Control of charged particle dynamics in capacitively coupled plasmas driven by tailored voltage waveforms in mixtures of Ar and CF₄

Abstract

The charged-particle power absorption dynamics in capacitively coupled plasmas operated in different CF 4 -Ar gas mixtures and driven by tailored voltage waveforms is experimentally investigated by phase-resolved optical emission spectroscopy in conjunction with kinetic simulations and an analytical model. Single-and triple-frequency 'peaks'and 'valleys'-type waveforms (generated as a superposition of multiple consecutive harmonics of 13.56 MHz) are studied at pressures of 20 and 60 Pa with 25 mm electrode gap and 150 V total driving voltage amplitude to determine the effects of the tailored driving voltage waveform in different gas mixtures on the density profiles of the particle species, the electronegativity, the DC self-bias, and the excitation/ionization dynamics. As the argon content in the buffer gas is increased, the discharge switches from the drift-ambipolar (DA) power absorption mode to the α-mode. This transition occurs due to the disappearance of the bulk and ambipolar electric fields as the electronegativity of the plasma decreases with increasing argon content. This effect is more pronounced at higher pressures, where the negative ion density is higher. We observe a significant change in the plasma's symmetry, DC self-bias, and mean electron energy as a result of the DA-to α-mode transition. At 60 Pa the simulation reveals a drastic increase of the spatially averaged electronegativity induced by increasing the argon admixture from 20% to 30%. This counterintuitive finding is explained by the effect of this admixture on the spatio-temporal electron dynamics. Finally, the generation of the DC self-bias as a function of the argon content is understood by the analytical model based on these fundamental insights into the plasma physics.

Electron heating dynamics and plasma parameters control in capacitively coupled plasma

“…简单化学反应的氩气CCP放电, 一维(one dimensional, 1D)模拟大约需要1-2天 [17,58] , 柱坐标小 腔室(10 cm腔室半径, 2 cm电极间距)、低密度 (10 15 -10 16 m -3 )的串行二维(two dimensional, 2D) 模拟需要1-2周 [18] , 针对略大一些腔室结构(12 cm 腔室半径, 6.7 cm电极间距), 基于GPU的2D并 行PIC/MCC模拟同样需要10天左右 [19,59] 等 [3,59] 开发的基于GPU的2D PIC/MCC模型等.…”

Electron power absorption in capacitively coupled neon-oxygen plasmas: a comparison of experimental and computational results

“…In the STR-mode, which develops when both positive and negative ions can react to the fast variation of the RF electric field, the ionization, concentrated within the bulk region, exhibits layered structures called "striations"; these are generated as a result of the formation of alternating space charges and the modulation of the electric field and the energy gain of electrons in the plasma bulk. The simultaneous presence of the ionization patterns characteristic of the different discharge operation modes can be observed in low-pressure CCPs under specific discharge conditions, as well as transitions between these modes by varying the external control parameters [13][14][15][16][17][18]. Experimental observation of the space and time-resolved plasma emission based on Phase Resolved Optical Emission Spectroscopy (PROES) [19][20][21] provides invaluable information on the electron power absorption and excitation/ionization dynamics in low-pressure CCPs [7,8].…”

eduPIC: an introductory particle based code for radio-frequency plasma simulation

“…CCPs have been studied using the PIC/MCC method in various gases, e.g., in Ar [53,75], He [76], O 2 [77][78][79][80][81][82], H 2 [83], CF 4 [47,[84][85][86] and Cl [87], as well as in Ar-CF 4 [88,89], Ar-O 2 [90], Xe-Ar [91], CH 4 -H 2 [92], and Ar-H 2 [93] mixtures. The limitations and the optimization of the PIC/MCC method have been discussed, e.g, in [94][95][96][97], and the issues of code verification and validation have been addressed in, e.g., [98][99][100].…”