JP4159304B2 - Polishing method - Google Patents
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【０００１】
【発明が属する技術分野】
本発明は、シリコンウエーハの表面が酸化物膜、窒化物膜、炭化物膜、金属膜で被覆されたウエーハのエッジ部分の研磨方法に関する。
【０００２】
【従来技術】
シリコン単結晶等半導体素材を原材料としたＩＣ、ＬＳＩあるいは超ＬＳＩ等の電子部品は、シリコンのインゴットを薄い円板状にスライスしたウエーハに、繊細な電気回路を書き込み分割した小片状の半導体素子チップを基に製造されるものである。インゴットからスライスされたアズカットウエーハは、ラッピング、エッチング、更にはポリッシングという工程を経て、少なくともその片面が鏡面に仕上られた鏡面ウエーハに加工されて行く。ウエーハは、その鏡面仕上げした表面にその後のデバイス工程にて、酸化物膜、窒化物膜、炭化物膜あるいは金属膜等の薄膜が形成され（半導体デバイス基板）、更に微細な電気回路が書き込まれて行くのであるが、半導体素子チップに分割されるまでウエーハは最初の円板状の形状を保ったまま加工されるのであり、各加工工程の間には洗浄、乾燥、搬送等の操作が入る。その間ウエーハの外周側面エッジの形状が切り立ったままでかつ未加工の粗な状態の面であると、そこが各工程中に装置や他物体と接触し微小破壊が起こり微細粒子が発生したり、その粗な状態の面の中に汚染粒子を巻き込み、その後の工程でそれが散逸して精密加工を施した面を汚染し、製品の歩留まりや品質に大きな影響を与えたりすることが多い。
【０００３】
これを防止するために、ウエーハ加工の初期の段階でエッジ部分の面取り（べべリング）を行ない更にその部分を鏡面仕上げ（エッジポリッシング）することが一般に行なわれている。また、前記酸化物膜、窒化物膜、炭化物膜あるいは金属膜等の薄膜は表面、エッジ部分ともに鏡面仕上げを施したウエーハにＣＶＤ等の手法により必要な薄膜を施与するのであるが、この薄膜はウエーハ表面のみならずエッジ部分も被覆することになる。このエッジ部分に薄膜が存在すると以降のデバイス工程での障害にもなりうるので、その時点で除去することが必要となる。通常、これらの酸化物膜、窒化物膜、炭化物膜あるいは金属膜等の薄膜は、シリコンベアウエーハに比較して硬質であり、難研磨性のものである。
【０００４】
従来から、シリコンウエーハのエッジ部分の研磨装置、研磨方法については、例えば以下に述べる方法が提案されている。即ち、特開平７−１５６０４９号公報では、ウエーハの回転手段と前記ウエーハの外周部に対応した曲率の弧状研磨部を持つ研磨バフからなり、前記ウエーハと研磨バフをお互い接近・押圧・離反させるシリンダ装置を備えたウエーハ外周部の研磨装置が提案されている。特開２０００−３１７７８８号公報では、回転可能な凹面形状の研磨面を有する研磨具に、あらかじめワーク保持具に保持されたシリコンウエーハあるいは半導体ウエーハなどの円板状のワークを接触させ、凹面形状の研磨面を有する研磨具を回転駆動するワーク外周の研磨方法と研磨装置が提案されている。特開平８−８５０５１号公報では、半導体シリコン基板の面取り部研磨に於いて、半導体シリコン基板とバフを回転させつつ、前記シリコン基板の周縁部をバフに押し付け、コロイダルシリカを含む研磨液を供給しつつ前記面取り部を鏡面研磨する方法が提案されている。先に出願人により出願した特願２０００−３３９３０５号では、回転する円盤状のワークに、弧状をした作業面を有する研磨部材を接触させる装置が提案されている。
【０００５】
上述の研磨装置あるいは研磨方法はいずれも、コロイダルシリカを含む研磨液を供給しつつ、研磨バフ、パッド等の研磨布（研磨部材）を貼付した研磨具あるいは円板状のワークの双方または、一方を高速回転させながら接触させ、前記面取り部の鏡面研磨を行なうものであり、特に研磨バフ、パッド等の研磨布を貼付した研磨具の形状および動きに特徴を持たせ、歩留まりよくかつ効率的エッジ研磨を行なおうとするものである。
【０００６】
