On the breakdown process of capacitively coupled plasma in carbon tetrafluoride

Abstract

Abstract 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.