JP3546200B2

JP3546200B2 - Plasma CVD apparatus and plasma CVD method

Info

Publication number: JP3546200B2
Application number: JP2002003718A
Authority: JP
Inventors: 宏次佐竹
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 2002-01-10
Filing date: 2002-01-10
Publication date: 2004-07-21
Anticipated expiration: 2022-01-10
Also published as: JP2003203873A

Description

【０００１】
【発明の属する技術分野】
本発明は、薄膜電子デバイス、例えば、薄膜トランジスタ、太陽電池、電子写真感光体等の製造、開発プロセスに用いられるプラズマＣＶＤ装置及びプラズマＣＶＤ方法に関する。
【０００２】
【従来の技術】
プラズマを用いた薄膜形成及び材料加工プロセスは、薄膜電子デバイス及び新材料製造などに広く用いられている必要不可欠の技術である。これらのプロセスでは経済性の観点から、より高速なプロセスでかつ高品質なデバイスの製造方法が望まれている。
【０００３】
従来のプラズマＣＶＤ装置は、図１０に示すように、側壁の排気管２を介して真空ポンプ３により反応容器１の内部が排気されるようになっており、反応容器１内には矩形の電極４が設けられている。この電極４は接地され、その下面に基板１０を保持し、さらに基板１０を加熱するためのヒータ５を内蔵している。
【０００４】
高圧電極６は、接地電極４に対向配置され、かつ所望の距離の位置に固定され、高周波電源７から整合器８を介して高周波電力が供給されるようになっている。この高圧電極６の表面には複数のガス噴出孔９が開口し、両電極４，６間に均一にガスが吹き出すようになっている。
【０００５】
このようなプラズマＣＶＤ装置を用いて製膜する場合は、反応容器１内の接地電極４に基板１０を保持し、ヒータ５により所望の温度に加熱する。次に、反応性ガスを高圧電極６のガス噴出孔９から反応容器１内に供給する。同時に真空ポンプ３により反応容器１内のガスを排気管２を通して排気し、反応容器１内を所望のガス圧力に保持する。最後に、高周波電源７から整合器８を介して、高圧電極６に高周波電力を供給する。
【０００６】
この高周波電力の供給により電極４，６間に時間的に交番する電界が形成され、この電界により加速された電子が反応性ガス分子に衝突し、電離作用を引き起こすことで両電極４，６間にプラズマ１１が形成される。このプラズマ１１が反応性ガスを分解、活性な分子を生成し、加熱された基板１０の表面に活性分子が堆積することで目的の薄膜が形成される。このようなプラズマの生成方式は容量結合型と呼ばれ、接地電極４と高圧電極６とが電気的に強く結合したものになっている。
【０００７】
【発明が解決しようとする課題】
上記の従来装置においては、高圧電極６と接地電極４に保持された基板１０の間にプラズマ本体１１が生成されることになる。通常、プラズマはそれを囲む境界面に対し、正の電位(境界面の電位より高い電位)を維持する性質がある。このため、プラズマ１１中にある正の電荷を持ったイオンは、プラズマ１１から境界面に向かう電位勾配により加速され、基板１０上の成膜表面に高いエネルギーを持って入射することになる。このとき、膜中に侵入したイオンが十分大きいエネルギーを有していれば、薄膜を破壊するなどのダメージを与える場合がある。
【０００８】
また、プラズマ１１中で原料ガスが分解される領域は、電子温度が高く、電子密度の大きいプラズマシース端であることが多い。プラズマシースはプラズマ１１が触れる境界面近傍に形成されるもので、プラズマ１１に直接触れる基板１０の近傍にも形成される。従って、基板１０の近傍では、成膜において膜質に良い影響をもたらす活性分子のみならず、悪い影響をもたらす活性分子も生成される可能性がある。
【０００９】
例えば、シリコン薄膜を形成する場合、シラン系ガスをプラズマ１１で分解して基板上に膜を堆積させる際に、活性分子ＳｉＨ₃(シリル)は膜質に良い影響をもたらすが、その反面、ＳｉＨ₂(シリレン)はそのものが欠陥の多い膜の原因となる他、非常に反応性が高いので、連鎖的な反応により分子量の大きい高次の活性分子を生成し、それが欠陥の多い膜の原因になっているとも言われている。従って、従来装置のようにプラズマ１１本体が直接成膜を行う基板１０に接している場合は、膜質のコントロールが極めて困難となる。
【００１０】
さらに、高速に成膜を実施しようとする場合、例えば高周波電源７のパワーを増大することが行われる。この操作は、プラズマ１１中の電位をより一層高くし、電子温度も高くなるので前述の２つの弊害、すなわちイオンによるダメージと膜質を悪くする活性分子の影響を助長する可能性が高く、高速成膜時において膜質が極端に劣化するおそれがある。
【００１１】
本発明は上記課題を解決するためになされたものであり、薄膜へのイオンダメージを抑制し、かつ膜質に良い影響をもたらす活性分子と悪い影響をもたらす活性分子との選択性を向上させ、膜質の制御性を向上することができ、高速成膜時においても膜厚均一性に優れた薄膜を形成することができるプラズマＣＶＤ装置及びプラズマＣＶＤ方法を提供することを目的とする。
【００１２】
【課題を解決するための手段】
本発明者らは、特開２０００−７３１７４号公報において図１１に示すプラズマＣＶＤ装置及び薄膜電子デバイス製造方法（以下、先願発明という）を提案している。この先願発明の装置では、上述の高圧電極６の代わりに、高周波電力を供給する導体棒と接地された導体棒を交互に梯子状に並べた複数の導体棒からなる梯子型電極５１を設置する。この方法によれば高周波電力を供給する高圧格子電極５２(黒丸)と接地格子電極５３(白丸)との間でプラズマ１１を生成するために、基板１０を載せる接地電極４との電気的結合を弱めることができる。これによりプラズマ１１本体は基板１０から離れ、イオンによるダメージの抑制やプラズマ中の反応性を制御可能となる。本発明者らは、さらに鋭意研究した結果、以下の本発明を完成した。
