JP3648096B2

JP3648096B2 - Processing equipment

Info

Publication number: JP3648096B2
Application number: JP17976799A
Authority: JP
Inventors: 敏英高島
Original assignee: Tokyo Electron Ltd
Current assignee: Tokyo Electron Ltd
Priority date: 1999-06-25
Filing date: 1999-06-25
Publication date: 2005-05-18
Anticipated expiration: 2019-06-25
Also published as: JP2001007074A

Description

【０００１】
【発明の属する技術分野】
本発明は，処理液を用いて基板などを処理する処理装置に関する。
【０００２】
【従来の技術】
例えば，半導体デバイスの製造工程では，半導体ウェハ（以下，「ウェハ」という。）を所定の薬液や純水等の洗浄液によって洗浄し，ウェハの表面に付着したパーティクル，有機汚染物，金属不純物等のコンタミネーションを除去する洗浄装置が使用されている。その中でも，洗浄液が充填された洗浄槽内にウェハを浸漬させて洗浄処理を行うウェット型の洗浄装置は，ウェハに付着したパーティクル等を効果的に除去できるため広く普及している。
【０００３】
ウェット型の洗浄装置においては，供給回路を通じて洗浄槽に供給された洗浄液中にウェハを浸漬させている。そして，洗浄中は供給回路を通じて新たな洗浄液を洗浄槽に供給し続ける一方で，洗浄槽内の洗浄液を排液回路を通じて排液し，洗浄槽内の洗浄液を清浄度の高い洗浄液に置換しながら，洗浄処理を行うようにしている。ここで，排液回路と供給回路との間は，ポンプ，ダンパ，ヒータ，フィルタを順に介装した循環回路によって接続されており，洗浄槽から排液された洗浄液は，排液回路から循環回路に流れて，循環回路で浄化及び温調された後に供給回路を通じて再び洗浄槽に供給される。これにより，洗浄液の再利用を図って洗浄液の消費量を節約しながら，洗浄槽内の洗浄液の温度や清浄度を所定の状態に保つことができる。洗浄槽で使用される洗浄液には，例えば，アンモニア水溶液（ＮＨ_４ＯＨ）と過酸化水素水（Ｈ_２Ｏ_２）と純水（Ｈ_２Ｏ）との混合液であるＡＰＭ，塩酸（ＨＣｌ）と過酸化水素水と純水との混合液であるＨＰＭ，硫酸（Ｈ_２ＳＯ_４）と過酸化水素水との混合液であるＳＰＭ，燐酸（Ｈ_３ＰＯ_４）を含んだ液体やエチレングリコール（ＨＯＣＨ_２ＣＨ_２ＯＨ）等の薬液が知られている。
【０００４】
また，洗浄処理が終了すると，供給回路や排液回路を通じて洗浄槽から洗浄液を排液させ，洗浄槽を一旦空にしている。このとき，洗浄槽内の洗浄液は，自重によって供給回路や排液回路に流れ込んで自然排液される。その後，新しい洗浄液が供給回路を通じて洗浄槽に供給され，次のウェハの洗浄処理に備えることになる。
【０００５】
【発明が解決しようとする課題】
しかしながら，従来の洗浄装置では，自重によって洗浄液を排液するので，粘度が高いＳＰＭ，燐酸（Ｈ_３ＰＯ_４）を含んだ液体やエチレングリコール等の薬液では，排液に時間がかかる。例えば，３４リットル容量の洗浄槽にＳＰＭが充填されていた場合，排液には５分程度要し，これは，洗浄処理を繰り返す毎に累積されることになるので，スループットに悪影響を与える。
【０００６】
従って，本発明の目的は，粘度が高い処理液でも短時間で排液することができる処理装置を提供することにある。
【０００７】
【課題を解決するための手段】
上記課題を解決するために，本発明は，基板を収納する処理槽に処理液を供給する供給回路と，前記処理槽から処理液を排液する排液回路と，前記供給回路と前記排液回路との間を接続する循環回路と，前記循環回路に介装され前記排液回路側から前記供給回路側に処理液を送液するポンプとフィルタを備えた処理装置において，前記供給回路と前記循環回路との接続点よりも前記処理槽側において供給回路に一端が接続され，前記排液回路と前記循環回路との接続点よりも前記処理槽側において前記排液回路に他端が接続されるか若しくは前記ポンプの上流側において循環回路に他端が接続された第１の迂回回路と，前記ポンプの下流側であって前記フィルタの上流側において前記循環回路に一端が接続された第２の迂回回路とを備え，前記第１の迂回回路に第１の弁を設け，前記第２の迂回回路に第２の弁を設け，前記供給回路と前記循環回路の接続点と前記供給回路と前記第１の迂回回路の接続点との間において前記供給回路に第３の弁を設け，前記供給回路と前記循環回路の接続点よりも前記処理槽の反対側において前記供給回路に第４の弁を設け，前記排液回路と前記循環回路の接続点よりも前記処理槽の反対側において前記排液回路に第５の弁を設け，前記処理槽は，基板を収納する内槽と前記内槽から溢れ出た処理液を受け止める外槽とを備え，前記排液回路の一端が前記外槽に接続されており，前記排液回路と前記第１の迂回回路との接続点よりも前記処理槽側において前記排液回路に第６の弁を設けると共に，前記外槽に液面の下限位置を検出する液面下限センサを設け，前記処理槽からの処理液排液時に，前記第１，２，６の弁を開き，前記ポンプにより送液排液し，前記外槽が空になると，これを前記液面下限センサが検出して前記第６の切換弁を閉じるように構成したことを特徴とする。
【０００８】
請求項１に記載の処理装置によれば，まず，第１の弁，第２の弁，第５の弁を閉じ，第３の弁,第４の弁を開いて供給回路から処理液を処理槽に供給し，処理槽内に処理液を充填する。そして，処理槽内の処理液に基板を浸漬させて処理を行う。処理中は第４の弁を閉じて供給回路から処理液を供給しない一方で，処理槽から排液回路を通じて排液された処理液を循環回路に流入させ，ポンプの稼働によって供給回路から処理槽に循環供給する。
【０００９】
