Power absorption characteristics of an inductively coupled plasma discharge

Power absorption characteristics of an inductively coupled discharge are investigated experimentally and compared with a two-dimensional inductive heating theory in a planar single turn antenna at high frequency (18 MHz) and low pressure (/spl les/50 mtorr) conditions. We measure the resistance R, which consists of vacuum resistance R/sub /spl nu// and the plasma resistance R/sub p/ for a given RF power of P= 1/2 I/sub c//sup 2/R, where I/sub c/ is the coil current. The vacuum resistance is determined to be 0.44 R in our case. The plasma resistance increases as the gas pressure increases in a pressure range of 2 to 50 mtorr. Also, it increases with power. In a high-pressure range near 50 mtorr, however, it has a nearly constant value of about 0.6 /spl Omega/.