JP4042906B2

JP4042906B2 - Polishing composition, method for adjusting polishing composition, and polishing method

Info

Publication number: JP4042906B2
Application number: JP2003127626A
Authority: JP
Inventors: 邦明前島; 慎介宮部; 昌宏泉
Original assignee: Nippon Chemical Industrial Co Ltd
Current assignee: Nippon Chemical Industrial Co Ltd
Priority date: 2003-05-06
Filing date: 2003-05-06
Publication date: 2008-02-06
Anticipated expiration: 2023-05-06
Also published as: TW200504188A; JP2004331753A; TWI299058B

Description

【０００１】
【発明が属する技術分野】
本発明は，ガラスディスク，フォトマスク，半導体ウェーハ上のシリカ絶縁膜，光学ガラス等の酸化珪素を主成分とする化合物表面の研磨を行なう研磨用組成物および該研磨用組成物の調製方法，および該研磨用組成物を用いた研磨方法に関する。
【０００２】
【従来の技術】
ガラスディスク，フォトマスク，半導体ウェーハ上のシリカ絶縁膜，光学ガラス等の酸化珪素を主成分とする化合物表面の研磨にはセリア，アルミナ，ヒュームドシリカ，コロイダルシリカなどが用いられてきた。特にセリアはシリカ表面に特異的に作用し極めて高い研磨速度を得ることが出来る。セリアの研磨速度はシリカ系研磨剤の１０倍にもおよびその優位性は確固となっている。
【０００３】
一方，コロイダルシリカはシリコンウェーハの研磨剤として多用されている。このコロイダルシリカ含有研磨剤は数十ナノメータの微細酸化珪素砥粒がｐＨ９〜１２程度のアルカリ水溶液中にコロイド状に分散したもので，酸化珪素粒子による機械的作用と，アルカリ溶液によりシリコンを浸蝕する化学的作用の複合作用によりシリコン精密研磨が行われる。シリコンは柔らかくアルカリにも浸食されやすい材料で，通常のコロイダルシリカと小量のアルカリで容易に研磨でき，逆に，傷（スクラッチ）を付けないことや，余剰の浸食（シミ）を起こさない方に注意が向けられている。
【０００４】
これに比べて，ガラスディスク，フォトマスク，半導体ウェーハ上のシリカ絶縁膜，光学ガラス等の表面は非常に硬く，仕上げ研磨だけで比較してもウェーハの１０倍以上の研磨時間，薬剤消費が必要になる。研磨剤に粒子径の大きいシリカを使うとか，シリカを高濃度で使用するとかｐＨを１１以上にするほどの高濃度のアルカリを使用するなどの力ずくの手段は講じられてはいるが，研磨コストを高くするばかりで合理的と言える状態ではない。
【０００５】
一般的な，ガラスディスク，フォトマスク，半導体ウェーハ上のシリカ絶縁膜，光学ガラス等の工程は，合成樹脂発泡体あるいはスウェード調合成皮革等よりなる研磨布を展張した定盤上に被研磨物を載置し，押圧回転しつつ，酸化セリウム，コロイダルシリカなどの研磨剤を定量的に供給しながら研磨を行なう方法が一般的である。
【０００６】
研磨用組成物としてシリコンを研磨対象にした出願は多く，アルカリ成分を含んだ溶液に微細なコロイド状酸化珪素粒子を分散した溶液を使用する基本技術が提示されている（例えば，特許文献１参照）。この研磨は，その前までの，例えばダイヤモンド砥石を使用したり，あるいは硬質なアルミナ系砥粒を用いた所謂機械的な研磨とは異なるものであって，その成分であるアルカリの化学的作用，具体的にはウェーハ等に対する浸蝕性を応用したものである。すなわち，アルカリの腐食性により，ウェーハ等の表面に薄い軟質の浸蝕層が形成される。その薄層を微細なコロイド状酸化珪素粒子の機械的作用により除去してゆくことにより研磨が進むのである。研磨用組成物溶液のｐＨは，溶液が持つアルカリ成分の化学的作用により研磨が進むのであるから，ｐＨが７以上のアルカリ性領域になければならない。すなわちｐＨが７の中性を示す数値に近くなるにつれその化学作用の力は弱くなり，研磨速度は遅くなるし，また，ｐＨ１４に近い強アルカリ領域になるに従ってその力は強くなり研磨速度は速くなる。
【０００７】
従って，このような研磨においては，研磨用組成物溶液の性質が極めて重要なファクターとなり，その性状や性質，具体的にはその浸食層の生成速度とそれを除去する研磨速度がバランス良く設計されていて，経時変化や温度変化などの外的要因に対して安定でなくてはならない。特にｐＨが安定した範囲にあることが大変重要である。また，前記浸蝕層は，研磨用組成物中に含有されるコロイド状酸化珪素粒子の機械的作用によって除去されるのであるから，その粒子は適度なサイズを有するものでなくてはならない。
【０００８】
従来，様々な研磨用組成物がウェーハ等の研磨剤として提案されている。シリカ粒子に関しては，シリカゾルおよびシリカゲルが研磨剤として提案されている（例えば，特許文献２参照）。また，半導体ウェーハの絶縁層（シリカ膜）の研磨剤としてフュームドシリカの水性分散スラリーの使用が提案されている（例えば，特許文献３参照）。細長く歪んだ球状のシリカ粒子からなるコロイダルシリカが高い研磨速度を示すことが（例えば，特許文献４参照），また，球が数珠状につながった形体のシリカ粒子からなるコロイダルシリカが高いシリコン研磨速度を示すことが開示されている（例えば，特許文献５参照）。
２種類以上の粒径の混合系については古くからサイトン（Ｓｙｔｏｎ）という製品が市販されており，平均粒子径は４０ｎｍだが１０〜２００ｎｍのブロードな粒子分布であることが特徴になっている（これの使用については特許文献６および７参照）。粒子が任意に混合された物か製法上の偶然なのかは判然としないが，この製品の研磨速度が高いことは近年見直されている。しかし，小さすぎる粒子の存在は他の薬品との混合安定性を悪くしており，大きすぎる粒子の存在はスクラッチの発生や配線溝への填り込みなどの懸念を抱えており，次世代への改良の必要性がある。特許文献8には，サイトンとよく似た２種類以上の粒径の混合系の使用が記載されている。それには，大きすぎる粒子の存在はないが，２種類以上の粒径の混合系であれば良いとされており，どのような量比かは範囲が広すぎて判然とせず，サイトンを無意識に使用していた旧来の技術からの進歩は見られない。
また，本発明者らは１５〜３０ｎｍと６０〜１００ｎｍの２種類の粒径の特定量比混合系の研磨組成物がシリコン研磨に高い性能を発揮することを見出し，すでに出願を行っている。
ガラスのような硬質シリカ表面の研磨にコロイダルシリカが必要とされてきたのは比較的最近で，シリカ表面に残留しやすいセリア粒子を研磨除去するのを目的としてコロイダルシリカを使用する方法が提案されている（例えば，特許文献９および１０参照）。また，ダイヤモンド砥石でガラスを研磨するときにコロイダルシリカを水の代わりに使用すると傷の少ない平坦なラッピングが出来ることが提案されている（例えば特許文献１１参照）。しかしながら，いずれもシリカ粒子や薬液に関する技術的探求がなされておらず，コロイダルシリカに高い研磨性能を発揮させるには至っていない。
【０００９】
一方，液組成においてはシリコンを研磨対象にして非常に多くの提案がなされている。上記特許文献１では，該懸濁液のｐＨを１０．５〜１２．５の範囲内にすることにより，研磨速度が増大する事が開示されている。また，アミン類を添加した研磨用組成物（例えば，特許文献１２参照），水，コロイダルシリカ，分子量１０万以上の水溶性高分子，水溶性塩類からなる研磨用組成物（例えば，特許文献１３参照）が提案されている。さらに水溶性アミンの一種であるピペラジンを，シリカゾルまたはシリカゲルのシリカ基準にて，１０〜８０重量％含む研磨用組成物を使用した研磨方法が提案されている（例えば，特許文献１４参照）。しかしながら，これら提案されている方法は，アルカリ性の母液にコロイダルシリカあるいはシリカゲル等の微細粒子からなる研磨剤を分散させた基本構造の溶液に，様々な添加剤を加えることにより研磨剤の分散性を上げたり，研磨の安定性を図ったりするものであって，従来の研磨用組成物の研磨速度を画期的に改善するようなものではない。
【００１０】
そこで，酸解離定数の逆数の対数値が８．０〜１２．０の弱酸および／または弱塩基を使用して，弱酸と強塩基，強酸と弱塩基あるいは弱酸と弱塩基の何れかの組み合わせのものを添加することによりｐＨの緩衝作用を有する緩衝溶液としたコロイダルシリカ組成物が提案されている。（例えば，特許文献１５，１６，１７および１８参照）緩衝液の使用は，外的条件の変化によるｐＨの変化が少なく，繰り返し使用においても変化の少ない安定した研磨用組成物を提供しているが，ｐＨが低くなる分だけ研磨速度が低くなり，また，それを改善するために緩衝液を構成する成分の濃度を高くすると，コロイドの安定性が悪くなり経時的に粘度が高くなり，最終的にはゲル化を起こし，安定使用できる商品にはならない。
【００１１】
集積回路上のチタンを研磨する方法としてフッ化カリを含有する酸性シリカスラリーが知られているが（例えば特許文献１９参照），アルカリ性でシリカを研磨する方法には触れていない。シリカ表面をフッ素イオンで浸食する方法は各分野で実施されており周知の技術であるが，フッ素イオン含有のコロイダルシリカ組成物は本発明者らの先願に見られるだけである。これはコロイドの安定性が確保できないためであり，研磨時に添加してその日の内に使い切ってしまう方法が採用されている。
【００１２】
【特許文献１】
米国特許第３３２８１４１号明細書
【特許文献２】
米国特許第３１７０２７３号明細書
【特許文献３】
米国特許第４９１０１５５号明細書
【特許文献４】
特開平７−２２１０５９号公報
【特許文献５】
特開２００１−１１４３３号公報
【特許文献６】
米国特許第３４８５６０８号明細書
【特許文献７】
米国特許第４０５７９３９号明細書
【特許文献８】
特開２００２−３０２７４号公報
【特許文献９】
特開２０００−３４３３９０号公報
【特許文献１０】
特開２００１−３０８０５０号公報
【特許文献１１】
特開２００１−３１５０６１号公報
【特許文献１２】
米国特許第４１６９３３７号公報
【特許文献１３】
特開平２−１５８６８４号公報
【特許文献１４】
特開平５−１５４７６０号公報
【特許文献１５】
特開平１１−３１５２７３号公報
【特許文献１６】
特開平１１−３０２６３５号公報
【特許文献１７】
特開平１１−３０２６３４号公報
【特許文献１８】
特開２０００−１５８３２９号公報
【特許文献１９】
米国特許第５３４０３７０号明細書
【００１３】
【発明が解決しようとする課題】
特に，近年電子回路の高集積化およびウェーハ自体の大型化に伴いガラスディスク，フォトマスク，半導体ウェーハ上のシリカ絶縁膜，光学ガラス等の高度な平坦化が必須となっている。さらに，生産効率を向上させるため，研磨速度が高くかつ安定しており，コストメリットの高い研磨用組成物および研磨方法が望まれている。
【００１４】