処理後，処理槽から処理液を排液し処理槽を空にする。このとき，第３の弁，第４の弁，第５の弁を閉じる一方で，第１の弁，第２の弁を開く。そして，供給回路と排液回路を通じて処理液を処理槽から排液する。この場合，処理液を，供給回路から第１の迂回回路，循環回路に順に流し，ポンプによって送液して排液することができる。即ち，処理槽から供給回路を通じて排液される処理液は，第３の弁が閉じているので，供給回路から第１の迂回回路に流れ込む。そして，第１の迂回回路の他端が，排液回路と循環回路との接続点よりも処理槽側において排液回路に接続されるか若しくはポンプの上流側において循環回路に接続されているので，第１の迂回回路内の処理液は，排液回路から循環回路に流れ込むか若しくは直接循環回路に流れ込む。そして，処理液は，循環回路においてポンプによって送液されて第２の迂回回路に流れ込み，外部に排液される。また，処理槽から排液回路を通じて排液される処理液は，排液回路から循環回路，第２の迂回回路の順で流れて外部に排液される。この場合も，処理液をポンプによって送液して排液することができる。このように請求項１では，ポンプによって送液するので，自重で排液させた場合に比べて，粘度が高い処理液でも短時間で排液することが可能になる。しかも，循環回路に設けられた既存のポンプを利用するので，排液用の新たなポンプを設ける必要もない。
【００１０】
請求項１に記載の処理装置において，請求項２に記載したように，前記第２の迂回回路の他端が，前記第５の弁よりも前記処理槽の反対側において前記排液回路に接続されていても良い。この場合，排液回路から循環回路に流れ込んだ処理液は，ポンプで送液された後に，第２の迂回回路から再び排液回路に流れ込んで外部に排液される。
【００１１】
前記処理槽は，基板を収納する内槽と前記内槽から溢れ出た処理液を受け止める外槽を備え，前記排液回路の一端が前記外槽に接続されている。かかる構成によれば，外槽内の処理液は，排液回路を通じて外槽から排液される。
【００１２】
また，前記排液回路と前記第１の迂回回路との接続点よりも前記処理槽側において前記排液回路に第６の弁を設けると共に，前記外槽に液面の下限位置を検出する液面下限センサを設け，前記第６の弁の開閉を前記液面下限センサの検出に基づいて行うように構成する。かかる構成によれば，まず，第６の弁を開き，外槽内の処理液を排液回路を通じて外槽から排液する。その後，外槽から処理液が全て排液されて外槽が空になると，これを液面下限センサが検出し，所定の時間が経過した後に第６の弁を閉じる。これにより，排液回路からポンプに空気が入り込むことがなくなり，ポンプの空気噛み込みを防止することができる。
【００１３】
【発明の実施の形態】
以下，添付図面を参照しながら本発明の好ましい実施の形態を説明する。図１は，本実施の形態にかかる洗浄装置１２を備えた洗浄システム１の斜視図である。この洗浄システム１は，キャリアＣ単位での基板としてのウェハＷの搬入，ウェハＷの洗浄，ウェハＷの乾燥，キャリアＣ単位でのウェハＷの搬出までを一貫して行うように構成されている。
【００１４】
この洗浄システム１において，搬入・取出部２は，洗浄前のウェハＷを２５枚収納したキャリアＣを搬入しウェハＷを洗浄に移行させるまでの動作を行う。即ち，搬入部５に載置されたキャリアＣを移送装置６によってローダ７へ例えば２個ずつ搬送し，このローダ７でキャリアＣからウェハＷを取り出す構成になっている。
【００１５】
洗浄乾燥処理部１０には，搬入・取出部２側から順に，ウェハＷを搬送する搬送装置３０のウェハチャック３０ａを洗浄および乾燥するためのウェハチャック洗浄・乾燥装置１１，各種の薬液や純水等の洗浄液を用いてウェハＷを洗浄する各洗浄装置１２〜１９，搬送装置３３のウェハチャック３３ａを洗浄および乾燥するためのウェハチャック洗浄・乾燥装置２０，および，洗浄装置１２〜１９で洗浄されたウェハＷを，例えばイソプロピルアルコール（ＩＰＡ）蒸気を用いて乾燥させる乾燥装置２１が配列されている。
【００１６】
ウェハチャック洗浄・乾燥装置１１，２０では，例えば純水などを用いてウェハチャック３０ａとウェハチャック３３ａの洗浄，乾燥をそれぞれ行う。また，一般的な洗浄プロセスに従い，薬液洗浄とリンス洗浄とが交互に行えるように洗浄乾燥処理部１０では，洗浄装置１２，１４，１６，１８は薬液洗浄を行うように構成され，洗浄装置１３，１５，１７，１９はリンス洗浄を行うように構成されている。その一例として，洗浄装置１２では，硫酸成分を主体とした洗浄液であって，粘度が高いＳＰＭ（Ｈ_２ＳＯ_４／Ｈ_２Ｏ_２の混合液）を用いた洗浄処理を行って，ウェハＷの表面に付着している有機汚染物等の不純物質を除去する。また，洗浄装置１６では，例えばアンモニア成分を主体とした洗浄液であるＡＰＭ（ＮＨ_４ＯＨ／Ｈ_２Ｏ_２／Ｈ_２Ｏの混合液）を用いた洗浄処理を行って，ウェハＷの表面に付着している有機汚染物，パーティクル等の不純物質を除去する。また，洗浄装置１４，１８では，何れもフッ酸成分を主体とした洗浄液であるＤＨＦ（ＨＦ／Ｈ_２Ｏの混合液）を用いた洗浄処理を行って，ウェハＷの表面に形成された酸化膜等を除去する。また，洗浄装置１３，１５，１７，１９では，純水を用いてウェハＷのリンス洗浄を行う。更に，乾燥装置２０では，ＩＰＡ蒸気を利用してウェハＷの表面を乾燥処理するように構成されている。
【００１７】
なお以上の配列や各洗浄装置１２〜１９の組合わせは，ウェハＷに対する洗浄処理の種類によって任意に組み合わせることができる。例えば，ある洗浄装置を減じたり，逆にさらに他の種類の薬液を用いてウェハＷを薬液洗浄する洗浄装置を付加してもよい。
【００１８】
装填・搬出部５０は，洗浄乾燥処理部１０で洗浄，乾燥された２５枚のウェハＷをキャリアＣに装填後キャリアＣ単位で搬出する。即ち，アンローダ５１によって，洗浄後のウェハＷが収納されたキャリアＣを，移送装置（図示せず）によって，搬出部５２にまで搬送する構成になっている。
【００１９】
次に，本実施の形態にかかる洗浄装置１２の構成について説明する。この洗浄装置１２は，粘度が高いＳＰＭでも円滑に排液できるように構成されている。図２に示すように，洗浄装置１２に備えられた洗浄槽６０は，ウェハＷを収納するのに充分な大きさを有する箱形の内槽６１と外槽６２から構成されている。外槽６２は，内槽６１の上端からオーバーフローしたＳＰＭを受けとめるように，内槽６１の開口部を取り囲んで装着されている。
【００２０】
