JP2004331852A

JP2004331852A - Abrasive slurry excellent in dispersion stability, and manufacturing method for substrate

Info

Publication number: JP2004331852A
Application number: JP2003131025A
Authority: JP
Inventors: Shiyunren Chiyou; 俊連長; Akira Iwaki; 彰岩城; Toshiaki Aso; 敏明麻生
Original assignee: Tama Kagaku Kogyo Co Ltd
Current assignee: Tama Kagaku Kogyo Co Ltd
Priority date: 2003-05-09
Filing date: 2003-05-09
Publication date: 2004-11-25
Also published as: TWI298666B; KR100808758B1; CN1330733C; US20070094936A1; KR20040095615A; US20040221516A1; TW200424036A; CN1550537A

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abrasive slurry which is excellent in the dispersion stability over a long period and is so good in the redispersibility as to solve as much as possible the problems of sedimentation and flocculation and which is available with no dispersant and no use at all of an organic dispersant, and to provide a manufacturing method, by using this abrasive slurry for CMP and with an industrial profit, for a substrate such as a silicon substrate used in a semiconductor manufacturing process and an aluminum substrate used in an electrostatic-chuck manufacturing process. <P>SOLUTION: The abrasive slurry contains the abrasive fine particle selected from one or more kinds of oxides, the colloidal fine particle of colloidal oxide having an average particle diameter smaller than that of the above abrasive fine particle, and a dispersing medium for dispersing these abrasive fine particle and colloidal fine particle, the slurry being excellent in the dispersion stability. The manufacturing method for a substrate comprises an abrasion process of abrading an inorganic substrate by using this abrasive slurry. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
この発明は、分散安定性に優れた研磨剤スラリーに係り、特に限定するものではないが、半導体製造工程や静電チャック製造工程で行われる基板表面の平坦化のための表面研磨を始めとして、フォトマスクブランクス、ガラスディスク、光学レンズ等の被研磨面の研磨に幅広く採用されている化学的機械研磨（ＣｈｅｍｉｃａｌＭｅｃｈａｎｉｃａｌＰｏｌｉｓｈｉｎｇ；以下「ＣＭＰ」という）の用途に用いるのに好適な研磨剤スラリーに関する。
【０００２】
【従来の技術】
例えば、半導体製造工程で用いられるシリコン基板や静電チャック製造工程で用いられるアルミニウム基板等の基板については、極めて高い精度の平坦性が要求されており、その被研磨面である基板表面を平坦化する技術として、研磨微粒子による機械的研磨とエッチング液による化学的研磨とを組み合わせたＣＭＰにより、基板表面に損傷を与えることなく基板表面を高度に平坦化する平坦化技術が採用されている。
【０００３】
そして、このような平坦化技術で用いる研磨剤としては、一般に、研磨対象となる基板の種類や平坦化技術で要求される加工速度等に応じて、種々の大きさ（平均粒径）を有する酸化セリウム（ＣｅＯ_２）、二酸化マンガン（ＭｎＯ_２）等の金属酸化物や、沈降シリカ、ヒュームドシリカ、コロイダルシリカ等の珪素酸化物（ＳｉＯ_２）や、ヒュームドアルミナ、コロイダルアルミナ等のアルミニウム酸化物（Ａｌ_２Ｏ_３）等の種々の種類の研磨微粒子を水等の分散媒中に分散させて得られたスラリーが用いられている。
【０００４】
しかるに、これらの研磨微粒子は、その種類や大きさによっては分散媒中での分散安定性が悪く、例えば、酸化セリウム粒子の場合には、比較的大きな比重を有するために、酸化セリウム粒子を分散媒中に分散させて研磨剤スラリーを調製すると、調製後しばらくは均一に分散してはいるものの、その後比較的短時間で酸化セリウム粒子が分離し始め、沈降し、やがては粒子の凝集を起こしてその粒径が大きくなり、粒度分布が広くなるという沈降・凝集の問題を引き起こし、加工速度が経時的に変化し、また、基板表面が損傷する等の問題が生じる。
