JP2007013070A - Polishing composition for polishing device wafer edge, its manufacturing method and polishing work method - Google Patents
Polishing composition for polishing device wafer edge, its manufacturing method and polishing work method Download PDFInfo
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本発明は、表面に金属膜、酸化物膜、窒化物膜等（以下、金属膜等と記載する）が形成されたデバイスウエハのエッジ部分の研磨加工を行なうウエハエッジ研磨用研磨組成物及びその製造方法に関する。更に本発明は前記ウエハエッジ研磨用研磨組成物を使用してデバイスウエハのエッジ部分の鏡面加工を行なう方法に係る。 The present invention relates to a polishing composition for polishing a wafer edge, which polishes an edge portion of a device wafer having a metal film, oxide film, nitride film or the like (hereinafter referred to as a metal film or the like) formed on the surface, and a production thereof. Regarding the method. Furthermore, the present invention relates to a method for performing mirror processing of an edge portion of a device wafer using the polishing composition for polishing a wafer edge.
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、シリコンあるいはその他の化合物半導体の単結晶のインゴットを薄い円板状にスライスしたウエハに多数の微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ウエハは、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、平面およびエッジ面が鏡面に仕上げられた鏡面ウエハに加工される。ウエハは、その後のデバイス工程にてその鏡面仕上げされた表面に微細な電気回路が形成されて行くのであるが、エッジ面は金属膜等が不規則に堆積した状態となっている。半導体素子チップに分割されるまではウエハは最初の円板状の形状を保ったままエッジ部を支えにした搬送等の工程が入る。搬送時にウエハの外周側面エッジが不規則な構造形状であると、搬送装置との接触で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る。これを防止するために、電気回路の形成後にエッジ部分の鏡面研磨仕上げをすることが必要となる。 Electronic components such as ICs, LSIs, and VLSIs, which are made from semiconductor materials such as silicon single crystals, have many fine electrical circuits on a wafer sliced from a silicon or other compound semiconductor single crystal ingot into a thin disk shape. It is manufactured on the basis of a small piece-like semiconductor element chip which is divided by writing. The wafer sliced from the ingot is processed into a mirror surface wafer having a plane surface and an edge surface finished to a mirror surface through processes such as lapping, etching, and polishing. A fine electric circuit is formed on the mirror-finished surface of the wafer in the subsequent device process, but the edge surface is in a state where metal films and the like are irregularly deposited. Until the wafer is divided into semiconductor element chips, the wafer is subjected to a process such as conveyance with the edge portion supported while maintaining the original disk shape. If the outer peripheral side edge of the wafer has an irregular structure during transfer, micro-destruction occurs due to contact with the transfer device, or fine particles are generated, or contaminated particles are entrained in the rough surface. In the process, it dissipates and contaminates the surface that has been subjected to precision processing, greatly affecting the yield and quality of the product. In order to prevent this, it is necessary to mirror finish the edge portion after forming the electric circuit.
上述のエッジ研磨は、パッド支持体例えば回転可能なドラムの表面に、合成樹脂発泡体、合成皮革あるいは不織布等からなるポリッシングパッドを貼付した研磨加工機に、工作物であるウエハのエッジ部分を回転させつつ傾斜押圧し、シリカ等の研磨砥粒を成分とした研磨組成物溶液を供給しつつ、エッジ部分の研磨加工を行なう方法で行われる。この際用いられる研磨組成物の砥粒としては、シリコンウエハのエッジポリッシングに用いられるものと同等のコロイダルシリカや、デバイスウエハの面研磨に用いられるヒュームドシリカやセリア、アルミナなどが提案されている。特にコロイダルシリカやヒュームドシリカは微細な粒子であるため平滑な鏡面を得られるので注目されている。
このような研磨組成物は「スラリー」とも呼ばれ、以下にそのように記載することもある。
In the above-described edge polishing, the edge portion of the wafer, which is a workpiece, is rotated on a polishing machine in which a polishing pad made of synthetic resin foam, synthetic leather or nonwoven fabric is attached to the surface of a pad support such as a rotatable drum. It is carried out by a method in which the edge portion is polished while being inclined and pressed and supplying a polishing composition solution containing polishing abrasives such as silica as a component. As abrasive grains of the polishing composition used in this case, colloidal silica equivalent to that used for edge polishing of silicon wafers, fumed silica, ceria, alumina, etc. used for surface polishing of device wafers have been proposed. . In particular, colloidal silica and fumed silica are attracting attention because they are fine particles and can provide a smooth mirror surface.
Such a polishing composition is also referred to as a “slurry” and may be described as such below.
シリカ砥粒を成分とする研磨組成物としては、アルカリ成分を含んだ溶液が一般的に使用される。この加工は、その成分であるアルカリの化学的作用、具体的には酸化珪素膜や金属膜等の被加工物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、ウエハ等被加工物表面に薄い軟質の浸蝕層が形成される。その薄層を微細な砥粒粒子の機械的作用により除去してゆくことにより加工が進むのである。 As a polishing composition containing silica abrasive grains as a component, a solution containing an alkali component is generally used. This processing is an application of the chemical action of alkali, which is a component thereof, specifically, the erosion of a workpiece such as a silicon oxide film or a metal film. That is, a thin soft erosion layer is formed on the surface of a workpiece such as a wafer due to the corrosiveness of alkali. The processing proceeds by removing the thin layer by the mechanical action of fine abrasive grains.
このような加工においては、コロイダルシリカやヒュームドシリカのシリカ粒子の形状は重要なファクターとなる。すなわち、被加工物表面はアルカリによって腐食され薄層が形成されてゆくのであるが、この薄層の除去速度はシリカ粒子の形状によって大きく変化する。シリカ粒子の粒子径を大きくすれば、除去速度は速くなるが、研磨面にスクラッチが発生しやすくなる。また、形状は真球状よりも異型の粒子の方が除去速度は速くなるが、研磨面にスクラッチが発生しやすくなる。ゆえに、その粒子は適度なサイズを有し、適当な形状であって、容易に破壊したり、あるいは高次に凝集してゲル化するものであってはならない。すなわち、シリカ粒子はアルカリにより形成された浸蝕層を機械的作用により効果的に除去してゆくものである。従って、除去後の新しい研磨面に何らかの影響を与えるようなものであってはならないのである。 In such processing, the shape of the silica particles of colloidal silica and fumed silica is an important factor. That is, the surface of the workpiece is corroded by alkali and a thin layer is formed, but the removal rate of this thin layer varies greatly depending on the shape of the silica particles. Increasing the particle size of the silica particles increases the removal rate, but tends to cause scratches on the polished surface. In addition, although the removal rate of particles having a different shape than that of a spherical shape is higher than that of a spherical shape, scratches are likely to occur on the polished surface. Therefore, the particles should have an appropriate size, have an appropriate shape, and cannot be easily broken or highly aggregated and gelled. That is, the silica particles effectively remove the erosion layer formed of alkali by a mechanical action. Therefore, it should not have any influence on the new polished surface after removal.