内槽６１の下方には，水槽６３を介して超音波振動子を内蔵しているメガソニック装置６４が装着されている。メガソニック装置６４から発振された超音波は，水槽６３の水を経て内槽６１内のＳＰＭに伝搬し，ＳＰＭを振動させてウェハＷの表面に付着しているパーティクルを除去する作用がある。
【００２１】
内槽６１には図示しないＳＰＭ供給源からのＳＰＭを内槽６１に供給する供給回路７０が接続され，外槽６２にはＳＰＭを例えば工場の排液ライン等に排液する排液回路７１が接続され，これら供給回路７０と排液回路７１との間は，循環回路７２によって接続されている。そして，この循環回路７２に介装されたポンプ７３は，循環回路７２内のＳＰＭを排液回路７１側から供給回路７０側に送液するように構成されている。
【００２２】
ここで，供給回路７０と循環回路７２との接続点Ｎ１よりも洗浄槽６０側において供給回路７０に一端が接続され，排液回路７１と循環回路７２との接続点Ｎ２よりも洗浄槽６０側において排液回路７１に他端が接続されている第１の迂回回路７４が設けられている。この第１の迂回回路７４を介して，内槽６１から供給回路７０を通じて排液されるＳＰＭを排液回路７１に流入させることができるようになっている。また，ポンプ７３の下流側において循環回路７２に一端が接続され，後述する第５の切換弁８４よりも洗浄槽６０の反対側において排液回路７１に他端が接続されている第２の迂回回路７５が設けられている。この第２の迂回回路７５を介して，ポンプ７３によって送液されるＳＰＭを排液回路７１に流入させて排液ラインに排液することができるようになっている。
【００２３】
第１の迂回回路７４に第１の切換弁８０を設け，第２の迂回回路７５に第２の切換弁８１を設け，供給回路７０と循環回路７２の接続点Ｎ１と供給回路７０と第１の迂回回路７４の接続点Ｎ３との間において供給回路７０に第３の切換弁８２を設け，供給回路７０と循環回路７２の接続点Ｎ１よりも洗浄槽６０の反対側において供給回路７０の途中に第４の切換弁８３を設け，排液回路７１と循環回路７２の接続点Ｎ２よりも洗浄槽６０の反対側において排液回路７１に前述した第５の切換弁８４を設け，排液回路７１と第１の迂回回路７４との接続点Ｎ４よりも洗浄槽６０側において排液回路７１に第６の切換弁８５を設ける。これら第１の切換弁８０，第２の切換弁８１，第３の切換弁８２，第４の切換弁８３，第５の切換弁８４，第６の切換弁８５は何れも，電磁（ソレノイド）方式の２方口弁であり，電源制御機構９０からの電力の供給によって，開閉の切り換えが制御されるようになっている。従って，各回路は，その時々に応じて流路を導通又は遮断して，ＳＰＭを流すか否かを選択できるようになっている。
【００２４】
循環回路７２には，ポンプ７３以外に，ダンパ８６，ヒータ８７，フィルタ８８がポンプ７３の下流側に順に介装されている。洗浄中は，第１の切換弁８０，第２の切換弁８１，第４の切換弁８３，第５の切換弁８４を閉じ，第３の切換弁８２,第６の切換弁８５を開いて，内槽６１から外槽６２にオーバーフローしたＳＰＭを，排液回路７１から循環回路７２に流し，循環回路７２で温調及び浄化した後に供給回路７０を通じて内槽６１に再び供給するようになっている。
【００２５】
また，外槽６２は，外槽６２内のＳＰＭの液面の下限位置を検出する液面下限センサ９１を備えている。この液面下限センサ９１は，外槽６２に窒素（Ｎ_２）ガスを送り続ける管路９２の途中に装着されており，Ｎ２ガスの圧力を測定することによって，間接的に外槽６２内のＳＰＭの液面の下限位置を検出する。液面下限センサ９１の検出信号は，電源制御機構９０に出力されるようになっており，第６の切換弁８５の開閉は，液面下限センサ９１の検出に基づいて，電源制御機構９０によって行うように構成されている。外槽６２からＳＰＭを排液する際には第６の切換弁８５を開き，外槽６２から全てのＳＰＭが排液されて所定の時間が経過すると，第６の切換弁８５を閉じるようになってる。
【００２６】
なお，その他，洗浄装置１３〜１９も洗浄装置１２と同様な構成にし，ポンプ７３を利用して槽内の洗浄液を円滑に排液できるように構成してもよい。
【００２７】
次に，以上のように構成された洗浄装置１２で行われる洗浄処理について，図１の洗浄システム１におけるウェハＷの洗浄工程に基づいて説明する。まず，図示しない搬送ロボットが未だ洗浄されていないウェハＷを例えば２５枚ずつ収納したキャリアＣを搬入・取出部２の搬入部５に複数載置する。そして，この搬入・取出部２によって，例えばキャリアＣ２個分の５０枚のウェハＷをキャリアＣから取り出し，搬送装置３０が，ウェハＷを５０枚単位で一括して把持する。そして，それらウェハＷを搬送装置３１，３２，３３に引きつきながら，各洗浄装置１２〜１９に順次搬送する。こうして，ウェハＷの表面に付着しているパーティクル等の不純物質を除去する洗浄を行う。
【００２８】
ここで，粘度が高い薬液であるＳＰＭ（Ｈ_２ＳＯ_４／Ｈ_２Ｏ_２の混合液）を用いて薬液洗浄を行う洗浄装置１２での処理について説明する。まず，第１の切換弁８０，第２の切換弁８１，第５の切換弁８４を閉じ，第３の切換弁８２,第４の切換弁８３を開く。図示しないＳＰＭ供給源から供給回路７０を通じてＳＰＭを洗浄槽６０に供給し，洗浄槽６０内にＳＰＭを予め充填しておく。
【００２９】
その後，搬送装置３０によって５０枚のウェハＷを一括して内槽６１内に収納し，ＳＰＭによる薬液洗浄を開始する。図２に示したように，洗浄中は第４の切換弁８３を閉じて供給回路７０から新たなＳＰＭを供給しない一方で，外槽６２から排液回路７１を通じて排液されたＳＰＭを循環回路７２に流入させ，以後，ポンプ７３の稼働によって，供給回路７０から洗浄槽６０に循環供給する。循環回路７２では，ダンパ８６，ヒータ８７，フィルタ８８の順で流して浄化及び温調を行い，ＳＰＭの再利用を図っている。内槽６１ではＳＰＭの上昇流を形成させ，ウェハＷの表面を均一に洗浄している。このように，洗浄槽６０内のＳＰＭを繰り返して利用するので，ＳＰＭの消費量を節約することができる。
【００３０】
洗浄後，洗浄槽６０からＳＰＭを排液し洗浄槽６０を空にする。このとき，第３の切換弁８２，第４の切換弁８３，第５の切換弁８４を閉じる一方で，第１の切換弁８０，第２の切換弁８１を開く。そして，供給回路７０と排液回路７１を通じてＳＰＭを洗浄槽６０から排液する。この場合，ＳＰＭを，供給回路７０から第１の迂回回路７４，循環回路７２に順に流し，ポンプ７３によって送液して排液することができる。図３は，このときの状態を示している。
