JP4431203B2 - Ferric chloride etchant management system - Google Patents

Description

【００１７】
上に示す様に４時間経過した結果は、図１に示すように酸化体濃度と還元体濃度の変化は略直線であり、又、酸化体と還元体の和から銅溶解量を引くと略エッチング新液（銅を溶解する前の塩化第二鉄液）のモル（Ｍ）数になる。従って塩化第二鉄と銅のエッチング反応では、反応式１しか起こらない。
【００１８】
したがって塩化第二鉄液によるエッチングにおいては実際のエッチングは反応式１の状態、すなわち塩化第一銅が第二銅に実質的に酸化されない状態で行われていたことになり、場合によっては必ずしも適正なエッチングが行われていなかった懸念がある。またエッチング液の再生についても従来は前記のように塩酸の供給によってエッチング速度をある程度回復させる等の手段をとる以外には特にこの理論にもとづく再生処理は行われておらず、比較的短い使用時間でエッチング液は劣化したものとみなされて新液と交換されていた。
【００１９】
塩化第二鉄液による銅のエッチングの場合、エッチング工程中において適時塩化第一鉄および塩化第一銅を酸化することにより、酸化力のある塩化第二鉄および塩化第二銅が共存する液組成によってエッチングが行われることになり、かゝる再生処理によりエッチング液の可使時間が著しく増大することになる。この結果廃液の排出量が大幅に減少して省資源および環境保護に寄与し得るものと考えられる。
【００２０】
【課題を解決するための手段】
本発明においてはかゝる再生処理は塩化第二鉄溶液による銅のエッチングにおいてエッチングによって生じる塩化第一鉄および塩化第一銅を順次酸化してエッチング液を再生する塩化第二鉄エッチング液の管理装置により達成される。
【００２４】
塩化第二鉄溶液による銅のエッチングにおいてエッチングによって生じる塩化第一鉄および塩化第一銅を酸化してエッチング液を再生する形式の塩化第二鉄エッチング液の管理装置において、
塩化第二鉄溶液を含むエッチング槽と、前記エッチング槽に循環路を介して接続された再生槽と、前記再生槽に接続された過酸化水素貯槽と、塩酸貯槽と、前記再生槽に設けた塩酸濃度測定用の滴定分析方式による塩酸分析装置およびｐＨ計と、塩化第一鉄および塩化第二鉄濃度測定用の滴定分析方式による塩化第二鉄および塩化第一鉄分析装置および酸化還元電位計と、
前記塩酸分析装置およびｐＨ計からの夫々の塩酸濃度の測定値を入力演算し、演算結果を前記塩酸貯槽に出力して塩酸の補給量を制御し、かつ前記塩化第一鉄および塩化第二鉄の分析装置および前記酸化還元電位計からの夫々の第一塩化鉄および塩化第二鉄濃度の測定値を入力演算し、演算結果を前記過酸化水素貯槽に出力して過酸化水素の補給量を制御するコンピュータとを備えた塩化第二鉄エッチング液の管理装置（請求項１）。
【００２６】
塩化第二鉄エッチング液による金属、たとえば銅のエッチングにおけるエッチング液の再生処理の為の塩化第一銅の実用的な酸化手段としては電解酸化、酸化剤による酸化又はいわゆる空気酸化等が考えられる。
【００２７】
隔膜電解法による塩化第二鉄エッチング液の再生装置
電解酸化法としてはたとえば公知の陰イオン交換膜を用いた隔膜電解法を利用することができ、陰イオン交換膜で仕切られた陰極槽と陽極槽との間に電解電圧を印加することによりイオン交換膜を通してイオンを選択的に槽間に移動させることにより電解（酸化）が行なわれる。
【００２８】
図２は前記隔膜電解法を利用してエッチング液の酸化再生処理を行うようになされた塩化第二鉄エッチング溶液の管理方法を実施する装置の概要を示す。図中、中央に示すエッチング液の再生槽では、再生処理用薬液としての塩酸が塩酸電解液の貯槽から補給される陰極槽と、エッチング槽からの老化した塩化第二鉄エッチング液が循環ポンプを介して循環される陽極室とが陰イオン交換膜によって仕切られている。陽／陰極には電解槽電源からの電圧が増幅器を介して印加されている。エッチング槽には塩酸分析計、陽極側には塩素発生検出センサが設けられ、陰極側には塩酸濃度を検出する電磁誘導式の電導度センサおよび液面センサ等が設けられている。
【００２９】
電解中には、陰極槽から交換膜を通してＣｌ⁻が陽極槽に移動して、
Ｆｅ^２＋ − ｅ⁻ → Ｆｅ^３＋
Ｃｕ^＋ − ｅ⁻ → Ｃｕ^２＋
の反応によって酸化され塩化第二鉄と塩化第二銅が生成する。陰極では水素イオンがＨ_２となり水素ガスが発生する。２価鉄、１価銅が全部酸化されると、陽極からＣｌ_２ガスが発生する。陽極槽の鉄イオン、銅イオンは交換膜に阻止され、陰極槽には移動しない。陰極槽から陽極槽に浸透圧の効果で若干の水が移動する。
【００３０】
電解すると陰極槽の塩酸濃度は低下する。塩酸濃度を一定に保つため、電磁式の電導度コントローラを用いて塩酸濃度制御計によって陰極液より高い濃度の塩酸を自動補給し濃度を一定に保つ。
【００３１】
エッチング槽では、エッチングにより塩酸濃度が低する。、また、電解するとプロトンが陽極槽から陰極槽に移動するため、陽極槽の水素イオンが減少し、ｐＨが上昇する。そのため、塩酸分析計で塩酸濃度を測定し、一定濃度を保つ様、陰極槽液（塩酸電解液）をエッチング槽に自動補給する。この補給により、陰極槽液量が不足した場合には液面センサーで検出し、塩酸電解液を規定レベルまで補給する。陰極槽の塩酸をエッチング液の塩酸補給液に利用すると、陰極槽の塩酸が無駄にならず、また、新しい塩酸が陰極槽に補給されるため、塩酸は不純物の少ない新しい状態を保つことができる。
【００３２】
電解電源をＯＦＦにすると、僅かな銅や鉄イオンが陽極槽側から交換膜を通して陰極槽に混入する。陰極槽に入った銅イオンは陰極で還元され金属銅になり、陰極に析出する。析出した銅は水素ガス泡等で剥離し、スカム状で陰極槽の沈殿又は分散又は浮上する。フィルターを陰極槽に付けることによって金属銅を除去することができかつ陰極液をきれいに保つことができる。
【００３３】
陽極槽では、塩素による酸化が終わると塩素ガスが陽極から発生する。従来の電解装置ではＯＲＰ電極を使用し、酸化還元電位から再生の終点を検出し電源を制御していた。しかし、ＯＲＰ電極はＫＣｌの定期的補給や比較電極の劣化で必ず寿命があるため、定期的な交換等のメンテナンスが必要となる。簡便な手段として、白金センサー又はカーボンセンサーと陽極との電位差を測定するだけで再生反応の終点を検出することができ、この方法によればセンサーのメンテナンスの必要が無くなる。
【００３４】
【発明の実施態様】
酸化剤注入による塩化第二鉄エッチング液の再生装置
本発明による塩化第二鉄エッチング液の再生処理は、酸化剤として過酸化水素を用いる塩化第一鉄および塩化第一銅の第二鉄および第二銅への酸化である。一般にこのような再生処理に用いる酸化剤としては、塩素ガス、オゾン、塩素酸塩（塩素酸ナトリウム、同カリウム、同ナトリウム）、次亜塩素酸塩（次亜塩素酸ナトリウム、同カリウム）、過酸化水素、過塩素酸等がある。各酸化剤の反応を下記に示す。
【００３５】
▲１▼ 塩素ガスの再生反応
2FeCl₂ + Cl2 → 2FeCl₃
Cu₂Cl₂ + Cl2 → 2CuCl₂
▲２▼ オゾンの再生反応
2FeCl₂ + O₃ + 2HCl → 2FeCl₃ + H₂O + O₂↑
Cu₂Cl₂ + O₃ + 2HCl → 2CuCl₂ + H₂O + O₂↑
▲３▼ 過酸化水素の再生反応
2FeCl₂ + H₂O₂ + 2HCl → 2FeCl₃ + 2H₂O
Cu₂Cl₂ + H₂O₂ + 2HCl → 2CuCl₂ + 2H₂O
▲４▼ 塩素酸塩の再生反応
6FeCl₂ + NaClO₃ + 6HCl → 6FeCl₃ + NaCl + 3H₂O
3Cu₂Cl₂ + NaClO₃ + HCl → 6CuCl₂ + NaCl + 3H₂O
▲５▼ 次亜塩素酸塩の再生反応
2FeCl₂ + NaClO + 2HCl → 2FeCl₃ + NaCl + H₂O
