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

PLASMA COMPOSITION AND SiO2 ETCHING KINETICS IN CF4/C4F8/Ar/He MIXTURE: EFFECTS OF CF4/C4F8 MIXING RATIO AND BIAS POWER

“…1) Similarly to conventional RIE conditions [10,11], an increase in CF4 fraction in a feed gas causes rather weak changes in both electron temperature (Fig. 1(a)) and ion current density (Fig.…”

“…Experiments were carried out in the inductively coupled plasma (ICP) reactor known from our previous works [10][11][12][13]. Plasma was excited using the 13.56 MHz power supply connected to the flat copper coil on the top side of reactor chamber.…”

“…1 represents effects of CF4/C4F8 mixing ratio and bias power on electrons-and ions-related gas-phase characteristics. The analysis of these data with accounting for the previous research experience of CF4 + Ar [9,13], C4F8 + Ar [9][10][11]13] and CF4 + + C4F8 + Ar [10][11][12] plasmas allows one to formulate several important features which may be useful for the optimization of corresponding RIE process. These are as follows:…”

“…The reason is that the variation of gas mixing ratio offers the additional tool to optimize output RIE characteristics through changes in both gas-phase and heterogeneous reaction kinetics. In our previous works [9][10][11][12][13], we carried out detailed investigations of gas mixing effects in binary and ternary gas systems composed by CF4, C4F8 and Ar under conventional RIE conditions (gas pressures below 50 mtorr, input power densities of 0.5-0.1 W/cm 3 that correspond to the plasma density of  10 10 -10 11 cm -3 , and ion bombardment energies above 1) An increase in Ar fraction in both CF4 +Ar and C4F8 + Ar plasmas changes electrons-and ionsrelated plasma parameters and thus, influences both gas-phase and heterogeneous reaction kinetics. Most principal effect here are a) the elevation of electron temperature and plasma density; b) the increasing efficiency of electron-impact processes that results in slower decrease of F atoms density [9,10]; and c) the growth of ion bombardment intensity that accelerates ion-driven heterogeneous processes, such as surface bond breaking, the desorption of low volatile reaction products and the destruction of fluorocarbon polymer film.…”

“…Most principal effect here are a) the elevation of electron temperature and plasma density; b) the increasing efficiency of electron-impact processes that results in slower decrease of F atoms density [9,10]; and c) the growth of ion bombardment intensity that accelerates ion-driven heterogeneous processes, such as surface bond breaking, the desorption of low volatile reaction products and the destruction of fluorocarbon polymer film. As such, the change in the effective probability of ion-assisted chemical reaction represents the superposition of all above effects [11,12].…”