【００３１】
即ち，内槽６１から供給回路７０を通じて排液されるＳＰＭは，第３の切換弁８２が閉じているので，供給回路７０から第１の迂回回路７４に流れ込む。そして，第１の迂回回路７４の他端が，排液回路７１と循環回路７２の接続点Ｎ２よりも洗浄槽６０側において排液回路７１に接続されているので，第１の迂回回路７４内のＳＰＭは，排液回路７１から循環回路７２に流れ込む。そして，ＳＰＭは，循環回路７２においてポンプ７３によって送液されて第２の迂回回路７５に流れ込んだ後に，再び排液回路７１に流れ込み，工場の排液ラインに排液される。
【００３２】
また，外槽６２から排液回路７１を通じて排液されるＳＰＭは，排液回路７１から循環回路７２，第２の迂回回路７５の順に流れて，内槽６１から排液されるＳＰＭの時と同様に排液ラインに排液される。この場合も，ＳＰＭをポンプ７３によって送液して排液することができる。ここで，図示の如く，第２の迂回回路７５の一端は，ポンプ７３の下流側であると共に，ヒータ８７の上流側において循環回路７２に接続されている。ポンプ７３によって送液されたＳＰＭの流動性が，ヒータ８７，フィルタ８８による圧力降下によって低下する前に，第２の迂回回路７５にＳＰＭを流入させて排液回路７１から排液することができるからである。
【００３３】
外槽６２からＳＰＭが全て排液されて外槽６２が空になると，これを液面下限センサ９１が検出して電源制御機構９０に出力し，電源制御機構９０は，所定の時間が経過した後に第６の切換弁８５を閉じるようにする。これにより，排液回路７１からポンプ７３に空気が入り込むことがなくなり，ポンプ７３の空気噛み込みを防止することができる。
【００３４】
このように，本実施の形成の洗浄装置１２では，ポンプ７３によって送液するので，自重で排液させた場合に比べて，粘度が高いＳＰＭでも短時間で排液することが可能になる。例えば，３４リットル容量の洗浄槽６０にＳＰＭが充填されていた場合，ポンプ７３の吐出量が１５リットル／ｍｉｎであれば，排液時間は２分数秒で済み，さらにポンプ７３の吐出量が５５リットル／ｍｉｎであれば，排液時間は１分以内で済ますことができる。しかも，循環回路７２に設けられた既存のポンプ７３を利用するので，排液用の新たなポンプを設ける必要もない。
【００３５】
かくして，本実施の形態の洗浄装置１２によれば，循環回路７２のポンプ７３を利用して排液を行うので，粘度が高いＳＰＭでも短時間で排液することができる。従って，処理時間も短縮することになり，経済的な負担をかけずにスループットの向上を図ることが可能になる。
【００３６】
以上のような洗浄装置１２は，その他の粘度が高い洗浄液，例えば燐酸（Ｈ_３ＰＯ_４）を含んだ液体やエチレングリコール等の薬液に対しても有効である。また，第１の迂回回路７４の他端を排液回路７１に接続する代わりに，第１の迂回回路７４の他端をポンプ７３の上流側において循環回路７２に接続して，第１の迂回回路７４内のＳＰＭを直接循環回路７２に流すようにしてもよい。
【００３７】
なお，本発明は，この実施の形態に限定されるものではなく，種々の態様を採りうるものである。例えば，１つの洗浄槽で複数の洗浄液を使用するワンバス・タイプ（一槽多薬型等とも称呼されている。）の洗浄装置などにも本発明を適用しても良い。また，基板は，上記ウェハＷに限るものではなく，例えばＬＣＤ基板，ＣＤ基板，プリント基板，セラミック基板であっても良い。
【００３８】
【発明の効果】
本発明によれば，循環回路のポンプを利用して排液を行うので，粘度が高い処理液でも短時間で排液することができる。従って，処理時間も短縮することになり，経済的な負担をかけずにスループットの向上を図ることが可能になる。特に，排液中のポンプの空気噛み込むを防止することができる。
【図面の簡単な説明】
【図１】本実施の形態にかかる洗浄装置を備えた洗浄システムの斜視図である。
【図２】本実施の形態にかかる洗浄装置の回路系統を示す説明図である。
【図３】図２の洗浄装置においてＳＰＭを排液する際の様子を示している説明図である。
【符号の説明】
１洗浄システム
１２洗浄装置
６０洗浄槽
７０供給回路
７１排液回路
７２循環回路
７３ポンプ
７４第１の迂回回路
７５第２の迂回回路
８０第１の切換弁
８１第２の切換弁
８２第３の切換弁
８３第４の切換弁
８４第５の切換弁
８５第６の切換弁
９１液面下限センサ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a processing apparatus for processing a substrate or the like using a processing liquid.
[0002]
[Prior art]
For example, in a semiconductor device manufacturing process, a semiconductor wafer (hereinafter referred to as “wafer”) is cleaned with a cleaning solution such as a predetermined chemical solution or pure water to remove particles, organic contaminants, metal impurities, etc. A cleaning device for removing contamination is used. Among them, a wet type cleaning apparatus that performs a cleaning process by immersing a wafer in a cleaning tank filled with a cleaning liquid is widely used because particles and the like attached to the wafer can be effectively removed.