【０００５】
このため、従来においては、このような研磨剤スラリーにおける沈降・凝集の問題を解消するため、例えば、研磨剤スラリーの使用直前に攪拌して研磨微粒子を再び分散させる再分散処理や、凝集して所定の粒径より大きくなった異常凝集粒子を濾過して分離除去する分離除去処理等が行われており、基板等の平坦化工程での大きな負担になっている。
【０００６】
そこで、従来においても、この研磨剤スラリーの沈降・凝集の問題を解決するための幾つかの提案がされている。
すなわち、酸化セリウム粒子、アクリル酸アンモニウム塩とアクリル酸メチルとの共重合体、及び水を含み、沈降し難く、ＳｉＯ_２絶縁膜等の被研磨面を損傷することなく高速で研磨可能な酸化セリウム研磨剤が提案されている（特許文献１参照）。
【０００７】
また、分散剤として水溶性有機高分子、水溶性陰イオン性界面活性剤、水溶性非イオン性界面活性剤及び水溶性アミンから選ばれた少なくとも１種の化合物を含み、最大沈降速度が１μｍ／ｓ以下であり、沈降が少なく、攪拌による均一化が容易であり、ＳｉＯ_２絶縁膜等の被研磨面を損傷することなく高速で研磨可能な酸化セリウム研磨剤が提案されている（特許文献２参照）。
【０００８】
更に、酸化セリウム粒子と、ポリアクリル酸の全カルボキシル基の９０％超をアンモニアで中和させた第１のポリアクリル酸塩と、ポリアクリル酸の全カルボキシル基の１５〜５０％をアンモニアで中和させた第２のポリアクリル酸塩と、水とを含み、第１のポリアクリル酸塩と第２のポリアクリル酸塩の合計含有量が０．１５〜１重量％であり、安定性が良く、二層分離や凝集沈降固結、粘度変化を起こさない酸化セリウム研磨剤が提案されている（特許文献３参照）。
【０００９】
しかしながら、これら分散剤を含む酸化セリウム研磨剤についても、１ヶ月あるいはそれ以上の長期に亘って沈降・凝集の問題を解消し、再分散性のよい状態に維持することは困難であり、また、製造工程においては、凝集した研磨剤による装置配管内の詰り等の発生事例も認められ、これらの諸問題を必ずしも完全には解決できないという問題がある。
【００１０】
また、これらいずれの酸化セリウム研磨剤も、分散剤として水溶性有機高分子、水溶性陰イオン性界面活性剤、水溶性非イオン性界面活性剤、水溶性アミン等の有機化合物を比較的多量（０．１〜５重量％）に含むものであり、研磨処理後の廃液中には酸化セリウム粒子の無機物質と分散剤等の有機物質とが混在し、この廃液処理に多大な手間とコストとを要するという問題もある。
【００１１】
加えて、このような研磨剤スラリーについては、その製造コストや輸送コストを可及的に低減するという観点から、製造時にはできるだけ高濃度のものを製造し、使用時に所定の濃度まで希釈して使用するのが望ましいが、沈降・凝集の問題は高濃度であればあるほど発生し易く、より一層の分散安定性に優れた研磨剤スラリーの開発が望まれている。
【００１２】
【特許文献１】特開２０００−１７１９５号公報
【特許文献２】特開２００１−１３８２１４号公報
【特許文献３】特開２００２−３５３１７５号公報
【００１３】
【発明が解決しようとする課題】
そこで、本発明者らは、長期に亘って分散安定性に優れており、また、再分散性が良好で、沈降・凝集の問題を可及的に解消することができるほか、有機系分散剤を全く使用しない分散剤フリーでの使用が可能な研磨剤スラリーについて鋭意検討した結果、コロイド状酸化物であって研磨微粒子より小さい平均粒径を有するコロイダル微粒子を添加することにより、研磨微粒子の沈降・凝集を可及的に抑制できることを見出し、本発明を完成した。
【００１４】
従って、本発明の目的は、長期に亘って分散安定性に優れており、また、再分散性が良好で、沈降・凝集の問題を可及的に解消することができるほか、有機系分散剤を全く使用しない分散剤フリーでの使用が可能な研磨剤スラリーを提供することにある。
【００１５】
また、本発明の他の目的は、このような研磨剤スラリーを用いて、ＣＭＰにより半導体製造工程で用いられるシリコン基板や静電チャック製造工程で用いられるアルミニウム基板等の基板を工業的に有利に製造するための基板の製造方法を提供することにある。
【００１６】
【課題を解決するための手段】
すなわち、本発明は、１種又は２種以上の酸化物からなる研磨微粒子と、コロイド状酸化物であって上記研磨微粒子より小さい平均粒径を有するコロイダル微粒子と、これら研磨微粒子及びとコロイダル微粒子とを分散させる分散媒とを含む、分散安定性に優れた研磨剤スラリーである。
また、本発明は、無機質の基板を製造する方法であって、上記の研磨剤スラリーを用いて基板を研磨する研磨工程を含む、基板の製造方法である。
【００１７】
本発明において、研磨微粒子として用いられる酸化物としては、従来この種の研磨微粒子として用いられているものをそのまま使用することができ、具体的には、酸化セリウム（ＣｅＯ_２）、二酸化マンガン（ＭｎＯ_２）等の金属酸化物や、沈降シリカ、ヒュームドシリカ、コロイダルシリカ等の珪素酸化物（ＳｉＯ_２）や、ヒュームドアルミナ、コロイダルアルミナ等のアルミニウム酸化物（Ａｌ_２Ｏ_３）等を挙げることができる。これらはその１種のみを単独で用いることができるほか、２種以上を混合して用いることもできる。
【００１８】
これらの酸化物のうち、本発明で研磨微粒子として用いる上で好ましいのは、例えば酸化セリウム粒子、酸化アルミニウム粒子等のように、比較的比重が高く、あるいは、比較的平均粒径が大きく、それ自体では沈降・凝集を起こし易いものであるのがよく、このような研磨微粒子に対して特に有効である。
【００１９】
本発明で用いる研磨微粒子の平均粒径（Ｄｐ）については、特に制限はなく、また、種類によっても異なるが、酸化セリウム粒子の場合には、通常１００〜５，０００ｎｍ、好ましくは５００〜２，０００ｎｍであるのがよく、研磨微粒子の種類によっては、平均粒径（Ｄｐ）が１００ｎｍより小さいと研磨能力が十分に発揮されない場合があり、反対に、５，０００ｎｍより大きくなると研磨面に傷が生じ易いという問題がある。
