Optical measurement of pulsed plasma produced by combined RF and HV pulses

Optical emission from plasmas of hydrocarbon gases was measured with a photomultiplier and an optical multichannel analyzer in a hybrid system of plasma-based ion implantation and deposition (PBII&D). In the PBII&D system, a RF pulse for plasma generation was applied to a substrate of trench structure together with a negative high-voltage (HV) pulse for ion implantation. The negative HV pulse with a voltage of −20 kV and the pulse width of 5 μs was applied at 50 μs after turning off of the RF pulse. The strong optical emission from the hydrocarbon plasma in the rectangular trench was observed at the same time as the application of the negative HV pulse. Intensity of optical emission from the HV pulsed plasma became stronger in a deeper trench, indicating the plasma generation in the trench by a hollow cathode effect. The optical spectra from CH (430.0 nm), Hα (656.2 nm) and Hβ (486.1 nm) were dominant in the HV pulsed plasma of methane, acetylene and toluene gases.