従来よりデバイスウエハのポリッシングでは、様々な研磨組成物が提案されている。たとえば、特許文献１では、炭酸ナトリウムと酸化剤を含有するコロイダルシリカが開示されている。特許文献２には、エチレンジアミンを含有するコロイダルシリカが開示されている。特許文献３には、繭状の形状をしたシリカ粒子の使用が記載されている。特許文献４には、エチレン・ジアミン・ピロカテコールとシリカの微粉末を含有する水溶液を用いたデバイスウエハの研磨方法が開示されている。特許文献５には、グリシン、過酸化水素、ベンゾトリアゾールとシリカの微粉末を含有する水溶液を用いたデバイスウエハの研磨方法が開示されている。特許文献６には、ＫＯＨ水溶液に平均粒子径５〜３０ｎｍのヒュームドシリカを分散した研磨剤とその製法が開示されている。 Conventionally, various polishing compositions have been proposed for polishing device wafers. For example, Patent Document 1 discloses colloidal silica containing sodium carbonate and an oxidizing agent. Patent Document 2 discloses colloidal silica containing ethylenediamine. Patent Document 3 describes the use of silica particles having a bowl-like shape. Patent Document 4 discloses a device wafer polishing method using an aqueous solution containing ethylene / diamine / pyrocatechol and silica fine powder. Patent Document 5 discloses a device wafer polishing method using an aqueous solution containing fine powders of glycine, hydrogen peroxide, benzotriazole and silica. Patent Document 6 discloses an abrasive in which fumed silica having an average particle diameter of 5 to 30 nm is dispersed in an aqueous KOH solution and a method for producing the same.
上記特許文献１、特許文献２のようにコロイダルシリカを用いる場合には不純物の問題がある。コロイダルシリカは珪酸ソーダを原料として製造されるため銅、亜鉛、ニッケルなどの金属が比較的多く含まれており、適切な材料ではない。特許文献３の繭状の形状をしたシリカ粒子は、有機珪素化合物を原料にして製造されるので高純度であり、好ましい形状でもあるが、このシリカ粒子は柔らかいため、研磨速度が低いことが欠点である。特許文献４、特許文献５ではシリカ粒子の形状に関する記載はない。特許文献６は特定範囲の粒子径のヒュームドシリカを用いたスラリーであるが、平均１次粒子径は比表面積から次式を用いて換算される粒子径であり、単に粒子の太さの程度を反映しているに過ぎない。 When colloidal silica is used as in Patent Document 1 and Patent Document 2, there is a problem of impurities. Colloidal silica is manufactured using sodium silicate as a raw material, and therefore contains a relatively large amount of metals such as copper, zinc, and nickel, and is not an appropriate material. Since the silica particles having a bowl-like shape of Patent Document 3 are produced using an organosilicon compound as a raw material, the silica particles have a high purity and a preferable shape. However, since the silica particles are soft, the polishing rate is low. It is. Patent Document 4 and Patent Document 5 do not describe the shape of silica particles. Patent Document 6 is a slurry using fumed silica having a specific range of particle diameters, but the average primary particle diameter is a particle diameter converted from the specific surface area using the following formula, and is merely a measure of the thickness of the particles. It only reflects.
ｄ＝６／（Ｓ×Ｄ）， ただし、ｄは平均一次粒子径（ｎｍ）、Ｓは比表面積（ｍ２／ｇ）、Ｄはヒュームドシリカの密度（２．２ｇ／ｃｍ３） d = 6 / (S × D), where d is the average primary particle size (nm), S is the specific surface area (m 2 / g), and D is the density of fumed silica (2.2 g / cm 3 ).
デバイスウエハのエッジ部分の研磨加工と、デバイスウエハの平面部分の研磨加工を比較すると、後者に比較し前者は、ポリッシングパッドがエッジ部分に接触する時間が短いため、加工面にかかる圧力を高く、かつ加工面に対するポリッシングパッドの線速度も速くしてある。すなわち、平面ポリッシングに比べ、エッジ部分の研磨加工工程は大変過酷な条件であるといえる。デバイスウエハのエッジ部分はその面粗さは大変粗い。このような加工条件下において、従来のデバイスウエハの平面ポリッシング用研磨組成物を用いても十分な研磨速度と面粗さは得られない。 When the polishing process of the edge part of the device wafer is compared with the polishing process of the flat part of the device wafer, the former has a short time for the polishing pad to contact the edge part, so the pressure applied to the processing surface is high. Moreover, the linear velocity of the polishing pad with respect to the processed surface is also increased. That is, it can be said that the polishing process of the edge portion is a very severe condition as compared with the planar polishing. The edge of the device wafer has a very rough surface. Under such processing conditions, a sufficient polishing speed and surface roughness cannot be obtained even if a conventional polishing composition for planar polishing of device wafers is used.
本発明の目的は、研磨速度が速く、かつ良好な面粗さが得られるデバイスウエハのエッジ部分の鏡面研磨加工を行なうための研磨用研磨組成物を提供することにある。さらに本発明の他の目的は、前述のウエハエッジ研磨用研磨組成物を用いた、デバイスウエハのエッジ部分の鏡面研磨方法を提供することにある。 An object of the present invention is to provide a polishing composition for polishing for carrying out mirror polishing of an edge portion of a device wafer that has a high polishing rate and good surface roughness. Still another object of the present invention is to provide a method for mirror polishing of an edge portion of a device wafer using the above-described polishing composition for polishing a wafer edge.
本発明者等は、砥粒として特定のヒュームドシリカを用い、更に溶液全体に対するシリカ粒子の濃度が２〜３０重量％である水分散液である研磨組成物を用いることにより、デバイスウエハのエッジ部分の鏡面研磨加工が効果的に行なえることを見出し、本発明を完成するに到った。本発明にいうデバイスウエハとは、シリコンウエハ基板表面に二酸化珪素等の絶縁膜を形成したもの、あるいはポリシリコン等の半導体膜、更には銅薄膜等の金属導体膜を施したものを指す。 The present inventors use a specific fumed silica as abrasive grains, and further use a polishing composition which is an aqueous dispersion having a silica particle concentration of 2 to 30% by weight with respect to the entire solution, thereby providing an edge of a device wafer. The inventors have found that the mirror polishing of the portion can be effectively performed, and have completed the present invention. The device wafer referred to in the present invention refers to a silicon wafer substrate surface formed with an insulating film such as silicon dioxide, or a semiconductor film such as polysilicon, and further a metal conductor film such as a copper thin film.
即ち、本発明の第一の発明は、ＢＥＴ法により測定した比表面積が５０〜２００ｍ２／ｇであり、かつＴＥＭ観察による粒子の長径Ａと短径Ｂとの比Ａ／Ｂの平均値が１．２〜７の範囲にあるヒュームドシリカを含むシリカ粒子の濃度が、溶液全体に対して２〜３０重量％である水分散液であることを特徴とするデバイスウエハエッジ研磨用研磨組成物である。
前記研磨用研磨組成物は、塩基（アルカリ剤）を含有し、かつ２５℃におけるｐＨが８〜１１であることが好ましい。
前記研磨用研磨組成物は、２５℃における酸解離定数の逆数の対数値（ｐＫａ）が８．０〜１２．５の弱酸および強塩基を組み合わせた緩衝溶液を含み、かつｐＨ８〜１１の間で緩衝作用を有することが好ましい。
前記弱酸を構成する陰イオンは、炭酸イオン、炭酸水素イオンであり、かつ強塩基を構成する陽イオンがアルカリ金属イオン、コリンイオン、テトラメチルアンモニウムイオンまたは４級アンモニウムイオンのうち少なくとも一つであることが好ましい。
コリンイオン、テトラメチルアンモニウムイオン以外の４級アンモニウムイオンとしてはテトラエチルアンモニウムイオン、ベンジルトリメチルアンモニウムイオン、テトラプロピルアンモニウムイオン、テトラブチルアンモニウムイオン、フェニルトリメチルアンモニウムイオン、メチルトリヒドロキシエチルアンモニウムイオンなどが入手しやすく、好ましい。
前記研磨用研磨組成物は、２５℃における導電率がシリカ粒子１重量％あたり２０ｍＳ／ｍ以上であることが好ましい。
前記ヒュームドシリカは、シリカ粒子全体に対して３０重量％以上含まれることが好ましい。
That is, in the first invention of the present invention, the specific surface area measured by the BET method is 50 to 200 m 2 / g, and the average value of the ratio A / B of the major axis A and the minor axis B of the particles by TEM observation is A polishing composition for polishing a device wafer edge, wherein the concentration of silica particles containing fumed silica in the range of 1.2 to 7 is an aqueous dispersion having a concentration of 2 to 30% by weight based on the entire solution. It is.
