JP3635463B2

JP3635463B2 - Self-bias measurement method and apparatus, and electrostatic chuck

Info

Publication number: JP3635463B2
Application number: JP2001361202A
Authority: JP
Inventors: 弘明佐伯
Original assignee: Tokyo Electron Ltd
Current assignee: Tokyo Electron Ltd
Priority date: 2001-11-27
Filing date: 2001-11-27
Publication date: 2005-04-06
Anticipated expiration: 2020-04-06
Also published as: JP2002252276A

Description

【０００１】
【産業上の利用分野】
本発明は、プラズマ処理装置において被処理体の自己バイアス電圧を測定する自己バイアス測定方法および装置ならびに被処理体を載置台上に静電吸着力で保持する静電吸着装置に関する。
【０００２】
【従来の技術】
たとえば、半導体集積回路の製造においては、アッシング、エッチング、ＣＶＤ、スパッタリング等の諸工程で、処理ガスのイオン化や化学反応等を促進するために、プラズマが利用されている。一般のプラズマ処理装置は、真空の処理容器内に一対の電極を上下に対向配置して、上部電極をアース電位に接続し、下部電極（載置台）に高周波電圧を印加することで、両電極間に放電によるプラズマを発生させ、このプラズマ中の電子、イオン等を載置台上の被処理体たとえば半導体ウエハに電界の力で引っ張り込んで、半導体ウエハの表面に所定のプラズマ処理を施すようにしている。
【０００３】
このようなプラズマ処理装置では、高周波電圧がコンデンサを介して下部電極（載置台）に印加されることから、載置台上の被処理体は直流的に負の電位いわゆる自己バイアス電圧にクランプされる。つまり、高周波電圧が正電圧となる半周期ではプラズマ中の電子（負の電荷）が被処理体側に引き寄せられ、高周波電圧が負電圧となる半周期ではプラズマ中のイオン（正の電荷）が被処理体側に引き寄せられるが、電子のほうがイオンよりも質量が小さくて移動しやすいため、より多く引き寄せられ、その結果、定常的にコンデンサが充電され、被処理体は直流的にほぼ一定の負電位（自己バイアス電圧）にクランプされる。
【０００４】
自己バイアス電圧によって被処理体に入射するイオンのエネルギが左右され、これが大きすぎると被処理体表面の酸化膜が損傷する等の不具合が生じる。このことから、プラズマ処理装置においては、自己バイアス電圧を測定して所望の値に調整する必要がある。しかし、処理容器内の被処理体にプローブ等を当てて直接自己バイアス電圧を測定することは事実上不可能である。そこで、従来は、下部電極（載置台）の電位を電圧センス線等を介して測定し、その測定値から自己バイアス電圧を推定していた。
【０００５】
ところで、最近のプラズマ処理装置は、クランプ等の機械的な保持手段を使わずに静電気の吸着力で被処理体を載置台上に保持するようにした静電チャックを設けている。この種の静電チャックの初期のものは、たとえばアルミニウムからなる載置台の表面を酸化して絶縁被膜を形成してなり、載置台に高圧の直流電圧を印加して載置台表面の絶縁被膜を分極させることにより、被処理体との境面に静電気を発生させ、その静電吸着力（クーロン力）によって被処理体を載置台上に保持する機構であった。しかし、このような静電チャック機構は、載置台表面の絶縁被膜に十分な分極が得られず、静電吸着力が物足りなかった。今日では、絶縁フィルムの中に導電膜（静電吸着用電極）を封入してなる静電チャックシートを載置台の上面に被せる構造の静電チャックが主流となっている。
【０００６】
【発明が解決しようとする課題】
上記したように、従来の自己バイアス測定法は、下部電極（載置台）の電位を測定し、その測定値から自己バイアス電圧を推定する方法であった。しかし、下部電極と被処理体との間には静電チャックシートまたは絶縁被膜が介在し、その分の抵抗ないしキャパシタが作用するため、下部電極の電位と被処理体の電位（自己バイアス電圧）との近似性はよくない。このために、従来の方法は、測定誤差が多く、精度の高い自己バイアス電圧測定値が得られなかった。
【０００７】
また、従来は、静電吸着用電極に印加する直流電圧の値を自己バイアス電圧とは無関係に決めていた。このため、所要の静電吸着力を得るための直流印加電圧の設定または調整に手間がかかるだけでなく、いったん調整した後も処理条件の変化（たとえばプラズマ生成用の高周波電力の変化）によって自己バイアス電圧が変わると静電吸着力も変わってしまい、具合が悪かった。
【０００８】
本発明は、かかる問題点に鑑みてなされたもので、プラズマ処理装置において被処理体の自己バイアス電圧を短時間で正確に測定することができる自己バイアス測定方法および装置を提供することを目的とする。
【０００９】
また、本発明は、プラズマ処理装置において被処理体を所望の静電吸着力で保持することができるとともに自己バイアス電圧の変動に対して静電吸着力を設定値に安定に維持することができる静電吸着装置を提供することを目的とする。
【００１０】
【課題を解決するための手段】
上記の目的を達成するために、本発明の第１の自己バイアス測定方法は、プラズマ処理装置の処理容器内で載置台上に静電吸着力で保持される被処理体の自己バイアス電圧を測定する自己バイアス測定方法において、前記載置台の静電吸着用電極に可変の直流電圧を印加し、前記直流電圧の値を変えながら前記被処理体と前記静電吸着用電極との間の直流漏れ電流を検出し、前記直流電圧の電圧値と前記直流漏れ電流の電流値との間の電圧電流特性に基づいて前記自己バイアス電圧の測定値を求める方法とした。
【００１１】
また、本発明の第１の自己バイアス測定装置は、プラズマ処理装置の処理容器内で載置台上に静電吸着力で保持される被処理体の自己バイアス電圧を測定する自己バイアス測定装置において、前記載置台の静電吸着用電極に可変直流電圧を印加する可変直流電圧発生手段と、前記被処理体と前記静電吸着用電極との間の直流漏れ電流を検出する漏れ電流検出手段と、前記可変直流電圧発生手段より前記載置台の静電吸着用電極に印加される前記直流電圧を可変制御し、前記直流電圧の電圧値と前記漏れ電流検出手段によって検出される前記直流漏れ電流の電流値との間の電圧電流特性に基づいて前記自己バイアス電圧の測定値を求める自己バイアス電圧検出手段とを具備する構成とした。
【００１２】
