Plasma Process Uniformity Diagnosis Technique Using Optical Emission Spectroscopy With Spatially Resolved Ring Lens

A novel method to measure the positional plasma intensity, which indicates the uniformity of plasma processes, using optical emission spectroscopy (OES) with a spatially resolved ring lens (SRRL) is proposed. OES offers a noncontact and nondestructive plasma diagnostic tool and is easily implemented. Despite these advantages, the light intensities in local regions are difficult to measure by the principle of superposition of light. In this study, by blocking the light passage through the center of the SRRL, the intensity of the plasma light as a function of the distance in the process chamber is measured precisely. This methodology improves the distortion of the near light source and measures the local light intensities. Thus, it can be used to obtain the plasma distribution in a process chamber and thereby assess the uniformity of the plasma process.