[0003]
In a wet type cleaning apparatus, a wafer is immersed in a cleaning solution supplied to a cleaning tank through a supply circuit. During cleaning, while supplying a new cleaning liquid to the cleaning tank through the supply circuit, the cleaning liquid in the cleaning tank is drained through the drain circuit, and the cleaning liquid in the cleaning tank is replaced with a highly clean cleaning liquid. , Cleaning process is performed. Here, the drain circuit and the supply circuit are connected by a circulation circuit in which a pump, a damper, a heater and a filter are interposed in order, and the cleaning liquid drained from the cleaning tank is transferred from the drain circuit to the circulation circuit. After being purified and temperature-controlled in the circulation circuit, it is supplied again to the washing tank through the supply circuit. Thereby, the temperature and cleanliness of the cleaning liquid in the cleaning tank can be maintained in a predetermined state while reusing the cleaning liquid and saving the consumption of the cleaning liquid. Examples of the cleaning liquid used in the cleaning tank include APM, hydrochloric acid (HCl), which is a mixed liquid of an aqueous ammonia solution (NH ₄ OH), a hydrogen peroxide solution (H ₂ O ₂ ), and pure water (H ₂ O). HPM that is a mixture of hydrogen peroxide water and pure water, SPM that is a mixture of sulfuric acid (H ₂ SO ₄ ) and hydrogen peroxide, and a liquid containing ethylene glycol or phosphoric acid (H ₃ PO ₄ ) Chemical solutions such as (HOCH ₂ CH ₂ OH) are known.
[0004]
When the cleaning process is completed, the cleaning liquid is drained from the cleaning tank through the supply circuit and the drain circuit, and the cleaning tank is once emptied. At this time, the cleaning liquid in the cleaning tank flows into the supply circuit and the drain circuit due to its own weight and is naturally discharged. Thereafter, a new cleaning liquid is supplied to the cleaning tank through the supply circuit to prepare for the next wafer cleaning process.
[0005]
[Problems to be solved by the invention]
However, in the conventional cleaning apparatus, since the cleaning liquid is discharged by its own weight, it takes time to discharge the liquid containing SPM having high viscosity, phosphoric acid (H ₃ PO ₄ ), or a chemical liquid such as ethylene glycol. For example, when a 34 liter cleaning tank is filled with SPM, draining takes about 5 minutes, and this is accumulated every time the cleaning process is repeated, which adversely affects the throughput.
[0006]
Accordingly, an object of the present invention is to provide a processing apparatus capable of draining a processing solution having a high viscosity in a short time.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a supply circuit that supplies a processing liquid to a processing tank that accommodates a substrate, a drain circuit that drains the processing liquid from the processing tank, the supply circuit, and the liquid drain A processing circuit comprising: a circulation circuit that connects between the circuit; a pump that is interposed in the circulation circuit and that feeds the processing liquid from the drain circuit side to the supply circuit side; and a filter. One end is connected to the supply circuit on the treatment tank side from the connection point with the circulation circuit, and the other end is connected to the drain circuit on the treatment tank side than the connection point between the drain circuit and the circulation circuit. Or a first bypass circuit having the other end connected to the circulation circuit on the upstream side of the pump, and a second bypass circuit connected to the circulation circuit on the downstream side of the pump and upstream of the filter . With a detour circuit A first valve is provided in the first bypass circuit, a second valve is provided in the second bypass circuit, a connection point between the supply circuit and the circulation circuit, and a connection between the supply circuit and the first bypass circuit A third valve is provided in the supply circuit between the points, and a fourth valve is provided in the supply circuit on the opposite side of the processing tank from a connection point between the supply circuit and the circulation circuit, and the drain circuit The drain circuit is provided with a fifth valve on the opposite side of the processing tank from the connection point of the circulation circuit, and the processing tank contains an inner tank for storing a substrate and a processing liquid overflowing from the inner tank. An outer tank to be received, and one end of the drainage circuit is connected to the outer tank, and the drainage circuit is connected to the drainage circuit on the processing tank side from a connection point between the drainage circuit and the first bypass circuit. A sixth valve is provided, and a liquid level lower limit sensor for detecting a lower limit position of the liquid level in the outer tank. The provided, during processing fluid discharge from said processing tank, the opening of the first 1, 2 and 6 of the valve, was fed drained by the pump, when the outer tub is empty, the liquid surface lower limit sensor this Is detected and the sixth switching valve is closed .
[0008]
According to the processing apparatus of claim 1, first, the first valve, the second valve, and the fifth valve are closed, the third valve and the fourth valve are opened, and the processing liquid is processed from the supply circuit. Supply to the tank and fill the treatment liquid into the treatment tank. And it processes by immersing a board | substrate in the processing liquid in a processing tank. During the processing, the fourth valve is closed and the processing liquid is not supplied from the supply circuit. On the other hand, the processing liquid discharged from the processing tank through the drain circuit is caused to flow into the circulation circuit. Circulate to supply.
[0009]
After the treatment, drain the treatment liquid from the treatment tank and empty the treatment tank. At this time, the first valve and the second valve are opened while the third valve, the fourth valve, and the fifth valve are closed. Then, the processing liquid is drained from the processing tank through the supply circuit and the drain circuit. In this case, the processing liquid can flow from the supply circuit to the first bypass circuit and the circulation circuit in order, and can be sent and discharged by a pump. That is, the processing liquid discharged from the processing tank through the supply circuit flows from the supply circuit into the first bypass circuit because the third valve is closed. Since the other end of the first bypass circuit is connected to the drain circuit on the treatment tank side or connected to the circulation circuit on the upstream side of the pump from the connection point between the drain circuit and the circulation circuit. The processing liquid in the first bypass circuit flows from the drain circuit into the circulation circuit or directly into the circulation circuit. Then, the processing liquid is sent by the pump in the circulation circuit, flows into the second bypass circuit, and is discharged outside. Further, the processing liquid drained from the processing tank through the draining circuit flows from the draining circuit in the order of the circulation circuit and the second bypass circuit, and is drained to the outside. Also in this case, the processing liquid can be fed by a pump and drained. Thus, according to the first aspect, since the liquid is fed by the pump, it is possible to drain the processing liquid having a high viscosity in a short time as compared with the case where the liquid is drained by its own weight. In addition, since an existing pump provided in the circulation circuit is used, it is not necessary to provide a new pump for drainage.