Cu₂Cl₂ + NaClO + 2HCl → 2CuCl₂ + NaCl + H₂O
【００３６】
これらの中、塩素ガスは日本では保安面で既得権事業所以外使用は殆ど不可能である。オゾンは比較的安全であるが、オゾン発生装置を必要とする。過塩素酸による再生は、反応速度が遅く、また危険物であってその使用は好ましくない。塩素酸塩や次亜塩素酸塩は添加すると、ナトリウム塩等がエッチング液に多量に混入するため、エッチング品位に影響する。
【００３７】
過酸化水素は鉄との反応が非常に過激なため、塩化第二鉄エッチング液への使用に当たっては注入方法や反応温度の監視制御等、保安面に注意が必要であるが反応により塩を生成しないので極めて有効であり、本発明では酸化剤として過酸化水素を用いる。
【００３８】
銅エッチングでは、エッチングにより生成された第一銅はエッチングに寄与しない。再生すると、第一鉄は第二鉄になり、第一銅は第二銅になる。再生された、第二鉄はもとより、第二銅も銅をエッチングする。このため、再生を続けると、鉄濃度は相対的に低下して第二銅濃度が増加し、最終的には第二鉄ではなく第二銅だけのエッチングになる。一般に塩化第二銅エッチングより塩化第二鉄のほうが切れが良いといわれており、このため、再生し比重が低下した場合や、酸化剤を補給するときに一定の比率で新液の補給が必要となる。
【００３９】
塩化第二鉄エッチング液は、塩化第二鉄液中に塩酸を０．２〜１％位存在させて使用される。これは、加温やドラフトによる塩酸飛散でエッチング液のｐＨが上昇し、水酸化鉄のスラッジが発生して基板面に付着したり、パイプ等を詰まらせたりすることを防ぐためである。ただし、塩酸濃度が高いとオーバーエッチングやエッチング品位の低下を生じるため、その補給量を何らかの方法で常に一定範囲内に維持する様に測定制御しなければならない。また酸化剤による再生では、前記再生反応にみられるように、多くの場合必ず塩酸を必要とし、再生を行う場合その測定制御も不可欠である。
【００４０】
図３は酸化剤として過酸化水素を用いて再生処理を行うようになされた本発明に係る塩化第二鉄エッチング液の管理方法を実施する装置の説明図である。図３に示す装置は塩化第二鉄エッチング液による銅のエッチング装置、前記エッチング装置に対してエッチング液循環ポンプを介して接続されたエッチング液の再生槽、およびこの再生槽に対して酸化剤としての過酸化水素および塩酸を供給するための酸化剤貯槽および塩酸貯槽ならびに必要に応じて塩化第二鉄新液を再生槽に補給するための塩化第二鉄新液貯槽からなる。再生槽には、ＯＲＰ調節計、ｐＨ調節計、比重調節計、温度計、冷却装置、攪拌機が設置されている。
【００４１】
ＯＲＰ計：
エッチングが進行すると、ＯＲＰ計の指示値は下がる。例として白金電極とそれに対する電極として銀／塩化銀参照電極を用いた場合、指示値は液温度５０℃の新液で７００ｍＶ〜８００ｍＶであり、塩化第二鉄新液の濃度の１／４Ｍの銅をエッチングすると約５５０ｍＶ〜４５０ｍＶに低下する。このＯＲＰ計により、指示値が予め設定されたＯＲＰｍＶ値を下回ると、酸化剤としての過酸化水素が注入され設定値以上になると注入が停止される。
【００４２】
ｐＨ計：
酸化剤が注入されると、ｐＨが上昇する。これをｐＨ計で測定し、予め設定されたｐＨを上回ると塩酸を注入し、予め設定されたｐＨを以下になると注入を停止する。例として、塩化第二鉄新液のｐＨは約−０．５〜１であり、酸化剤を注入すると、ｐＨは急激に上昇する。
【００４３】
比重計：
エッチングが進行すると、エッチング液の比重は上昇する（たとえば新液比重１．３８０の場合、新液の１／４Ｍの銅をエッチングすると１．４００に上昇する）。しかし、再生を行うと、再生液（酸化剤、塩酸）はエッチング液より遥かに比重が低いため比重は低下傾向となる。一定比重を確保するため、エッチング新液を比重計の検出出力に応じて自動補給する。
【００４４】
温度計、冷却器：
再生反応では反応熱が発生する。特に、過酸化水素を使用した場合、温度上昇は急激に起り、このため温度計による再生槽の温度管理が必要となる。予め上限温度を設定しておき、設定値を上回った場合温度計からの出力で酸化剤の注入を強制的に停止させる。さらに温度上昇が起った場合を想定して上限警報も必要となる。再生槽に冷却器を設け、再生反応で温度が上昇した場合冷却により温度上昇を防止する。
【００４５】
塩酸分析装置：
本発明の再生処理においては応答速度を考慮してオンタイムの塩酸濃度をｐＨ計で行っているが、ｐＨ計では０．２〜１％の高い塩酸濃度の正確な管理は困難である。このため、図４に示す塩酸分析計（塩酸分析装置）を用いて定期的に塩酸濃度を分析する（所要時間約１０分）。この分析装置からの出力で直接塩酸貯槽からの供給量を制御することができるが、こゝではその出力をｐＨ計の測定値の校正に用いてその精度を確保する。
【００４６】
図４中、試料重量測定用のロードセルと組合せた塩酸濃度の分析試料（エッチング液）を入れる分析セルに対して試料注入用の弁ＳＶ１、滴定液および隠蔽液等の注入用の弁ＳＶ３〜ＳＶ５およびｐＨ電極が設けられている。
【００４７】
測定方法
▲１▼ ２５％しゅう酸カリウム溶液、０．０５％しゅう酸溶液をポンプＰ４、Ｐ５から弁ＳＶ４、ＳＶ５を介して分析セルに注入し、所定のｐＨ６〜６．２に自動調節してその値をコンピュ−タＣＰＵに記憶する。
▲２▼ エッチング液試料をポンプＰ１から弁ＳＶ１を介して注入し、含有される塩酸によって低下したセル内のｐＨを０．１ＮＮａＯＨ溶液をＳＶ３から滴下させることによって前記の記憶値となるように滴定し、この滴定値にもとづいて試料中の塩酸濃度をコンピュータＣＰＵで演算する。
▲３▼ 演算値が所定の塩酸目標濃度を下回るとＣＰＵで補給量を演算して演算補給出力信号又はｐＨ計の校正信号を出力する。
【００４８】
塩化第一鉄および第二鉄分析計
エッチング液中に若干の還元物質を残存させる方が良質のエッチングのために好ましいことが知られ、そのためにたとえば塩化第一鉄および第二鉄の濃度を所定の値に制御することが必要である。本発明の再生処理においては、応答性の点でＯＲＰセンサを用いているがその精度、安定度が充分でないため、図５に示す塩化第一鉄および第二鉄分析装置を用いて定期的に濃度を絶対値で測定し、それに基く演算値によってＯＲＰの設定値等を設定する。
【００４９】
この分析装置の基本的な構成は図４に示す塩酸分析装置と同様であり、ロードセルで測定した試料重量を基準とした滴定によって絶対値としての濃度を得るようになされており、こゝでは、分析セルに対して測定試料や、過マンガン酸カリウム滴定液、三塩化チタン滴定液および希硫酸等の注入弁ＳＶ１〜ＳＶ６が設けられている。
【００５０】
図５の塩化第一鉄／第二鉄分析計では酸化物質としての塩化第二鉄および塩化第二銅ならびに還元物質として塩化第一鉄および塩化第一銅分析される。分析方法は公知の還元滴定および酸化滴定法に準じて行われ、分析計の動作は基本的には図４の塩酸分析計の場合と同様である。
【００５１】
酸化剤センサ：
図３に示す再生装置の再生槽では酸化剤（過酸化水素）センサとしてＯＲＰ計を用いているが、これに代えて酸化剤注入ノズル内部に一本の貴金属線（ＰｔやＡｕ）、再生槽内（酸化剤注入ノズル近傍）に一本の貴金属線（ＰｔやＡｕ）を設置して、両貴金属線間の電位差を測定すると、図６に示す電位測定ができ、酸化剤の制御に使用することができる。このセンサーは単純な構造なので、メンテナンスが全く不要であり、再生反応の実質的な終点はこのセンサーで確認できる。
【００５２】
酸化剤注入ノズル：
過酸化水素を酸化剤として使用する場合、塩化第二鉄液との反応は過激で危険な突沸状態を生じるおそれがあるので出来るだけ少量の過酸化水素を時間をかけて注入する。ポンプから直接配管を通して液中に注入すると、たとえチェック弁を介していてもチェック弁が故障すると、サイホン現象で酸化剤が鉄液中に流れ込んでしまうか、逆流して酸化剤槽の鉄液が入り爆発的な状態となる。このため、過酸化水素は図７の左側に示すように、液から物理的に離しなければならないが、滴下すると鉄液表面で過激に反応し、ここで突沸状態を生じて周囲に飛散する．このため、注入場所は必ず吸気ダクト等で陰圧状態にしておかなければならない
