Fluid Simulation of the Plasma Characteristics in an Inductively Coupled Plasma Source with Planar and Cylindrical Coils

Inductively coupled plasma (ICP) source with planar and cylindrical coils is one of the effective methods to generate large-area uniform plasma. The effects of the current ratio and phase difference between the planar and cylindrical coil on the plasma characteristics in the dual antenna ICP source are investigated using a two-dimensional (2D) fluid model. When the planar and cylindrical coil sources are in phase, and their currents are 10 A, the inductive electric field is strengthened in the region between planar and cylindrical coils (i.e., r = 0.18–0.21 m, and z = 0.11–0.13 m) due to the superposition of the electric fields in the same direction from the two coils, which strongly heats the electrons in the large radius area of the reactor. As a result, edge-high profiles of ionization rate, plasma density, and ion flux are obtained. As the planar coil’s current increases, the magnitude of the electron density becomes higher, the profiles of the electron density and ion current flux shift from edge-high to center-high due to the enhanced electron heating in the center region, and the best uniform plasma is obtained at 25 A. When both the planar and cylindrical coil currents are maintained at 10 A with the phase shift rising from 45° to 180°, the electric fields from the two antennas act in the opposite direction during the time interval from 1/4 RF period to one RF period, respectively. Moreover, the total inductive electric field becomes weak in the region jointly adjacent to these coils, dominating the plasma generation at the reactor center region. Accordingly, the best uniform plasma is obtained for the case of 135°. In summary, the plasma’s nonuniform distribution can be smoothed by adjusting the power ratio and phase difference between planar and cylindrical coils.