本発明者等は上述の，従来の研磨用組成物が持つ問題点に鑑み，鋭意研究を行ない，研磨用組成物溶液として，特定の粒度を有する酸化珪素の粒子を含むコロイド，すなわちコロイダルシリカのアルカリ性水溶液であって，ｐＨの緩衝作用を有し，特定のイオン構成を構築することで，安定した高速加工が達成されることを見出し，本発明を完成するに至ったものであり，その目的となすところはｐＨの変化が少なく，かつ研磨速度が高速で，繰り返し使用においても変化の少ない安定した研磨を行うことができる研磨用組成物を提供することおよび該研磨用組成物を用いた酸化珪素を主成分とする表面の研磨方法を提供することにある。
【００１５】
【問題を解決するための手段】
上述の目的は、ガラスディスク、フォトマスク、半導体ウェーハ上のシリカ絶縁膜又は光学ガラスの酸化珪素を主成分とする化合物表面の研磨を行なう研磨用組成物であって、小さい粒子と大きい粒子との２種類の酸化珪素粒子を含み、該小さい粒子は平均一次粒子径が４０ｎｍ以上６０ｎｍ以下で、該大きい粒子は平均一次粒子径が６０ｎｍを超え１００ｎｍ以下で、該小さい粒子と該大きい粒子とは重量比において１：０．０５〜１：０．３の割合で存在し、かつ研磨用組成物全体に対する酸化珪素粒子の濃度が５重量％以上２０重量％未満の範囲にあるコロイド溶液から成り、該コロイド溶液が、ｐＨ９．７〜１０．７の間で緩衝作用を有する塩の溶解した緩衝溶液として調製され、更に、フッ素イオンもしくはフッ素が配位した陰イオンをフッ素として０．０１〜０．１ｍｏｌ／ｋｇ−ＳｉＯ _２含有する研磨用組成物を使用することによって達成できる。
【００１７】
本発明の他の目的は，研磨布を展張した定盤上にシリカ表面を有する被研磨物を載置し，押圧回転しつつ研磨剤を供給しながら被研磨物の主面の研磨を行なう方法，又は表面に研磨布を貼付した研磨部材を有する研磨装置を使用して，該研磨部材に酸化珪素を主成分とする表面を有する被研磨物の端面を接触させ，研磨部材および／または被研磨物を回転させながら，上述の研磨用組成物を端面部分に定量的に供給して，被研磨物の研磨を行なう方法により達成される。
【発明の実施の形態】
【００１８】
本発明による研磨用組成物は、平均一次粒子径が４０ｎｍ以上６０ｎｍ以下と、６０ｎｍを超え１００ｎｍ以下の明確に区別できる２種類の酸化珪素粒子が重量比において１：０．０５〜１：０．３の割合で存在し、かつ研磨用組成物全体に対する酸化珪素粒子の濃度が５重量％以上２０重量％未満の範囲にあるコロイド溶液から成り、該コロイド溶液が、ｐＨ９．７〜１０．７の間で緩衝作用を有する塩の溶解した緩衝溶液として調製された研磨用組成物である。
【００１９】
本発明は，研磨対象の材質とそれを浸食するのに適切な薬剤を選定したうえで最も高い研磨速度を示した酸化珪素粒子を特定した物であり，さらにその組成物に改良を加えた物である。
主たる酸化珪素粒子は粒子径の小さい酸化珪素粒子で，これに大きい粒子径の酸化珪素粒子が小量加えられた混合粒子系である。小さい方の酸化珪素粒子が３０ｎｍより小さいと研磨速度が不足し，大きい方の粒子が１００ｎｍより大きいと，研磨用組成物としての性能に影響はないが，粗大粒子が沈降し製品の経時安定性確保が難しくまた，価格的にも不利である。また，２種類の中間の粒子径の酸化珪素が存在しても，小さい粒子だけの場合と研磨特性に変わりがなく，価格的に不利になるだけのため，存在しない方がよい。
【００２０】
重量比が１：０．０５〜１：０．３であることが必要である。４０ｎｍ以上６０ｎｍ以下の粒子径の酸化珪素粒子だけの場合および６０ｎｍを超え１００ｎｍ以下の粒子径の酸化珪素粒子だけの場合のいずれと比較しても、重量比が１：０．０５〜１：０．３の混合粒子系は研磨速度が高いことが見出された。６０ｎｍを超え１００ｎｍ以下の粒子径の酸化珪素粒子が重量比０．０５未満では、研磨速度向上効果が不十分であり０．３より多いと逆効果が発現する。この現象を図１にグラフで記載した。
【００２１】
図１は、研磨用組成物全体に対する酸化珪素粒子の濃度が１０重量％でｐＨが１０．３のコロイド溶液を用い、大きな粒子（８０ｎｍの粒子径の粒子）と小さな粒子（４０ｎｍの粒子径の粒子）の重量比を変化させたときの白ガラス表面の研磨速度（研磨レート；ｎｍ／ｍｉｎ）を示したものである。小さな粒子のみ、あるいは大きい粒子のみでは１２０ｎｍ／ｍｉｎ程度の研磨速度しか出ないが、小さな粒子に大きな粒子を僅かに添加することで、研磨速度が著しく向上し最高２７０ｎｍ／ｍｉｎ程度の研磨速度が得られている。つまり２種の粒子の配合比と研磨速度は直線的な関係にあるのではなく，特定配合域に極大値があることが見いだされた。このような事例は未だ開示されたことが無く，本発明の最大構成要素である。
【００２２】
本発明において、酸化珪素の研磨用組成物に対する濃度は、実際の研磨時において酸化珪素粒子の濃度が５重量％以上２０重量％未満であることが肝要であり、この範囲に於いて研磨対象の種類により、許容される研磨時間により濃度を決定することが出来る。一般に、研磨剤の濃度が高いほど研磨速度は高いが、研磨剤の濃度と研磨量は比例しない。低い濃度で長時間研磨する方が研磨剤の消費は少なくて済む。しかし、５重量％未満ではいたずらに時間ばかり掛かり現実的ではなく、２０重量％以上で高濃度化による効果が弱まり、研磨剤消費が経済性に不利になってくる。４０重量％より高濃度では、研磨部位以外に付着したコロイドが乾燥しやすく、乾燥したシリカ粉が研磨部位に運ばれるとスクラッチを生じ不良品発生の原因となりやすい。
【００２３】
本発明においては研磨用組成物のｐＨはｐＨ９．７〜１０．７の範囲にあることが肝要である。ｐＨが９．７未満であると研磨速度は著しく低下して実用の範囲から外れる。また、ｐＨが１０．７より高いと、酸化珪素粒子の凝集がはじまるため研磨用組成物の安定性が低下しこれも実用の範囲から外れる。
そしてまた、このｐＨは摩擦、熱、外気との接触あるいは他の成分との混合等、考えられる外的条件の変化により容易に変化するようなものであってはならないが、本発明においては研磨用組成物の溶液自体を、ｐＨの変化の幅が少ない所謂緩衝作用の強い液とすることが要件になっている。
【００２４】
本発明の緩衝溶液を形成するイオンとしては，陰イオンは一例をあげると，塩酸，硝酸，フッ酸，硫酸などの強酸やホウ酸，炭酸，燐酸および水溶性の有機酸等の弱酸があげられ，またその混合物であってもかまわない。特に好適なのは炭酸イオンもしく炭酸水素イオンである。陽イオンとしては，ナトリウム，カリウム等のアルカリ金属イオン，アンモニウム，コリン，テトラメチルアンモニウム等のアンモニウムイオン，エチレンジアミン，ピペラジン等のアミン類イオンなど水酸イオンと対をなしてアルカリ性を示すもので，それらの混合物でも良い。特にカリウムイオンやテトラメチルアンモニウムイオンやそれらの混合物が好ましい。本発明で述べる緩衝溶液とは，上述のイオンの組み合わせで形成され，酸，アルカリ，塩として添加され，イオンとして解離している状態および，未解離の状態が共存している溶液を示し，少量の酸または，塩基が混入してもｐＨの変化が少ないことが特徴である。
【００２５】
さらに本発明の組成物は上記の組成物の成分にフッ素イオンもしくはフッ素が配位した陰イオンをフッ素として０．０１〜０．１ｍｏｌ／ｋｇ−ＳｉＯ₂含有させることが出来る。この研磨用組成物は研磨速度をさらに高くすることが出来る。フッ素イオンはフッ酸として添加しても良く，上記の各塩基のフッ化物として添加することもできる。フッ素が配位した陰イオンとしては，テトラフルオロホウ酸イオンやヘキサフルオロ珪酸イオンが良い。これらは酸化珪素１５〜６５重量％の濃厚原液に添加しておくこともできるが，原液を使用の都度希釈して調整するときに添加しても良い。フッ素イオンもしくはフッ素が配位した陰イオンをフッ素として０．０１ｍｏｌ／ｋｇ−ＳｉＯ₂以下では充分な研磨速度は得られない。０．１ｍｏｌ／ｋｇ−ＳｉＯ₂以上の添加は，浸食が強すぎて平坦な鏡面を得ることが出来ない。好ましくは０．０１〜０．０６ｍｏｌ／ｋｇ−ＳｉＯ₂である。
【００２６】
上記の研磨方法では，研磨用組成物の定量供給液は１回使用で廃棄しても良いが，経済的には不利であり，供給液に戻して循環使用する事が好ましい。すなわち，一定量の研磨用組成物を循環させて研磨装置の研磨部に供給し，複数枚の研磨対象を研磨する方法が経済的で良い。
【００２７】
本発明の研磨用組成物の物性を改良するため，界面活性剤，分散剤，沈降防止剤，研磨促進剤などの添加剤を併用することができる。界面活性剤，分散剤，沈降防止剤，研磨促進剤としては，水溶性の有機物，無機層状化合物，フッ素系塩類などがあげられる。また，本発明の研磨用組成物は水溶液としているが，有機溶媒を添加してもかまわない。本発明の研磨用組成物は，研磨時にコロイダルシリカおよび，塩基と添加剤と水を混合して調製してもよい。また，一般的には酸化珪素粒子の濃度が２５〜６５重量％の範囲にある組成物を調製しておき，水あるいは，水と有機溶媒の混合物で希釈して使用することが多い。
【００２８】
次に実施例および比較例をあげて本発明の研磨用組成物、およびそれを用いた研磨方法を具体的に説明するが、特にこれにより限定を行なうものではない。なお、実施例１〜９および実施例１１は参考例である。
実施例および比較例において使用する研磨用組成物は以下の方法にて調製した。平均一次粒子径が４０ｎｍと８０ｎｍのコロイダルシリカ（濃度４０重量％）は市販品を使用した。それぞれの平均一次粒子径は、酸化珪素の比表面積を窒素吸着ＢＥＴ法で測定し、酸化珪素粒子を真球と仮定して算出し、その値が４０ｎｍと８０ｎｍであることを確認した。また、ＴＥＭ写真により、最大粒子と最小粒子が平均粒子径の±２０％の範囲にあり、粒度分布の極めて狭いことを確認した。
【００２９】
緩衝液を構成する成分には，水酸化テトラメチルアンモニウムは市販の２０％水溶液を使用し，炭酸水素カリウム，炭酸水素ナトリウム，炭酸ナトリウム，水酸化ナトリウム，フッ化カリウムは試薬を使用した。
緩衝液を構成する成分はあらかじめ純水に溶解しておき，これをコロイダルシリカに添加し，最後に純水を加えて所定の酸化珪素濃度となるよう調製し，これを使用液とした。緩衝液を構成する成分の使用量は，研磨組成物中の酸化珪素１ｋｇに添加したモル数（ｍｏｌ／ｋｇ−ＳｉＯ₂）で示した。また，フッ化カリウムは最後に加える純水に溶解して調製した。
【００３０】
【実施例】
［実施例１〜２および比較例１〜３］
光学用白板ガラスの表面研磨の例を以下に記載する。白板ガラスは市販品を使用し予めサンドペーパーにて角落とし縁研磨した物を用いた。表１に示した内容の研磨剤組成物を使用して研磨試験を実施し、その結果を表１に記載した。研磨組成物のｐＨはｐＨメーターを用いて測定し、研磨速度は研磨前後の白板ガラスの重量差より求め厚さ変化に換算した。
【００３１】
研磨条件は以下の方法で鏡面研磨を実施した。
＜研磨条件＞
研磨装置：定盤径２００ｍｍ，片面研磨装置
定盤回転速度：１５０ｒｐｍ
研磨布：Ｓｕｂａ４００（ロデール社製）
荷重：２２３ｇ／ｃｍ２
研磨組成物流量：２０ｍｌ／分
研磨時間：１０分
被加工物：白板ガラス
実施例および比較例で明らかなように，小さい粒子に大きい粒子を特定量配合することで著しく研磨速度が高くなることが判明した。
【００３２】
【表１】