【００１３】
本発明に係るプラズマＣＶＤ装置は、真空容器と、この真空容器内を排気する手段と、前記真空容器内で基板を保持するホルダと、このホルダ上の基板と向き合って配置された格子状の高圧電極と、この高圧電極に整合器を介して高周波電力を給電する高周波電源と、前記高圧電極に近接して並行な二段格子電極を構成するように前記ホルダ上の基板と前記高圧電極との間に配置され、前記高圧電極を構成する複数の格子電極棒に少なくとも１対１に対応するだけの複数の格子電極棒を有する格子状の接地電極と、反応性ガスを前記真空容器内に供給する第１のガス供給源と、前記反応性ガスを希釈する希釈ガスを前記真空容器内に供給する第２のガス供給源と、前記第２のガス供給源から前記真空容器内に希釈ガスを導入する希釈ガス導入口と、この希釈ガス導入口よりも前記ホルダ上の基板に近いところに開口し、反応性ガスを前記ホルダ上の基板に向けて供給する反応性ガス導入口と、前記高周波電源、前記第１のガス供給源および前記第２のガス供給源の動作をそれぞれ制御する手段と、を具備することを特徴とする。
【００１４】
本発明に係るプラズマＣＶＤ方法は、基板を真空容器内で保持するホルダと、このホルダ上の基板と向き合って配置された格子状の高圧電極と、この高圧電極に整合器を介して高周波電力を給電する高周波電源と、前記高圧電極に近接して並行な二段格子電極を構成するようにホルダ上の基板と前記高圧電極との間に配置され、前記高圧電極を構成する複数の格子電極棒に少なくとも１対１に対応するだけの複数の格子電極棒を有する格子状の接地電極と、反応性ガスを前記真空容器内に供給する第１のガス供給源と、反応性ガスを希釈する希釈ガスを前記真空容器内に供給する第２のガス供給源と、前記第２のガス供給源から前記真空容器内に希釈ガスを導入する希釈ガス導入口と、この希釈ガス導入口よりも前記ホルダ上の基板に近いところに開口し、反応性ガスを前記ホルダ上の基板に向けて供給する反応性ガス導入口とを具備するプラズマＣＶＤ装置を用いて、基板上に薄膜を製膜するプラズマＣＶＤ方法であって、
（ａ）基板をホルダで保持し、真空容器内を排気する工程と、
（ｂ）反応性ガスを前記接地電極のガス噴出孔から吹き出させてホルダ上の基板に向けて通流させるとともに、希釈ガスを前記接地電極後方のガス導入口から導入してホルダ上の基板に向けて通流させ、前記接地電極からホルダ上の基板までの空間で後方から流れる希釈ガスにより前方の反応性ガスを希釈する工程と、
（ｃ）高周波電源から高圧電極に高周波を印加して接地電極の格子電極棒の相互間に放電プラズマを生成させ、反応性ガス成分の活性種を作用させて基板上に製膜する工程と、を具備することを特徴とする．
本発明においては格子型高圧電極と格子型接地電極とを特定の相対位置関係に配置し、接地電極を構成する格子電極棒の相互間に局部的にプラズマをそれぞれ生成させることにより、イオンダメージが大幅に抑制され、膜質の制御性を向上させることができる。
【００１５】
さらに、高圧電極の径を接地電極の径よりも大きくすることにより、径の大きい高圧電極と径の小さい接地電極との最短距離を結ぶ間にプラズマを生成させること無しに、径の小さい接地電極の相互間のみにプラズマを容易に生成させることができる。
【００１６】
ＳｉＨ₄ガスを分解してシリコン薄膜を成膜する場合、活性分子ＳｉＨ₃(シリル)は膜質に良い影響をもたらすが、ＳｉＨ₂(シリレン)はそのものが欠陥の多い膜の原因となる他、非常に反応性が高いので、連鎖的な反応により分子量の大きい高次の活性分子を生成し、それが欠陥の多い膜の原因になっているとも言われている。
【００１７】
二段格子型電極に高周波を印可して放電プラズマを生成させると、図４に示すようにプラズマ１１の本体は接地格子電極６２の電極棒相互間であって高圧格子電極６１のほうに少し偏って生成される。
【００１８】
従って、ＳｉＨ₄ガスを接地格子電極６２の基板側表面から供給すれば、ＳｉＨ₄ガスはプラズマ１１本体中を完全に通過することを抑制できる。このようにすることで、プラズマ１１本体中に存在する高エネルギの電子によりＳｉＨ₄ガスが分解されることを抑制でき、膜質に悪い影響をもたらすＳｉＨ₂に生成を抑制可能となる。この理由は、ＳｉＨ₄ガスが分解してＳｉＨ₂になるのに必要なエネルギは９．４７ｅＶであり、これはＳｉＨ₃に必要とされるエネルギ８．７５ｅＶに比べて大きいからである。
【００１９】
一方、Ｈ₂ガスは、図５に示すようにプラズマ１１本体中を通過することで、効率的に水素原子に解離される。この解離した水素原子ＨとＳｉＨ₄ガスとの反応によりＳｉＨ₃を生成する反応速度は大きく、さらにＳｉＨ₂に対するＳｉＨ₃の選択比を向上することができ、良質な膜をつくることができる。
【００２０】
【発明の実施の形態】
以下、添付の図面を参照して本発明の種々の好ましい実施の形態について説明する。
【００２１】
図１に示すように、矩形状の反応容器１は、側壁に真空ポンプ３に連通する排気管２を有する。矩形の電極４は反応容器１内に設けられ、ヒータ５を内蔵している。電極４は、その下面に基板１０を吸着又はクランプ保持し、基板１０を所定温度域に加熱するものである。電極４は接地されている。
【００２２】
次に、図１中で該反応容器１内には本発明による二段格子型電極６１，６２を、電極４に対向し、かつ所望の距離の位置に設置する。このとき、径の大きい梯子型電極６１には高周波電源７から整合器８を介して高周波電力が供給される。一方、径の小さい格子型電極６２は接地されている。
【００２３】
図２に示すように、ガス供給電極６１，６２は、ガス溜りとしてのヘッダ６５を介して各ガス供給源２２，２３にそれぞれ連通している。ガス供給源２２，２３より供給されたガスは、ヘッダ６５に一時滞留することによりほぼ均等な圧力に調整され、複数のガス供給孔６３，６４から吹き出されるようになっている。
【００２４】
この二段格子型電極について図４を用いて詳述する。まず、径の大きい方の高圧電極６１と径の小さい接地電極６２の距離ｄ₁は、次の数値を目安に決められる。すなわち、高周波プラズマ中の電子の振幅Ａは次式で表される。
【００２５】
【数１】

