Bulletin of the American Physical Society
69th Annual Gaseous Electronics Conference
Volume 61, Number 9
Monday–Friday, October 10–14, 2016; Bochum, Germany
Session RR1: Electrical Diagnostics IIFocus
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Chair: Alan Howling, Swiss Plasma Center Room: 1 |
Thursday, October 13, 2016 11:00AM - 11:30AM |
RR1.00001: Development and Miniaturization of RF based probes for Electron Density Measurements Invited Speaker: Keiji Nakamura To make a diagnostics on plasmas for materials processing plasmas accompanying with deposition of non-conducting films in etching and/or CVD processes, curling probe (CP) with a spiral slot antenna has been recently developed as a compact diagnostic tool which enables the local electron density measurement. The electron density is obtained from a shift of the probe resonance frequency in discharge ON and OFF monitored by a network analyzer (NWA). A conventional CP has a diameter larger than \textasciitilde 15 mm typically, because a slot length of the CP is as long as several tens millimeters for its resonance frequency less than several GHz. Further miniaturization of the CP was required to expand applicable range to various plasma sources like a narrow-gap parallel plate discharge. We tried miniaturization of the CP down to less than \textasciitilde 3 mm in the probe diameter by fabricating narrow spiral slot antenna, and experimentally and numerically the miniaturized probe was investigated how much influence the slot width has on probe resonance characteristics and electron density measurements. In the case of the conventional CP made of stainless steel, \textasciitilde 0.3-mm-wide normal slot antenna, the resonance spectra was clearly observed regardless of antenna materials of copper or stainless steel (SS). However, when the slot width was reduced down to \textasciitilde 0.03 mm, the slot resonance was strongly dependent on the antenna materials. Namely the resonance peak was almost vanished for the SS antenna, whereas clearly appeared for the copper antenna. In general, the narrower the slot is, the higher attenuation factor the slot has for electromagnetic wave propagating along the slot. In such an attenuated transmission line of the narrow slot, high electric conductivity of the antenna seems preferable for the slot resonance. Furthermore, the miniaturized CP with the copper antenna was also introduced into low pressure (\textless \textasciitilde 1Pa) Ar plasma. The resonance frequency was confirmed to changes sensitively with electron density, suggesting the miniaturized CP will be available to electron density measurements. Numerical simulation showed that localization of electromagnetic fields near the slot was remarkably enhanced by decreasing in the slot width, suggesting that the miniaturized CP suffers from more significant sheath effects compared to the conventional CP. [Preview Abstract] |
Thursday, October 13, 2016 11:30AM - 11:45AM |
RR1.00002: Simulation of reactive and resistive resonances of a curling probe for low and high pressure plasma diagnostics Ali Arshadi, Ralf Peter Brinkmann Curling probe (CP) as a novel realization of ''Active Plasma Resonance Spectroscopy'' concept, reveals a great ability for electron density measurement in a low pressure plasma. A weak RF signal is coupled into the plasma via a CP. The spectral response of the plasma is recorded and a mathematical model is used to determine the electron density. The CP is a spiral slot resonating at distinctive frequencies which are strongly dependent on the electron density. Since the CP can be miniaturized and flatly embedded into the chamber wall, the perturbation and metal contamination are negligible. With the assumption of little spiralization effect, this work investigates a ''straightened'' CP. The diffraction of an incident plane wave at a rectangular slot is calculated by solving Maxwell's equations and the cold plasma model simultaneously. In low pressure plasmas two kinds of reactive resonance are observed. The lower frequency of resonance has a surface wave characteristic and the higher one is associated with the wave propagation along the probe length. In high pressure plasmas reactive resonance is not observed but a resistive reonance even at frequencies smaller than the surface wave frequency is excited. Good agreement of our computations with the numerical results is shown. [Preview Abstract] |
Thursday, October 13, 2016 11:45AM - 12:00PM |
RR1.00003: Accuracy of cutoff probe for measuring electron density: simulation and experiment Dae-Woong Kim, Shin-Jae You, Si-June Kim, Jang-Jae Lee, Jung-Hyung Kim, Wang-Yuhl Oh The electron density has been used for characterizing the plasma for basic research as well as industrial application. To measure the exact electron density, various type of microwave probe has been developed and improved. The cutoff probe is a promising technique inferring the electron density from the plasma resonance peak on the transmission spectrum. In this study, we present the accuracy of electron density inferred from cutoff probe. The accuracy was investigated by electromagnetic simulation and experiment. The discrepancy between the electron densities from the cutoff probe and other sophisticated microwave probes were investigated and discussed. We found that the cutoff probe has good accuracy in inferred electron density. [Preview Abstract] |
Thursday, October 13, 2016 12:00PM - 12:15PM |
RR1.00004: ABSTRACT WITHDRAWN |
Thursday, October 13, 2016 12:15PM - 12:30PM |
RR1.00005: Diagnostics of plasma and particle flows extracted from bipolar gridded plasma sources Stanislav Dudin, Dmytro Rafalskyi, Ane Aanesland Gridded plasma sources have a strong interest from both industry and research community due to large number of their applications, including electric propulsion, plasma acceleration for fundamental studies, ion beam surface treatment and semiconductor etching, etc. Commonly, a dc electric field is applied between the grids of these sources to accelerate positive ions, while the space charge compensation of the beam is achieved using an additional external electron source. Few recent concepts assume bipolar extraction of particles, such that both positive and negative particles are extracted from plasma and accelerated. The formed beam can be composed of extracted continuously or alternately positive and negative ions, or positive ions and electrons. Diagnostics of these beams is a challenging task, in particular absolute flux and energy distribution measurements for different species present in the bipolar beam. In this work we present few recent diagnostic techniques allowing to measure absolute fluxes and energies of $+$/- ions and electrons, and also methods to investigate temporal behavior of these flows. [Preview Abstract] |
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