【００２０】
また、この研磨微粒子と共に用いられるコロイダル微粒子については、例えば、コロイダルシリカ、コロイダルアルミナ等のコロイド状酸化物を挙げることができ、これらはその１種のみを単独で用いることができるほか、２種以上を混合して用いることもできる。
【００２１】
そして、このコロイダル微粒子の平均粒径（Ｄｃ）については、少なくとも上記研磨微粒子より小さいことが必要であり、種類によっても異なるが、コロイダルシリカの場合を含めて多くの場合、通常１０〜３００ｎｍ、好ましくは２０〜２００ｎｍであって、上記研磨微粒子の平均粒径（Ｄｐ）とこのコロイダル微粒子の平均粒径（Ｄｃ）との粒径比（Ｄｃ／Ｄｐ）が１０以下、好ましくは０．０１〜３程度であるのがよい。このコロイダル微粒子の平均粒径（Ｄｃ）が１０ｎｍより小さいと製造時に不安定でゲル化し易く、反対に、３００ｎｍより大きくなると粒径にバラツキが生じ易く、また、粒径比（Ｄｃ／Ｄｐ）が１０を超えると結果として研磨微粒子が小さくなりすぎて研磨能力が十分に発揮されない。
【００２２】
更に、研磨剤スラリーを構成する分散媒については、従来この種の研磨剤スラリーにおいて用いられている分散媒をそのまま用いることができ、特に制限されるものではなく、この研磨剤スラリーの用途、例えば半導体製造工程で用いるシリコン基板や静電チャック製造工程で用いるアルミニウム基板等の基板の平坦化に用いられるＣＭＰ用の研磨剤スラリーであるか、フォトマスクブランクス、ガラスディスク、光学レンズ等の被研磨面の研磨に用いられるＣＭＰ用の研磨剤スラリーであるか、更にはその他の被研磨面の研磨に用いられる通常の研磨剤スラリーであるか等によって適宜選択できるが、好ましくは水、又は、水を主成分としてメタノール、エタノール、ｎ−プロパノール、ｉｓｏ−プロパノール、ｎ−ブタノール、ｔｅｒｔ−ブタノール等のアルコール類や、ケトン類、エステル類、エーテル類等の水溶性溶剤を含む水性分散媒が好適に用いられる。また、この分散媒中には、従来の場合と同様に、必要に応じてＣＭＰの際に化学的研磨を行うためのエッチング液も添加される。
【００２３】
そして、本発明の研磨剤スラリーを構成する上記研磨微粒子の粒子濃度（Ｃｐ）については、研磨微粒子の種類によって異なるが、酸化セリウム粒子の場合には、通常５〜４０重量％、好ましくは５〜３０重量％、より好ましくは５〜１０重量％であって、また、コロイダル微粒子の粒子濃度（Ｃｃ）については、コロイダルシリカの場合を含めて多くの場合、通常０．１〜５重量％、好ましくは０．５〜２重量％であるのがよく、更に、上記研磨微粒子とコロイダル微粒子との重量配合比（Ｃｃ／Ｃｐ）が１以下、好ましくは０．５以下であるのがよい。このような粒子濃度（Ｃｐ）及び（Ｃｃ）で調製された研磨剤スラリーは、そのままの粒子濃度（Ｃｐ）及び（Ｃｃ）で、あるいは、必要に応じて分散媒により所定の粒子濃度（Ｃｐ）及び（Ｃｃ）まで希釈してＣＭＰ等の研磨に用いられる。研磨微粒子の粒子濃度（Ｃｐ）が５重量％より低いと研磨能力が不足し、反対に、４０重量％より高くなると溶解性に問題が生じる。また、コロイダル微粒子の粒子濃度（Ｃｃ）が０．１重量％より低いと沈降・凝集の抑制効果が低下し、反対に、５重量％より高くなると逆に凝集現象が生じ易くなる。更に、研磨微粒子とコロイダル微粒子との重量配合比（Ｃｃ／Ｃｐ）が１を超えると、凝集現象が生じ易くなる。
【００２４】
本発明の研磨剤スラリーは、特に水溶性有機高分子、水溶性陰イオン性界面活性剤、水溶性非イオン性界面活性剤及び水溶性アミン等の有機系分散剤を添加しなくても長期に亘る分散安定性に優れており、また、再分散性が良好で、沈降・凝集の問題を可及的に解消することができる。
【００２５】
また、本発明において、研磨剤スラリーを調製する方法についても、その構成成分である研磨微粒子、コロイダル微粒子及び分散媒が均一に混合され、分散媒中に研磨微粒子及びコロイダル微粒子が均一に分散したスラリーとなればよく、特に制限はなく、通常の攪拌機を用いて調製できるほか、必要により超音波分散機、ホモジナイザー、ボールミル、振動ボールミル、遊星ボールミル、媒体攪拌式ミル等の湿式分散機を用いることができる。
【００２６】
本発明の研磨剤スラリーは、半導体製造工程で用いるシリコン基板や静電チャック製造工程で用いるアルミニウム基板等の基板の平坦化だけでなく、所定の配線を有する配線板に形成された酸化珪素絶縁膜等の酸化膜、ガラス、窒化ケイ素等の無機絶縁膜、フォトマスク・レンズ・プリズム等の光学ガラス、ＩＴＯ等の無機導電膜、ガラス及び結晶質材料で構成される光集積回路・光スイッチング素子・光導波路、光ファイバ−の端面、シンチレ−タ等の光学用単結晶、固体レ−ザ単結晶、青色レ−ザ用ＬＥＤサファイア基板、ＳｉＣ、ＧａＰ、ＧａＡＳ等の半導体単結晶、磁気ディスク用ガラス基板、磁気ヘッド等を研磨するために使用される。
【００２７】
例えば、回路素子とアルミニウム配線が形成された段階の半導体基板や、回路素子が形成された段階の半導体基板等の基板上に酸化珪素絶縁膜等の酸化膜が形成された基板について、その酸化膜表面の凹凸を解消するための平坦化を目的にＣＭＰを行う場合、基板を保持するホルダーと研磨布（パッド）が貼り付けられた回転盤とを備えた一般的な研磨装置を用い、研磨布には本発明の研磨剤スラリーをポンプ等で連続的に一定量ずつ供給し、所定の回転数及び加圧下の下に研磨することができる。
【００２８】
そして、研磨終了後の基板については、通常の後処理の場合と同様に、流水中で良く洗浄後、スピンドライヤ等を用いて基板上に付着した水滴を払い落としてから乾燥させる。
この基板の研磨の際に排出される廃液については、有機系分散剤を全く使用しない分散剤フリーであるため、従来に比べてその廃液処理を極めて経済的に行うことができる。
【００２９】
【発明の実施の形態】
以下、実施例及び比較例に基づいて、本発明の好適な実施の形態を具体的に説明する。
【００３０】
実施例１〜２７
〔コロイダルシリカ（２０ｎｍ）の調製〕
液留出口、液面制御装置及び攪拌機を備えたジャケット付き１ｍ^３−タンクに、メチルシリケート３２ｋｇ、メタノール１００ｋｇ及び純水７６８ｋｇを仕込み、混合してＡ液とした。
