JP2004327614A - Polishing solution for iii-v compound semiconductor wafer and method for polishing iii-v compound semiconductor wafer using the same - Google Patents
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、ＩＩＩ−Ｖ族化合物半導体ウェハ用の研磨液及びそれを用いたＩＩＩ−Ｖ族化合物半導体ウェハの研磨方法に関し、さらに詳しくは、鏡面研磨において、臭素系の研磨液を使用しないで、十分な加工速度で表面精度の優れた研磨を行うことができる研磨液、及びそれを用いたウェハの研磨方法に関する。
【０００２】
【従来の技術】
ＩＩＩ−Ｖ族化合物半導体ウェハは、発光素子、レーザ素子、受光素子、マイクロ波素子等の半導体デバイス製造に際して、エピタキシャル用の基板として用いられるものである。上記基板として用いられるウェハの製造では、先ず単結晶インゴットが育成され、次に、スライス作業で得られたウェハの粗研磨ついで鏡面研磨が行われる。その後、洗浄処理さらに乾燥処理を経てエピタキシャル用の基板となる。エピタキシャル工程では、液相成長法あるいは気相成長法で基板上に発光層が形成されるので、ウェハ表面の平坦度、表面粗さ、清浄度等の表面精度が重要である。
【０００３】
上記ウェハの鏡面研磨の方法としては、一般的に、回転する定盤に研磨パッドを貼付け、この表面に研磨液を滴下しながら接着板にワックスを用いて固定したウェハを所定の押圧（加工圧力）で圧接して、研磨パッドに対して自転を行わせる。滴下された研磨液は、ウェハと研磨パッドとの間に研磨液層を形成し、研磨液による化学的作用と研磨液の固形物と研磨パッドによる機械的作用によってウェハの鏡面研磨が行われる。ここで、ウェハの厚み方向への研磨の進行度合を、加工速度（μｍ／ｍｉｎ）であらわす。
【０００４】
従来、上記化合物半導体の一つであるＩｎＰウェハの鏡面研磨において、臭素とメタノールの混合液、臭素とグリセリンの混合液、またはこれにコロイダルシリカを混合した研磨液等の臭素を含んだ研磨液が一般的に用いられている（例えば、特許文献１、特許文献２参照）。これは、臭素がＩｎＰに対する溶解性が大きいために、臭素を含んだ研磨液を用いると加工速度が１．５μｍ／ｍｉｎ以上と大きく、かつ研磨後の表面粗さが小さく、またスクラッチも少ないなど表面精度が良いことによる。
しかしながら、ＩｎＰに使用される上記研磨液は、金属に対して強い腐食作用がある臭素を用いているので、研磨機やその周辺の装置を短期間で錆びさせてしまうので、量産規模での研磨加工には適さないという問題がある。また、臭素は揮発性が強いため、研磨加工の間に研磨液の臭素濃度及びｐＨ値が変化して、ポリッシュピットの発生など研磨後の表面の品質にばらつきが出やすいという問題があった。
【０００５】
この解決策として、臭素を用いない研磨液、例えばコロイダルシリカに過酸化水素及び有機酸を混合して得た研磨液、及びこれを用いた研磨方法（例えば、特許文献３参照）が提案されている。しかしながら、前記研磨液でＩｎＰの鏡面研磨加工を行った場合、加工速度が０．２μｍ／ｍｉｎ以下であり、生産性が低いという問題がある。このため、加工速度を上げるために、研磨装置の研磨の押圧（加工圧力）を大きくするとスクラッチが多発して表面粗さが悪化する。以上のように、ＩｎＰ用として工業的に効率的な研磨液が未だ得られていない。
このような状況から、ＩＩＩ−Ｖ族化合物半導体ウェハの鏡面研磨において、臭素系の研磨液を使用しないで、十分な加工速度で表面精度の優れた研磨を行うことができる研磨液が求められている。
【０００６】
【特許文献１】
特開平７−２３５５１９号公報（第１頁、第２頁）
【特許文献２】
特開２００２−２５９５４号公報（第１頁、第２頁）
【特許文献３】
特許第２５８５９６３号（第１〜７頁）
【０００７】
【発明が解決しようとする課題】
本発明の目的は、上記の従来技術の問題点に鑑み、ＩＩＩ−Ｖ族化合物半導体ウェハの鏡面研磨において、臭素系の研磨液を使用しないで、十分な加工速度で表面精度の優れた研磨を行うことができる研磨液及びこれを用いたウェハの研磨方法を提供することにある。
【０００８】
【課題を解決するための手段】
本発明者は、上記目的を達成するために、ＩＩＩ−Ｖ族化合物半導体ウェハ用の研磨液について、鋭意研究を重ねた結果、粗粒と細粒からなる２種類の粒子径のシリカに、特定の酸化剤、酸化助剤及び研削助剤を混合してなる研磨液を用いてＩＩＩ−Ｖ族化合物半導体ウェハを研磨したところ、十分な加工速度と優れた表面精度が得られることことを見出し、本発明を完成した。
