Novel low-frequency oscillation in a radio-frequency inductively coupled plasma with tuned substrate

Abstract

The rf self-bias on the substrate in a rf inductively coupled plasma is controlled by varying the impedance of an external tuning inductor and capacitor network inserted between the substrate and the ground. In term of variations of tuned substrate self-bias (Vtsb) with tuning capacitance (Ct), three characteristic regions, namely continuous, instable, and bistable regions are found, corresponding to low, moderate, and high discharge power at a constant gas pressure, respectively. A novel self-oscillation observed in the instable region occurs only within a limited domain of Ct. With the increment in Ct, the self-oscillation frequency increases while its amplitude decreases. Near the boundary of the instable and bistable regions, the self-oscillations shift downward and upward at lower and higher Ct, respectively. The possible mechanism for the self-oscillation is discussed.