Influence of external circuitry on CF4 breakdown process in capacitively coupled plasma

Abstract

Capacitively coupled plasma (CCP) tools are crucial for etching, deposition, and cleaning processes in the semiconductor industry. A comprehensive understanding of their discharge characteristics is vital for the advancement of chip processing technology. In this study, the influence of external circuitry on the breakdown process was investigated under the CF4 discharge system, with a particular focus on challenges presented by the nonlinear nature of the plasma. The results demonstrated that the external circuit significantly affects the discharge process by altering the electric field distribution as well as modifying the electron density and temperature of the plasma. By incorporating the matching circuit, stable discharge was achieved at reduced voltage levels. During breakdown, a substantial increase in the capacitance of the discharge chamber is induced by the formation of the sheath, which alters the amplitude of the electrical signal within the external circuit. The breakdown characteristics are significantly influenced by the capacitance of the matching network. Breakdowns with distinctive characteristics can be achieved by selectively choosing different capacitors. Furthermore, a shift in the CF4 discharge mode at different pressures under the external circuit model and the alteration in the discharge mode affect the electrical properties of the plasma in the matched circuit. These findings could be used to optimize the discharge of CCP and its applications, including surface treatment, material synthesis, and environmental remediation.