【０００９】
すなわち、本発明の第１の発明によれば、水に、粗粒と細粒からなる２種類の粒子径のシリカ、ジクロロイソシアヌール酸ナトリウム、硫酸ナトリウム、トリポリリン酸ナトリウム、炭酸ナトリウム及びクエン酸を混合してなることを特徴とするＩＩＩ−Ｖ族化合物半導体ウェハ用の研磨液が提供される。
【００１０】
また、本発明の第２の発明によれば、第１の発明において、前記粗粒の粒子径が０．０５〜０．５μｍで、一方細粒の粒子径が０．０１〜０．０５μｍであることを特徴とするＩＩＩ−Ｖ族化合物半導体ウェハ用の研磨液が提供される。
【００１１】
また、本発明の第３の発明によれば、第１の発明において、前記研磨液のｐＨが７．０〜８．０あることを特徴とするＩＩＩ−Ｖ族化合物半導体ウェハ用の研磨液が提供される。
【００１２】
また、本発明の第４の発明によれば、第１〜３いずれかの発明において、前記ＩＩＩ−Ｖ族化合物半導体が、リン化インジウムであることを特徴とするＩＩＩ−Ｖ族化合物半導体ウェハ用の研磨液が提供される。
【００１３】
また、本発明の第５の発明によれば、請求項１〜４のいずれかの研磨液を用いることを特徴とするＩＩＩ−Ｖ族化合物半導体ウェハの研磨方法が提供される。
【００１４】
【発明の実施の形態】
以下、本発明のＩＩＩ−Ｖ族化合物半導体ウェハ用の研磨液及びこれを用いたＩＩＩ−Ｖ族化合物半導体ウェハの研磨方法を詳細に説明する。
【００１５】
１．ＩＩＩ−Ｖ族化合物半導体ウェハ
本発明において研磨対象とされるＩＩＩ−Ｖ族化合物半導体ウェハとしては、特に限定されるものではなく、リン化ガリウム（ＧａＰ）、リン化インジウム（ＩｎＰ）、ヒ化ガリウム（ＧａＡｓ）、ヒ化インジウム（ＩｎＡｓ）、アンチモン化インジウム（ＩｎＳｂ）等の単結晶から得られたものが用いられるが、鏡面研磨加工において、上記のように多くの課題があるリン化物半導体が好適であり、リン化インジウムが特に好適である。
【００１６】
２．研磨液
本発明に係る研磨液は、ＩＩＩ−Ｖ族化合物半導体ウェハの鏡面研磨加工に用いられるものであって、水に、必須成分として、粗粒と細粒からなる２種類の粒子径のシリカ、ジクロロイソシアヌール酸ナトリウム、硫酸ナトリウム、トリポリリン酸ナトリウム、炭酸ナトリウム及びクエン酸を混合することにより構成される。
【００１７】
本発明において、ウェハの鏡面研磨は、前記研磨液中の酸化剤であるジクロロイソシアヌール酸ナトリウムによってウェハ表面に酸化膜を形成し、その酸化膜をクエン酸で溶解する作用と、研削剤であるシリカ及び研磨パッドで研削する作用によって進行する。本発明では、さらに酸化助剤として硫酸ナトリウム及び炭酸ナトリウム、研削助剤としてトリポリリン酸ナトリウムを適切に混合して、研磨液を構成することが必須である。これによって、十分な加工速度と優れた表面精度が達成される。
【００１８】
本発明において、水への上記必須成分の混合は、特に限定されるものではなく、個々の必須成分を任意の順序で、しかもそれらのスラリー又は水溶液を用いて行うこともできる。本発明に用いる水の組成は、特に限定されるものではなく、研磨処理に影響を及ぼす不純物を含有しない水が用いられる。
【００１９】
本発明に用いるシリカは、粗粒と細粒を含むものである。本発明において、粗粒と細粒を含むシリカを用いることが重要である。これによって、ウェハの研磨において、十分な加工速度と小さな表面粗さを両立させることができる。すなわち、粒子径の大きな粗粒のみでは加工速度は速いが表面粗さが悪化し、一方、粒子径の小さい細粒のみでは加工速度が遅く、かつ研削量が少ないために表面粗さも小さくならない。そこで、本発明では、粗粒のシリカと細粒のシリカを混合して用いることで、加工速度を高く維持しつつ、表面粗さを小さくする。
【００２０】
上記シリカの粒子径は、特に限定されるものではないが、十分な加工速度と小さな表面粗さを両立させるために、粗粒の粒子径が０．０５〜０．５μｍ、かつ細粒の粒子径が０．０１〜０．０５μｍであるのが好ましい。
上記シリカの研磨液中の濃度、及び粗粒と細粒の混合割合は、特に限定されるものではないが、粗粒が０．５〜２．０重量％で、細粒が２．０〜２０．０重量％で混合するのが好ましい。すなわち、粗粒と細粒の研磨液中の濃度が上記範囲であるとき、加工速度を高く維持しつつ、表面粗さを小さくすることができる。
【００２１】