近年の電子回路の高集積化に伴い、ウエーハに対して、より高い品質と歩留まりが要求されて来ている。即ち、エッジ部分の研磨においては研磨速度が速く、安定していること、研磨後のウエーハの洗浄工程に於いて洗浄性が良いことなどが具体的項目として求められている。しかしながら、現実的には、上述の研磨装置あるいは研磨方法を用いてもこの近年の急激な要求の高度化に対応し切れていない。特に、難研磨性の酸化物膜、窒化物膜、炭化物膜あるいは金属膜等の薄膜を被覆した半導体デバイス基板のエッジ部分を研磨する場合において顕著である。
【０００７】
【発明が解決しようとする課題】
そこで、本発明者等は、例えば特願２０００−３３９３０５号に記載されているような方式の装置で上述の問題点の解決について鋭意検討を行なった。特願２０００−３３９３０５号に記載の装置の特徴は、ウエーハエッジ部分と研磨布が線接触しながらウエーハのエッジ部分を鏡面研磨することにあり、線接触部分に研磨用組成物を供給しながら、ワークを回転させて、ワークの外周エッジを研磨する所にある。本発明者等は、ウエーハエッジ部分と研磨布を線接触させウエーハのエッジ部分を鏡面研磨する研磨工程において、特定の組成の研磨用組成物を用いることにより、高い研磨速度と優れた品質の面が得られることを見出し本発明を完成したものである。即ち、本発明の目的はウエーハの表面が酸化物膜、窒化物膜、炭化物膜、金属膜で被覆されたウエーハのエッジ部分の研磨において、円弧状の研磨具の内側に貼付された研磨布とウエーハエッジ部分を線接触させウエーハのエッジ部分を鏡面研磨するウエーハエッジ研磨装置において、ウエーハエッジ部分の研磨速度、研磨面品質の向上を目的としている。特に、従来難研磨性で研磨効率の悪い酸化物膜、窒化物膜、炭化物膜あるいは金属膜等の薄膜で被覆されたウエーハを高効率で研磨し、後の洗浄工程において洗浄性が良い研磨方法の提供にある。
【０００８】
【課題を解決するための手段】
上述の目的は、円弧状の研磨具の内側表面に研磨布を貼付した円弧状の作業面を有する研磨具に、平均粒子径が２０〜１２０ｎｍであるコロイダルシリカを研磨用組成物全体に対してシリカ濃度が３重量％〜 ２５重量％になるように含み、更に、該研磨用組成物中のフッ素濃度が、１０ｐｐｍ〜２０００ｐｐｍになるようにフッ素化合物を含み、かつ、該研磨用組成物のｐＨが８．７〜１０．５の範囲でｐＨが緩衝溶液状態にあり、また、該研磨用組成物の導電率が２０ミリＳ/ｍ〜５００ミリＳ/ｍの範囲にある研磨用組成物を供給しながら、研磨具作業面と、シリコンウエーハに比較して硬質の薄膜で被覆されたウエーハのエッジ部分を線接触させながらウエーハを回転させて、ウエーハの外周エッジを研磨する研磨方法により達成される。
【０００９】
【発明の実施の形態】
上述の円弧状をした作業面を有する研磨具とは、ウエーハの外周円周形状に相当する円弧状の内周形状を持つ研磨具をいい、ウエーハ外周は研磨具の内側表面に貼付された研磨布と円周線上で線接触するものである。この円弧状の研磨具はウエーハ外周の全部に接触するものでなくてもよい。
上述の研磨布は、合成樹脂発泡体、合成皮革、不織布、不織布の合成樹脂加工品のうち少なくとも一つであることが好ましい。上述の不織布の合成樹脂加工品が、ポリエステルを主成分とする不織布をウレタン樹脂及び／または、シリコーン樹脂で加工したシートであると研磨力の向上と安定性につながり本発明達成に好適である。
【００１０】
本発明にいう研磨用組成物とは、研磨用砥粒である微細なコロイド状酸化珪素微粒子（コロイダルシリカ）を分散した水系の分散液が一般的に使用され、必要に応じて例えば界面活性剤、安定剤、添加剤、増量剤等が添加される。本発明の場合鏡面を得ることをその目的としているので、加えられるコロイダルシリカの平均粒子径は２０ｎｍ〜１２０ｎｍ、望ましくは、３０ｎｍ〜８０ｎｍの範囲にあることが肝要である。これより細かいと十分な研磨量（研磨速度）を得ることができないのみならずウエーハの表面に付着したコロイダルシリカが落ちにくくその洗浄性が低下する。１２０ｎｍ以上となるとデバイスの配線の幅に近づき好ましくない。本発明では、ＢＥＴ法で測定されたコロイダルシリカの比表面積より、コロイダルシリカを真球を仮定して算出した粒子径を平均粒子径として使用した。
【００１１】
更に、コロイダルシリカの含有量は研磨用組成物全体に対してシリカ濃度が３重量％〜２５重量％であることが必要である。これより低いと十分な研磨速度を得ることはできず、またこれより高いと研磨速度は増大するが、ウエーハへの汚染が増大し洗浄性が低化する。特に、ウエーハのエッジ部分を研磨する場合、シリカ濃度が３重量％〜１０重量％であることが好ましい。表面に酸化物膜、窒化物膜、炭化物膜、金属膜を有するウエーハのエッジ部分を研磨する場合、研磨時のシリカ濃度は、１０重量％〜２５重量％であることが好ましい。