[0010]
2. The processing apparatus according to claim 1, wherein, as described in claim 2, the other end of the second bypass circuit is connected to the drain circuit on the opposite side of the processing tank from the fifth valve. May be. In this case, the processing liquid that has flowed from the drain circuit into the circulation circuit is fed by the pump, and then flows again from the second bypass circuit into the drain circuit and is drained to the outside.
[0011]
The processing tank includes an inner tank that accommodates a substrate and an outer tank that receives the processing liquid overflowing from the inner tank, and one end of the drain circuit is connected to the outer tank . According to this configuration, the processing liquid in the outer tub is drained from the outer tub through the drain circuit.
[0012]
In addition, a sixth valve is provided in the drain circuit on the processing tank side with respect to the connection point between the drain circuit and the first bypass circuit, and a liquid that detects a lower limit position of the liquid level in the outer tank. A surface lower limit sensor is provided, and the sixth valve is configured to open and close based on detection of the liquid level lower limit sensor . According to such a configuration, first, the sixth valve is opened, and the processing liquid in the outer tank is drained from the outer tank through the drain circuit. Thereafter, when all of the processing liquid is drained from the outer tank and the outer tank is emptied, the liquid level lower limit sensor detects this, and the sixth valve is closed after a predetermined time has elapsed. As a result, air does not enter the pump from the drainage circuit, and the pump can be prevented from getting stuck.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view of a cleaning system 1 including a cleaning device 12 according to the present embodiment. The cleaning system 1 is configured to consistently perform the loading of the wafer W as a substrate in units of carriers C, the cleaning of the wafers W, the drying of the wafers W, and the unloading of the wafers W in units of carriers C. .
[0014]
In this cleaning system 1, the carry-in / out unit 2 performs an operation from loading the carrier C storing 25 wafers W before cleaning to shifting the wafer W to cleaning. That is, the carrier C placed on the carry-in portion 5 is transported, for example, two by two to the loader 7 by the transfer device 6, and the wafer W is taken out from the carrier C by the loader 7.
[0015]
The cleaning / drying processing unit 10 includes, in order from the loading / unloading unit 2 side, a wafer chuck cleaning / drying device 11 for cleaning and drying the wafer chuck 30a of the transfer device 30 that transfers the wafer W, various chemical solutions and pure water. The wafers W are cleaned by the cleaning devices 12 to 19 for cleaning the wafer W using a cleaning liquid such as the wafer chuck cleaning / drying device 20 for cleaning and drying the wafer chuck 33a of the transfer device 33, and the cleaning devices 12 to 19. A drying device 21 for drying the wafer W using, for example, isopropyl alcohol (IPA) vapor is arranged.
[0016]
In the wafer chuck cleaning / drying apparatuses 11 and 20, the wafer chuck 30a and the wafer chuck 33a are cleaned and dried using, for example, pure water. Further, in the cleaning / drying processing unit 10, the cleaning devices 12, 14, 16, and 18 are configured to perform chemical cleaning so that chemical cleaning and rinsing can be alternately performed according to a general cleaning process. , 15, 17, and 19 are configured to perform rinse cleaning. As an example, the cleaning apparatus 12 performs a cleaning process using SPM (mixed liquid of H ₂ SO ₄ / H ₂ O ₂ ), which is a cleaning liquid mainly composed of a sulfuric acid component and has a high viscosity, and Impurities such as organic contaminants adhering to the surface are removed. Further, in the cleaning device 16, for example, a cleaning process using APM (mixed solution of NH ₄ OH / H ₂ O ₂ / H ₂ O) which is a cleaning liquid mainly composed of an ammonia component is performed, and the surface adheres to the surface of the wafer W. Remove impurities such as organic contaminants and particles. Further, in the cleaning apparatuses 14 and 18, an oxidation formed on the surface of the wafer W by performing a cleaning process using DHF (HF / H ₂ O mixed liquid) which is a cleaning liquid mainly composed of a hydrofluoric acid component. Remove the film. In the cleaning devices 13, 15, 17, and 19, the wafer W is rinsed using pure water. Further, the drying device 20 is configured to dry the surface of the wafer W using IPA vapor.
[0017]
The above arrangement and combinations of the cleaning devices 12 to 19 can be arbitrarily combined depending on the type of cleaning processing for the wafer W. For example, a certain cleaning apparatus may be reduced, or conversely, a cleaning apparatus for cleaning the wafer W with another type of chemical may be added.
[0018]
The loading / unloading unit 50 loads the 25 wafers W cleaned and dried by the cleaning / drying processing unit 10 onto the carrier C and then unloads them in units of carriers C. That is, the carrier C in which the cleaned wafer W is accommodated by the unloader 51 is transported to the unloading section 52 by a transfer device (not shown).
[0019]
Next, the configuration of the cleaning device 12 according to the present embodiment will be described. The cleaning device 12 is configured so as to be able to smoothly drain even an SPM having a high viscosity. As shown in FIG. 2, the cleaning tank 60 provided in the cleaning apparatus 12 is composed of a box-shaped inner tank 61 and an outer tank 62 having a size sufficient to accommodate the wafer W. The outer tank 62 is mounted so as to surround the opening of the inner tank 61 so as to receive the SPM overflowed from the upper end of the inner tank 61.
[0020]
Below the inner tank 61, a megasonic device 64 incorporating an ultrasonic transducer is mounted via a water tank 63. The ultrasonic wave oscillated from the megasonic device 64 propagates through the water in the water tank 63 to the SPM in the inner tank 61, and has the effect of vibrating the SPM to remove particles adhering to the surface of the wafer W.
[0021]
A supply circuit 70 for supplying SPM from an SPM supply source (not shown) to the inner tank 61 is connected to the inner tank 61, and a drain circuit 71 for draining the SPM to a drain line of a factory, for example, is connected to the outer tank 62. The supply circuit 70 and the drain circuit 71 are connected by a circulation circuit 72. The pump 73 interposed in the circulation circuit 72 is configured to send the SPM in the circulation circuit 72 from the drain circuit 71 side to the supply circuit 70 side.