上記シリカの種類は、特に限定されるものではなく、さまざまな製法による種々の形状の粉末シリカ及び／又はコロイダルシリカが用いられるが、研磨液のｐＨを所定値に調整するのが容易な粉末シリカが好ましい。すなわち、シリカとしてアルカリ性のコロイダルシリカ溶液のみを用いると、ｐＨが高くなり、そのため加工速度が低下してしまう。そこで、コロイダルシリカを使用する場合には、粗粒の方をコロイダルシリカ、細粒の方を粉末シリカにして組合せて用いるのが望ましい。また、前記粒子形状としては、表面粗さを小さく、研削作用を強めるため、球状が好ましい。
【００２２】
本発明に用いるトリポリリン酸ナトリウムの研磨液中の濃度は、特に限定されるものではないが、０．５〜２．０重量％が好ましい。すなわち、トリポリリン酸ナトリウムの研磨液中の濃度が上記範囲であるとき、シリカの流動性を良くするための研削助剤として効果的に作用することができる。また、これ以上の添加は、研磨液のｐＨが高くなり、そのため加工速度が低下してしまう。
【００２３】
本発明に用いるジクロロイソシアヌール酸ナトリウムの研磨液中の濃度は、特に限定されるものではないが、７．０〜１０．０重量％が好ましい。前記濃度が、７．０重量％未満では、ウェハ表面に酸化膜を形成する効果が低く、一方１０．０重量％を超えても、加工速度の向上は小さく、また塩素臭への対応の強化が必要になる。ジクロロイソシアヌール酸ナトリウムは、有効塩素濃度が高く、水に溶けやすいので酸化剤として有効である。
【００２４】
本発明に用いる硫酸ナトリウムの研磨液中の濃度は、特に限定されるものではないが、１．０〜２．０重量％が好ましい。すなわち、硫酸ナトリウムの研磨液中の濃度が上記範囲であるとき、酸化助剤として酸化作用を向上させ、また表面粗さを１０ｎｍ以下にすることができる。また、２．０重量％を超えれば研磨液中に析出物が発生するので好ましくない。
【００２５】
本発明に用いる炭酸ナトリウムの研磨液中の濃度は、特に限定されるものではないが、０．１〜０．３重量％が好ましい。すなわち、炭酸ナトリウムの研磨液中の濃度が上記範囲であるとき、酸化助剤として酸化作用を向上させ、また表面粗さを１０ｎｍ以下にすることができる。また、０．３重量％を超えれば、研磨液のｐＨが高くなり加工速度が著しく低下するので好ましくない。
【００２６】
本発明に用いるクエン酸の研磨液中の濃度は、特に限定されるものではないが、１．０〜２．０重量％が好ましい。すなわち、クエン酸の研磨液中の濃度が上記範囲であるとき、酸化及び研削作用と相俟ってウェハ表面の酸化膜を溶解して、加工速度を大きく向上することができる。また、２．０重量％を超えれば、シリカの凝集が起り始め、その凝集物が研磨装置のタンクや液供給チューブに付着するなどの不具合が発生する。
【００２７】
本発明の研磨液のｐＨは、特に限定されるものではないが、７．０〜８．０が好ましい。すなわち、研磨液のｐＨが７．０未満では、溶解作用が強くなり加工速度が向上するかわりにポリッシュピットが発生しやすくなる。一方８．０を超えると加工速度が低下する。
【００２８】
以上のように、本発明の研磨液は、弱アルカリ性であるので、一般的に用いられている臭素とメタノールの混合液等のｐＨが３〜４の酸性の研磨液に比べて、溶解作用が弱い。したがって、加工速度はやや劣るが、ポリッシュピットなどの不良が発生しづらいので得られるウェハの品質が優れている。またウェハの裏面に研磨液が浸透しても、腐食によるダメージが小さいので、裏面にワックスを塗布しないワックスレス研磨を行う場合には、特に有効である。
【００２９】
なお、本発明の研磨液には、前記した必須成分に加えて、本発明の目的を逸脱しない範囲で、ウェハの鏡面研磨加工液に用いられることが知られている他の成分、例えば、ＣＨ３Ｏ（ＣＨ２ＣＨ２ＯＨ）、ＣＨ３Ｎ（ＣＨ２ＣＨ２ＯＨ）等の非イオン系界面活性剤、乳酸、酢酸等の有機酸、水酸化ナトリウム、水酸化カリウム等のアルカリ水溶液等を配合してもよい。
【００３０】
３．研磨方法
本発明のＩＩＩ−Ｖ族化合物半導体ウェハの研磨方法は、上記本発明の研磨剤を用いて行うのが特徴である。
使用する研磨液以外の研磨方法については、特に限定されるものではなく、一般的にＩＩＩ−Ｖ族化合物半導体ウェハの研磨加工に用いられる装置及び方法が適用できる。例えば、研磨定盤と回転プレートを有する研磨装置において、粗研磨されたウェハは回転プレートの底面にワックス等で固定され、また研磨パッドが研磨定盤上に固定される。回転プレートを回転させながら下降させて、ウェハに研磨パッドから所定の加工圧力が加えられるように押圧する。そして、研磨パッド上に研磨液が滴下される。
【００３１】
