation direction of the rotating substrate holder. For example, FIG. 5 is a schematic perspective view in which an example of a connecting portion in which a straightening gas outflow hole 58a of the annular connecting portion 58 is inclined at a predetermined angle in the circumferential direction and is cut out is shown. In FIG. 5, a hole is formed so as to be inclined in the circumferential direction from a hole 58X of a rectifying gas outflow hole 58a on a gas inflow surface and communicate with a hole 58Y on a gas outflow surface on a back surface. The rectifying gas from the rectifying gas outlet hole 58a flows out in the same circumferential direction as the rotation of the rotating substrate holder. This straightening gas outlet hole structure is preferable because it does not roughen the gas flow near the rotating body. The inclination angle in this case is also generally inclined in the circumferential direction at about 10 to 80 degrees with respect to the gas inflow surface of the connection portion. Furthermore, the rectifying gas outflow hole can be inclined in the circumferential direction and at the same time in the center direction of the diameter, so that the rectifying gas can flow out in the rotating direction of the rotating substrate holder. FIG. 6 is a schematic plan view showing an example of a connecting portion in which the straightening gas outflow hole 68a of the annular connecting portion 68 is formed at a predetermined angle in the circumferential direction and the center of the annular shape. In FIG. 6, a hole is formed in the gas inflow surface 6F so as to be inclined from the opening 68X of the rectifying gas outflow hole 68a in the circumferential direction and the annular center direction so as to communicate with the opening 68Y of the gas outflow surface on the back surface. The rectifying gas flows out from the rectifying gas outlet hole 68a so as to rotate in the same direction as the rotation direction of the rotating substrate holder. This straightening gas outlet hole structure is preferable because it does not roughen the gas flow near the rotating body. In this case, the inclination angle is usually about 10 to 80 degrees with respect to the gas inflow surface of the connecting portion and about 10 to 80 degrees with respect to the circumferential direction.
[0026]
【Example】
Examples 1-3
As in the case of the reactor shown in FIG.₁  , Lower inner diameter D₂  And rotating substrate holder diameter D_S  Have the diameters shown in Table 1, respectively, and a vapor phase growth apparatus arranged so that the upper and lower ends B and the upper surface of the rotating substrate holder have the height difference H shown in Table 1 is used. SiH as source gas₄  Gas as carrier gas H₂  Gas and diborane (B₂  H₆  ) To H₂  The gas contained in the gas at 0.1 ppm was supplied at the flow rates shown in Table 1, and the same H as the carrier gas was supplied from the connection portion.₂  The gas flowed out uniformly in the vertical direction at a flow rate shown in Table 1 as a rectifying gas. The ratio (G) between the reaction gas flow rate (m / s) and the rectifying gas flow rate (m / s)_I  / G_c  ), The reaction temperature, the reaction pressure, and the number of rotations of the rotating substrate holder are also shown in Table 1.
[0027]
B on a silicon wafer under the vapor phase growth conditions shown in Table 1.₂  H₆  Vapor-phase growth of a dopant silicon thin film was performed. After the vapor-phase growth thin film was formed, the adhesion of particles to the connection part of the vapor-phase growth apparatus used and the inner peripheral wall of the lower part of the reactor were visually observed. The number of LPDs (wafer surface laser scatterers) having a diameter of 0.135 μm or more was measured using a Surfscan 6200 manufactured by Tencor Co., Ltd. for the properties of the crystal phase on the obtained thin film-formed wafer substrate surface. The results are shown in Table 1. 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. In addition, 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.
[0028]
[Table 1]

