Development of a Novel Nanodiamond-Impregnated Polishing Pad for Chemical Mechanical Polishing of Oxide Film

Abstract

This study is aimed at fabricating a chemical mechanical planarization or polishing (CMP) pad by impregnating a polyurethane matrix with hydrogenated nanodiamond (5-10nm) and graphite particles. Two types of pads-one containing 0.1wt% nanodiamond with 3wt% graphite and the other comprising 1wt% nanodiamond with 3wt% graphite-were fabricated and their performances were compared with that of a polyurethane polishing pad. Hydrogenated nanodiamond particles used in this study were obtained by heat-treating graphite particles under a layer of hydrogen ions, which enables their uniform dispersion in the polyurethane matrix. The surface characteristics and contact angle of the nanodiamond-impregnated pads, as well as the removal rate of a dielectric oxide film polished with these pads, were investigated and compared with the corresponding attributes shown by a polyurethane polishing pad. The results of this study confirmed that the nanodiamond-impregnated polishing pads showed the smallest contact angle for the slurry, indicating that their ability to retain the slurry was better than that of a polyurethane polishing pad. Hence, the site to be polished was better lubricated by increasing its wetting, which led to a faster polishing of the wafer without damaging the local circuitry by the nanodiamond-impregnated pads. Thus, oxide CMP tests proved that these novel polishing pads provided a better wafer removal rate.本研究旨在研究如何使用聚氨酯基質含浸氫化奈米鑽石（5-10nm）和石墨顆粒製造化學機械拋光（CMP），亦稱平坦化，所需之拋光墊。可製造出兩種不同比例成份之拋光墊，一種含0.1wt%的奈米鑽石和3wt%的石墨，另一種含1wt%的奈米鑽石和3wt%的石墨，其特性跟聚氨酯拋光墊相當。本研究使用的氫化奈米鑽石顆粒是藉由一層氫離子進行石墨顆粒的加熱處理而取得，使其在聚氨酯基質中可均勻分散。本研究亦探討奈米鑽石含浸墊的表面特性和接觸角度，以及使用這些墊拋光後對介電質氧化層的移除率，並與聚氨酯拋光墊的相關特性進行比較。本研究的結果確認奈米鑽石含浸拋光墊跟漿料出現最小的接觸角，即表示此材料保有漿料的能力較聚氨酯拋光墊更佳。因此，要拋光的部位最好加溼潤滑，可使用奈米鑽石含浸墊促成晶圓進行更快速的拋光而不損及局部的電路。因此，經實際測試拋光氧化層矽晶圓後證明新發明的拋光墊能讓晶圓具有更佳的移除率。