【００３３】
［実施例３〜６および比較例４〜７］
青板ガラスの表面研磨の例を以下に記載する。青板ガラスは予めセリア研磨材（スピードファム株式会社社ＣＯ＃ＳＦ６２０）で研磨した物を用いた。表２に示した内容の研磨剤組成物を使用して研磨試験を実施し，その結果を表２に記載した。
【００３４】
研磨条件は以下の方法で鏡面研磨を実施した。
＜研磨条件＞
研磨装置：定盤径６５０ｍｍ，両面研磨装置
下定盤回転速度：３０ｒｐｍ
研磨布：Ｓｕｂａ４００（ロデール社製）
荷重：１５０ｇ／ｃｍ２
研磨組成物流量：３００ｍｌ／分
研磨時間：７分
被加工物：２．５インチ，青板ガラスディスク
【００３５】
研磨組成物のｐＨはｐＨメーターを用いて測定した。研磨面の評価は，集光灯下で肉眼にてヘイズの発生状態を観察した。研磨速度は，研磨前後の青板ガラスディスクの重量差より求め厚さ変化に換算した。
【００３６】
実施例３〜６で明らかなように，小さい粒子に大きい粒子を特定量配合することで著しく研磨速度が高くなることが判明した。比較例４では小さい粒子のみおよび比較例５〜７では大きい粒子の配合比を高くしており研磨速度が著しく低くなっている。
【００３７】
【表２】