また、攪拌機を備えた３ｍ^３−タンクに、メチルシリケート３６８ｋｇ、メタノール１００ｋｇ、純水１８４０ｇ及び２８ｗｔ％−アンモニア水１２ｋｇを仕込み、混合してＢ液とした。
【００３１】
次に、Ａ液が入ったタンクをスチーム加熱し、メタノールと水の混合液を留出させ、Ａ液から液が留出し始めたところでＡ液の液面が一定になるようにＢ液を添加し、Ｂ液の全てを添加し終えたところで、更にＡ液の液面が一定になるように純水２４０ｋｇを添加し、反応させた。
反応終了後、Ａ液が入っていたタンク内から反応生成物を取り出して分析した結果、シリカ濃度が２０重量％であって平均粒径が２０ｎｍであるコロイド状シリカ生成物（コロイダルシリカ（２０ｎｍ））であった。
【００３２】
〔コロイダルシリカ（７０ｎｍ）の調製〕
攪拌機を備えたジャケット付き３ｍ^３−タンクに、メタノール１７２１．７ｋｇ、純水３０６．３ｋｇ及び２８ｗｔ％−アンモニア水８８．４ｋｇを仕込み、混合した後、液温を２３±１℃に調整し、次いで液温を２３±１℃に維持しながら２〜２．５時間かけて攪拌下に４０４．４ｋｇのメチルシリケートを投入し、反応させた。
【００３３】
反応終了後、得られた反応混合物の粗製品を液留出口、液面制御装置及び攪拌機を備えたジャケット付き１ｍ^３−タンクに移し、タンクをスチーム加熱してメタノール、水及びアンモニアの混合液を留出させ、タンクから液が留出し始めたところで液面が一定になるように残りの反応混合物を添加し、反応混合物の全てを添加し終えたところで、更に液面が一定になるように純水を添加し、タンク内の液温が１００℃に到達するまで純水の添加を行った。
【００３４】
液温が１００℃に到達したところで加熱を終了し、中間製品にして冷却し、液温が７０℃になったところで適量の２８ｗｔ％−アンモニア水を添加し、更に攪拌して混合した後、タンクから反応生成物を取り出した。
得られた反応生成物は、シリカ濃度が３０重量％であって平均粒径が７０ｎｍであるコロイド状シリカ生成物（コロイダルシリカ（７０ｎｍ））であった。
【００３５】
〔コロイダルシリカ（１７０ｎｍ）の調製〕
攪拌機を備えたジャケット付き１．８ｍ^３−タンクに、メタノール８８５．１ｋｇ、純水６３．１ｋｇ及び２８ｗｔ％−アンモニア水１１３．２５ｋｇを仕込み、混合した後、温度を２３±１℃に調整し、次いで液温を２３±１℃に維持しながら３時間かけて攪拌下に１７１．１ｋｇのメチルシリケートを投入し、反応させた。
【００３６】
反応終了後、得られた反応混合物の粗製品を液留出口、液面制御装置及び攪拌機を備えたジャケット付き１ｍ^３−タンクに移し、タンクをスチーム加熱してメタノール、水及びアンモニアの混合液を留出させ、タンクから液が留出し始めたところで液面が一定になるように残りの反応混合物を添加し、反応混合物の全てを添加し終えたところで、更に液面が一定になるように純水を添加し、タンク内の液温が１００℃に到達するまで純水の添加を行った。
【００３７】
液温が１００℃に到達したところで加熱を終了し、中間製品にして冷却し、液温が７０℃になったところで適量の２８ｗｔ％−アンモニア水を添加し、更に攪拌して混合した後、タンクから反応生成物を取り出した。
得られた反応生成物は、シリカ濃度が２２重量％であって平均粒径が１７０ｎｍであるコロイド状シリカ生成物（コロイダルシリカ（１７０ｎｍ））であった。
【００３８】
〔研磨剤スラリーの調製〕
研磨微粒子として平均粒径１．１μｍ及び最大粒径８μｍの酸化セリウム粒子（セイミケミカル社製商品名：ＴＥ−５０８）を用い、コロイダル微粒子として上で得られた３種類のコロイダルシリカを用い、分散媒として純水を用い、表１に示す割合で配合し、攪拌機にて均一に混合し、各実施例１〜２７の研磨剤スラリーを調製した。
【００３９】
〔沈殿・凝集状態及び再分散性の評価〕
得られた各実施例１〜２７の研磨剤スラリーについて、その５０ｍｌを１００ｍｌ−試験管内に入れ、１ヶ月間静止放置の後、沈殿・凝集の状態を目視で観察した。
また、５０ｍｌの研磨剤スラリーを１００ｍｌ−ポリエチレン製容器内に入れ、１ヶ月間静止放置した。その後、手振りによる再分散性を目視で観察すると共に、卓上型ボールミル攪拌機（入江商会社製：型式Ｖ−１Ｍ）の上に横に寝かせて載置し、攪拌回転数１００ｒｐｍ及び攪拌時間１０分の条件で攪拌し、攪拌機による再分散性を目視で観察した。
【００４０】
上記の沈殿・凝集状態と再分散性との結果を、
◎：沈殿部全体がソフトであって、手振りにより数秒で再分散が可能であり、また、攪拌機により５分以内に再分散が可能である、
○：沈殿部に固い部分があるが、手振りによる再分散に３０秒程を要し、また、攪拌機による再分散に１０分程を要す、
△：沈殿部に固い部分があるが、手振りによる再分散に２分以上を要し、また、攪拌機による再分散に１０分程を要す、
×：沈殿部全体が完全に固化し、１０分間の手振りでも再分散せず、また、攪拌機による再分散に１０分間以上を要する、
の４段階で評価した。
結果を表１に示す。
【００４１】
〔石英基板研磨速度〕
また、研磨剤スラリーを超純水で３倍に希釈し、研磨布を備えたＣＭＰ用研磨機（ナノファクター社製：ＦＡＣＴ−２００）を用い、回転数２００ｒｐｍ、加工圧力５００ｇ／ｃｍ^２、及び研磨剤スラリーの供給速度１０ｍｌ／ｍｉｎの条件下で、試料（幅３．３ｃｍ×２．６ｃｍ、厚さ１．１５ｍｍの石英基板）を１０分間研磨し、研磨前後の試料の厚さをマイクロメーターで測定し、研磨前後の試料の厚さから石英基板（ＳｉＯ_２）に対する研磨速度（μｍ／１０ｍｉｎ）を求めた。
結果を表１に示す。
【００４２】
比較例１〜１５
有機系分散剤としてポリビニルピロリドン（ＰＶＰ）を用い、上記実施例１〜２７の場合と同様にして比較例１〜１５の研磨剤スラリーを調製し、得られた各比較例１〜１５の研磨剤について、各実施例１〜２７の場合と同様にして、沈殿・凝集状態及び再分散性を評価し、また、石英基板（ＳｉＯ_２）に対する研磨速度（μｍ／１０ｍｉｎ）を求めた。
結果を上記各実施例１〜２７と共に表１に示す。
【００４３】
【表１】

