Reproducibility of a Plasma Production in a Fast- and Automatically-controlled Radio Frequency Plasma Source

Reproducibility of the plasma production by using a fast- and automatically-controlled radio frequency (RF) plasma source with a magnetic field is investigated, where a frequency-tunable RF generator including a controller board is used to supply the RF power to the plasma source. The pulsed RF plasma with a pulsewidth of 200 ms is repeated by 500 shots and the data are statistically analyzed. It is demonstrated that the impedance matching is typically accomplished within about 5 ms, and the power ratio of the reflected power to the forward power can be reduced to less than 0.1. Furthermore, the optical emission intensity from the plasma is successfully stabilized by incorporating the automatic adjustment of the output RF power, providing the nearly constant net power being the forward power minus the reflected power, even if the reflection coefficient temporally varies. Therefore, the fast- and automatically-controlled RF system is useful for the repetitively pulsed RF plasma production.