本発明の第２の自己バイアス測定方法は、プラズマ処理装置の処理容器内で載置台上に静電吸着力で保持される被処理体の自己バイアス電圧を測定する自己バイアス測定方法において、前記載置台の静電吸着用電極に可変の直流電圧を印加し、前記直流電圧の値を変えながら前記被処理体と前記静電吸着用電極との間の直流漏れ電流を検出し、前記直流漏れ電流がほぼ零となるときの前記直流電圧の値を前記自己バイアス電圧の測定値とする方法とした。
【００１３】
また、本発明の第２の自己バイアス測定装置は、プラズマ処理装置の処理容器内で載置台上に静電吸着力で保持される被処理体の自己バイアス電圧を測定する自己バイアス測定装置において、前記載置台の静電吸着用電極に可変の直流電圧を印加する可変直流電圧発生手段と、前記被処理体と前記静電吸着用電極との間の直流漏れ電流を検出する漏れ電流検出手段と、前記可変直流電圧発生手段より前記載置台の静電吸着用電極に印加される前記直流電圧を可変制御し、前記漏れ電流検出手段より得られる前記直流漏れ電流の電流検出値がほぼ零となるときの前記直流電圧を前記自己バイアス電圧の測定値とする自己バイアス電圧検出手段とを具備する構成とした。
【００１４】
本発明の静電吸着装置は、プラズマ処理装置の処理容器内で被処理体を静電吸着力で載置台上に保持するための静電吸着装置において、前記被処理体に前記静電吸着力を及ぼすように前記載置台に設けられた静電吸着用電極と、前記静電吸着用電極に可変直流電圧を印加する可変直流電圧発生手段と、前記被処理体と前記静電吸着用電極との間の直流漏れ電流を検出する漏れ電流検出手段と、前記可変直流電圧発生手段より前記静電吸着用電極に印加される可変直流電圧の電圧値と前記漏れ電流検出手段によって検出される前記直流漏れ電流の電流値との間の電圧電流特性に基づいて前記自己バイアス電圧の測定値を求める自己バイアス電圧検出手段と、前記自己バイアス電圧検出手段より得られた前記自己バイアス電圧の測定値と所望の静電吸着力を得るための前記被処理体および前記電極間の電圧差との和または差の値にほぼ等しい電圧を前記被処理体の処理時に前記静電吸着用電極に印加するように前記可変直流電圧発生手段を制御する電圧制御手段とを具備する構成とした。
【００１５】
本発明の第１の自己バイアス測定方法または自己バイアス測定装置では、載置台の静電吸着用電極に可変の直流電圧を印加し、その可変直流電圧の値を変えながら被処理体と静電吸着用電極との間に流れる直流の漏れ電流を検出し、可変直流電圧と直流漏れ電流の電圧電流特性に基づいて自己バイアス電圧の測定値を求める。一般に、この電圧電流特性は自己バイアス電圧の値を中心とする対称な曲線として表される。このことから、本発明の第２の自己バイアス測定方法または自己バイアス測定装置では、直流漏れ電流がほぼ零となるときの可変直流電圧の値を自己バイアス電圧の測定値とする。
【００１６】
本発明の静電吸着装置では、本発明による自己バイアス測定方法で得られた自己バイアス電圧の測定値に基づいて、被処理体と静電吸着用電極間の電圧差が所望の静電吸着力を得るための電圧差となるように、静電吸着用電極に所定の可変直流電圧を印加する。電圧制御手段によって静電吸着力の制御・調整を行うので、自己バイアス電圧が変わっても自動的に可変直流電圧を調整して静電吸着力を設定値に安定に維持することができる。
【００１７】
【発明の実施の形態】
以下、添付図を参照して本発明の実施形態を説明する。
【００１８】
図１は、本発明の一実施形態におけるプラズマエッチング装置の構成を示す断面図である。
【００１９】
このプラズマエッチング装置の処理容器１０は、たとえばアルミニウムからなる両端の閉塞した円筒状のチャンバとして構成されている。処理容器１０の側壁には、被処理体たとえば半導体ウエハＷを容器１０内に搬入・搬出するためのゲートバルブ１１が設けられている。
【００２０】
処理容器１０の底面には円筒状でかつ導電性の外支持枠１２が立設され、この外支持枠１２の内側に有底円筒状でかつ絶縁性の内支持枠１４が嵌め込まれている。内支持枠１４の内側底部には円柱形の支持台１６が配設され、この支持台１６の上に円盤状の載置台１８がボルト（図示せず）によって固定されている。支持台１６および載置台１８のいずれもアルミニウム等の導電性金属からなる。支持台１６の内部には冷却ジャケット２０が設けられており、導入管２２を通って冷却ジャケット２０に供給された冷却液は排出管２４を通って装置外部へ排出されるようになっている。支持台１６および載置台１８には、熱交換用のガスたとえばヘリウムガスを載置台１８上の半導体ウエハＷの裏面に供給するための貫通孔１６ａ，１８ａが形成されている。下部電極として機能する載置台１８には、コンデンサ２６を介して高周波電源２８が接続されている。
【００２１】
載置台１８の上面には円形の静電チャックシート３０が冠着され、この静電チャックシート３０の上に半導体ウエハＷが載置される。静電チャックシート３０は、抵抗体としての機能をも併せ持つ誘電体たとえばＳｉＣからなる薄膜３２を上に、たとえばポリイミドからなる絶縁膜３４を下にして両者を重ね合わせ、その中に静電吸着用電極としてたとえば銅箔からなる薄い導電膜３６を封入してなるものである。この静電チャックシート３０においても、熱交換用のヘリウムガスを載置台１８上の半導体ウエハＷの裏面に供給するための通気孔３０ａが形成されている。
【００２２】
静電チャックシート３０の導電膜３６は、載置台１８を貫通する絶縁被覆導電線３８、支持台１６、内支持枠１４および外支持枠１２を貫通する給電棒４０、処理容器１０の外に設けられたコイル４２ならびに電流計４４を介して可変直流電源４６の出力端子に接続されている。
【００２３】
コイル４２は、コンデンサ４８と協働して、この直流回路に誘導または混入した高周波ノイズを除去するためのローパスフィルタを構成する。電流計４４は、この直流回路を流れる電流、つまり半導体ウエハＷ（被処理体）と静電チャックシート３０の導電膜３６（静電吸着用電極）との間の漏れ電流を検出し、その電流検出値を表す漏れ電流検出信号ＭＬを制御部５０に出力する。可変直流電源４６は、制御部５０からの電圧制御信号ＥＳで指定された任意の直流電圧Ｖ0 を出力できるように構成されている。制御部５０は、たとえばマイクロコンピュータからなり、後述するように本実施形態における自己バイアス電圧測定の制御および静電吸着力の制御・調整を行う。
【００２４】
載置台１８の上方には、ガス導入室５２が配設されている。ガス供給管５４を介してこのガス導入室５２に導入されたエッチングガスは、載置台１８と対向する多孔板５２ａの多数の通気孔５２ｂより均一な圧力・流量で半導体ウエハＷに向けて吐出または噴射される。ガス導入室５２は、上部電極を兼ねており、接地されている。処理容器１０の底付近の側壁には排気口５６が設けられており、この排気口５６に排気管５８を介して真空ポンプ（図示せず）が接続されている。
【００２５】
