Experimental Validation of Particle-in-Cell/Monte Carlo Collision simulation coupled with Collisional Radiative Model by Optical Emission Spectroscopy*

Capacitively-coupled radio-frequency (RF) Ar plasma experiments with optical emission spectroscopy (OES) measurements were used to validate a 1D Particle-in-Cell/Monte Carlo Collision (PIC/MCC) simulation code with a Collisional Radiative Model (CRM). The CRM based on the first 14 levels of argon provided the line intensities using the electron energy distribution function (EEDF) obtained from the PIC/MCC simulation. The experiments were performed in a plasma source with symmetric parallel-plate stainless steel electrodes having a gap distance of 4 cm and a radius of 7.1 cm enclosed inside a cylindrical quartz chamber wall. The peak-to-peak voltage applied to the powered electrode ranged between 200 and 500 V, and the gas pressure varied from 1.5 to 120 Pa. OES spectra were acquired from the central region of the plasma. The validity of the simulation model was tested by comparing the electrical current (EC) and spectral line intensities obtained from both experiments and simulations. The resulting OES and EC comparison showed good agreement between the measurements and calculations in general. Moreover, the line intensities were found to be highly sensitive to changes in the EEDF. The extent of the agreement between the experiment and simulation corroborated with the nonintrusive OES and EC measurements gives us a well-defined level of confidence in using the simulation as a virtual metrology tool to predict plasma parameters that are usually difficult or even impossible to be obtained experimentally.