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.
References
Makabe T., Petrovic Z. Plasma electronics: applications in microelectronic device fabrication. New York: Taylor & Francis. 2006. 330 p.
Rooth J.R. Industrial Plasma Engineering. Philadelphia: IOP Publishing LTD. 2001. 658 p.
Plasma Etching Processes for CMOS Devices Realization. London: ISTE Press – Elsevier. 2017. 125 p.
Wolf S., Tauber R.N. Silicon Processing for the VLSI Era. V. 1. Process Technology. New York: Lattice Press. 2000. 416 p.
Lieberman M.A., Lichtenberg A.J. Principles of plasma discharges and materials processing. New York: John Wiley & Sons Inc. 2005. 730 p.
Li X., Hua X., Ling L., Oehrlein G.S., Barela M., An-derson H.M. Fluorocarbon-based plasma etching of SiO2: Comparison of C4F6/Ar and C4F8/Ar discharges. J. Vac. Sci. Technol. A. 2002. V. 20. P. 2052-2061.
Matsui M., Tatsumi T., Sekine M. Relationship of etch reaction and reactive species flux in C4F8-Ar-O2 plasma for SiO2 selective etching over Si and Si3N4. J. Vac. Sci. Technol. A. 2001. V. 19. P. 2089-2096.
Standaert T.E.F.M., Hedlund C., Joseph E.A., Oehrlein G.S. Role of fluorocarbon film formation in the etching of silicon, silicon dioxide, silicon nitride, and amorphous hy-drogenated silicon carbide. J. Vac. Sci. Technol. A. 2004. V. 22. P. 53-60.
Son J., Efremov A., Yun S.J., Yeom G.Y., Kwon K.-H. Etching characteristics and mechanism of SiNx films for Nano-Devices in CH2F2/O2/Ar inductively coupled plasma: Effect of O2 mixing ratio. J. Nanosci. Nanotech. 2014. V. 14. P. 9534-9540.
Johnson E.O., Malter L. A floating double probe method for meas-urements in gas discharges. Phys. Rev. 1950. V. 80. P. 58-70.
Sugavara M. Plasma etching: Fundamentals and applica-tions. New York: Oxford University Press. 1998. 469 p.
Kwon K.-H., Efremov A., Kim M., Min N. K., Jeong J., Kim K. A model-based analysis of plasma parameters and composition in HBr/X (X=Ar, He, N2) inductively coupled plasmas. J. Electrochem. Soc. 2010. V. 157. P. H574-H579.
Efremov A., Min N.K., Choi B.G., Baek K.H., Kwon K.-H. Model-based analysis of plasma parameters and active species kinetics in Cl2/X (X=Ar, He, N2) inductively cou-pled plasmas. J. Electrochem. Soc. 2008. V. 155. P. D777-D782.
Lee J., Efremov A., Lee J., Yeom G.Y., Kwon K.-H. Silicon surface modification using C4F8+O2 plasma for nano-imprint lithography. J. Nanosci. Nanotech. 2015. V. 15. P. 8749-8755.
Chun I., Efremov A., Yeom G.Y., Kwon K.-H. A com-parative study of CF4/O2/Ar and C4F8/O2/Ar plasmas for dry etching applications. Thin Solid Films. 2015. V. 579. P. 136-143.
Kokkoris G., Goodyear A., Cooke M., Gogolides E. A global model for C4F8 plasmas coupling gas phase and wall surface reaction kinetics. J. Phys. D: Appl. Phys. 2008. V. 41. P. 195211-195222.
Rauf S., Ventzek P. L. G. Model for an inductively cou-pled Ar-C4F8 plasma discharge. J. Vac. Sci. Technol. A. 2002. V. 20. P. 14-23.
Lee J., Efremov A., Yeom G.Y., Lim N., Kwon K.-H. Application of Si and SiO2 etching mechanisms in CF4/C4F8/Ar inductively coupled plasmas for nanoscale patterns. J. Nanosci. Nanotech. 2015. V. 15. P. 8340-8347.
Tatsumi T., Hayashi H., Morishita S., Noda S., Okigawa M., Itabashi N., Nikisaka Y., Inoue M. Mechanism of radical control in capacitive RF plasma for ULSI pro-cessing. Jpn. J. Apl. Phys. 1998. V. 37. P. 2394-2405.
Efremov A.M., Kim D.-P., Kim C.-I. Simple model for ion-assisted etching using Cl2-Ar inductively coupled plasma: Effect of gas mixing ratio. IEEE Trans. Plasma Sci. 2004. V. 32. P. 1344-1351.
Lee J., Efremov A., Kwon K.-H. On the relationships between plasma chemistry, etching kinetics and etching residues in CF4+C4F8+Ar and CF4+CH2F2+Ar plasmas with various CF4/C4F8 and CF4/CH2F2 mixing ratios. Vacuum. 2018. V. 148. P. 214-223.
Gogolides E., Vauvert P., Kokkoris G., Turban G., Boudouvis A.G. Etching of SiO2 and Si in fluorocarbon plasmas: A detailed surface model accounting for etching and deposition. J. Phys. D: Appl. Phys. 2000. V. 88. P. 5570-5584.
Jin W., Vitale S.A., Sawin H.H. Plasma–surface kinetics and simulation of feature profile evolution in Cl2+HBr etching of polysilicon. J. Vac. Sci. Technol. A. 2002. V. 20. P. 2106-2115.
Li X., Ling L., Hua X., Fukasawa M., Oehrlein G.S., Barela M., Anderson H.M. Effects of Ar and O2 additives on SiO2 etching in C4F8-based plasmas. J. Vac. Sci. Tech-nol. A. 2003. V. 21. P. 284-295.
