Excitation mechanisms and ion kinetics in a 450 kHz capacitively coupled argon discharge

Low pressure RF plasmas are widely used in the microelectronics industry for the production of integrated circuits. External conditions, like pressure, power, geometry and driving frequency determine the properties of the plasma and thus its practical use in various applications. The influence of the applied RF frequency has been studied by several authors. When the driving frequency is in the order, or lower than the ion transit frequency across the sheath (~1 MHz), the discharge is then sustained by ionization due to the secondary electrons from the electrodes. We applied a 450 kHz RF voltage to a capacitively coupled parallel plate plasma reactor filled with 158 mTorr argon. Time resolved emission spectroscopy is used to study the excitation mechanism. The movement of the ions near the sheath edge is investigated with Doppler-shifted laser induced fluorescence (DSLIF). Langmuir probe and optical absorption spectroscopy are used to determine the ion density and the electron and neutral temperatures. The experimental results are compared with a 1D fluid model which includes both bulk and beam electrons (12 References).