【００３８】
［実施例４〜６および比較例５〜８］
結晶化ガラスディスクの表面研磨の例を以下に記載する。結晶化ガラスディスクは予めセリア研磨材（スピードファム株式会社販売ＣＯ＃ＳＦ６２０）で研磨した物を用いた。表３に示した内容の研磨剤組成物を使用して研磨試験を実施し，その結果を表３に記載した。
【００３９】
研磨条件は以下の方法で鏡面研磨を実施した。
＜研磨条件＞
研磨装置：定盤径６５０ｍｍ，両面研磨装置
下定盤回転速度：３０ｒｐｍ
研磨布：Ｓｕｂａ４００（ロデール社製）
荷重：１５０ｇ／ｃｍ２
研磨組成物流量：３００ｍｌ／分
研磨時間：７分
被加工物：２．５インチ，結晶化ガラスディスク
【００４０】
研磨組成物のｐＨはｐＨメーターを用いて測定した。研磨面の評価は，集光灯下で肉眼にてヘイズの発生状態を観察した。研磨速度は，研磨前後の結晶化ガラスディスクの重量差より求め厚さ変化に換算した。
【００４１】
比較例８と実施例７を比べて明らかなように，小さい粒子に大きい粒子を小量配合することで著しく研磨速度が高くなる。また，実施例７〜９を比べて明らかなように，ｐＨも重要な因子であり，高いほど研磨速度は高くなるが，逆に常に同じ研磨速度を得るためにはｐＨが変動しないことが必要であることが判った。実施例１０と比較例９ではフッ素イオンの効果が明らかとなっている。フッ素イオンは研磨を促進するが，過大な量は浸食が強すぎてヘイズの発生原因になる。実施例１０では酸化珪素粒子の濃度を高くすることで低いｐＨでも研磨が行えることが示された。一方，比較例１１では酸化珪素粒子の濃度を低くした場合，添加剤を多くしても充分な研磨が行えないことが示された。
【００４２】
【表３】

