Mode transition and hysteresis in inductively coupled radio frequency argon discharge

Abstract

This contribution presents experimental results about the mode transition of an inductively coupled radio frequency (RF) (13.56 MHz) argon discharge at different total gas pressures. In particular, the positive ion saturation current and the line integrated electron density are measured by Langmuir probe and 160 GHz microwave interferometer, respectively. The mode transition strongly depends on the total gas pressure and can appear stepwise or continuously. The space resolved positive ion saturation current is separately shown for the E- and H-mode at different total gas pressures. Therewith, the pressure dependency of the RF sheath thickness indicates a collisional sheath. The hysteresis phenomenon during the E-H and the inverse H-E transition is discussed within the framework of the matching situation for different total gas pressures. The hysteresis width is analyzed using the absorbed power as well as the coil voltage and current. As a result, the width strongly increases with pressure regarding the power and the coil voltage in the E-mode and remains constant in the H-mode. In addition, the phase shift between the coil voltage and current shows a hysteresis effect, too.