The polishing composition for polishing preferably contains a base (alkali agent) and has a pH of 8 to 11 at 25 ° C.
The polishing composition for polishing comprises a buffer solution in which a weak acid and a strong base having a logarithmic value (pKa) of the reciprocal of the acid dissociation constant at 25 ° C. of 8.0 to 12.5 are combined, and the pH is between 8 and 11 It preferably has a buffering action.
The anion constituting the weak acid is carbonate ion or hydrogen carbonate ion, and the cation constituting the strong base is at least one of alkali metal ion, choline ion, tetramethylammonium ion or quaternary ammonium ion. It is preferable.
Quaternary ammonium ions other than choline ions and tetramethylammonium ions include tetraethylammonium ion, benzyltrimethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, phenyltrimethylammonium ion, and methyltrihydroxyethylammonium ion. ,preferable.
The polishing composition for polishing preferably has an electrical conductivity at 25 ° C. of 20 mS / m or more per 1% by weight of silica particles.
The fumed silica is preferably contained in an amount of 30% by weight or more based on the entire silica particles.
また、本発明の第二の発明は、強塩基の水溶液とヒュームドシリカとを混合し、湿式粉砕を行った後、弱酸を添加して緩衝溶液とし、更に湿式粉砕を行うことを特徴とする上記デバイスウエハエッジ研磨用研磨組成物の製造方法である。
さらに、本発明の第三の発明は、ｐＨ８〜１１の間で緩衝作用を有する弱酸および強塩基の水溶液とヒュームドシリカとを混合し、湿式粉砕を行うことを特徴とする上記デバイスウエハエッジ研磨用研磨組成物の製造方法である。
In addition, the second invention of the present invention is characterized in that an aqueous solution of a strong base and fumed silica are mixed and wet pulverized, then a weak acid is added to form a buffer solution, and further wet pulverization is performed. It is a manufacturing method of the said polishing composition for device wafer edge grinding | polishing.
Further, according to a third aspect of the present invention, the device wafer edge polishing is characterized in that an aqueous solution of a weak acid and a strong base having a buffering action between pH 8 and 11 and fumed silica are mixed and wet pulverized. It is a manufacturing method of the polishing composition for water.
本発明の第四の発明は、合成樹脂発泡体、合成皮革あるいは不織布等からなるポリッシングパッドを貼付したパッド支持体を有するエッジ研磨加工機に、被加工物であるデバイスウエハを載置押圧し、前記デバイスウエハエッジ研磨用研磨組成物を供給しつつ、前記パッド支持体及び被加工物の双方あるいはその一方を回転して研磨することを特徴とするデバイスウエハのエッジ研磨加工方法である。 According to a fourth aspect of the present invention, a device wafer as a workpiece is placed and pressed on an edge polishing machine having a pad support to which a polishing pad made of synthetic resin foam, synthetic leather, nonwoven fabric, or the like is attached, An edge polishing method for a device wafer, characterized in that, while supplying the polishing composition for polishing a device wafer edge, both or one of the pad support and the workpiece is rotated and polished.
本発明による研磨組成物を用いれば、デバイスウエハ等のエッジ研磨において卓越した効果が得られる。本発明により、従来比較的対策が不十分であった、ウエハのエッジ部分の鏡面研磨加工において優れた研磨力とその持続性をもった研磨組成物が得られたものであり、関連業界に及ぼす効果は極めて大である。 When the polishing composition according to the present invention is used, an excellent effect can be obtained in edge polishing of a device wafer or the like. According to the present invention, a polishing composition having excellent polishing power and sustainability in mirror polishing of the edge portion of a wafer, which has been relatively insufficient in the past, has been obtained, and this affects the related industries. The effect is extremely large.
ヒュームドシリカは、一般に、四塩化珪素を酸水素炎中で燃焼させて製造される。燃焼時に発生する塩酸成分を含有し、酸性を呈する。製造条件を変えることによって、比表面積がおよそ５０〜５００ｍ２／ｇの製品がある。また、ヒュームドシリカ粒子を酸化アルミニウムで変性した製品もある。市販品としては、Ｄｅｇｕｓｓａ社のＡＥＲＯＳＩＬやＣａｂｏｔ社のＣＡＢ−Ｏ−ＳＩＬなどがあり、それらの水分散液（スラリー）も市販されている。これらのヒュームドシリカ市販品をそのまま水に分散したものは本発明では使用できない。
本発明においては、デバイスウエハエッジ研磨用研磨組成物中に含まれる研磨砥粒としてある特定の粒子径と形状を有するヒュームドシリカを使用する。すなわち、本発明において、研磨砥粒としてのヒュームドシリカは、ＢＥＴ法により測定した比表面積が５０〜２００ｍ２／ｇであり、かつ粒子の長径Ａと短径Ｂとの比Ａ／Ｂが１．２〜７の範囲にあることが肝要である。
Fumed silica is generally produced by burning silicon tetrachloride in an oxyhydrogen flame. Contains a hydrochloric acid component generated during combustion and exhibits acidity. By changing the production conditions, there is a product with a specific surface area of approximately 50 to 500 m 2 / g. There is also a product in which fumed silica particles are modified with aluminum oxide. Commercially available products include Degussa AEROSIL and Cabot CAB-O-SIL, and their aqueous dispersions (slurries) are also commercially available. A product obtained by dispersing these fumed silica commercial products in water as they are cannot be used in the present invention.
In the present invention, fumed silica having a specific particle diameter and shape is used as the abrasive grains contained in the polishing composition for polishing a device wafer edge. That is, in the present invention, fumed silica as abrasive grains has a specific surface area measured by the BET method of 50 to 200 m 2 / g, and the ratio A / B between the major axis A and the minor axis B of the particles is 1. It is important to be in the range of 2-7.
上記のように、比表面積から真球換算で算出した平均一次粒子径は、
ｄ＝６／（Ｓ×Ｄ）
を整理して、下式の関係にある。
２７２０／比表面積（ｍ２／ｇ）＝真球換算で算出した平均一次粒子径（ｎｍ）
As mentioned above, the average primary particle diameter calculated in terms of sphere from the specific surface area is
d = 6 / (S × D)
Are organized as shown below.
2720 / specific surface area (m 2 / g) = average primary particle diameter (nm) calculated in terms of true sphere
したがって、比表面積が５０〜２００ｍ２／ｇとは、平均一次粒子径１３．６〜５４．４ｎｍと記載する方法もあるが、正確ではない。また、メーカーによっては平均一次粒子径を電子顕微鏡によって測定した数値としているところもあり、上式は当てはまらない。
ヒュームドシリカは真球状ではなく、球が２ないし７個連結・分岐した形状、棒状、俵状、繭状、ひも状などのさまざまな粒子が、更に凝集して二次粒子を形成し、不規則な形状のため、真球換算で算出した平均一次粒子径を用いた数値では正確な形状を表しきれない。従って、あくまでも粒子の太さを表すという観点で比表面積を用いた。
Therefore, the specific surface area of 50 to 200 m 2 / g may be described as an average primary particle diameter of 13.6 to 54.4 nm, but is not accurate. In addition, some manufacturers use the average primary particle size as a value measured with an electron microscope, and the above formula does not apply.