【００５３】
本発明の実施態様においては、図７の右側に示すように酸化剤の注入ノズルにスリットが設けられている。ノズル先端が液中に浸漬されていても反応による圧力がスリットから逃げ、また鉄液はスリットでサイホンカットされるため、チェック弁が故障しても逆流は生じない。酸化剤槽又は酸化剤テンポラリー槽の液面は再生槽液面より低い位置とする。
【００５４】
塩化第二鉄エッチング液の気体酸化処理
塩化第二鉄エッチング液の酸化再生処理には、比較的長時間を有するがいわゆる空気酸化を利用することもできる。酸化に用いる気体としては酸素を含む気体、たとえば空気、又はオゾンを含む気体等が用いられる。
【００５５】
図８には気体酸化による塩化第二鉄エッチング液の再生処理に用いる装置の概要を示す。図８の装置では塩化第二鉄エッチング装置に対してエッチング液循環ポンプを介して再生装置の液留まり部が接続されており、この液留まり部には塩酸貯槽および新液貯槽が夫々の補給ポンプを介して接続されている。また液留まり部には塩酸分析計、塩化第一／第二鉄および塩化第一／第二銅の濃度を検出するＦｅ^２＋／Ｆｅ^３＋分析計およびエッチング工程の進行、気体酸化処理に伴うエッチング液の比重の変化（増大）を検出制御する比重計が設けられている。
【００５６】
酸素もしくはオゾン発生器からの酸化性気体を混合器を通して循環供給するための気体循環ブロア−が前記液留まり部の底部のバブリング装置に接続されている。バブリング装置からの気／液混合体は再生装置の循環ポンプによって装置上方のスプレー部からカラムに均一に噴霧されて気／液接触による酸化を行い液留まり部に流下する。その他図中、スプレーの上方には接触後の気体を装置外のスクラバに放出する際のミスト漏れ防止フィルタが設けられている。
【００５７】
塩酸分析計：
気体とエッチング液の酸化の反応は緩慢なので、塩酸濃度制御は前記塩酸分析計で行い、予め設定された塩酸濃度を下回ると塩酸貯槽から酸補給ポンプで塩酸を補給する。
【００５８】
比重計：
エッチング液を霧状にする為、水の蒸発が起り比重は上昇する傾向にある。またエッチングによっても比重は上昇する。このため、比重がエッチング液より十分低い塩化第二鉄新液を比重計によって適量補給する。
【００５９】
Ｆｅ^２＋／Ｆｅ^３＋分析計：
予め設定された比率以上に第二鉄濃度が上昇すると再生装置を停止させたり、比重計によって新液が正しく補給されている（第二鉄と第一鉄の比が或る範囲内に確保されている）かどうかを監視する機能を有する。
【００６０】
気体循環ブロアー：
再生装置内部の気体の有効利用するため、および液溜り部のエッチング液をバブリングさせるため、再生装置内に気体を循環させる。
【００６１】
図示の装置ではエッチング装置の第二塩化鉄エッニング溶液は液留まり部を通して常時循環され、エッチング中に塩酸濃度が設定値を下回ると、塩酸分析計によって塩酸貯槽から所定量の塩酸が補給される。
【００６２】
気体循環ブロアは常時作動されて気体混合器を通して発生器からの空気又は酸素等を液留まり部のバブリング装置に送る。これによって生成された気泡混合再生液は再生装置の循環ポンプで上方に圧送されてスプレー部から噴霧されカラムに均一に散布されて完全な気／液接触が行われ、それによって再生液中の塩化第一鉄や塩化第一銅が第二鉄および第二銅にそれぞれ酸化される。
【００６３】
再生処理が完了してＦｅ^２＋／Ｆｅ^３＋分析計によって塩化第二鉄（および塩化第二銅）濃度の所定値以上の上昇が検出されると、その信号で再生液の循環が停止される。またエッチング液のスプレ−による水分装置やエッチングの進行によりエッチング液の比重が増大すると比重計がこれを検知してエッチング新液を新液貯槽から液留まり部に補給する。
【００６４】
以上本発明を図に示す塩化第二鉄エッチング溶液による銅のエッチングに用いる液管理装置について説明したが、本発明は銅のエッチングに限らず鉄その他の金属のエッチングにも用いられる。またＯＲＰセンサ、電位差センサおよび塩酸分析計、塩化第二鉄／第一鉄分析計としては図示の例の他これと等価な種々の検出手段を用いることができる。
【００６５】
【発明の効果】
以上のように本発明によれば、塩化第二鉄エッチング液による銅のエッチングに際してエッチング過程で生じる塩化第一鉄および塩化第一銅を適時又は常時塩化第二鉄および塩化第二銅に酸化することによりエッチング液が再生されて高いエッチング能力を維持し、長時間にわたってワ−クを効果的にエッチング処理することができる。これによって新液交換の頻度が減少しかつ排液量も少なくなるので省資源および環境保護の上からも有効である。
【図面の簡単な説明】
【図１】 塩化第二鉄エッチング液中の銅溶解度に対する酸化物質および還元物質の濃度変化の傾向を示すグラフである。
【図２】 電解酸化により再生処理を行う塩化第二鉄エッチング液の管理装置の概要を示す図である。
【図３】 酸化剤酸化により再生処理を行う本発明による塩化第二鉄エッチング液の管理装置の概要を示す図である。
【図４】 本発明によるエッチング液管理装置に用いる塩酸濃度分析装置の概要を示す図である。
【図５】 本発明によるエッチング液管理装置に用いる塩化第一鉄／第二鉄分析計の概要を示す図である。
【図６】 本発明によるエッチング液管理装置に用いる酸化剤センサの特性を示すずである。
【図７】 本発明によるエッチング液管理装置に用いる酸化剤注入ノズルの概要を示す図である。
【図８】 気体酸化により再生処理を行う塩化第二鉄エッチング液の管理装置の概要を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a copper etching technique using a ferric chloride solution, and more particularly, etching for regenerating an etching solution by appropriately or constantly oxidizing ferrous chloride and cuprous chloride generated in the course of such etching. The present invention relates to a solution management method and apparatus.
[0002]
[Background Art and Problems to be Solved by the Invention]
In the etching process of a metal such as copper with a ferric chloride solution, copper is conventionally oxidized by ferric chloride ions to become cuprous chloride as shown in the following reaction formulas 1, 2, and 3. Copper is further oxidized in the solution to cupric chloride.
[0003]
FeCl_Three + Cu → FeCl₂ + CuCl ………… 1
In the first reaction, ferric chloride and copper react to produce ferrous chloride and cuprous chloride. The reaction goes further:
FeCl_Three + CuCl → FeCl₂ + CuCl₂ ……… 2