【００２６】
但し、Ｅは電界強度、μは電子の移動度、ｍ_ｅは電子の質量、ｅは電子の電荷量、ω＝２πｆは高周波電力の角周波数をそれぞれ表す。
【００２７】
このとき、距離ｄ₁は振幅Ａの２倍よりも小さくする（ｄ₁＜２Ａ）。この理由は、上記の条件下ではプラズマ中の電子が容易に導体棒に到達することにより、結果的にプラズマの生成を抑制できるからである。これに併せて、径の小さい接地側電極６２の間隔ｄ₂をプラズマシース長の２〜３倍の程度とする。なお、プラズマシース長は高周波の周波数、ガス圧力、電力の大きさに依存して増減する。プラズマ解析の結果から、例えば周波数６０ＭＨｚ、ガス圧力３Torr、電力１０Ｗの場合に、プラズマシース長は約２ｍｍとなる。従って、間隔ｄ₂は４〜６ｍｍに設定される。
【００２８】
梯子型高圧電極６１の背後には、シャワープレート９１を備えた中空部があり、この中空部に反応性ガスを導入し、シャワープレート９１に設けた多数の噴出口９１ａから均一にガスが噴出するようにしてある。
【００２９】
（第１の実施形態）
次に、図１〜図６を参照して第１の実施形態について説明する。
【００３０】
図３は本発明の有効性を確認するためにコンピュータグラフィックスを用いてプラズマ生成中の装置内部における電子密度分布を調べた結果を示す数値シミュレーション図である。図４は図３の二段格子型電極の部分を拡大した図である。
【００３１】
上述の相対位置関係に格子型電極を二段に配置すると、径の大きい高圧電極６１と径の小さい接地電極６２の最短距離を結ぶ間にプラズマを生成すること無しに、図４に示すように、径の小さい接地電極６２の相互間のみにプラズマ１１を生成させることができる。
【００３２】
このような二段格子型電極とすることで、高圧電極６１と基板１０を保持する接地電極４との電気的結合は弱くなり、基板１０上の成膜面が直接プラズマ１１の本体に曝されることを避けることが可能となる。
【００３３】
また、格子型高圧電極６１と格子型接地電極６２との間にプラズマを挟み込むようにすると、プラズマ本体と基板１０との距離が大きくなってしまい、成膜速度が低下するとともに膜厚均一性も劣化するおそれがある。このような不都合が生じることを回避するために、径の小さい格子型接地電極６２の相互間にプラズマ１１を引き出すような配置としている。
【００３４】
次に、本実施形態のプラズマＣＶＤ装置を用いて基板の上にシリコン膜を製膜する場合について説明する。
【００３５】
反応容器１内の接地電極４に基板１０を保持し、ヒータ５により所望の温度に加熱する。梯子型高圧電極６１の背後には、シャワープレート９１を備えた中空部があり、この中空部に反応性ガスを導入し、該シャワープレート９１に設けた多数の噴出口から均一にガスが噴出するようにしてある。同時に真空ポンプ３により反応容器１内のガスを排気管２を通して排気し、反応容器１内を所望のガス圧力に保持する。最後に、高周波電源７から整合器８を介して、格子型高圧電極６１に高周波電力を供給する。この高周波電力の供給により格子型高圧電極６１と格子型接地電極６２との間に時間的に交番する電界が形成され、この電界により加速された電子が反応性ガス分子に衝突し、電離作用を引き起こすことでプラズマ１１が形成される。このプラズマ１１が反応性ガスを分解、活性な分子を生成し、活性分子が基板１０の表面に輸送され、加熱された基板１０の表面に活性分子が堆積することで目的の薄膜が形成される。
【００３６】
周波数６０ＭＨｚの高周波電力を二段梯子型電極６０のうち、径の大きい格子型電極６１に給電し、生成されたプラズマ中の電子密度の空間分布を示している。電子密度は径の小さい梯子型電極の間で最も大きく、上述の狙い通りのプラズマ生成が可能であることを示している。これらの図から明らかなように、格子型電極間のプラズマ本体から基板に向かうに従って、電子温度、電位ともに急激に減少することを確認した。従って、基板前面にプラズマシースによる急勾配の電位分布が形成されることがなく、イオンダメージは大幅に抑制される。また、格子型電極と基板間では電子密度、電子温度ともにかなり低下しているので、活性な分子の生成量は小さい。このため、例えば、シリコン薄膜の場合、良質な膜をもたらすＳｉＨ₃(シリル)のみを選択的に基板上に輸送することができる。
【００３７】
（第２の実施形態）
次に、第２の実施形態としてＳｉＨ₄及びＨ₂ガスを用いてシリコン系薄膜を成膜する場合について図５及び図６を参照して説明する。なお、本実施形態が上記の実施形態と重複する部分の説明は省略する。
【００３８】
図５は、Ｈ₂ガスを高圧格子電極６１背面からシャワープレート９１を通して供給し、ＳｉＨ₄ガスは接地格子電極６２中を通し、電極の基板側表面に複数のガス噴出口６３をあけて、そこから供給する方式である。
【００３９】
図６は、Ｈ₂ガスを高圧格子電極６２中を通し、電極の基盤側表面に複数のガス噴出孔６４を形成し、そこから供給し、ＳｉＨ₄ガスは図６と同様の方法で供給する方式である。
【００４０】
次に、本実施形態のプラズマＣＶＤ装置を用いて基板の上にシリコン膜を製膜する場合について説明する。
【００４１】
先に述べたように、ＳｉＨ₄ガスを分解してシリコン薄膜を成膜する場合、活性分子ＳｉＨ₃(シリル)は膜質に良い影響をもたらすが、ＳｉＨ₂(シリレン)はそのものが欠陥の多い膜の原因となる他、非常に反応性が高いので、連鎖的な反応により分子量の大きい高次の活性分子を生成し、それが欠陥の多い膜の原因になっているとも言われている。
【００４２】
本実施形態の二段格子型電極においては、プラズマ１１本体は接地格子電極６２の相互間のやや高圧格子電極６１Ａに偏った箇所に生成される。従って、ＳｉＨ₄ガスを接地格子電極６２の基板側表面から供給すれば、ＳｉＨ₄ガスはプラズマ１１本体中を完全に通過することを抑制できる。このようにすることによりプラズマ１１本体中に存在する高エネルギの電子によりＳｉＨ₄ガスが分解されることを抑制でき、膜質に悪い影響をもたらすＳｉＨ₂に生成を抑制可能となる。この理由は、ＳｉＨ₄ガスが分解してＳｉＨ₂になるのに必要なエネルギは９．４７ｅＶでＳｉＨ₃の必要なエネルギ８．７５ｅＶに比べて大きいからである。
【００４３】
一方、図６よりＨ₂ガスはプラズマ１１本体中を通過することで、効率的に水素原子に分解される。この水素原子ＨとＳｉＨ₄ガスとの反応によりＳｉＨ₃を生成する反応速度は大きく、さらにＳｉＨ₂に対するＳｉＨ₃の選択比を向上することができ、良質な膜を作ることができる。
【００４４】
（第３の実施形態）
次に、第３の実施形態としてＳｉＨ₄及びＨ₂ガスを用いてシリコン系薄膜を成膜する場合について図７及び図８を参照して説明する。なお、本実施形態が上記の実施形態と重複する部分の説明は省略する。
【００４５】
図７に示すように、プラズマＣＶＤ装置の基板側の電極４は整合器８１を介して高周波電源７１に接続されている。電源７１から電極４に高周波電力を供給すると、その周波数に応じて基板の表面電位が時間的に変動する。二段格子型電極６１，６２により生成されたプラズマ１１中のイオンはプラズマの空間電位と基板の表面電位との間で時間的に変動する電位差により加速され、基板表面に入射するようになっている。
【００４６】
図８の（ａ）は、横軸にイオンエネルギ（ｅＶ）をとり、電極４に給電する高周波電力の周波数を１３．５６ＭＨｚとしたときの基板に入射するＳｉＨ₃ ^＋とＨ^＋のイオンエネルギ分布を示す特性線図である。図８の（ｂ）は、横軸にイオンエネルギ（ｅＶ）をとり、電極４に給電する高周波電力の周波数を７０ＭＨｚとしたときの基板に入射するＳｉＨ₃ ^＋とＨ^＋のイオンエネルギ分布を示す特性線図である。各図中にて実線Ａ１，Ａ２はＳｉＨ₃ ^＋のエネルギ分布を示し、破線Ｂ１，Ｂ２はＨ^＋のエネルギ分布を示す。なお、各図の縦軸は規格化された度数を表わしたものであり、任意の単位（無単位）である。図８の（ａ）（ｂ）から明らかなように、低い周波数（１３．５６ＭＨｚ）ではエネルギ分布は広く、高い周波数（７０ＭＨｚ）ではエネルギ分布が狭くなる。このことから周波数を変えることにより入射エネルギを制御することができることが判明した。イオンエネルギが高すぎる場合、例えば結晶系シリコンを製膜する場合では約２０ｅＶを超える場合、膜中の結晶格子を破壊して膜質を劣化させる可能性が高いので、高周波電力によりイオンエネルギを制御することが可能となる。
【００４７】
（第４の実施形態）
次に、第４の実施形態としてＳｉＨ₄及びＨ₂ガスを用いてシリコン系薄膜を成膜する場合について図９を参照して説明する。なお、本実施形態が上記の実施形態と重複する部分の説明は省略する。
【００４８】
二段格子電極の径の小さいほうの電極６２に電圧可変の直流電源７２を接続している。
【００４９】
本実施形態によれば、格子電極６２に対してバイアス電圧を印加することにより、格子型電極６２の相互間に生成されるプラズマ１１の一部が基板１０側への拡散を制御することができる。通常、電極６２は接地してゼロ電位（０Ｖ）としているが、これを負の電位にバイアスすることで、プラズマ１１は隣り合う格子電極６２間に閉じ込められる効果が増大し、格子電極６２と基板１０との間には電子温度の低い低温プラズマが生成される。
【００５０】
このようにすることにより、格子電極６２と基板１０との間に存在するプラズマによるガス分解をさらに低電子エネルギでの反応を優位にすることができる。
【００５１】
シリコン系薄膜を製膜する場合を例にあげると、ＳｉＨ₄ガスが分解してＳｉＨ₃になるのに必要なエネルギは８．７５ｅＶであるのに対して、ＳｉＨ₂は９．４７ｅＶものエネルギが必要になるので、膜質を劣化させるＳｉＨ₂は生成を抑制し、ＳｉＨ₃を選択的に生成することができる。
【００５２】
従って、本実施例による格子型電極６２における直流電圧制御はプラズマ中の反応制御に有効である。
【００５３】
【発明の効果】
本発明によれば、２段格子電極によるプラズマ生成法の特長を活用し、反応性ガスの供給箇所を２箇所とすることで、プラズマＣＶＤ中の反応を制御可能とし、結果として膜質の向上に寄与できる。
【図面の簡単な説明】
【図１】本発明の実施形態に係るプラズマＣＶＤ装置を模式的に示すブロック断面図。
【図２】ガス管電極へのガス供給機構を示す図。
【図３】コンピュータグラフィックスを用いてプラズマ生成中の装置内部における電子密度分布を調べた結果を示す数値シミュレーション図。
【図４】図５の二段格子型電極の部分を拡大した図。
【図５】二段格子型電極の周辺領域におけるガスの流れを模式的に示す図。
【図６】他の二段格子型電極の周辺領域におけるガスの流れを模式的に示す図。
【図７】本発明の他の実施形態に係るプラズマＣＶＤ装置を模式的に示すブロック断面図。
【図８】（ａ）は周波数１３．５６ＭＨｚの高周波を用いて生成されるプラズマから基板に入射するＳｉＨ₃イオンおよびＨイオンのエネルギ分布図、（ｂ）は周波数７０ＭＨｚの高周波を用いて生成されるプラズマから基板に入射するＳｉＨ₃イオンおよびＨイオンのエネルギ分布図。
【図９】本発明の他の実施形態に係るプラズマＣＶＤ装置を模式的に示すブロック断面図。
【図１０】従来の装置を模式的に示すブロック断面図。
【図１１】先願発明の装置を模式的に示すブロック断面図。
【符号の説明】
１…反応容器、
２…排気管、
３…真空ポンプ、
４…上部電極（基板側電極）、
５…ヒータ、
６…下部電極（格子電極）、
７…高周波電源、
８…整合器、
９…ガス噴出孔、
１０…基板、
１１…プラズマ
２１…制御器、
２２…第１のガス供給源（Ｈ₂）、
２３…第２のガス供給源（ＳｉＨ₄）、
５１…梯子型電極、
５２…高圧格子電極、
５３…接地格子電極、
６０，６０Ａ…二段格子型電極、
６１…高圧電極（丸棒）、
６１Ａ…高圧電極（ガス管）、
６２…接地電極（ガス管）、
６３，６４…ガス噴出孔、
６８…電子密度等高線、
７１…高周波電源、
７２…直流電源、
８１…整合器、
９１…シャワープレート、
９１ａ…ガス噴出口。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plasma CVD apparatus and a plasma CVD method used for manufacturing and developing processes of a thin film electronic device, for example, a thin film transistor, a solar cell, an electrophotographic photosensitive member, and the like.
[0002]
[Prior art]
2. Description of the Related Art Thin film formation and material processing processes using plasma are indispensable technologies widely used in thin film electronic devices and new material production. In these processes, from the viewpoint of economy, there is a demand for a higher-speed process and a method for manufacturing high-quality devices.
[0003]
In a conventional plasma CVD apparatus, as shown in FIG. 10, the inside of a reaction vessel 1 is evacuated by a vacuum pump 3 through an exhaust pipe 2 on a side wall. 4 are provided. The electrode 4 is grounded, holds the substrate 10 on its lower surface, and has a built-in heater 5 for heating the substrate 10.
