Second harmonic RF currents in a cylindrical ICP with a planar coil

Summary form only given. The possibility of non-linear effects in inductively coupled plasma (ICP) associated with RF components of the magnetic field is a subject of discussion in the current literature. It has been shown that the RF magnetic field changes the direction of electron acceleration and may modulate the plasma density and generate an RF field at the second harmonic in the skin layer of an ICP. Here we report on experimental observations of RF currents at the second harmonic J/sub 2/spl omega// directed orthogonal to the main azimuthal (/spl theta/) discharge current at the fundamental frequency J/sub /spl theta//spl omega//. Phase resolved measurement of the axial J/sub z2/spl omega//(r) and radial J/sub r2/spl omega//(z) components of the RF current density at the second harmonic have been performed with a magnetic (dB/dt) probe in an ICP driven at 3.39; 6.78 and 13.56 MHz in argon gas at 1, 10 and 100 mTorr. An independent measurement of J/sub z2/spl omega//(r) has also been made with a flat differential Langmuir probe maintained at the plasma potential. The measurements show that the second harmonic current is nearly proportional to the discharge power, inversely proportional to the square of the driving frequency and is falling with gas pressure.