[0029]
Comparative Examples 1-2
Except that the rectifying gas flowed out of the connection part in a very small amount (Comparative Example 1) or a large amount (Comparative Example 2) as shown in Table 1, a vapor phase thin film growth constructed in the same manner as the reactor of Example 1 Using a device, B was placed on a silicon wafer in the same manner as in Example 1.₂ H₆ Vapor-phase growth of a dopant silicon thin film was performed. Thereafter, the results of observation in the apparatus and measurement of the obtained thin film-formed wafer substrate in the same manner are shown in Table 1.
[0030]
Comparative Examples 3 to 13
A silicon thin film was vapor-phase grown on a wafer substrate in the same manner as in Example 1 using a reaction furnace 70 of a vapor-phase thin-film growth apparatus whose schematic cross-sectional explanatory view was shown in FIG. In FIG. 7, a reaction furnace 70 is operated except that the upper diameter of the upper part 1 ′ of the small diameter and the inner diameter of the upper part of the lower part 2 ′ of the large diameter are different, and the connecting portion 78 connecting the upper and lower parts is not provided with a rectifying gas outlet. The structure is exactly the same as that of the reaction furnace of the vapor phase thin film growth apparatus of Example 1. Members similar to those of the apparatus shown in FIG. 1 are indicated by the same numeral of the first digit or by the same reference numeral. In the reactor 70, the inner diameter D₁ , Lower inner diameter D₂ And rotating substrate holder diameter D_S Was changed as shown in Tables 2 and 3, and B was formed on the silicon wafer in the same manner as in Example 1.₂ H₆ Vapor-phase growth of a dopant silicon thin film was performed. Thereafter, the results of the observation in the apparatus and the same measurement performed on the obtained thin film-formed wafer substrate are shown in Tables 2, 3 and 4.
[0031]
[Table 2]

[0032]
[Table 3]

[0033]
Comparative Examples 14 and 15
Using a reactor configured similarly to the reactor 80 of the conventional vapor phase thin film growth apparatus shown in FIG. Under the same vapor phase growth reaction conditions as in Example 1 shown in Table 4, B₂ H₆ A dopant silicon thin film was formed. After that, the results of observation in the apparatus and measurement of the obtained thin film-formed wafer substrate in the same manner are shown in Table 4.
[0034]
[Table 4]

