JP2004217814A - Washing composition for device substrate and washing method and washing apparatus each using the same composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a washing composition for device substrates capable of effectively removing contamination by particles, etc., on the substrate while preventing corrosion and fusion of wiring, a device material such as an insulation film or a capacity film in washing of the device substrate and to provide a washing method and a washing device by using the washing composition. <P>SOLUTION: The substrate is washed by using a basic aqueous solution containing a nonionic surfactant having ≥3 and <12 HLB and a nonionic surfactant having ≥12 and ≤20 HLb and each having at least one hydroxy group in one molecule and having nearly ≥-1,200 mV and ≤100 mV or nearly ≥400 mV and ≤1,200 mV oxidation-reduction potential based on hydrogen electrode at 25°C. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

（Ｘ１〜Ｘ４のうち、少なくとも１つがＯＨ基であり、残りはＯＣＯＲを示す。Ｒは炭素数５〜１７の炭化水素基を示す。）
【化６】

（Ｘ１〜Ｘ５のうち、少なくとも１つがＯＨ基であり、残りはＯＣＯＲを示す。Ｒは炭素数５〜１７の炭化水素基を示す。）
【化７】

（Ｘ１〜Ｘ５のうち、少なくとも１つがＯＨ基であり、残りはＯＣＯＲを示す。Ｒは炭素数５〜１７の炭化水素基を示す。また、ｎは２〜１０の数を示す。）
【化８】

（Ｘ１〜Ｘ４のうち、少なくとも１つがＯＨ基であり、残りはＯＣＯＲを示す。Ｒは炭素数５〜１７の炭化水素基を示す。）
【００２３】
上記一般式［１］〜［４］のＸは、何れもＯＨあるいはＯＣＯＲの化学式で示される極性部であり、当該極性部にエチレンオキサイドが任意に付加したものを用いることもできる。また、Ｒは炭化水素基であり、水中での分散性、抑泡性、すすぎの簡便性などの点から炭素数が５〜１７であることが好ましい。さらに、一般式［３］中に示されるｎは、グリセリン脂肪酸エステルの重合度に係わる数であり、粘性や水溶性などの点から２〜１０の範囲であることが好ましい。上記一般式［１］で示される化合物の具体例としては、モノカプリン酸ソルビタン、モノラウリン酸ソルビタン、モノパルチミン酸ソルビタン、トリオレイン酸ソルビタンなどが挙げられる。また、上記一般式［２］で示される化合物の具体例としては、モノラウリン酸ＰＯＥ（６）ソルビット、テトラステアリン酸ＰＯＥ（６０）ソルビット、テトラオレイン酸ＰＯＥ（４０）ソルビットなど、上記一般式［３］の具体例としては、モノラウリン酸ヘキサグリセル、ジステアリン酸デカグリセル、モノラウリン酸デカグリセルなど、上記一般式［４］の具体例としては、テトラ２−エチルヘキサン酸ペンタエリスリトール、ペンタエリスルトールモノパルミテートなどが挙げられる。
【００２４】
本発明の洗浄組成物では、ＨＬＢ値の異なる非イオン界面活性剤を少なくとも２種以上含有することが好ましい。これにより、界面活性剤分子の会合が生じ、ＨＬＢ値がより小さい界面活性剤の水溶性が高められると同時に、それぞれの界面活性剤の特性が相乗的に得られる。また、ＨＬＢが３以上１２未満の非イオン界面活性剤と、ＨＬＢが１２以上２０以下の非イオン界面活性剤を混合して使用することにより、界面活性剤分子の会合体の良好な分散性が得られると共に、防食性に優れた親水性の基板表面を形成することができる。さらに、泡立ちも抑えられるという利点が得られる。
【００２５】
図１には、非特許文献１に記載された非イオン界面活性剤の用途の分類と、本発明で見出されたデバイス基板洗浄に対する効果をＨＬＢ値と併せて示した。一般的に、ＨＬＢが３以上１２未満の非イオン界面活性剤は、水溶性に乏しく、水中では水と分離あるいは懸濁したり、基板に残留したりする上、パーティクルの付着を促進する作用があるために、デバイス基板の洗浄にはほとんど用いられない。ところが、この範囲のＨＬＢの界面活性剤は、気泡界面に対して均一な吸着配向が起こり難く、気泡の安定性が失われるために、抑泡性に優れるという特徴がある。また、固体表面に吸着すると、界面活性剤分子自体の疎水作用により優れた防食効果が得られる特徴がある。一方、ＨＬＢが１２以上２０以下の非イオン界面活性剤は、水溶性が高く、低濃度でも表面を親水化させて、パーティクルの付着力を低下させる作用がある。その反面、気泡を安定化させる作用が強く、激しい泡立ちが発生するために、デバイス基板の洗浄プロセスにおいては非常に扱い難く敬遠される。
【００２６】
このように各々の非イオン界面活性剤には一長一短があるが、本発明では、ＨＬＢが３以上１２未満の非イオン界面活性剤と、ＨＬＢが１２以上２０以下の非イオン界面活性剤を共存させるという新規の発想により、それぞれの問題点が解消されると同時に、デバイス基板の洗浄に対して優れた洗浄特性が相乗的に得られることを見出した。本発明の非イオン界面活性剤の複合効果をさらに強化させる場合には、ＨＬＢが３以上１０以下の非イオン界面活性剤と、ＨＬＢが１３以上２０以下の非イオン界面活性をそれぞれ含有させるのが好適であり、より優れた防食効果が得られる。
【００２７】
非イオン性界面活性剤の含有量は、洗浄組成物に対して好ましくは略０．０００１〜０．１質量％、より好ましくは略０．０００５〜０．０５質量％とする。この濃度が薄すぎると充分な洗浄効果が得られず、また、金属や誘電体の腐食や溶解が生じ、逆に濃すぎると基板に多量に残留して他の汚染を誘発するばかりでなく、排水処理にかかる費用が増大する。
【００２８】
また、本発明の洗浄組成物に、陰イオン界面活性剤を含有させることができる。陰イオン界面活性剤は、基板とパーティクルの表面を同符号に帯電する作用があり、パーティクル汚染が除去し易くなると同時に、一旦除去したパーティクルの再付着が防止できる効果が得られる。本発明に用いる陰イオン界面活性剤は、特に限定されないが、ナトリウムなどの金属を含まないものであることが好ましい。陰イオン界面活性剤にナトリウムが含まれると、基板に吸着あるいは拡散して、デバイスの電気的特性を劣化させる原因になるからである。なお、生体に対する毒性や抑泡性の点では、陰イオン界面活性剤は非イオン界面活性剤に劣るものの、略０．０００１〜０．０１質量％の濃度で用いることにより、その弊害を最小限に抑えつつ本来の優れた洗浄特性を最大限に利用することができる。
【００２９】
また、本発明の洗浄組成物に、アルコールを含有させることができる。アルコールは、分子中に極性部と非極性部の両方を有するため、水だけでなく、極性の小さい界面活性剤に対しても容易に混合する。このため、水溶性に乏しい界面活性剤の水中での分散性を高めることができ、洗浄後の基板への界面活性剤の残留を少なくする効果も得られる。本発明に用いるアルコールとしては、プロピレングリコール、エチレングリコール、ポリエチレングリコールなどの揮発性の低い多価アルコールが洗浄液の安定性の点で好適であるが、洗浄液を循環使用しない場合など、洗浄液の安定性が特に問題にならない場合には、エタノールやプロパノールなどの揮発性アルコールも用いることができる。前記アルコールは界面活性剤の濃度に応じて任意に添加することができる。
【００３０】
本発明における洗浄組成物の酸化還元電位は略−１２００ｍＶ以上１００ｍＶ以下、または略４００ｍＶ以上１２００ｍＶ以下（水素電極基準、２５℃）とすることが好ましい。図２は、種々の酸化還元電位調整剤を用いて純水の酸化還元電位を調整し、パーティクル除去性について調べた結果である。この実験では、酸化還元電位の効果のみを調べるために界面活性剤は一切添加しておらず、また、ｐＨの影響を避けるために緩衝剤を使用して液性をｐＨ７に調整して洗浄を行った。図２から分かるように、パーティクル除去性は、酸化還元電位の値に強く依存し、銀／塩化銀電極基準（２５℃）で略−１４００ｍＶ付近から−１００ｍＶ付近まで、および略２００ｍＶ付近から１０００ｍＶ付近までの領域で、パーティクル除去率が略５０％以上となり、パーティクル除去性が著しく向上した。すなわち、パーティクル除去に好適な酸化還元電位の範囲は、水素電極基準（２５℃）にして、略−１２００ｍＶ以上１００ｍＶ以下、および略４００ｍＶ以上１２００ｍＶ以下の領域であった。酸化還元電位が略１００ｍＶ〜４００ｍＶ（水素電極基準）の範囲は、通常の水（常温常圧下において空気が溶解した状態の水）の酸化還元電位の範囲であり、この範囲より小さいか、大きい場合にパーティクル除去作用が発現することが確認できた。この範囲の酸化還元電位を有する洗浄組成物は、基板やパーティクルの表面に洗浄に好適な電位差を与え、パーティクル汚染の除去に有効に作用する。
【００３１】
本発明における洗浄組成物の酸化還元電位を水素電極基準（２５℃）で略−１２００ｍＶ以上１００ｍＶ以下、または略４００ｍＶ以上１２００ｍＶ以下にするための酸化還元電位調整剤として、純水の電気分解によって得られる陰極水あるいは陽極水を用いることもできる。
【００３２】