[0004]
The high-voltage electrode 6 is arranged opposite to the ground electrode 4 and is fixed at a position at a desired distance, so that high-frequency power is supplied from a high-frequency power source 7 via a matching unit 8. A plurality of gas ejection holes 9 are formed on the surface of the high-voltage electrode 6 so that gas can be uniformly ejected between the electrodes 4 and 6.
[0005]
When a film is formed using such a plasma CVD apparatus, the substrate 10 is held on the ground electrode 4 in the reaction vessel 1 and heated to a desired temperature by the heater 5. Next, a reactive gas is supplied into the reaction vessel 1 from the gas ejection holes 9 of the high-pressure electrode 6. At the same time, the gas in the reaction vessel 1 is exhausted through the exhaust pipe 2 by the vacuum pump 3 to maintain the inside of the reaction vessel 1 at a desired gas pressure. Finally, high-frequency power is supplied from the high-frequency power supply 7 to the high-voltage electrode 6 via the matching unit 8.
[0006]
The supply of the high-frequency power forms an electric field that alternates in time between the electrodes 4 and 6, and the electrons accelerated by the electric field collide with the reactive gas molecules to cause ionization, thereby causing an ionization between the electrodes 4 and 6. The plasma 11 is formed at the time. The plasma 11 decomposes the reactive gas to generate active molecules, and the active molecules are deposited on the heated surface of the substrate 10 to form a target thin film. Such a plasma generation method is called a capacitive coupling type, in which the ground electrode 4 and the high voltage electrode 6 are electrically strongly coupled.
[0007]
[Problems to be solved by the invention]
In the above-described conventional apparatus, the plasma main body 11 is generated between the high voltage electrode 6 and the substrate 10 held by the ground electrode 4. Generally, plasma has a property of maintaining a positive potential (potential higher than the potential of the boundary surface) with respect to the boundary surface surrounding the plasma. Therefore, positively charged ions in the plasma 11 are accelerated by a potential gradient from the plasma 11 toward the boundary surface, and enter the film formation surface on the substrate 10 with high energy. At this time, if the ions that have penetrated into the film have a sufficiently large energy, damage such as breaking the thin film may be caused.
[0008]
In addition, the region where the source gas is decomposed in the plasma 11 is often a plasma sheath end having a high electron temperature and a high electron density. The plasma sheath is formed near the boundary surface where the plasma 11 touches, and is also formed near the substrate 10 which directly touches the plasma 11. Therefore, in the vicinity of the substrate 10, not only active molecules having a good effect on film quality in film formation but also active molecules having a bad effect may be generated.
[0009]
For example, when a silicon thin film is formed, when the silane-based gas is decomposed by the plasma 11 and a film is deposited on the substrate, the active molecule SiH ₃ (silyl) has a good effect on the film quality, but on the other hand, SiH ₂ Since (silylene) itself causes a film with many defects, it is also very reactive, so it generates high-order active molecules with a large molecular weight by a chain reaction, which causes a film with many defects. It is also said that it has become. Therefore, when the main body of the plasma 11 is in direct contact with the substrate 10 on which the film is directly formed as in the conventional apparatus, it is extremely difficult to control the film quality.
[0010]
Further, when film formation is to be performed at a high speed, for example, the power of the high frequency power supply 7 is increased. In this operation, the potential in the plasma 11 is further increased, and the electron temperature is also increased. Therefore, there is a high possibility that the above-mentioned two harmful effects, that is, damage by ions and the influence of active molecules that deteriorate the film quality, will be promoted. During film formation, the film quality may be extremely deteriorated.
[0011]
The present invention has been made in order to solve the above-mentioned problems, and suppresses ion damage to a thin film, and improves the selectivity between active molecules having a good effect on the film quality and active molecules having a bad effect on the film quality. It is an object of the present invention to provide a plasma CVD apparatus and a plasma CVD method which can improve the controllability of a thin film and can form a thin film having excellent film thickness uniformity even during high-speed film formation.
[0012]
[Means for Solving the Problems]
The present inventors have proposed a plasma CVD apparatus and a method for manufacturing a thin film electronic device (hereinafter, referred to as a prior application) shown in FIG. 11 in JP-A-2000-73174. In the device of the prior application, a ladder-type electrode 51 composed of a plurality of conductor rods in which conductor rods for supplying high-frequency power and grounded conductor rods are alternately arranged in a ladder shape is provided instead of the high-voltage electrode 6 described above. . According to this method, in order to generate the plasma 11 between the high-voltage grid electrode 52 (black circle) supplying the high-frequency power and the ground grid electrode 53 (white circle), the electrical connection with the ground electrode 4 on which the substrate 10 is mounted is established. Can be weakened. As a result, the main body of the plasma 11 is separated from the substrate 10, so that the damage due to ions can be suppressed and the reactivity in the plasma can be controlled. The present inventors have further studied diligently, and as a result, have completed the present invention described below.
[0013]