[0022]
Here, one end is connected to the supply circuit 70 at the cleaning tank 60 side from the connection point N1 between the supply circuit 70 and the circulation circuit 72, and the cleaning tank 60 side from the connection point N2 between the drain circuit 71 and the circulation circuit 72. , A first bypass circuit 74 is provided, the other end of which is connected to the drain circuit 71. The SPM discharged from the inner tank 61 through the supply circuit 70 can flow into the drain circuit 71 via the first bypass circuit 74. Further, a second detour in which one end is connected to the circulation circuit 72 on the downstream side of the pump 73 and the other end is connected to the drainage circuit 71 on the opposite side of the cleaning tank 60 from a fifth switching valve 84 described later. A circuit 75 is provided. Via this second bypass circuit 75, the SPM fed by the pump 73 can flow into the drain circuit 71 and drain into the drain line.
[0023]
The first bypass valve 74 is provided in the first bypass circuit 74, the second switch valve 81 is provided in the second bypass circuit 75, the connection point N1 of the supply circuit 70 and the circulation circuit 72, the supply circuit 70, the first A third switching valve 82 is provided in the supply circuit 70 between the connection point N3 of the bypass circuit 74 and the supply circuit 70 is located on the opposite side of the cleaning tank 60 from the connection point N1 of the supply circuit 70 and the circulation circuit 72. The fourth switching valve 83 is provided, and the fifth switching valve 84 described above is provided in the drainage circuit 71 on the opposite side of the cleaning tank 60 from the connection point N2 between the drainage circuit 71 and the circulation circuit 72. A sixth switching valve 85 is provided in the drainage circuit 71 on the cleaning tank 60 side of the connection point N4 between 71 and the first bypass circuit 74. These first switching valve 80, second switching valve 81, third switching valve 82, fourth switching valve 83, fifth switching valve 84, and sixth switching valve 85 are all electromagnetic (solenoid). This is a two-way valve of the type, and the switching of opening and closing is controlled by the supply of electric power from the power supply control mechanism 90. Accordingly, each circuit can select whether or not to flow SPM by conducting or blocking the flow path depending on the time.
[0024]
In addition to the pump 73, a damper 86, a heater 87, and a filter 88 are interposed in the circulation circuit 72 in order on the downstream side of the pump 73. During cleaning, the first switching valve 80, the second switching valve 81, the fourth switching valve 83, and the fifth switching valve 84 are closed, and the third switching valve 82 and the sixth switching valve 85 are opened. The SPM overflowed from the inner tank 61 to the outer tank 62 is supplied from the drain circuit 71 to the circulation circuit 72, and after the temperature is adjusted and purified by the circulation circuit 72, the SPM is supplied again to the inner tank 61 through the supply circuit 70. Yes.
[0025]
Further, the outer tank 62 includes a liquid level lower limit sensor 91 that detects a lower limit position of the liquid level of the SPM in the outer tank 62. This liquid level lower limit sensor 91 is mounted in the middle of a pipe line 92 that continuously feeds nitrogen (N ₂ ) gas to the outer tank 62, and indirectly measures the pressure of the N 2 gas, thereby measuring the inside of the outer tank 62. The lower limit position of the SPM liquid level is detected. The detection signal of the liquid level lower limit sensor 91 is output to the power supply control mechanism 90, and the sixth switching valve 85 is opened and closed by the power supply control mechanism 90 based on the detection of the liquid level lower limit sensor 91. Configured to do. When draining the SPM from the outer tank 62, the sixth switching valve 85 is opened, and when all the SPM is drained from the outer tank 62 and a predetermined time has elapsed, the sixth switching valve 85 is closed. It is.
[0026]
In addition, the cleaning devices 13 to 19 may be configured similarly to the cleaning device 12 so that the cleaning liquid in the tank can be smoothly drained using the pump 73.
[0027]
Next, the cleaning process performed by the cleaning apparatus 12 configured as described above will be described based on the cleaning process of the wafer W in the cleaning system 1 of FIG. First, a plurality of carriers C each containing, for example, 25 wafers W that have not been cleaned by a transfer robot (not shown) are placed on the carry-in section 5 of the carry-in / out section 2. Then, for example, 50 wafers W corresponding to 2 carriers C are taken out from the carrier C by the carry-in / out part 2, and the transfer device 30 holds the wafers W in units of 50 pieces. Then, the wafers W are sequentially transferred to the cleaning devices 12 to 19 while being attracted to the transfer devices 31, 32, and 33. In this way, cleaning for removing impurities such as particles adhering to the surface of the wafer W is performed.
[0028]
Here, processing in the cleaning apparatus 12 that performs chemical liquid cleaning using SPM (mixed liquid of H ₂ SO ₄ / H ₂ O ₂ ) that is a high-viscosity chemical liquid will be described. First, the first switching valve 80, the second switching valve 81, and the fifth switching valve 84 are closed, and the third switching valve 82 and the fourth switching valve 83 are opened. SPM is supplied from an SPM supply source (not shown) to the cleaning tank 60 through the supply circuit 70, and the cleaning tank 60 is filled with SPM in advance.
[0029]
Thereafter, 50 wafers W are collectively stored in the inner tank 61 by the transfer device 30 and chemical cleaning by SPM is started. As shown in FIG. 2, during the cleaning, the fourth switching valve 83 is closed and no new SPM is supplied from the supply circuit 70, while the SPM drained from the outer tank 62 through the drain circuit 71 is circulated. 72 and then circulated and supplied from the supply circuit 70 to the cleaning tank 60 by the operation of the pump 73. In the circulation circuit 72, the damper 86, the heater 87, and the filter 88 are flowed in this order to perform purification and temperature control, thereby reusing the SPM. In the inner tank 61, an upward flow of SPM is formed to uniformly clean the surface of the wafer W. Thus, since the SPM in the cleaning tank 60 is repeatedly used, the amount of consumption of SPM can be saved.
[0030]
After cleaning, the SPM is drained from the cleaning tank 60 and the cleaning tank 60 is emptied. At this time, the third switching valve 82, the fourth switching valve 83, and the fifth switching valve 84 are closed, while the first switching valve 80 and the second switching valve 81 are opened. Then, the SPM is drained from the cleaning tank 60 through the supply circuit 70 and the drain circuit 71. In this case, the SPM can flow from the supply circuit 70 to the first bypass circuit 74 and the circulation circuit 72 in order, and can be sent and discharged by the pump 73. FIG. 3 shows the state at this time.