Fumed silica is not spherical, but various particles such as 2-7 connected or branched spheres, rods, bowls, bowls, strings, etc. are further aggregated to form secondary particles. Because of the regular shape, the numerical value using the average primary particle diameter calculated in terms of true sphere cannot accurately represent the shape. Therefore, the specific surface area was used from the viewpoint of representing the thickness of the particles.
次に、粒子の長径Ａと短径Ｂの比Ａ／Ｂが１．２〜７の範囲と限定することで、本発明で用いるヒュームドシリカの形状を正確に表すことができ、従来一般の製品と異なることがわかる。このヒュームドシリカは、例えば、従来一般の製品の中でも太いひも状の粒子を短く裁断した形状であり、具体的には５０ｍ２／ｇでＡ／Ｂが２のときは、短径約５０ｎｍで長径約１００ｎｍの俵型であり、２００ｍ２／ｇでＡ／Ｂが５のときは、短径約１０ｎｍで長径約５０ｎｍの棒型である。このようなヒュームドシリカは、従来一般の製品を、ビーズミルやサンドグラインダーなどの強力な粉砕手段を用いて湿式粉砕し、更にそのスラリーから沈降分離（水簸）により粗粒を除去して調製することができる。 Next, by limiting the ratio A / B of the major axis A and the minor axis B of the particles to a range of 1.2 to 7, it is possible to accurately represent the shape of the fumed silica used in the present invention. You can see that it is different from the product. This fumed silica has, for example, a shape obtained by cutting a thick string-like particle in a conventional general product into short cuts. Specifically, when A / B is 2 at 50 m 2 / g, the short diameter is about 50 nm. When the major axis is about 100 nm and the A / B is 5 at 200 m 2 / g, it is a rod type with a minor axis of about 10 nm and a major axis of about 50 nm. Such fumed silica is prepared by wet pulverizing a conventional product using a powerful pulverizing means such as a bead mill or a sand grinder, and removing coarse particles from the slurry by sedimentation (water tank). be able to.
上述の形状のヒュームドシリカは水に分散し安定なコロイド状分散液とすることができる。比表面積が５０ｍ２／ｇよりも小さいものは原料の段階で製造しにくく、入手が困難である。比表面積が２００ｍ２／ｇよりも大きいものは、使用中に２次凝集をするなど、物性が変化しやすく、研磨性能を安定させることができない。同様の理由から、比表面積が７０〜１５０ｍ２／ｇの範囲の粒子は更に好ましい。一方、Ａ／Ｂが１．２より小さいものは研磨力が低く本発明の目的を達することができない。Ａ／Ｂが７より大きいものは使用中に２次凝集をするなど、物性が変化しやすく、研磨性能を安定させることができない。研磨組成物の研磨力および安定性をより向上させる観点から、Ａ／Ｂは、２〜５であることが好ましい。このヒュームドシリカは、溶液中のシリカ粒子全体に対して３０重量％以上含まれることが好ましい。また、本発明では、ヒュームドシリカ以外の他のシリカ粒子を含有していてもよい。他のシリカ粒子としては、上記特定の値を満たさないヒュームドシリカや、コロイダルシリカ等、通常デバイスウエハエッジ研磨に用いる研磨粒子が挙げられる。 The fumed silica having the above shape can be dispersed in water to form a stable colloidal dispersion. Those having a specific surface area of less than 50 m 2 / g are difficult to produce at the raw material stage and are difficult to obtain. When the specific surface area is larger than 200 m 2 / g, the physical properties are likely to change, such as secondary aggregation during use, and the polishing performance cannot be stabilized. For the same reason, particles having a specific surface area of 70 to 150 m 2 / g are more preferable. On the other hand, when A / B is smaller than 1.2, the polishing power is low and the object of the present invention cannot be achieved. When A / B is greater than 7, the physical properties are likely to change, such as secondary aggregation during use, and the polishing performance cannot be stabilized. From the viewpoint of further improving the polishing power and stability of the polishing composition, A / B is preferably 2 to 5. The fumed silica is preferably contained in an amount of 30% by weight or more based on the entire silica particles in the solution. In the present invention, silica particles other than fumed silica may be contained. Examples of other silica particles include abrasive particles usually used for device wafer edge polishing, such as fumed silica and colloidal silica that do not satisfy the specific value.
本発明の研磨組成物において、ヒュームドシリカを含むシリカ粒子の濃度は、溶液全体に対して２〜３０重量％であることが好ましい。研磨組成物の研磨力をより向上させる観点から、シリカ粒子の濃度は、１０〜２５重量％であることが望ましい。また、研磨組成物は、塩基（アルカリ剤）を含有し、かつ２５℃におけるｐＨが８〜１１であることも好ましい。 In the polishing composition of the present invention, the concentration of the silica particles containing fumed silica is preferably 2 to 30% by weight with respect to the entire solution. From the viewpoint of further improving the polishing power of the polishing composition, the concentration of the silica particles is preferably 10 to 25% by weight. Moreover, it is also preferable that polishing composition contains a base (alkali agent) and the pH in 25 degreeC is 8-11.
さらに、本発明においては、実際の研磨加工時に安定な研磨力を持続するために、溶液全体のｐＨを８〜１１の範囲に保つことが好ましい。ｐＨが８未満であると研磨速度は低下し実用の範囲からは外れることがある。また、ｐＨが１１を超えると、研磨部以外でのエッチングが強くなりすぎ、またシリカ粒子が凝集を始めるため研磨組成物の安定性が低下しこれも実用の範囲から外れることがある。さらに、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により容易に変化しないことが好ましい。特にエッジ研磨においては、研磨組成物は循環流として使用される。すなわち、スラリータンクから研磨部位へ供給された研磨組成物は、スラリータンクへ戻す方式で使用される。従来技術のアルカリ剤だけを含む研磨組成物は、使用時に短時間でｐＨが低下してしまう。これは、被研磨物の溶解や洗浄水の混入によるもので、スラリータンク内の研磨組成物のｐＨを一定に保つのは非常に煩わしい作業となり、削り残り品などの発生を起こしやすくなる。 Furthermore, in the present invention, it is preferable to maintain the pH of the entire solution in the range of 8 to 11 in order to maintain a stable polishing force during actual polishing. When the pH is less than 8, the polishing rate decreases and may be out of the practical range. On the other hand, when the pH exceeds 11, the etching at the portion other than the polishing portion becomes too strong, and the silica particles start to aggregate, so that the stability of the polishing composition is lowered, which may be out of the practical range. Furthermore, it is preferable that this pH does not change easily due to possible external conditions such as friction, heat, contact with outside air, or mixing with other components. Particularly in edge polishing, the polishing composition is used as a circulating flow. That is, the polishing composition supplied from the slurry tank to the polishing site is used in a manner of returning to the slurry tank. The polishing composition containing only the alkali agent of the prior art is lowered in pH in a short time when used. This is due to dissolution of the object to be polished and mixing of cleaning water. It is very troublesome to keep the pH of the polishing composition in the slurry tank constant, and it is easy to cause uncut parts.
