Real-time endpoint detection of small exposed area SiO₂ films in plasma etching using plasma impedance monitoring with modified principal component analysis

Endpoint detection (EPD) with plasma impedance monitoring (PIM) is demonstrated for small area SiO₂ RF plasma etching. The endpoint is determined by the impedance harmonic signals variation from the I-V monitoring system. Moreover, modified principal component analysis (mPCA) is applied to enhance the sensitivity for real-time small area SiO₂ etching. For verification, the detected endpoint by PIM is compared with optical emission spectroscopy (OES) signals. The results indicate that PIM shows better sensitivity than OES, and the sensitivity of EPD is enhanced by a factor of 2.03 with the mPCA algorithm. EPD of 0.5% SiO₂ area etching is successfully demonstrated with PIM and mPCA. This technique can be applied to plasma etching processes as a sensitive process monitoring tool. The goal of this research is to enhance detection limit of etching endpoint. The endpoint is determined by impedance signals from RF I-V monitoring system. Voltage, current, and phase harmonics are gathered, and modified principal component analysis is applied to enhance sensitivity for real-time small area SiO ₂ etching. Optical emission spectroscopy (OES) is usually used to detect endpoint; the new method that is introduced in this paper is verified by OES.