本発明の洗浄組成物の酸化還元電位を水素電極基準（２５℃）で略−１２００ｍＶ以上１００ｍＶ以下にするための酸化還元電位調整剤としては、水素ガス、ヒドロキシルアミンまたはその塩、エチルアミン、プロピルアミンなどのアミン類、アンモニア、水酸化テトラメチルアンモニウム、グリオキシル酸、シュウ酸などのカルボン酸類、ホルムアルデヒド、アセトアルデヒドなどのアルデヒド類、チオ硫酸塩、亜ジチオン酸塩、ギ酸、アスコルビン酸、グルコースなどの糖類などの還元性物質が用いることができる。塩を用いる場合には、デバイスの特性に悪影響を及ぼさない塩が好ましく、特にアンモニウム塩のように金属を含まないものが好ましい。これらのうち、何れを選択した場合でも酸化還元電位を低下させることができる。しかしながら、上記のうち特定の種類のものを選択することにより、さらに多くの利点を得ることができる。例えば、水素ガス、アミン、カルボン酸からなる群から選ばれる１または２以上の成分を含有する洗浄組成物を用いれば、極めて少量の添加量でも酸化還元電位を低下させることができる。また洗浄後のすすぎ工程を簡略化できるという利点も得られる。とりわけ、酸化還元電位調整剤として水素を用いると、添加によるｐＨ変動が生じず工程における洗浄組成物の濃度管理を簡便化できる上、排水処理への負荷も大幅に軽減できる。
【００３３】
また、本発明の洗浄組成物の酸化還元電位を水素電極基準（２５℃）で略４００ｍＶ以上１２００ｍＶ以下にするための酸化還元電位調整剤としては、酸素ガス、オゾン、二酸化炭素、過塩素酸又はその塩、次亜塩素酸またはその塩、過酸化水素水などの過酸化物類、ペルオキシ酢酸などのペルオキソ酸またはその塩などの酸化性物質を用いることができる。塩を用いる場合には、デバイスの特性に悪影響を及ぼさない塩が好ましく、特にアンモニウム塩のように金属を含まないものが好ましい。これらのうち、何れを選択した場合でも酸化還元電位を増大させ、基板のパーティクルを除去することができる。しかしながら、上記のうち特定の種類のものを選択することにより、さらに多くの利点を得ることができる。例えば、酸素又はオゾン、あるいは両方を含有する洗浄組成物を用いれば、極めて少量の添加量で酸化還元電位を上昇させることができ、金属や金属化合物の腐食や溶解を防止しつつ、基板のパーティクルを効果的に除去することができる。また洗浄後のすすぎ工程や排水処理を簡略化できるという利点も得られる。
【００３４】
本発明における洗浄組成物のｐＨは略５〜１２であることが好ましい。一般に、パーティクルの洗浄性は塩基性領域が優れているとされ、一方、金属や金属化合物の腐食や溶解は中性領域で起こり難いとされている。図３は、洗浄液のｐＨとパーティクル除去性、および金属および金属化合物の腐食度の関係を調べた結果である。ｐＨ５付近から塩基性領域では、パーティクルと基板の表面が同符号に帯電し静電的反発が生じるため、パーティクル除去性が大きく向上する。一方、金属および金属化合物の腐食度は、それぞれの物性により傾向が異なるものの、ｐＨが中性から酸性領域にかけて、あるいは中性から塩基性領域にかけて腐食度が著しく増大する。本発明では、前記界面活性剤および酸化還元電位を選択することにより、酸性から塩基性の広いｐＨ領域においてパーティクル洗浄の目的で使用できるが、ｐＨが５〜１２においては基板の防食とパーティクルの除去の両特性が共に良好である。また、ｐＨが５〜１２の範囲では、キレート化剤を添加剤として加えた場合に、より効果的にキレート作用が得られる利点もある。なお、洗浄液のｐＨが１２より高くなると、界面活性剤の加水分解が生じたり、洗浄液中の塩濃度が高くなるためにすすぎ工程に時間がかかったりするなどの問題が生じる。
【００３５】
また、洗浄組成物の使用温度は特に限定されず、使用する非イオン界面活性剤の種類や、添加剤の種類、これらの量に応じて最適な温度条件を選択すればよいが、実用上は略５〜７０℃の温度範囲が好ましい。
【００３６】
本発明では、フッ化物イオンを洗浄組成物に含有させて洗浄に用いることもできる。フッ化物イオンが添加された洗浄組成物は、シリコン酸化膜などの表面をわずかに等方性エッチングする作用があるため、一般に除去が困難な基板に埋没したようなパーティクル汚染の除去も可能である。また、洗浄液中に遊離した金属不純物と結合して溶解させる作用があるため、基板への金属汚染の付着を防止する効果がある。さらに、パターン形成においては、アッシングあるいはエッチング後に生じた残差の除去にも優れた効果がある。なお、フッ化物イオンが高濃度になると、金属あるいは金属化合物の腐食の原因になる場合があり、本発明におけるフッ化物イオンの含有濃度としては略０．０１〜０．５質量％が好適である。
【００３７】
本発明では、ベンゾトリアゾールまたはその誘導体を含有させて洗浄に用いることもできる。ベンゾトリアゾールまたはその誘導体が添加された洗浄組成物は、銅やアルミニウム、銀などをはじめとする金属あるいは金属化合物の表面に保護被膜を形成し、防食性が向上する効果が得られる。一般に、ベンゾトリアゾールまたはその誘導体は、金属や金属化合物表面に吸着することにより、表面を疎水化させて腐食を防止する。本発明の洗浄組成物では、ベンゾトリアゾールまたはその誘導体が吸着した金属あるいは金属化合物表面を、さらに親水化させる作用があるため、もとの防食性を維持したまま、パーティクル除去に好適な親水性表面を形成することができる。なお、表面を疎水化させて腐食を防止するという点では、本発明のＨＬＢ３以上１２未満の非イオン界面活性剤の作用と類似しており、ＨＬＢ３以上１２未満の非イオン界面活性剤の成分に替えてベンゾトリアゾールまたはその誘導体を用いて洗浄することもできる。
【００３８】
本発明では、キレート化剤を含有させて洗浄に用いることもできる。キレート化剤とは、金属や金属化合物に対してキレート錯体を形成する能力を有する化合物をいう。具体的には、エチレンジアミン四酢酸（ＥＤＴＡ）、トランス−１，２−シクロヘキサンジアミン四酢酸（ＣｙＤＴＡ）、ニトリロトリ酢酸（ＮＴＡ）、ジエチレントリアミンペンタ酢酸（ＤＴＰＡ）、Ｎ−（２−ヒドロキシエチル）エチレンジアミン−Ｎ，Ｎ’，Ｎ’−トリ酢酸（ＥＤＴＡ−ＯＨ）等の化合物、またはこれらの塩が挙げられる。塩を用いる場合は、半導体装置の特性に悪影響を及ぼさない塩が好ましく、特にアンモニウム塩のように金属を含まない塩が好ましい。キレート化剤の含有率は、塩基性洗浄液に対して好ましくは略１〜１０，０００ｐｐｍ、より好ましくは略１０〜１，０００ｐｐｍとする。この濃度が薄すぎると充分なキレート効果が得られず、逆に濃すぎると基板表面に有機物が残存して半導体素子の性能を劣化させる要因になり、廃液の処理に費用がかかる。このようなキレート化剤を用いれば、基板表面に付着した金属汚染を除去できると共に、いったん除去した金属汚染の再付着を効果的に防止することができる。
【００３９】
本発明において洗浄を行う際、超音波を印加することが好ましい。このようにすることによって洗浄効果を一層高めることができる。この際、超音波の周波数は８００ｋＨｚ以上とすることが好ましい。８００ｋＨｚ未満であると、ウエハにダメージを与えることがあり、また、超音波による洗浄作用が充分に得られない場合がある。
【００４０】
本発明において洗浄を行う際、上記洗浄組成物にガスを溶解させて洗浄することもできる。ガスが溶解した洗浄組成物は、洗浄の際にわずかに脱ガスが生じ、この作用により基板上のパーティクルがリフトオフし易くなり除去性が向上する効果が得られる。この場合のガスとしては、常温常圧においてガス状態で存在するものが好ましく、具体的には、水素、窒素、酸素、ヘリウム、アルゴン、二酸化炭素などのガスを挙げることができる。これらのうち、水素、酸素、二酸化炭素などは酸化還元電位調整剤としても機能するものであり、他の酸化還元電位調整剤と組み合わせて、あるいはこれらを単独に過剰に添加することで、酸化還元電位調整剤としての機能に追加して、パーティクル除去性の向上を図ることができる。
【００４１】
本発明の洗浄組成物を用いた洗浄では、種々の洗浄方法を適用することができる。たとえば浸漬法、スピン洗浄法、ブラシ洗浄法、スプレー法、ジェット噴射法、シャワー洗浄法または他の機械的方法によって行うことができる。
【００４２】
本発明の洗浄組成物を用いて基板を洗浄した後、さらにＨＬＢ値が１５以上２０以下の非イオン界面活性剤あるいは陰イオン界面活性剤を含有する水溶液を用いて洗浄を行うことができる。これにより、基板表面の親水性がさらに向上し、パーティクル除去性が向上する効果が得られる。この洗浄に用いる界面活性剤としては、ＨＬＢの値が１５以上２０以下の非イオン界面活性剤、あるいは陰イオン界面活性剤であれば特に限定されない。このような界面活性剤を用いることにより、低濃度の水溶液においても基板表面の親水性を効果的に高めることができる。また、界面活性剤の濃度としては略０．０００１〜０．００５質量％であることが好ましい。これ以上の濃度になると、泡立ちが生じて制御性が低下するばかりでなく、洗浄後の基板表面に界面活性剤が残留するという問題が生じる。また、これ以下の濃度では、基板表面を親水化する作用が不充分となるほか、濃度制御が困難となる。
【００４３】
本発明の洗浄に用いる基板洗浄装置は、洗浄組成物の濃度を一定の範囲に維持するために、前記洗浄組成物の濃度制御手段を備えたものであることが好ましい。特に界面活性剤は、洗浄処理に伴い基板表面に吸着して徐々に濃度が減少するため、洗浄中は濃度を連続あるいは断続的に測定しながら、適正濃度範囲になるように添加することが好ましい。界面活性剤の濃度測定には、比重計の他、ＣＯＤ計、接触角計、表面張力計などを用いることができる。
【００４４】
【実施例】
以下、実施例を参照して本発明をさらに詳細に説明するが、本発明はこれらの実施例のみに限定されるものではない。
【００４５】
下記の実施例に示す洗浄評価に用いた洗浄装置の概要を図４に示す。本洗浄装置では、純水は脱気装置１において脱気処理され、気体透過膜２へ通水される。気体透過膜２では、外部に接続されたガスボンベ（不図示）から水素等のガスが供給される。前記脱気された純水に気体透過膜２を透過した水素等のガスが溶解し水素溶解水等のガス溶解水が生成する。さらに、界面活性剤やｐＨ調製剤等の添加剤が貯留タンク３〜５からポンプ６〜８により供給され、インラインミキサー９において前記ガス溶解水に混合される。なお、純水にガスを溶解させない場合には、純水はバイパス１０を通して通水され、インラインミキサー９で前記添加剤と混合される。添加剤が混合されたガス溶解水（以下、洗浄液という。）は、ノズル１１を介して基板１２に供給される。ノズル１１には超音波発振器（不図示）が具備されており、任意の音圧および振動数を洗浄液に付与することができる。また、ノズル１１が固定されたアーム部１３は、基板１２上で水平方向に移動させることができ、基板１２は回転支持台１４に固定されて回転することにより、基板１２の表面全体をまんべんなく洗浄することができる。
【００４６】
［実施例１］
本実施例で使用した洗浄液の調製条件を表１に示す。酸化還元電位調整剤として水素を用いた。当該洗浄液に関し、後述の方法によりパーティクル除去性と、アルミニウム配線に対する腐食性と、洗浄液の泡立ちの程度とを評価し、これらの結果を踏まえて洗浄液の性能を総合的に評価した。
【００４７】
【表１】

