Signal Analysis of CMP Process based on AE Monitoring System

As chemical mechanical planarization (CMP) enables local and global planarization over a wafer surface by the combined effects of chemical and mechanical interactions, process monitoring is becoming an increasingly important in-situ methodology for process control. According to the materials and process, signal characteristics were distinguishable between material and process. In this study, an acoustic emission (AE) sensor was used to measure the abrasive and molecular-scale phenomena during CMP An AE signal was acquired using rotational equipment and adapted to two types of equipment. First, a wireless AE system consisting of wireless modules using Bluetooth was used. This system was suitable for acquiring signals in rotational equipment. However, a wireless AE system could be acquired with only Root Mean Square(RMS) signals. Second, mercury slip-ring (wired) AE systems that were suitable for rotational equipment and the acquisition of raw signals were used The acquired raw signals could be analyzed by a Fast Fourier Transform (FFT) for abrasive and molecular-level phenomena in the CMP process. The AE signal parameters including the AE RMS, frequency, and amplitude were analyzed for abrasive and molecular-level phenomena in the CMP process. The authors analyzed the AE signals for changes in the materials and CMP process.