Real-Time Endpoint Detection for SiO$_{2}$ Film Plasma Etching Using Impedance Analysis with Modified Principal Component Analysis

Plasma etching is used in various semiconductor processing steps. Commonly, optical emission spectroscopy is widely used for real-time endpoint detection for plasma etching, In this research, the object is to investigate the suitability of using impedance analysis for real-time endpoint detection. The endpoint were determined by impedance measurement and an equivalent circuit model. Especially, third harmonic changed sharply at the endpoint when SiO$_{2}$ film on Si wafer is etched by CF$_{4}$ plasma on capacitive coupled plasma. And modified principal component analysis (PCA) is applied to them for increasing sensitivity. For verifying this method, detected endpoint from impedance analysis is compared with optical emission spectroscopy and ion current probe, From impedance data, we tried to analyze physical properties of plasma, and real-time endpoint detection can be achieved. This method can be applied to the other fault detections.