【００４３】
なお，本発明は，上記実施形態に限定されるものではない。上記実施形態は，例示であり，本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し，同様な作用効果を奏するものは，いかなるものであっても本発明の技術的範囲に包含される。
【００４４】
例えば，上記研磨工程ではガラスの研磨について例示したが，画像表示用フラットパネルやシリコン酸化膜の研磨にも本発明の研磨剤は使用することができる。
【００４５】
【発明の効果】
以上の説明で示される通り，本発明の研磨組成物は，平均一次粒子径が４０〜６０ｎｍと，６０〜１００ｎｍの明確に区別できる２種類の酸化珪素粒子が重量比において１：０．０５〜１：０．３の割合で存在し，かつ研磨用組成物全体に対する酸化珪素粒子の濃度が５〜４０重量％の範囲にあるコロイド溶液から成り，該コロイド溶液が，ｐＨ９．７〜１０．７の間で緩衝作用を有する塩の溶解した緩衝溶液として調製されたものであり，この組成物は小さい粒子に大きい粒子を特定量配合すると研磨速度が著しく高くなるという発明を基盤とし，さらにｐＨを緩衝作用を利用して安定化しており，例えばこれを用いてシリカガラスの表面の研磨を行った場合，研磨速度が速く，かつ研磨表面状態が良好であり，従来の問題点を大きく改善することができた。さらに本発明の組成物は上記の組成物の成分にフッ素イオンもしくはフッ素が配位した陰イオンをフッ素として０．０１〜０．１ｍｏｌ／ｋｇ−ＳｉＯ₂含有させることでより高い研磨速度を得ることが出来る。
【図面の簡単な説明】
【図１】大きな粒子と小さな粒子との重量比を変化させた研磨用組成物を用いて，白ガラス表面（主面）を研磨したときの研磨速度（ｎｍ／ｍｉｎ）を示すグラフである。[0001]
[Technical field to which the invention belongs]
The present invention relates to a polishing composition for polishing a surface of a compound containing silicon oxide as a main component, such as a glass disk, a photomask, a silica insulating film on a semiconductor wafer, or optical glass, and a method for preparing the polishing composition, and The present invention relates to a polishing method using the polishing composition.
[0002]
[Prior art]
Ceria, alumina, fumed silica, colloidal silica, and the like have been used for polishing a compound surface mainly composed of silicon oxide such as a glass disk, a photomask, a silica insulating film on a semiconductor wafer, and optical glass. In particular, ceria acts specifically on the silica surface and can obtain an extremely high polishing rate. The polishing rate of ceria is 10 times that of silica-based abrasives, and its superiority is firm.
[0003]
On the other hand, colloidal silica is widely used as a polishing agent for silicon wafers. This colloidal silica-containing abrasive is a colloidal dispersion of fine silicon oxide abrasive grains of several tens of nanometers in an alkaline aqueous solution having a pH of about 9 to 12, and erodes silicon by the mechanical action of silicon oxide particles and the alkaline solution. Silicon precision polishing is performed by the combined action of chemical action. Silicon is a material that is soft and easily eroded by alkali, and can be easily polished with normal colloidal silica and a small amount of alkali. On the contrary, it should not scratch or cause excessive erosion (stain) Attention has been directed to.
[0004]
Compared to this, the surfaces of glass disks, photomasks, silica insulating films on semiconductor wafers, optical glass, etc. are extremely hard, and polishing time and chemical consumption more than 10 times that of wafers are required even by finishing polishing alone. become. Although there have been brute force measures such as using silica with a large particle size for the polishing agent, using silica at a high concentration, or using a high concentration of alkali to make the pH 11 or higher, the polishing cost has been taken. It is not a reasonable state just to raise the value.
[0005]
General processes such as glass discs, photomasks, silica insulating films on semiconductor wafers, and optical glass are used to place an object to be polished on a surface plate with a polishing cloth made of synthetic resin foam or suede-like synthetic leather. In general, polishing is performed while quantitatively supplying an abrasive such as cerium oxide or colloidal silica while being mounted and pressed and rotated.
[0006]
There are many applications for polishing silicon as a polishing composition, and a basic technique using a solution in which fine colloidal silicon oxide particles are dispersed in a solution containing an alkali component has been proposed (for example, see Patent Document 1). ). This polishing is different from the so-called mechanical polishing using, for example, a diamond grindstone or a hard alumina-based abrasive grain before that, and the chemical action of its constituent alkali, Specifically, it applies the erodibility to a wafer or the like. That is, a thin soft erosion layer is formed on the surface of a wafer or the like due to the corrosiveness of alkali. Polishing proceeds by removing the thin layer by the mechanical action of fine colloidal silicon oxide particles. The pH of the polishing composition solution must be in an alkaline region where the pH is 7 or higher because polishing proceeds by the chemical action of the alkaline component of the solution. That is, as the pH approaches a value indicating neutrality of 7, the chemical action force becomes weaker, the polishing rate becomes slower, and the force becomes stronger and the polishing rate becomes faster as it becomes a strongly alkaline region close to pH14. Become.
[0007]
Therefore, in such polishing, the property of the polishing composition solution is an extremely important factor, and its properties and properties, specifically, the formation rate of the erosion layer and the polishing rate for removing it are designed in a well-balanced manner. It must be stable against external factors such as changes over time and temperature. In particular, it is very important that the pH is in a stable range. Further, since the eroded layer is removed by the mechanical action of colloidal silicon oxide particles contained in the polishing composition, the particles must have an appropriate size.
[0008]
Conventionally, various polishing compositions have been proposed as polishing agents for wafers and the like. Regarding silica particles, silica sol and silica gel have been proposed as abrasives (see, for example, Patent Document 2). In addition, use of an aqueous dispersion slurry of fumed silica as an abrasive for an insulating layer (silica film) of a semiconductor wafer has been proposed (see, for example, Patent Document 3). Colloidal silica composed of elongated and distorted spherical silica particles exhibits a high polishing rate (see, for example, Patent Document 4), and colloidal silica composed of silica particles in the form of beads connected in a bead shape has a high silicon polishing rate. (For example, refer to Patent Document 5).
For mixed systems of two or more particle sizes, a product called Cyton has been commercially available for a long time, and the average particle size is 40 nm, but it is characterized by a broad particle distribution of 10 to 200 nm (this) (See Patent Documents 6 and 7). It is unclear whether the particles are mixed arbitrarily or accidentally in the manufacturing process, but the high polishing rate of this product has recently been reviewed. However, the presence of particles that are too small has deteriorated the mixing stability with other chemicals, and the presence of particles that are too large has concerns such as the generation of scratches and the insertion into wiring grooves. There is a need for improvement. Patent Document 8 describes the use of a mixed system having two or more types of particle sizes that are very similar to Cyton. For this purpose, there are no particles that are too large, but a mixed system with two or more particle sizes is considered to be acceptable, and the amount ratio is too wide to be understood, making Cyton unconscious. There is no progress from the old technology used.
In addition, the present inventors have found that a polishing composition of a specific quantity ratio mixed system of two kinds of particle sizes of 15 to 30 nm and 60 to 100 nm exhibits high performance for silicon polishing, and has already filed an application.
Colloidal silica has been required for polishing hard silica surfaces such as glass, and a method using colloidal silica has been proposed for the purpose of polishing and removing ceria particles that tend to remain on the silica surface. (For example, see Patent Documents 9 and 10). Further, it has been proposed that when colloidal silica is used instead of water when polishing a glass with a diamond grindstone, flat wrapping with few scratches can be achieved (see, for example, Patent Document 11). However, none of these has been technically searched for silica particles or chemicals, and the colloidal silica has not yet achieved high polishing performance.
[0009]
On the other hand, with respect to the liquid composition, a great number of proposals have been made for silicon as a polishing target. Patent Document 1 discloses that the polishing rate is increased by setting the pH of the suspension within the range of 10.5 to 12.5. Further, a polishing composition (for example, Patent Document 13) comprising an amine added to the polishing composition (for example, see Patent Document 12), water, colloidal silica, a water-soluble polymer having a molecular weight of 100,000 or more, and a water-soluble salt. Have been proposed). Furthermore, a polishing method using a polishing composition containing 10 to 80% by weight of piperazine, which is a kind of water-soluble amine, based on silica sol or silica gel of silica gel has been proposed (for example, see Patent Document 14). However, these proposed methods improve the dispersibility of the abrasive by adding various additives to a solution having a basic structure in which an abrasive composed of fine particles such as colloidal silica or silica gel is dispersed in an alkaline mother liquor. It is intended to increase the stability of the polishing, and does not significantly improve the polishing rate of the conventional polishing composition.
[0010]
Therefore, using a weak acid and / or weak base having a logarithmic value of the reciprocal of the acid dissociation constant of 8.0 to 12.0, any combination of weak acid and strong base, strong acid and weak base, or weak acid and weak base is used. A colloidal silica composition has been proposed in which a buffer solution having a pH buffering action is added by adding a material. (For example, see Patent Documents 15, 16, 17, and 18) The use of a buffer solution provides a stable polishing composition that has little change in pH due to changes in external conditions and little change in repeated use. However, the polishing rate decreases as the pH decreases, and if the concentration of the components constituting the buffer solution is increased to improve it, the stability of the colloid becomes worse and the viscosity increases with time. In reality, gelation occurs and the product cannot be used stably.
[0011]
An acidic silica slurry containing potassium fluoride is known as a method for polishing titanium on an integrated circuit (see, for example, Patent Document 19), but does not mention a method for polishing silica in an alkaline manner. Although the method of eroding the silica surface with fluorine ions is practiced in various fields and is a well-known technique, a fluorine ion-containing colloidal silica composition is only found in the prior application of the present inventors. This is because the stability of the colloid cannot be ensured, and a method is adopted in which it is added during polishing and used up within the day.
[0012]
[Patent Document 1]
U.S. Pat. No. 3,328,141
[Patent Document 2]
U.S. Pat. No. 3,170,273
[Patent Document 3]
US Pat. No. 4,910,155
[Patent Document 4]
Japanese Patent Laid-Open No. 7-221059
[Patent Document 5]
JP 2001-11433 A
[Patent Document 6]
U.S. Pat. No. 3,485,608
[Patent Document 7]
U.S. Pat. No. 4,057,939
[Patent Document 8]
JP 2002-30274 A
[Patent Document 9]
JP 2000-343390 A
[Patent Document 10]
JP 2001-308050 A
[Patent Document 11]
JP 2001-315061 A
[Patent Document 12]
U.S. Pat. No. 4,169,337
[Patent Document 13]
Japanese Patent Laid-Open No. 2-158684
[Patent Document 14]
Japanese Patent Laid-Open No. 5-154760
[Patent Document 15]
JP-A-11-315273
[Patent Document 16]
JP-A-11-302635
[Patent Document 17]
Japanese Patent Laid-Open No. 11-302634
[Patent Document 18]
JP 2000-158329 A
[Patent Document 19]
US Pat. No. 5,340,370
[0013]
[Problems to be solved by the invention]
In particular, with the recent high integration of electronic circuits and the enlargement of the wafer itself, high level planarization of glass disks, photomasks, silica insulating films on semiconductor wafers, optical glass, etc. is essential. Furthermore, in order to improve production efficiency, a polishing composition and a polishing method that have a high and stable polishing rate and high cost merit are desired.
[0014]
In view of the above-mentioned problems of the conventional polishing composition, the present inventors have intensively studied, and as a polishing composition solution, a colloid containing particles of silicon oxide having a specific particle size, that is, colloidal silica. It is an alkaline aqueous solution, has a pH buffering action, and has found that stable high-speed processing can be achieved by constructing a specific ion configuration, and has completed the present invention. The present invention provides a polishing composition capable of performing stable polishing with little change in pH, high polishing rate, and little change even during repeated use, and oxidation using the polishing composition. An object of the present invention is to provide a method for polishing a surface containing silicon as a main component.
[0015]
[Means for solving problems]
  The above objective isA polishing composition for polishing a glass disk, a photomask, a silica insulating film on a semiconductor wafer, or a surface of a compound mainly composed of silicon oxide of optical glass, comprising two types of silicon oxide, small particles and large particles Particles, the small particlesThe average primary particle size is 40nm or more60nmIn,The large particles have an average primary particle size.60over nm100nmIn the following, the small particles and the large particlesIt exists in the ratio of 1: 0.05-1: 0.3 in weight ratio, and the density | concentration of the silicon oxide particle with respect to the whole polishing composition is 520% by weight or moreweight%Less thanThe colloidal solution is prepared as a salt-dissolved buffer solution having a buffering effect between pH 9.7 and 10.7.Furthermore, 0.01 to 0.1 mol / kg-SiO2 with fluorine ion or anion coordinated with fluorine as fluorine ₂ containsThis can be achieved by using a polishing composition.
[0017]
Another object of the present invention is a method of placing an object to be polished having a silica surface on a surface plate on which an abrasive cloth is stretched, and polishing the main surface of the object to be polished while supplying an abrasive while pressing and rotating. Or, using a polishing apparatus having a polishing member with a polishing cloth affixed to the surface, the polishing member and / or the polishing target are brought into contact with the polishing member and the end surface of the object having a surface mainly composed of silicon oxide. This is achieved by a method of polishing the object to be polished by quantitatively supplying the above polishing composition to the end face portion while rotating the object.
DETAILED DESCRIPTION OF THE INVENTION
[0018]
  In the present inventionYoThe polishing composition having an average primary particle size of 40nm or more60nmLess thanAnd 60over nm100nmLess thanThe two types of silicon oxide particles that can be clearly distinguished are present in a weight ratio of 1: 0.05 to 1: 0.3, and the concentration of the silicon oxide particles with respect to the entire polishing composition is 520% by weight or moreweight%Less thanThe colloidal solution is a polishing composition prepared as a salt-dissolved buffer solution having a buffering action between pH 9.7 and 10.7.
[0019]
The present invention specifies silicon oxide particles that show the highest polishing rate after selecting the material to be polished and the appropriate chemicals to erode it, and further improves the composition. It is.
The main silicon oxide particles are silicon oxide particles having a small particle diameter, and a mixed particle system in which a small amount of silicon oxide particles having a large particle diameter is added thereto. When the smaller silicon oxide particles are smaller than 30 nm, the polishing rate is insufficient. When the larger silicon particles are larger than 100 nm, the performance as a polishing composition is not affected, but the coarse particles settle and the product is stable over time. It is difficult to secure and also disadvantageous in price. Also, even if there are two types of silicon oxides with an intermediate particle size, it is better not to have them because the polishing characteristics remain the same as when only small particles are used, and the price is disadvantageous.
[0020]
  It is necessary that the weight ratio is 1: 0.05 to 1: 0.3.40nm or more60nmLess thanOnly silicon oxide particles with a particle size ofofCase and 60over nm100nmLess thanOnly silicon oxide particles with a particle size ofofCompared to any of the cases, it was found that the mixed particle system having a weight ratio of 1: 0.05 to 1: 0.3 has a high polishing rate. 60over nm100nmLess thanIf the silicon oxide particles having a particle diameter of less than 0.05 are less than 0.05 in weight ratio, the effect of improving the polishing rate is insufficient. This phenomenon is shown graphically in FIG.
[0021]
  FIG. 1 shows a colloidal solution having a concentration of silicon oxide particles of 10% by weight and a pH of 10.3 with respect to the whole polishing composition. Large particles (particles having a particle size of 80 nm) and small particles (particles having a particle size of 40 nm) are used. It shows the polishing rate (polishing rate; nm / min) of the white glass surface when the weight ratio of the particles is changed. Only small particles or only large particles give a polishing rate of about 120 nm / min. However, by adding a small amount of large particles to small particles, the polishing rate is remarkably improved and a polishing rate of up to about 270 nm / min is obtained. EtPleaseYes. In other words, it was found that the mixing ratio of the two kinds of particles and the polishing rate were not in a linear relationship, but had a maximum value in a specific mixing area. Such a case has not yet been disclosed and is the largest component of the present invention.
[0022]
  In the present invention, the concentration of silicon oxide with respect to the polishing composition is such that the concentration of silicon oxide particles is 5 during actual polishing.20% by weight or moreweight%Less thanIn this range, the concentration can be determined by the allowable polishing time depending on the type of object to be polished. In general, the higher the concentration of the abrasive, the higher the polishing rate, but the concentration of the abrasive and the amount of polishing are not proportional. Polishing at a low concentration for a long time requires less abrasive consumption. But 5weight%Less thanSo it takes a lot of time and it's not realistic,20% by weightmore thanTherefore, the effect of increasing the concentration is weakened, and the consumption of the abrasive becomes disadvantageous for the economy. 40weightIf the concentration is higher than%, the colloid adhering to the part other than the polishing part is easy to dry, and the dried silica powder isInCarrying it can cause scratches and cause defective products.
[0023]
  In the present invention, it is important that the polishing composition has a pH in the range of 9.7 to 10.7. When the pH is less than 9.7, the polishing rate is remarkably lowered and deviates from the practical range. On the other hand, when the pH is higher than 10.7, the aggregation of the silicon oxide particles starts, so that the stability of the polishing composition is lowered and this is also out of the practical range.
  In addition, this pH should not easily change due to possible changes in external conditions such as friction, heat, contact with outside air, or mixing with other components. The composition solution itself is a so-called buffering solution with a small range of pH change.thingIs a requirement.
[0024]
Examples of the ions that form the buffer solution of the present invention include anions such as strong acids such as hydrochloric acid, nitric acid, hydrofluoric acid, and sulfuric acid, and weak acids such as boric acid, carbonic acid, phosphoric acid, and water-soluble organic acids. Or a mixture thereof. Particularly preferred are carbonate ions or bicarbonate ions. Cations are alkaline ions such as sodium and potassium, ammonium ions such as ammonium, choline and tetramethylammonium, and amine ions such as ethylenediamine and piperazine, which show alkalinity. A mixture of In particular, potassium ions, tetramethylammonium ions, and mixtures thereof are preferable. The buffer solution described in the present invention is a solution formed by a combination of the above-mentioned ions, added as an acid, an alkali, and a salt, dissociated as ions, and coexisting in an undissociated state. It is characterized by little change in pH even when any acid or base is mixed.
[0025]
Furthermore, the composition of the present invention is 0.01 to 0.1 mol / kg-SiO, wherein fluorine ions or anions in which fluorine is coordinated to the components of the above composition are fluorine.₂Can be included. This polishing composition can further increase the polishing rate. Fluorine ions may be added as hydrofluoric acid, or may be added as fluorides of the above bases. As the anion coordinated with fluorine, tetrafluoroborate ion or hexafluorosilicate ion is preferable. These can be added to a concentrated stock solution of 15 to 65% by weight of silicon oxide, but may be added when the stock solution is diluted and adjusted each time it is used. 0.01 mol / kg-SiO with fluorine ions or anions coordinated with fluorine as fluorine₂In the following, a sufficient polishing rate cannot be obtained. 0.1 mol / kg-SiO₂Addition of the above does not provide a flat mirror surface because the erosion is too strong. Preferably 0.01-0.06 mol / kg-SiO₂It is.
[0026]
In the above polishing method, the quantitative supply liquid of the polishing composition may be discarded after being used once, but it is economically disadvantageous, and it is preferable to return to the supply liquid and use it in a circulating manner. That is, it is economical to circulate a fixed amount of the polishing composition and supply it to the polishing section of the polishing apparatus to polish a plurality of polishing objects.
[0027]
In order to improve the physical properties of the polishing composition of the present invention, additives such as surfactants, dispersants, anti-settling agents and polishing accelerators can be used in combination. Examples of the surfactant, dispersant, anti-settling agent, and polishing accelerator include water-soluble organic substances, inorganic layered compounds, and fluorine-based salts. Further, the polishing composition of the present invention is an aqueous solution, but an organic solvent may be added. The polishing composition of the present invention may be prepared by mixing colloidal silica, a base, an additive, and water during polishing. In general, a composition in which the concentration of silicon oxide particles is in the range of 25 to 65% by weight is prepared and diluted with water or a mixture of water and an organic solvent for use.
[0028]
  Next, the polishing composition of the present invention and the polishing method using the same will be specifically described with reference to examples and comparative examples, but the present invention is not particularly limited thereto.Examples 1 to 9 and Example 11 are reference examples.
  Polishing compositions used in Examples and Comparative Examples were prepared by the following method. Commercially available products were used for colloidal silica (concentration 40 wt%) having an average primary particle size of 40 nm and 80 nm. Each average primary particle diameter was calculated by measuring the specific surface area of silicon oxide by the nitrogen adsorption BET method, assuming that the silicon oxide particles were true spheres, and confirmed that the values were 40 nm and 80 nm. In addition, the TEM photograph confirmed that the maximum particle and the minimum particle were in the range of ± 20% of the average particle diameter, and the particle size distribution was extremely narrow.
[0029]
As components constituting the buffer solution, a commercially available 20% aqueous solution was used for tetramethylammonium hydroxide, and reagents were used for potassium hydrogen carbonate, sodium hydrogen carbonate, sodium carbonate, sodium hydroxide, and potassium fluoride.
The components constituting the buffer solution were previously dissolved in pure water, added to colloidal silica, and finally added with pure water to prepare a predetermined silicon oxide concentration, which was used as a working solution. The amount of the components constituting the buffer solution is the number of moles (mol / kg-SiO 2) added to 1 kg of silicon oxide in the polishing composition.₂). In addition, potassium fluoride was prepared by dissolving in pure water added last.
[0030]
【Example】
[Examples 1-2OhAnd Comparative Examples 1 to 3]
  Examples of surface polishing of optical white glass are described below. As the white plate glass, a commercially available product was used which had been subjected to edge-polishing with sandpaper in advance. A polishing test was performed using the abrasive composition having the contents shown in Table 1, and the results are shown in Table 1. The pH of the polishing composition was measured using a pH meter, and the polishing rate was determined from the weight difference of the white plate glass before and after polishing and converted to a change in thickness.
[0031]
The polishing conditions were mirror polishing by the following method.
<Polishing conditions>
Polishing device: Surface plate diameter 200mm, single-side polishing device
Surface plate rotation speed: 150 rpm
Polishing cloth: Suba 400 (Rodel)
Load: 223g / cm2
Polishing composition flow rate: 20 ml / min
Polishing time: 10 minutes
Workpiece: White plate glass
As is clear from the examples and comparative examples, it was found that the polishing rate was remarkably increased by adding a specific amount of large particles to small particles.
[0032]
[Table 1]