従って、本発明においては研磨組成物自体を、外的条件の変化に対してｐＨ変化の幅が少ない、所謂緩衝作用の強い液とすることが好ましい。緩衝溶液を形成するためには、２５℃における酸解離定数（Ｋａ）の逆数の対数値（ｐＫａ）が８．０〜１２．５の範囲にある弱酸および強塩基を組み合わせて使用すればよい。２５℃における酸解離定数の逆数の対数値（ｐＫａ）が８．０未満の場合、ｐＨを上昇させるために、弱酸及び強塩基を大量に添加することが必要となるため好ましくない。２５℃における酸解離定数の逆数の対数値（ｐＫａ）が１２．５より大きい場合、ｐＨを８〜１１の範囲で安定させる大きな緩衝作用を持つ緩衝溶液を形成しにくいため好ましくない。 Therefore, in the present invention, it is preferable that the polishing composition itself is a liquid having a strong so-called buffering action, in which the range of pH change is small with respect to changes in external conditions. In order to form a buffer solution, a weak acid and a strong base whose logarithmic value (pKa) of the reciprocal of the acid dissociation constant (Ka) at 25 ° C. is in the range of 8.0 to 12.5 may be used in combination. When the logarithmic value (pKa) of the reciprocal of the acid dissociation constant at 25 ° C. is less than 8.0, it is not preferable because it is necessary to add a large amount of a weak acid and a strong base in order to increase the pH. If the logarithmic value (pKa) of the reciprocal of the acid dissociation constant at 25 ° C. is larger than 12.5, it is not preferable because it is difficult to form a buffer solution having a large buffering action that stabilizes the pH in the range of 8-11.
本発明において、緩衝作用を有する研磨組成物溶液の形成に使用する弱酸としては、炭酸（ｐＫａ＝６．３５、１０．３３）、ホウ酸（ｐＫａ＝９．２４）、燐酸（ｐＫａ＝２．１５、７．２０、１２．３５）類及び水溶性の有機酸等があげられ、またその混合物であってもかまわない。また、強塩基としては、アルカリ金属の水酸化物、四級アンモニウムの水酸化物などが使用できる。本発明で述べる緩衝溶液とは、上述の組合せで形成され、溶液の中で弱酸が価数の異なるイオンとして解離している状態、または、解離状態と未解離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。 In the present invention, weak acids used for forming a polishing composition solution having a buffering action include carbonic acid (pKa = 6.35, 10.33), boric acid (pKa = 9.24), phosphoric acid (pKa = 2. 15, 7.20, 12.35) and water-soluble organic acids, and a mixture thereof may also be used. As the strong base, alkali metal hydroxides, quaternary ammonium hydroxides, and the like can be used. The buffer solution described in the present invention refers to a solution formed by the combination described above, in which a weak acid is dissociated as ions having different valences, or a dissociated state and an undissociated state coexist. It is characterized by little change in pH even when a small amount of acid or base is mixed.
本発明においては、研磨組成物溶液の導電率を高くすることにより、研磨加工速度を著しく向上することができる。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値である。本発明においては単位長あたりの導電率の数値（ｍｉｃｒｏ・Ｓｉｅｍｅｎｓ）をシリカ１重量％当たりに換算した数値で示す。本発明においては、２５℃における導電率が２０ｍＳ／ｍ／１％−ＳｉＯ２以上であれば研磨加工速度の向上に対して好ましく、２５ｍＳ／ｍ／１％−ＳｉＯ２以上であれば更に好ましい。導電率を上昇させる方法としては、次の二方法がある。一つは緩衝溶液の濃度を高くする方法、もう一つは塩類を添加する方法である。緩衝溶液の濃度を高くするには、酸と塩基とのモル比を変えずに濃度のみを高くすればよい。塩類を添加する方法に用いる塩類は、酸及び塩基の組み合わせより構成されるが、酸としては、強酸、弱酸いずれであってもかまわず、鉱酸および、有機酸が使用でき、その混合物でもよい。塩基としては、強塩基、弱塩基いずれであってもよく、アルカリ金属の水酸化物、水溶性の四級アンモニウムの水酸化物、水溶性アミンが使用でき、その混合物であってもかまわない。弱酸及び強塩基、強酸及び弱塩基、弱酸及び弱塩基の組み合わせで添加する場合は、緩衝溶液のｐＨを変化させることがあるため、大量に添加することは望ましくない。前述の二方法を併用してもかまわない。 In the present invention, the polishing rate can be remarkably improved by increasing the conductivity of the polishing composition solution. The electrical conductivity is a numerical value indicating the ease of passing electricity in the liquid, and is an inverse value of the electrical resistance value per unit length. In the present invention, the numerical value of conductivity per unit length (micro · Siemens) is shown as a numerical value converted to 1% by weight of silica. In the present invention, further preferably equal to preferably against improvement of polishing rate if the conductivity at 25 ° C. is 20mS / m / 1% -SiO 2 or more, 25mS / m / 1% -SiO 2 or more. There are the following two methods for increasing the conductivity. One is a method of increasing the concentration of the buffer solution, and the other is a method of adding salts. In order to increase the concentration of the buffer solution, it is only necessary to increase the concentration without changing the molar ratio of acid to base. The salt used in the method of adding salts is composed of a combination of an acid and a base, but the acid may be either a strong acid or a weak acid, and a mineral acid and an organic acid can be used, or a mixture thereof may be used. . The base may be either a strong base or a weak base, and an alkali metal hydroxide, a water-soluble quaternary ammonium hydroxide, a water-soluble amine, or a mixture thereof may be used. When adding in a combination of a weak acid and a strong base, a strong acid and a weak base, a weak acid and a weak base, the pH of the buffer solution may be changed. The above two methods may be used in combination.
また、本発明の研磨組成物は、銅と水不溶性のキレート化合物を形成するキレート化剤を含有していることが好ましい。例えば、キレート化剤としては、ベンゾトリアゾールのようなアゾール類やキノリノール、キナルジン酸のようなキノリン誘導体など公知の化合物が好ましい。
本発明の研磨組成物の物性を改良するため、界面活性剤、分散剤、沈降防止剤などを併用することができる。界面活性剤、分散剤、沈降防止剤としては、水溶性の有機物、無機層状化合物などがあげられる。また、本発明の研磨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。本発明の研磨組成物は、研磨時にコロイダルシリカ等の他の研磨剤、塩基、添加剤、水等を混合して調製してもよい。
Moreover, it is preferable that the polishing composition of this invention contains the chelating agent which forms copper and a water-insoluble chelate compound. For example, as the chelating agent, known compounds such as azoles such as benzotriazole, quinoline derivatives such as quinolinol and quinaldic acid are preferable.
In order to improve the physical properties of the polishing composition of the present invention, a surfactant, a dispersant, an anti-settling agent and the like can be used in combination. Examples of the surfactant, dispersant, and anti-settling agent include water-soluble organic substances and inorganic layered compounds. Moreover, although the polishing composition of the present invention is an aqueous solution, an organic solvent may be added. The polishing composition of the present invention may be prepared by mixing other polishing agents such as colloidal silica, a base, additives, water and the like during polishing.
