Effect of Pad Micro-Texture on Frictional Force, Removal Rate, and Wafer Topography during Copper CMP Process

In this study, the effect of pad micro-texture on frictional force, removal rate, and wafer topography during copper CMP process was investigated. 200-mm blanket copper wafers and Sematech854 patterned wafers were polished and pad samples were taken after wafer polishing. Pad contact area and surface topography were analyzed using a laser confocal microscope. The Mitsubishi Materials Corporation (MMC) 100-grit TRD disc generated much larger flat near contact areas that corresponded to conditioning debris and fractured/collapsed pore walls. The conditioning debris and fractured/collapsed pore walls partly covered the adjacent pores, making the pad surface more lubricated and rendering a lower coefficient of friction and removal rate compared with the 3M A2810 disc. The mean summit curvature generated by the MMC disc was larger than the 3M disc during patterned wafer polishing, indicating sharper pad summits contributed to higher dishing for the MMC disc.