【００４４】
表１に示す結果から明らかなように、本発明の各実施例１〜２７の研磨剤スラリーはいずれも沈降・凝集状態及び再分散性の評価、及び、石英基板研磨速度において優れた性能を発揮するのに対し、コロイダル微粒子及び分散剤のいずれも添加しない比較例１〜３の研磨剤スラリーは再分散が不可能で研磨速度が測定されず、また、１重量％又は３重量％の分散剤のみを添加した比較例４〜１５の研磨剤スラリーは再分散に長時間を要しており、本発明の研磨剤スラリーが特に沈降・凝集状態及び再分散性において優れた性能を有することが判明した。
【００４５】
【発明の効果】
本発明によれば、長期に亘って分散安定性に優れており、また、再分散性が良好で、沈降・凝集の問題を可及的に解消することができ、また、有機系分散剤を全く使用しない分散剤フリーでの使用が可能な研磨剤スラリーを提供することができる。
また、本発明の研磨剤スラリーを用いることにより、ＣＭＰにより半導体製造工程で用いられるシリコン基板や静電チャック製造工程で用いられるアルミニウム基板等の基板を工業的に有利に製造することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an abrasive slurry having excellent dispersion stability, including, but not limited to, surface polishing for flattening a substrate surface performed in a semiconductor manufacturing process or an electrostatic chuck manufacturing process, The present invention relates to an abrasive slurry suitable for use in chemical mechanical polishing (hereinafter, referred to as “CMP”) widely used for polishing a surface to be polished such as a photomask blank, a glass disk, and an optical lens.
[0002]
[Prior art]
For example, substrates such as a silicon substrate used in a semiconductor manufacturing process and an aluminum substrate used in an electrostatic chuck manufacturing process are required to have extremely high flatness, and the surface to be polished is flattened. As a technique for performing the polishing, a flattening technique for highly flattening the substrate surface without damaging the substrate surface by CMP that combines mechanical polishing with abrasive fine particles and chemical polishing with an etchant has been adopted.
[0003]
The polishing agent used in such a planarization technique generally has various sizes (average particle diameters) according to the type of a substrate to be polished, the processing speed required by the planarization technique, and the like. Metal oxides such as cerium oxide (CeO ₂ ) and manganese dioxide (MnO ₂ ), silicon oxides (SiO ₂ ) such as precipitated silica, fumed silica and colloidal silica, and aluminum oxides such as fumed alumina and colloidal alumina A slurry obtained by dispersing various kinds of abrasive fine particles such as a substance (Al ₂ O ₃ ) in a dispersion medium such as water is used.
[0004]
However, these abrasive fine particles have poor dispersion stability in a dispersion medium depending on their type and size.For example, in the case of cerium oxide particles, since they have a relatively large specific gravity, cerium oxide particles are dispersed. When the abrasive slurry is prepared by dispersing it in a medium, the cerium oxide particles begin to separate and settle down in a relatively short period of time after the preparation, but then sediment and eventually agglomerate. This causes problems such as sedimentation and agglomeration that the particle size becomes large and the particle size distribution becomes wide, the processing speed changes with time, and the substrate surface is damaged.
[0005]
For this reason, conventionally, in order to solve the problem of sedimentation / agglomeration in such an abrasive slurry, for example, a re-dispersion process in which the abrasive fine particles are again dispersed by stirring just before use of the abrasive slurry, Separation and removal processing of filtering and separating and removing abnormal agglomerated particles having a particle size larger than a predetermined particle size is performed, which imposes a heavy burden on a step of flattening a substrate or the like.
[0006]
Therefore, some proposals have conventionally been made to solve the problem of sedimentation / aggregation of the abrasive slurry.
That is, cerium oxide containing cerium oxide particles, a copolymer of ammonium acrylate and methyl acrylate, and water, hardly sediments, and can be polished at high speed without damaging the surface to be polished such as a SiO ₂ insulating film. An abrasive has been proposed (see Patent Document 1).
[0007]
Further, it contains at least one compound selected from a water-soluble organic polymer, a water-soluble anionic surfactant, a water-soluble nonionic surfactant and a water-soluble amine as a dispersant, and has a maximum sedimentation velocity of 1 μm / The cerium oxide abrasive has been proposed, which is less than or equal to s, has low sedimentation, can be easily uniformized by stirring, and can be polished at high speed without damaging the surface to be polished such as an SiO ₂ insulating film (Patent Document 2) reference).
[0008]
Further, cerium oxide particles, a first polyacrylate salt in which more than 90% of all carboxyl groups of polyacrylic acid are neutralized with ammonia, and 15 to 50% of all carboxyl groups of polyacrylic acid with ammonia The first polyacrylate and the second polyacrylate have a total content of 0.15 to 1% by weight, and have stability. A cerium oxide abrasive which does not cause two-layer separation, coagulation and sedimentation and viscosity change is proposed (see Patent Document 3).
[0009]
However, even with cerium oxide abrasives containing these dispersants, it is difficult to solve the problem of sedimentation / aggregation over a long period of one month or more, and to maintain good redispersibility, In the manufacturing process, there have been cases where clogging or the like has occurred in the apparatus piping due to the agglomerated abrasive, and there is a problem that these problems cannot always be completely solved.
[0010]
In addition, any of these cerium oxide abrasives contains a relatively large amount of an organic compound such as a water-soluble organic polymer, a water-soluble anionic surfactant, a water-soluble nonionic surfactant, or a water-soluble amine as a dispersant. 0.1 to 5% by weight), and the waste liquid after the polishing process contains an inorganic substance of cerium oxide particles and an organic substance such as a dispersing agent. There is also a problem that requires.
[0011]
In addition, from the viewpoint of minimizing the production cost and transportation cost of such an abrasive slurry, a slurry having a concentration as high as possible is manufactured at the time of manufacture, and the slurry is diluted to a predetermined concentration at the time of use. However, the problem of sedimentation / aggregation is more likely to occur as the concentration is higher, and it is desired to develop an abrasive slurry having more excellent dispersion stability.
[0012]
[Patent Document 1] JP-A-2000-17195 [Patent Document 2] JP-A-2001-138214 [Patent Document 3] JP-A-2002-353175
[Problems to be solved by the invention]
Then, the present inventors have excellent dispersion stability over a long period of time, have good redispersibility, can solve the problem of sedimentation / aggregation as much as possible, and have an organic dispersant. As a result of intensive studies on an abrasive slurry that can be used without a dispersant without using any abrasive, the addition of colloidal fine particles, which are colloidal oxides and have an average particle size smaller than the abrasive fine particles, caused sedimentation of the abrasive fine particles. -It discovered that aggregation could be suppressed as much as possible, and completed this invention.
[0014]
Therefore, an object of the present invention is to provide excellent dispersion stability over a long period of time, good redispersibility, and to solve the problems of sedimentation and aggregation as much as possible. It is an object of the present invention to provide an abrasive slurry that can be used without using a dispersant and that does not use any of them.
[0015]
Further, another object of the present invention is to industrially advantageously use such an abrasive slurry to produce a substrate such as a silicon substrate used in a semiconductor manufacturing process or an aluminum substrate used in an electrostatic chuck manufacturing process by CMP. An object of the present invention is to provide a method of manufacturing a substrate for manufacturing.
[0016]
[Means for Solving the Problems]
That is, the present invention relates to abrasive fine particles comprising one or more oxides, colloidal fine particles which are colloidal oxides and have an average particle diameter smaller than the above-mentioned abrasive fine particles, and these abrasive fine particles and colloidal fine particles. And a dispersion medium for dispersing the same.