A plasma CVD apparatus according to the present invention includes a vacuum container, a unit for evacuating the inside of the vacuum container, a holder for holding a substrate in the vacuum container, and a grid-like high-pressure arranged facing the substrate on the holder. An electrode, a high-frequency power supply for supplying high-frequency power to the high-voltage electrode through a matching device, and a substrate and the high-voltage electrode on the holder so as to form a parallel two-stage lattice electrode close to the high-voltage electrode. A grid-like ground electrode having a plurality of grid electrode rods corresponding to at least one-to-one correspondence with the plurality of grid electrode rods constituting the high-voltage electrode; and supplying a reactive gas into the vacuum vessel. A first gas supply source, a second gas supply source for supplying a diluent gas for diluting the reactive gas into the vacuum vessel, and a diluent gas from the second gas supply source into the vacuum vessel. Dilution gas introduction A reactive gas inlet opening closer to the substrate on the holder than the dilution gas inlet and supplying a reactive gas toward the substrate on the holder; and the high-frequency power source, the first Means for controlling operations of the gas supply source and the second gas supply source, respectively.
[0014]
The plasma CVD method according to the present invention includes a holder for holding a substrate in a vacuum container, a grid-like high-voltage electrode arranged facing the substrate on the holder, and a high-frequency power supplied to the high-voltage electrode through a matching device. A high-frequency power supply for supplying power, and a plurality of grid electrode rods arranged between the substrate on the holder and the high-voltage electrode so as to form a parallel two-stage grid electrode close to the high-voltage electrode and forming the high-voltage electrode A grid-like ground electrode having a plurality of grid electrode rods corresponding to at least one to one, a first gas supply source for supplying a reactive gas into the vacuum vessel, and a dilution for diluting the reactive gas A second gas supply source for supplying a gas into the vacuum container, a dilution gas inlet for introducing a dilution gas from the second gas supply source into the vacuum container, and a holder which is more than the dilution gas introduction port. Close to the upper board Open to the filtrate, a reactive gas using a plasma CVD apparatus comprising a reactive gas introduction port for supplying toward the substrate on the holder, a plasma CVD method for film formation of the thin film on a substrate,
(A) holding the substrate with a holder and evacuating the vacuum vessel;
(B) a reactive gas is blown out from a gas ejection hole of the ground electrode to flow toward the substrate on the holder, and a diluting gas is introduced from a gas inlet behind the ground electrode to the substrate on the holder. Diluting the front reactive gas with a diluent gas flowing from the rear in the space from the ground electrode to the substrate on the holder,
(C) applying a high frequency from a high frequency power source to the high voltage electrode to generate discharge plasma between the grid electrode rods of the ground electrode, and act on the active species of the reactive gas component to form a film on the substrate; It is characterized by having.
In the present invention, the grid-type high-voltage electrode and the grid-type ground electrode are arranged in a specific relative positional relationship, and plasma is locally generated between grid electrode rods constituting the ground electrode, thereby reducing ion damage. It is greatly suppressed, and the controllability of the film quality can be improved.
[0015]
Further, by making the diameter of the high-voltage electrode larger than the diameter of the ground electrode, the plasma is not generated while connecting the shortest distance between the large-diameter high-voltage electrode and the small-diameter ground electrode. Can be easily generated only between the two.
[0016]
When SiH ₄ gas is decomposed to form a silicon thin film, the active molecule SiH ₃ (silyl) has a good effect on the film quality, but SiH ₂ (silylene) itself causes a film with many defects and is very poor. It is also said that due to its high reactivity, high-order active molecules having a large molecular weight are produced by a chain reaction, which causes a film having many defects.
[0017]
When a high frequency is applied to the two-stage grid electrode to generate discharge plasma, the main body of the plasma 11 is slightly biased toward the high voltage grid electrode 61 between the electrode bars of the ground grid electrode 62 as shown in FIG. Generated.
[0018]
Therefore, if supplying the SiH ₄ gas from the substrate side surface of the ground grid electrode 62, SiH ₄ gas may prevent the passing completely through the plasma 11 in the body. By doing so, the decomposition of the SiH ₄ gas by the high-energy electrons present in the plasma 11 main body can be suppressed, and the generation of SiH ₂ that adversely affects the film quality can be suppressed. The reason for this is that the energy required for SiH ₄ gas to decompose into SiH ₂ is 9.47 eV, which is larger than the energy required for SiH ₃ , 8.75 eV.
[0019]
On the other hand, the H ₂ gas is efficiently dissociated into hydrogen atoms by passing through the plasma 11 main body as shown in FIG. The reaction rate of producing SiH ₃ by the reaction between the dissociated hydrogen atoms H and the SiH ₄ gas is high, the selectivity of SiH _{3 to} SiH ₂ can be improved, and a good quality film can be formed.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, various preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[0021]
As shown in FIG. 1, the rectangular reaction vessel 1 has an exhaust pipe 2 communicating with a vacuum pump 3 on a side wall. The rectangular electrode 4 is provided in the reaction vessel 1 and has a built-in heater 5. The electrode 4 holds or clamps the substrate 10 on its lower surface, and heats the substrate 10 to a predetermined temperature range. The electrode 4 is grounded.
[0022]
Next, in FIG. 1, two-stage