かかる構成のプラズマエッチング装置においては、次のようにしてプラズマエッチング加工が行われる。下部電極（載置台）１８に高周波電源２８よりコンデンサ２６を介してたとえば３８０ＫＨｚ、１５ＫＷの高周波電圧が印加され、かつ処理容器１０内が排気口５４および排気管５６を介して真空ポンプにより所定の真空度まで排気された状態の下で、ガス供給管５４およびガス導入室５２を通ってエッチングガスが処理容器１０内に供給される。そうすると、ガス導入室５２の直下で、エッチングガスのガス分子が高周波電力のエネルギにより電離し、プラズマが発生する。このプラズマ中の電子、イオン、活性種等が載置台１８上の半導体ウエハＷの表面（被処理面）にほぼ垂直に入射してウエハ表面の被加工物と化学反応を起こすことによって、エッチングが行われる。エッチングによって気化した反応生成物は排気口５６より排気される。
【００２６】
このようなエッチングが行われる間、静電チャックシート３０の導電膜３６には可変直流電源４６より一定の直流電圧が印加され、その直流電圧によって誘電体膜３２が分極して、導電膜３６の上面に正電荷、半導体ウエハＷの裏面に負電荷がそれぞれ誘導され、それら正電荷および負電荷間のクーロン力により半導体ウエハＷが載置台１８上に吸着保持される。
【００２７】
また、下部電極としての載置台１８にはコンデンサ２６を介して高周波電源２８より高周波電圧が印加され、かつ半導体ウエハＷの直上にはプラズマが立ち篭もっているため、半導体ウエハＷには自己バイアス電圧が誘起される。本実施例によれば、以下に説明するように、この自己バイアス電圧が正確に測定され、その自己バイアス電圧測定値に基づいてプラズマエッチング中に半導体ウエハＷを載置台１８上に所望の静電吸着力で保持するための直流電圧が可変直流電源４６より静電チャックシート３０の導電膜３６に印加されるようになっている。
【００２８】
図２および図４につき本実施形態における自己バイアス測定方法について説明する。図２は、本実施形態における自己バイアスの測定に関係する部分の回路図である。静電チャックシート３０の誘電体膜３２は、導電体と絶縁体の中間の抵抗率（１×１０^８〜１×１０^１２Ω・ｃｍ）を有するＳｉＣからなるので、これを抵抗体とみることができる。この抵抗体３２の抵抗値は相当大きいので、可変直流電源４６から導電膜３６までの導体（４２，４０，３８等）の抵抗値は無視することができる。また、上部電極５２と半導体ウエハＷとの間は、プラズマＰＲ中のイオン、電子が移動するので、導電性の空間である。
【００２９】
したがって、図２に示すように、可変直流電源４６の出力端子とアースとの間に、電流計４４、抵抗体（誘電体膜）３２、半導体ウエハＷ、プラズマＰＲおよび上部電極５２が直列接続された電気回路が形成される。定常状態でプラズマＰＲ内の電圧分布（電位）は一定で安定しており、半導体ウエハＷの電位は上部電極５２（アース電位）に対して自己バイアス電圧ＶSBにクランプされる。したがって、可変直流電源４６の出力電圧をＶ0 、抵抗体３２の抵抗値をＲとし、電流計４４における電圧降下を無視できるものとすると、この電気回路に流れる直流電流、つまり半導体ウエハＷと導電膜（静電吸着用電極）３６間の漏れ電流ｉL は次式で表される。
ｉL ＝（Ｖ0 −ＶSB）／Ｒ ……（１）
【００３０】
上式（１）において、自己バイアス電圧ＶSBは一定であるが、抵抗体３２の抵抗値Ｒは電圧Ｖ0 ，温度，半導体ウエハＷの裏面の状態たとえば酸化状態等によって変わる値である。
【００３１】
本実施形態では、制御部５０の制御の下で可変直流電源４６の出力電圧Ｖ0 の値を変えながら電流計４４で漏れ電流ｉL を検出する。そうすると、Ｖ0 とｉL の絶対値｜ｉL ｜との間には、図３に示すような電圧電流特性が得られる。この電圧電流特性においては、Ｖ0 がＶSB（自己バイアス電圧）にほぼ等しいときに｜ｉL ｜はほぼ零になり、Ｖ0 とＶSBの差（絶対値）が大きくなるにしたがって｜ｉL ｜は放物線状に増大する。Ｖ0 がＶSBよりも大きいときｉL は導電膜（静電吸着用電極）３６側から半導体ウエハＷ側に流れ、Ｖ0 がＶSBよりも小さいときｉL は反対に半導体ウエハＷ側から導電膜３６側に流れる。かかる電圧電流特性を基に自己バイアス電圧の測定値を求めることができる。
【００３２】
本実施形態の好適な自己バイアス測定法によれば、Ｖ0 がＶSBにほぼ等しいときに｜ｉL ｜がほぼ零になるという上記電圧電流特性に基づいて、｜ｉL ｜がほぼ零になったときのＶ0 の値が自己バイアス電圧ＶSBの測定値とされる。制御部５０は、電流計４４より｜ｉL ｜がほぼ零の値であることを示す漏れ電流検出値ＭＬを受け取った時の可変直流電源４６の出力電圧Ｖ0 の値を自己バイアス電圧ＶSBの測定値と判定する。制御部５０は、こうして求めた自己バイアス電圧ＶSBの測定値を表示装置や記録装置（図示せず）に与えて表示または記録させることも可能である。
【００３３】
また、第２の自己バイアス測定法によれば、自己バイアス電圧ＶSBの値を中心点としてＶ0 とＶSBの差が大きくなるにしたがって｜ｉL ｜は放物線状に増大するという上記電圧電流特性に基づいて、極性が逆で絶対値の等しい漏れ電流ｉL の電流値ｉLa，ｉLbが得られるときのＶ0 の値Ｖ0a，Ｖ0bの中間値（Ｖ0a＋Ｖ0b）／２が自己バイアス電圧ＶSBの測定値とされる。この場合、制御部２０は、Ｖ0 の各値に対するｉL の測定値を記憶部（図示せず）に取り込み、比較演算により極性が逆で絶対値の等しい測定値ｉLa，ｉLbを割り出し、ひいてはそれらの測定値にそれぞれ対応するＶ0 の値Ｖ0a，Ｖ0bを割り出し、それらの電圧値Ｖ0a，Ｖ0bから自己バイアス電圧ＶSBの測定値を演算で求める。
【００３４】
本実施形態において、制御部５０は開ループで可変直流電源４６の出力電圧Ｖ0 を制御するが、必要に応じてＶ0 を検出する電圧検出手段を設けてもよく、その場合はより高い精度でＶ0 の値を監視ないし制御することができ、ひいてはより高い精度で自己バイアス電圧ＶSBの測定値を得ることができる。
【００３５】
なお、本実施形態の自己バイアス測定法においては、Ｖ0 をＶSBに近づけると、半導体ウエハＷと導電膜（静電吸着用電極）３６間の印加電圧（電圧差）が小さくなり、静電吸着力が小さくなる。半導体ウエハＷの裏面には熱交換用のガスが供給されるため、静電吸着力が小さくなると、熱交換用のガスの圧力で半導体ウエハＷが載置台１８からずれ落ちるおそれもある。したがって、図１のプラズマエッチング装置においてこの自己バイアス測定法を実施するときは、たとえばダミーの半導体ウエハＷを用いて、これを適当な治具で保持する等の工夫が必要である。その点、上記第２の自己バイアス測定法においては、Ｖ0 をＶSBに近づけずに極性が逆で絶対値の等しい測定値ｉLa，ｉLbを割り出すことが可能であるから、実際にエッチング加工を受ける半導体ウエハＷに対して自己バイアス電圧ＶSBを測定することができる。