Cu⁺ Fe³⁺ Oxidized by Cu²⁺ Is generated. To summarize etching reactions 1 and 2:
2FeCl_Three + Cu → 2FeCl₂ + CuCl₂ ……… 3
That is, 2M ferric chloride is required to etch 1M copper, and 2M ferrous chloride and 1M cupric chloride are formed.
[0004]
As the copper concentration in the solution increases with the progress of etching, the etching rate decreases and the etching time becomes longer. Conventionally, HCl is added to increase the solubility of copper, or a new solution is partially replenished, etc. In any case, the etching solution is usually replaced with a new solution at an appropriate time after the degree of aging is judged on the basis of a decrease in the etching rate or the appearance of the solution.
[0005]
The present inventor often experiences an event indicating that the reaction in etching copper with ferric chloride does not necessarily proceed as shown in the above reaction formulas 1-2 during the etching process. That is, cuprous chloride produced by reaction formula 1 is not easily oxidized, and cupric chloride according to reaction formula 2 is not produced. This can be confirmed, for example, by analyzing the etching solution by the iodine method.
[0006]
Reaction of iodine method:
Fe³⁺ Is masked with ammonium hydrogen fluoride. Now Fe⁺³ Is irrelevant. When KI is added:
Fe²⁺ + KI → FeI₂ ……… 4
And
2Cu²⁺ + 4KI → 2CuI + I₂ ……… 5
To release iodine.
Cu⁺ + KI → CuI ……… 6
It becomes.
[0007]
In the reactions of Formula 4 and Formula 6, no iodine release occurs. Therefore, the iodine method (a typical method of divalent copper analysis, adding a buffer solution to a solution containing divalent copper to pH 4 position, adding potassium iodide, and titrating free iodine with Na thiosulfate) Cu in the etching solution²⁺ Only the concentration measurement becomes possible.
[0008]
2M-FeCl_ThreeAnd 0.1M-CuCl₂ When the solution containing (Solution 1) is analyzed by the iodine method, 0.1M copper is correctly measured.
When 0.1M metallic copper is further dissolved in Solution 1 and analyzed by the iodine method, 0.2M Cu is obtained based on Reaction Formula 3.²⁺Should be measured, but in fact Cu lower than 0.1M²⁺Is measured. This means that the added copper metal is Fe³⁺ Cu dissolves at the same time²⁺ In both cases, the following reactions are considered to occur.
FeCl_Three + Cu → FeCl₂ + CuCl and CuCl₂ + Cu → 2CuCl reaction.
In addition, after adding hydrogen peroxide to the solution 1 and leaving it to stand sufficiently, Cu is measured to be 0.1M when measured by the iodine method. This is Fe³⁺ And Cu²⁺ It shows that no reaction occurs even if hydrogen peroxide is added to the solution.
[0009]
2M-FeCl_ThreeAnd 0.1M-CuCl₂Hydrogen peroxide was added to a solution (solution 2) in which 0.1 M metallic copper was dissolved in the solution, and 0.2 M copper was measured by measuring with the iodine method.
2FeCl₂ + H₂O₂ + 2HCl → 2FeCl_Three+ 2H₂O
Cu₂Cl₂ + H₂O₂ + 2HCl → 2CuCl₂+ 2H₂O
In Solution 2, the copper metal is Cu²⁺ And Fe³⁺ Cu dissolved and produced by⁺ Is oxidized with hydrogen peroxide and Cu²⁺ Means that
The reaction of reaction formula 2 is considered to be very slow.²⁺ Was not measurable and was almost the same value as described above. Also, in anticipation of air oxidation, the solution 2 was aerated for 12 hours.²⁺ Was not detected.
[0010]
The above-mentioned verification by the elementary method alone is not sufficient, and another method shown below is used for Cu.²⁺Was confirmed.