[0035]
As is clear from the above Examples and Comparative Examples, the thin film-formed wafer substrate obtained by dividing the reaction furnace into upper and lower portions having different diameters and allowing the rectifying gas to flow out from the connection portion where the diameter of the upper and lower portions is enlarged in a predetermined manner. It can be seen that the number of LPDs of the crystal phase on the surface is reduced to about 1/300 or less as compared with Comparative Example 14 using the conventional vapor phase growth apparatus under the same conditions at 100 or less. Further, it is clear that a very uniform thin film is formed with a uniformity of the formed thin film of 1 or less. In addition, it can be seen that the uniformity of the resistance value is 4.4 or less, and there is no defect in the crystal phase, and also the re-incorporation of the dopant is prevented and a uniform thin film is formed. When a large amount of the carrier gas is circulated by the conventional apparatus as in Comparative Example 15, the film thickness is relatively uniform, the LPD is small and the crystal phase is relatively good, but the uniformity of the resistance value is low. Inferiorly, it can be estimated that the gas flow was rough on the outer peripheral side of the rotating substrate holder. Further, it can be predicted that the amount of precipitates is large at the lower part of the reactor and the maintenance cycle of the reactor is shortened.
[0036]
On the other hand, even in the case where the reactors having different diameters at the upper and lower portions are used as in Comparative Examples 3 to 13, even when the rectifying gas does not flow out from the connecting portion, the diameter ratio is the same as in the example. In Comparative Example 3 above, all of the film uniformity, the resistance value uniformity, the number of LPDs, and the amount of deposits in the lower part of the reaction furnace are more excellent than the case of the conventional normal carrier gas flow rate (Comparative Example 14). However, it is clear that the flow rate is lower than that of the example in which the rectifying gas is discharged. Further, it can be seen that even when the ratio between the diameter of the furnace upper and lower parts and the diameter of the rotating substrate holder is variously changed, good results cannot be obtained as compared with the embodiment. In Comparative Examples 8 and 9 in which the lower diameter was increased three to four times as compared with the upper diameter, a relatively good thin film was formed, but there were inconveniences such as an excessively large device size. This is not preferable because there is a precipitate in the part, defects in the crystal phase increase somewhat, and the maintenance cycle of the reactor is shortened. Further, in Comparative Example 12 in which the height difference between the upper lower end B of the reactor and the upper surface of the rotating substrate holder was close to 5 mm, the number of LPDs was significantly increased, and the crystal phase defects, the uniformity of the thin film thickness, and the resistance value were small. It can be seen that the uniformity of is significantly impaired.
[0037]
Further, according to Comparative Examples 1 and 2, when the flow rate of the rectifying gas from the connecting portion is smaller than the flow rate of the reaction gas, the flow rate can be obtained using the reactor of the vapor phase thin film growth apparatus of the present invention. While the thin film is relatively good, the number of LPDs increases remarkably at three times the flow rate of the reaction gas, and there is no precipitate at the connection part, but the amount of deposition at the lower part of the reactor increases, and the obtained thin film properties It can also be seen that also decreases.
Note that the transition layer thickness T in the above Examples and Comparative Examples is ω = 209 rad / s and ν = 6608 to 8811 mm according to the above equation (1).²  The calculated value at which / s was introduced was 18 to 21 mm.
[0038]
【The invention's effect】
The vapor-phase thin-film growth apparatus of the present invention is configured such that the reaction furnace is divided into upper and lower parts by a small-diameter upper part and a large-diameter lower part, and an upper lower end and a lower upper end are joined to form a continuous hollow internal space. The lack of the rising space can prevent the reaction gas from rising upward. In addition, temperature rise of the reaction gas can be suppressed, uniform nucleation of the source 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 addition, a gas outlet hole is provided at the connection part of the upper and lower joints, and a rectifying gas flows out simultaneously with the reaction gas, stabilizing the gas flow to the exhaust port at the lower part of the reactor, so that the wafer substrate is placed. In addition to preventing the generation of a gas vortex on the rotating substrate holder, the reaction gas flow becomes turbulent on the outer peripheral side and the gas flow can be prevented from becoming rough, and the connection part can prevent precipitates at the lower part of the reaction furnace. The maintenance cycle of the reactor can be maintained for a long time.
After all, the vapor phase thin film growth by the vapor phase thin film growth apparatus of the present invention keeps the gas flow in the reactor stable without generation of particles, turbulence and drift, and the particle flow to the furnace inner wall. It is possible to obtain a high-quality, uniform-thickness thin-film-formed wafer substrate having no crystal defects and no crystal defects without adhesion and preventing an increase in particles adhering to the wafer, and a wafer suitable for high integration can be obtained. .
[Brief description of the drawings]
FIG. 1 is a schematic sectional explanatory view of one embodiment of a vapor phase thin film growth apparatus of the present invention.
FIG. 2 is a schematic sectional view showing a gas flow of another embodiment of the vapor phase thin film growth apparatus of the present invention.
FIG. 3 is a schematic plan view of a connecting portion in the vapor phase thin film growth apparatus of FIG. 2;
FIG. 4 is a schematic cross-sectional view of a connection region in another embodiment of the vapor phase thin film growth apparatus of the present invention.
FIG. 5 is a partially cutaway perspective schematic view of a connecting portion in another embodiment of the vapor phase thin film growth apparatus of the present invention.
FIG. 6 is a schematic plan view of a connecting portion in another embodiment of the vapor phase thin film growth apparatus of the present invention.
FIG. 7 is a schematic sectional explanatory view of a vapor phase thin film growth apparatus used in a comparative example of the present invention.
FIG. 8 is a schematic sectional explanatory view of an example of a conventional vapor phase thin film growth apparatus.
[Explanation of symbols]
10, 20, 70, 80 reactor
11, 21, 41, 51, 71, 81 wafer substrate
12, 22, 42 52, 72, 82 Rotating substrate holder
13,23,43,73,83 Rotation axis
14, 24, 44 74, 84 heater
15, 25, 75, 85 Exhaust port
16, 26, 76, 86 Gas supply port
17, 27, 77, 87 Rectifier plate
17a, 27a, 77a, 87a Straightening hole
18, 28, 78 connecting part
18a, 28a, 78a Rectifying gas outlet
19, 19 ', 29 Rectifying gas introduction space
1, 1 'upper part of reactor
2, 2 'lower part of reactor
S space part
B Upper and lower end
U lower upper end
I, I 'Rectifying gas inlet
D₁    Reactor upper inside diameter
D₂    Reactor lower inside diameter
D_S    Rotating substrate holder diameter