【００４８】
（パーティクル除去性の評価）
本実施例では、本発明の洗浄組成物のパーティクル除去性について調べるため、シリコン基板にＰＳＬ（ポリスチレンラテックス）を付着させたものを用いた。ＰＳＬは、疎水性のパーティクルであり、疎水性のシリコン基板に付着し易く除去し難いので、洗浄性を厳しく評価することができる。
【００４９】
まず、６インチシリコン基板を０．２μｍのＰＳＬ粒子を分散させた純水に浸漬し、基板表面にＰＳＬ粒子を３０００〜５０００個程度付着させ、乾燥させた。その後、基板をスピン洗浄により３０秒間洗浄した。洗浄中は、基板を５００ｒｐｍで回転させ、表１の成分の水溶液を毎分１．５リットルの流量で供給しながら１ＭＨｚのメガソニックを照射した。洗浄液の温度は、室温（１８〜２０℃）とした。
【００５０】
洗浄前後におけるシリコン基板上のＰＳＬ粒子の付着量をパーティクルカウンターを用いて分析した。以下の基準により除去性を評価した。
５・・・・・パーティクル除去率が９０％以上
４・・・・・パーティクル除去率が８０以上〜９０％未満
３・・・・・パーティクル除去率が５０以上〜８０％未満
２・・・・・パーティクル除去率が１０以上〜５０％未満
１・・・・・パーティクル除去率が１０％未満
【００５１】
（アルミニウム配線に対する腐食性の評価）
さらに、洗浄液中でのアルミニウム配線の腐食性を調べるため、アルミニウム配線（厚さ３００ｎｍ）が成膜されたガラス基板上を表１の洗浄液に浸漬し、腐食の程度を評価した。洗浄液の温度を４０℃、浸漬時間を１５分とし、浸漬前後におけるアルミニウム配線の形状を走査型電子顕微鏡（ＳＥＭ）を用いて観察した。以下の基準により腐食程度を評価した。
５・・・・ほとんど変化が認められない
４・・・・わずかに腐食が認められる
３・・・・部分的な腐食が認められる
２・・・・半分以上に腐食が認められる
１・・・・全体が腐食しているか全て溶解
【００５２】
（洗浄液の泡立ち程度の評価方法）
また、洗浄液の泡立ちの程度を調べるため、バブリング試験による評価を行った。５００ｍｌのメスシリンダーに表１の洗浄液１００ｍｌを入れ、乾燥空気を毎分８０ｍｌの流量でディフューザーストーンを用いて１分間通気した。洗浄液の温度は室温とした。通気を１分間行った後に液面に生成した泡の量、および通気を停止してから１分後の泡の残留量を観察した。以下の基準により泡立ちの程度を評価した。
５・・・・ほとんど泡立ちが認められず、泡の残留も認められない
４・・・・わずかに泡立ちが認められるが、泡の残留はほとんど認められない
３・・・・やや泡立ちが認められるが、泡の残留は少ない
２・・・・やや泡立ちが認められ、大半が残留したままである
１・・・・多量の泡立ちが認められ、大半が残留したままである
【００５３】
（洗浄液の総合評価）
上記の各評価を踏まえて、洗浄液の洗浄性能について総合評価した。評価基準は以下の通りとした。
５・・・・・全ての評価基準に対して総合的に優れている
４・・・・・総合的に充分な洗浄性能を有している
３・・・・・総合的に洗浄性能がやや不足する
２・・・・・いくつかの評価基準において洗浄性能が著しく不足する
１・・・・・ほとんど洗浄性能を有していない
【００５４】
［実施例２］
本実施例では、表１に示す成分に、ポリオキシエチレンノニルフェニルエーテル（非イオン界面活性剤、ＨＬＢ＝１９）を０．００１％の濃度で添加した洗浄液を用いた。ＯＲＰ（酸化還元電位）は−５６１ｍＶであった。これらのパラメータ以外の洗浄液調製条件ならびに実験および評価方法は実施例１と同様にした。
【００５５】
［実施例３］
本実施例では、表１に示す成分の内プロピレングリコールをポリオキシエチレンアルキルエーテル硫酸トリエタノールアミン（陰イオン界面活性剤）に替えた洗浄液を用いた。ＯＲＰは−５８８ｍＶであった。これらのパラメータ以外の洗浄液調製条件ならびに実験および評価方法は実施例１と同様にした。
【００５６】
［実施例４］
本実施例では、表１に示す成分にフッ化アンモニウムを０．１％の濃度で混合した洗浄液を用いた。ＯＲＰは−５２５ｍＶであった。これらのパラメータ以外の洗浄液調製条件ならびに実験および評価方法は実施例１と同様にした。
【００５７】
［比較例１］
本比較例で使用した洗浄液の調製条件を表２に示す。本比較例では、実施例１の成分の内、ＨＬＢの低い非イオン界面活性剤（モノラウリン酸ソルビタン）のみを用いた。実験および評価方法は実施例１と同様にした。
【００５８】
【表２】