【００１２】
ウエーハのエッジ研磨加工の場合、研磨用砥粒による機械的作用と、研磨用組成物中に含まれるある特定の成分によるウエーハへの化学的作用、具体的には特定のｐＨでの化学作用が組み合わされて行われるものであるため、研磨加工対象であるウエーハの種類によりその添加物が変えられる。すなわち、ウエーハの種類によって最適ｐＨ範囲が異なってくる場合もある。本発明の場合、研磨用組成物のｐＨは８．７〜１０．５の範囲にあることが必要であり、好ましくは、ｐＨ９．３〜１０．５の範囲である。またそのｐＨを安定に維持するために緩衝成分を加え研磨用組成物液全体をｐＨの緩衝溶液状態にしておくことが肝要である。
【００１３】
ｐＨの緩衝溶液を形成するための添加剤については特に限定を受けるものではないが、陰イオンとしては、炭酸イオンと炭酸水素イオンの組み合わせが特に好ましい。陽イオンとしては、カリウムイオン及び／または、ナトリウムイオン及び／または、テトラメチルアンモニウム（ＴＭＡ）イオンが好ましく、カリウムイオン及び／または、テトラメチルアンモニウムイオンがより好ましい。
【００１４】
更に、本発明においては、研磨用組成物中のフッ素濃度が、１０ｐｐｍ〜２０００ｐｐｍ、好ましくは１００ｐｐｍ〜２０００ｐｐｍになるようフッ素化合物を添加することが必要である。それにより研磨速度を向上することができる。特に、シリコンウエーハが表面に酸化物膜、窒化物膜、炭化物膜、金属膜を有するウエーハの研磨を行なう場合その効果が顕著である。フッ素化合物の種類としては特に限定されないが、水溶性であることが必要である。フッ素化合物としては、フッ化アルカリ、もしくは、フッ素錯体の塩などが使用できる。具体的には、フッ化ナトリウム（ＮａＦ）、フッ化カリウム（ＫＦ）、フッ化テトラメチルアンモニウム（ＴＭＡＦ）、テトラフルオロホウ酸ナトリウム（ＮａＢＦ4）、ヘキサフルオロケイ酸ナトリウム（Ｎａ2ＳｉＦ6）などを使用することが好ましい。研磨剤中のフッ素の含有量が、フッ素として、１０ｐｐｍ以下では、十分な研磨速度は与えない。フッ素の含有量が増加すると研磨速度は増加するが、フッ素が過剰に存在すると、洗浄性は低下する。
【００１５】
更に本発明において導電率とは液中の電気の通り易さを示す数値であり、単位長さあたりの電気抵抗値の逆数（Ｓｉｅｍｅｎｓ/ｍ）値である。本発明においては、研磨用組成物の導電率を２０ミリＳ／ｍ〜５００ミリＳ／ｍの間におくことにより研磨性能を顕著に向上することができる。導電率が２０ミリＳ／ｍ以下であると、研磨速度は低下する。導電率が５００ミリＳ／ｍ以上となると表面への汚染が増大し洗浄性が低下する。
【００１６】
以下実施例および比較例を挙げて本発明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、実施例および比較例にあげる実験例において、エッジ部分の研磨は以下の条件で鏡面研磨を実施した。
研磨装置：スピードファム株式会社製 特願２０００−３３９３０５に記載の装置
ウエーハ回転速度：２０００ｒｐｍ
研磨時間：１分間
研磨用組成物流量：２０００ｍｌ／分
荷重：４．０Ｋｇ／（１ユニットの研磨具）
研磨布： Ｓｕｂａ６００（ロデールニッタ社製）及び、ＤＲＰ−II（スピードファム社製）
研磨剤：表１及び表２記載の研磨用組成物を使用した。なお、研磨布として用いた、Ｓｕｂａ６００は、ポリエステルを主成分とする不織布をウレタン樹脂にて加工したシートである。ＤＲＰ−IIは、ポリエステルを主成分とする不織布をウレタン樹脂にて加工したシートと、圧縮弾性率が３５０Ｋｇｆ／ｃｍ2、厚み１mmの弾性体シートを組み合わせた多層構造シートである。
【００１７】
実施例および比較例にあげる実験例において、研磨用試料として用いたものは以下の通りである。
Ａ：８インチ、酸化膜８００ｎｍ＋ポリシリコン膜２０００ｎｍ付ウエーハ
Ｂ：８インチ、窒化チタン膜１００ｎｍ付ウエーハ
Ｃ：８インチ、チタン膜１５０ｎｍ付ウエーハ
Ｄ：８インチ、炭化ケイ素膜１００ｎｍ付ウエーハ
【００１８】
