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Indexed by:期刊论文

Date of Publication:2018-05-01

Journal:PLASMA SOURCES SCIENCE & TECHNOLOGY

Included Journals:SCIE

Volume:27

Issue:5

ISSN No.:0963-0252

Key Words:electrical asymmetry effect; multiple harmonics; very high frequency discharges; plasma uniformity; transient behavior; electromagnetic effects

Abstract:A novel method, the so-called electrical asymmetry effect (EAE), is gaining increasing interest for realizing the separate control of the ion flux and ion energy. In this paper, a two-dimensional fluid model combined with the full set of Maxwell equations is used to investigate the plasma properties in an electrically asymmetric capacitive discharge sustained by multiple consecutive harmonics operating in the very high frequency regime. The results indicate that by increasing the total number of consecutive harmonics k, the modulation of the dc self-bias induced by changing theta(1) (the relative phase of the fundamental frequency) becomes different, especially for k <= 6. In a discharge driven by eight consecutive harmonics, the dc self-bias varies with a period 2 pi, and the most positive value appears at theta(1) = 3 pi/2. In addition, with the electromagnetic effects taken into account, the plasma density shifts from edge-high to uniform when theta(1) increases from 0 to pi, and the maximum moves again towards the radial wall at theta(1) = 3 pi/2. Moreover, the transient behavior of electrodynamics is also important for a better understanding of the EAE. Within a period, three positive peaks of I- are observed, which cause substantial ionization at similar places. P-r is characterized by a pronounced peak at the end of the period, and the lowest peak value appears at theta(1) = pi. The results obtained in this work are important for improving the plasma processes by utilizing the EAE, especially when the higher order harmonics are included.