Measurements of time average series resonance effect in capacitively coupled radio frequency discharge plasma

Abstract

Self-excited plasma series resonance is observed in low pressure capacitvely coupled radio frequency discharges as high-frequency oscillations superimposed on the normal radio frequency current. This high-frequency contribution to the radio frequency current is generated by a series resonance between the capacitive sheath and the inductive and resistive bulk plasma. In this report, we present an experimental method to measure the plasma series resonance in a capacitively coupled radio frequency argon plasma by modifying the homogeneous discharge model. The homogeneous discharge model is modified by introducing a correction factor to the plasma resistance. Plasma parameters are also calculated by considering the plasma series resonances effect. Experimental measurements show that the self-excitation of the plasma series resonance, which arises in capacitive discharge due to the nonlinear interaction of plasma bulk and sheath, significantly enhances both the Ohmic and stochastic heating. The experimentally measured total dissipation, which is the sum of the Ohmic and stochastic heating, is found to increase significantly with decreasing pressure.

Influence of finite geometrical asymmetry of the electrodes in capacitively coupled radio frequency plasma

“…17 (Fast and slow dynamics) and comparing the rf current waveforms in the present study, it is realized that the deviation of the rf current waveforms from sinusoidal structure and generation of distortions are related to geometrical asymmetry and PSR effect, respectively. It has been also reported the experimentally measured rf current waveforms at different pressure for finite geometrical asymmetry 18 (with ratio of the electrodes is 1.56) and observed the distortions in the rf current waveforms with comparatively less deviation from sinusoidal structure. Consistent with the experimental observations, 18 it is observed that the distortions in the rf waveforms reduce with increasing pressure.…”

“…It is also known that the stochastic heating is also plays a crucial rule in heating the CCRF plasma at low pressure. [17][18][19] Thus, considering hard wall model and taking into account the Ohmic and stochastic heating, the effective collision frequency can be represented by…”

“…Several numerical and modeling studies have been reported [17][18][19][20][21][22] to study the heating mechanism by PSR in asymmetric CCRF plasma ignoring the plasma sheath at the grounded electrode by considering the grounded electrode is infinitely larger than the powered electrode. Although many reactive ion etchers use CCRF plasma discharge, which is off course finite asymmetry, studies on such plasmas to understand the different mechanism like generation of dc self-bias, PSR effect, etc., are scanty.…”

On the self-excitation mechanisms of plasma series resonance oscillations in single- and multi-frequency capacitive discharges

“…6 In electrically asymmetric discharges driven by multiple consecutive harmonics, such constraints are no longer given and a broad spectrum of higher harmonics is observed due to the self-excitation of the PSR. 1,15,16,18,20 The Fourier spectrum of the electron current density of the 54. 24 MHz discharge again reveals the alternating amplitudes for odd and even …”

“…Another way of inducing an asymmetry is via the Electrical Asymmetry Effect (EAE), [17][18][19][20][21][22][23][24][25][26] i.e., by using a driving voltage waveform with unequal absolute values of the global maximum and minimum. Donko et al 17 have shown that the PSR is self-excited in geometrically symmetric, electrically asymmetric discharges operated at a fundamental frequency (13.56 MHz) and its second harmonic (27.12 MHz).…”