Further, the present invention is a method for producing an inorganic substrate, which comprises a polishing step of polishing the substrate using the above-mentioned abrasive slurry.
[0017]
In the present invention, as the oxide used as the polishing fine particles, those conventionally used as this type of polishing fine particles can be used as they are. Specifically, cerium oxide (CeO ₂ ), manganese dioxide (MnO ₂ ) ₂ ) and the like; silicon oxides (SiO ₂ ) such as precipitated silica, fumed silica and colloidal silica; and aluminum oxides (Al ₂ O ₃ ) such as fumed alumina and colloidal alumina. Can be. These can be used alone or in combination of two or more.
[0018]
Among these oxides, those which are preferable for use as the polishing fine particles in the present invention have a relatively high specific gravity or a relatively large average particle diameter, for example, such as cerium oxide particles and aluminum oxide particles. It is preferable that sedimentation and agglomeration easily occur by itself, and it is particularly effective for such abrasive fine particles.
[0019]
The average particle diameter (Dp) of the abrasive fine particles used in the present invention is not particularly limited and varies depending on the type. In the case of cerium oxide particles, the average particle diameter is usually 100 to 5,000 nm, preferably 500 to 2,000. If the average particle size (Dp) is smaller than 100 nm, the polishing ability may not be sufficiently exhibited. Conversely, if the average particle size (Dp) is larger than 5,000 nm, the polished surface may be damaged. There is a problem that it easily occurs.
[0020]
The colloidal fine particles used together with the abrasive fine particles include, for example, colloidal oxides such as colloidal silica and colloidal alumina. These can be used alone or in combination of two or more. May be used in combination.
[0021]
The average particle size (Dc) of the colloidal fine particles needs to be at least smaller than the above-mentioned abrasive fine particles, and varies depending on the type. In many cases, including colloidal silica, the average particle size is usually 10 to 300 nm, preferably. Is 20 to 200 nm, and the particle size ratio (Dc / Dp) between the average particle size (Dp) of the abrasive fine particles and the average particle size (Dc) of the colloidal fine particles is 10 or less, preferably 0.01 to 3 The degree is good. If the average particle diameter (Dc) of the colloidal fine particles is less than 10 nm, the particles are unstable during the production and easily gelled. Conversely, if the average particle diameter (Dc) is more than 300 nm, the particle diameter tends to vary, and the particle diameter ratio (Dc / Dp) is reduced. When it exceeds 10, as a result, the polishing fine particles become too small, and the polishing ability is not sufficiently exhibited.
[0022]
Further, as the dispersion medium constituting the abrasive slurry, the dispersion medium conventionally used in this type of abrasive slurry can be used as it is, and is not particularly limited, and the use of the abrasive slurry, for example, Polishing slurry for CMP used to planarize substrates such as silicon substrates used in semiconductor manufacturing processes and aluminum substrates used in electrostatic chuck manufacturing processes, or polished surfaces such as photomask blanks, glass disks, optical lenses, etc. Polishing slurry for CMP used for polishing, or it can be appropriately selected depending on whether it is a normal polishing slurry used for polishing other polished surfaces, etc., preferably water, or water. The main components are methanol, ethanol, n-propanol, iso-propanol, n-butanol and tert. Alcohols and the like butanol, ketones, esters, aqueous dispersion medium containing a water-soluble solvent such as ethers are preferably used. In addition, an etching solution for performing chemical polishing at the time of CMP is added to the dispersion medium as needed, as in the conventional case.
[0023]
The particle concentration (Cp) of the abrasive fine particles constituting the abrasive slurry of the present invention varies depending on the type of the abrasive fine particles, but in the case of cerium oxide particles, usually 5 to 40% by weight, preferably 5 to 40% by weight. It is 30% by weight, more preferably 5 to 10% by weight, and the particle concentration (Cc) of the colloidal fine particles is usually 0.1 to 5% by weight, in many cases including the case of colloidal silica. Is preferably 0.5 to 2% by weight, and the weight ratio (Cc / Cp) of the abrasive fine particles to the colloidal fine particles is 1 or less, preferably 0.5 or less. The abrasive slurry prepared with such particle concentrations (Cp) and (Cc) has the same particle concentration (Cp) and (Cc) or, if necessary, a predetermined particle concentration (Cp) with a dispersion medium. And diluted to (Cc) and used for polishing such as CMP. If the particle concentration (Cp) of the polishing fine particles is lower than 5% by weight, the polishing ability is insufficient, and if it is higher than 40% by weight, there is a problem in solubility. On the other hand, when the particle concentration (Cc) of the colloidal fine particles is lower than 0.1% by weight, the effect of suppressing sedimentation / aggregation is reduced. On the contrary, when the particle concentration is higher than 5% by weight, the aggregation phenomenon is liable to occur. Further, when the weight mixing ratio (Cc / Cp) of the abrasive fine particles and the colloidal fine particles exceeds 1, the aggregation phenomenon tends to occur.
[0024]
The abrasive slurry of the present invention can be used for a long time without adding an organic dispersant such as a water-soluble organic polymer, a water-soluble anionic surfactant, a water-soluble nonionic surfactant and a water-soluble amine. It has excellent dispersion stability over the entire surface, has good redispersibility, and can solve the problems of sedimentation and aggregation as much as possible.
[0025]
In the present invention, the method for preparing an abrasive slurry also includes a slurry in which the constituent fine particles, the colloidal fine particles and the dispersion medium are uniformly mixed, and the polishing fine particles and the colloidal fine particles are uniformly dispersed in the dispersion medium. There is no particular limitation, and it can be prepared using a normal stirrer.If necessary, an ultrasonic disperser, a homogenizer, a ball mill, a vibrating ball mill, a planetary ball mill, and a wet disperser such as a medium stirring mill may be used. it can.
[0026]
The abrasive slurry of the present invention is used not only for flattening a substrate such as a silicon substrate used in a semiconductor manufacturing process or an aluminum substrate used in an electrostatic chuck manufacturing process, but also for a silicon oxide insulating film formed on a wiring board having predetermined wiring. Oxide film such as glass, inorganic insulating film such as silicon nitride, optical glass such as photomask, lens, prism, etc., inorganic conductive film such as ITO, optical integrated circuit and optical switching element composed of glass and crystalline material. Optical waveguide, end face of optical fiber, optical single crystal such as scintillator, solid laser single crystal, LED sapphire substrate for blue laser, semiconductor single crystal such as SiC, GaP, GaAs, glass for magnetic disk It is used for polishing a substrate, a magnetic head and the like.
[0027]
For example, for a substrate in which an oxide film such as a silicon oxide insulating film is formed on a substrate such as a semiconductor substrate in which a circuit element and an aluminum wiring are formed or a semiconductor substrate in which a circuit element is formed, When performing CMP for the purpose of flattening to eliminate surface irregularities, a general polishing apparatus including a holder for holding a substrate and a rotating plate to which a polishing cloth (pad) is attached is used. , The polishing slurry of the present invention can be continuously supplied at a constant rate by a pump or the like, and can be polished under a predetermined number of rotations and pressure.