[0033]
[Examples 3 to 6 and Comparative Examples 4 to 7]
An example of surface polishing of soda glass is described below. As the blue plate glass, a material polished in advance with a ceria abrasive (COFSF 620, Speed Fam Co., Ltd.) was used. A polishing test was conducted using the abrasive composition having the contents shown in Table 2, and the results are shown in Table 2.
[0034]
The polishing conditions were mirror polishing by the following method.
<Polishing conditions>
Polishing equipment: Surface plate diameter 650mm, double-side polishing equipment
Lower surface plate rotation speed: 30rpm
Polishing cloth: Suba 400 (Rodel)
Load: 150 g / cm2
Polishing composition flow rate: 300 ml / min
Polishing time: 7 minutes
Workpiece: 2.5 inches, blue plate glass disk
[0035]
The pH of the polishing composition was measured using a pH meter. The polished surface was evaluated by observing the occurrence of haze with the naked eye under a condenser lamp. The polishing rate was calculated from the difference in weight of the soda glass discs before and after polishing and converted into a change in thickness.
[0036]
As apparent from Examples 3 to 6, it was found that the polishing rate was remarkably increased by adding a specific amount of large particles to small particles. In Comparative Example 4, only the small particles and in Comparative Examples 5-7, the mixing ratio of the large particles is increased, and the polishing rate is remarkably reduced.
[0037]
[Table 2]

