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 4.5×10 11 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 n e of 7×10 11 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 V pp 4 n e -2 , where V pp is RF voltage.