[0031]
That is, the SPM discharged from the inner tank 61 through the supply circuit 70 flows from the supply circuit 70 into the first bypass circuit 74 because the third switching valve 82 is closed. The other end of the first bypass circuit 74 is connected to the drain circuit 71 closer to the cleaning tank 60 than the connection point N2 between the drain circuit 71 and the circulation circuit 72. The SPM flows from the drain circuit 71 into the circulation circuit 72. Then, the SPM is fed by the pump 73 in the circulation circuit 72 and flows into the second bypass circuit 75, then flows again into the drain circuit 71, and is drained to the factory drain line.
[0032]
The SPM discharged from the outer tank 62 through the drain circuit 71 flows from the drain circuit 71 to the circulation circuit 72 and the second bypass circuit 75 in this order, and is discharged from the inner tank 61. Similarly, the liquid is discharged to the drainage line. Also in this case, the SPM can be discharged by the pump 73 and discharged. Here, as shown in the figure, one end of the second bypass circuit 75 is connected to the circulation circuit 72 on the downstream side of the pump 73 and on the upstream side of the heater 87. Before the fluidity of the SPM fed by the pump 73 decreases due to the pressure drop caused by the heater 87 and the filter 88, the SPM can flow into the second bypass circuit 75 and drain from the drain circuit 71. Because.
[0033]
When all the SPM is drained from the outer tank 62 and the outer tank 62 is emptied, the liquid level lower limit sensor 91 detects this and outputs it to the power supply control mechanism 90. The power supply control mechanism 90 has passed a predetermined time. Later, the sixth switching valve 85 is closed. As a result, air does not enter the pump 73 from the drain circuit 71, and the pump 73 can be prevented from getting stuck.
[0034]
As described above, in the cleaning device 12 according to the present embodiment, since the liquid is fed by the pump 73, it is possible to drain the SPM having a high viscosity in a short time compared to the case where the liquid is drained by its own weight. For example, when the 34 liter capacity washing tank 60 is filled with SPM, if the discharge amount of the pump 73 is 15 liters / min, the drainage time is 2 minutes and the discharge amount of the pump 73 is 55. With liter / min, the drainage time can be less than 1 minute. In addition, since the existing pump 73 provided in the circulation circuit 72 is used, it is not necessary to provide a new pump for drainage.
[0035]
Thus, according to the cleaning device 12 of the present embodiment, the drainage is performed using the pump 73 of the circulation circuit 72, so that even a highly viscous SPM can be drained in a short time. Therefore, the processing time is also shortened, and it is possible to improve the throughput without placing an economical burden.
[0036]
The cleaning device 12 as described above is also effective for other high-viscosity cleaning liquids such as liquids containing phosphoric acid (H ₃ PO ₄ ) and chemical liquids such as ethylene glycol. Further, instead of connecting the other end of the first bypass circuit 74 to the drain circuit 71, the other end of the first bypass circuit 74 is connected to the circulation circuit 72 on the upstream side of the pump 73, and the first bypass circuit 74 is connected. The SPM in the circuit 74 may be directly supplied to the circulation circuit 72.
[0037]
The present invention is not limited to this embodiment, and can take various forms. For example, the present invention may be applied to a one-bath type (also referred to as one-tank multi-drug type) cleaning apparatus that uses a plurality of cleaning liquids in one cleaning tank. The substrate is not limited to the wafer W, and may be, for example, an LCD substrate, a CD substrate, a printed substrate, or a ceramic substrate.
[0038]
【The invention's effect】
According to the present invention , since the liquid is discharged using the pump of the circulation circuit, the processing liquid having a high viscosity can be discharged in a short time. Therefore, the processing time is also shortened, and it is possible to improve the throughput without placing an economical burden. In particular, it is possible to prevent the pump from getting stuck in the drainage.
[Brief description of the drawings]
FIG. 1 is a perspective view of a cleaning system including a cleaning device according to an embodiment.
FIG. 2 is an explanatory diagram showing a circuit system of the cleaning apparatus according to the present embodiment.
FIG. 3 is an explanatory view showing a state when SPM is drained in the cleaning apparatus of FIG. 2;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cleaning system 12 Cleaning apparatus 60 Cleaning tank 70 Supply circuit 71 Drain circuit 72 Circulation circuit 73 Pump 74 1st bypass circuit 75 2nd bypass circuit 80 1st switching valve 81 2nd switching valve 82 3rd switching Valve 83 Fourth switching valve 84 Fifth switching valve 85 Sixth switching valve 91 Liquid level lower limit sensor

Claims

A supply circuit for supplying a processing liquid to a processing tank containing a substrate, a drain circuit for draining the processing liquid from the processing tank, a circulation circuit connecting between the supply circuit and the drain circuit, In a processing apparatus including a pump and a filter that are interposed in a circulation circuit and send processing liquid from the drain circuit side to the supply circuit side,
One end is connected to the supply circuit on the treatment tank side from the connection point between the supply circuit and the circulation circuit, and the drain circuit is connected to the treatment tank side from the connection point between the drain circuit and the circulation circuit. A first bypass circuit having the other end connected or the other end connected to the circulation circuit upstream of the pump;
A second bypass circuit having one end connected to the circulation circuit downstream of the pump and upstream of the filter ;
A first valve is provided in the first bypass circuit, a second valve is provided in the second bypass circuit, a connection point between the supply circuit and the circulation circuit, the supply circuit, and the first bypass circuit. A third valve is provided in the supply circuit between the connection point and a fourth valve is provided in the supply circuit on the opposite side of the processing tank from the connection point between the supply circuit and the circulation circuit, A fifth valve is provided in the drain circuit on the opposite side of the treatment tank from the connection point of the circuit and the circulation circuit;
The processing tank includes an inner tank for storing a substrate and an outer tank for receiving a processing liquid overflowing from the inner tank, and one end of the drainage circuit is connected to the outer tank,
A liquid level lower limit for detecting a lower limit position of the liquid level in the outer tank while providing a sixth valve in the drain circuit on the processing tank side of the connection point between the drain circuit and the first bypass circuit. A sensor,
When the processing liquid is discharged from the processing tank, the first, second, and sixth valves are opened, and the liquid is discharged by the pump.
The processing apparatus, wherein when the outer tub becomes empty, the liquid level lower limit sensor detects this and the sixth switching valve is closed .

2. The processing apparatus according to claim 1, wherein the other end of the second bypass circuit is connected to the drain circuit on the opposite side of the processing tank from the fifth valve.