[0038]
[Examples 4 to 6 and Comparative Examples 5 to 8]
Examples of surface polishing of crystallized glass disks are described below. As the crystallized glass disk, a material that had been polished in advance with a ceria abrasive (COFSF620, sold by Speed Fam Co., Ltd.) was used. A polishing test was conducted using the abrasive composition having the contents shown in Table 3, and the results are shown in Table 3.
[0039]
The polishing conditions were mirror polishing by the following method.
<Polishing conditions>
Polishing equipment: Surface plate diameter 650mm, double-side polishing equipment
Lower surface plate rotation speed: 30rpm
Polishing cloth: Suba 400 (Rodel)
Load: 150 g / cm2
Polishing composition flow rate: 300 ml / min
Polishing time: 7 minutes
Workpiece: 2.5 inch, crystallized glass disk
[0040]
The pH of the polishing composition was measured using a pH meter. The polished surface was evaluated by observing the occurrence of haze with the naked eye under a condenser lamp. The polishing rate was obtained from the difference in weight of the crystallized glass disk before and after polishing and converted into a change in thickness.
[0041]
As is clear from the comparison between Comparative Example 8 and Example 7, the polishing rate is remarkably increased by adding a small amount of large particles to small particles. Further, as is clear from Examples 7 to 9, the pH is also an important factor. The higher the value, the higher the polishing rate, but conversely, in order to always obtain the same polishing rate, it is necessary that the pH does not fluctuate. It turned out that. In Example 10 and Comparative Example 9, the effect of fluorine ions is clear. Fluorine ions promote polishing, but excessive amounts cause excessive erosion and cause haze. In Example 10, it was shown that polishing can be performed even at a low pH by increasing the concentration of silicon oxide particles. On the other hand, in Comparative Example 11, it was shown that when the concentration of silicon oxide particles was lowered, sufficient polishing could not be performed even if the additive was increased.
[0042]
[Table 3]