本発明の研磨組成物の製造方法は、特に限定されないが、例えば以下のようにして製造することができる。
強塩基の水溶液とヒュームドシリカとを混合し、湿式粉砕を行いヒュームドシリカを分散させた後、弱酸を添加して緩衝溶液とし、更に湿式粉砕を行う。湿式粉砕は、ビーズミルやサンドグラインダーなどの強力な粉砕手段を用いて行い、更にそのスラリーから沈降分離により粗粒を除去することが好ましい。得られたヒュームドシリカスラリーに必要に応じて弱酸、強塩基、脱イオン水、及び導電率調整のための塩類等を適宜加えて本発明の研磨組成物とする。
または、ｐＨ８〜１１の間で緩衝作用を有する弱酸および強塩基の水溶液をあらかじめ調製し、この緩衝溶液とヒュームドシリカとを混合して湿式粉砕を行い、得られたヒュームドシリカスラリーに上記と同様の各種添加剤を加えて研磨組成物とすることもできる。
Although the manufacturing method of the polishing composition of this invention is not specifically limited, For example, it can manufacture as follows.
An aqueous solution of a strong base and fumed silica are mixed, wet pulverized to disperse the fumed silica, and then a weak acid is added to form a buffer solution, followed by wet pulverization. The wet pulverization is preferably performed using a powerful pulverization means such as a bead mill or a sand grinder, and further, coarse particles are preferably removed from the slurry by sedimentation. If necessary, a weak acid, a strong base, deionized water, salts for adjusting conductivity, and the like are appropriately added to the obtained fumed silica slurry to obtain the polishing composition of the present invention.
Alternatively, an aqueous solution of a weak acid and a strong base having a buffering action between pH 8 and 11 is prepared in advance, the buffer solution and fumed silica are mixed, and wet pulverization is performed. Various kinds of similar additives can be added to form a polishing composition.
次に本発明の研磨組成物を用いたエッジ研磨加工方法について説明する。
エッジポリッシングの場合、一般的には回転可能なパッド支持体の表面に、合成樹脂発泡体、合成皮革あるいは不織布等からなるポリッシングパッドを貼付した研磨加工機に、ワーク（被加工物）であるべべリングを施したシリコンウエハ等のエッジ部分を回転させつつ傾斜押圧し、研磨組成物溶液を供給しながら、エッジ部分の研磨加工を行なう方法で行われる。本発明に用いるエッジポリッシング用加工機とは、例えばスピードファム社製ＥＰ−ＩＶ型エッジポリッシュ装置に示されるようなものであり、表面にポリッシングパッドを貼付した回転可能なパッド支持体と、ワークを把持し回転し任意の角度で傾斜させる把持部とからなり、該把持部に取り付けられたワークのエッジ部分を前記パッド支持体に押圧し、本発明の研磨組成物を供給しながらワークとパッド支持体の双方を回転せしめ、ワークのエッジ部分の鏡面研磨加工を行なう。即ち、回転しつつ少しずつ上昇あるいは下降して位置を変えてゆくパッド支持体に、ワークを回転させながら一定の角度で押しあて、本発明の研磨組成物を加工部分に滴下しながらポリッシングを行なう。本発明の研磨組成物を用いたデバイスウエハエッジの具体的研磨加工方法は以下に述べる実施例にて明らかにされよう。なお、装置については上記の記載に限定されるものではなく、例えば特開２０００−３１７７８８号公報、特開２００２−３６０７９号公報などに記載のいかなる装置も使用できる。
Next, an edge polishing method using the polishing composition of the present invention will be described.
In the case of edge polishing, generally, a work (workpiece) should be placed on a polishing machine in which a polishing pad made of synthetic resin foam, synthetic leather or nonwoven fabric is attached to the surface of a rotatable pad support. The edge portion of a ringed silicon wafer or the like is inclined and pressed while rotating, and the edge portion is polished while supplying the polishing composition solution. The edge polishing processing machine used in the present invention is, for example, as shown in an EP-IV type edge polishing apparatus manufactured by Speed Fam Co., Ltd., and a rotatable pad support with a polishing pad attached to the surface, and a workpiece. A gripping portion that grips, rotates, and tilts at an arbitrary angle, presses an edge portion of the workpiece attached to the gripping portion against the pad support, and supplies the polishing composition of the present invention to support the workpiece and the pad Rotate both sides of the body and perform mirror polishing on the edge of the workpiece. That is, polishing is carried out while dripping the polishing composition of the present invention onto a processed portion by pressing the workpiece against a pad support that is gradually raised or lowered while rotating and changing the position while rotating the workpiece. . The specific polishing method of the device wafer edge using the polishing composition of the present invention will be clarified in the examples described below. The device is not limited to the above description, and any device described in, for example, Japanese Patent Application Laid-Open Nos. 2000-317788 and 2002-36079 can be used.
次に、実施例及び比較例をあげて本発明のデバイスウエハエッジ研磨用研磨組成物、及びそれを用いた研磨加工方法を具体的に説明するが、本発明はこれら実施例により何ら限定されるものではない。
（実施例１〜１２、比較例１〜８）
＜研磨組成物の調製＞
純水７０重量部にヒュームドシリカ１５重量部を加えて強力に攪拌して分散させ、微量の水酸化テトラメチルアンモニウムを加えてｐＨを８とした。次いで、この高粘性なスラリーを、０．５ｍｍのジルコニアビーズを粉砕媒体とするサンドグラインダー（アイメックス社製：４ＴＳＧ−１／４型）の容器に仕込んで、２０００ｒｐｍで粉砕を行った。粉砕後、内容物を取り出し、ジルコニアビーズを篩で取り除き、粉砕スラリーを回収した。粉砕スラリーは低粘性になっており、ここにヒュームドシリカ１５重量部を再度加えて強力に攪拌して分散させ、微量の水酸化テトラメチルアンモニウムを加えて再びｐＨを８とした。次いで上記サンドグラインダーによる粉砕を再度行い、ジルコニアビーズを篩で取り除き、シリカ濃度３０％の粉砕スラリーを回収した。ヒュームドシリカの酸成分によりｐＨが僅かに低下したので、再度微量の水酸化テトラメチルアンモニウムでｐＨを８とした。
ヒュームドシリカは、ＢＥＴ比表面積１３０ｍ２／ｇの市販品ａと、ＢＥＴ比表面積５０ｍ２／ｇの市販品ｂを使用した。
Next, the polishing composition for polishing a device wafer edge of the present invention and the polishing method using the same will be described with reference to examples and comparative examples, but the present invention is not limited to these examples. It is not a thing.
(Examples 1-12, Comparative Examples 1-8)
<Preparation of polishing composition>
15 parts by weight of fumed silica was added to 70 parts by weight of pure water and dispersed by vigorous stirring, and a slight amount of tetramethylammonium hydroxide was added to adjust the pH to 8. Next, this highly viscous slurry was charged into a sand grinder (made by IMEX: 4TSG-1 / 4 type) using 0.5 mm zirconia beads as a grinding medium, and pulverized at 2000 rpm. After grinding, the contents were taken out, the zirconia beads were removed with a sieve, and the ground slurry was recovered. The pulverized slurry had a low viscosity, and 15 parts by weight of fumed silica was again added thereto, and the mixture was vigorously stirred and dispersed. The trace amount of tetramethylammonium hydroxide was added to adjust the pH to 8. Subsequently, the grinding by the sand grinder was performed again, the zirconia beads were removed with a sieve, and the grinding slurry having a silica concentration of 30% was recovered. Since the pH was slightly lowered by the acid component of fumed silica, the pH was adjusted to 8 again with a small amount of tetramethylammonium hydroxide.
As the fumed silica, a commercial product a having a BET specific surface area of 130 m 2 / g and a commercial product b having a BET specific surface area of 50 m 2 / g were used.
