Power transfer efficiency and mode jump in an inductive RF discharge

Abstract

A large-diameter (50 cm) high-density (>10 11 cm −3 ) plasma is produced in a few mTorr argon by inductive RF discharge using a conventional external antenna or a plasma-immersed internal antenna. A power transfer efficiency, i.e., the ratio of net power deposited into plasma to total power into the matching circuits, is measured as a function of the electron density based on a test antenna method. The measured density dependence of the power efficiency is well described by an equivalent circuit where both inductive and capacitive couplings are included with stochastic power deposition process taken into account. The internal antenna, for the conditions studied, has higher power efficiency than the external antenna and enables a stable discharge at low pressures without density jump. The density jump observed in the external antenna discharge is attributed to the mode transition between a capacitive discharge and an inductive discharge. A mechanism of the density jump is successfully explained in terms of the density dependence of the power transfer efficiency.

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.…”

Power transfer and mode transitions in low-frequency inductively coupled plasmas

“…This turns out to be a serious obstacle for the development of automatic control systems for plasma processing applications. 2 Mode jumps have recently become a subject of increasing concern for inductively coupled ͑IC͒, [3][4][5][6][7] helicon-wave sustained, 2,8,9 electron cyclotron resonance, 10 and microwave slot-excited ͑MSE͒ ͑Refs. 11-13͒ plasmas.…”

“…These plasmas are driven by a flat spiral coil placed above the discharge window ͑external-antenna configuration͒ and can operate in both electrostatic (E) and electromagnetic (H) regimes, states in which electrostatic and electromagnetic plasma modes are excited, respectively. 5,6 In IC plasmas driven by flat spiral induction coils the power coupling is predominantly capacitive in the E regime, and the electrostatic field is due to the potential difference between the inner and outer coil turns. 5,14 In the H regime, the power coupling is inductive and the azimuthally symmetric resonator modes (mϭ0) are excited.…”

“…Smooth transitions between the E and H modes have been reported, 6 e.g., in 13.56 MHz low-pressure (p 0 Ͻ10 mTorr) plasmas with internal rf antennas. On the other hand, in IC plasmas with the external coil configuration, [4][5][6] density jumps of at least one order of magnitude have been observed. Examination of the power transfer from the coil to the plasma reveals that the discharge efficiency dramatically increases after the transition to the H discharge regime.…”

Inductively coupled plasmas sustained by an internal oscillating current

“…18 Furthermore, schemes with internally driven rf currents usually achieve plasma production with lower powers than those with external coils. 19,20 Indeed, in conventional external-coil schemes useless rf fields are usually generated outside the chamber. 17 The results of computation show that by using an internal rotating current ͑IRC͒, one can improve the uniformity of power density and simultaneously minimize power consumption.…”