ИСТИНА

Modern plasma processing techniques, especially atomic layer etching, require precise control of different plasma parameters. The resent studies of widely used low-k materials show great sensitivity of these materials to the VUV emission from the plasma. VUV photons from the discharge can substantially damage the properties of the processing materials. In this sense the simulation of plasma processing discharges should correctly predict the VUV fluxes from the plasma. Also material modification on the atomic layer scale requires precise control of the ion flux and ion energy distribution function (IEDF) at the electrode. In the first part of this work we study the usage of collision-radiative models in PIC MCC simulation of CCP discharge. In the second part the ion fluxes and IEDFs are investigated. We study different sets of Ar excited states included in the model: from the simple one with the total description of metastable and resonance states [1], to the more detailed scheme with four lower levels and two effective higher levels [2] and to the detailed scheme in [3] with the 14 levels (4 lower 1s- states and 10 2p- states) and different transitions between these states. The experimental results from [4] for Ar(1s) densities was used to verify the PIC MCC calculations. The reduced sets of Ar excited states, which give the necessary information about concentration of metastable and radiative states, but not complicate too much the PIC simulation are presented. The self-consisted simulation of the discharge allows obtaining the electron energy distribution function (EEDF) without additional assumptions. However dealing with experimental data from the different discharge configurations, some additional effects should be taken into account that can change the EEDF shape and electron heating. These are edge electrostatic effect and electromagnetic effects. IEDF and ion flux values are crucial for selective surface modification. To estimate the ion flux value from the bulk plasma density one need the correct value of the k - plasma density reduction in the presheath area. Pulsed selfbias method was used as the reliable method for ion flux measurement and experimental estimation of the k value. PIC MCC simulation was done to provide the approximation of the k value as a function of pressure for the given ion composition. The semianalytical approach of ion spectrum calculation at an rf-biased electrode in asymmetric DF CCP discharge is presented. It is based on the experimentally measured sheath voltage waveform and Monte-Carlo simulation of ion motion in the sheath to get the IEDF taking into account ion collisions with the neutral particles. The following discharges were studied: argon and xenon discharges as examples of atomic ions; hydrogen and nitrogen as examples of molecular ions. The experimentally measured IEDFs agree well with the calculated ones. This research was supported by the Russian Science Foundation Grant No. 14-12-01012 References : [1] T. Rakhimova et al., IEEE Trans. Plasma Sci. 34 (2006) 867. [2] N. A. Dyatko, Yu. Z. Ionikh, A. V. Meshchanov, and A. P. Napartovich, Plasma Physics Reports 31 (2005) 871. [3] A. N. Vasilieva, D. G. Voloshin, A. S. Kovalev, and K. A. Kurchikov, Plasma Physics Reports 41 (2015) 426. [4] X. Zhu, Z. Cheng, Y. Pu, U. Czarnetzki, J. Phys. D: Appl. Phys. 49 (2016) 225204.