Electron dynamics in capacitively coupled argon plasmas with a structured cathode

Radio frequency capacitively coupled plasmas are used in the semiconductor industry for a wide range of applications, spanning from dielectric material deposition to reactive ion etching. Understanding the fundamentals of these plasmas will aid the design and improvement of next-generation reactors. In this paper, we use a combination of experimental techniques and computational simulations to examine low pressure (2.5 – 15 Pa), capacitively coupled argon plasmas that are powered by a variety of slotted cathodes. Phase-resolved optical emission spectroscopy (PROES) is used to measure argon excitation dynamics. We observe spatial and temporal oscillations of the excitation signal in the slotted electrode and the parallel region between the electrodes. These experimental data are used to validate two simulation models. The first is a hybrid plasma model with particle in cell electrons and fluid ions and neutrals. The second model treats all charged species kinetically using the particle in cell technique. Both models show good agreement with experimentally observed behaviors. This paper will first explain the physics behind the observed oscillatory argon excitation signals, followed by a comparison of the performance of the two simulation models.