EFFECTS OF SURFACE ZETA POTENTIAL ON THE FILTRATION BEHAVIOR OF COLLOIDAL ABRASIVES

In order to reduce scratches attributed to the CMP (chemical mechanical planarization) polishing processes, defect-causing large particle counts must be reduced to improve semiconductor yields. CMP slurry filtration is considered as a critical enabler of these yield improvements. As the process technology advances, the abrasive concentrations of CMP slurries will continue to be lowered while abrasive sizes will be smaller. To respond to such changes in slurry properties, it's imperative to reconsider slurry filtration strategies. With such changes in slurry properties, it's expected that the slurry abrasives will become less stable in the future. As many researchers have reported, proper slurry stability and their interactions with filtration media are very important for better particle removal in particle separation processes. In this study, we will investigate the effects of zeta potential of filtration media and abrasive particles on filtration performance under different conditions. We will compare the filtration performance when the zeta potential of the slurries is lower than, equal to, or higher than that of the filtration media. We will also compare filtration performance at the isoelectric point (I.E.P) of the slurry. At same time we will monitor LPC (liquid particle counts), PSD (particle size distribution), and idle effects under these conditions. We expect the results of this study to propose a filter selection index for advanced slurry applications.