RF SELF-BIAS CHARACTERISTICS IN INDUCTIVELY-COUPLED PLASMA

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 x 10(11) cm-3 was achieved for 12 cmphi 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 x 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.