On the Etching Characteristics and Mechanisms of HfO<SUB>2</SUB> Thin Films in CF<SUB>4</SUB>/O<SUB>2</SUB>/Ar and CHF<SUB>3</SUB>/O<SUB>2</SUB>/Ar Plasma for Nano-Devices

Abstract

The study of etching characteristics and mechanisms for HfO2 and Si in CF4/O2/Ar and CHF3/O2/Ar inductively-coupled plasmas was carried out. The etching rates of HfO2 thin films as well as the HfO2/Si etching selectivities were measured as functions of Ar content in a feed gas (0-50% Ar) at fixed fluorocarbon gas content (50%), gas pressure (6 mTorr), input power (700 W), bias power (200 W), and total gas flow rate (40 sccm). Plasma parameters as well as the differences in plasma chemistries for CF4- and CHF3-based plasmas were analyzed using Langmuir probe diagnostics and 0-dimensional plasma modeling. It was found that, in both gas systems, the non-monotonic (with a maximum at about 15-20% Ar) HfO2 etching rate does not correlate with monotonic changes of F atom flux and ion energy flux. It was proposed that, under the given set of experimental conditions, the HfO2 etching process is affected by the factors determining the formation and decomposition kinetics of the fluorocarbon polymer layer. These factor are the fluxes of CF(x) (x = 1, 2) radicals, O atoms and H atoms.

PLASMA PARAMETERS AND COMPOSITION IN CF4/O2/Ar GAS MIXTURE

“…Similarly, to our previous works [10,11,14,15], the model was based on the Maxwellian electron energy distribution function (EEDF), and directly used the experimental data of Т е and n + as input parameters. Though the real EEDFs are not exactly Maxwellian, such a simplification for CF 4 -based and lowpressure (p < 50 mTorr) ICPs provides reasonable agreement between the diagnostic results and modeling [10-12, 16, 27].…”

“…The general model assumptions as well as the reaction scheme were the same with our previous works [14,15]. The rate coefficients for electron impact reactions were calculated as functions of Те using the fitting expressions in a form of k = AT e B exp(-C/T e ) [5,14].…”

“…The rate coefficients for electron impact reactions were calculated as functions of Те using the fitting expressions in a form of k = AT e B exp(-C/T e ) [5,14]. The heterogeneous chemistry of atoms (F, C, O) and radicals (CF 3 , CF 2 , CF) was described in terms of the conventional first-order recombination kinetics.…”

“…The heterogeneous chemistry of atoms (F, C, O) and radicals (CF 3 , CF 2 , CF) was described in terms of the conventional first-order recombination kinetics. The corresponding ticking probabilities were obtained from Refs [5,14,15]. The electron density (n e ) was calculated using the simultaneous solution of the steady-state chemical kinetic equation for negative ions ν da n e ≈ k ii n + n -and the quasi-neutrality equation n + = n e +n -.…”

CF4 Adsorption on Microporous Carbons Prepared by Carbonization of Poly(vinylidene fluoride)

“…9 Generally, CF 4 is used for dry etching processes in the semiconductor industry and for chemical vapor decomposition processes in aluminum production. 10,11 Thus, the demand for CF 4 as an electronic gas has continued to increase due to the rapidly growing semiconductor market, which makes an increase in CF 4 emission inevitable. 12 In order to mitigate the effect of CF 4 on global warming, appropriate steps must be taken for its capture and removal.…”