本発明の研磨方法において、上記研磨液を使用し、かつ軟質の不織布タイプの研磨パッドを用いることで、４０ｋＰａまでの加工圧力を加えてもスクラッチがなく、加工速度を０．６μｍ／ｍｉｎ以上で、かつ表面粗さＰｖ（Ｐｅａｋ ｔｏ ｖａｌｌｅｙ）を１０ｎｍ以下にすることができ、十分な加工速度と優れた表面精度が得られる。
【００３２】
【実施例】
以下に、本発明の実施例及び比較例によって、本発明をさらに詳細に説明するが、本発明は、これらの実施例によってなんら限定されるものではない。なお、実施例及び比較例で用いた研磨液、並びに加工速度、表面粗さ及びスクラッチの評価方法は、以下の通りである。
（１）研磨液
（研磨液Ａ）：本発明の研磨液
▲１▼ジクロロイソシアヌール酸ナトリウム：８．０重量％
▲２▼硫酸ナトリウム：１．０重量％
▲３▼炭酸ナトリウム：０．１重量％
▲４▼粉末シリカ（平均粒子径０．１０μｍ）：１．０重量％
▲５▼粉末シリカ（平均粒子径０．０４μｍ）：５．０重量％
▲６▼トリポリリン酸ナトリウム：１．０重量％
▲７▼クエン酸：１．０重量％
▲８▼純水：８２．９重量％
▲９▼ｐＨ：７．１
（研磨液Ｂ）：市販のＧａＡｓ用１次研磨液（インセックＦＰ、フジミコーポレーテッド社製）
（研磨液Ｃ）：コロイダルシリカ（粒子径０．０７μｍ）１０重量％水溶液
（２）加工速度の測定：最小目盛０．１μｍの電気マイクロメータを使用して研磨前後の厚さ変化を測定し、研磨時間から求めた。
（３）表面粗さＰｖの測定：光干渉式表面粗さ計（ＷＹＫＯ社製）を用いて行った。
（４）スクラッチの検査：１０万ルクス以上の高輝度照明を用いて目視で有無の確認を行った。
【００３３】
実施例１
卓上式研磨装置を使用した。３８０ｍｍ径の定盤に、不織布タイプの軟質クロス製の研磨パッドを貼付けた。研磨治具に粗研磨した１５ｍｍ角のＩｎＰ小片ウェハ６枚を貼り付け、加工圧力４０ｋＰａになるように研磨パッドに圧接した。
それから定盤を４０ｒｐｍで回転しながら、研磨液Ａを流量３０ｍｌ／ｍｉｎで流下させて、３０分間研磨した。その後、ＩｎＰ小片ウェハを研磨治具から取り外し、洗浄及び乾燥処理を行った。得られたウェハの加工速度及び表面粗さＰｖを測定し、またスクラッチの有無を検査した。結果を表１に示す。
【００３４】
比較例１
研磨液Ｂを用いた以外は、実施例１と同様に行った。得られたウェハの加工速度及び表面粗さＰｖを測定し、またスクラッチの有無を検査した。結果を表１に示す。
【００３５】
比較例２
研磨液Ｃを用いた以外は、実施例１と同様に行った。得られたウェハの加工速度及び表面粗さＰｖを測定し、またスクラッチの有無を検査した。結果を表１に示す。
【００３６】
【表１】
表１より、実施例１では、本発明の研磨液を使用して本発明の方法に従って行われたので、０．６μｍ／ｍｉｎ以上の十分な加工速度が得られ、同時に表面粗さＰｖが１０ｎｍ以下でスクラッチのない表面精度の優れた鏡面研磨ウェハが得られることが分かる。これに対して、比較例１又は２では、使用した研磨液がこれらの条件に合わないので、加工速度、表面粗さ及びスクラッチのいずれににおいても満足すべき結果が得られないことが分かる。
【００３８】
【発明の効果】
以上説明したように、本発明のＩＩＩ−Ｖ族化合物半導体ウェハ用の研磨液及びこれを用いた研磨方法は、ウェハの鏡面研磨において、臭素系の研磨液を使用しないで、十分な加工速度で表面精度の優れた研磨を行うことができるものであり、その工業的価値は極めて大きい。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polishing liquid for a group III-V compound semiconductor wafer and a method for polishing a group III-V compound semiconductor wafer using the same, and more specifically, in mirror polishing, without using a bromine-based polishing liquid. The present invention relates to a polishing liquid capable of performing polishing with excellent surface accuracy at a sufficient processing speed, and a method for polishing a wafer using the polishing liquid.
