Stable plasma ignition of remote plasma sources (RPSs) for various plasma processes is essential to ensure the stability of the discharge, steady operating conditions, and high plasma density. In an RPS in which the gas pressure exceeds 1 Torr, the reaction paths leading to the high-level excited state play an essential role in the power balance and energy cascade at high applied input power. In this study, 97 chemical reactions in a detailed reaction set involving argon discharge are investigated in the steady-state to understand the extent to which the dominant reactions are affected by variations in the process parameters. We observed that the stepwise ionization process of the argon 4p excited state significantly contributes to sustaining high-density plasmas in the near 1 Torr regime.

This study investigates, numerically, the spatial distribution of metastable helium (He*) in He/SiH4 capacitively coupled plasma (CCP) for the purpose of optimizing plasma density distributions. As a first step, we presented the results of a two-dimensional fluid model of He discharges, followed by those of He/SiH4 discharges to deposit hydrogenated amorphous silicon films, to investigate which factor dominates the coating uniformity. We retained our CCPs in the 300 mm wafer reactor used by the semiconductor industry in the recent past. Selected parameters, such as a sidewall gap (radial distance between the electrode edge and the sidewall), electrical condition of the sidewall, and position of the powered electrode, were considered. In addition, by increasing the gas pressure while varying the sidewall condition, we observed modification of the plasma distributions and, thus, the deposition rate profiles. According to the results, the shift in He* distributions was mainly due to the reduction in the electron mean free path under conditions of gas pressure higher than 100 Pa, as well as local perturbations in the ambipolar electric field due to the finite electrode structure. Small additions of SiH4 largely changed the He* density profile in the midplane of the discharge due to He* quenching. Furthermore, we found that the wide sidewall gap did not improve deposition uniformity against the expectation. This was because the excitation and ionization rate profiles were enhanced and localized only near the bottom electrode edge.

Inside Front Cover: For a wide range of plasma processes, stable plasma ignition of remote plasma sources (RPSs) is essential to ensure the stability of the discharge, stable operating conditions, and high plasma density. An RPS operating at a gas pressure greater than 1 Torr relies on the reaction pathways leading to the high‐level excited state to sustain the power balance and energy cascade at a high input power level. Further details can be found in the article by Cheongbin Cheon, Jung Hwan Yoon, Sanghyun Jo, Ho Jun Kim, and Hae June Lee (https://doi.org/10.1002/ppap.202100251).