通常、CMPを行う前には使用する研磨パッドにブレークイン(Break in)と呼ばれる表面の"目立て"を研磨機定盤上で行う必要がある。我々は、ブレークイン後の研磨パッド表面の解析結果から、研磨パッドの表面加工を事前に行うことで、ブレークインを省略もしくは短縮することが出来ることを新たに見出した。本報では、この表面加工に伴うパッド表面形状の変化と研磨特性について調査した結果を報告する。

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In Chemical Mechanical Polishing (CMP) process, surface roughness of polishing pad has critical effect on material removal process because the material on a wafer surface is removed by direct contact with rough pad surface. However, when it comes to mentioning about the effect of roughness on CMP, loose definition of surface roughness, e.g. Ra, has been used to describe the topological state of pad surface with weak physical or experimental background. Furthermore, little research has been done about the effect of pad roughness on CMP process. Therefore, the authors conducted extensive experimental work as well as empirical modeling approach on surface roughness of pad to find out parameters that best describe the effect of roughness on material removal in CMP.
The authors found that arithmetic average roughness (Ra), which is most frequently referred parameter as ″roughness″, has weak correlation with material removal rate and has weak physical relationship with polishing phenomenon, whereas skewness (Rsk), peak roughness (Rp) and reduced peak height (Rpk) are found three most relevant parameters that showed high correlation with removal rate. Among them, Rpk seems most appropriate parameter to describe the relationship between roughness and material removal in terms of considering the definition of its physical meaning. Also, further research combined with empirical modeling showed that the deviation of removal rate over wafer surface (WIWNU) is strongly affected by spatial uniformity of roughness of Rpk. These results suggest basic understanding of material removal phenomenon such that polishing is strongly dominated by direct contact with pad asperity tips, especially with highest spots over the contact area. These research results are expected to be useful to understand or to develop advanced CMP process.

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Monitoring system for CMP equipment, which uses friction force and temperature measurement, was newly developed. The correlation between friction and CMP results can be investigated in terms of the tribological aspects by using the monitoring system. Therefore, the removal mechanism of materials could be understood through the investigation of correlation between removal rate and coefficient of friction. In this study, a close examination between friction and CMP results was conducted. The results show that the material removal per unit sliding distance is proportional to friction force with regard to polishing performance. The friction energy affects removal rate and process temperature. Also, within wafer non–uniformity increases with the coefficient of friction, because operating location of normal resultant force on wafer shifts to its edge. Therefore the monitoring system will contribute to research and development of CMP process for fabrication of semiconductor device and silicon wafer.

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CMP技術の主な構成要素消耗品の中でも、パッドとコンデイショナーは均一な研磨特性を発揮する上で、特に重要な要素である。コンデイショナーの役割は、研磨工程中に発生する被研磨物の加工屑やパッドの削れ屑がパッド表面に堆積、付着し研磨性能の低下（グレージング）を防止することである。コンディショナーの欠点として、ダイヤモンド粒子の脱落、コンディショニング後のパッド表面の変化など研磨品質に悪影響を及ぼす課題がある。脱落したダイヤモンドは研磨工程においては巨大粒子であり、ウエハ表面のスクラッチ不良の原因になる。本研究は、特殊な溶解剤によりパッドの極表面を除去するメカニズムを用いて、コンデイショニング工程を排除したドレッシングレスCMPを検討する。特に、においてグレージングやパッドプロファイルの変化を考察する。

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研磨の特性に重要な相関関係にある摩擦力を同時測定して研磨中の動的な変化とその挙動を解析して各種パッドの摩擦特性を把握するsystemを構成し研究した。今回の研究はそのSystemの構成、測定data処理と解析法の提案と代表的な各種研磨Padの研磨中摩擦特性、このsystemの活用方案をその内容にする。

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研磨パッドの表面状態は、研磨性能に大きく影響する。特にパッドの立ち上げ時においては、パッドの表面状態が大きく変化するために、初期の研磨性能の安定化に対して様々な工夫が行われている。本報ではパッドの立ち上げ時における表面状態に着目し、解析を行った。

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シリコンウェハファイナル研磨工程ではファイナル研磨布の研磨装置への貼付け直後にダミーランと呼ばれる立上げ処理を行う。前記よりシリコンウェハ上の微小欠陥低減、砥粒残渣除去、Hazeと呼ばれる微小粗さ低減を達成する。しかし従来、立上げ評価は被研磨物のみで研磨布の動的変化を把握できなかった。本件は研磨初期の研磨布特性を捉える為、研磨時の研磨布-被研磨物間摩擦力より、研磨布物性と摩擦力の相関関係を検討した。

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This paper describes newly developed polishing pads for glass finishing that employs an epoxy resin instead of a conventional polyurethane resin. The porosity of the polishing pad was controlled by changing the amount of a chemical foaming agents mixed with a prepolymer epoxy resin. It was found that the removal rate of glass surface using epoxy polishing pad was approximately two times higher than those using urethane polishing pad, which means a 50 percent decrease in a usage of CeO₂ abrasives. The waviness and edge roll-off of polished glass surfaces were markedly improved by utilizing epoxy polishing pads, while the surface roughness of glass surfaces finished by epoxy pads was comparable to that finished by urethane pads. The investigation of substitute abrasive materials exhibited that the CeO₂ abrasives were completely substituted for ZrO₂ abrasives. The mechanism of higher removal rate of epoxy polishing pads was also investigated using measurement of contact angles, sliding angles and dynamic friction coefficient of polishing pads. These measurements indicate that abrasive grains are supported more strongly on the epoxy polishing pad than on the urethane polishing pad, namely, higher relative velocity between workpiece surface and abrasive grains to be obtained.

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