Noninvasive method to measure the ion flux in capacitive discharge

Abstract

A noninvasive method to measure the ion flux from the current flowing through the substrate (substrate current) in a capacitive discharge is proposed. The substrate current consists of a displacement current and a conduction current. In a high frequency capacitively coupled plasma, the displacement current is usually much higher than the conduction current. However, the displacement current becomes negligible at a moment that the second time derivative of the substrate current becomes zero (the first time derivative reaches its minimum), and from the measured substrate current at that time, the ion flux can be obtained. The measured ion flux from this method is compared with the flux measured by another diagnostic method.