A novel electrostatic probe method for ion flux measurements

Abstract

A novel electrostatic probe method is described in which the ion flux is determined from the discharging of an RF-biased capacitance in series with the probe. By using a large-area planar probe, with a guard ring and located in or on other surfaces, edge effects and perturbations to the plasma volume can be kept small. The ion flux to the probe can be determined even when its surface is coated with insulating material from the plasma itself. Results are reported for ion fluxes in RF-excited plasmas in Ar and in CF 4 in a RIE reactor. In Ar, ion fluxes to the earthed surfaces increase with pressure and power over the ranges 50-200 mTorr and 30-200 W. In CF 4 , over the same ranges the ion fluxes to the surfaces decrease with increasing pressure.

Synergistic etch rates during low-energetic plasma etching of hydrogenated amorphous carbon

“…The dielectric function is determined beforehand and fixed for every thickness (i.e., every datapoint). The unbiased maximum likelihood estimator v 2 -which is a measure of the fit quality 77,82 -for this particular sample reaches 68. If the void fraction is varied, on the other hand, v drops below 25 as can be seen in Fig.…”

“…a capacitive probe). 77,78 The design, operating procedure, and characterization of an ion probe is described in detail by Petcu et al 78 Our planar probe is embedded in a sample holder which provides a measurement directly at the position of the sample. The sample holder itself is electrically floating, whereas the collecting area (200 mm 2 ) is connected to a single external capacitor (12:7 6 0:1 nF).…”

“…77 A dielectric constant of 5:2 and a Debye length of 30 lm -for an electron density and temperature of 6:1 Â 10 15 m À3 and 0:1 eV, respectively -gives an upper limit of 156 lm for the film thickness. 22 The thickness in the measurement presented here decreases from $ 980 to $ 870 nm, thus well below this upper limit.…”

“…This is a second, although less stringent, requirement for a proper functionality of the ion probe. 77,78 Regardless, the bias voltage at the a-C:H surface cannot be measured directly and distortions of the applied pulse shape, therefore, cannot be completely excluded. The bias voltage as measured over the external capacitor is indicated in Fig.…”

Converting a Microwave Oven into a Plasma Reactor: A Review

“…e probe used is an RF-biased ion flux probe (known colloquially as "Bébésone, or BBs"). For full details of the probe and measurement, see [48]. For good probe measurements, visual observations of the plasma volume as a whole and around the probe itself are usually required.…”