研磨用組成物の物性、研磨速度の測定および、加工後のワークの表面状態の評価は以下の方法で行なった。
研磨用組成物のｐＨ：ｐＨメーターを用い測定した。
研磨用組成物の導電率：導電率セルを使用して測定した。
研磨速度：研磨前後のウエーハの重量差より求めた。
研磨面（端面）の評価：光学顕微鏡にてヘイズ及びピットの状態を観察した。
平面状態の評価：スクラブ洗浄後、集光灯下、肉眼観察にて評価した。
【００１９】
【実施例及び比較例】
実施例１−２０
実施例１−２０の研磨用組成物は表２に示す処方にて調製した。研磨用組成物に添加したｐＨの緩衝溶液は、表１に示される４種類の構成の組成を用い、各実施例に示される導電率になるよう添加した。フッ素は、各実施例に示されるフッ素化合物を各実施例に示すフッ素量になるよう添加した。結果をまとめて表２に示す。
【００２０】
【表１】
【表２】
比較例１−２２
比較例１−２２の研磨用組成物は表３に示す処方にて調製した。研磨用組成物に添加した緩衝溶液は、表１に示される４種類の構成の組成を用い、各実施例に示される導電率になるよう添加した。フッ素は、各実施例に示されるフッ素化合物を各実施例に示すフッ素量になるよう添加した。結果をまとめて表３に示す。
【００２３】
【表３】
【００２４】
特許請求の範囲内の研磨方法にて実施された実施例１〜２０では、８ｍｇ／分以上の研磨速度および、鏡面状態にある端面が得られ、平面部分の洗浄性も全て良好であった。これに対しコロイダルシリカの平均粒子径が１８ｎｍと特許請求の範囲以下にある比較例１及び２ではスクラブ洗浄を行ってもウエーハの平面に付着したコロイダルシリカがシミ状に存在した。また、シリカ濃度が３ｗｔ％以下と特許請求の範囲以下にある比較例３及び４では、研磨速度が著しく低下し、端面に研磨不充分によるスレ残りが発生した。更に、シリカ濃度が３０ｗｔ％以上と特許請求の範囲以上にある比較例５及び６では、スクラブ洗浄を行ってもウエーハの平面に付着したコロイダルシリカがシミ状に存在した。
【００２５】
ｐＨが８．５と特許請求の範囲より低い比較例７及び８では、研磨速度が低下し、端面に研磨不充分によるスレ残りが発生した。また、ｐＨが１０．８と特許請求の範囲より高い比較例９及び１０では、スクラブ洗浄を行ってもウエーハの平面に付着したコロイダルシリカがシミ状に存在した。緩衝溶液を加えていない比較例１１及び１２では、研磨速度が低下し、端面に研磨不充分によるスレ残りが発生した。
更に導電率が５００ミリＳ／ｍ以上と特許請求の範囲以上にある比較例１３及び１４では、スクラブ洗浄を行ってもウエーハの平面に付着したコロイダルシリカがわずかながらシミ状に存在した。一方、導電率が２０ミリＳ／ｍ以下では比較例１５及び１６で示したように、酸化膜＋ポリシリコン膜付きウエーハの場合、端面に研磨不充分によるスレ残りが発生した。
【００２６】
比較例１７〜２２に示すように、表面に機能性膜を被覆したウエーハでは、フッ素化合物が存在しないと、端面に研磨不充分によるスレ残りが発生した。
【００２７】
【発明の効果】
以上述べた通り、本発明になる方法によれば、シリコンウエーハの表面が酸化物膜、窒化物膜、炭化物膜、金属膜で被覆されたウエーハのエッジ部分の研磨において、円弧状の研磨具の内側表面に貼付された研磨布とウエーハエッジ部分を線接触させウエーハのエッジ部分を鏡面研磨するウエーハエッジ研磨装置において、研磨装置自体の構造を全く変えることなく、研磨用組成物の組成に改良を加えた方法を用いることにより、ウエーハエッジ部分を研磨速度、研磨面品質の向上及び歩留まり等、効率の向上が可能となった。特に、従来難研磨性で研磨効率の悪い酸化物膜、窒化物膜、炭化物膜あるいは金属膜等の薄膜で被覆されたウエーハの高効率研磨及び後の洗浄工程における洗浄性を向上させることが可能となった。[0001]
[Technical field to which the invention belongs]
The present invention is a surface oxide film of the silicon Parkway Ha, nitride film, a carbide film, a polishing method of the edge portion of the coated window er wafer with a metal film.