[0011]
Fe³⁺ The hydroxide of 10 at pH 4.1 or higher^-FiveSolubility is less than M, redissolves at pH 14 and above, Fe²⁺ The hydroxide is 10 at pH 9.7 and above^-FiveSolubility is below M and redissolves at pH 13.5 and above. For this reason, when ammonia water is added to the etching solution, the pH becomes around 10, iron precipitates as hydroxide, copper dissolves in ammonia water as ammonia complex salt, Cu²⁺ In the case of blue, Cu⁺In case of, it becomes transparent (no color development). The monovalent copper ammonium complex is easily oxidized by air to become divalent and exhibits a blue color. For this reason, after adding ammonia, the beaker was covered to prevent air oxidation as much as possible.
[0012]
3M-FeCl_ThreeCopper 0.75M was dissolved in the etching solution, and after adding ammonia water and allowing to stand, the color of the supernatant was almost transparent. In addition, air was bubbled through the liquid for 10 hours, and after adding ammonia water and allowing to stand, the color of the supernatant liquid was almost transparent. By the way, after oxidation with hydrogen peroxide, ammonia water was added and the color of the supernatant liquid after standing still showed a deep blue color. The supernatant liquid after adding ammonia water and allowing it to stand still gradually turns light blue because there is air on the liquid even if it is covered to prevent air oxidation. But from the beginning Cu²⁺When blue water is present, the blue color becomes blue when ammonia water is added, and the supernatant liquid during standing is dark blue from the beginning.
[0013]
(1) 2M-FeCl₃And 0.1M-CuCl₂The solution 1 containing ammonium hydrogen fluoride (NH₄As soon as (F · HF) was added, the supernatant liquid exhibited a blue color peculiar to copper.
(2) On the other hand, 4M-FeCl₃A sufficient amount of ammonium hydrogen fluoride (NH) in a solution obtained by dissolving 0.66M, 0.8M, 1M, 1.33M, and 2M of copper in the ferrous chloride etching solution.₄The supernatant liquid is transparent even if F.HF is added, and CuCl₂Existence was not confirmed.
(3) The liquid obtained in the above (2) gradually exhibited a slight blue color on the liquid surface (contact surface) after several hours.
(4) Similarly, when the liquid obtained in (2) was forcibly ventilated, a blue color peculiar to copper was exhibited within a few minutes.
Iodine was liberated when potassium iodide was added to the blue liquids of (1), (3), and (4).
[0014]
Even in this verification, it was confirmed that copper etching with a ferric chloride solution hardly generated divalent copper in a normal etching state. In the experiments (3) and (4) above, ammonium hydrogen fluoride (NH₄After concealing iron with (F · HF), copper is easily oxidized, and it is presumed that divalent or trivalent iron hinders the oxidation of copper.
[0015]
The etching reaction between ferric chloride and copper was quantitatively verified.
Test method:
200 cc each of 4M ferric chloride solution (oxide mass 3.949M) was taken in 5 beakers, and different amounts of copper were dissolved.
The oxidizing substance and reducing substance concentrations after 4 hours were measured in a constant temperature water bath (50 ° C. ± 0.1 ° C.).
Oxidized substance measurement method: 3 ml of a sample was taken, 20 ml of 10% hydrochloric acid was added, and titrated with titanium trichloride. End point detection: ORP meter.
Reducing substance measurement method: 3 ml of a sample was taken, 20 ml of Reinhardt's solution was added, and titrated with potassium permanganate. End point detection: visual inspection.
[0016]
Measurement result:
Reaction temperature 50 ° C .: Reaction time 4 hours

[0017]
As shown in the above, the results after 4 hours have shown that the changes in the oxidant concentration and the reductant concentration are substantially linear as shown in FIG. It becomes the number of moles (M) of the new etching solution (ferric chloride solution before dissolving copper). Therefore, only the reaction formula 1 occurs in the etching reaction between ferric chloride and copper.
[0018]
Therefore, in the etching with a ferric chloride solution, the actual etching was performed in the state of reaction formula 1, that is, the state in which cuprous chloride was not substantially oxidized to cupric. There is a concern that the etching was not performed. Also, with respect to the regeneration of the etching solution, a regeneration process based on this theory has not been carried out except for measures such as recovering the etching rate to some extent by supplying hydrochloric acid as described above. Thus, the etching solution was regarded as deteriorated and replaced with a new solution.
[0019]
In the case of etching copper with ferric chloride solution, liquid composition in which ferric chloride and cupric chloride with oxidizing power coexist by oxidizing ferrous chloride and cuprous chloride timely during the etching process Etching is performed by this, and the usable time of the etching solution is remarkably increased by such a regeneration process. As a result, it is considered that the amount of discharged waste liquid can be greatly reduced, contributing to resource saving and environmental protection.
[0020]
[Means for solving the problem]
  In the present invention, such reproduction processing isA ferric chloride etchant management device that sequentially oxidizes ferrous chloride and cuprous chloride generated by etching in etching copper with a ferric chloride solution to regenerate the etchantIs achieved.
[0024]
  In the ferric chloride etchant management device of the type that oxidizes ferrous chloride and cuprous chloride generated by etching in etching copper with a ferric chloride solution to regenerate the etchant,
  An etching tank containing a ferric chloride solution, a regeneration tank connected to the etching tank via a circulation path, a hydrogen peroxide storage tank connected to the regeneration tank, a hydrochloric acid storage tank, and the regeneration tank Hydrochloric acid analyzer by titration analysis method for hydrochloric acid concentration measurementAnd a pH meter, a ferric chloride and ferrous chloride analyzer and a redox potentiometer by a titration analysis method for measuring ferrous chloride and ferric chloride concentrations,
Calculating each hydrochloric acid concentration measurement value from the hydrochloric acid analyzer and pH meter, inputting the calculation result to the hydrochloric acid storage tank to control the replenishment amount of hydrochloric acid, and the ferrous chloride and ferric chloride The measured values of ferrous chloride and ferric chloride concentrations from the analyzer and the oxidation-reduction potentiometer are input and calculated, and the calculation results are output to the hydrogen peroxide storage tank to determine the hydrogen peroxide replenishment amount. A ferric chloride etchant management device comprising a computer for control).
[0026]
  Practical means for oxidizing cuprous chloride for the regeneration treatment of a metal, for example, an etching solution in etching copper, using ferric chloride etching solution may be electrolytic oxidation, oxidation with an oxidizing agent, or so-called air oxidation.
[0027]
Regeneration system for ferric chloride etchant by diaphragm electrolysis.
As the electrolytic oxidation method, for example, a known membrane electrolysis method using an anion exchange membrane can be used. By applying an electrolysis voltage between a cathode chamber and an anode chamber partitioned by an anion exchange membrane, Electrolysis (oxidation) is performed by selectively moving ions between the tanks through the exchange membrane.