【００３６】
本実施形態における静電吸着装置は、静電チャックシート３０、可変直流電源４６、電流計４４、制御部５０から構成される。制御部５０は、上記したような可変直流電源４６の出力電圧Ｖ0 と電流計４４によって検出される漏れ電流ｉL との間の電圧電流特性に基づいて半導体ウエハＷの自己バイアス電圧ＶSBの測定値を求める自己バイアス電圧検出手段として機能するだけでなく、次のようにエッチング加工時に半導体ウエハＷを載置台１８上に所望の静電吸着力で保持するための直流電圧を導電膜（静電吸着用電極）３６に与えるように可変直流電源４６を制御する電圧制御手段としても機能する。
【００３７】
すなわち、半導体ウエハＷと導電膜（静電吸着用電極）３６間の印加電圧ＶF と静電吸着力Ｆとの間には図４に示すような比例関係があり、この関係（特性）は理論値または実験値として得られる。制御部５０は、所要の静電吸着力Ｆs が設定されたならば、このＦs に対応した印加電圧ＶF の値ＶFSに上記自己バイアス電圧ＶSBの測定値を加え、その加算値（ＶFS＋ＶSB）に等しい出力電圧Ｖ0 を可変直流電源４６に出力させる。
【００３８】
本実施形態では、たとえば高周波電源２８の出力が変わって自己バイアス電圧ＶSBが変化した場合、制御部５０は、上記のようにしてその新たな自己バイアス電圧ＶSBの値を測定することができるから、その新たな測定値に基づいて可変直流電源４６の出力電圧Ｖ0 を調整することで、静電吸着力Ｆを設定値Ｆs に安定に維持することができる。
【００３９】
好適な実施形態について上述説明したが、本発明は上記した実施形態に限定されるわけではなく、その技術的思想の範囲内で種々の変形・変更が可能である。
【００４０】
たとえば、静電吸着用電極は誘電性と漏電性とを併せ持つ膜または板を介して被処理体と対向配置されるものであればよく、その形状・構造・サイズを任意に選ぶことが可能である。したがって、静電チヤックシート以外の構成も可能である。
【００４１】
また、電流計４４および可変直流電源４６の回路構成ならびに制御部５０の回路構成・ソフトウェアも任意に変形・変更が可能である。また、制御部５０を設けないで、電流計４４の測定値を表示させ、作業員がその電流測定値を見ながら、マニュアル操作で可変直流電源４６の出力電圧を可変調整するようにしてもよい。
【００４２】
また、上記実施形態はプラズマエッチング装置に係るものであったが、本発明はプラズマアッシング装置、プラズマＣＶＤ装置等の他のプラズマ処理装置にも適用可能であり、半導体ウエハＷ以外の被処理体たとえばＬＣＤ基板にも適用可能である。
【００４３】
【発明の効果】
本発明の自己バイアス測定方法および装置によれば、静電吸着用電極に印加する直流電圧の値を変えながら被処理体と静電吸着用電極間の漏れ電流を検出し、印加直流電圧と漏れ電流の電圧電流特性に基づいて自己バイアス電圧の測定値を求めるようにしたので、誤差の少ない高精度な自己バイアス電圧測定値を短時間で容易に得ることができる。
【００４４】
本発明の静電吸着装置によれば、自己バイアス電圧の測定値に基づいて被処理体と静電吸着用電極間の電圧差が所望の静電吸着力を得るための電圧差となるように、静電吸着用電極に所定の可変直流電圧を印加するようにしたので、自己バイアス電圧が変わっても静電吸着力を設定値に安定に維持することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態におけるプラズマエッチング装置の全体構成を示す断面図である。
【図２】実施形態における自己バイアス測定方法の作用を説明するための電気回路図である。
【図３】実施形態における自己バイアス測定方法で用いられる可変直流電圧と漏れ電流間の電圧電流特性を示す図である。
【図４】実施形態における静電吸着装置で用いられる印加電圧−静電吸着力間の特性を示す図である。
【符号の説明】
１０処理容器
１８載置台
３０静電チャックシート
３２誘電体膜（抵抗体）
３４絶縁膜
３６導電膜（静電吸着用電極）
４４電流計
４６可変直流電源
５０制御部
Ｗ半導体ウエハ[0001]
[Industrial application fields]
The present invention relates to a self-bias measuring method and apparatus for measuring a self-bias voltage of an object to be processed in a plasma processing apparatus, and an electrostatic attraction apparatus for holding an object to be processed on a mounting table with an electrostatic attraction force.
[0002]
[Prior art]
For example, in the manufacture of semiconductor integrated circuits, plasma is used in various processes such as ashing, etching, CVD, and sputtering in order to promote ionization and chemical reaction of a processing gas. In a general plasma processing apparatus, a pair of electrodes are vertically arranged in a vacuum processing container, the upper electrode is connected to the ground potential, and a high frequency voltage is applied to the lower electrode (mounting table), whereby both electrodes In the meantime, a plasma is generated by discharge, and electrons, ions, etc. in the plasma are pulled into the object to be processed on the mounting table, such as a semiconductor wafer, by the force of an electric field so that the surface of the semiconductor wafer is subjected to a predetermined plasma treatment. ing.