[0028]
Then, as in the case of the ordinary post-treatment, the substrate after the polishing is thoroughly washed in running water, and after removing water droplets attached to the substrate using a spin drier or the like, the substrate is dried.
Since the waste liquid discharged during the polishing of the substrate is free of a dispersant without using any organic dispersant, the waste liquid can be treated extremely economically as compared with the related art.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be specifically described based on examples and comparative examples.
[0030]
Examples 1-27
[Preparation of colloidal silica (20 nm)]
32 kg of methyl silicate, 100 kg of methanol and 768 kg of pure water were charged into a jacketed 1 m ³ -tank equipped with a liquid outlet, a liquid level controller and a stirrer, and mixed to obtain a liquid A.
Further, 368 kg of methyl silicate, 100 kg of methanol, 1840 g of pure water and 12 kg of 28 wt% -ammonia water were charged into a 3 m ³ -tank equipped with a stirrer, and mixed to obtain a liquid B.
[0031]
Next, the tank containing the liquid A is steam-heated to distill a mixed liquid of methanol and water, and when the liquid starts to be distilled from the liquid A, the liquid B is added so that the liquid level of the liquid A becomes constant. Then, when all the liquid B was added, 240 kg of pure water was further added so that the liquid level of the liquid A became constant and reacted.
After the completion of the reaction, the reaction product was taken out of the tank containing the solution A and analyzed. As a result, a colloidal silica product (colloidal silica (20 nm) having a silica concentration of 20% by weight and an average particle diameter of 20 nm was obtained. )Met.
[0032]
[Preparation of colloidal silica (70 nm)]
1721.7 kg of methanol, 306.3 kg of pure water and 88.4 kg of 28 wt% -ammonia water were charged into a jacketed 3 m ³ -tank equipped with a stirrer, mixed, and then the liquid temperature was adjusted to 23 ± 1 ° C. While maintaining the liquid temperature at 23 ± 1 ° C., 404.4 kg of methyl silicate was charged and reacted over 2 to 2.5 hours with stirring.
[0033]
After completion of the reaction, the crude product EkiTome outlet of the obtained reaction mixture, jacketed 1 m 3 equipped with a liquid level control device and a stirrer ^- transferred to the tank, and a steam heating tank methanol, mixture of water and ammonia Distill, add the remaining reaction mixture so that the liquid level becomes constant when the liquid starts to distill from the tank, and when all of the reaction mixture has been added, add pure water so that the liquid level becomes more constant. Water was added, and pure water was added until the liquid temperature in the tank reached 100 ° C.
[0034]
When the liquid temperature reached 100 ° C., the heating was terminated, the product was cooled as an intermediate product, and when the liquid temperature reached 70 ° C., an appropriate amount of 28 wt% -ammonia water was added, and the mixture was further stirred and mixed. From the reaction product.
The obtained reaction product was a colloidal silica product (colloidal silica (70 nm)) having a silica concentration of 30% by weight and an average particle size of 70 nm.
[0035]
[Preparation of colloidal silica (170 nm)]
885.1 kg of methanol, 63.1 kg of pure water and 113.25 kg of 28 wt% -ammonia water were charged into a jacketed 1.8 m ³ -tank equipped with a stirrer, mixed, and then adjusted to a temperature of 23 ± 1 ° C. Then, while maintaining the liquid temperature at 23 ± 1 ° C., 171.1 kg of methyl silicate was charged and reacted over 3 hours while stirring.
[0036]
After completion of the reaction, the crude product EkiTome outlet of the obtained reaction mixture, jacketed 1 m 3 equipped with a liquid level control device and a stirrer ^- transferred to the tank, and a steam heating tank methanol, mixture of water and ammonia Distill, add the remaining reaction mixture so that the liquid level becomes constant when the liquid starts to distill from the tank, and when all of the reaction mixture has been added, add pure water so that the liquid level becomes more constant. Water was added, and pure water was added until the liquid temperature in the tank reached 100 ° C.
[0037]
When the liquid temperature reached 100 ° C., the heating was terminated, the product was cooled as an intermediate product, and when the liquid temperature reached 70 ° C., an appropriate amount of 28 wt% -ammonia water was added, and the mixture was further stirred and mixed. From the reaction product.
The obtained reaction product was a colloidal silica product (colloidal silica (170 nm)) having a silica concentration of 22% by weight and an average particle size of 170 nm.
[0038]
(Preparation of abrasive slurry)
Cerium oxide particles having an average particle diameter of 1.1 μm and a maximum particle diameter of 8 μm (trade name: TE-508, manufactured by Seimi Chemical Co., Ltd.) were used as the polishing fine particles, and the three types of colloidal silica obtained above were used as the colloidal fine particles. Pure water was used as a medium, mixed at the ratios shown in Table 1, and uniformly mixed with a stirrer to prepare abrasive slurries of Examples 1 to 27.
[0039]
(Evaluation of precipitation / aggregation state and redispersibility)
With respect to the obtained abrasive slurries of Examples 1 to 27, 50 ml of the slurry was placed in a 100 ml test tube, allowed to stand still for one month, and then visually observed for precipitation and aggregation.
In addition, 50 ml of the abrasive slurry was placed in a 100 ml-polyethylene container and allowed to stand still for one month. Thereafter, the redispersibility by hand movement is visually observed, and the apparatus is laid on a table-type ball mill stirrer (manufactured by Irie Shosha Co., Ltd .: Model V-1M) sideways. The stirring rotation speed is 100 rpm and the stirring time is 10 minutes. The mixture was stirred under the conditions, and the redispersibility by a stirrer was visually observed.
[0040]
The results of the above precipitation / aggregation state and redispersibility
◎: The entire settling portion is soft, can be redispersed in a few seconds by hand, and can be redispersed within 5 minutes by a stirrer.
：: There is a hard part in the sedimentation part, but it takes about 30 seconds for redispersion by hand, and about 10 minutes for redispersion by a stirrer.
Δ: There is a hard part in the sedimentation part, but redispersion by hand requires 2 minutes or more, and redispersion by a stirrer requires about 10 minutes.
×: The entire sedimentation portion was completely solidified and did not re-disperse even if shaked for 10 minutes, and required more than 10 minutes for re-dispersion using a stirrer.
Was evaluated in four steps.
Table 1 shows the results.
[0041]
(Quartz substrate polishing rate)
Further, the polishing slurry was diluted three times with ultrapure water, and the number of rotations was 200 rpm, the processing pressure was 500 g / cm ² , and the polishing machine for polishing (FACT-200 manufactured by Nanofactor) equipped with a polishing cloth was used. The sample (a quartz substrate having a width of 3.3 cm × 2.6 cm and a thickness of 1.15 mm) was polished for 10 minutes under the conditions of a supply rate of the abrasive slurry of 10 ml / min, and the thickness of the sample before and after polishing was measured by a micrometer. The polishing rate (μm / 10 min) for the quartz substrate (SiO ₂ ) was determined from the thickness of the sample before and after polishing.
Table 1 shows the results.
[0042]
Comparative Examples 1 to 15
Using polyvinylpyrrolidone (PVP) as the organic dispersant, the abrasive slurries of Comparative Examples 1 to 15 were prepared in the same manner as in Examples 1 to 27, and the obtained abrasives of Comparative Examples 1 to 15 were obtained. In the same manner as in Examples 1 to 27, the precipitation / aggregation state and redispersibility were evaluated, and the polishing rate (μm / 10 min) for the quartz substrate (SiO ₂ ) was determined.
The results are shown in Table 1 together with the above Examples 1 to 27.
[0043]
[Table 1]

