Power dissipation and impedance measurements in radio-frequency discharges

Abstract

An improved method for the measurement of the power consumed in low pressure, radio frequency discharges is presented. The method involves the measurement of current and voltage waveforms outside the reactor, and the determination of the discharge impedance and the network of parasitics. The measured waveforms are transformed to the equivalent ones at the powered electrode, by using an electrical circuit model of the stray impedance of the cell, with experimentally determined components. A tunable shunt circuit is used for minimizing displacement currents. The equivalent circuit contains elements which account also for resistive power losses in the cell-shunt circuit. The obtained discharge power is compared with measurements of the total power output of the generator made by a power meter. Results concerning power consumption and impedance in argon and silane discharges are presented as a function of the excitation voltage and the pressure. In both cases there is a discharge impedance drop, for higher voltage or pressure, which leads to higher power consumption in the discharge. The measurements show that only a small, nonconstant part of the power is consumed in the discharge, whereas, the inclusion of resistive loses leads to more accurate results. The mechanisms of the discharge impedance drop are further discussed in terms of their relation to microscopic plasma phenomena and quantities.

Relative importance of hydrogen atom flux and ion bombardment to the growth of μc-Si:H thin films

“…The amount of RF power actually fed into the discharge chamber was determined using an accurate method employing the Fourier transform determination of power and impedance phase, from current and voltage measurements [12], while the deposition rate was measured in situ using laser reflectance interferometry [13].…”

Exploration of the deposition limits of microcrystalline silicon

“…All of the results presented concern deposition experiments carried out in capacitively coupled rf discharge chambers that are completely characterized from the electrical point of view in such a way that the power actually consumed in the discharge is accurately known through voltage and current waveform measurements [31]. Moreover, to the best sensitivity of our laser-scattering diagnostics, the discharges operate in particle-free conditions, unless specifically stated otherwise.…”

Atmospheric glow discharges from the high-frequency to very high-frequency bands

“…A Pearson 2877 200 MHz current probe and Tektronix P5100 250 MHz voltage probe were connected directly to the powered electrode to capture current and voltage waveforms. The difficulties associated with accurate electrical measurements of rf discharges particularly in the VHF band 4,17 were addressed by minimizing stray inductance within the external circuitry and by employing a calibration procedure to ensure accurate phase and power measurements. 17 Optical emission spectra were obtained using an Andor Shamrock spectrometer with a grating of 2400 grooves/mm and plasma images were captured using an Andor iStar iCCD camera.…”