[0002]
[Prior art]
Silicon single crystal such as an IC in which the semiconductor material as a raw material, LSI or electronic parts ultra LSI or the like, the wafer sliced from an ingot of silicon on to a thin disc-shaped, small piece-shaped semiconductor to which writing dividing the delicate electrical circuit It is manufactured based on the element chip. The as-cut wafer sliced from the ingot is processed into a mirror-finished wafer having at least one surface finished as a mirror surface through processes such as lapping, etching, and polishing. Wafer at the subsequent device step on the surface was the mirror finish, oxide film, nitride film, carbide film or thin metal film or the like is formed (semiconductor device board), finer electric circuit is written However, the wafer is processed while maintaining the original disk shape until it is divided into semiconductor element chips, and operations such as cleaning, drying, and conveyance are performed between each processing step. . Meanwhile, if the shape of the outer peripheral side edge of the wafer remains sharp and is an unprocessed rough surface, it will come into contact with equipment and other objects during each process, causing microdestruction and generating fine particles, In many cases, contaminated particles are entrained in a rough surface, which dissipates in the subsequent process, contaminates the surface that has been subjected to precision processing, and greatly affects the yield and quality of the product.
[0003]
In order to prevent this, chamfering (beveling) of an edge portion is generally performed at an initial stage of wafer processing, and then that portion is mirror-finished (edge polishing). In addition, the thin film such as the oxide film, nitride film, carbide film or metal film is formed by applying a necessary thin film by a method such as CVD to a wafer having a mirror-finished surface and edge portion. Covers the edge as well as the wafer surface. If a thin film is present at this edge portion, it may become an obstacle in the subsequent device process, and therefore it is necessary to remove it at that time. Usually, these oxide films, nitride films, carbide films, metal films and other thin films are harder and harder to polish than silicon bare wafers.
[0004]
Conventionally, a polishing apparatus of the edge portion of the silicon Parkway Ha, for the polishing method, a method described below, for example has been proposed. That is, in JP-A-7-156049, a cylinder comprising a polishing buff having a wafer rotating means and an arc-shaped polishing portion having a curvature corresponding to the outer peripheral portion of the wafer, the wafer and the polishing buff approaching, pressing and separating from each other. A polishing apparatus for a wafer outer peripheral portion provided with the apparatus has been proposed. In Japanese Patent Laid-Open No. 2000-317788, a disk-shaped workpiece such as a silicon wafer or a semiconductor wafer held in advance by a workpiece holding tool is brought into contact with a polishing tool having a rotatable concave polishing surface to thereby form a concave shape. There has been proposed a polishing method and a polishing apparatus for the outer periphery of a work that rotationally drives a polishing tool having a polishing surface. In JP-A 8-85051 discloses, in the chamfered portion polishing of the semiconductor silicon substrate, while rotating the semiconductor silicon substrate and buff, a peripheral portion of the silicon substrate pressed against the buff, supplying a polishing liquid containing colloidal silica However, a method for mirror polishing the chamfered portion has been proposed. In Japanese Patent Application No. 2000-339305 previously filed by the applicant, there has been proposed an apparatus for bringing a polishing member having an arc-shaped work surface into contact with a rotating disk-shaped workpiece.
[0005]
In either of the above polishing apparatuses or polishing methods, either or both of a polishing tool and a disk-shaped workpiece to which a polishing cloth (polishing member) such as a polishing buff and a pad is attached while supplying a polishing liquid containing colloidal silica The chamfered part is mirror-polished while rotating at a high speed, and the edge is characterized by the shape and movement of a polishing tool to which a polishing cloth such as a polishing buff or pad is applied, and the yield is high and efficient. It is intended to polish.
