The measurement and control of the ion energy distribution function at a surface in an RF plasma

Abstract

Using an RF-driven collecting surface, mounted on the front end of a high-resolution energy-resolved mass spectrometer, the ion energy distribution functions (IEDFs) within a 13.56 MHz argon discharge have been measured and controlled. A technique of RF signal feedback has been developed, in which the RF amplitude and phase (fundamental and first two harmonics) in the sheath are varied, so manipulating the mean bombarding ion energies and widths of the IEDFs. For high RF sheath potentials, the IEDFs are broad and bi-modal. However as the sheath potential drop is reduced (with imposed matched RF signal) the IEDFs narrow, eventually becoming single peaked when no RF potential drop is present in the sheath. The observed widths in the IEDFs broadly agree with simple modelling predictions for the `high frequency' RF sheath regime; however we calculate, from the ion spectral data, marginally thinner sheaths than given by the Child-Langmuir law (derived using the mean DC sheath potential).

The Effect of Positive Ion Energy on Plasma Polymerization: A Comparison between Acrylic and Propionic Acids

“…9 Hence, by nulling the RF sheath potentials, we manipulate the time average potential difference between the limits V p -V sb (upper energy limit, no bias potential applied) and V p -V f (lower energy limit, with the nulling RF potentials applied). 7 V p is the time average plasma potential. The self-bias and floating potentials were monitored through a high-impedance RF filter.…”

“…The basis of the technique has been described in detail in earlier publications, , and so only a brief description is given here. Normally, in an RF plasma, there is an RF potential difference between the bulk plasma and the substrate, across the sheath region .…”

Quantitative determination of mass-resolved ion densities in H2-Ar inductively coupled radio frequency plasmas

“…To determine the detection efficiency η PM of the plasma monitor one would need a source of ions with variable energy and known and variable flux as well as angular distribution which is experimentally nearly impossible (see also Ref. 36 ). Ion energy distributions are measured with a plasma monitor by keeping the pass energy in the cylindrical-mirror analyzer constant to achieve constant energy resolution 37,38 .…”

“…There are at least two articles 36,38 that discuss the fact that the transmission through a plasma monitor depends on the particle energy and that the energy-dependent transmission can change depending on the settings in the ion optics. For their studies they used a different plasma monitor system, namely a Hiden EQP 300 energy-resolved mass spectrometer.…”

Formation mechanism of graphite hexagonal pyramids by argon plasma etching of graphite substrates

“…In fact, in our conditions the ion transit time in the sheath is about a third of an rf period. In such case, the final ion energy depends on the plasma potentialwhich oscillates at the rf frequency-during its crossing of the sheath 24 . However, the substrates are located in the diffusion chamber far from the rf power absorption limiting the amplitude of the V p oscillations.…”