Comparison of spatial distributions of atomic oxygen and hydrogen in ICP by means of catalytic probes and actinometry

Low pressure inductively coupled plasma was investigated with a combination of two diagnostic techniques: catalytic probes and optical emission spectroscopy (actinometry). Three working gases were used: oxygen, oxygen-argon mixture and hydrogen. Concentrations of oxygen and hydrogen atoms were determined in a wide range of plasma parameters, with pressure ranging from 10 Pa to 70 Pa, applied power in the range from 50 to 250 W and at many different positions throughout the system (including the coil and afterglow in sample chamber). Concentrations of oxygen atoms were measured to be 1.3 × 1015 cm−3 in the middle of the coil and 4 × 1012 cm−3 in the regions of the chamber furthest from the coil. These spatially resolved concentrations are very important in plasma processing of materials, because radical concentrations over the sample determine plasma-material interactions. This work demonstrates that a relatively simple detection system can be practical and sufficiently successful in many plasma applications.