Capacitively coupled plasma is a plasma generated between two electrodes while reactive gases are fed into the chamber. The electrodes form the parallel plates of a capacitor and hence the resulting plasma is called a capacitively coupled plasma. RF power is applied to one of the electrodes while the other is grounded. In this mode, ions are accelerated from the plasma toward the powered electrode. The potential difference between the plasma and the powered electrode is the bias voltage. If the substrate is placed on the powered electrode, then the substrate experiences the bias voltage and the reactive ions as well as other reactive species from the plasma causes etching of the substrate. The resulting process is called the reactive ion etching. If the substrate is placed on the grounded electrode, then the reaction is mainly caused by reactive neutral species as the voltage across the sheath is very small (less than about 50V). This mode of etching is called the plasma mode etching.