[0006]
Along with high integration of recent electronic circuits, for the U er Ha, it is coming higher quality and yield are required. That is, in polishing the edge portion, it is required as specific items that the polishing rate is fast and stable, and that the cleaning performance is good in the wafer cleaning process after polishing. However, in reality, even if the above-described polishing apparatus or polishing method is used, it has not been able to cope with the recent rapid increase in demand. This is particularly noticeable in the case of polishing an edge portion of a semiconductor device substrate coated with a thin film such as a hard-polishing oxide film, nitride film, carbide film or metal film.
[0007]
[Problems to be solved by the invention]
Therefore, the present inventors have conducted intensive studies on the solution of the above-described problems using an apparatus of the type described in, for example, Japanese Patent Application No. 2000-339305. The feature of the apparatus described in Japanese Patent Application No. 2000-339305 is that the edge portion of the wafer is mirror-polished while the wafer edge portion and the polishing cloth are in line contact, and while supplying the polishing composition to the line contact portion, The work is rotated to polish the outer peripheral edge of the work. In the polishing process in which the wafer edge portion and the polishing cloth are brought into line contact and the edge portion of the wafer is mirror-polished, the present inventors use a polishing composition having a specific composition to achieve high polishing speed and excellent quality. And the present invention has been completed. That is, the polishing object of the present invention the surface of Parkway Ha oxide film, nitride film, carbide film, the polishing of the edge portion of the Parkway Ha coated with a metal film, which is attached to the inside of the arc-shaped grinding tool An object of the present invention is to improve the polishing speed and the quality of a polished surface of a wafer edge portion in a wafer edge polishing apparatus for mirror-polishing a wafer edge portion by bringing a cloth and a wafer edge portion into line contact. In particular, the conventional flame abrasive polishing inefficient oxide film, a nitride film, a film coated with a wafer such as a carbide film or a metal film is Migaku Ken with high efficiency, cleanability in the cleaning process after a good polishing In providing a method.
[0008]
[Means for Solving the Problems]
The above-mentioned purpose is to apply colloidal silica having an average particle diameter of 20 to 120 nm to the polishing composition as a whole on a polishing tool having an arc-shaped work surface in which an abrasive cloth is attached to the inner surface of the arc-shaped polishing tool. The silica concentration is 3 wt% to 25 wt%, and the fluorine concentration in the polishing composition is 10 ppm to 2000 ppm, and the polishing composition has a pH. A polishing composition in which the pH is in a buffer solution state in the range of 8.7 to 10.5, and the conductivity of the polishing composition is in the range of 20 mS / m to 500 mS / m. This is achieved by a polishing method in which the outer peripheral edge of the wafer is polished by rotating the wafer while making a line contact between the work surface of the polishing tool and the edge portion of the wafer coated with a hard thin film compared to a silicon wafer. Ru
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The polishing tool having a work surface in which the above-mentioned arc-shaped, refers to a polishing tool having an arcuate inner circumferential shape corresponding to the outer peripheral circumference shape of the U er wafer, the wafer periphery is attached to the inside surface of the polishing tool In line contact with the polishing cloth on the circumference line. The arcuate polishing tool may not contact the entire outer periphery of the wafer .
The abrasive cloth is preferably at least one of synthetic resin foam, synthetic leather, non-woven fabric, and non-woven synthetic resin processed product. If the above-mentioned synthetic resin processed product of a nonwoven fabric is a sheet obtained by processing a nonwoven fabric mainly composed of polyester with a urethane resin and / or a silicone resin, the polishing power is improved and stability is suitable for achieving the present invention.
[0010]
As the polishing composition referred to in the present invention, an aqueous dispersion in which fine colloidal silicon oxide fine particles (colloidal silica) which are polishing abrasive grains are dispersed is generally used. Stabilizers, additives, extenders, etc. are added. In the case of the present invention, the purpose is to obtain a mirror surface, so it is important that the colloidal silica to be added has an average particle diameter of 20 nm to 120 nm, preferably 30 nm to 80 nm. If it is finer than this, not only a sufficient polishing amount (polishing rate) cannot be obtained, but also the colloidal silica adhering to the surface of the wafer is difficult to be removed, and its detergency is lowered. If it is 120 nm or more, it approaches the width of the device wiring, which is not preferable. In the present invention, the particle diameter calculated by assuming that the colloidal silica is a true sphere from the specific surface area of the colloidal silica measured by the BET method was used as the average particle diameter.
