Monitoring O₂ Plasma Parameters with a Single Langmuir Probe and OES in a 6-Inch ICP Etcher

Maintaining etch uniformity from the center to the edge of the wafer during the etching process is a critical challenge. In particular, the edge of the wafer poses difficulties due to changes in the angle of ion incidence caused by the curvature of the sheath, making it challenging to achieve the desired etch pattern. Therefore, identifying and monitoring key factors that significantly impact center-to-edge uniformity is essential. In this paper, plasma diagnostics were conducted using Optical Emission Spectroscopy (OES), an optical diagnostic method, to analyze the bulk plasma, while the traditional diagnostic method of the Single Langmuir Probe was used to measure plasma parameters. OES was employed to monitor changes in the bulk plasma, and the Single Langmuir Probe was used to monitor plasma parameters such as electron density and electron temperature at different radial positions. Experiments were conducted in a 6-inch ICP-type etcher, with the top power varied from 150 to 250 W in increments of 25 W, using O₂ at a flow rate of 20 SCCM.