lattice type electrodes

61 and 62 according to the present invention are installed in the reaction vessel 1 at a desired distance from the electrode 4. At this time, high-frequency power is supplied from the high-frequency power source 7 to the ladder-shaped electrode 61 having a large diameter via the matching unit 8. On the other hand, the small-diameter grid electrode 62 is grounded.
[0023]
As shown in FIG. 2, the

gas supply electrodes

61 and 62 communicate with the respective

gas supply sources

22 and 23 via a header 65 serving as a gas reservoir. The gas supplied from the

gas supply sources

22 and 23 is temporarily stored in the header 65 to be adjusted to a substantially uniform pressure, and is blown out from the plurality of gas supply holes 63 and 64.
[0024]
The two-stage grid electrode will be described in detail with reference to FIG. First, the distance d ₁ between the large-diameter high-voltage electrode 61 and the small-diameter ground electrode 62 is determined based on the following numerical values. That is, the amplitude A of the electrons in the high-frequency plasma is represented by the following equation.
[0025]
(Equation 1)

[0026]
However, E is represented respectively field strength, mu is the electron mobility, m _e is the electron mass, e is the electron charge quantity, omega = 2 [pi] f is the angular frequency of the high frequency power.
[0027]
At this time, the distance d ₁ is smaller than twice the amplitude A (d ₁ <2A). The reason for this is that under the above conditions, the electrons in the plasma easily reach the conductor bar, and as a result, generation of the plasma can be suppressed. Along with this, the distance d ₂ of the small ground-side electrode 62 of diameter 2 to 3 times the extent of the plasma sheath length. The plasma sheath length increases and decreases depending on the frequency of the high frequency, the gas pressure, and the magnitude of the electric power. From the result of the plasma analysis, for example, when the frequency is 60 MHz, the gas pressure is 3 Torr, and the power is 10 W, the plasma sheath length is about 2 mm. Therefore, distance d ₂ is set to 4 to 6 mm.
[0028]
Behind the ladder-type high-voltage electrode 61, there is a hollow portion provided with a shower plate 91. A reactive gas is introduced into this hollow portion, and the gas is uniformly discharged from a large number of outlets 91a provided in the shower plate 91. It is like that.
[0029]
(1st Embodiment)
Next, a first embodiment will be described with reference to FIGS.
[0030]
FIG. 3 is a numerical simulation diagram showing the result of examining the electron density distribution inside the apparatus during plasma generation using computer graphics to confirm the effectiveness of the present invention. FIG. 4 is an enlarged view of a portion of the two-stage grid electrode of FIG.
[0031]
When the grid type electrodes are arranged in two stages in the above-described relative positional relationship, as shown in FIG. 4 without generating plasma while connecting the shortest distance between the large-diameter high-voltage electrode 61 and the small-diameter ground electrode 62, The plasma 11 can be generated only between the small-diameter ground electrodes 62.
[0032]
With such a two-stage grid electrode, the electrical coupling between the high-voltage electrode 61 and the ground electrode 4 holding the substrate 10 is weakened, and the film formation surface on the substrate 10 is directly exposed to the main body of the plasma 11. Can be avoided.
[0033]
Further, if the plasma is sandwiched between the grid-type high-voltage electrode 61 and the grid-type ground electrode 62, the distance between the plasma body and the substrate 10 becomes large, so that the film-forming speed is reduced and the film thickness uniformity is improved. There is a risk of deterioration. In order to avoid such inconvenience, the arrangement is such that the plasma 11 is extracted between the grid-type ground electrodes 62 having a small diameter.
[0034]
Next, a case in which a silicon film is formed on a substrate using the plasma CVD apparatus of the present embodiment will be described.
[0035]
The substrate 10 is held on the ground electrode 4 in the reaction vessel 1 and heated to a desired temperature by the heater 5. Behind the ladder-type high-voltage electrode 61, there is a hollow portion provided with a shower plate 91. A reactive gas is introduced into this hollow portion, and the gas is jetted out uniformly from a large number of outlets provided in the shower plate 91. It is like that. At the same time, the gas in the reaction vessel 1 is exhausted through the exhaust pipe 2 by the vacuum pump 3 to maintain the inside of the reaction vessel 1 at a desired gas pressure. Finally, high-frequency power is supplied from the high-frequency power supply 7 to the lattice-type high-voltage electrode 61 via the matching unit 8. By the supply of the high-frequency power, an electric field that alternates in time is formed between the grid-type high-voltage electrode 61 and the grid-type ground electrode 62, and the electrons accelerated by the electric field collide with the reactive gas molecules, thereby causing ionization. This causes the plasma 11 to be formed. The plasma 11 decomposes the reactive gas to generate active molecules, the active molecules are transported to the surface of the substrate 10, and the active molecules are deposited on the heated surface of the substrate 10 to form a target thin film. .
[0036]
A high-frequency power having a frequency of 60 MHz is supplied to a large-diameter lattice electrode 61 of the two-stage ladder electrode 60, and the spatial distribution of the electron density in the generated plasma is shown. The electron density is highest between the ladder-shaped electrodes having a small diameter, indicating that the above-described target plasma can be generated. As is clear from these figures, it was confirmed that both the electron temperature and the potential sharply decreased from the plasma body between the lattice electrodes toward the substrate. Therefore, no steep potential distribution due to the plasma sheath is formed on the front surface of the substrate, and ion damage is greatly suppressed. In addition, since both the electron density and the electron temperature are considerably reduced between the grid electrode and the substrate, the amount of active molecules generated is small. Therefore, for example, in the case of a silicon thin film, only SiH ₃ (silyl) which provides a high quality film can be selectively transported onto the substrate.
[0037]
(Second embodiment)
Next, as a second embodiment, a case in which a silicon-based thin film is formed using SiH ₄ and H ₂ gases will be described with reference to FIGS. Note that the description of the portions of this embodiment that overlap with the above-described embodiments will be omitted.
[0038]
FIG. 5 shows that the H ₂ gas is supplied from the back of the high-pressure grid electrode 61 through the shower plate 91, the SiH ₄ gas passes through the ground grid electrode 62, and a plurality of gas ejection ports 63 are opened on the substrate side surface of the electrode. It is a method of supplying from.
[0039]
FIG. 6 shows that H ₂ gas is passed through the high-pressure grid electrode 62, and a plurality of gas ejection holes 64 are formed on the base-side surface of the electrode and supplied from there. SiH ₄ gas is supplied in the same manner as in FIG. It is a method.
[0040]
Next, a case in which a silicon film is formed on a substrate using the plasma CVD apparatus of the present embodiment will be described.
[0041]
As described above, when decomposing SiH ₄ gas to form a silicon thin film, the active molecule SiH ₃ (silyl) has a good effect on the film quality, but SiH ₂ (silylene) itself is a film having many defects. It is also said that, because of its extremely high reactivity, a chain reaction produces higher-order active molecules having a large molecular weight, which causes a film with many defects.
[0042]
In the two-stage grid electrode of the present embodiment, the plasma 11 main body is generated between the ground grid electrodes 62 at a position slightly biased to the high-voltage grid electrode 61A. Therefore, if supplying the SiH ₄ gas from the substrate side surface of the ground grid electrode 62, SiH ₄ gas may prevent the passing completely through the plasma 11 in the body. By doing so, the decomposition of the SiH ₄ gas by high-energy electrons existing in the main body of the plasma 11 can be suppressed, and the generation of SiH ₂ that adversely affects the film quality can be suppressed. The reason for this is that the energy required to decompose the SiH ₄ gas into SiH ₂ is 9.47 eV, which is larger than the required energy of SiH ₃ of 8.75 eV.
[0043]
On the other hand, from FIG. 6, the H ₂ gas is efficiently decomposed into hydrogen atoms by passing through the plasma 11 main body. The reaction rate of generating SiH ₃ by the reaction between the hydrogen atom H and the SiH ₄ gas is high, the selectivity of SiH _{3 to} SiH ₂ can be improved, and a high quality film can be formed.
[0044]
(Third embodiment)
Next, a case where a silicon-based thin film is formed using SiH ₄ and H ₂ gases as a third embodiment will be described with reference to FIGS. Note that the description of the portions of this embodiment that overlap with the above-described embodiments will be omitted.
[0045]
As shown in FIG. 7, the electrode 4 on the substrate side of the plasma CVD apparatus is connected to a high frequency power supply 71 via a matching device 81. When high-frequency power is supplied from the power supply 71 to the electrode 4, the surface potential of the substrate fluctuates with time according to the frequency. The ions in the plasma 11 generated by the two-stage

