Characterization of Inductively Coupled Plasma Driven with Ferrite Cores at 400 kHz

Summary form only given. A very effective inductively coupled plasma (ICP) source free of capacitive coupling and transmission line effect is developed according to Godyak´s concept. The discharge is driven via six toroidal ferromagnetic cores whose primary windings are connected to an RF power source operated at 400 kHz. The source operates in a wide range of the input RF power, thus, it is able to generate plasma density in a wide dynamic range (over two orders of magnitude. In reported experiments, the RF power delivered to plasma was up to 3 kW at the input RF voltage less than 300 V and the input RF current less than 20 A. Due to mainly resistive input impedance, the power factor of such ICP is close to 1 and the input voltage and current are order of magnitude less than in the similar wattage conventional ICP system operating at 13.56 MHz. The measured power factor (cos square) was more than 0.8 and the power transfer efficiency was more than 90%. Plasma parameters, the plasma density and electron temperature were obtained as appropriate integrals of the measured electron energy distribution functions (EEDF). At 2 mtorr of argon gas, the electron density was found to be twice of that at 13.56 MHz, while the electron temperature was found to be nearly the same (about 3 eV) in both ICPs. A twice less the plasma potential (15 V) was found in ICP driven with ferromagnetic cores at 400 kHz than that in the conventional ICP driven at 13.56 MHz. It seems that ICP with ferromagnetic cores has a great potential as a plasma source for next generation plasma processing