[0003]
In such a plasma processing apparatus, since the high frequency voltage is applied to the lower electrode (mounting table) via the capacitor, the object to be processed on the mounting table is clamped to a negative potential so-called self-bias voltage in terms of DC. . That is, electrons (negative charge) in the plasma are attracted to the object to be processed in the half cycle in which the high-frequency voltage is positive, and ions (positive charge) in the plasma are in the half-cycle in which the high-frequency voltage is negative. Although it is attracted to the processing object side, it is attracted more because electrons are smaller in mass than ions and move more easily.As a result, the capacitor is constantly charged, and the object to be processed has a negative potential that is almost constant in terms of DC. Clamped to (self-bias voltage).
[0004]
The energy of ions incident on the object to be processed is influenced by the self-bias voltage. If this energy is too large, problems such as damage to the oxide film on the surface of the object to be processed occur. Therefore, in the plasma processing apparatus, it is necessary to measure the self-bias voltage and adjust it to a desired value. However, it is practically impossible to directly measure the self-bias voltage by applying a probe or the like to the object to be processed in the processing container. Therefore, conventionally, the potential of the lower electrode (mounting table) is measured via a voltage sense line or the like, and the self-bias voltage is estimated from the measured value.
[0005]
By the way, recent plasma processing apparatuses are provided with an electrostatic chuck that holds an object to be processed on a mounting table by electrostatic attraction without using a mechanical holding means such as a clamp. The initial type of electrostatic chuck is formed by, for example, oxidizing the surface of a mounting table made of aluminum to form an insulating film, and applying a high-voltage DC voltage to the mounting table to form an insulating film on the surface of the mounting table. This is a mechanism for generating static electricity on the boundary surface with the object to be processed by polarization and holding the object on the mounting table by the electrostatic adsorption force (Coulomb force). However, such an electrostatic chuck mechanism cannot obtain sufficient polarization in the insulating coating on the surface of the mounting table, and has an insufficient electrostatic attraction force. Nowadays, an electrostatic chuck having a structure in which an electrostatic chuck sheet formed by encapsulating a conductive film (electrostatic attracting electrode) in an insulating film is placed on the upper surface of a mounting table has become the mainstream.
[0006]
[Problems to be solved by the invention]
As described above, the conventional self-bias measurement method is a method of measuring the potential of the lower electrode (mounting table) and estimating the self-bias voltage from the measured value. However, an electrostatic chuck sheet or insulating film is interposed between the lower electrode and the object to be processed, and the corresponding resistance or capacitor acts. Therefore, the electric potential of the lower electrode and the electric potential of the object to be processed (self-bias voltage) The closeness to is not good. For this reason, the conventional method has many measurement errors, and a highly accurate self-bias voltage measurement value cannot be obtained.
[0007]
Conventionally, the value of the DC voltage applied to the electrostatic chucking electrode has been determined regardless of the self-bias voltage. For this reason, not only is it time-consuming to set or adjust the DC applied voltage to obtain the required electrostatic attraction force, but also after the adjustment, the self-adjustment occurs due to changes in processing conditions (for example, changes in high-frequency power for plasma generation). When the bias voltage changed, the electrostatic adsorption force also changed, and the condition was bad.
[0008]
The present invention has been made in view of such problems, and an object of the present invention is to provide a self-bias measurement method and apparatus capable of accurately measuring the self-bias voltage of an object to be processed in a plasma processing apparatus in a short time. To do.
[0009]
In addition, the present invention can hold an object to be processed with a desired electrostatic attraction force in a plasma processing apparatus and can stably maintain the electrostatic attraction force at a set value against fluctuations in self-bias voltage. An object is to provide an electrostatic adsorption device.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the first self-bias measuring method of the present invention measures the self-bias voltage of the object to be processed held by the electrostatic adsorption force on the mounting table in the processing container of the plasma processing apparatus. In the self-bias measurement method, a variable DC voltage is applied to the electrostatic chucking electrode of the mounting table, and a DC leakage between the workpiece and the electrostatic chucking electrode while changing a value of the DC voltage A method is used in which a current is detected and a measured value of the self-bias voltage is obtained based on a voltage-current characteristic between the voltage value of the DC voltage and the current value of the DC leakage current.
[0011]
The first self-bias measuring device of the present invention is a self-bias measuring device that measures a self-bias voltage of an object to be processed held by an electrostatic attraction force on a mounting table in a processing container of a plasma processing apparatus. Variable DC voltage generating means for applying a variable DC voltage to the electrostatic adsorption electrode of the mounting table, and a leakage current detection means for detecting a DC leakage current between the object to be processed and the electrostatic adsorption electrode; The DC voltage applied to the electrostatic chucking electrode of the mounting table is variably controlled by the variable DC voltage generating unit, and the DC voltage value and the current of the DC leakage current detected by the leakage current detecting unit are controlled. And a self-bias voltage detecting means for obtaining a measured value of the self-bias voltage based on a voltage-current characteristic between the values.
[0012]
The second self-bias measuring method of the present invention is the self-bias measuring method for measuring the self-bias voltage of the object to be processed held by the electrostatic attraction force on the mounting table in the processing container of the plasma processing apparatus. A variable DC voltage is applied to the electrostatic adsorption electrode of the pedestal, and a DC leakage current between the object to be processed and the electrostatic adsorption electrode is detected while changing a value of the DC voltage, and the DC leakage current is detected. The value of the DC voltage when the value becomes almost zero is used as the measured value of the self-bias voltage.
[0013]
Further, a second self-bias measuring device of the present invention is a self-bias measuring device that measures a self-bias voltage of an object to be processed held by an electrostatic adsorption force on a mounting table in a processing container of a plasma processing device. Variable DC voltage generating means for applying a variable DC voltage to the electrostatic adsorption electrode of the mounting table, and leakage current detection means for detecting a DC leakage current between the object to be processed and the electrostatic adsorption electrode; The DC voltage applied to the electrostatic chucking electrode of the mounting table is variably controlled from the variable DC voltage generating means, and the current detection value of the DC leakage current obtained from the leakage current detecting means becomes substantially zero. And a self-bias voltage detecting means for using the DC voltage at that time as a measured value of the self-bias voltage.
[0014]
The electrostatic attraction apparatus of the present invention is an electrostatic attraction apparatus for holding a target object on a mounting table with an electrostatic attraction force in a processing container of a plasma processing apparatus, wherein the electrostatic attraction force is applied to the target object. The electrostatic chucking electrode provided on the mounting table so as to exert influence, variable DC voltage generating means for applying a variable DC voltage to the electrostatic chucking electrode, the object to be processed, and the electrostatic chucking electrode; A leakage current detecting means for detecting a DC leakage current between the variable DC voltage and a voltage value of a variable DC voltage applied to the electrostatic adsorption electrode by the variable DC voltage generating means and the DC detected by the leakage current detecting means. Self-bias voltage detection means for obtaining a measurement value of the self-bias voltage based on a voltage-current characteristic between the current value of the leakage current, the measurement value of the self-bias voltage obtained from the self-bias voltage detection means, and a desired value The stillness of The variable direct current is applied so that a voltage substantially equal to the sum or difference value of the voltage difference between the object to be processed and the electrode for obtaining an adsorbing force is applied to the electrode for electrostatic attraction when the object to be processed is processed. Voltage control means for controlling the voltage generation means.