[0044]
As is clear from the results shown in Table 1, each of the abrasive slurries of Examples 1 to 27 of the present invention exhibited excellent performance in evaluation of sedimentation / agglomeration state and redispersibility, and in polishing rate of quartz substrate. On the other hand, the abrasive slurries of Comparative Examples 1 to 3 to which neither the colloidal fine particles nor the dispersant is added cannot be redispersed, the polishing rate is not measured, and 1% by weight or 3% by weight of the dispersant is used. It was found that the abrasive slurries of Comparative Examples 4 to 15 to which only A was added required a long time for re-dispersion, and the abrasive slurries of the present invention had excellent performance especially in the sedimentation / aggregation state and re-dispersibility. did.
[0045]
【The invention's effect】
According to the present invention, the dispersion stability is excellent over a long period of time, the redispersibility is good, the problem of sedimentation / aggregation can be eliminated as much as possible. It is possible to provide an abrasive slurry which can be used without using a dispersant at all.
Further, by using the abrasive slurry of the present invention, substrates such as a silicon substrate used in a semiconductor manufacturing process and an aluminum substrate used in an electrostatic chuck manufacturing process can be industrially advantageously manufactured by CMP.

Claims

Includes abrasive fine particles composed of one or more oxides, colloidal fine particles that are colloidal oxides and have an average particle diameter smaller than the above abrasive fine particles, and a dispersion medium that disperses these abrasive fine particles and colloidal fine particles. An abrasive slurry excellent in dispersion stability, characterized in that:

The average particle diameter (Dp) of the abrasive fine particles is 100 to 5,000 nm, the average particle diameter (Dc) of the colloidal fine particles is 10 to 300 nm, and the average particle diameter (Dp) of the abrasive fine particles is the average of the colloidal fine particles. The abrasive slurry excellent in dispersion stability according to claim 1, wherein a particle size ratio (Dc / Dp) to a particle size (Dc) is 10 or less.

The particle concentration (Cp) of the polishing fine particles is 5 to 30% by weight, the particle concentration (Cc) of the colloidal fine particles is 0.1 to 5% by weight, and the weight mixing ratio (Cc) of the polishing fine particles and the colloidal fine particles is The abrasive slurry having excellent dispersion stability according to claim 1 or 2, wherein / Cp) is 1 or less.

The polishing slurry according to any one of claims 1 to 3, wherein the dispersion medium is water or an aqueous dispersion medium containing water as a main component.

The abrasive slurry having excellent dispersion stability according to any one of claims 1 to 4, wherein the abrasive fine particles are cerium oxide particles.

The abrasive slurry according to any one of claims 1 to 5, wherein the colloidal fine particles are colloidal silica.

A method for producing an inorganic substrate, comprising a polishing step of polishing the substrate using the abrasive slurry according to any one of claims 1 to 6.

The method for manufacturing a substrate according to claim 7, wherein the substrate has an oxide film on a surface thereof.