An automated system for DC and RF plasma characterization by guard double electric probes

Monitoring basic plasma parameters such as temperature (T), density (n), floating potential (Vf) or Debye length (λd) provides vital knowledge during the ion implantation processing of materials immersed in plasmas (PIII or PSII) generated either by DC or (13.56 MHz) RF sources. Thus, a fully automated electromechanical system has been designed and constructed on the basis of guard double electric probes in order to prevent both probe erosion and plasma contamination. The electronic components of the system comprise a ± 150 V triangular and ramp wave form generator capable of supplying ± 50 μA to ± 100 mA currents at 1-2000 Hz frequencies and a DAQ PCI-6023E data acquisition board with a 12 bit resolution compatible with LabVIEW graphic language. A program has been specifically developed for the latter in order to control the probe position within the discharge vessel and to capture, filter, visualize, process and store the respective information. The system has been experimentally applied to DC and RF plasmas of helium, argon, nitrogen, oxygen, and multiple gas mixtures with great success, inside several PIII reactors. Results are presented free from RF interference from the process itself or other surrounding sources.