Claims

It has a plurality of reaction gas supply ports at the top of a hollow reaction furnace, an exhaust port at the bottom, a rotating substrate holder for mounting a wafer substrate inside, and a rectifying plate with a plurality of holes formed at the top inside. In a vapor phase growth apparatus for supplying a reaction gas inside and vapor-phase growing a thin film on a wafer substrate surface on a rotating substrate holder,
The hollow interior of the reaction furnace is divided into upper and lower portions with different equivalent inner diameters, the equivalent inner diameter of the upper portion is smaller than the equivalent inner diameter of the lower portion, and the upper and lower lower ends and the lower upper end are connected by a connecting portion and the hollow interior is continuous. Having a rectifying gas outlet in the connection,
The straightening vane is disposed closely above the inner peripheral surface in the upper part of the reactor,
An apparatus for growing a vapor phase thin film, wherein the rotary substrate holder is disposed below a lower end of the upper portion of the reactor with a predetermined height difference.

2. The vapor phase thin film growth apparatus according to claim 1, further comprising: a space portion airtightly surrounding the rectification gas outlet hole on the connection portion, wherein the space portion has a rectification gas supply port.

3. The vapor phase thin film growth apparatus according to claim 1, wherein the upper side surface is perpendicular to the rotation holder upper surface.

4. The vapor phase thin film growth apparatus according to claim 3, wherein the space portion and the upper portion are formed in a double annular shape, and an outer surface of the space portion is continuous with the upper end of the lower portion via a connecting portion.

The horizontal cross section of the hollow interior of the reactor is circular, the upper diameter (D ₁ ) is larger than the diameter of the wafer substrate, and the rotating substrate holder is circular and has a diameter (D _S ). The vapor phase thin film growth apparatus according to any one of claims 1 to 4, wherein the ratio (D ₁ / D _S ) is 0.7 to 1.2.

The upper diameter (D ₁₎ and the lower diameter (D ₂₎ and the ratio (D ₂ / D ₁₎ is vapor thin film growth apparatus according to any one of claims 1 to 5 is 1.2 or more.

The lower diameter (D ₂₎ and the rotating substrate holder diameter (D _S) and the ratio (D ₂ / D _S) is vapor thin film growth apparatus according to any of claims 1 to 6 is 1.2 or more .

The height difference (H) between the upper and lower ends and the rotating substrate holder is the transition layer thickness (T) of the gas flow on the upper surface of the rotating substrate holder = 3.22 (ν / ω) ^1/2 (where ν 8 is larger than the kinematic viscosity coefficient (mm ² / s) of the atmosphere gas in the reactor, and ω is the angular velocity of rotation (rad / s). Growth equipment.

8. The gas phase growth apparatus according to any one of 1 to 7, wherein a transition layer thickness (T) of a gas flow above the rotating substrate holder (T) = 3.22 (ν / ω) ^1/2 (where ν is a reaction gas). the kinematic viscosity of (mm ² / s), ω displays the rotation of the angular velocity (rad / s) respectively), the height difference between the upper bottom and said rotary substrate holder upper surface (H) becomes smaller than such A plurality of reaction gas supply ports, a reaction gas comprising a thin film forming raw material gas and a carrier gas is supplied and passed through the holes of the current plate to the wafer substrate, and at the same time, the flow of the flow gas of the connection portion is reduced. A method for forming a vapor phase thin film, comprising introducing a rectifying gas through a hole.

Claim 9, wherein the ratio of the carrier gas flow rate (G _C) and rectifying the gas flow rate introduced from the rectifying gas outlet hole of the connecting portion _{_{(G I) (G I /}} G C) is 0.05 to 2 Vapor phase thin film growth method.