Advancing Capacitively Coupled RF Plasma: Magnetic Fields for Enhanced Control

Capacitively coupled Radio Frequency discharges find diverse applications, spanning from plasma processing of nanoscale semiconductors to ion thrusters crucial for satellite positioning. Over time, numerous techniques have emerged to enhance CCP performance, such as utilizing multiple RF frequencies, tailored waveforms to tune electron kinetics and densities in such systems. One promising approach for controlling plasma parameters involves introducing a magnetic field perpendicular to the sheath electric field. The incorporation of these magnetic fields not only impacts global plasma properties but also exerts influence on local charge particle behavior within the discharge. A cylindrical configuration employing an axisymmetric magnetic field can generate closed E×B drifts, promoting a uniform plasma density. Hence, a novel CCP discharge with an axial magnetic field is developed. The experimental results predict a transition in the discharge asymmetry for a constant discharge power and gas pressure. A range of magnetic fields is observed where the discharge is highly efficient with lower electron temperature. The behavior is attributed to the transition from geometrical asymmetry to magnetic field-associated symmetry. This source can be utilized for the volume production of negative ions due to its unique feature of spatial variation in the electron temperature. Hence, the potential applications of the source are also investigated by producing an oxygen discharge.