[0015]
In the first self-bias measuring method or the self-bias measuring device of the present invention, a variable DC voltage is applied to the electrostatic chucking electrode of the mounting table, and the workpiece and the electrostatic chuck are changed while changing the value of the variable DC voltage. A direct current leakage current flowing between the electrodes is detected, and a measured value of the self-bias voltage is obtained based on the voltage-current characteristics of the variable direct current voltage and the direct current leakage current. Generally, this voltage-current characteristic is expressed as a symmetric curve centered on the value of the self-bias voltage. For this reason, in the second self-bias measuring method or self-bias measuring device of the present invention, the value of the variable DC voltage when the DC leakage current becomes substantially zero is used as the measured value of the self-bias voltage.
[0016]
In the electrostatic attraction apparatus of the present invention, based on the measured value of the self-bias voltage obtained by the self-bias measurement method according to the present invention, the voltage difference between the workpiece and the electrode for electrostatic attraction is a desired electrostatic attraction force. A predetermined variable DC voltage is applied to the electrode for electrostatic attraction so as to obtain a voltage difference for obtaining the voltage. Since the electrostatic attraction force is controlled / adjusted by the voltage control means, even if the self-bias voltage changes, the variable DC voltage can be automatically adjusted to stably maintain the electrostatic attraction force at the set value.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0018]
FIG. 1 is a cross-sectional view showing a configuration of a plasma etching apparatus according to an embodiment of the present invention.
[0019]
The processing vessel 10 of this plasma etching apparatus is configured as a cylindrical chamber closed at both ends, for example, made of aluminum. On the side wall of the processing container 10, a gate valve 11 is provided for loading / unloading an object to be processed such as a semiconductor wafer W into / from the container 10.
[0020]
A cylindrical and conductive outer support frame 12 is erected on the bottom surface of the processing vessel 10. A bottomed cylindrical and insulating inner support frame 14 is fitted inside the outer support frame 12. A cylindrical support base 16 is disposed on the inner bottom portion of the inner support frame 14, and a disk-shaped mounting base 18 is fixed on the support base 16 by bolts (not shown). Both the support table 16 and the mounting table 18 are made of a conductive metal such as aluminum. A cooling jacket 20 is provided inside the support base 16, and the coolant supplied to the cooling jacket 20 through the introduction pipe 22 is discharged to the outside of the apparatus through the discharge pipe 24. The support table 16 and the mounting table 18 are formed with through holes 16 a and 18 a for supplying a gas for heat exchange, for example, helium gas, to the back surface of the semiconductor wafer W on the mounting table 18. A high frequency power supply 28 is connected to the mounting table 18 functioning as the lower electrode via a capacitor 26.
[0021]
A circular electrostatic chuck sheet 30 is crowned on the upper surface of the mounting table 18, and the semiconductor wafer W is mounted on the electrostatic chuck sheet 30. The electrostatic chuck sheet 30 has a dielectric material that also has a function as a resistor, for example, a thin film 32 made of SiC, and an insulating film 34 made of polyimide, for example, and the two are superposed on each other. A thin conductive film 36 made of, for example, copper foil is enclosed as an electrode. Also in this electrostatic chuck sheet 30, a vent hole 30 a for supplying helium gas for heat exchange to the back surface of the semiconductor wafer W on the mounting table 18 is formed.
[0022]
The conductive film 36 of the electrostatic chuck sheet 30 is provided outside of the processing vessel 10, the insulating coating conductive wire 38 that penetrates the mounting table 18, the support 16, the power supply rod 40 that penetrates the inner support frame 14 and the outer support frame 12. The coil 42 and the ammeter 44 are connected to the output terminal of the variable DC power supply 46.
[0023]
The coil 42, in cooperation with the capacitor 48, constitutes a low-pass filter for removing high frequency noise induced or mixed in the DC circuit. The ammeter 44 detects a current flowing through the DC circuit, that is, a leakage current between the semiconductor wafer W (object to be processed) and the conductive film 36 (electrostatic attracting electrode) of the electrostatic chuck sheet 30, and the current The leakage current detection signal ML representing the detection value is output to the control unit 50. The variable DC power supply 46 is configured to output an arbitrary DC voltage V0 designated by the voltage control signal ES from the control unit 50. The control unit 50 is composed of, for example, a microcomputer, and controls self-bias voltage measurement and controls / adjusts electrostatic attraction force in the present embodiment as will be described later.
[0024]
A gas introduction chamber 52 is disposed above the mounting table 18. The etching gas introduced into the gas introduction chamber 52 via the gas supply pipe 54 is discharged or directed toward the semiconductor wafer W at a uniform pressure / flow rate from the numerous vent holes 52b of the porous plate 52a facing the mounting table 18. Be injected. The gas introduction chamber 52 also serves as an upper electrode and is grounded. An exhaust port 56 is provided in a side wall near the bottom of the processing vessel 10, and a vacuum pump (not shown) is connected to the exhaust port 56 via an exhaust pipe 58.
[0025]
In the plasma etching apparatus having such a configuration, plasma etching is performed as follows. A high frequency voltage of, for example, 380 KHz and 15 KW is applied to the lower electrode (mounting table) 18 from a high frequency power source 28 via a capacitor 26, and the inside of the processing vessel 10 is vacuumed by a vacuum pump via an exhaust port 54 and an exhaust pipe 56. The etching gas is supplied into the processing container 10 through the gas supply pipe 54 and the gas introduction chamber 52 under a state where the gas is exhausted to a predetermined degree. Then, immediately below the gas introduction chamber 52, the gas molecules of the etching gas are ionized by the energy of the high frequency power, and plasma is generated. Etching is caused by electrons, ions, active species, and the like in the plasma entering the surface (surface to be processed) of the semiconductor wafer W on the mounting table 18 almost perpendicularly and causing a chemical reaction with the workpiece on the wafer surface. Done. The reaction product vaporized by the etching is exhausted from the exhaust port 56.
[0026]
While such etching is performed, a constant DC voltage is applied from the variable DC power supply 46 to the conductive film 36 of the electrostatic chuck sheet 30, and the dielectric film 32 is polarized by the DC voltage, so that the conductive film 36 A positive charge is induced on the upper surface and a negative charge is induced on the back surface of the semiconductor wafer W, and the semiconductor wafer W is attracted and held on the mounting table 18 by a Coulomb force between the positive charge and the negative charge.