[0043]
The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and has the same function and effect regardless of the present embodiment. It is included in the technical scope of the invention.
[0044]
For example, in the above polishing step, glass polishing is exemplified, but the polishing agent of the present invention can also be used for polishing an image display flat panel and a silicon oxide film.
[0045]
【The invention's effect】
As shown in the above description, the polishing composition of the present invention has an average primary particle diameter of 40 to 60 nm and two distinct silicon oxide particles having a weight ratio of 60 to 100 nm in a weight ratio of 1: 0.05 to The colloidal solution is present in a ratio of 1: 0.3, and the concentration of silicon oxide particles with respect to the entire polishing composition is in the range of 5 to 40% by weight, and the colloidal solution has a pH of 9.7 to 10.7. The composition is prepared as a buffer solution in which a salt having a buffering action is dissolved, and this composition is based on the invention that when a specific amount of large particles are mixed with small particles, the polishing rate is remarkably increased. For example, when the surface of silica glass is polished using this, the polishing speed is high and the polishing surface condition is good, which greatly improves the conventional problems. Rukoto could be. Furthermore, the composition of the present invention is 0.01 to 0.1 mol / kg-SiO, wherein fluorine ions or anions in which fluorine is coordinated to the components of the above composition are fluorine.₂Inclusion of a higher polishing rate can be achieved.
[Brief description of the drawings]
FIG. 1 is a graph showing the polishing rate (nm / min) when a white glass surface (main surface) is polished using a polishing composition in which the weight ratio of large particles to small particles is changed.

Claims

A polishing composition for polishing a glass disk, a photomask, a silica insulating film on a semiconductor wafer, or a surface of a compound mainly composed of silicon oxide of optical glass, comprising two types of silicon oxide, small particles and large particles The small particles have an average primary particle diameter of 40 nm or more and 60 nm or less, the large particles have an average primary particle diameter of more than 60 nm and 100 nm or less, and the small particles and the large particles have a weight ratio of 1 The colloidal solution is present in a ratio of 0.05 to 1: 0.3, and the concentration of the silicon oxide particles with respect to the entire polishing composition is in the range of 5 wt% to less than 20 wt%. , it is prepared as a buffer solution of a salt having a buffering action between PH9.7～10.7, further, fluorine anions fluorine ions or fluorine coordinated Polishing composition characterized by containing 0.01~0.1mol / kg-SiO ₂ in.

And 60nm below the average primary particle diameter of 40 nm or more as a polishing composition, the two kinds of weight a colloidal solution of silicon oxide particles in the range below 100nm exceed 60 nm 1: 0.05~1: 0. The method for preparing a polishing composition according to claim 1, comprising a step of mixing at a ratio of 3.

The polishing composition is further diluted with water or an aqueous solution containing a salt, so that the concentration of silicon oxide particles in the polishing composition as a whole is in the range of 5 wt% to less than 20 wt%, and pH 9.7 to 10. 7. The method for preparing a polishing composition according to claim 2 , comprising a step of preparing a colloidal solution of No. 7.

A polishing method for polishing an object to be polished, the surface of which is composed of a compound mainly composed of silicon oxide, using the polishing composition according to claim 1 .

Placing the synthetic resin foam or object to be polished to a surface plate of polishing cloth was stretched consisting suede synthetic leather or the like consists of those compounds of silicon oxide as a main component, while the press rotating, according to claim 1 A polishing method comprising supplying a polishing composition to polish a main surface of an object to be polished.

Using a polishing apparatus having a polishing member with a polishing cloth affixed to the surface, the polishing member and / or the polishing object are brought into contact with the polishing member and an end surface of the polishing object made of a compound mainly composed of silicon oxide. A polishing method comprising polishing the object to be polished by supplying the polishing composition according to claim 1 to an end face portion while rotating.