Experimental investigation of power deposition and ionization kinetics in an inductively coupled discharge

Summary form only given. Inductively coupled discharges are of current interest because they may be applied to plasma processing, especially in the microelectronic device fabrication industry. The operating regime for these applications is at low gas pressure, where various characteristic lengths often supposed small, such as the electron energy relaxation length and mean free path, are in fact comparable with the relevant macroscopic lengths such as the size of the discharge chamber and the plasma skin depth. These circumstances typically produce departures from classical fluid behaviour such as non-ohmic electron heating and non-local ionization. In this paper we investigate the ionization kinetics in an inductively coupled in argon by determining both the time averaged power deposition into electrons and also the ionization source term. The experiment was conducted in a stainless steel cylindrical vacuum chamber of radius 10 cm and length 80 cm, into which a quartz tube of radius 2.5 cm and length 30 cm was inserted through a port in one of the end-plates. A Pyrex observation window formed the other end-plate. The quartz tube contained an eleven-turn helical induction-coil of length 10 cm and radius 2 cm. The coil was driven at 13.56 MHz and H mode discharges were formed in argon gas at pressures ranging from p 10 mTorr to a few hundred mTorr. These discharges had average densities /spl sim/10/sup 11/ cm/sup -3/ and effective electron temperature T/sub e//spl sim/1-2 eV. The power deposition was measured directly vis a B probe, while the ionization source term was obtained by inverting the plasma transport equation using a deconvolution method.