High-speed plasma diagnostics based on the floating harmonic method

With the recent use of pulsed RF plasma in etch processes, a high-time resolution diagnostic method is required. To monitor the plasma in real-time , a high-speed plasma diagnostic method based on the floating harmonic method (FHM) is proposed. The conventional FHM is a diagnostic technique to obtain ion density and electron temperature by applying a sinusoidal voltage to a floating probe, and its frequency is usually kHz range. In this work, we increased frequency of the applied voltage to MHz range for high-speed plasma diagnostics. As the applied frequency to the probe is increased, harmonic currents increase abnormally. As we applied high frequency voltage to the probe, the additional currents flow through the ceramic sleeve of the probe. By subtracting the additional currents from the harmonic currents, the compensated results were in good agreement with measurements from the conventional floating harmonic method. The electron temperature and ion density of the pulsed plasma were also measured with high-time resolution.