【００５９】
［比較例２］
本比較例では、表２に示す成分の内、モノラウリン酸ソルビタンをモノラウリン酸デカグリセル（非イオン界面活性剤、ＨＬＢ＝１５．５）に替えた洗浄液を用いた。これらのパラメータ以外の洗浄液調製条件ならびに実験および評価方法は比較例１と同様にした。
【００６０】
［比較例３］
本比較例では、表２に示す成分の内、モノラウリン酸ソルビタンをポリオキシエチレンアルキルエーテル硫酸トリエタノールアミン（陰イオン界面活性剤）に替えた洗浄液を用いた。これらのパラメータ以外の洗浄液調製条件ならびに実験および評価方法は比較例１と同様にした。
【００６１】
［比較例４］
本比較例では、純水に水素ガスを溶解させた水素溶解水（ｐＨ７、ＯＲＰ：−４１５ｍＶ）を洗浄液として用いた。これらのパラメータ以外の洗浄液調製条件ならびに実験および評価方法は比較例１と同様にした。
【００６２】
［比較例５］
本比較例では、純水に水素ガスを溶解させた水素溶解水（ｐＨ１０、ＯＲＰ：−４１５ｍＶ）を洗浄液として用いた。これらのパラメータ以外の洗浄液調製条件ならびに実験および評価方法は比較例１と同様にした。実施例１乃至４および比較例１乃至４の結果を、表３にあわせて示す。
【００６３】
実施例１乃至４の洗浄液ではいずれも優れたＰＳＬ除去性が得られた。また、アルミニウム防食および泡立ち防止の点についても良好な特性が得られた。一方、ＨＬＢ値の小さい非イオン界面活性剤を単独で使用した比較例１では、ＰＳＬ除去性が全く得られず、逆にＨＬＢ値の大きい非イオン界面活性剤を単独で使用した比較例２と、陰イオン界面活性剤を単独で使用した比較例２では、多量の泡立ちが発生する問題が生じた。また、中性の水素溶解水を用いた比較例４では充分なＰＳＬ除去性が得られず、塩基性に調整した水素溶解水を用いた比較例５では、アルミニウムの腐食が生じた。
【００６４】
【表３】

【００６５】
以上の結果から、少なくともＨＬＢ値の小さい非イオン界面活性剤とＨＬＢ値の大きい非イオン界面活性剤とを含む２種以上の非イオン界面活性剤を組み合わせることにより、両者の欠点を補完することができ、１種の非イオン界面活性剤や陰イオン界面活性剤、機能水を用いる場合に比べて総合的な洗浄性能が向上することが確認された。
【００６６】
以下の実施例５〜８では、酸化還元電位調整剤として水素以外のものを用いて洗浄を行った。実施例５〜８においては、酸化還元電位調整剤として各実施例記載の水素以外のものを用いそれぞれに記載のＯＲＰに調整したこと以外は、洗浄液調製条件ならびに実験および評価方法は実施例１と同様にした。
【００６７】
［実施例５］
酸化還元電位調整剤としてヒドロキシルアミンを用いた。ＯＲＰは−２８８ｍＶであった。
【００６８】
［実施例６］
酸化還元電位調整剤としてアスコルビン酸を用いた。ＯＲＰは−１００ｍＶであった。
【００６９】
［実施例７］
酸化還元電位調整剤として酸素を用いた。ＯＲＰは４２７ｍＶであった。
【００７０】
［実施例８］
酸化還元電位調整剤として次亜塩素酸を用いた。ＯＲＰは６１２ｍＶであった。
【００７１】
実施例５〜８の結果を、表４にあわせて示す。実施例５〜８の洗浄液では、何れも実施例１の酸化還元調整剤に水素を用いた場合と同等のＰＳＬ除去性が得られ、水素電極基準（２５℃）の酸化還元電位が略−１２００〜１００ｍＶ、略４００−１２００ｍＶの範囲であれば良好な洗浄性能が得られることを確認した。
【００７２】
【表４】

【００７３】
以下の実施例９〜１０および比較例６では、実施例１乃至８および比較例１乃至５で評価したアルミニウム配線材料に替えて、低抵抗配線材料として検討されている銅配線材料に対する腐食性を調べた。
【００７４】
［実施例９］
洗浄液中での銅配線の腐食性を調べるため、銅メッキ薄膜を成膜した５センチ四方のシリコン基板を表１に示す調製条件の洗浄液に浸漬し、腐食の程度を評価した。洗浄液の温度は室温（２２〜２４℃）とし、基板を１時間浸漬後、洗浄液中に溶解した銅成分の濃度を黒鉛炉原子吸光分析装置を用いて分析することにより評価した。
【００７５】
銅メッキ膜は、純水に浸漬しただけでも銅成分が溶出する。そこで、各洗浄液中での溶解量を純水中での溶解量に対する比で評価した。これにより、銅の腐食性に対して厳しい評価を行うことができる。
５・・・・・銅の溶解量比が２０％未満
４・・・・・ 〃 ２０％以上５０％未満
３・・・・・ 〃 ５０％以上７０％未満
２・・・・・ 〃 ７０％以上９０％未満
１・・・・・ 〃 ９０％以上
【００７６】
［実施例１０］
本実施例では、実施例３で使用した洗浄液（ＨＬＢの小さい非イオン界面活性剤（モノウラリン酸ソルビタン）、ＨＬＢの大きい非イオン界面活性剤（モノウラリン酸デカグリセル）に陰イオン界面活性剤（ポリオキシエチレンアルキルエーテル硫酸トリエタノールアミン）を添加した洗浄液）を用いた。評価は実施例９と同様に行った。
【００７７】
［比較例６］
本比較例では、洗浄液として、純水に水素ガスを溶解させた後、ｐＨを１０に調整した水素溶解水（ｐＨ１０、ＯＲＰ：−６２０ｍＶ）を用いた。評価は実施例９と同様に行った。
【００７８】
実施例９〜１０および比較例６の結果を、表５に示す。実施例９および１０では、銅の溶解量は純水比で２０％未満に抑えられ、ほぼ腐食が防止できた。これに対して従来の水素溶解水を用いた比較例６では、純水比で著しい銅の溶出量が認められ、腐食が生じた。
【００７９】
【表５】

【００８０】
以下の実施例１１〜１２では、本発明の洗浄組成物を用いて洗浄後、さらにＨＬＢ値が１５〜２０の非イオン界面活性剤、または陰イオン性界面活性剤を用いて洗浄を行った。
【００８１】
［実施例１１］
実施例１の洗浄後、さらにモノラウリン酸デカグリセル（非イオン界面活性剤、ＨＬＢ値：１５．５）を０．００５％含む水溶液（ｐＨ７）で洗浄を行った。洗浄後のシリコン基板のＰＳＬ除去性について実施例１と同様の評価を行った。
【００８２】
［実施例１２］
実施例１の洗浄後、ポリオキシエチレンアルキルエーテル硫酸トリエタノールアミン（陰イオン界面活性剤）を０．００１％含む水溶液（ｐＨ９）で洗浄を行った。洗浄後のシリコン基板のＰＳＬ除去性について実施例１と同様の評価を行った。
【００８３】
実施例１１〜１２の結果を、表６に示す。実施例１１〜１２の洗浄液を用いて２段階の洗浄を行うことにより、実施例１の洗浄のみに比べて、いずれもＰＳＬ除去性が向上した。
【００８４】
【表６】

【００８５】
［実施例１３］
本実施例では、低抵抗金属膜としてＣｕ膜、低誘電率膜として多孔質ＭＳＱ（メチルシルセスキオキサン）膜を用いて素子を形成し、素子形成過程で生じたパーティクル汚染（アッシング残渣およびエッチング残渣）の洗浄を行った。本実施例で使用した洗浄液の調製条件を表７に示す。当該洗浄液に関し、後述の方法によりパーティクル（残渣）除去性と、Ｃｕ膜に対する腐食性、ＭＳＱ膜の変質に対する評価を行い、洗浄液の泡立ちの程度ならびに総合的な洗浄性能評価については実施例１と同様に行った。
【００８６】
【表７】

【００８７】
（パーティクル（残渣）除去性評価）
本実施例では、一般的なシングルダマシンプロセスにより素子を形成し、素子形成後にビアホール内に生じたアッシング残渣およびエッチング残渣を、実施例１と同様の方法により洗浄した。洗浄後、ＳＥＭ（走査型電子顕微鏡）を用いて素子のビアホール内を断面観察し、パーティクル（残渣）除去性を評価した。評価基準は以下の通りとした。
５・・・・・残存が全く認められなかった
４・・・・・残存が僅か（１割未満）に認められる
３・・・・・残存が２〜５割程度認められる
２・・・・・残存が６〜８程度認められる
１・・・・・ほとんどが残存している
【００８８】
（Ｃｕ膜に対する腐食性の評価）
素子形成後、ビア底に露出したＣｕ膜の表面をＳＥＭにより観察し、腐食の程度を評価した。以下の基準により腐食程度を評価した。
５・・・・・ほとんど変化が認められない
４・・・・・わずかに腐食が認められる
３・・・・・部分的な腐食が認められる
２・・・・・半分以上に腐食が認められる
１・・・・・全体が腐食しているか全て溶解
【００８９】
（ＭＳＱ膜の変質に対する評価）
素子形成後、ビアホール側壁に露出したＭＳＱ膜の表面を、ＳＥＭを用いて変質の程度を観察した。また、ＭＳＱ膜の誘電率を測定し、特性劣化の程度を評価した。なお、誘電率の測定に当たっては、膜の細孔内に吸着した水分が大きく影響するため、ＭＳＱ膜を２５０℃で５分間加熱し、乾燥させてから測定を行った。評価基準は以下の通りとした。
５・・・・・ほとんど変化が認められない
４・・・・・わずかに変質が観察される。または、わずかに誘電率の上昇が認められる
３・・・・・部分的な変質が観察される。または、多少の誘電率の上昇が認められる
２・・・・・半分以上に変質が観察される。または、明らかに誘電率の上昇が認められる
１・・・・・全体が腐食している。または、著しい誘電率の上昇が認められる
【００９０】
【表８】