lattice type electrodes

61 and 62 are accelerated by a potential difference that fluctuates with time between the space potential of the plasma and the surface potential of the substrate, and enter the substrate surface. I have.
[0046]
FIG. 8A shows the ion energy (eV) on the horizontal axis, and the ion energy distribution of SiH ₃ ⁺ and H ⁺ incident on the substrate when the frequency of the high-frequency power supplied to the electrode 4 is 13.56 MHz. FIG. FIG. 8B shows the ion energy (eV) on the horizontal axis, and shows the ion energy distribution of SiH ₃ ⁺ and H ⁺ incident on the substrate when the frequency of the high-frequency power supplied to the electrode 4 is 70 MHz. FIG. 3 is a characteristic diagram. In each figure, solid lines A1 and A2 show the energy distribution of SiH ₃ ⁺ , and broken lines B1 and B2 show the energy distribution of H ⁺ . Note that the vertical axis in each figure represents the normalized frequency, and is an arbitrary unit (no unit). As is clear from FIGS. 8A and 8B, the energy distribution is wide at low frequencies (13.56 MHz) and narrow at high frequencies (70 MHz). This proved that incident energy could be controlled by changing the frequency. If the ion energy is too high, for example, when forming a crystalline silicon film, if it exceeds about 20 eV, there is a high possibility that the crystal lattice in the film is destroyed and the film quality is deteriorated. It becomes possible.
[0047]
(Fourth embodiment)
Next, a case of forming a silicon-based thin film using SiH ₄ and H ₂ gas as a _fourth embodiment will be described with reference to FIG. Note that the description of the portions of this embodiment that overlap with the above-described embodiments will be omitted.
[0048]
A variable voltage DC power supply 72 is connected to the electrode 62 having the smaller diameter of the two-stage lattice electrode.
[0049]
According to the present embodiment, by applying a bias voltage to the grid electrode 62, it is possible to control the diffusion of a part of the plasma 11 generated between the grid electrodes 62 to the substrate 10 side. . Normally, the electrode 62 is grounded to have a zero potential (0 V). By biasing the electrode 62 to a negative potential, the effect of confining the plasma 11 between the adjacent grid electrodes 62 increases, and the grid electrode 62 and the substrate A low-temperature plasma having a low electron temperature is generated between them.
[0050]
By doing so, gas decomposition due to plasma existing between the grid electrode 62 and the substrate 10 can further favor the reaction with lower electron energy.
[0051]
Taking the case of forming a silicon-based thin film as an example, the energy required to decompose SiH ₄ gas into SiH ₃ is 8.75 eV, whereas the energy required for SiH ₂ is 9.47 eV. Since it becomes necessary, the generation of SiH ₂ that degrades the film quality can be suppressed, and SiH ₃ can be selectively generated.
[0052]
Therefore, the DC voltage control in the grid electrode 62 according to the present embodiment is effective for controlling the reaction in the plasma.
[0053]
【The invention's effect】
According to the present invention, the reaction during plasma CVD can be controlled by utilizing the features of the plasma generation method using the two-stage lattice electrode and providing two reactive gas supply points, thereby improving the film quality. Can contribute.
[Brief description of the drawings]
FIG. 1 is a block sectional view schematically showing a plasma CVD apparatus according to an embodiment of the present invention.
FIG. 2 is a view showing a gas supply mechanism to a gas tube electrode.
FIG. 3 is a numerical simulation diagram showing the result of examining the electron density distribution inside the apparatus during plasma generation using computer graphics.
FIG. 4 is an enlarged view of a part of a two-stage grid electrode of FIG. 5;
FIG. 5 is a diagram schematically showing a gas flow in a peripheral region of a two-stage grid electrode.
FIG. 6 is a diagram schematically showing a gas flow in a peripheral region of another two-stage lattice type electrode.
FIG. 7 is a block sectional view schematically showing a plasma CVD apparatus according to another embodiment of the present invention.
8A is an energy distribution diagram of SiH ₃ ions and H ions incident on a substrate from plasma generated using a high frequency of 13.56 MHz, and FIG. 8B is generated using a high frequency of 70 MHz. FIG. 4 is an energy distribution diagram of SiH ₃ ions and H ions incident on the substrate from the plasma.
FIG. 9 is a block sectional view schematically showing a plasma CVD apparatus according to another embodiment of the present invention.
FIG. 10 is a block sectional view schematically showing a conventional device.
FIG. 11 is a block sectional view schematically showing an apparatus of the invention of the prior application.
[Explanation of symbols]
1 ... reaction vessel,
2 ... exhaust pipe,
3 ... vacuum pump,
4: Upper electrode (substrate side electrode)
5 ... heater,
6. Lower electrode (lattice electrode)
7. High frequency power supply
8. Matching device,
9 ... gas vent,
10 ... substrate,
11 Plasma 21 Controller
22 first gas supply source (H ₂ )
23 ... second gas supply source (SiH ₄ )
51 ... Ladder type electrode,
52 high-voltage grid electrode
53 ... Ground grid electrode,
60, 60A: two-stage grid electrode,
61 ... High voltage electrode (round bar)
61A: High pressure electrode (gas pipe),
62: ground electrode (gas pipe),
63, 64 ... gas vent,
68: electron density contour,
71 ... High frequency power supply,
72 ... DC power supply,
81: Matching device,
91 ... shower plate,
91a: Gas outlet.

