Measurement of Absolute Carbon Atom Density in Reactive Plasmas using Vacuum Ultraviolet Absorption Spectroscopy with Microdischarge Hollow Cathode Lamp

Carbon atoms play an important role in the reactive plasma processes such as carbon nanostructure formation, etching and so on. In order to realize the smart plasma processing, it is very important to measure the absolute C atom density in the process plasma using carbon based gasses, because the C atoms have a high sticking coefficient. We have developed a measurement technique for absolute C atom densities using a vacuum ultraviolet absorption spectroscopy (VUVAS) employing a microdischarge hollow cathode lamp (MHCL). Helium gas containing a small amount of CO$_{2}$ gas was used as the gas of the MHCL. The transition lines 2p3s$^{3}$p$_{2}$-2p$^{23}$P$_{2}$ at 165.7 nm were used for C atom measurements. By using VUVAS system, we measured the absolute C atom density in the CO-ICP at the pressure of 8.0 Pa. The densities increased from 1.7x10$^{11}$ to 9.5x10$^{13}$ cm$^{-3}$ when the RF power increased from 10 to 1000 W. his measurement method will be useful for the plasma processing for synthesize a diamond like carbon, carbon nanotube and so on.