The Gaseous Electronics Conference radio-frequency reference cell: A defined parallel-plate radio-frequency system for experimental and theoretical studies of plasma-processing discharges

Abstract

A "reference cell" for generating radio-frequency (rf) glow discharges in gases at a frequency of 13.56 MHz is described. The reference cell provides an experimental platform for comparing plasma measurements carried out in a common reactor geometry by different experimental groups, thereby enhancing the transfer of knowledge and insight gained in rf discharge studies. The results of performing ostensibly identical measurements on six of these cells in five different laboratories are analyzed and discussed. Measurements were made of plasma voltage and current characteristics for discharges in pure argon at specified values of applied voltages, gas pressures, and gas flow rates. Data are presented on relevant electrical quantities derived from Fourier analysis of the voltage and current wave forms. Amplitudes, phase shifts, self-bias voltages, and power dissipation were measured. Each of the cells was characterized in terms of its measured internal reactive components. Comparing results from different cells provides an indication of the degree of precision needed to define the electrical configuration and operating parameters in order to achieve identical performance at various laboratories. The results show, for example, that the external circuit, including the reactive components of the rf power source, can significantly influence the discharge. Results obtained in reference cells with identical rf power sources demonstrate that considerable progress has been made in developing a phenomenological understanding of the conditions needed to obtain reproducible discharge conditions in independent reference cells.

Measurement of the Vertical Nonuniformity of the Plasma Sheath in a Complex Plasma

“…To validate the theory given above, an experiment was conducted using the CASPER GEC rf reference cell at Baylor University [12]. In the CASPER GEC cell, a radio-frequency, capacitively coupled discharge is formed between two parallel-plate electrodes, 8 cm in diameter and separated by 3 cm, with the bottom electrode air-cooled.…”

“…Using a fast Fourier transformation technique, the resulting spectrum is analyzed and information concerning the individual interaction forces obtained. For a vertical oscillating pair of dust particles, the general equations of motion can be expressed as, (1) In the above, y 1,2 represent the vertical positions of particles 1 and 2 respectively (where 1 represents the upper and 2 the lower particle), β 1,2 are their neutral drag coefficients, ω 01,2 their resonant frequencies, ω is the applied external driving frequency, f 12 = F 12 /m 2 , f 21 = F 21 /m 1 , m 1,2 are the dust particle masses, and F 12,21 are the interaction forces between the two particles, which is a function of their separation distance |y 1 -y 2 |. For small oscillation amplitudes, the interaction force can be assumed linear to |y 1 -y 2 |, i.e.…”

Investigation of dust wake field oscillations

“…The experiment described herein was conducted employing the CASPER GEC rf reference cell [6]. A radio-frequency, capacitively coupled discharge was formed between two parallel-plate electrodes, 8 cm in diameter and separated by 3 cm, with the bottom electrode air-cooled.…”

Digital imaging and analysis of dusty plasmas

“…In order to create a controlled plasma environment and make meaningful quantitative and qualitative observations of these systems, the GEC rf reference cell was introduced as a standard tool in which to produce and collect data (Hargis, et al, 1994;Samsonov, 2000). Obtaining and analyzing data from the reference cell without perturbing the plasma requires an efficient optical diagnostic system.…”