Hysteresis and mode transitions in a low-frequency inductively coupled plasma

Abstract

Global electric properties, distributions of the induced electromagnetic fields, electron density, temperature, and plasma potential in the 500 kHz planar-coil inductively coupled plasma source have been investigated. The transitions between the two (E and H) discharge operating regimes with variation of input power and operating gas pressure have been demonstrated. It has been shown that the E↔H transitions are accompanied by the resonant minima in the rf power reflection coefficient, which are characteristic for mode jumps in electron cyclotron resonance and microwave slot-excited discharges. The optical emission spectra of argon atoms and ions together with global power balance arguments suggest that the step-wise ionization via the excited states of argon atoms and ions is presumably a mechanism which is responsible for hysteresis. The achieved high plasma density with a high homogeneity level, and low electron temperature and plasma potential imply that the studied plasma source is promising for industrial applications.

Inductively coupled plasmas sustained by an internal oscillating current

“…Above all, finite B can result in enhanced penetration of the rf field due to secondary nonlinear effects, 39 which become more pronounced at lower operation frequencies. 23 The interesting feature of the IOC configuration is that the poloidal rf current and hence, the azimuthal magnetic field, are driven in a linear fashion at the fundamental frequency and one can expect enhanced rf field penetration due to primary nonlinear effects. Furthermore, the internal oscillating current eliminates the nonuniformity of the rf power density in the vicinity of the chamber axis, which is inherent to the flat external coil ICP configurations.…”

“…10,[23][24][25] Figures 2-3 show that the electromagnetic field generated by the internal oscillating current is highly uniform in radial direction, especially in the vicinity of the chamber walls. We note that all field components, except for the axial magnetic field ͓Figs.…”

“…In these calculations we assume the same size of the vacuum chamber and the rf frequency as in lowfrequency ICPs (Rϭ16 cm, Lϭ20 cm, and /2 ϭ500 kHz͒. 23,24 In the steady state we have…”

“…We note that T e declines in the pressure range 15-200 mTorr, which appears to be consistent with numerical and experimental results on rf discharges in argon. 23,24,31 …”

“…In reality, d includes a thick air gap inbetween the coil holder and a quartz window. 10,[23][24][25] It is worth mentioning that the field penetration length is an important characteristic of rf power deposition. 2 Figure 4 shows the ratio qϭ(␥ 1 (2) /␥ 0 ) Ϫ1 of the field penetration depths in Fig.…”