[0002]
[Prior art]
A group III-V compound semiconductor wafer is used as an epitaxial substrate when manufacturing semiconductor devices such as light emitting devices, laser devices, light receiving devices, and microwave devices. In the manufacture of the wafer used as the substrate, first, a single crystal ingot is grown, and then, the wafer obtained by the slicing operation is roughly polished and then mirror-polished. After that, the substrate is subjected to a cleaning process and a drying process to become an epitaxial substrate. In the epitaxial process, since a light emitting layer is formed on a substrate by a liquid phase growth method or a vapor phase growth method, surface accuracy such as flatness, surface roughness, and cleanliness of a wafer surface is important.
[0003]
As a method of mirror polishing the wafer, generally, a polishing pad is attached to a rotating surface plate, and a wafer fixed to an adhesive plate with wax while a polishing liquid is dropped on this surface is pressed at a predetermined pressure (processing pressure). ) To rotate the polishing pad. The dropped polishing liquid forms a polishing liquid layer between the wafer and the polishing pad, and the wafer is mirror-polished by a chemical action of the polishing liquid, a solid substance of the polishing liquid, and a mechanical action of the polishing pad. Here, the degree of progress of polishing in the thickness direction of the wafer is represented by a processing speed (μm / min).
[0004]
Conventionally, in the mirror polishing of an InP wafer, which is one of the above compound semiconductors, a polishing liquid containing bromine such as a mixed liquid of bromine and methanol, a mixed liquid of bromine and glycerin, or a polishing liquid mixed with colloidal silica is used. It is generally used (for example, see Patent Documents 1 and 2). This is because bromine has a high solubility in InP, so when a polishing liquid containing bromine is used, the processing speed is as high as 1.5 μm / min or more, the surface roughness after polishing is small, and scratches are small. Due to good surface accuracy.
However, since the polishing liquid used for InP uses bromine, which has a strong corrosive action on metal, the polishing machine and its peripheral devices are rusted in a short period of time. There is a problem that it is not suitable for processing. Further, since bromine has a high volatility, the bromine concentration and the pH value of the polishing liquid change during the polishing process, so that there is a problem that the quality of the surface after polishing such as generation of polishing pits tends to vary.
[0005]
As a solution to this problem, a polishing solution that does not use bromine, for example, a polishing solution obtained by mixing hydrogen peroxide and an organic acid with colloidal silica, and a polishing method using the same have been proposed (for example, see Patent Document 3). I have. However, when mirror polishing of InP is performed with the polishing liquid, the processing speed is 0.2 μm / min or less, and there is a problem that productivity is low. Therefore, if the polishing pressure (processing pressure) of the polishing apparatus is increased in order to increase the processing speed, scratches occur frequently and the surface roughness deteriorates. As described above, an industrially efficient polishing liquid for InP has not been obtained yet.
Under such circumstances, there has been a demand for a polishing liquid capable of performing polishing with excellent surface accuracy at a sufficient processing speed without using a bromine-based polishing liquid in mirror polishing of a III-V compound semiconductor wafer. I have.
[0006]
[Patent Document 1]
JP-A-7-235519 (pages 1 and 2)
[Patent Document 2]
JP-A-2002-25954 (pages 1 and 2)
[Patent Document 3]
Patent No. 2585963 (pages 1 to 7)
[0007]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, an object of the present invention is to provide a polishing method for polishing a group III-V compound semiconductor wafer, which does not use a bromine-based polishing liquid and has excellent surface accuracy at a sufficient processing speed without using a bromine-based polishing liquid. An object of the present invention is to provide a polishing liquid that can be performed and a method for polishing a wafer using the same.
