Experimental investigation of a pulsed linear inductively coupled plasma

Abstract

Summary form only given. Inductively coupled plasmas (ICP) employing linear antennas have gained a great deal of interests recently for applications in large area plasma processing tools. On the other hand, plasma sources operated in pulsed mode are also very attractive since they allow a wider range of tunability of relative concentration of reactive species and/or plasma uniformity. In this work, we experimentally characterized a pulsed linear ICP, excited by 13.56 MHz rf power through a 40 cm long cylindrical coaxial antenna formed by a 6 mm diameter copper tube and a 5 cm diameter quartz tube, by measurements using a Langmuir probe. To acquire the temporal behavior of the pulsed ICP, the probe was operated under a special mode. The time dependence of current collected by the probe was recorded for different probe bias voltages by using a high speed digital oscilloscope. The data are then reconstructed to obtain current vs voltage at different time of the pulsed rf power for analysis to obtain temporal behavior of plasma parameters such as plasma density, electron temperature, and plasma potentials, etc. The measurements were carried out to obtain the specialprofile of plasma parameters from the linear antenna. Measurement results show that plasma density first increases and then decreases if the probe is moved away from the antenna, although the rf field is higher near the antenna surface. This is a result of higher loss rate of charge species there due to diffusion loss on surface. Detailed temporal behavior of the pulsed ICP will also be presented.