PLASMA PARAMETERS, DENSITIES OF ACTIVE SPECIES AND ETCHING KINETICS IN C4F8+Ar GAS MIXTURE

Abstract

In this work, we performed the combined (experimental and model-based) study of gas-phase plasma characteristics and etching kinetics for both Si and SiO2 in the C4F8 + Ar gas mixture. The experiments were carried out at constant total gas pressure (p = 6 mTorr), input power (W = 900 W) and bias power (Wdc = 200 W) while the C4F8/Ar mixing ratio was varied in the range of 0–75% Ar. The data on internal plasma parameters, plasma chemistry as well as the steady-state plasma composition were obtained by both Langmuir probe diagnostics and 0-dimensional plasma modeling. The etching mechanisms were investigated through the analysis of relationships between the measured etching rates and the model-predicted fluxes of active species (F atoms, polymerizing CFx radicals and positive ions). It was found that, under the given set of experimental conditions, the Si and SiO2 etching process 1) appears in the steady-state etching regime; 2) exhibits the features of the ion-assisted chemical reactions in the neutral-flux-limited mode; and 3) is influenced by the fluorocarbon polymer film thickness. It was shown that the influence of input process parameters on the effective probability of chemical reaction between Si, SiO2 and fluorine atoms may be adequately characterized by the fluorocarbon radicals/fluorine atoms and fluorocarbon radicals/ion energy flux ratios.

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:…”

“…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. As such, the change in the effective probability of ion-assisted chemical reaction represents the superposition of all above effects [11,12].…”

PLASMA PARAMETERS AND ACTIVE SPECIES KINETICS IN Cl2 + BCl3 + Ar GAS MIXTURE

“…Together with increasing effective ion molar mass Mi, this overcompensates the decreasing tendency for + and produces a growth of the parameter (Mii) 1/2 + (Fig. 3(d)) characterizing the ion bombardment intensity [5,[9][10][11]19]. An increase in input power causes either the weak growth (in the case of Cl2-rich plasma) or the weak fall (in the case of BCl3-rich plasma) of (Mii) 1/2 + values.…”