[0027]
In addition, since a high frequency voltage is applied to the mounting table 18 as a lower electrode from a high frequency power supply 28 via a capacitor 26 and plasma is standing immediately above the semiconductor wafer W, a self-bias voltage is applied to the semiconductor wafer W. Is induced. According to the present embodiment, as will be described below, the self-bias voltage is accurately measured, and a desired electrostatic charge is placed on the mounting table 18 during the plasma etching based on the self-bias voltage measurement value. A direct current voltage for holding by the attractive force is applied from the variable direct current power source 46 to the conductive film 36 of the electrostatic chuck sheet 30.
[0028]
The self-bias measurement method in this embodiment will be described with reference to FIGS. FIG. 2 is a circuit diagram of a portion related to the self-bias measurement in the present embodiment. The dielectric film 32 of the electrostatic chuck sheet 30 is made of SiC having an intermediate resistivity (1 × 10 ⁸ to 1 × 10 ¹² Ω · cm) between the conductor and the insulator. Can do. Since the resistance value of the resistor 32 is considerably large, the resistance value of the conductor (42, 40, 38, etc.) from the variable DC power supply 46 to the conductive film 36 can be ignored. Further, since ions and electrons in the plasma PR move between the upper electrode 52 and the semiconductor wafer W, it is a conductive space.
[0029]
Therefore, as shown in FIG. 2, the ammeter 44, the resistor (dielectric film) 32, the semiconductor wafer W, the plasma PR, and the upper electrode 52 are connected in series between the output terminal of the variable DC power supply 46 and the ground. An electrical circuit is formed. In the steady state, the voltage distribution (potential) in the plasma PR is constant and stable, and the potential of the semiconductor wafer W is clamped to the self-bias voltage VSB with respect to the upper electrode 52 (earth potential). Therefore, assuming that the output voltage of the variable DC power supply 46 is V0, the resistance value of the resistor 32 is R, and the voltage drop in the ammeter 44 can be ignored, the DC current flowing in this electric circuit, that is, the semiconductor wafer W and the conductive film. The leakage current iL between the (electrostatic adsorption electrodes) 36 is expressed by the following equation.
iL = (V0-VSB) / R (1)
[0030]
In the above equation (1), the self-bias voltage VSB is constant, but the resistance value R of the resistor 32 varies depending on the voltage V0, temperature, the state of the back surface of the semiconductor wafer W, for example, the oxidation state.
[0031]
In this embodiment, the leakage current iL is detected by the ammeter 44 while changing the value of the output voltage V0 of the variable DC power supply 46 under the control of the control unit 50. Then, a voltage-current characteristic as shown in FIG. 3 is obtained between V0 and the absolute value | iL | of iL. In this voltage-current characteristic, | iL | becomes almost zero when V0 is approximately equal to VSB (self-bias voltage), and | iL | becomes parabolic as the difference (absolute value) between V0 and VSB increases. Increase. When V0 is larger than VSB, iL flows from the conductive film (electrostatic chucking electrode) 36 side to the semiconductor wafer W side. When V0 is smaller than VSB, iL flows from the semiconductor wafer W side to the conductive film 36 side. . A measured value of the self-bias voltage can be obtained based on such voltage-current characteristics.
[0032]
According to the preferred self-bias measurement method of this embodiment, when | iL | becomes substantially zero based on the above voltage-current characteristic that | iL | becomes substantially zero when V0 is substantially equal to VSB. The value of V0 is the measured value of the self-bias voltage VSB. The control unit 50 uses the value of the output voltage V0 of the variable DC power supply 46 when the leak current detection value ML indicating that | iL | is almost zero from the ammeter 44 as a measured value of the self-bias voltage VSB. Is determined. The control unit 50 can also display or record the measured value of the self-bias voltage VSB thus obtained by giving it to a display device or a recording device (not shown).
[0033]
Further, according to the second self-bias measurement method, based on the voltage-current characteristic that | iL | increases parabolically as the difference between V0 and VSB increases with the value of the self-bias voltage VSB as the center point. The intermediate value (V0a + V0b) / 2 of the values V0a and V0b when the current values iLa and iLb of the leakage current iL having the opposite polarities and the same absolute values are obtained is the measured value of the self-bias voltage VSB. In this case, the control unit 20 takes in the measured values of iL for each value of V0 into a storage unit (not shown), and calculates the measured values iLa and iLb having opposite polarities and equal absolute values by comparison operation, and as a result The values V0a and V0b of V0 corresponding to the measured values are determined, and the measured value of the self-bias voltage VSB is obtained from the voltage values V0a and V0b by calculation.
[0034]
In the present embodiment, the control unit 50 controls the output voltage V0 of the variable DC power supply 46 in an open loop, but it may be provided with voltage detection means for detecting V0 as necessary. Can be monitored or controlled, so that the measured value of the self-bias voltage VSB can be obtained with higher accuracy.
[0035]
In the self-bias measurement method of this embodiment, when V0 is brought close to VSB, the applied voltage (voltage difference) between the semiconductor wafer W and the conductive film (electrostatic attracting electrode) 36 is reduced, and the electrostatic attracting force is increased. Becomes smaller. Since the heat exchange gas is supplied to the back surface of the semiconductor wafer W, if the electrostatic attraction force is reduced, the semiconductor wafer W may be displaced from the mounting table 18 by the pressure of the heat exchange gas. Therefore, when this self-bias measurement method is performed in the plasma etching apparatus of FIG. 1, it is necessary to devise, for example, using a dummy semiconductor wafer W and holding it with an appropriate jig. In that respect, in the second self-bias measurement method, it is possible to determine the measured values iLa and iLb having opposite polarities and equal absolute values without bringing V0 close to VSB. The self-bias voltage VSB can be measured for the wafer W.
[0036]
The electrostatic attraction apparatus in the present embodiment includes an electrostatic chuck sheet 30, a variable DC power supply 46, an ammeter 44, and a control unit 50. The controller 50 determines the measured value of the self-bias voltage VSB of the semiconductor wafer W based on the voltage-current characteristic between the output voltage V0 of the variable DC power supply 46 and the leakage current iL detected by the ammeter 44 as described above. In addition to functioning as a required self-bias voltage detection means, a direct current voltage for holding the semiconductor wafer W on the mounting table 18 with a desired electrostatic attraction force during etching processing as described below is applied to the conductive film (for electrostatic attraction). It also functions as voltage control means for controlling the variable DC power supply 46 to be applied to the electrode 36.
[0037]
That is, there is a proportional relationship as shown in FIG. 4 between the applied voltage VF between the semiconductor wafer W and the conductive film (electrostatic attracting electrode) 36 and the electrostatic attracting force F, and this relationship (characteristic) is theoretically. Value or experimental value. When the required electrostatic attraction force Fs is set, the controller 50 adds the measured value of the self-bias voltage VSB to the value VFS of the applied voltage VF corresponding to this Fs, and is equal to the added value (VFS + VSB). The output voltage V0 is output to the variable DC power supply 46.