【００９１】
実施例１３の結果を、表８に示す。実施例１３では、アッシング残渣およびエッチング残渣のほとんどが除去された。また、Ｃｕ膜およびＭＳＱ膜に対しても充分な防食効果が認められ、泡立ちもほぼ抑制された。すなわち、素子形成基板の洗浄において優れた効果があることが認められた。
【００９２】
［実施例１４］
本実施例では、洗浄中における洗浄組成物の濃度を一定範囲に維持するために、図５に示す濃度制御手段を備えた洗浄装置を使用した。本装置では、洗浄液は、貯留タンク１５に貯えられ、循環ポンプ１６によりタンク内を循環する。貯留タンク１５には、洗浄液の状態をモニターするため、温度計１７、ｐＨメーター１８、水位計１９、電気伝導度計２０、比重計２１、ヒーター２２が具備されている。また、界面活性剤や各種添加剤、ｐＨ調整剤などの洗浄剤が、薬液タンク２３、２４、２５に貯留され、送液ポンプ２６，２７，２８により貯留タンク１５に送られる。なお、洗浄剤の送液量やタイミングは、上記１７〜２２でモニターされた洗浄液の状態に応じて、洗浄液の濃度が一定範囲となるように制御部（不図示）により制御される。一方、基板洗浄時において、洗浄液は貯留タンク１５から基板洗浄部２９に送液ポンプ３０によって送られ、基板（不図示）に供給される。また、必要に応じて、洗浄後の洗浄液は、ポンプ３１により排水もしくはフィルター３２を介して貯留タンク１５に回収される。
【００９３】
上記洗浄液について、洗浄中の濃度変動について評価した結果を図６に示した。本実施例においては、洗浄液の濃度変動（測定値／設定値比）は±５％以内であり、ほぼ一定に維持された。
【００９４】
【発明の効果】
本発明によれば、デバイス基板の洗浄において、配線や絶縁膜、容量膜等に用いられる金属膜や金属化合物膜の腐食や溶解を防止しつつ、またウォーターマークの発生を防止して、材料の特性を劣化させることなく、基板上のパーティクル等の汚染を極めて効果的に洗浄することができる。
【００９５】
その理由は、１分子中に少なくとも１つの水酸基を有し、ＨＬＢが３以上１２未満の非イオン界面活性剤と、ＨＬＢが１２以上２０以下の非イオン界面活性剤とを含むＨＬＢ値の異なる２種以上の非イオン界面活性剤を組み合わせることにより、１種の非イオン界面活性剤を単独で用いる場合の欠点を補完することができるからである。また、酸化還元電位調整剤により酸化還元電位を水素電極基準（２５℃）で略−１２００ｍＶ〜１００ｍＶ、略４００ｍＶ〜１２００ｍＶに調整することにより洗浄性能を高めることができるからである。
【００９６】
また、洗浄組成物にアルコールや陰イオン界面活性剤、フッ化物イオン、ベンゾトリアゾール又はその誘導体、キレート化剤を添加したり、上記洗浄組成物による洗浄の後、ＨＬＢが１５以上２０以下の非イオン界面活性剤、もしくは陰イオン界面活性剤を含有する水溶液で洗浄することにより、更に洗浄性能を高めることができるからである。そして上記洗浄組成物を用いることにより、従来の洗浄液では対応できなかった低抵抗金属や低誘電率材料、強誘電材料等の新規材料に対しても洗浄が可能となり、デバイスの性能や生産性を向上させることができる。
【図面の簡単な説明】
【図１】本発明の洗浄組成物のＨＬＢ値と洗浄効果の関係を示す図である。
【図２】本発明の洗浄組成物の好適な酸化還元電位を示す図である。
【図３】本発明の洗浄組成物のパーティクル除去性及び金属の腐食度とｐＨとの関係を示す図である。
【図４】本発明の基板洗浄装置の一実施例を示す図である。
【図５】本発明の基板洗浄装置の一実施例を示す図である。
【図６】本発明の基板洗浄装置による洗浄組成物の濃度変動の抑制効果を示す図である。
【符号の説明】
１ 脱気装置
２ 気体透過膜
３ 貯留タンク
４ 貯留タンク
５ 貯留タンク
６ ポンプ
７ ポンプ
８ ポンプ
９ インラインミキサー
１０ バイパス
１１ ノズル
１２ 基板
１３ アーム部
１４ 回転支持台
１５ 貯留タンク
１６ 循環ポンプ
１７ 温度計
１８ ｐＨメーター
１９ 水位計
２０ 電気伝導度計
２１ 比重計
２２ ヒーター
２３ 薬液タンク
２４ 薬液タンク
２５ 薬液タンク
２６ 送液ポンプ
２７ 送液ポンプ
２８ 送液ポンプ
２９ 基板洗浄部
３０ 送液ポンプ
３１ ポンプ
３２ フィルター[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cleaning composition for a device substrate containing a nonionic surfactant and having a controlled oxidation-reduction potential, particularly a cleaning composition for cleaning a device substrate having an exposed metal or metal compound surface, and the cleaning composition. The present invention relates to a cleaning method and a cleaning apparatus using a material.
[0002]
[Prior art]
In an LSI or LCD manufacturing process, a high-concentration acid or basic chemical solution has been used for cleaning in order to obtain a highly clean device substrate surface. However, with the increasing integration and density of devices, not only high cleanability but also high control of damage such as substrate surface roughness and deterioration due to corrosion and melting is required. . Further, if the cleaning component remains after cleaning, it may adversely affect the subsequent film formation, and it has been required that the cleaning component can be easily removed by rinsing with ultrapure water or the like. Further, from the viewpoint of reducing the cost of chemicals and wastewater treatment and the reduction of environmental load, it has been required to dilute the cleaning liquid.
[0003]
In order to solve these problems, functional water such as electrolyzed water generated by electrolysis of water and gas-dissolved water obtained by dissolving a gas in pure water has been used. The cleaning method using gas-dissolved water is a method of cleaning by jetting a reducing gas or an oxidizing gas (for example, see Patent Document 1). According to this method, contamination can be effectively cleaned while preventing damage to the object to be cleaned due to ultrasonic cavitation. Such cleaning with functional water is an excellent method with low cost and low environmental load, and with less roughness of the substrate surface after cleaning. However, high requirements for cleanability in LSI and LCD processes can be sufficiently achieved. The scope of application is limited. Therefore, a method of adding a small amount of an additive such as an acid or a basic substance for the purpose of improving the cleaning effect of functional water has been studied (for example, see Patent Document 2). In many cases, a basic substance is added to make functional water basic. The cleaning mechanism is based on the action that particles are detached from the substrate by lift-off or physical cleaning power and are prevented from re-adhering by electrostatic repulsion. In the method described in Patent Document 2, the alkaline surfactant is hydrogenated. By diluting with dissolved water and adjusting the oxidation-reduction potential to -300 mV or less, an excellent particle removing effect can be obtained even when the surfactant concentration is as low as 0.05% or less.
[0004]
On the other hand, in the cleaning of metal materials, a technique for preventing corrosion of the material at the time of cleaning is required, and an anticorrosive or a surfactant is added to the cleaning liquid to make the surface hydrophobic, thereby inactivating the corrosion reaction. Methods are known (see, for example, Patent Documents 3 and 4). In the method described in Patent Document 3, by adding a nonionic surfactant having an HLB of 9 to 16 to an aqueous detergent containing a specific ester compound and an anionic surfactant, water repellency is imparted to the metal surface and rust The occurrence is prevented. The cleaning agent described in Patent Document 4 is an aqueous cleaning agent comprising a nonionic surfactant of HLB 4 to 16, a solvent such as lower alcohol, and a rust inhibitor such as benzotriazole, and is used for cleaning metal parts. Has rust and corrosion resistance. This HLB (Hydrophile-Lipophile Balance) is used as a measure of the hydrophilicity / hydrophobicity of a nonionic surfactant, and it is known that characteristics and applications differ depending on the HLB value (for example, see Non-Patent Document 1). ). Generally, the lower the HLB value, the stronger the hydrophobicity and the poorer the water solubility. According to Non-Patent Document 1, when HLB is 3 to 6, it is used for emulsification of W / O type, when HLB is 7 to 9, it is used for enhancing wettability, and when HLB is 8 to 15, O / W type emulsification is used. It is described that HLB is used for washing when HLB is 13 to 15, and is used for solubilization when HLB is 15 to 18.
[0005]
As a method of enhancing the anticorrosion effect of functional water, there is a method of using a cleaning agent comprising hydrogen peroxide water, ozone water or electrolytic anode water, an inorganic acid or a basic substance, and a complexing agent or a surfactant. (For example, see Patent Document 5).
[0006]
[Patent Document 1]
JP-A-11-265870 (pages 2-6, FIG. 1)
[Patent Document 2]
JP 2001-70898 A (page 3-7)
[Patent Document 3]
JP-A-7-11467 (pages 2-7)
[Patent Document 4]
JP-A-8-283797 (pages 3-7)
[Patent Document 5]
JP 2001-308052 A (pages 2 to 5)
[Non-patent document 1]
Fumio Kitahara, Yatsukatsu Tamai, Shigeo Hayano, Ichiro Hara, eds., “Physical Properties, Applications, and Chemical Ecology” (Kodansha, 1979), pp. 24-27.
[0007]
[Problems to be solved by the invention]
In recent years, new materials such as low resistance metals, low dielectric constant materials, and ferroelectric materials have been introduced as materials for wiring for LSIs and LCDs, interlayer insulating films, and capacitance films. However, while excellent device characteristics can be obtained by controlling the composition and film thickness, etc., because of its high chemical reactivity, it easily reacts with the cleaning solution to easily cause corrosion, dissolution, and alteration. There has been a demand for compatibility between advanced cleaning properties, low damage and low residual properties, and further enhancement of these performances.
[0008]
However, when the anticorrosion method using the anticorrosion agent or the surfactant described in Patent Document 3 or Patent Document 4 is applied to functional water, there is a problem that the original purpose of removing particles is reduced. . In the related art in which the surface of the object to be cleaned is made hydrophobic and the chemical reaction with the cleaning liquid is suppressed, the enhanced adhesion of the particles to the surface is considered to be the cause of the decrease in the particle removability. Furthermore, since the concentration of the nonionic surfactant required for obtaining the anticorrosion performance is high, there is a problem that the detergent component remains on the substrate surface after the cleaning and the cost and the wastewater treatment load increase. Effect is lost. In addition, when the method described in Patent Document 5 is applied to cleaning of a new material, deterioration and composition deviation of the film material, and dissolution and corrosion of the film occur, and it is impossible to prevent corrosion of the new material.
[0009]
In this way, there is a trade-off between utilizing the properties of functional water such as low cost, low environmental load, and low persistence, improving the cleaning performance with additives, and improving the anticorrosion performance with an anticorrosive. It has been difficult to effectively exhibit the properties of each component in washing new materials.
[0010]
The present invention has been made in view of the above circumstances, and its main purpose is to prevent corrosion and dissolution of metals and metal compounds used for wiring, insulating films, and capacitor films in cleaning device substrates. A cleaning liquid for a device substrate, which can effectively clean particles and the like on a substrate without deteriorating device characteristics, and has excellent drainage treatment properties and recyclability, a cleaning method and a cleaning apparatus using the same. Is to provide.
[0011]
[Means for Solving the Problems]
As described above, the conventional cleaning of particles with functional water mostly uses basic functional water, but basic functional water causes corrosion and dissolution of device materials. In fact, it shows strong corrosiveness and solubility for metals and metal compounds used as new materials. Further, the conventional anticorrosion method is to make the surface hydrophobic by adding an anticorrosive or a surfactant, thereby suppressing the reaction with the cleaning solution to prevent corrosion. Is enhanced, and conversely, the particle removal property is reduced.
[0012]
Therefore, when cleaning a device substrate containing a new material such as a metal or a metal compound, corrosion and dissolution can be prevented by a method different from the method of hydrophobizing the surface, and functional water prepared to be acidic or basic is inherently possessed. It is preferable that the washing action can be used effectively. Further, it is desirable that the cleaning performance is high, and it is more desirable that the additive for improving the cleaning performance and the anticorrosion performance has excellent biodegradability and low environmental load. The present invention has been made based on the above points.
[0013]
According to the present invention for solving the above-mentioned problems, a device substrate having a metal film or a metal compound exposed to a non-ionic surfactant having a specific molecular structure and an HLB value and having a controlled oxidation-reduction potential. Cleaning is performed using an aqueous solution. Thereby, particle contamination attached to the substrate surface can be effectively removed.
[0014]
Generally, a metal film or a metal compound exhibits strong corrosiveness to a basic cleaning solution. However, in the cleaning composition of the present invention, a nonionic surfactant having at least one hydroxyl group in one molecule and having an HLB of 3 or more and less than 12 and a nonionic surfactant having an HLB of 12 or more and 20 or less are used. By containing it in the cleaning solution, an excellent anticorrosion property against a metal film or a metal compound film is obtained. Further, the surface state of the substrate at the time of cleaning is hydrophilic, whereby the adhesion of particles is effectively reduced, and the particle removal effect inherent to functional water is effectively obtained. This indicates that anticorrosion and cleaning are performed based on a mechanism different from the conventional anticorrosion method and cleaning method. That is, as described above, the conventional anticorrosion method makes the surface hydrophobic and suppresses the reaction with the cleaning solution to prevent corrosion. In the present invention, however, the hydrophilization and anticorrosion of the substrate surface are simultaneously performed. In order to achieve this, particles can be effectively removed, and an effective anticorrosion effect is obtained even in basicity.
[0015]
Despite the fact that the cleaning composition of the present invention contains a strong nonionic surfactant having an HLB value of 3 or more and less than 12 which is generally not suitable for cleaning, the substrate after cleaning has a hydrophilic property suitable for particle removal. Surface. Although the formation mechanism of this hydrophilic anticorrosive surface is not always clear, the presence of a plurality of nonionic surfactants having a specific molecular structure having different HLB values allows the surfactant to be selectively deposited on the substrate surface. This is probably due to multimolecular adsorption, that is, a non-ionic surfactant having a hydrophilic HLB value of 12 or more and less than 20 was further adsorbed on the non-ionic surfactant having a strong hydrophobicity adsorbed on the substrate. Such selective adsorption of the surfactant on the substrate is unlikely to occur at the same time as the adsorption rate and the adsorption orientation of each surfactant molecule are not extremely different, but in the present invention, By coexisting a plurality of nonionic surfactants having hydroxyl groups in the molecular structure and having different HLB values, the above-described specific surface control could be realized.
[0016]
Furthermore, as a result of conducting various experiments, the use of a cleaning solution having a pH of 5 to 12 with an oxidation-reduction potential of about -1200 mV or more and 100 mV or less or about 400 mV or more and 1200 mV or less based on a hydrogen electrode (25 ° C.) has an effect of removing particles. It was found to be significantly improved. In other words, experiments have shown that, in addition to the action of the above-mentioned surfactant, the control of the oxidation-reduction potential of the aqueous solution produces excellent synergistic effect on particle removal. It was issued. Although the cleaning mechanism by controlling the oxidation-reduction potential is not clear, it is considered that the application of a potential difference suitable for cleaning to the surface of the substrate or the particle effectively acts to remove the particle contamination.
[0017]
After the substrate is cleaned using the cleaning composition of the present invention, the particles are removed by performing cleaning using a dilute aqueous solution of a nonionic surfactant or an anionic surfactant having an HLB value of 15 or more and 20 or less. It was found that the properties were further improved. Such two-stage cleaning is particularly effective when it is desired to further improve the removability of particles. A dilute aqueous solution of a nonionic surfactant or an anionic surfactant having an HLB value of 15 or more and 20 or less used in the main cleaning is difficult to obtain an anticorrosion effect, but is excellent in hydrophilizing the substrate. The hydrophilicity of the anticorrosion film formed on the surface can be further enhanced, and even the slight particle contamination that cannot be completely removed by washing can be almost completely removed.
[0018]
In the present invention, as described above, washing is performed using a neutral to basic aqueous solution containing a plurality of nonionic surfactants having a specific molecular structure and different HLB values and having a controlled oxidation-reduction potential. As a result, the respective effects are synergistically exhibited, and cleaning of a new material, which has been conventionally difficult, has become possible. In other words, the effects that had been trade-off so far, such as the corrosion prevention of the material, the hydrophilicity of the surface, and the improvement of the particle removal property by adjusting the pH, were simultaneously realized by controlling the structure and type of the surfactant and the conditions of the cleaning solution. Thereby, in the cleaning composition and the cleaning method of the device substrate in the present invention, the particle removing property having the basic functional water, the anticorrosive action of the surfactant, and the reduction of the cost and the environmental load based on the fact that the component is diluted are reduced. The effect is maximized.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is characterized by cleaning of particle contamination attached to a device substrate. Therefore, the device substrate in the present invention is not particularly limited as long as it is a substrate for manufacturing a device. ₂ A substrate formed of a substrate, an SOI substrate, a III-V compound semiconductor substrate, a glass substrate, a quartz substrate, a plastic substrate, or the like can be used.
[0020]
The metal film and metal compound film in the present invention refer to thin films used for device wiring, low dielectric constant films, high dielectric constant films, and the like. Various materials can be used as the thin film material. Specifically, the thin film material is made of Ba, Sr, Hf, Zr, Ta, Al, Ti, W, Pb, Mo, Si, Co, Bi, Cu, and Ag. Examples include metals, alloys, oxides, and silicide compounds containing one or more materials selected from the group. Each element has a value of electronegativity close to or smaller than that of Si, and the oxidation-reduction reaction progresses and corrodes the acid or basic cleaning solution used for etching and cleaning the conventional silicon substrate. And dissolution may occur, and the effect of the present invention can be more remarkably obtained.
[0021]
The nonionic surfactant in the present invention may be any as long as it can be dissolved in pure water. However, it is preferable to select a nonionic surfactant having one or more hydroxyl groups in one molecule to obtain a metal or metal compound surface. To form an anticorrosion film. Furthermore, by using a nonionic surfactant in which more hydroxyl groups are arranged in a branched state in the molecule, it is possible to improve the adsorptivity to a substrate surface or a metal or a metal compound. In addition, nonionic surfactants have the advantage of being less toxic to living organisms, having less effect on the environment, and lowering the surface tension of the washing solution even at low concentrations, and increasing permeability, compared to ionic surfactants. is there. Furthermore, since it is superior in foam suppressing property as compared with an ionic surfactant and has no action of changing pH, the controllability of the cleaning liquid in the process is very good. In addition, since it has an aggregation point (temperature) called a cloud point, there is an advantage that the concentration treatment can be easily performed even in wastewater treatment. In addition, the excellent emulsifying action of the nonionic surfactant has an effect of easily removing organic contaminants such as oils and fats attached to the substrate surface.
[0022]
As the nonionic surfactant in the present invention, for example, polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene alkyl phenyl ethers such as polyoxyethylene nonyl phenyl ether, polyethylene glycol fatty acid ester, polyglycerin fatty acid Polyhydric alcohol fatty acid esters such as esters, pentaerythritol fatty acid esters, sorbitan fatty acid esters, and sorbite fatty acid esters, and their fluorine oxide surfactants such as ethylene oxide adducts, fluorinated alkyl esters, and perfluoroalkyl ethylene oxide Alternatively, they are used as a mixture. In any case, a good cleaning effect and a high anticorrosion effect can be obtained due to the excellent adsorption to the substrate surface. However, by selecting a particular type among the above, more advantages can be obtained. For example, a nonionic surfactant containing an ester bond in the molecular structure is excellent in biodegradability, and has an advantage that the cost for wastewater treatment and the burden on the environment can be reduced. In addition, by selecting a nonionic surfactant having a molecular structure with fewer side chain alkyl groups, biodegradability can be improved. Specific examples of such a nonionic surfactant include compounds having chemical structures exemplified by the following general formulas [1], [2], [3], and [4].
Embedded image

