The effects of both CF4/O2 and O2/Ar mixing ratios in three-component CF4/O2/Ar mixture on plasma parameters, densities and fluxes of active species determining the dry etching kinetics were analyzed. The investigation combined plasma diagnostics by Langmuir probes and zero-dimensional plasma modeling. It was found that the substitution of CF4 for O2 at constant fraction of Ar in a feed gas produces the non-monotonic change in F atom density, as it was repeatedly reported for the binary CF4/O2 gas mixtures. At the same time, the substitution of Ar for O2 at constant fraction of CF4 results in the monotonic increase in F atom density toward more oxygenated plasmas. The natures of these phenomena as well as theirs possible impacts on the etching/polymerization kinetics were discussed in details.
The influence of O2/Ar mixing ratio on plasma characteristics, densities and fluxes of active species determining the dry etching kinetics in both CF4/O2/Ar and CHF3/O2/Ar plasmas was studied. The investigation combined plasma diagnostics by Langmuir probes and zero-dimensional plasma modeling. It was found that the substitution of O2 for Ar at constant fraction of CF4 or CHF3 in a feed gas noticeably changes electron temperature and electron density, but does not result in the non-monotonic behavior of F atom density. The differences between two gas systems were discussed in details from the point of view of plasma chemistry.
The direct current (dc) glow discharge plasma parameters and active species kinetics in HCl-X (X = Ar, N2, H2, Cl2, O2) mixtures were studied using both plasma diagnostics Langmuir probes and modeling. The 0-dimensional self-consistent steady-state model included the simultaneous solution of Boltzmann kinetic equation, the equations of chemical kinetics for neutral and charge particles, plasma conductivity equation and the quasi-neutrality conditions for volume densities of charged particles as well as for their fluxes to the reactor walls. The data on the steady-state electron energy distribution function, electron gas characteristics (mean energy, drift rate and transport coefficients), volume-averaged densities of plasma active species and their fluxed to the reactor walls were obtained as functions of gas mixing ratios and gas pressure at fixed discharge current.
An investigation of a VO2 etch mechanism in Cl2/Ar inductively coupled plasma under the condition of low ion bombardment energy is carried out. It is found that an increase in Ar mixing ratio results a nonmonotonic VO2 etch rate, which reaches a maximum of 70 to 80 nm/min at 70 to 75% Ar. The model-based analysis of the etch mechanism shows that the VO2 etch kinetics correspond to the ion-flux-limited etch regime. This is most likely due to the domination of low volatile VCl3 and/or VCl2 in the reaction products.
In this work, the investigations of plasma parameters and active particles kinetics in an HCl dc glow discharge were carried out using the combination of plasma diagnostics and plasma modeling. The modeling was based on the self-consistent solution of Boltzmann kinetic equation and the balance equation of chemical kinetic for neutral and charged particles. It was shown that the electron impact dissociation of HCl is the main source of both Cl and H atoms while the total balances for all kinds of neutral particles are noticeably influenced by the volume atom-molecular reactions. The population of the vibrational energy levels for HCl molecules was found to be low, but the role of the HClv>0 in the negative ions formation process cannot be neglected. The assumption of the first-order heterogeneous recombination kinetics for both Cl and H species provides a good agreement between the modeling and plasma diagnostics data.
Plasma parameters and chemical kinetics of Cl2/Ar plasma were investigated aimed at understanding the mechanism of Ar addition on mass composition of charged and neutral particles. The analysis was based on both experimental methods and plasma modeling. It was found that addition of Ar to Cl2 leads to deformation of the electron energy distribution function and to increase of the electron mean energy. Direct electron impact dissociation of Cl2 molecules represents the main source of chlorine atoms in plasma volume. The contributions of stepwise dissociation and ionization involving Ar metastable atoms were found to be negligible. Addition of Ar to Cl2 causes the decrease of both electron and ion densities due to the decrease of the total ionization rate and the acceleration of heterogeneous decay of charged particles.
In this work, we investigated both etching characteristics and mechanisms of Au thin films using Cl2/Ar gas mixture in an inductively coupled plasma (ICP) system. For these purposes, a combination of experimental methods and modeling was used. It was found that an increase in Ar mixing ratio under constant operating conditions causes non-monotonic behavior of Au etch rate, which reaches a maximum 80% Ar. A study of surface composition using X-ray photoelectron spectroscopy (XPS) showed that the etching in chlorine-rich plasma is escorted by accumulation of AuClx on the etched surfaces. Langmuir probe measurements indicated a noticeable sensitivity of both electron temperature and electron density to the change of Ar mixing ratio while 0-dimensional model of volume kinetics showed monotonic change of both densities and fluxes of active species such as chlorine atoms and positive ions. However, analyses of surface kinetics showed that the non-monotonic etch rate behavior may be produced by the concurrence of physical and chemical pathways in ion-assisted chemical reaction.