Experimental and numerical investigations of electron density in low-pressure dual-frequency capacitively coupled oxygen discharges

Abstract

The electron density is measured in low-pressure dual-frequency (2/60 MHz) capacitively coupled oxygen discharges by utilizing a floating hairpin probe. The dependence of electron density at the discharge center on the high frequency (HF) power, low frequency (LF) power, and gas pressure are investigated in detail. A (1D) particle-in-cell/Monte Carlo method is developed to calculate the time-averaged electron density at the discharge center and the simulation results are compared with the experimental ones, and general agreements are achieved. With increasing HF power, the electron density linearly increases. The electron density exhibits different changes with the LF power at different HF powers. At low HF powers (e.g., 30 W in our experiment), the electron density increases with increasing LF power while the electron density decreases with increasing LF power at relatively high HF powers (e.g., 120 W in our experiment). With increasing gas pressure the electron density first increases rapidly to reach a maximum value and then decreases slowly due to the combined effect of the production process by the ionization and the loss processes including the surface and volume losses.

Electron heating dynamics and plasma parameters control in capacitively coupled plasma

“…例如, 深刻地揭示了CCP放电中一些非线性谐波的产 生, 如串联共振的激励 [33] . 此外, 由于等效回路中 各个电学元件可以用等离子体参量(如电子密度和 电子温度等)来表达, 这样等效回路中电阻两端的 电压和流过回路的电流可以表达为等离子体物理 量的函数, 从而近似估计出等离子体沉积功率 [62] .…”

Measurements of argon metastable density using the tunable diode laser absorption spectroscopy in Ar and Ar/O 2

“…1. The vacuum vessel has been described in more detail elsewhere, [12,22,29] so only a brief description is given here. The plasma is produced between the two circular plate electrodes with 210 mm in diameter and 30 mm in spacing.…”

“…In order to reduce the rf disturbance, the hairpin probe used in our experiment is fully floating and its detailed description can be found elsewhere. [22] The hairpin probe is based on the microwave resonance theory, which was developed by Piejak et al [32,33] and Curley. [34] The electron density can be obtained from the following expression…”

“…[1,2] Recently, many researches have focused on the Ar/O 2 mixture discharge because of their specific features both experimentally and theoretically. [7,[22][23][24][25][26][27][28] For example, Takechi and Lieberman [23] found that argon addition into oxygen in-ductive discharges can greatly improve the plasma density and the etch rate due to the increased dissociation of O 2 by metastable argon atoms. In a capacitively coupled discharge, Worsley et al [24] also observed that the O radical density is raised upon argon dilution as a result of an increasing contribution of Penning dissociation, which agreed well with the data simulated by Lee et al [26] through using a PIC-MCC model.…”

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

“…As a consequence of this, it is more likely that the highly energetic SEs within the sheaths induce ionization rather than excitation. Due to their high relevance in material processing, oxygen CCPs have been studied extensively, both experimentally and by simulations [13,[35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]. In pure oxygen CCPs, transitions between the α-mode and the DA-mode have been found by changing the gas pressure [13,14], the gap distance [14,17], the driving frequency [13,47], the driving voltage waveform [13,15,18,46,51,52], and the external magnetic field [49].…”