(At least one of X1 to X4 is an OH group, and the rest represents OCOR. R represents a hydrocarbon group having 5 to 17 carbon atoms.)
Embedded image

(At least one of X1 to X5 is an OH group, and the rest is OCOR. R represents a hydrocarbon group having 5 to 17 carbon atoms.)
Embedded image

(At least one of X1 to X5 is an OH group, and the rest is OCOR. R represents a hydrocarbon group having 5 to 17 carbon atoms. N represents a number of 2 to 10.)
Embedded image

(At least one of X1 to X4 is an OH group, and the rest represents OCOR. R represents a hydrocarbon group having 5 to 17 carbon atoms.)
[0023]
X in the general formulas [1] to [4] is a polar part represented by the chemical formula of OH or OCOR, and a polar part to which ethylene oxide is arbitrarily added can be used. R is a hydrocarbon group, and preferably has 5 to 17 carbon atoms from the viewpoints of dispersibility in water, foam suppression, and easy rinsing. Further, n shown in the general formula [3] is a number related to the degree of polymerization of the glycerin fatty acid ester, and is preferably in the range of 2 to 10 from the viewpoint of viscosity and water solubility. Specific examples of the compound represented by the general formula [1] include sorbitan monocaprate, sorbitan monolaurate, sorbitan monopartimate, and sorbitan trioleate. Specific examples of the compound represented by the above general formula [2] include the above-mentioned general formula [3] such as POE (6) sorbit monolaurate, POE (60) sorbit tetrastearate, and sorbit tetraoleate. Specific examples of the general formula [4] include pentaerythritol tetra-2-ethylhexanoate, pentaerythritol monopalmitate, and the like. No.
[0024]
The cleaning composition of the present invention preferably contains at least two or more nonionic surfactants having different HLB values. This results in the association of surfactant molecules, increasing the water solubility of the lower HLB surfactant and synergistically obtaining the properties of each surfactant. Further, by using a mixture of a nonionic surfactant having an HLB of 3 or more and less than 12 and a nonionic surfactant having an HLB of 12 or more and 20 or less, good dispersibility of an aggregate of surfactant molecules can be obtained. As well as being obtained, a hydrophilic substrate surface having excellent anticorrosion properties can be formed. Further, there is obtained an advantage that foaming can be suppressed.
[0025]
FIG. 1 shows the classification of the use of the nonionic surfactant described in Non-Patent Document 1 and the effect on the device substrate cleaning found in the present invention together with the HLB value. In general, a nonionic surfactant having an HLB of 3 or more and less than 12 has poor water solubility, separates or suspends from water in water, remains on a substrate, and has an action of promoting adhesion of particles. Therefore, they are hardly used for cleaning device substrates. However, HLB surfactants in this range are characterized in that uniform adsorption orientation is unlikely to occur at the bubble interface and that the stability of the bubbles is lost, so that the surfactant is excellent in bubble suppression. In addition, when it is adsorbed on a solid surface, it is characterized in that an excellent anticorrosion effect is obtained by the hydrophobic action of the surfactant molecule itself. On the other hand, a nonionic surfactant having an HLB of 12 or more and 20 or less has high water solubility, and has an effect of hydrophilizing the surface even at a low concentration to reduce the adhesion of particles. On the other hand, it has a strong effect of stabilizing bubbles and generates strong bubbling, so that it is very difficult to handle in a device substrate cleaning process and is avoided.
[0026]
As described above, each nonionic surfactant has advantages and disadvantages. In the present invention, a nonionic surfactant having an HLB of 3 or more and less than 12 and a nonionic surfactant having an HLB of 12 or more and 20 or less coexist. It has been found that the above-mentioned novel concept solves each problem and at the same time synergistically provides excellent cleaning characteristics for cleaning the device substrate. In order to further enhance the combined effect of the nonionic surfactant of the present invention, it is preferable to include a nonionic surfactant having an HLB of 3 to 10 and a nonionic surfactant having an HLB of 13 to 20. It is suitable, and a more excellent anticorrosion effect can be obtained.
[0027]
The content of the nonionic surfactant is preferably about 0.0001 to 0.1% by mass, more preferably about 0.0005 to 0.05% by mass, based on the cleaning composition. If the concentration is too low, a sufficient cleaning effect cannot be obtained, and corrosion and dissolution of metals and dielectrics occur.On the other hand, if the concentration is too high, a large amount remains on the substrate to cause other contamination, The cost of wastewater treatment increases.
[0028]
Further, the cleaning composition of the present invention can contain an anionic surfactant. The anionic surfactant has an effect of charging the surfaces of the substrate and the particles with the same sign, and thus has the effect of facilitating the removal of particle contamination and the effect of preventing the particles once removed from being reattached. The anionic surfactant used in the present invention is not particularly limited, but preferably does not contain a metal such as sodium. This is because when sodium is contained in the anionic surfactant, it is adsorbed or diffused on the substrate and causes deterioration of the electrical characteristics of the device. In addition, anionic surfactants are inferior to nonionic surfactants in terms of toxicity to the living body and foam suppressing properties. However, the anionic surfactant is used at a concentration of about 0.0001 to 0.01% by mass to minimize the adverse effect. It is possible to make the most of the original excellent cleaning properties while keeping the cleaning performance low.
[0029]
Further, the cleaning composition of the present invention can contain an alcohol. Alcohol has both a polar part and a non-polar part in a molecule, and therefore easily mixes not only with water but also with a surfactant having a small polarity. For this reason, the dispersibility of the poorly water-soluble surfactant in water can be enhanced, and the effect of reducing the residue of the surfactant on the substrate after cleaning can be obtained. As the alcohol used in the present invention, polyhydric alcohols having low volatility such as propylene glycol, ethylene glycol and polyethylene glycol are preferable in terms of the stability of the cleaning solution. If no particular problem arises, volatile alcohols such as ethanol and propanol can be used. The alcohol can be arbitrarily added according to the concentration of the surfactant.
[0030]
The oxidation-reduction potential of the cleaning composition of the present invention is preferably about -1200 mV to 100 mV, or about 400 mV to 1200 mV (based on a hydrogen electrode, 25 ° C.). FIG. 2 shows the results obtained by adjusting the oxidation-reduction potential of pure water using various oxidation-reduction potential regulators and examining the particle removability. In this experiment, no surfactant was added to examine only the effect of the redox potential, and the solution was adjusted to pH 7 using a buffer to avoid the influence of pH, and washing was performed. went. As can be seen from FIG. 2, the particle removability strongly depends on the value of the oxidation-reduction potential, and from about -1400 mV to about -100 mV, and from about 200 mV to about 1000 mV on the basis of the silver / silver chloride electrode (25 ° C.). In the region up to the above, the particle removal rate became approximately 50% or more, and the particle removal property was significantly improved. That is, the range of the oxidation-reduction potential suitable for particle removal was a range of about -1200 mV or more and 100 mV or less and about 400 mV or more and 1200 mV or less based on the hydrogen electrode (25 ° C.). The range where the oxidation-reduction potential is approximately 100 mV to 400 mV (based on the hydrogen electrode) is the range of the oxidation-reduction potential of ordinary water (water in which air is dissolved at normal temperature and normal pressure). It was confirmed that the particles exhibited an effect of removing particles. A cleaning composition having an oxidation-reduction potential in this range gives a potential difference suitable for cleaning to the surface of a substrate or a particle, and effectively acts to remove particle contamination.
[0031]
The oxidation-reduction potential adjusting agent for adjusting the oxidation-reduction potential of the cleaning composition of the present invention to approximately -1200 mV or more and 100 mV or less or approximately 400 mV or more and 1200 mV or less based on a hydrogen electrode (25 ° C.) is obtained by electrolysis of pure water. Cathode water or anodic water can be used.
[0032]
Hydrogen gas, hydroxylamine or a salt thereof, ethylamine, propylamine as an oxidation-reduction potential adjusting agent for adjusting the oxidation-reduction potential of the cleaning composition of the present invention to approximately −1200 mV or more and 100 mV or less based on a hydrogen electrode (25 ° C.) Amines such as ammonia, carboxylic acids such as ammonia, tetramethylammonium hydroxide, glyoxylic acid, and oxalic acid; aldehydes such as formaldehyde and acetaldehyde; saccharides such as thiosulfate, dithionite, formic acid, ascorbic acid, and glucose. Can be used. When a salt is used, a salt that does not adversely affect the characteristics of the device is preferable, and a metal-free salt such as an ammonium salt is particularly preferable. In any case, the oxidation-reduction potential can be reduced. However, more advantages can be obtained by selecting particular ones of the above. For example, when a cleaning composition containing one or more components selected from the group consisting of hydrogen gas, amine, and carboxylic acid is used, the oxidation-reduction potential can be reduced even with a very small amount of addition. Another advantage is that the rinsing step after washing can be simplified. In particular, when hydrogen is used as the oxidation-reduction potential adjuster, pH fluctuation due to the addition does not occur, the concentration of the cleaning composition can be easily controlled in the process, and the load on the wastewater treatment can be significantly reduced.
[0033]
The oxidation-reduction potential adjusting agent for adjusting the oxidation-reduction potential of the cleaning composition of the present invention to approximately 400 mV or more and 1200 mV or less on the basis of a hydrogen electrode (25 ° C.) includes oxygen gas, ozone, carbon dioxide, perchloric acid or Oxidizing substances such as salts thereof, hypochlorous acid or salts thereof, peroxides such as aqueous hydrogen peroxide, peroxoacids such as peroxyacetic acid, and salts thereof can be used. When a salt is used, a salt that does not adversely affect the characteristics of the device is preferable, and a metal-free salt such as an ammonium salt is particularly preferable. Whichever one of them is selected, the oxidation-reduction potential can be increased and particles on the substrate can be removed. However, more advantages can be obtained by selecting particular ones of the above. For example, if a cleaning composition containing oxygen or ozone, or both, is used, the oxidation-reduction potential can be increased with an extremely small amount of addition, and while preventing corrosion and dissolution of metals and metal compounds, particles on the substrate can be prevented. Can be effectively removed. Another advantage is that the rinsing step after washing and the drainage treatment can be simplified.
[0034]
The pH of the cleaning composition of the present invention is preferably about 5 to 12. In general, it is considered that the basic region is excellent in particle cleaning properties, while it is considered that corrosion and dissolution of metals and metal compounds hardly occur in a neutral region. FIG. 3 shows the results of examining the relationship between the pH of the cleaning solution and the particle removal properties, and the degree of corrosion of metals and metal compounds. In the basic region from pH around 5, particles and the surface of the substrate are charged to the same sign and electrostatic repulsion occurs, so that the particle removability is greatly improved. On the other hand, although the degree of corrosion of metals and metal compounds varies depending on their physical properties, the degree of corrosion increases significantly from a neutral pH to an acidic pH or from a neutral pH to a basic pH. In the present invention, by selecting the surfactant and the oxidation-reduction potential, it can be used for the purpose of particle cleaning in a wide pH range from acidic to basic, but when the pH is 5 to 12, corrosion prevention of the substrate and removal of particles are performed. Both characteristics are good. Further, when the pH is in the range of 5 to 12, there is also an advantage that a chelating action can be more effectively obtained when a chelating agent is added as an additive. If the pH of the washing solution is higher than 12, there are problems such as hydrolysis of the surfactant and a long rinsing step due to the high salt concentration in the washing solution.
[0035]
Further, the use temperature of the cleaning composition is not particularly limited, and the type of the nonionic surfactant to be used, the type of the additive, and the optimal temperature condition may be selected according to the amount thereof, but in practice, A temperature range of approximately 5-70C is preferred.
[0036]
In the present invention, the cleaning composition may contain fluoride ions and be used for cleaning. Since the cleaning composition to which fluoride ions are added has a function of slightly isotropically etching the surface of a silicon oxide film or the like, it is also possible to remove particle contamination as if buried in a substrate which is generally difficult to remove. . In addition, since it has an action of binding and dissolving metal impurities liberated in the cleaning solution, it has an effect of preventing metal contamination from adhering to the substrate. Further, in forming a pattern, there is also an excellent effect in removing a residue generated after ashing or etching. In addition, when a fluoride ion becomes high concentration, it may cause corrosion of a metal or a metal compound, and the content concentration of the fluoride ion in the present invention is preferably approximately 0.01 to 0.5% by mass. .
[0037]
In the present invention, benzotriazole or a derivative thereof can be contained and used for washing. The cleaning composition to which benzotriazole or a derivative thereof is added forms a protective film on the surface of a metal or a metal compound such as copper, aluminum, or silver, and has an effect of improving corrosion resistance. In general, benzotriazole or a derivative thereof adsorbs on the surface of a metal or metal compound, thereby making the surface hydrophobic and preventing corrosion. In the cleaning composition of the present invention, the metal or metal compound surface on which benzotriazole or a derivative thereof is adsorbed has an action of further hydrophilizing, so that the hydrophilic surface suitable for particle removal is maintained while maintaining the original anticorrosion property. Can be formed. In addition, in terms of preventing the corrosion by making the surface hydrophobic, the action of the nonionic surfactant having an HLB of 3 or more and less than 12 of the present invention is similar to that of the nonionic surfactant having an HLB of 3 or more and less than 12. Alternatively, it can be washed with benzotriazole or a derivative thereof.
[0038]
In the present invention, a chelating agent may be contained and used for washing. The chelating agent refers to a compound having an ability to form a chelate complex with a metal or a metal compound. Specifically, ethylenediaminetetraacetic acid (EDTA), trans-1,2-cyclohexanediaminetetraacetic acid (CyDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), N- (2-hydroxyethyl) ethylenediamine-N , N ', N'-triacetic acid (EDTA-OH) and the like, or salts thereof. When a salt is used, a salt that does not adversely affect the characteristics of the semiconductor device is preferable, and a salt that does not contain a metal such as an ammonium salt is particularly preferable. The content of the chelating agent is preferably about 1 to 10,000 ppm, more preferably about 10 to 1,000 ppm, based on the basic washing liquid. If the concentration is too low, a sufficient chelating effect cannot be obtained. Conversely, if the concentration is too high, organic substances remain on the substrate surface, deteriorating the performance of the semiconductor device, and the disposal of waste liquid is expensive. The use of such a chelating agent can remove metal contamination adhering to the substrate surface and effectively prevent reattachment of the once removed metal contamination.
[0039]
When cleaning is performed in the present invention, it is preferable to apply ultrasonic waves. By doing so, the cleaning effect can be further enhanced. At this time, the frequency of the ultrasonic wave is preferably 800 kHz or more. If the frequency is less than 800 kHz, the wafer may be damaged, and the cleaning effect by the ultrasonic wave may not be sufficiently obtained.
[0040]
When cleaning is performed in the present invention, a gas can be dissolved in the cleaning composition to perform cleaning. The cleaning composition in which the gas is dissolved is slightly degassed at the time of cleaning, and by this action, particles on the substrate are easily lifted off, and an effect of improving removability is obtained. The gas in this case is preferably a gas that exists in a gas state at normal temperature and normal pressure, and specific examples include gases such as hydrogen, nitrogen, oxygen, helium, argon, and carbon dioxide. Of these, hydrogen, oxygen, carbon dioxide and the like also function as oxidation-reduction potential regulators. In addition to the function as the potential adjusting agent, the particle removability can be improved.
[0041]
In the cleaning using the cleaning composition of the present invention, various cleaning methods can be applied. For example, it can be performed by an immersion method, a spin cleaning method, a brush cleaning method, a spray method, a jet spray method, a shower cleaning method, or another mechanical method.
[0042]
After cleaning the substrate using the cleaning composition of the present invention, the cleaning can be further performed using an aqueous solution containing a nonionic surfactant or an anionic surfactant having an HLB value of 15 or more and 20 or less. Thereby, the hydrophilicity of the substrate surface is further improved, and an effect of improving the particle removing property is obtained. The surfactant used for this washing is not particularly limited as long as it is a nonionic surfactant having an HLB value of 15 or more and 20 or less, or an anionic surfactant. By using such a surfactant, the hydrophilicity of the substrate surface can be effectively enhanced even in a low-concentration aqueous solution. Further, the concentration of the surfactant is preferably about 0.0001 to 0.005% by mass. If the concentration is higher than this, not only does bubbling occur, the controllability deteriorates, but also the problem that a surfactant remains on the substrate surface after cleaning occurs. If the concentration is lower than this, the effect of hydrophilizing the substrate surface becomes insufficient, and the concentration control becomes difficult.
[0043]
The substrate cleaning apparatus used for cleaning according to the present invention is preferably provided with a concentration control means for the cleaning composition in order to maintain the concentration of the cleaning composition within a certain range. In particular, since the surfactant is adsorbed on the substrate surface and gradually decreases in concentration with the cleaning treatment, it is preferable to add the surfactant so as to be in an appropriate concentration range while continuously or intermittently measuring the concentration during the cleaning. . For measuring the concentration of the surfactant, a COD meter, a contact angle meter, a surface tensiometer, or the like can be used in addition to a specific gravity meter.
[0044]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
[0045]
FIG. 4 shows an outline of a cleaning apparatus used for cleaning evaluation shown in the following examples. In the present cleaning apparatus, pure water is deaerated in the deaerator 1 and passed through the gas permeable membrane 2. In the gas permeable membrane 2, a gas such as hydrogen is supplied from a gas cylinder (not shown) connected to the outside. A gas such as hydrogen that has passed through the gas permeable membrane 2 is dissolved in the degassed pure water, and gas-dissolved water such as hydrogen-dissolved water is generated. Further, additives such as a surfactant and a pH adjuster are supplied from the storage tanks 3 to 5 by the pumps 6 to 8 and mixed with the gas-dissolved water in the in-line mixer 9. When the gas is not dissolved in the pure water, the pure water is passed through the bypass 10 and mixed with the additive by the in-line mixer 9. The gas-dissolved water (hereinafter, referred to as a cleaning liquid) mixed with the additive is supplied to the substrate 12 through the nozzle 11. The nozzle 11 is provided with an ultrasonic oscillator (not shown), and can apply any sound pressure and frequency to the cleaning liquid. Further, the arm 13 to which the nozzle 11 is fixed can be moved in the horizontal direction on the substrate 12, and the substrate 12 is fixed to the rotation support base 14 and rotates, so that the entire surface of the substrate 12 is evenly cleaned. can do.
[0046]
[Example 1]
Table 1 shows the conditions for preparing the cleaning solution used in this example. Hydrogen was used as a redox potential regulator. With respect to the cleaning liquid, particle removal properties, corrosiveness to aluminum wiring, and the degree of bubbling of the cleaning liquid were evaluated by the method described later, and the performance of the cleaning liquid was comprehensively evaluated based on these results.
[0047]
[Table 1]

