Radio frequency hollow cathode jet: optical emission study

Hydrogen radicals are crucial for: remote plasma enhanced chemical vapor de position; metal-organic chemical vapor deposition; or plasma cleaning. A ne w type of 13.56 MHz hollow cathode jet shows high efficiency of radical gen eration. For better understanding of plasma heating mechanisms, the source is characterized by optical emission spectroscopy from hydrogen plasma in t he wavelength range from 200 to 800 nm. The examined parameter range was: p ressure from 0.1 to 4 torr; gas flow up to 100 sccm; and rf power from 20 t o 180 W. The emission intensity in the jet zone is 2 orders of magnitude hi gher than in the anode or cathode zone. The axial emission intensity distri butions in the remote zone indicate the propagation and absorption of rf po wer along the remote plasma column. The emission intensities of lines relat ed to C(1)pi (u)-XA(1)Sigma (+)(g) transition, are compared og with the int ensities of H-alpha, H-beta and H-gamma atomic lines. The molecular-to-atom ic emission intensity ratio increases with increasing pressure and with inc reasing distance from the plasma source, due to the increase of vibrational excitation. (C) 2001 Elsevier Science B.V. All rights reserved.