Apparatus and methods for manipulating power at an edge ring in plasma process device

The present disclosure relates to apparatus and methods that manipulate the amplitude and phase of the voltage or current of an edge ring. The apparatus includes an electrostatic chuck having a chucking electrode embedded therein for chucking a substrate to the electrostatic chuck. The apparatus further includes a baseplate underneath the substrate to feed power to the substrate. The apparatus further includes an edge ring disposed over the electrostatic chuck. The apparatus further includes an edge ring electrode located underneath the edge ring. The apparatus further includes a circuit including a first variable capacitor coupled to the edge ring electrode.