[0048]
(Evaluation of particle removal properties)
In this example, in order to examine the particle removing property of the cleaning composition of the present invention, a silicon substrate to which PSL (polystyrene latex) was attached was used. Since PSL is a hydrophobic particle and easily adheres to a hydrophobic silicon substrate and is difficult to remove, the cleaning property can be strictly evaluated.
[0049]
First, a 6-inch silicon substrate was immersed in pure water in which 0.2 μm PSL particles were dispersed, about 3000 to 5000 PSL particles were adhered to the substrate surface, and dried. Thereafter, the substrate was washed by spin cleaning for 30 seconds. During the cleaning, the substrate was rotated at 500 rpm, and irradiated with 1 MHz megasonic while supplying an aqueous solution of the components shown in Table 1 at a flow rate of 1.5 liter per minute. The temperature of the washing solution was room temperature (18 to 20 ° C.).
[0050]
The amount of PSL particles deposited on the silicon substrate before and after cleaning was analyzed using a particle counter. The removability was evaluated according to the following criteria.
5: Particle removal rate is 90% or more
4. The particle removal rate is 80 to less than 90%
3. The particle removal rate is 50 or more to less than 80%
2. The particle removal rate is 10 or more to less than 50%
1 ... Particle removal rate is less than 10%
[0051]
(Evaluation of corrosiveness to aluminum wiring)
Further, in order to examine the corrosiveness of the aluminum wiring in the cleaning liquid, the glass substrate on which the aluminum wiring (thickness: 300 nm) was formed was immersed in the cleaning liquid shown in Table 1, and the degree of corrosion was evaluated. The temperature of the cleaning solution was 40 ° C., the immersion time was 15 minutes, and the shapes of the aluminum wiring before and after the immersion were observed using a scanning electron microscope (SEM). The degree of corrosion was evaluated according to the following criteria.
5: No change is observed
4 ... Slight corrosion is observed
3 ... Partial corrosion is observed
2 ... More than half corrosion is observed
1 ... The whole is corroded or completely dissolved
[0052]
(Method of evaluating the degree of foaming of the cleaning liquid)
Further, in order to examine the degree of foaming of the cleaning liquid, evaluation was performed by a bubbling test. 100 ml of the cleaning solution shown in Table 1 was placed in a 500 ml graduated cylinder, and dry air was bubbled through the diffuser stone at a flow rate of 80 ml per minute for 1 minute. The temperature of the washing solution was room temperature. The amount of foam generated on the liquid surface after aeration was performed for 1 minute, and the amount of foam remaining 1 minute after the aeration was stopped were observed. The degree of foaming was evaluated according to the following criteria.
5: Almost no foaming was observed, and no residual foam was observed.
4. Slight foaming is observed, but little foam remains.
3 ... Some foaming is observed, but little foam remains
2. Slight foaming is observed, and most remains
1 A large amount of foaming was observed, and most of the foaming remained
[0053]
(Comprehensive evaluation of cleaning liquid)
Based on the above evaluations, the cleaning performance of the cleaning liquid was comprehensively evaluated. The evaluation criteria were as follows.
5 ・ ・ ・ ・ ・ ・ ・ Comprehensively excellent for all evaluation criteria
4 ・ ・ ・ ・ ・ has comprehensively sufficient cleaning performance
3 ・ ・ ・ ・ ・ ・ ・ The cleaning performance is slightly insufficient overall
2 ・ ・ ・ ・ ・ ・ ・ Cleaning performance is significantly insufficient in some evaluation criteria
1 .... have almost no cleaning performance
[0054]
[Example 2]
In the present example, a cleaning liquid in which polyoxyethylene nonylphenyl ether (nonionic surfactant, HLB = 19) was added to the components shown in Table 1 at a concentration of 0.001% was used. ORP (redox potential) was -561 mV. The cleaning liquid preparation conditions other than these parameters, and the experiments and evaluation methods were the same as in Example 1.
[0055]
[Example 3]
In this example, a cleaning solution was used in which the propylene glycol in the components shown in Table 1 was changed to polyoxyethylene alkyl ether triethanolamine sulfate (anionic surfactant). ORP was -588 mV. The cleaning liquid preparation conditions other than these parameters, and the experiments and evaluation methods were the same as in Example 1.
[0056]
[Example 4]
In the present example, a cleaning solution in which the components shown in Table 1 were mixed with ammonium fluoride at a concentration of 0.1% was used. ORP was -525 mV. The cleaning liquid preparation conditions other than these parameters, and the experiments and evaluation methods were the same as in Example 1.
[0057]
[Comparative Example 1]
Table 2 shows the preparation conditions of the cleaning solution used in this comparative example. In this comparative example, only the nonionic surfactant having a low HLB (sorbitan monolaurate) among the components of Example 1 was used. The experiment and evaluation method were the same as in Example 1.
[0058]
[Table 2]

[0059]
[Comparative Example 2]
In this comparative example, of the components shown in Table 2, a washing solution in which sorbitan monolaurate was replaced with decaglyceryl monolaurate (nonionic surfactant, HLB = 15.5) was used. The cleaning liquid preparation conditions and the experiment and evaluation methods other than these parameters were the same as in Comparative Example 1.
[0060]
[Comparative Example 3]
In this comparative example, a cleaning liquid in which sorbitan monolaurate was replaced with polyoxyethylene alkyl ether triethanolamine sulfate (anionic surfactant) among the components shown in Table 2 was used. The cleaning liquid preparation conditions and the experiment and evaluation methods other than these parameters were the same as in Comparative Example 1.
[0061]
[Comparative Example 4]
In this comparative example, hydrogen cleaning water (pH 7, ORP: -415 mV) obtained by dissolving hydrogen gas in pure water was used as the cleaning liquid. The cleaning liquid preparation conditions and the experiment and evaluation methods other than these parameters were the same as in Comparative Example 1.
[0062]
[Comparative Example 5]
In this comparative example, hydrogen-dissolved water (pH 10, ORP: -415 mV) in which hydrogen gas was dissolved in pure water was used as a cleaning liquid. The cleaning liquid preparation conditions and the experiment and evaluation methods other than these parameters were the same as in Comparative Example 1. The results of Examples 1 to 4 and Comparative Examples 1 to 4 are also shown in Table 3.
[0063]
In the cleaning liquids of Examples 1 to 4, excellent PSL removal properties were obtained. Good characteristics were also obtained in terms of aluminum corrosion prevention and foam prevention. On the other hand, in Comparative Example 1 in which a nonionic surfactant having a small HLB value was used alone, no PSL removability was obtained, and in contrast, Comparative Example 2 in which a nonionic surfactant having a large HLB value was used alone was used. In Comparative Example 2, in which the anionic surfactant was used alone, there was a problem that a large amount of foaming occurred. In Comparative Example 4 using neutral hydrogen-dissolved water, sufficient PSL removability was not obtained, and in Comparative Example 5 using basic hydrogen-dissolved water, aluminum corrosion occurred.
[0064]
[Table 3]

[0065]
From the above results, by combining at least two types of nonionic surfactants including a nonionic surfactant having a small HLB value and a nonionic surfactant having a large HLB value, it is possible to complement the disadvantages of both. It was confirmed that the overall cleaning performance was improved as compared with the case where one kind of nonionic surfactant, anionic surfactant and functional water was used.
[0066]
In Examples 5 to 8 below, cleaning was performed using a substance other than hydrogen as the redox potential regulator. In Examples 5 to 8, the conditions for the preparation of the cleaning solution, the experiment and the evaluation method were the same as those in Example 1 except that the oxidation-reduction potential regulator was adjusted to the ORP described in each example except for using hydrogen other than the hydrogen described in each example. I did the same.
[0067]
[Example 5]
Hydroxylamine was used as a redox potential regulator. ORP was -288 mV.
[0068]
[Example 6]
Ascorbic acid was used as a redox potential regulator. ORP was -100 mV.
[0069]
[Example 7]
Oxygen was used as a redox potential regulator. ORP was 427 mV.
[0070]
Example 8
Hypochlorous acid was used as a redox potential regulator. ORP was 612 mV.
[0071]
The results of Examples 5 to 8 are also shown in Table 4. In each of the cleaning liquids of Examples 5 to 8, the same PSL removal property as that obtained when hydrogen was used as the redox regulator of Example 1 was obtained, and the oxidation-reduction potential based on the hydrogen electrode (25 ° C.) was approximately −1200. It was confirmed that good cleaning performance could be obtained in the range of about 100 mV to about 400-1200 mV.
[0072]
[Table 4]

[0073]
In the following Examples 9 to 10 and Comparative Example 6, in place of the aluminum wiring materials evaluated in Examples 1 to 8 and Comparative Examples 1 to 5, the corrosiveness to the copper wiring material which is being studied as a low-resistance wiring material was evaluated. Examined.
[0074]
[Example 9]
In order to examine the corrosiveness of the copper wiring in the cleaning solution, a 5 cm square silicon substrate on which a copper plating thin film was formed was immersed in a cleaning solution under the preparation conditions shown in Table 1, and the degree of corrosion was evaluated. The temperature of the cleaning solution was set to room temperature (22 to 24 ° C.), the substrate was immersed for 1 hour, and the concentration of the copper component dissolved in the cleaning solution was analyzed by using a graphite furnace atomic absorption spectrometer.
[0075]
The copper component elutes from the copper plating film even if it is simply immersed in pure water. Therefore, the amount dissolved in each cleaning solution was evaluated by the ratio to the amount dissolved in pure water. This makes it possible to make a strict evaluation on the corrosiveness of copper.
5 Copper dissolution ratio is less than 20%
4 ... 20% or more and less than 50%
3 ... 50% or more and less than 70%
2 ... 70% or more and less than 90%
1 ···· 〃 90% or more
[0076]
[Example 10]
In this example, the cleaning solution (nonionic surfactant having a small HLB (sorbitan monourarate)) and the nonionic surfactant having a large HLB (decaglyceryl monouranate) used in Example 3 were added to the anionic surfactant (polyoxyethylene). A washing solution to which alkyl ether triethanolamine) was added was used. The evaluation was performed in the same manner as in Example 9.
[0077]
[Comparative Example 6]
In this comparative example, hydrogen dissolved water (pH 10, ORP: -620 mV) adjusted to pH 10 after dissolving hydrogen gas in pure water was used as the cleaning liquid. The evaluation was performed in the same manner as in Example 9.
[0078]
Table 5 shows the results of Examples 9 to 10 and Comparative Example 6. In Examples 9 and 10, the amount of copper dissolved was suppressed to less than 20% in pure water ratio, and almost corrosion was prevented. On the other hand, in Comparative Example 6 using the conventional hydrogen-dissolved water, a remarkable amount of copper was eluted at a pure water ratio, and corrosion occurred.
[0079]
[Table 5]

[0080]
In the following Examples 11 to 12, after cleaning using the cleaning composition of the present invention, cleaning was further performed using a nonionic surfactant having an HLB value of 15 to 20 or an anionic surfactant.
[0081]
[Example 11]
After the washing of Example 1, washing was further performed with an aqueous solution (pH 7) containing 0.005% of decaglyceryl monolaurate (nonionic surfactant, HLB value: 15.5). The same evaluation as in Example 1 was performed on the PSL removability of the cleaned silicon substrate.
[0082]
[Example 12]
After the washing in Example 1, washing was performed with an aqueous solution (pH 9) containing 0.001% of polyoxyethylene alkyl ether triethanolamine sulfate (anionic surfactant). The same evaluation as in Example 1 was performed on the PSL removability of the cleaned silicon substrate.
[0083]
Table 6 shows the results of Examples 11 to 12. By performing the two-stage cleaning using the cleaning liquids of Examples 11 to 12, the PSL removability was improved in each case as compared with the cleaning of Example 1 alone.
[0084]
[Table 6]