市販品ａを用いて得られたスラリー中のヒュームドシリカ（シリカＡ）は、ＢＥＴ比表面積１６０ｍ２／ｇで、Ａ／Ｂが５であり、市販品ｂを用いて得られたスラリー中のヒュームドシリカ（シリカＢ）は、ＢＥＴ比表面積７０ｍ２／ｇで、Ａ／Ｂが２であった。比較として、市販品ａの粉砕時間を短くしてＢＥＴ比表面積１５０ｍ２／ｇで、Ａ／Ｂが１５のヒュームドシリカ（シリカＣ）を含むスラリーを調製した。更に、比較として、シリカ濃度３０％で、ＢＥＴ比表面積７０ｍ２／ｇ、Ａ／Ｂが１．０の真球状のコロイダルシリカ（シリカＤ）を用いた。なお、粉砕したヒュームドシリカをそのまま乾燥すると水酸化テトラメチルアンモニウムによりシリカが一部溶解してしまい、ＢＥＴ法により測定されるＢＥＴ比表面積が実際の値よりも低くなる。そのため、粉砕したヒュームドシリカを希塩酸でｐＨ３にした後、テフロン（登録商標）皿上で乾燥させ、乾燥粉末をろ紙に移し、塩素が検出されなくなるまで純水で洗浄した後、再度乾燥させて測定試料とした。
それぞれのシリカスラリーは、純水で所定のシリカ濃度に希釈した後、表１、表２記載の薬剤を所定量加えて、研磨組成物として用いた。なお、上記粉砕工程で使用した水酸化テトラメチルアンモニウムは表に記載の薬剤量には含まれない。
添加物のうち、炭酸水素テトラメチルアンモニウム、炭酸水素カリウムは弱酸としての炭酸（ｐＫａ＝１０．３３）と強塩基との組み合わせになる塩であり本発明の緩衝溶液である。フッ化カリウムは、導電率を上げるための添加物である。上述の方法にて各々デバイスウエハの研磨実験を行なった。本研磨加工試験では、酸化珪素膜、窒化チタン膜、金属銅膜の積層した８インチのシリコンウエハを使用した。
The fumed silica (silica A) in the slurry obtained using the commercial product a has a BET specific surface area of 160 m 2 / g, A / B is 5, and the fumed silica in the slurry obtained using the commercial product b The fumed silica (silica B) had a BET specific surface area of 70 m 2 / g and an A / B of 2. As a comparison, a slurry containing fumed silica (silica C) having a BET specific surface area of 150 m 2 / g and A / B of 15 was prepared by shortening the pulverization time of the commercial product a. Further, for comparison, a spherical colloidal silica (silica D) having a silica concentration of 30%, a BET specific surface area of 70 m 2 / g, and A / B of 1.0 was used. If the pulverized fumed silica is dried as it is, the silica is partially dissolved by tetramethylammonium hydroxide, and the BET specific surface area measured by the BET method becomes lower than the actual value. Therefore, after pulverized fumed silica is adjusted to pH 3 with dilute hydrochloric acid, it is dried on a Teflon (registered trademark) dish, the dried powder is transferred to a filter paper, washed with pure water until chlorine is no longer detected, and then dried again. A measurement sample was obtained.
Each of the silica slurries was diluted with pure water to a predetermined silica concentration, and then a predetermined amount of chemicals shown in Tables 1 and 2 were added and used as a polishing composition. In addition, the tetramethylammonium hydroxide used at the said grinding | pulverization process is not contained in the chemical | medical agent quantity described in a table | surface.
Among the additives, tetramethylammonium hydrogen carbonate and potassium hydrogen carbonate are salts that are a combination of carbonic acid (pKa = 10.33) as a weak acid and a strong base, and are the buffer solution of the present invention. Potassium fluoride is an additive for increasing electrical conductivity. Each of the device wafers was polished by the above-described method. In this polishing processing test, an 8-inch silicon wafer in which a silicon oxide film, a titanium nitride film, and a metal copper film were stacked was used.
＜研磨試験＞
本発明に使用したデバイスウエハエッジ研磨装置およびそれによる研磨条件は以下の通りである。
研磨装置：スピードファム株式会社製、ＥＰ−ＩＶ型エッジポリッシュ装置
ドラム回転数：８００ＲＰＭ
ウエハ回転速度：６０秒／ＲＥＶ
ウエハ回転数：４回／枚
研磨布：ＤＲＰ−ＩＩ（スピードファム株式会社製）
加重：２．５ｋｇ
研磨組成物流量：２５０ｍｌ／分
<Polishing test>
The device wafer edge polishing apparatus and polishing conditions used in the present invention are as follows.
Polishing device: EP-IV type edge polishing device manufactured by Speed Fem Co., Ltd. Drum rotation speed: 800 RPM
Wafer rotation speed: 60 seconds / REV
Wafer rotation speed: 4 times / sheet Polishing cloth: DRP-II (manufactured by Speed Fem Co., Ltd.)
Weight: 2.5kg
Polishing composition flow rate: 250 ml / min
研磨組成物のｐＨはｐＨメーターを用いて測定した。導電率は導電率計にて測定した。研磨速度は、研磨前後のシリコンウエハの重量差より求めた。研磨面の評価は、ヘイズ及ピットの状態を集光灯下で目視により観察すること、及びエッジポリッシュが不完全であることによって発生する削り残りを、光学顕微鏡を用い、８００倍の倍率で加工後のワーク全周を調べることにより行った。 The pH of the polishing composition was measured using a pH meter. The conductivity was measured with a conductivity meter. The polishing rate was determined from the weight difference between the silicon wafers before and after polishing. The polished surface is evaluated by visually observing the state of haze and pits under a condensing lamp, and processing the remaining shavings generated by incomplete edge polishing at a magnification of 800 times using an optical microscope. This was done by examining the entire workpiece later.
表１及び表２に示した実施例１〜１２および比較例１〜８の研磨組成物を用いて、研磨組成物を循環使用してエッジ部分の鏡面研磨加工試験を行なった。実施例１〜１２および比較例１〜８の研磨組成物を用いた研磨加工試験すべてにおいて、ヘイズ及ピットは見られなかった。他の評価結果を表１及び表２に併記する。なお、表中において使用する略号は次のものを示す。ＴＭＡＯＨ：水酸化テトラメチルアンモニウム、ＫＨＣＯ３：炭酸水素カリウム、ＴＭＡＨＣＯ３：炭酸水素テトラメチルアンモニウム、ＫＦ：フッ化カリウム。表中におけるこれらの添加量は、研磨組成物中のシリカ１ｋｇに対するモル数（ｍｏｌ／ｋｇ−ＳｉＯ２）で示した。また、導電率の単位はシリカ粒子１重量％あたり（ｍＳ／ｍ／１％−ＳｉＯ２）である。 Using the polishing compositions of Examples 1 to 12 and Comparative Examples 1 to 8 shown in Tables 1 and 2, the polishing composition was circulated and used to perform a mirror polishing test of the edge portion. In all polishing processing tests using the polishing compositions of Examples 1 to 12 and Comparative Examples 1 to 8, no haze and pits were observed. Other evaluation results are also shown in Tables 1 and 2. In addition, the symbol used in a table | surface shows the following. TMAOH: tetramethylammonium hydroxide, KHCO 3 : potassium hydrogen carbonate, TMAHCO 3 : tetramethyl ammonium hydrogen carbonate, KF: potassium fluoride. These addition amounts in the table are indicated by the number of moles (mol / kg-SiO 2 ) relative to 1 kg of silica in the polishing composition. The unit of conductivity is silica particles per 1 wt% (mS / m / 1% -SiO 2).
