RF Self-Bias Characteristics in Inductively Coupled Plasma

Abstract

The plasma characteristics and RF self-bias behavior in inductively coupled plasma were studied. In the absence of magnetic field, a newly developed 1-turn antenna provided more uniform radial distribution of electron density than the spiral antenna with the present relatively small diameter, and uniformity of ±5% with 4.5×1011 cm-3 was achieved for 12 cmφ at 600 W. The electron density increased linearly with increasing power and did not saturate even at 1 kW input power. The ne of 7×1011 cm-3 was obtained in Ar at 1 kW power. For such high-density and large-diameter uniform plasma, the RF self-bias voltage was difficult to generate, because the sheath capacitance is too large. An equivalent circuit analysis clarified that the self-bias voltage behaved as Vpp4ne-2, where Vpp is RF voltage.