[0028]
  FIG. 2 shows an outline of an apparatus for carrying out a method for managing a ferric chloride etching solution which is adapted to perform oxidation regeneration treatment of an etching solution using the diaphragm electrolysis method. In the figure, the etching solution regeneration tank shown in the center has a cathode tank in which hydrochloric acid as a chemical solution for the regeneration treatment is replenished from the hydrochloric acid electrolyte storage tank, and an aged ferric chloride etching solution from the etching tank is connected to the circulation pump. And an anode chamber circulated through the anion exchange membrane. A voltage from the electrolytic cell power source is applied to the positive / cathode via an amplifier. A hydrochloric acid analyzer is provided in the etching tank, a chlorine generation detection sensor is provided on the anode side, and an electromagnetic induction type conductivity sensor and a liquid level sensor for detecting the hydrochloric acid concentration are provided on the cathode side.
[0029]
During electrolysis, Cl is passed through the exchange membrane from the cathode chamber.⁻Moved to the anode tank,
Fe²⁺  -E⁻ → Fe³⁺
Cu⁺ -E⁻ → Cu²⁺
As a result of oxidation, ferric chloride and cupric chloride are produced. Hydrogen ions are H at the cathode.₂And hydrogen gas is generated. When divalent iron and monovalent copper are all oxidized, Cl₂Gas is generated. Iron ions and copper ions in the anode cell are blocked by the exchange membrane and do not move to the cathode cell. Some water moves from the cathode tank to the anode tank due to the effect of osmotic pressure.
[0030]
When electrolyzed, the concentration of hydrochloric acid in the cathode chamber decreases. In order to keep the hydrochloric acid concentration constant, an electromagnetic conductivity controller is used to automatically replenish hydrochloric acid with a concentration higher than that of the catholyte by a hydrochloric acid concentration controller to keep the concentration constant.
[0031]
In the etching tank, the hydrochloric acid concentration is lowered by etching. In addition, when electrolysis is performed, protons move from the anode tank to the cathode tank, so that hydrogen ions in the anode tank are decreased and pH is increased. Therefore, the hydrochloric acid concentration is measured with a hydrochloric acid analyzer, and the cathode bath solution (hydrochloric acid electrolyte) is automatically supplied to the etching bath so as to maintain a constant concentration. By this replenishment, when the amount of liquid in the cathode tank is insufficient, it is detected by a liquid level sensor, and the hydrochloric acid electrolyte is replenished to a specified level. When hydrochloric acid in the cathode tank is used as a hydrochloric acid replenisher for the etching solution, hydrochloric acid in the cathode tank is not wasted, and new hydrochloric acid is replenished to the cathode tank, so that the hydrochloric acid can be kept in a new state with few impurities. .
[0032]
When the electrolytic power source is turned off, a small amount of copper and iron ions enter the cathode cell through the exchange membrane from the anode cell side. Copper ions that have entered the cathode chamber are reduced at the cathode to become metallic copper, and are deposited on the cathode. The deposited copper is peeled off by hydrogen gas bubbles or the like, and is precipitated, dispersed or floated in the cathode tank in a scum shape. By attaching a filter to the cathode chamber, the metallic copper can be removed and the catholyte can be kept clean.
[0033]
In the anode tank, chlorine gas is generated from the anode when the oxidation with chlorine is finished. In the conventional electrolysis apparatus, an ORP electrode is used to control the power source by detecting the end point of regeneration from the oxidation-reduction potential. However, since the ORP electrode always has a lifetime due to the periodic replenishment of KCl and the deterioration of the comparison electrode, maintenance such as periodic replacement is required. As a simple means, the end point of the regeneration reaction can be detected simply by measuring the potential difference between the platinum sensor or carbon sensor and the anode, and this method eliminates the need for sensor maintenance.
[0034]
[Embodiment of the Invention]
Regeneration device for ferric chloride etchant by oxidant injection
  According to the inventionReprocessing of ferric chloride etchant is an oxidantUsing hydrogen peroxideOf ferrous chloride and cuprous chloride to ferric and cupricInTheIn generalOxidizing agents used for such regeneration treatment include chlorine gas, ozone, chlorates (sodium chlorate, potassium and sodium), hypochlorites (sodium hypochlorite and potassium), and peroxides. Examples include hydrogen and perchloric acid. The reaction of each oxidizing agent is shown below.
[0035]
(1) Chlorine gas regeneration reaction
2FeCl₂ + Cl2 → 2FeCl_Three
Cu₂Cl₂ + Cl2 → 2CuCl₂
(2) Ozone regeneration reaction
2FeCl₂ + O_Three+ 2HCl → 2FeCl_Three + H₂O + O₂↑
Cu₂Cl₂ + O_Three + 2HCl → 2CuCl₂ + H₂O + O₂↑
(3) Regeneration reaction of hydrogen peroxide
2FeCl₂ + H₂O₂ + 2HCl → 2FeCl_Three+ 2H₂O
Cu₂Cl₂ + H₂O₂ + 2HCl → 2CuCl₂+ 2H₂O
(4) Regeneration reaction of chlorate
6FeCl₂ + NaClO_Three + 6HCl → 6FeCl_Three+ NaCl + 3H₂O
3Cu₂Cl₂ + NaClO_Three + HCl → 6CuCl₂+ NaCl + 3H₂O
(5) Regeneration reaction of hypochlorite
2FeCl₂ + NaClO + 2HCl → 2FeCl_Three+ NaCl + H₂O
Cu₂Cl₂ + NaClO + 2HCl → 2CuCl₂+ NaCl + H₂O
[0036]
Among these, chlorine gas is almost impossible to use except for vested offices in Japan in terms of security. Ozone is relatively safe but requires an ozone generator. Regeneration with perchloric acid has a slow reaction rate and is a hazardous material, and its use is not preferred. When chlorate or hypochlorite is added, a large amount of sodium salt or the like is mixed in the etching solution, which affects the etching quality.
[0037]
  Since hydrogen peroxide reacts with iron very rapidly, when using it in ferric chloride etching solution, it is necessary to pay attention to safety, such as injection method and reaction temperature monitoring control. Not so effectiveIn the present invention, hydrogen peroxide is used as the oxidizing agent.The
[0038]
In copper etching, cuprous produced by etching does not contribute to etching. When regenerated, ferrous iron becomes ferric iron and cuprous copper becomes cupric. In addition to the regenerated ferric iron, copper also etches copper. For this reason, if the regeneration is continued, the iron concentration is relatively lowered and the cupric concentration is increased, and finally etching is performed only for cupric, not for ferric iron. In general, ferric chloride is said to cut better than cupric chloride etching. For this reason, it is necessary to replenish a new solution at a certain ratio when it is regenerated and the specific gravity decreases or when an oxidizing agent is replenished. It becomes.
[0039]
The ferric chloride etchant is used with about 0.2 to 1% hydrochloric acid in the ferric chloride solution. This is to prevent the pH of the etching solution from rising due to hydrochloric acid scattering due to heating or drafting, and iron hydroxide sludge being generated and adhering to the substrate surface, or clogging of pipes and the like. However, if the concentration of hydrochloric acid is high, over-etching and deterioration of etching quality occur. Therefore, it is necessary to control the measurement so that the replenishment amount is always kept within a certain range by some method. In addition, in the regeneration with an oxidizing agent, as seen in the regeneration reaction, hydrochloric acid is always required in many cases, and measurement control is indispensable when regeneration is performed.
