PLASMA PARAMETERS AND ACTIVE SPECIES KINETICS IN CF4+C4F8+Ar GAS MIXTURE

Abstract

This work discusses the relationships between the initial composition of the CF4 + C4F8 + Ar gas mixture, gas-phase characteristics and heterogeneous process kinetics under the condition of low-pressure inductively coupled plasma. The goals were to investigate how the CF4/C4F8 mixing ratio influences internal plasma parameters (electron temperature, electron density and ion bombardment energy) and kinetics of plasma active species as well as to analyze how the changes in above parameters may influence the dry etching characteristics, such as etching rates and selectivities. The investigation was carried out using the combination of plasma diagnostics by double Langmuir probes and 0-dimensional plasma modeling. Both experiments and calculations were carried out at constant gas pressure (10 mTorr), input power (800 W) and bias power (150 W) while the CF4/C4F8 mixing ratio was varied through the partial flow rates for corresponding gases. It was shown that the substitution of CF4 for C4F8 in the CF4+C4F8+Ar feed gas lowers F atom formation rates and causes the decreasing F atom flux to the treated surface due to decreasing their volume density. It was proposed that an increase in the densities and fluxes of unsaturated CFx (x=1,2) radicals toward C4F8-rich plasmas at the nearly constant ion energy flux (i.e. at the nearly constant efficiency of ion bombardment) causes a decrease in the effective reaction probability for F atoms through the increasing thickness of the fluorocarbon polymer film on the treated surface.Forcitation:Efremov A.M., Murin D.B., Kwon K.H. Plasma parameters and active species kinetics CF4+C4F8+Ar gas mixture. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N4-5. P. 31-36