Acoustic emission (AE) is used as a technique to monitor and characterize surface interactions between wafer and pad in a chemical-mechanical planarization (CMP) process for copper. A significant variation in in-situ AE signal was observed during controlled variation of the slurry composition, demonstrating the sensitivity of AE to the unique surface reactions taking place. Two different levels of AE were observed; a high root-mean-square (RMS) signal when polishing H2O2 treated copper, and a low RMS signal when polishing bare copper. The rate of change in the AE signal was also tied to variations in species concentration and pH in slurry.

Chemical mechanical planarization (CMP) of Cu interconnects is a critical bottleneck technology for semiconductor manufacturing at the 65 nm technology node and beyond. The pad condition in CMP is of utmost importance in maintaining acceptable production quality and throughput, as it directly affects many different parameters in CMP including material removal rate (MRR) and process uniformity. Acoustic emission (AE) is a proven technique for in-situ monitoring of a wide range of manufacturing processes, and has been demonstrated for the in-situ monitoring of various phenomena in the CMP process such as endpoint and MRR detection. A novel graphical mapping approach of sensor signal for monitoring pad condition during Cu CMP is proposed and tested, with AE demonstrating improved sensitivity over that of friction force.