[0040]
FIG. 3 is an explanatory view of an apparatus for carrying out the ferric chloride etching solution management method according to the present invention, which is configured to perform a regeneration process using hydrogen peroxide as an oxidizing agent. The apparatus shown in FIG. 3 is an apparatus for etching copper with a ferric chloride etchant, an etchant regeneration tank connected to the etcher via an etchant circulation pump, and an oxidizing agent for the regeneration tank. An oxidizing agent storage tank for supplying hydrogen peroxide and hydrochloric acid, a hydrochloric acid storage tank, and a ferric chloride new liquid storage tank for supplying a ferric chloride new liquid to the regeneration tank as necessary. In the regeneration tank, an ORP controller, a pH controller, a specific gravity controller, a thermometer, a cooling device, and a stirrer are installed.
[0041]
ORP meter:
As the etching progresses, the indicated value of the ORP meter decreases. For example, when a platinum electrode and a silver / silver chloride reference electrode are used as an electrode for the platinum electrode, the indicated value is 700 mV to 800 mV for a fresh solution having a liquid temperature of 50 ° C., and is ¼ M of the concentration of the ferric chloride fresh solution. When copper is etched, the voltage drops to about 550 mV to 450 mV. When the indicated value falls below a preset ORPmV value by this ORP meter, hydrogen peroxide as an oxidant is injected, and the injection is stopped when it exceeds the set value.
[0042]
pH meter:
When the oxidant is injected, the pH increases. This is measured with a pH meter, and hydrochloric acid is injected when the pH exceeds a preset pH, and the injection is stopped when the preset pH falls below. As an example, the pH of the new ferric chloride solution is about -0.5 to 1, and when the oxidizing agent is injected, the pH rises rapidly.
[0043]
Hydrometer:
As the etching progresses, the specific gravity of the etching solution increases (for example, in the case of a new solution specific gravity of 1.380, etching of 1/4 M copper of the new solution increases to 1.400). However, when regeneration is performed, the specific gravity of the regenerating solution (oxidant, hydrochloric acid) tends to decrease because the specific gravity is much lower than that of the etching solution. In order to ensure a certain specific gravity, an etching new solution is automatically replenished according to the detection output of the hydrometer.
[0044]
Thermometer, cooler:
In the regeneration reaction, heat of reaction is generated. In particular, when hydrogen peroxide is used, the temperature rises abruptly. Therefore, it is necessary to control the temperature of the regeneration tank using a thermometer. An upper limit temperature is set in advance, and when the set temperature is exceeded, injection of the oxidant is forcibly stopped by an output from the thermometer. Furthermore, an upper limit alarm is also required in the case where the temperature rises. A cooler is provided in the regeneration tank, and when the temperature rises due to the regeneration reaction, the temperature rise is prevented by cooling.
[0045]
Hydrochloric acid analyzer:
In the regeneration treatment of the present invention, the on-time hydrochloric acid concentration is measured with a pH meter in consideration of the response speed, but accurate control of a high hydrochloric acid concentration of 0.2 to 1% is difficult with the pH meter. Therefore, the hydrochloric acid concentration is periodically analyzed using the hydrochloric acid analyzer (hydrochloric acid analyzer) shown in FIG. 4 (required time is about 10 minutes). The supply amount from the hydrochloric acid storage tank can be directly controlled by the output from the analyzer, but this output is used to calibrate the measured value of the pH meter to ensure its accuracy.
[0046]
In FIG. 4, a valve SV1 for injecting a sample, valves SV3 to SV5 for injecting a titrant liquid, a concealing liquid, and the like into an analysis cell into which an analysis sample (etching liquid) having a hydrochloric acid concentration combined with a load cell for sample weight measurement is placed. And a pH electrode.
[0047]
Measuring method
(1) 25% potassium oxalate solution and 0.05% oxalic acid solution are injected into pumps P4 and P5 through valves SV4 and SV5 and automatically adjusted to a predetermined pH of 6 to 6.2. Is stored in the computer CPU.
(2) The etching solution sample is injected from the pump P1 through the valve SV1, and the pH in the cell lowered by the hydrochloric acid contained is titrated so that the 0.1N NaOH solution is dropped from the SV3 to the above memory value. The hydrochloric acid concentration in the sample is calculated by the computer CPU based on the titration value.
(3) When the calculated value falls below a predetermined hydrochloric acid target concentration, the CPU calculates the replenishment amount and outputs a calculated replenishment output signal or a pH meter calibration signal.
[0048]
Ferrous chlorideandFerric analyzer
  It is known that it is preferable to leave some reducing substances in the etching solution for good quality etching. For this reason, for example, ferrous chlorideandIt is necessary to control the ferric iron concentration to a predetermined value. In the regeneration process of the present invention, an ORP sensor is used in terms of responsiveness, but its accuracy and stability are not sufficient, so ferrous chloride shown in FIG.andThe concentration is periodically measured as an absolute value using a ferric analyzer, and a set value of ORP or the like is set by a calculation value based on the concentration.
[0049]
The basic configuration of this analyzer is the same as that of the hydrochloric acid analyzer shown in FIG. 4, and the concentration as an absolute value is obtained by titration based on the sample weight measured by the load cell. The measurement cell, injection valves SV1 to SV6 such as potassium permanganate titrant, titanium trichloride titrant and dilute sulfuric acid are provided for the analysis cell.
[0050]
In the ferrous chloride / ferric chloride analyzer of FIG. 5, ferric chloride and cupric chloride as oxidizing substances and ferrous chloride and cuprous chloride as reducing substances are analyzed. The analysis method is performed according to the known reduction titration and oxidation titration methods, and the operation of the analyzer is basically the same as that of the hydrochloric acid analyzer of FIG.
[0051]
Oxidant sensor:
In the regeneration tank of the regeneration apparatus shown in FIG. 3, an ORP meter is used as an oxidant (hydrogen peroxide) sensor. Instead, a single noble metal wire (Pt or Au) is disposed inside the oxidant injection nozzle, and the regeneration tank. If one noble metal wire (Pt or Au) is installed in the inside (near the oxidant injection nozzle) and the potential difference between the two noble metal wires is measured, the potential measurement shown in FIG. 6 can be performed and used for controlling the oxidant. be able to. Since this sensor has a simple structure, no maintenance is required, and the substantial end point of the regeneration reaction can be confirmed with this sensor.
[0052]
Oxidant injection nozzle:
When hydrogen peroxide is used as an oxidizing agent, the reaction with ferric chloride solution may cause an extreme and dangerous bumping condition, so as little hydrogen peroxide as possible is injected over time. When injected directly into the liquid from the pump through the pipe, even if the check valve fails, the oxidizer flows into the iron liquid due to the siphon phenomenon, or the iron liquid in the oxidizer tank flows backward due to the siphon phenomenon. It enters an explosive state. For this reason, hydrogen peroxide must be physically separated from the liquid as shown on the left side of FIG. 7, but when dripped, it reacts extremely on the surface of the iron liquid, where a bumping state occurs and scatters around. For this reason, the injection location must always be in a negative pressure state, such as with an intake duct.