[0008]
[Means for Solving the Problems]
The present inventor has conducted extensive studies on a polishing liquid for a III-V compound semiconductor wafer in order to achieve the above object, and as a result, the polishing liquid has been identified as two types of silica having coarse and fine particles. When the III-V compound semiconductor wafer was polished using a polishing liquid obtained by mixing an oxidizing agent, an oxidizing aid and a grinding aid, it was found that a sufficient processing speed and excellent surface accuracy were obtained. The present invention has been completed.
[0009]
That is, according to the first invention of the present invention, silica having two kinds of particle diameters consisting of coarse particles and fine particles, sodium dichloroisocyanurate, sodium sulfate, sodium tripolyphosphate, sodium carbonate and citric acid are added to water. A polishing liquid for a group III-V compound semiconductor wafer characterized by being mixed is provided.
[0010]
According to a second aspect of the present invention, in the first aspect, the coarse particles have a particle size of 0.05 to 0.5 μm, while the fine particles have a particle size of 0.01 to 0.05 μm. A polishing liquid for a group III-V compound semiconductor wafer is provided.
[0011]
According to a third aspect of the present invention, in the first aspect, the polishing liquid for a group III-V compound semiconductor wafer, wherein the polishing liquid has a pH of 7.0 to 8.0. Provided.
[0012]
Further, according to the fourth invention of the present invention, in any one of the first to third inventions, the III-V compound semiconductor is indium phosphide, wherein the III-V compound semiconductor is indium phosphide. Is provided.
[0013]
According to a fifth aspect of the present invention, there is provided a method for polishing a group III-V compound semiconductor wafer, comprising using the polishing liquid according to any one of the first to fourth aspects.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a polishing liquid for a III-V compound semiconductor wafer of the present invention and a method for polishing a III-V compound semiconductor wafer using the polishing liquid will be described in detail.
[0015]
1. III-V Compound Semiconductor Wafer The III-V compound semiconductor wafer to be polished in the present invention is not particularly limited, and may be gallium phosphide (GaP), indium phosphide (InP), gallium arsenide. (GaAs), indium arsenide (InAs), indium antimonide (InSb), or the like obtained from a single crystal is used, but a phosphide semiconductor having many problems as described above in mirror polishing is preferable. And indium phosphide is particularly preferred.
[0016]
2. Polishing liquid The polishing liquid according to the present invention is used for mirror polishing of III-V compound semiconductor wafers. Silica having two kinds of particle diameters, consisting of coarse particles and fine particles, as essential components in water , Sodium dichloroisocyanurate, sodium sulfate, sodium tripolyphosphate, sodium carbonate and citric acid.
[0017]
In the present invention, the mirror polishing of the wafer is an operation of forming an oxide film on the wafer surface by sodium dichloroisocyanurate, which is an oxidizing agent in the polishing liquid, dissolving the oxide film with citric acid, and a grinding agent. It proceeds by the action of grinding with silica and a polishing pad. In the present invention, it is essential to form a polishing liquid by appropriately mixing sodium sulfate and sodium carbonate as oxidation aids and sodium tripolyphosphate as grinding aids. This achieves a sufficient processing speed and excellent surface accuracy.
[0018]
In the present invention, the mixing of the above-mentioned essential components with water is not particularly limited, and individual essential components can be mixed in an arbitrary order and using a slurry or an aqueous solution thereof. The composition of the water used in the present invention is not particularly limited, and water containing no impurities affecting the polishing treatment is used.
[0019]
The silica used in the present invention contains coarse particles and fine particles. In the present invention, it is important to use silica containing coarse particles and fine particles. This makes it possible to achieve both a sufficient processing speed and a small surface roughness in polishing the wafer. That is, the processing speed is high but the surface roughness is deteriorated only with coarse particles having a large particle diameter, while the processing speed is low only with fine particles having a small particle diameter, and the surface roughness does not decrease because the grinding amount is small. Therefore, in the present invention, by using a mixture of coarse-grained silica and fine-grained silica, the surface roughness is reduced while maintaining a high processing speed.
[0020]
The particle size of the silica is not particularly limited, but in order to achieve both a sufficient processing speed and a small surface roughness, the coarse particles have a particle size of 0.05 to 0.5 μm, and fine particles. Preferably, the diameter is from 0.01 to 0.05 μm.
The concentration of the silica in the polishing liquid and the mixing ratio of the coarse particles and the fine particles are not particularly limited, but the coarse particles are 0.5 to 2.0% by weight and the fine particles are 2.0 to 2.0% by weight. It is preferred to mix at 20.0% by weight. That is, when the concentration of coarse particles and fine particles in the polishing liquid is within the above range, the surface roughness can be reduced while maintaining the processing speed high.
