A.M. Efremov

Inductively coupled Cl2/Ar plasma: Experimental investigation and modeling

Electrophysical and kinetic characteristics of Cl2/Ar plasma were investigated to understand the influence of the addition of Ar on the volume densities and fluxes of active particles, both neutral and charged. Our analysis combined 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 an increase of the electron mean energy due to the “transparency” effect. Direct electron impact dissociation of Cl2 molecules represents the main source of chlorine atoms in the 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 a decrease in the total ionization rate and the acceleration of heterogeneous decay of charged particles.

Etching mechanism of MgO thin films in inductively coupled Cl2∕Ar plasma

The etching mechanism of MgO thin films in Cl2∕Ar plasma was investigated. It was found that the increasing Ar in the mixing ratio of Cl2∕Ar plasma causes nonmonotonic MgO etch rate, which reaches a maximum value at 70%Ar+30%Cl2. Langmuir probe measurement showed the noticeable influence of Cl2∕Ar mixing ratio on electron temperature and electron density. The zero-dimensional plasma model indicated monotonic changes of both densities and fluxes of active species. At the same time, analyses of surface kinetics showed the possibility of nonmonotonic etch rate behavior due to the concurrence of physical and chemical pathways in ion-assisted chemical reaction.

Volume and heterogeneous chemistry of active species in chlorine plasma

Abstract Chlorine plasma parameters and the mechanisms of both volume and heterogeneous reactions were investigated using a combination of experimental methods and plasma modeling. It was found that increasing gas pressure within the range 20–200 Pa leads to sufficient deformation of the electron energy distribution function and to corresponding changes in kinetic and transport coefficients. Direct electron impact dissociation and ionization were found to be the main mechanisms for radical and ion generation, while contributions from dissociative attachment and dissociative ionization were negligible. Heterogeneous recombination of chlorine atoms is the dominant decay channel, which is described by a first-order kinetic mechanism.

On mechanisms of argon addition influence on etching rate in chlorine plasma

Abstract Parameters of Cl 2 /Ar plasma were investigated aimed to understand the mechanism of Ar addition influence on etching rate acceleration. Analysis was carried out on the base of combination of experimental methods and plasma modelling. It was found that the addition of Ar to chlorine under a constant total pressure condition cause changes in plasma electro-physical properties (EEDF, mean electron energy) due to the ‘transparency’ effect. Direct electron impact dissociation of Cl 2 molecules was found as the main source of chlorine atoms while the contributions of dissociative attachment and stepwise dissociation involving Ar metastable atoms are negligible. It was supposed that the main reason of etching rate increasing in Cl 2 /Ar mixture plasma is connected with simultaneous action of Ar on volume chemistry and the heterogeneous stage of etching process.

Investigation of SrBi2Ta2O9 thin films etching mechanisms in Cl2 /Ar plasma

An investigation of the SrBi2Ta2O9 (SBT) etching mechanism in a Cl2/Ar plasma was carried out. Experiments showed that an increase of the Ar mixing ratio under constant pressure and input power conditions leads to increasing an etch rate of SBT, which reaches a maximum value when the Ar is 80% of the gas. The modeling of volume kinetics using the measured electron temperature and electron density indicated monotonic changes of both densities and fluxes of active species such as chlorine atoms and positive ions. Nevertheless, an analysis of surface kinetics in the framework of an ion-assisted etching mechanism confirms the possibility of nonmonotonic etch rate behavior due to the concurrence of physical sputtering and chemical etching activated by ion bombardment.An investigation of the SrBi2Ta2O9 (SBT) etching mechanism in a Cl2/Ar plasma was carried out. Experiments showed that an increase of the Ar mixing ratio under constant pressure and input power conditions leads to increasing an etch rate of SBT, which reaches a maximum value when the Ar is 80% of the gas. The modeling of volume kinetics using the measured electron temperature and electron density indicated monotonic changes of both densities and fluxes of active species such as chlorine atoms and positive ions. Nevertheless, an analysis of surface kinetics in the framework of an ion-assisted etching mechanism confirms the possibility of nonmonotonic etch rate behavior due to the concurrence of physical sputtering and chemical etching activated by ion bombardment.

Etching mechanism of Bi4−xLaxTi3O12 films in Ar/Cl2 inductively coupled plasma

The etching behavior of Bi4−xLaxTi3O12 (BLT) films in inductively coupled Ar/Cl2 plasma was investigated in terms of etch parameters. The etching rate as a function of Ar/Cl2 mixing ratio showed a maximum of 50.3 nm/min for the mixture of Ar(80%)/Cl2(20%). The increase of r.f. power and d.c.-bias voltage caused an increase in BLT etch rate under any fixed gas composition. To understand etch mechanism, the plasma diagnostics were performed using Langmuir probe (LP) and optical emission spectroscopy (OES). The LP measurement indicated that the increase of Ar mixing ratio in Ar/Cl2 plasma leads to monotonic changes of both electron density and total density of positive ions. The same tendencies were found for chlorine atoms and molecules using OES. The chemical states of BLT were studied using X-ray photoelectron spectroscopy (XPS). XPS narrow scan analysis shows that the La-chlorides remained on the etched surface. The analysis of surface reactions and plasma diagnostics in the frameworks of an ion-assisted etching mechanism confirms the possibility of non-monotonic etch rate behavior due to the concurrence of physical sputtering and chemical etching activated by ion bombardment.

Etching characteristics and mechanism of Au thin films in inductively coupled Cl2/Ar plasma

The etching characteristics and physical/chemical mechanisms of Au thin films in Cl 2 /Ar plasma were investigated. It was found that an increase of the Ar content in Cl 2 /Ar plasma under constant pressure and input power conditions leads to an increasing etch rate of Au, which reaches a maximum value at 80%Ar/20%Cl 2 . X-ray photoelectron spectroscopy of the etched surfaces indicated the accumulation of reaction products in a chlorine-rich plasma. A proposed zero-dimensional model of volume kinetics, which involved the Langmuir probe data for electron temperature and electron density, showed monotonic change of both densities and fluxes of active species such as chlorine atoms and positive ions. In contrast, analyses of surface kinetics showed the possibility of nonmonotonic etch rate behavior due to the concurrence of physical and chemical factors in ion-assisted chemical reaction.