[0053]
In the embodiment of the present invention, as shown on the right side of FIG. Even if the nozzle tip is immersed in the liquid, the pressure due to the reaction escapes from the slit, and the iron liquid is siphon-cut by the slit, so that no back flow occurs even if the check valve fails. The liquid level of the oxidizer tank or the oxidizer temporary tank is set lower than the liquid level of the regeneration tank.
[0054]
Gas oxidation treatment of ferric chloride etchant
The oxidation regeneration treatment of the ferric chloride etching solution can use so-called air oxidation although it takes a relatively long time. As a gas used for oxidation, a gas containing oxygen, for example, air, a gas containing ozone, or the like is used.
[0055]
  FIG. 8 shows an outline of an apparatus used for regenerating the ferric chloride etching solution by gas oxidation. In the apparatus of FIG. 8, the liquid reservoir of the regenerator is connected to the ferric chloride etching apparatus via an etchant circulation pump, and a hydrochloric acid storage tank and a new liquid storage tank are respectively supplied to the liquid reservoir. Connected through. In addition, a hydrochloric acid analyzer, Fe / ferric chloride and ferrous chloride concentrations are detected in the liquid reservoir.²⁺/ Fe³⁺An analyzer and a specific gravity meter that detects and controls the change (increase) in the specific gravity of the etchant accompanying the progress of the etching process and the gas oxidation process are provided.
[0056]
A gas circulation blower for circulating and supplying an oxidizing gas from an oxygen or ozone generator through a mixer is connected to a bubbling device at the bottom of the liquid reservoir. The gas / liquid mixture from the bubbling device is sprayed uniformly on the column from the spray section above the apparatus by the circulation pump of the regenerator, oxidizes by gas / liquid contact, and flows down to the liquid reservoir. In addition, the mist leakage prevention filter at the time of discharging | emitting the gas after contact to the scrubber outside an apparatus is provided above the spray in the figure.
[0057]
Hydrochloric acid analyzer:
Since the oxidation reaction between the gas and the etching solution is slow, the hydrochloric acid concentration is controlled by the hydrochloric acid analyzer. When the hydrochloric acid concentration falls below a preset hydrochloric acid concentration, hydrochloric acid is replenished from the hydrochloric acid storage tank by the acid replenishment pump.
[0058]
Hydrometer:
Since the etching solution is made into a mist, water evaporates and the specific gravity tends to increase. The specific gravity also increases by etching. For this reason, an appropriate amount of a ferric chloride fresh solution having a specific gravity sufficiently lower than that of the etching solution is replenished by a specific gravity meter.
[0059]
Fe²⁺/ Fe³⁺Analyzer:
When the ferric iron concentration rises above a preset ratio, the regenerator is stopped or new liquid is correctly replenished by the hydrometer (the ratio of ferric iron to ferrous iron is ensured within a certain range). It has a function to monitor whether or not.
[0060]
Gas circulation blower:
In order to effectively use the gas inside the regenerator and to bubble the etching solution in the liquid reservoir, the gas is circulated in the regenerator.
[0061]
In the illustrated apparatus, the ferric chloride etching solution of the etching apparatus is constantly circulated through the liquid retaining portion. When the hydrochloric acid concentration falls below a set value during etching, a predetermined amount of hydrochloric acid is supplied from the hydrochloric acid storage tank by the hydrochloric acid analyzer.
[0062]
The gas circulation blower is always operated to send air or oxygen from the generator through the gas mixer to the bubbling device in the liquid reservoir. The bubble-mixed regenerated liquid thus produced is pumped upward by the recirculation pump of the regenerator, sprayed from the spray section and evenly sprayed on the column, and complete gas / liquid contact is made, whereby the chloride in the regenerated liquid is made. Ferrous and cuprous chloride are oxidized to ferric and cupric, respectively.
[0063]
After the regeneration process is completed, Fe²⁺/ Fe³⁺When the analyzer detects an increase in the ferric chloride (and cupric chloride) concentration above a predetermined value, the circulation of the regenerating solution is stopped by that signal. Further, when the specific gravity of the etching solution increases due to the moisture device using the spray of the etching solution or the progress of the etching, the hydrometer detects this and replenishes the new solution with the etching solution from the new solution storage tank.
[0064]
Although the present invention has been described above with respect to the liquid management apparatus used for etching copper with the ferric chloride etching solution shown in the figure, the present invention is not limited to copper etching but also for etching iron and other metals. As the ORP sensor, potentiometric sensor, hydrochloric acid analyzer, and ferric chloride / ferrous chloride analyzer, various detection means equivalent to this can be used in addition to the illustrated example.
[0065]
【The invention's effect】
As described above, according to the present invention, ferrous chloride and cuprous chloride generated in the etching process when copper is etched with a ferric chloride etchant are oxidized to ferric chloride and cupric chloride timely or constantly. As a result, the etching solution is regenerated to maintain a high etching ability, and the workpiece can be effectively etched for a long time. As a result, the frequency of new liquid replacement is reduced and the amount of drainage is reduced, which is effective for saving resources and protecting the environment.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a graph showing a trend of changes in concentration of an oxidizing substance and a reducing substance with respect to copper solubility in a ferric chloride etchant.
FIG. 2 is a diagram showing an outline of a ferric chloride etchant management device that performs a regeneration process by electrolytic oxidation.
FIG. 3 is a diagram showing an outline of a ferric chloride etchant management apparatus according to the present invention for performing a regeneration process by oxidizing agent oxidation.
FIG. 4 is a diagram showing an outline of a hydrochloric acid concentration analyzer used in an etching solution management apparatus according to the present invention.
FIG. 5 is a view showing an outline of a ferrous chloride / ferric chloride analyzer used in an etching solution management apparatus according to the present invention.
FIG. 6 is a diagram illustrating characteristics of an oxidant sensor used in an etching solution management apparatus according to the present invention.
FIG. 7 is a diagram showing an outline of an oxidizing agent injection nozzle used in an etching solution management apparatus according to the present invention.
FIG. 8 is a diagram showing an outline of a ferric chloride etchant management device that performs a regeneration process by gas oxidation.

Claims (1)

In a ferric chloride etchant management apparatus of a type that regenerates an etchant by oxidizing ferrous chloride and cuprous chloride generated by etching in etching copper with a ferric chloride solution,
An etching tank containing a ferric chloride solution, a regeneration tank connected to the etching tank via a circulation path, a hydrogen peroxide storage tank connected to the regeneration tank, a hydrochloric acid storage tank, and the regeneration tank Hydrochloric acid analyzer and pH meter by titration analysis method for hydrochloric acid concentration measurement, ferric chloride and ferrous chloride analyzer and redox potentiometer by titration analysis method for ferrous chloride and ferric chloride concentration measurement When,
Calculating each hydrochloric acid concentration measurement value from the hydrochloric acid analyzer and pH meter, inputting the calculation result to the hydrochloric acid storage tank to control the replenishment amount of hydrochloric acid, and the ferrous chloride and ferric chloride The measured values of ferrous chloride and ferric chloride concentrations from the analyzer and the oxidation-reduction potentiometer are input and calculated, and the calculation results are output to the hydrogen peroxide storage tank to determine the hydrogen peroxide replenishment amount. A ferric chloride etchant management device comprising a computer for controlling .

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