Fluid simulation of species concentrations in capacitively coupled N2/Ar plasmas: Effect of gas proportion

Abstract

A two-dimensional self-consistent fluid model and the experimental diagnostic are employed to investigate the dependencies of species concentrations on the gas proportion in the capacitive N2/Ar discharges operated at 60 MHz, 50 Pa, and 140 W. The results indicate that the N2/Ar proportion has a considerable impact on the species densities. As the N2 fraction increases, the electron density, as well as the Ar+ and Arm densities, decreases remarkably. On the contrary, the N2+ density is demonstrated to increase monotonically with the N2 fraction. Moreover, the N density is observed to increase significantly with the N2 fraction at the N2 fractions below 40%, beyond which it decreases slightly. The electrons are primarily generated via the electron impact ionization of the feed gases. The electron impact ionization of Ar essentially determines the Ar+ density. For the N2+ production, the charge transition process between the Ar+ ions and the feed gas N2 dominates at low N2 fraction, while the electron impact ionization of N2 plays the more important role at high N2 fraction. At any gas mixtures, more than 60% Arm atoms are generated through the radiative decay process from Ar(4p). The dissociation of the feed gas N2 by the excited Ar atoms and by the electrons is responsible for the N formation at low N2 fraction and high N2 fraction, respectively. To validate the simulation results, the floating double probe and the optical emission spectroscopy are employed to measure the total positive ion density and the emission intensity originating from Ar(4p) transitions, respectively. The results from the simulation show a qualitative agreement with that from the experiment, which indicates the reliable model.

Control of charged particle dynamics in capacitively coupled plasmas driven by tailored voltage waveforms in mixtures of Ar and CF4

“…The influence of a chosen gas mixing ratio on discharge operation and process control is strongly correlated to the specific spatio-temporal dynamics dictated by the electron power absorption modes occurring in the plasma. The exact power absorption modes present in a discharge depend on the operating pressure, the characteristics of the driving voltage waveform [20, 31-39, 42-44, 46, 61-69, 71-75, 84-99], and the mixing ratio between gas components [57][58][59][100][101][102][103]. Therefore, in this work we present a systematic investigation of the electron power absorption dynamics and the EAE in CCPs driven by tailored voltage waveforms at different pressures as a function of the Ar-to-CF 4 gas mixing ratio, which determines the discharge electronegativity.…”

Importance of Dielectric Elements for Attaining Process Uniformity in Capacitively Coupled Plasma Deposition Reactors

“…Despite various efforts, technically complex issues such as the electron heating mechanism and the plasma distribution control have not been sufficiently resolved in the coating process using the capacitively coupled plasma (CCP) deposition reactors [1,2]. However, CCP deposition reactors have been widely adopted in the current semiconductor industry [3].…”