Characterization of the E to H transition in a pulsed inductively coupled plasma discharge with internal coil geometry: bi-stability and hysteresis

Abstract

Electrodeless radiofrequency discharges exhibit two modes of operation: a low-density mode in which the power is capacitively coupled to the plasma and which is known as the E-mode, and a higher density mode which is an inductive discharge known as the H-mode. The transition between these modes exhibits hysteresis, i.e. the E to H transition occurs at a different coil current than the reverse H to E transition. Recent theoretical results show that the hysteresis can be qualitatively understood in terms of electron power balance assuming that either the power dissipated or the power absorbed by the plasma electrons has a nonlinear dependence on the electron density. Experiments have been carried out to examine this hypothesis, both by characterizing steady-state E-and H-mode plasmas with a Langmuir probe, and by using a new approach consisting of measuring the internal plasma parameters in a pulsed discharge. In the latter case, the power is time modulated with increasing and decreasing power ramps. This approach allows us to investigate the hysteresis in detail and to study the dynamics of the transition. A number of time-resolved diagnostics including Langmuir probes, current and voltage sensors, optical emission and B-dot probes have been used.

Hysteresis and mode transition in terms of electron energy distribution function for an inductively coupled argon discharge

“…Note that the E-H mode mixing is high in the transition region and the modification of EEDF is most likely in this power region. Since the width of the hysteresis loop is found to be pressure dependent ͑much smaller in the case of low pressure͒, 6,10,23 performing the measurement at one fixed power in E mode will not fairly reflect the similar power coupling conditions. Recently, we have shown that the normalized EEPF immediately before the E to H transition point is identical to the one immediately before the H to E transition point, namely, bi-Maxwellian.…”

“…23,24 The EEDFs presented in Ref. 23 for pressures 0.67 and 6.7 Pa are reported to be Maxwellian and Druyvesteyn-like, respectively.…”

Extreme-ultraviolet light generation in plasmonic nanostructures

“…Specifically, for inductively-coupled (IC) discharge plasmas, bistabilities have been studied for a long time, resulting in a large number of reports [97,98,99,100,120,121,119,122,123]. For example, Fig.…”

“…Here, the emission yield from an argon plasma shows a strong hysteresis as a function of the coil current. Such bistabilities are commonly explained by considering power balance diagrams, which compare the dissipated with the absorbed power in the IC discharge plasma [119]. In Fig.…”

Plasma power measurement and hysteresis in the E–H transition of a rf inductively coupled plasma system

“…In addition, the transition between these two modes has been reported to exhibit hysteresis, i.e., when reducing input power starting in H mode, the transition to E mode occurs at lower powers than the transition to H mode when starting in E mode. 1-8 Hysteresis in the E -H mode transition has been reported, almost exclusively in argon, in the measured optical emission, 1,3,5-7 electrical characteristics, 2-4 plasma density, 3,4,8 and magnetic field 3,4 dependence on coil current or input power. Most often, the studied ICPs have external 1,5,6,8 or internal cylindrical coils 3 but hysteresis has also been reported in external flat coil ICPs.…”