Real-Time Endpoint Detection of Small Exposed Area SiO₂ Films in Plasma Etching Using Plasma Impedance Monitoring with Modified Principal Component Analysis

Abstract

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.