Real-time characteristic impedance monitoring for end-point and anomaly detection in the plasma etching process

摘要

We propose a practical and highly sensitive characteristic impedance monitoring (CIM) system for detecting the etching end point and anomalies during the plasma etching process. The CIM system employs a directional coupler and a newly developed vector processing system. The etching end point was successfully detected when a SiO_2/Si wafer was etched with CF_4 plasma; the system also detected wafer fluttering occurring during SF_6-N_2 plasma etching. The reactance component of the characteristic impedance primarily changed with the transient response of the electric potential on the inner glass surface during SF_6-N_2 plasma etching.