Most plasma sources have to undergo a breakdown process, during which, energy is injected, and particles are ionized. However, we still know little about this fast evolution process. In this work, a one-dimensional direct implicit particle-in-cell/Monte-Carlo collision (PIC/MCC) program is used to study the breakdown process of a capacitively coupled plasma (CCP) driven by dual radio frequencies. The results show that the breakdown process can be divided into three phases: the pre-breakdown, transition, and post-breakdown phases. In the pre-breakdown phase, the plasma density and heating power grow exponentially. The electric field can penetrate the whole discharge region without any shielding, resulting in a higher-than-average electron energy. Secondary electron emission is critical to grow the electron numbers under these discharge conditions. During the transition phase, the formation of sheaths maximizes the electron generation rate and heating power. The formation of sheaths also causes a drastic change in the electrical characteristics of CCP devices. In the post-breakdown phase, the plasma parameters gradually evolve until a steady state is reached. The decreasing rate of generation and the increasing rate of particle loss gradually equalize. The trends of the power gain and plasma loss are similar to the curves for the particle generation and loss rates, and a dynamic equilibrium is finally reached in the last steady state.

Impedance matching can maximize the absorbed power transferred to the plasma load and minimize the reflected power, making it critical and indispensable for capacitively coupled plasmas (CCPs). The external circuit usually interacts with the plasma nonlinearly, so the global simulation of the external circuit and plasma and the matching design is very challenging. In this work, an a priori model was proposed to match the plasma impedance and the external circuit impedance for single-frequency CCPs. By calculating the plasma impedance and the matching network, the matching parameters were iteratively updated to find the best matching parameters. By adjusting the capacitance and the inductance of the circuit by numerical simulations, the reflection coefficient can be significantly reduced. At the same time, the plasma power absorption efficiency will be significantly improved. The universality of the method was demonstrated by choosing different initial circuit, discharge, and plasma parameters. The proposed method provides an effective matching design reference for CCPs.

Matching networks are of vital importance for capacitively coupled plasmas (CCPs) to maximize the power transferred to the plasma discharge. The nonlinear interaction between the external circuit and plasma has to be considered to design suitable matching networks. To study the effect of the matching circuit, we coupled particle in cell/MC(Monte Carlo) model and nonlinear circuit equations based on Kirchhoff’s laws, in a fully nonlinear and self-consistent way. The single-frequency capacitively coupled discharge with ‘L’-Type matching networks are simulated. Fully self-consistently results of circuit and plasma parameters are presented and then power absorbed by the plasma and efficiency are calculated. With the tune of the matching network, the efficiency can reach 28.7%, leading to higher potential as well as higher electron density at fixed source voltage. Besides, only very small components of the third harmonics are found in the plasma voltage and current while surface charge densities have multiple harmonics on account of the strong plasma nonlinearity. Finally, the effects of matching capacitors on discharge are analyzed, results show that smaller C m 1 and C m 2 of 500–1000 pF may be a proper choice for better matching, resulting in higher voltage across the CCP, and thus higher electron density and power absorption efficiency are obtained.

Micro-discharge is the process that gas breakdown occurs on a small spatial scale to generate plasma. With the decrease of the discharge scale, the high electric field makes the field emission (FE) play a leading role in the breakdown process of the micro-discharge, which is one of the reasons that the breakdown voltage deviates from the Paschen curve in a small gap. A one-dimensional implicit particle-in-cell Monte Carlo collision model is used to simulate the whole breakdown process of direct current micro-discharge sustained by FE in argon. The results show that the discharge after breakdown is in arc mode, the breakdown process can be divided into three stages: the pre-breakdown stage, the breakdown stage, and the post-breakdown stage. In the pre-breakdown stage, the sheath and plasma are not formed, the external electric field can penetrate the entire gap. In the breakdown stage, gas breakdown occurs. As the sheath is formed, the rate of change of plasma parameters increases rapidly and the discharge gap changes from capacitive to resistive. In the post-breakdown stage, the anode sheath gradually becomes thinner, but the region where the field is reversed still exists. The particle and energy balance gradually reach equilibrium, and the entire discharge evolves to a quasi-steady-state.

Capacitively coupled plasma (CCP) in CF₄ has been widely used in the semiconductor industry. However, its breakdown process at low pressure has rarely been studied. In this paper, we study the whole CCP breakdown process in CF₄ using the 1D implicit particle-in-cell/Monte Carlo collision (PIC/MCC) method. The detailed evolution of the plasma parameters is given, and both the particle balance and power evolution are discussed. The electron density initially grows exponentially, driven by the penetrating electric field. Both the ionization in the discharge gap and the boundary interaction are significant for electron avalanches. The formation of a sheath maximizes the ionization rate and the heating power, which thoroughly changes the field structure. In the post-breakdown phase, the growing negative ion density shrink the sheaths and changes the heating mode from the α mode to the drift-ambipolar mode. The particle generation rate and heating power show a growth trend after a brief decline. The growth of the recombination rate slowly balances the gain and loss of ions, which finally stabilizes the discharge.

The breakdown of SF ₆ gas at low pressure is of vital importance to both aerospace and microelectronics industries. However, the breakdown characteristics of SF ₆ in direct current at low pressure are still seldom studied. In this work, one-dimensional implicit particle-in-cell/Monte-Carlo collision algorithm is used to study the entire direct current breakdown process of low-pressure SF ₆ . The ion-molecule collision, recombination, and external circuit are considered in the model. According to the results, the breakdown process can be divided into three stages: pre-breakdown stage, breakdown stage, and post-breakdown stage. In the pre-breakdown stage, the cathode sheath is not yet formed so the constant electric field exists in the entire area. In the breakdown stage, the formation mechanism of the cathode sheath is analyzed and the electrodes as a whole changes from capacitive to resistive, sharing the voltage with the external resistance. In the post-breakdown stage, the continued growth of positive ions leads to the formation of a thin anode sheath, which further causes the negative plasma potential, different from electropositive gas. The energy production terms including heating power and secondary electron emission (SEE) power are equal to the energy loss terms including collision loss power and boundary loss power, where collision loss power and boundary loss power are almost equal, while SEE power is negligible. In the final, plasma parameters gradually evolve to the last steady-state.