Abstract: A substrate processing apparatus includes a vacuum chamber with upper and lower electrodes and a processing zone for processing a substrate using plasma. The upper electrode includes a surface that is substantially parallel to a surface of the substrate when the substrate is positioned in the chamber. The apparatus includes at least one magnetic field source configured to generate one or more active magnetic fields through the processing zone, and a controller coupled to the at least one magnetic field source and the upper electrode. The controller is configured to apply RF power between the upper and lower electrodes to generate the plasma using a process gas. The controller controls the current through the at least one magnetic field source during the processing of the substrate, where the current is based on a target value corresponding to at least one characteristic of the one or more active magnetic fields.