[0021]
The type of the silica is not particularly limited, and various shapes of powdered silica and / or colloidal silica obtained by various production methods are used. However, powdered silica which can easily adjust the pH of the polishing liquid to a predetermined value is used. Is preferred. That is, when only the alkaline colloidal silica solution is used as the silica, the pH becomes high, so that the processing speed decreases. Therefore, when using colloidal silica, it is desirable to use a combination of coarse particles as colloidal silica and fine particles as powdered silica. The shape of the particles is preferably spherical in order to reduce the surface roughness and enhance the grinding action.
[0022]
The concentration of the sodium tripolyphosphate used in the present invention in the polishing liquid is not particularly limited, but is preferably 0.5 to 2.0% by weight. That is, when the concentration of sodium tripolyphosphate in the polishing liquid is within the above range, it can effectively act as a grinding aid for improving the flowability of silica. Further, the addition of more than that increases the pH of the polishing liquid, and therefore reduces the processing speed.
[0023]
The concentration of sodium dichloroisocyanurate in the polishing liquid used in the present invention is not particularly limited, but is preferably 7.0 to 10.0% by weight. When the concentration is less than 7.0% by weight, the effect of forming an oxide film on the wafer surface is low. On the other hand, when the concentration exceeds 10.0% by weight, the improvement of the processing speed is small and the response to chlorine odor is strengthened. Is required. Sodium dichloroisocyanurate is effective as an oxidizing agent because it has a high effective chlorine concentration and is easily soluble in water.
[0024]
The concentration of the sodium sulfate used in the present invention in the polishing liquid is not particularly limited, but is preferably 1.0 to 2.0% by weight. That is, when the concentration of sodium sulfate in the polishing liquid is within the above range, the oxidizing action can be improved as an oxidation aid, and the surface roughness can be reduced to 10 nm or less. On the other hand, if it exceeds 2.0% by weight, precipitates are generated in the polishing liquid, which is not preferable.
[0025]
The concentration of the sodium carbonate used in the present invention in the polishing liquid is not particularly limited, but is preferably 0.1 to 0.3% by weight. That is, when the concentration of sodium carbonate in the polishing liquid is within the above range, the oxidizing action can be improved as an oxidation aid and the surface roughness can be reduced to 10 nm or less. On the other hand, if it exceeds 0.3% by weight, the pH of the polishing liquid is increased, and the processing speed is remarkably reduced.
[0026]
The concentration of the citric acid used in the present invention in the polishing liquid is not particularly limited, but is preferably 1.0 to 2.0% by weight. That is, when the concentration of citric acid in the polishing liquid is within the above range, the oxide film on the wafer surface is dissolved together with the oxidizing and grinding actions, and the processing speed can be greatly improved. On the other hand, if the content exceeds 2.0% by weight, agglomeration of silica starts to occur, and problems such as adhesion of the agglomerate to a tank or a liquid supply tube of the polishing apparatus occur.
[0027]
The pH of the polishing liquid of the present invention is not particularly limited, but is preferably 7.0 to 8.0. That is, when the pH of the polishing liquid is less than 7.0, the dissolving action becomes stronger and the processing speed is improved, but instead, polishing pits are easily generated. On the other hand, if it exceeds 8.0, the processing speed decreases.
[0028]
As described above, since the polishing liquid of the present invention is weakly alkaline, its dissolving effect is higher than that of a commonly used acidic polishing liquid having a pH of 3 to 4 such as a mixture of bromine and methanol. weak. Therefore, although the processing speed is slightly inferior, defects such as polished pits are unlikely to occur, so that the quality of the obtained wafer is excellent. Even if the polishing liquid penetrates into the back surface of the wafer, damage due to corrosion is small. Therefore, it is particularly effective when performing waxless polishing without applying wax to the back surface.
[0029]
The polishing liquid of the present invention contains, in addition to the essential components described above, other components known to be used in a mirror polishing liquid for wafers, such as CH, without departing from the object of the present invention. Non-ionic surfactants such as 3 O (CH 2 CH 2 OH) and CH 3 N (CH 2 CH 2 OH); organic acids such as lactic acid and acetic acid; and alkaline aqueous solutions such as sodium hydroxide and potassium hydroxide. You may mix.
[0030]
3. Polishing Method The method for polishing a group III-V compound semiconductor wafer of the present invention is characterized in that it is performed using the above-mentioned abrasive of the present invention.
The polishing method other than the polishing liquid to be used is not particularly limited, and an apparatus and a method generally used for polishing a III-V compound semiconductor wafer can be applied. For example, in a polishing apparatus having a polishing plate and a rotating plate, a roughly polished wafer is fixed to the bottom surface of the rotating plate with wax or the like, and a polishing pad is fixed on the polishing plate. The rotating plate is lowered while rotating, and pressed so that a predetermined processing pressure is applied to the wafer from the polishing pad. Then, the polishing liquid is dropped on the polishing pad.
