Electrical properties of planar rf discharges for dry etching

Abstract

rf impedance, dc self-bias, and ion sheath (dark space) thicknesses are measured in an O2 discharge for 7–53 Pa pressure and 50–800 W rf power (13.56 MHz). Special attention is paid to corrections for reactor stray impedances. It is concluded that the discharge can be described as a capacitance (the ion sheath) with both a parallel and a series resistance, the series element being the more important one. Good agreement is found between optical and electrical measurements of the ion sheath thickness. Evidence is presented that the dc potential difference between plasma and ground and rf electrode can be estimated with reasonable accuracy from the dc self-bias and the optical dark space thicknesses. Positive ion acceleration in the ion sheath and electron-neutral collisions in the bulk of the plasma glow account for only part of the total rf power transfer. It is suggested that significant dissipation takes place near the glow-sheath boundary, although a quantitative description cannot be given yet.

Double layer onset inside the near-electrode sheath of a RF capacitive discharge in oxygen

“…The experimental data we obtained for T e are in good agreement with the calculations from [37]. At the same time we observed an additional brightly shining layer inside the nearelectrode sheath of the RF discharge in electronegative gases SF 6 and CF 4 . However, the probe measurements in these gases are impeded, because the surface of the probe is quickly coated with a sulphur film (in SF 6 ) or a polymer film in CF 4 , which are difficult to remove simply by heating the probe to a high temperature.…”

“…Van Roosmalen et al [6] carried out experiments in 13.56 MHz oxygen discharge at 6.67-53.3 Pa and 50-800 W. They attempted to reconcile their experimental results with various theoretical models and found that more than half the dissipated power remains physically unaccounted for. Jurgensen [7] proposed a model of the near-electrode sheath of the RF discharge in oxygen.…”

“…A large number of experimental and theoretical papers studying the characteristics of this type of the discharge were published (see, e.g., [6][7][8][9][10][11][12][13][14][15][16][17]). Let us present a brief review of main results obtained with the RF discharge in oxygen.…”

“…The pumping was accomplished with pre-vacuum and turbo molecular pumps permitting to achieve the limiting pressure of 2.67 Â 10 À4 Pa. The generator (5) delivered the RF voltage to another electrode via the matching box (6). The choke of L c ¼ 4 mH inductance switched across the electrodes outside the chamber removed the self-bias voltage.…”

Satistical Analysis of SiO2Contact Hole Etching in a Magnetically Enhanced Reactive Ion Etching Reactor

“…Increasing pressure decreases electron diffusion toward the electrode because of an increase in electron-neutral collisions, so the DC self-bias voltage also decreases as the pressure increases [19]. The sheath thickness and DC self-bias voltage were found to decrease with increasing pressure at 53-400 mTorr [24] and 20-200 mTorr [25]. The measurements showed that the capacitive reactance of the sheath decreased at higher pressures.…”