A process chamber for detecting formation of plasma during a semiconductor wafer processing, includes an upper electrode, for providing a gas chemistry to the process chamber. The upper electrode is connected to a radio frequency (RF) power source through a match network to provide RF power to the wafer cavity to generate a plasma. The process chamber also includes a lower electrode for receiving and supporting the semiconductor wafer during the deposition process. The lower electrode is disposed in the process chamber so as to define a wafer cavity between a surface of the upper electrode and a top surface of the lower electrode. The lower electrode is electrically grounded. A coil sensor is disposed at a base of the lower electrode that extends outside the process chamber. The coil sensor substantially surrounds the base of the lower electrode. The coil sensor is configured to measure characteristics of RF current conducting through the wafer cavity. The characteristics of the RF current measured by the coil sensor are used to confirm presence of plasma within the wafer cavity.