表１の実施例に示す結果から明らかなように、Ａ／Ｂが１．２〜７の範囲内にあり、シリカの濃度が２〜３０重量％であり、かつ２５℃における酸解離定数の逆数の対数値が８．０〜１２．５の弱酸および強塩基を組み合わせた緩衝溶液を含むｐＨ８〜１１の間で緩衝作用を有するようにした研磨組成物で、研磨組成物を循環使用してエッジ部分の加工を行なった実験においては、研磨速度、表面状態ともに安定して満足し得る結果が得られ、また、表面の品質にも重大な欠陥がなく良好であった。これに対し、表２の比較例に示すようにＢ／Ａが本発明の範囲を逸脱した研磨組成物を用いた場合、研磨速度が低く、シリカ濃度を高くしても研磨速度がそれほど上がらない。そのため、循環使用においては安定した研磨が行われず、研磨が不十分であるため、もとの粗い面が残っていてポリッシングされていない。また、コロイダルシリカのようにＡ／Ｂが１．０の真球状のシリカは研磨速度が低く、良好な表面状態を得ることができないが、本発明のヒュームドシリカとの併用ではその性能が大幅に改善されることが判明した。更に、本発明のヒュームドシリカに本発明の範囲を逸脱したヒュームドシリカが少量混在しても、本発明のヒュームドシリカの性能を大幅に劣化させることがないことも判明した。 As is apparent from the results shown in the examples of Table 1, A / B is in the range of 1.2 to 7, the concentration of silica is 2 to 30% by weight, and the reciprocal of the acid dissociation constant at 25 ° C. A polishing composition having a buffering action between pH 8 and 11 including a buffer solution in which a weak acid and a strong base having a logarithmic value of 8.0 to 12.5 are combined. In an experiment in which a part was processed, stable and satisfactory results were obtained for both the polishing rate and the surface condition, and the surface quality was good without significant defects. On the other hand, as shown in the comparative example of Table 2, when a polishing composition having B / A deviating from the scope of the present invention was used, the polishing rate was low and the polishing rate did not increase so much even if the silica concentration was increased. . Therefore, stable polishing is not performed in cyclic use, and polishing is insufficient, so that the original rough surface remains and is not polished. In addition, spherical silica with A / B of 1.0 such as colloidal silica has a low polishing rate and cannot obtain a good surface state. However, when used in combination with the fumed silica of the present invention, the performance is greatly improved. It turned out to be improved. Furthermore, it has been found that even if a small amount of fumed silica deviating from the scope of the present invention is mixed in the fumed silica of the present invention, the performance of the fumed silica of the present invention is not significantly deteriorated.
（実施例１３）
実施例３における、弱酸としての炭酸（ｐＫａ＝１０．３３）と強塩基との組み合わせになる塩である炭酸水素カリウム（ＫＨＣＯ３）を、同モル量の水酸化テトラメチルアンモニウム（ＴＭＡＯＨ）に置換した以外は、実施例３と同じ研磨組成物を調製した。すなわち、シリカＡを１５重量％、水酸化テトラメチルアンモニウムを０．１６８ｍｏｌ／ｋｇ−ＳｉＯ２、フッ化カリウム（ＫＦ）を０．０３４ｍｏｌ／ｋｇ−ＳｉＯ２の組成のスラリーを調製した。水酸化テトラメチルアンモニウムは０．０８と０．０８８の加算された量である。このスラリーのｐＨは１１．５であり、スラリーの安定化のため５％硝酸を滴下してｐＨを１１．０に調節し、研磨組成物とした。研磨試験には実施例３と同じ、酸化珪素膜、窒化チタン膜、金属銅膜の積層した８インチのシリコンウエハを使用し、実施例３と同じ研磨条件で試験を行った。研磨試験中、スラリータンク内の研磨組成物を攪拌しつつ、ｐＨを測定し、ｐＨが１０．５に低下した時点で２５％水酸化テトラメチルアンモニウム水溶液を滴下して、ｐＨを１１．０とする方法で、研磨組成物のｐＨを１０．５と１１．０との間に調節した。
循環１回目から１０回目まで、研磨速度は２．３±０．１ｍｇ／ｍｉｎで安定しており、表面の品質にも重大な欠陥がなく良好であった。
(Example 13)
In Example 3, potassium hydrogen carbonate (KHCO 3 ), which is a salt of a combination of carbonic acid (pKa = 10.33) as a weak acid and a strong base, was replaced with an equimolar amount of tetramethylammonium hydroxide (TMAOH). A polishing composition identical to that of Example 3 was prepared except that. That is, the silica A 15 wt%, 0.168mol / kg-SiO 2 tetramethylammonium hydroxide, potassium fluoride (KF) to prepare a slurry composition of 0.034mol / kg-SiO 2. Tetramethylammonium hydroxide is an added amount of 0.08 and 0.088. The slurry had a pH of 11.5. To stabilize the slurry, 5% nitric acid was added dropwise to adjust the pH to 11.0 to obtain a polishing composition. In the polishing test, an 8-inch silicon wafer in which a silicon oxide film, a titanium nitride film, and a metal copper film were laminated as in Example 3 was used, and the test was performed under the same polishing conditions as in Example 3. During the polishing test, the pH was measured while stirring the polishing composition in the slurry tank. When the pH dropped to 10.5, a 25% tetramethylammonium hydroxide aqueous solution was added dropwise to adjust the pH to 11.0. The pH of the polishing composition was adjusted between 10.5 and 11.0.
From the first cycle to the 10th cycle, the polishing rate was stable at 2.3 ± 0.1 mg / min, and the surface quality was good with no significant defects.
Claims (9)
強塩基の水溶液とヒュームドシリカとを混合し、湿式粉砕を行った後、弱酸を添加して緩衝溶液とし、更に湿式粉砕を行う工程を有することを特徴とするデバイスウエハエッジ研磨用研磨組成物の製造方法。 A method for producing a polishing composition for polishing a device wafer edge according to claim 3 or 4,
A polishing composition for polishing a device wafer edge, comprising: mixing an aqueous solution of a strong base and fumed silica, performing wet grinding, adding a weak acid to form a buffer solution, and further performing wet grinding. Manufacturing method.
ｐＨ８〜１１の間で緩衝作用を有する弱酸および強塩基の水溶液とヒュームドシリカとを混合し、湿式粉砕を行う工程を有することを特徴とするデバイスウエハエッジ研磨用研磨組成物の製造方法。 A method for producing a polishing composition for polishing a device wafer edge according to claim 3 or 4,
A method for producing a polishing composition for polishing a device wafer edge, comprising a step of mixing an aqueous solution of a weak acid and a strong base having a buffering action between pH 8 and 11 and fumed silica and performing wet grinding.
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| TW95113620A TWI401306B (en) | 2005-06-02 | 2006-04-17 | A polishing composition for polishing a wafer edge, a method for manufacturing the same, and a polishing method |
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| JP2009256507A (en) * | 2008-04-18 | 2009-11-05 | Shin Etsu Chem Co Ltd | Silicone rubber composition for sewing air bag filling material |
| JP2014092770A (en) * | 2012-11-07 | 2014-05-19 | Toray Ind Inc | Molding material and method for manufacturing molding material |
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| TWI401306B (en) | 2013-07-11 |
| TW200726831A (en) | 2007-07-16 |
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