[0011]
Furthermore, the content of colloidal silica is required to have a silica concentration of 3 to 25% by weight with respect to the entire polishing composition. If it is lower than this, it is not possible to obtain a sufficient polishing rate, and if it is higher than this, the polishing rate will increase, but the contamination to the wafer will increase and the cleaning property will decrease. In particular, when polishing the edge portion of the wafer, the silica concentration is preferably 3% by weight to 10% by weight. Oxide film on the surface, a nitride film, a carbide film, to polish the edge portion of the Parkway Ha having a metal film, the silica concentration during polishing is preferably 10 wt% to 25 wt%.
[0012]
For the edge grinding of c er c, and mechanical action by the polishing abrasive, chemical action to that due to a specific component contained in the polishing composition wafers, in particular pH specifically for those that chemistry is performed in combination, the addition thereof is changed depending on the type of polishing target der Ru wafer. That is , the optimum pH range may vary depending on the type of wafer . In the case of the present invention, the polishing composition needs to have a pH in the range of 8.7 to 10.5, and preferably in the range of pH 9.3 to 10.5. In order to maintain the pH stably, it is important to add a buffer component and keep the entire polishing composition liquid in a pH buffer solution state.
[0013]
The additive for forming the pH buffer solution is not particularly limited, but the anion is particularly preferably a combination of carbonate ion and bicarbonate ion. As the cation, potassium ion and / or sodium ion and / or tetramethylammonium (TMA) ion are preferable, and potassium ion and / or tetramethylammonium ion are more preferable.
[0014]
Furthermore, in the present invention, it is necessary to add a fluorine compound so that the fluorine concentration in the polishing composition is 10 ppm to 2000 ppm, preferably 100 ppm to 2000 ppm. Thereby, the polishing rate can be improved. In particular, a silicon wafer is oxide film on the surface, a nitride film, a carbide film, its effect when performing polishing roux Eha that having a metal film is remarkable. Although it does not specifically limit as a kind of fluorine compound, It is required that it is water-soluble. As the fluorine compound, an alkali fluoride, a salt of a fluorine complex, or the like can be used. Specifically, sodium fluoride (NaF), potassium fluoride (KF), tetramethylammonium fluoride (TMAF), sodium tetrafluoroborate (NaBF 4 ), sodium hexafluorosilicate (Na 2 SiF 6 ), etc. Is preferably used. When the fluorine content in the abrasive is 10 ppm or less as fluorine, a sufficient polishing rate is not provided. When the fluorine content is increased, the polishing rate is increased. However, when fluorine is excessively present, the cleaning property is lowered.
[0015]
Furthermore, in the present invention, the conductivity is a numerical value indicating the ease of passing electricity in the liquid, and is a reciprocal (Siemens / m) value of the electrical resistance value per unit length. In the present invention, the polishing performance can be remarkably improved by placing the conductivity of the polishing composition between 20 mS / m and 500 mS / m. When the electrical conductivity is 20 mS / m or less, the polishing rate decreases. When the electrical conductivity is 500 mS / m or more, the contamination on the surface is increased and the cleaning property is lowered .
[0016]
Hereinafter, the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not particularly limited thereto. In the experimental examples given as examples and comparative examples, the edge portion was polished by mirror polishing under the following conditions.
Polishing apparatus: Speed wafer manufactured by Speed Fam Co., Ltd. The apparatus wafer rotation speed described in Japanese Patent Application 2000-339305: 2000 rpm
Polishing time: 1 minute Polishing composition flow rate: 2000 ml / min Load: 4.0 kg / (1 unit of polishing tool)
Polishing cloth: Suba600 (Rodel Nitta) and DRP-II (Speed Fam)
Polishing agent: The polishing composition described in Tables 1 and 2 was used. In addition, Suba600 used as the polishing cloth is a sheet obtained by processing a nonwoven fabric mainly composed of polyester with a urethane resin. DRP-II is a multilayer structure sheet in which a non-woven fabric mainly composed of polyester is processed with a urethane resin and an elastic sheet having a compression elastic modulus of 350 kgf / cm 2 and a thickness of 1 mm.
[0017]
In the experimental examples given in the examples and comparative examples, those used as polishing samples are as follows.
A: 8 inches oxide film 800 nm + polysilicon film 2000nm Tsukeu Eha B: 8 inches, a titanium nitride film 100nm Tsukeu Eha C: 8 inches, a titanium film 150nm Tsukeu Eha D: 8-inch silicon carbide film 100nm Tsukeu Agent C 【0018】
The physical properties of the polishing composition, the measurement of the polishing rate, and the evaluation of the surface state of the workpiece after processing were performed by the following methods.
The pH of the polishing composition was measured using a pH meter.
Conductivity of polishing composition: measured using a conductivity cell.
Polishing rate: It was determined from the weight difference between the wafers before and after polishing.
