A one-dimensional hybrid model is developed to study the characteristics of energy and angular distributions of the ions and fast neutrals impinging on the rf-biased electrode in a dual-frequency capacitively coupled Ar discharge. The hybrid model consists of a fluid model that determines the spatiotemporal evolution of the discharge, and a Monte-Carlo model that, including the electron-neutral, ion-neutral, and fast neutral-neutral collisions, predicts the energy and angular distributions of the ions and fast neutrals on the rf-biased electrode. The influence of pressure, voltage amplitude, and frequencies of the two rf sources on the energy and angular distributions is discussed. The ion energy distributions (IEDs) appear to have multiple peaks in the dual-frequency capacitively coupled rf discharge rather than bimodal shape in a conventional single-frequency rf discharge. The ion angle distributions (IADs) have a significant peak at a small angle, and most ions strike to the process surface with the angle less than 4°. With the increase of the pressure, the maximum energy of IEDs and the peaks of IADs decrease. The structures of IEDs are controlled mainly by the voltage and frequency applied to the two rf sources. By decreasing the frequency or adding the voltage applied to the low-frequency (LF) source, the width of IEDs and the maximum energy increase. More ions strike to the electrode with a small angle by increasing either the voltage of LF source or the frequency of high-frequency source. The energy and angular distributions of the fast neutrals are correlative with those of the ions. Compared with the ions, the fast neutrals have a much lower energy and the scattering effect becomes more prominent.

Geometrically symmetric and electrically asymmetric discharges operating at 13.56 MHz and 27.12 MHz with variable phase angle between the harmonics are simulated by a one-dimensional implicit particle-in-cell/Monte Carlo collision model in argon at a pressure of 30 mTorr. The amplitude of each of the harmonics is chosen to be 150 V. The magnetic fields, with strengths of 10 G and 100 G, are parallel to the electrodes and homogeneous throughout the entire electrode gap in a direction perpendicular to the electrodes. It is found that, with a weaker magnetic field at 10 G, the plasma density is nearly doubled and the self-bias is almost unaffected. However, with a stronger magnetic field at 100 G, the plasma density is significantly increased and nearly independent of the phase angle, but at the cost of decreasing the self-bias, which results in a smaller adjustable range of ion bombardment energy. In general, we have demonstrated that an external magnetic field will expand the operational parameter spaces and thus may promote some related applications in coupled plasma sources with electrical asymmetry effects.

With the energy resolved quadrupole mass spectrometer and hybrid simulation, the influence of low-frequency (LF) source parameters on the ion energy distributions (IEDs) of argon ions impinging on the grounded electrode was studied, both experimentally and numerically, in a dual frequency capacitively coupled plasma. It was shown that for decreasing LF or increasing LF power, the high energy peak in IEDs shifts toward the high energy region significantly. The simulation results were in general agreement with the experimental data.

The characteristics of magnetized capacitively coupled plasmas (CCPs) driven by combined dc/rf sources in argon have been investigated by a one-dimensional implicit Particle-in-cell/Monte Carlo collision model. Discharges operating at 13.56 MHz with a fixed rf voltage of 300 V are simulated at the pressure of 50 mTorr in argon. Four cases, i.e., CCP driven by rf source, rf + dc sources, rf source with magnetic field, and rf + dc sources with magnetic field, are presented and compared at the Vdc = −100 V, B = 50 Gs, and γi = 0.2. It is found that, with the influence of dc voltage and magnetic field, the plasma density has been greatly enhanced by over one order of magnitude over the rf-only case. This is due to the fact that the mean free path of electrons decreases by the cyclotron motion and the energetic secondary electrons are trapped by the magnetic field, leading to a significant increase in heating and ionization rates. Moreover, transition of the stochastic to Ohmic electron heating mechanism takes place as the magnetic field increases because electron kinetics can be strongly affected by the magnetic field. In general, we have demonstrated that such a configuration will enhance the discharge and thus enable CCPs work under extremely high energy density stably that can never be operated by any other configurations. We expect that such a configuration can promote many related applications, like etching, sputtering, and deposition.

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