Claims

A vacuum vessel,
Means for evacuating the vacuum vessel;
A holder for holding a substrate in the vacuum vessel,
A grid-like high-voltage electrode arranged facing the substrate on the holder;
A high-frequency power supply for supplying high-frequency power to the high-voltage electrode via a matching device;
At least one-to-one is disposed between the substrate on the holder and the high-voltage electrode so as to form a parallel two-stage grid electrode close to the high-voltage electrode, and a plurality of grid electrode rods forming the high-voltage electrode. A grid-like ground electrode having a plurality of grid electrode rods only corresponding to
A first gas supply for supplying a reactive gas into the vacuum vessel;
A second gas supply source for supplying a diluent gas for diluting the reactive gas into the vacuum vessel;
A dilution gas inlet for introducing a dilution gas from the second gas supply source into the vacuum vessel;
A reactive gas inlet that opens closer to the substrate on the holder than the dilution gas inlet, and supplies a reactive gas toward the substrate on the holder;
Means for controlling operation of the high-frequency power supply, the first gas supply source and the second gas supply source, respectively;
A plasma CVD apparatus comprising:

The reactive gas inlet is provided in at least two places of the substrate-side front surface of the ground electrode and the rear surface behind the high-voltage electrode, or the substrate-side front surface of the ground electrode and the substrate-side front surface of the high-voltage electrode. The apparatus of claim 1, wherein:

The ground electrode has an internal flow path communicating with a first gas supply source, and is located closer to a substrate on the holder than an inlet of a diluent gas from the second gas supply source into a vacuum vessel. And a plurality of gas ejection holes serving as the reactive gas inlet for blowing the reactive gas flowing through the internal passage toward the substrate on the holder. The described device.

The diluent gas inlet is open at a plurality of locations on the back side of the high-pressure electrode, and the diluent gas passes through the high-pressure electrode, wraps around from the back side of the ground electrode, and reacts with the reactive gas blown out from the gas ejection hole. 2. The apparatus of claim 1, wherein the apparatus merges with the substrate toward the substrate.

The high-pressure electrode has an internal flow passage through which the diluent gas flows in communication with the second gas supply source, and the internal flow passage opens at a plurality of locations on the outer periphery of the high-pressure electrode. The dilution gas introduction port is formed, and the dilution gas wraps around from the back side of the ground electrode, merges with the reactive gas introduced from the reactive gas introduction port, and heads toward the substrate on the holder. The apparatus according to claim 1, wherein

2. The apparatus according to claim 1, wherein an outer diameter of the grid electrode rod forming the ground electrode is smaller than an outer diameter of the grid electrode rod forming the high voltage electrode.

The control unit controls a frequency of a high frequency power supplied from the high frequency power supply to the high voltage electrode, thereby temporally fluctuating a potential difference between a space potential in plasma and a surface potential of the substrate to be incident on the substrate. The apparatus of claim 1, wherein the apparatus controls ion energy.

The method of claim 1, further comprising a DC power supply for biasing the ground electrode.

A holder for holding the substrate in the vacuum vessel, a grid-like high-voltage electrode disposed opposite to the substrate on the holder, a high-frequency power supply for supplying high-frequency power to the high-voltage electrode via a matching device, and the high-voltage electrode The high-voltage electrode is disposed between the substrate on the holder and the high-voltage electrode so as to form a parallel two-stage grid electrode in close proximity to the plurality of grid electrode rods constituting the high-voltage electrode. A plurality of grid electrode rods, a grid-like ground electrode, a first gas supply source for supplying a reactive gas into the vacuum vessel, and a diluent gas for diluting the reactive gas into the vacuum vessel A second gas supply source, a dilution gas inlet for introducing a dilution gas from the second gas supply source into the vacuum vessel, and an opening that is closer to the substrate on the holder than the dilution gas introduction port. The reactive gas Using a plasma CVD apparatus comprising a reactive gas introduction port for supplying toward the substrate above, a plasma CVD method for film formation of the thin film on a substrate,
(A) holding the substrate with a holder and evacuating the vacuum vessel;
(B) a reactive gas is blown out from a gas ejection hole of the ground electrode to flow toward the substrate on the holder, and a diluting gas is introduced from a gas inlet behind the ground electrode to the substrate on the holder. Diluting the front reactive gas with the diluent gas flowing from the rear in the space from the ground electrode to the substrate on the holder,
(C) a step of applying a high frequency from a high-frequency power source to the high-voltage electrode to generate discharge plasma between the grid electrode rods of the ground electrode, and act on the active species of the reactive gas component to form a film on the substrate;
A plasma CVD method comprising:

In the step (b), a reactive gas is supplied from at least two of the substrate-side front surface of the ground electrode and the rear surface behind the high-voltage electrode, or the substrate-side front surface of the ground electrode and the substrate-side front surface of the high-voltage electrode. 10. The method of claim 9, wherein:

In the step (c), the potential difference between the space potential in the plasma and the surface potential of the substrate is temporally fluctuated by controlling the frequency of a high frequency power supplied from the high frequency power supply to the high voltage electrode. The method according to claim 9, wherein the incident ion energy is controlled.

The method according to claim 9, wherein in the step (c), a bias is further applied to the ground electrode by a DC power supply.