Evaluation of polished surface (end surface): The state of haze and pits was observed with an optical microscope.
Evaluation of the planar state: After scrub cleaning, it was evaluated by visual observation under a condenser lamp.
[0019]
[Examples and Comparative Examples]
Example 1-2 0
Polishing compositions of Examples 1-2 0 were prepared in formulations shown in Table 2. The buffer solution of pH added to the polishing composition was prepared so as to have the electrical conductivity shown in each example using the compositions of four types shown in Table 1. Fluorine was added to the fluorine compound shown in each example so that the amount of fluorine shown in each example was reached. The results are summarized in Table 2.
[0020]
[Table 1]
[Table 2]
Comparative Example 1-22
The polishing composition of Comparative Example 1-22 was prepared according to the formulation shown in Table 3. As the buffer solution added to the polishing composition, the compositions having four kinds of structures shown in Table 1 were used so that the conductivity shown in each example was obtained. Fluorine was added to the fluorine compound shown in each example so that the amount of fluorine shown in each example was reached. The results are summarized in Table 3.
[0023]
[Table 3]
[0024]
In Examples 1-2 0 which is performed by the polishing method within the scope of the claims, 8 mg / min or more polishing rate and an end surface in the mirror state is obtained, he was all also cleaning of the planar portion good . On the other hand, in Comparative Examples 1 and 2 in which the average particle diameter of colloidal silica was 18 nm or less, the colloidal silica adhering to the plane of the wafer was present in a spot shape even after scrub cleaning. Further, in Comparative Examples 3 and 4 having a silica concentration of 3 wt% or less and below the claims, the polishing rate was remarkably reduced, and a thread residue due to insufficient polishing occurred on the end face. Further, in Comparative Examples 5 and 6 in which the silica concentration is 30 wt% or more and more than the claims, colloidal silica adhering to the plane of the wafer existed in a spot shape even after scrub cleaning.
[0025]
In Comparative Examples 7 and 8 having a pH of 8.5, which is lower than the claimed range, the polishing rate was lowered, and a thread residue due to insufficient polishing occurred on the end face. Further, in Comparative Examples 9 and 10 having a pH of 10.8, which is higher than the scope of claims, the colloidal silica adhering to the plane of the wafer existed in a spot shape even after scrub cleaning. In Comparative Examples 11 and 12 in which no buffer solution was added, the polishing rate decreased, and a thread residue due to insufficient polishing occurred on the end face.
Further, in Comparative Examples 13 and 14 having an electrical conductivity of 500 milliS / m or more, which is more than the scope of claims, a slight amount of colloidal silica adhering to the plane of the wafer was present even when scrubbing was performed. On the other hand, when the conductivity was 20 milliS / m or less, as shown in Comparative Examples 15 and 16, in the case of a wafer with an oxide film and a polysilicon film, a thread residue due to insufficient polishing occurred on the end face.
[0026]
As shown in Comparative Examples 17 to 22, in the wafer with the functional film coated on the surface, if there was no fluorine compound, a thread residue due to insufficient polishing occurred on the end face.
[0027]
【The invention's effect】
As described above, according to the method according to the present invention, the surface oxide film of the silicon Parkway Ha, nitride film, carbide film, the polishing of the edge portion of the coated window er wafer with a metal film, arcuate in roux Ehaejji polishing apparatus to mirror polishing an edge portion of the attached abrasive cloth and the wafer edge portion to the inner surface of the polishing tool is line contact wafer, completely without changing the structure of the polishing apparatus itself, the polishing composition By using a method in which the composition has been improved, it has become possible to improve the efficiency of the wafer edge portion, such as the polishing rate, the quality of the polished surface and the yield. In particular, high-efficiency polishing of wafers coated with a thin film such as an oxide film, nitride film, carbide film, or metal film, which has been difficult to polish and has poor polishing efficiency, can be improved in the subsequent cleaning process. It became.
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002093729A JP4159304B2 (en) | 2002-03-29 | 2002-03-29 | Polishing method |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002093729A JP4159304B2 (en) | 2002-03-29 | 2002-03-29 | Polishing method |
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| JP2006104354A (en) * | 2004-10-06 | 2006-04-20 | Nippon Chem Ind Co Ltd | Polishing composition, method for producing the same and polishing method using the polishing composition |
| US8815110B2 (en) * | 2009-09-16 | 2014-08-26 | Cabot Microelectronics Corporation | Composition and method for polishing bulk silicon |
| CN109427573B (en) * | 2017-08-31 | 2022-11-04 | 胜高股份有限公司 | Method for grinding wafer |
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