Diffusion-Limited Agglomeration and Defect Generation during Chemical Mechanical Planarization

Chemical mechanical planarization ͑CMP͒ of copper involves removal of surface asperities with abrasive particles and polishing processes.This leads to copper-containing nanoparticles extruded into the solution.We model the diffusion-limited agglomeration ͑DLA͒ of such nanoparticles which can rapidly grow to large sizes.These large particles are detrimental because they can participate in polishing, causing scratches and surface defects during CMP.The agglomeration is much slower in the reactionlimited agglomeration process.Under realistic conditions the defect generation probability can increase significantly over time scales of ϳ10 to 20 min from DLA, unless prevented by slurry rejuvenation or process modification measures.