[0038]
In the present embodiment, for example, when the output of the high frequency power supply 28 changes and the self-bias voltage VSB changes, the control unit 50 can measure the value of the new self-bias voltage VSB as described above. By adjusting the output voltage V0 of the variable DC power supply 46 based on the new measurement value, the electrostatic attraction force F can be stably maintained at the set value Fs.
[0039]
Although the preferred embodiment has been described above, the present invention is not limited to the above-described embodiment, and various modifications and changes can be made within the scope of the technical idea.
[0040]
For example, the electrode for electrostatic adsorption only needs to be disposed opposite to the object to be processed via a film or plate having both dielectric properties and leakage, and the shape, structure, and size can be arbitrarily selected. is there. Therefore, configurations other than the electrostatic chuck sheet are possible.
[0041]
Further, the circuit configuration of the ammeter 44 and the variable DC power source 46 and the circuit configuration / software of the control unit 50 can be arbitrarily modified and changed. Further, the measurement value of the ammeter 44 may be displayed without providing the control unit 50, and the operator may variably adjust the output voltage of the variable DC power supply 46 by manual operation while viewing the current measurement value. .
[0042]
Moreover, although the said embodiment concerns the plasma etching apparatus, this invention is applicable also to other plasma processing apparatuses, such as a plasma ashing apparatus and a plasma CVD apparatus, and to-be-processed objects other than the semiconductor wafer W, for example, It can also be applied to LCD substrates.
[0043]
【The invention's effect】
According to the self-bias measuring method and apparatus of the present invention, the leakage current between the workpiece and the electrostatic adsorption electrode is detected while changing the value of the DC voltage applied to the electrostatic adsorption electrode, and the applied DC voltage and leakage are detected. Since the measured value of the self-bias voltage is obtained based on the voltage-current characteristics of the current, a highly accurate self-bias voltage measured value with less error can be easily obtained in a short time.
[0044]
According to the electrostatic attraction apparatus of the present invention, based on the measured value of the self-bias voltage, the voltage difference between the object to be processed and the electrostatic attraction electrode becomes a voltage difference for obtaining a desired electrostatic attraction force. Since the predetermined variable DC voltage is applied to the electrostatic chucking electrode, the electrostatic chucking force can be stably maintained at the set value even if the self-bias voltage changes.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the overall configuration of a plasma etching apparatus according to an embodiment of the present invention.
FIG. 2 is an electric circuit diagram for explaining the operation of the self-bias measurement method in the embodiment.
FIG. 3 is a diagram illustrating a voltage-current characteristic between a variable DC voltage and a leakage current used in the self-bias measurement method in the embodiment.
FIG. 4 is a diagram illustrating a characteristic between an applied voltage and an electrostatic attraction force used in the electrostatic attraction apparatus according to the embodiment.
[Explanation of symbols]
10 processing container 18 mounting table 30 electrostatic chuck sheet 32 dielectric film (resistor)
34 Insulating film 36 Conductive film (Electrostatic adsorption electrode)
44 Ammeter 46 Variable DC Power Supply 50 Control Unit W Semiconductor Wafer

Claims

In the self-bias measurement method for measuring the self-bias voltage of the object to be processed held by the electrostatic adsorption force on the mounting table in the processing container of the plasma processing apparatus, a variable DC voltage is applied to the electrostatic chucking electrode of the mounting table. And detecting the DC leakage current between the object to be processed and the electrostatic adsorption electrode while changing the value of the DC voltage, and the voltage value of the DC voltage and the current value of the DC leakage current A self-bias measuring method, wherein a measured value of the self-bias voltage is obtained based on a voltage-current characteristic between the two.

In the self-bias measuring device for measuring the self-bias voltage of the object to be processed held by the electrostatic adsorption force on the mounting table in the processing container of the plasma processing device,
Variable DC voltage generating means for applying a variable DC voltage to the electrostatic chucking electrode of the mounting table;
A leakage current detecting means for detecting a DC leakage current between the object to be processed and the electrode for electrostatic attraction;
The DC voltage applied to the electrostatic chucking electrode of the mounting table is variably controlled by the variable DC voltage generating unit, and the DC voltage value and the current of the DC leakage current detected by the leakage current detecting unit are controlled. And a self-bias voltage detecting means for obtaining a measured value of the self-bias voltage based on a voltage-current characteristic between the values.

In a self-bias measurement method for measuring a self-bias voltage of an object to be processed held by an electrostatic attraction force on a mounting table in a processing container of a plasma processing apparatus,
A variable DC voltage is applied to the electrostatic chucking electrode of the mounting table, and a DC leakage current between the workpiece and the electrostatic chucking electrode is detected while changing a value of the DC voltage, and the DC A self-bias measurement method characterized in that a value of the DC voltage when a leakage current becomes substantially zero is used as a measurement value of the self-bias voltage.

In the self-bias measuring device for measuring the self-bias voltage of the object to be processed held by the electrostatic adsorption force on the mounting table in the processing container of the plasma processing device,
Variable DC voltage generating means for applying a variable DC voltage to the electrostatic chucking electrode of the mounting table;
A leakage current detecting means for detecting a DC leakage current between the object to be processed and the electrode for electrostatic attraction;
When the DC voltage applied to the electrostatic chucking electrode of the mounting table is variably controlled from the variable DC voltage generating means, and the current detection value of the DC leakage current obtained from the leakage current detecting means is substantially zero. And a self-bias voltage detecting means for using the direct-current voltage as a measurement value of the self-bias voltage.

In an electrostatic attraction apparatus for holding an object to be processed on a mounting table with an electrostatic attraction force in a processing container of a plasma processing apparatus,
An electrode for electrostatic attraction provided on the mounting table so as to exert the electrostatic attraction force on the object to be processed;
Variable DC voltage generating means for applying a variable DC voltage to the electrostatic adsorption electrode;
A leakage current detecting means for detecting a DC leakage current between the object to be processed and the electrode for electrostatic attraction;
Based on the voltage-current characteristics between the voltage value of the variable DC voltage applied to the electrostatic attraction electrode from the variable DC voltage generation means and the current value of the DC leakage current detected by the leakage current detection means. Self-bias voltage detection means for obtaining a measured value of the self-bias voltage;
A voltage approximately equal to the sum or difference value of the measured value of the self-bias voltage obtained from the self-bias voltage detection means and the voltage difference between the object to be processed and the electrode for obtaining a desired electrostatic attraction force And a voltage control means for controlling the variable DC voltage generating means so as to be applied to the electrostatic attraction electrode during processing of the object to be processed.