Influence of Applied DC Bias on the Characteristics of RF Capacitive Coupling Discharge

DC Bias can better suppress the RF-CCP surface charging effect, but the influences on RF-CCP discharge parameters and complex parameter control for power supply are still unclear. A board-board structure RF-CCP simulation model for DC and RF sources was constructed. A negative DC source was applied on the basis of the RF source to study its impact on the discharge characteristics of RF-CCP. The effects of RF and DC bias on discharge parameters were compared. The results show that when no DC source is applied, the period average electron density N_{e, ave} and the period average electron temperature T_{e, ave} are symmetrically distributed, and N_{e, ave} presents a convex shape with low ends and high middle. T_{e, ave} has a sharp rise within 4 mm from the pole plate, and reaches a maximum value at 1 mm from the two pole plates. The DC source will increase and offset N_{e, ave} in the main plasma zone, decrease N_{e, ave} on the DC source side, increase N_{e, ave} at a significant speed on the bottom plate side. Applying a DC bias can improve one-side electron temperature and electron flux, but the ability to increase electron density is weaker than RF source. In order to increase the electron temperature and electron flux on one side, a DC source should be applied. If the overall electron density is increased, the power of RF source should be increased.