Effect of slurry injection position on slurry mixing, friction, removal rate, and temperature in copper CMP

In this study, the extent of mixing of old and new slurry on the polishing pad is varied by the use of three different points of injection. Influences of the conditioner and bow wave on slurry mixing can be inferred from the experimental results, which include coefficient of friction data and pad and substrate thermal data. Results measured under identical lubrication mechanisms show that the slurry injection position can play a significant role in slurry mixing and slurry utilization efficiency. Slurry injection positions that induce lower slurry mixing are found to increase copper removal rate. Simulations of the bow wave and slurry puddle support the interpretation of the mixing phenomenon. This work underscores the importance of optimum slurry injection geometry and flow for obtaining a more cost effective and environmentally benign copper chemical mechanical polishing (CMP) process.