[0031]
In the polishing method of the present invention, by using the above polishing liquid and using a soft nonwoven type polishing pad, there is no scratch even when a processing pressure of up to 40 kPa is applied, and the processing speed is 0.6 μm / min or more. In addition, the surface roughness Pv (Peak to valley) can be reduced to 10 nm or less, and a sufficient processing speed and excellent surface accuracy can be obtained.
[0032]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention. However, the present invention is not limited to these Examples. The polishing liquids used in the examples and comparative examples, and the evaluation methods of the processing speed, the surface roughness and the scratch are as follows.
(1) Polishing liquid (polishing liquid A): polishing liquid of the present invention {1} sodium dichloroisocyanurate: 8.0% by weight
(2) Sodium sulfate: 1.0% by weight
(3) Sodium carbonate: 0.1% by weight
(4) Powdered silica (average particle size 0.10 μm): 1.0% by weight
{Circle around (5)} Powdered silica (average particle diameter 0.04 μm): 5.0% by weight
(6) Sodium tripolyphosphate: 1.0% by weight
{Circle around (7)} Citric acid: 1.0% by weight
(8) Pure water: 82.9% by weight
(9) pH: 7.1
(Polishing liquid B): Commercially available primary polishing liquid for GaAs (Insec FP, manufactured by Fujimi Corporation)
(Polishing liquid C): Colloidal silica (particle size: 0.07 μm) 10% by weight aqueous solution (2) Measurement of processing speed: The thickness change before and after polishing was measured using an electric micrometer having a minimum scale of 0.1 μm. It was determined from the polishing time.
(3) Measurement of surface roughness Pv: Measurement was performed using a light interference type surface roughness meter (manufactured by WYKO).
(4) Scratch inspection: The presence or absence was visually checked using high-intensity illumination of 100,000 lux or more.
[0033]
Example 1
A table-top polishing machine was used. A polishing pad made of a non-woven fabric type soft cloth was stuck to a 380 mm diameter platen. Six 15 mm-square roughly polished InP wafers were attached to a polishing jig and pressed against a polishing pad so as to have a processing pressure of 40 kPa.
Then, the polishing liquid A was allowed to flow at a flow rate of 30 ml / min while rotating the platen at 40 rpm, and polishing was performed for 30 minutes. After that, the InP small-piece wafer was removed from the polishing jig, and washed and dried. The processing speed and surface roughness Pv of the obtained wafer were measured, and the presence or absence of scratches was inspected. Table 1 shows the results.
[0034]
Comparative Example 1
The same operation as in Example 1 was performed except that the polishing liquid B was used. The processing speed and surface roughness Pv of the obtained wafer were measured, and the presence or absence of scratches was inspected. Table 1 shows the results.
[0035]
Comparative Example 2
The procedure was performed in the same manner as in Example 1 except that the polishing liquid C was used. The processing speed and surface roughness Pv of the obtained wafer were measured, and the presence or absence of scratches was inspected. Table 1 shows the results.
[0036]
[Table 1]
According to Table 1, in Example 1, since the polishing was performed according to the method of the present invention using the polishing liquid of the present invention, a sufficient processing speed of 0.6 μm / min or more was obtained, and at the same time, the surface roughness Pv was 10 nm. It can be seen that a mirror-polished wafer having excellent surface accuracy without scratches can be obtained below. On the other hand, in Comparative Examples 1 and 2, since the used polishing liquid does not meet these conditions, it can be seen that satisfactory results cannot be obtained in any of the processing speed, the surface roughness and the scratch.
[0038]
【The invention's effect】
As described above, the polishing liquid for a III-V compound semiconductor wafer of the present invention and the polishing method using the same can be used at a sufficient processing speed without using a bromine-based polishing liquid in the mirror polishing of the wafer. Polishing with excellent surface accuracy can be performed, and its industrial value is extremely large.
Claims (5)
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| JP2015093932A (en) * | 2013-11-12 | 2015-05-18 | 花王株式会社 | Polishing liquid composition for hard and brittle material |
| JP2017048359A (en) * | 2015-08-31 | 2017-03-09 | 住友金属鉱山株式会社 | Polishing slurry for oxide single crystal substrate and method for producing the same |
| JP2021057093A (en) * | 2019-09-30 | 2021-04-08 | 株式会社フジミインコーポレーテッド | Composition for polishing |
| JP7368997B2 (en) | 2019-09-30 | 2023-10-25 | 株式会社フジミインコーポレーテッド | polishing composition |
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