[0085]
Example 13
In this embodiment, a device is formed using a Cu film as a low resistance metal film and a porous MSQ (methyl silsesquioxane) film as a low dielectric constant film, and particle contamination (ashing residue and etching) generated during the device formation process. (Residue) was washed. Table 7 shows the conditions for preparing the cleaning solution used in this example. The cleaning liquid was evaluated for particle (residue) removability, corrosiveness to the Cu film, and deterioration of the MSQ film by the method described later, and the degree of foaming of the cleaning liquid and the overall cleaning performance evaluation were the same as in Example 1. I went to.
[0086]
[Table 7]

[0087]
(Evaluation of particle (residue) removal properties)
In this embodiment, an element is formed by a general single damascene process, and an ashing residue and an etching residue generated in a via hole after the element is formed are washed by the same method as in the first embodiment. After the cleaning, a cross section of the inside of the via hole of the device was observed using a scanning electron microscope (SEM), and the removability of particles (residues) was evaluated. The evaluation criteria were as follows.
5 ... No residual was observed
4 ... Remaining is slightly observed (less than 10%)
3 ... Remaining about 20 to 50% is observed
2 ... Remaining about 6 to 8 are recognized
1… ..most remain
[0088]
(Evaluation of corrosiveness to Cu film)
After the device was formed, the surface of the Cu film exposed at the via bottom was observed by SEM to evaluate the degree of corrosion. The degree of corrosion was evaluated according to the following criteria.
5: No change is observed
4. Slight corrosion is observed
3 ・ ・ ・ ・ ・ ・ ・ Partial corrosion is observed
2. Corrosion is observed in more than half
1 ···· The whole is corroded or completely dissolved
[0089]
(Evaluation for deterioration of MSQ film)
After the device was formed, the surface of the MSQ film exposed on the side wall of the via hole was observed for its degree of deterioration by using an SEM. Further, the dielectric constant of the MSQ film was measured to evaluate the degree of characteristic deterioration. In the measurement of the dielectric constant, the moisture adsorbed in the pores of the film had a great effect, so the MSQ film was heated at 250 ° C. for 5 minutes, dried, and then measured. The evaluation criteria were as follows.
5: No change is observed
4 ... A slight alteration is observed. Or a slight increase in dielectric constant
3. Partial deterioration is observed. Or some increase in dielectric constant
2. Alteration is observed in more than half. Or an apparent increase in dielectric constant
1 ... The whole is corroded. Or a significant increase in dielectric constant
[0090]
[Table 8]

[0091]
Table 8 shows the results of Example 13. In Example 13, most of the ashing residue and the etching residue were removed. In addition, a sufficient anticorrosion effect was observed for the Cu film and the MSQ film, and foaming was almost suppressed. That is, it was recognized that there was an excellent effect in cleaning the element formation substrate.
[0092]
[Example 14]
In the present example, a cleaning apparatus provided with a concentration control means shown in FIG. 5 was used in order to maintain the concentration of the cleaning composition during cleaning in a constant range. In the present apparatus, the cleaning liquid is stored in the storage tank 15 and circulated in the tank by the circulation pump 16. The storage tank 15 is provided with a thermometer 17, a pH meter 18, a water level meter 19, an electric conductivity meter 20, a specific gravity meter 21, and a heater 22 for monitoring the state of the cleaning liquid. A detergent such as a surfactant, various additives, and a pH adjuster is stored in the chemical tanks 23, 24, and 25, and sent to the storage tank 15 by the liquid sending pumps 26, 27, and 28. In addition, the amount and timing of sending the cleaning agent are controlled by a control unit (not shown) so that the concentration of the cleaning solution is within a certain range according to the state of the cleaning solution monitored in the above 17 to 22. On the other hand, at the time of substrate cleaning, the cleaning liquid is sent from the storage tank 15 to the substrate cleaning section 29 by the liquid feed pump 30 and supplied to the substrate (not shown). Further, if necessary, the cleaning liquid after the cleaning is collected by the pump 31 into the storage tank 15 via drainage or a filter 32.
[0093]
FIG. 6 shows the results of evaluating the concentration fluctuation during the cleaning of the cleaning liquid. In this example, the concentration fluctuation (measured value / set value ratio) of the cleaning solution was within ± 5%, and was kept almost constant.
[0094]
【The invention's effect】
According to the present invention, in cleaning a device substrate, while preventing corrosion and dissolution of a metal film or a metal compound film used for wiring, an insulating film, a capacitance film, and the like, and preventing the generation of a watermark, The contamination such as particles on the substrate can be cleaned very effectively without deteriorating the characteristics.
[0095]
The reason for this is that HLB values differing between a nonionic surfactant having at least one hydroxyl group in one molecule and having an HLB of 3 to less than 12 and a nonionic surfactant having an HLB of 12 to 20 are 2 This is because the combination of two or more nonionic surfactants can compensate for the drawbacks of using one nonionic surfactant alone. In addition, the cleaning performance can be enhanced by adjusting the oxidation-reduction potential to approximately -1200 mV to 100 mV and approximately 400 mV to 1200 mV on the basis of the hydrogen electrode (25 ° C.) using the oxidation-reduction potential adjusting agent.
[0096]
Further, an alcohol, an anionic surfactant, fluoride ion, benzotriazole or a derivative thereof, or a chelating agent may be added to the cleaning composition, or after the cleaning with the cleaning composition, a nonionic having an HLB of 15 to 20 is used. This is because cleaning performance can be further improved by cleaning with an aqueous solution containing a surfactant or an anionic surfactant. By using the above cleaning composition, it is possible to clean even new materials such as low resistance metals, low dielectric constant materials, and ferroelectric materials, which cannot be handled by conventional cleaning liquids, thereby improving device performance and productivity. Can be improved.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the HLB value and the cleaning effect of the cleaning composition of the present invention.
FIG. 2 is a view showing a preferable oxidation-reduction potential of the cleaning composition of the present invention.
FIG. 3 is a graph showing the relationship between the particle removal property of a cleaning composition of the present invention and the degree of corrosion of metal and pH.
FIG. 4 is a view showing one embodiment of the substrate cleaning apparatus of the present invention.
FIG. 5 is a view showing one embodiment of the substrate cleaning apparatus of the present invention.
FIG. 6 is a graph showing the effect of suppressing fluctuations in concentration of a cleaning composition by the substrate cleaning apparatus of the present invention.
[Explanation of symbols]
1 deaerator
2 Gas permeable membrane
3 storage tanks
4 Storage tank
5 Storage tank
6 pump
7 pump
8 pump
9 In-line mixer
10 Bypass
11 nozzles
12 Substrate
13 Arm part
14 Rotation support
15 Storage tank
16 Circulation pump
17 Thermometer
18 pH meter
19 Water level gauge
20 Electric conductivity meter
21 Hydrometer
22 heater
23 Chemical tank
24 Chemical tank
25 Chemical tank
26 Liquid pump
27 Liquid pump
28 Liquid pump
29 Substrate cleaning section
30 Liquid pump
31 pump
32 filters

Claims (22)

Two or more nonionic surfactants having different HLB values including a nonionic surfactant having at least one hydroxyl group in one molecule and having an HLB of 3 or more and less than 12 and a nonionic surfactant having an HLB of 12 or more and 20 or less. A cleaning composition for a device substrate, comprising an ionic surfactant. A non-ionic surfactant having an oxidation-reduction potential based on a hydrogen electrode at 25 ° C. of about −1200 mV or more and 100 mV or less, having at least one hydroxyl group in one molecule, and having an HLB of 3 or more and less than 12; A cleaning composition for a device substrate, wherein the aqueous solution contains a nonionic surfactant having an HLB of 12 or more and 20 or less. An aqueous solution having an oxidation-reduction potential based on a hydrogen electrode at 25 ° C. of about 400 mV to 1200 mV, having at least one hydroxyl group in one molecule and having an HLB of 3 to less than 12; A cleaning composition for a device substrate, wherein the aqueous solution contains 12 to 20 nonionic surfactants, respectively. The cleaning composition for a device substrate according to any one of claims 1 to 3, wherein the cleaning composition has a pH of 5 to 12. The cleaning composition for a device substrate according to any one of claims 1 to 4, wherein the cleaning composition contains an alcohol. The cleaning composition for a device substrate according to any one of claims 1 to 5, wherein the cleaning composition contains an anionic surfactant. The cleaning composition for a device substrate according to any one of claims 1 to 6, wherein the cleaning composition contains a fluoride ion. The device substrate according to any one of claims 1 to 7, further comprising benzotriazole or a derivative thereof in addition to the cleaning composition or in place of the nonionic surfactant having an HLB of 3 or more and less than 12. Cleaning composition. The cleaning composition for a device substrate according to any one of claims 1 to 7, wherein the cleaning composition contains a chelating agent. The cleaning composition contains at least one redox potential regulator selected from the group consisting of hydrogen gas, amine, ammonia, tetramethylammonium hydroxide, carboxylic acid, aldehyde, sugar, and hyposulfite. The cleaning composition for a device substrate according to claim 2, wherein the oxidation-reduction potential of the cleaning composition is adjusted to −1200 mV or more and 100 mV or less by 10. The cleaning composition includes at least one kind of redox selected from oxygen, ozone, carbon dioxide, perchloric acid or a salt thereof, hypochlorous acid or a salt thereof, peroxide, peroxoacid or a salt thereof, nitric acid, and sulfuric acid. The device for a device substrate according to any one of claims 3 to 9, further comprising a potential adjuster, wherein the oxidation-reduction potential adjuster adjusts the oxidation-reduction potential of the cleaning composition to approximately 400 mV or more and 1200 mV or less. Cleaning composition. The nonionic surfactant includes any of polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyethylene glycol fatty acid esters, polyglycerin fatty acid esters, pentaerythritol fatty acid esters, sorbitan fatty acid esters, and sorbite fatty acid esters. The device substrate according to any one of claims 1 to 11, wherein the device substrate is at least one selected from the group consisting of polyhydric alcohol fatty acid esters, their ethylene oxide adducts, and fluorine-based surfactants. Cleaning composition. The nonionic surfactant is a compound represented by any one of the following general formulas [1], [2], [3], and [4], or a compound in which ethylene oxide is added to the molecular structure. The cleaning composition for a device substrate according to claim 1, wherein the cleaning composition is at least one selected from the group consisting of:

At least one of X1 to X4 is an OH group, and the rest show OCOR. R represents a hydrocarbon group having 5 to 17 carbon atoms.

At least one of X1 to X5 is an OH group, and the rest show OCOR. R represents a hydrocarbon group having 5 to 17 carbon atoms.

At least one of X1 to X5 is an OH group, and the rest show OCOR. R represents a hydrocarbon group having 5 to 17 carbon atoms. N represents a number of 2 to 10.

At least one of X1 to X4 is an OH group, and the rest show OCOR. R represents a hydrocarbon group having 5 to 17 carbon atoms. 14. The cleaning composition for a device substrate according to claim 1, wherein the concentration of the nonionic surfactant is about 0.0005 to 0.05% by mass. The cleaning composition for a device substrate according to any one of claims 1 to 14, wherein the cleaning composition is used for cleaning a substrate surface on which a metal or a metal compound is exposed. The metal or metal compound contains one or more materials selected from the group consisting of Ba, Sr, Hf, Zr, Ta, Al, Ti, W, Pb, Mo, Si, Co, Bi, Cu, and Ag. The cleaning composition for a device substrate according to claim 15, wherein: 17. A method for cleaning a device substrate, wherein the cleaning composition according to claim 1 is used as a cleaning liquid. Using the cleaning composition according to any one of claims 1 to 16, a physical force using at least one method selected from an ultrasonic cleaning method, a brush cleaning method, a spray method, a shower cleaning method, and a jet injection method. A method for cleaning a device substrate, comprising applying and cleaning. 19. The method for cleaning a device substrate according to claim 17, wherein the cleaning is performed by dissolving a gas in the cleaning composition. 20. The method according to claim 17, wherein after the cleaning using the cleaning composition, the cleaning is further performed using an aqueous solution containing a nonionic surfactant having an HLB of 15 to 20 or an anionic surfactant. The method for cleaning a device substrate according to any one of the above. 21. The device substrate cleaning method according to claim 20, wherein the concentration of the nonionic surfactant or the anionic surfactant is approximately 0.0001 to 0.005% by mass. A cleaning apparatus for performing cleaning using the cleaning composition according to any one of claims 1 to 16, or the cleaning method according to any one of claims 17 to 21.
An apparatus for cleaning a device substrate, comprising a concentration control means for maintaining the concentration of the cleaning composition within a certain range.

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