Optical emission spectroscopy for analysis of broad ion beams

In sputter etching and reactive ion beam etching (RIBE), contamination and disturbance free in situ methods are desired for control of etch relevant quantities like energy and angular distribution of particles. These requirements cannot be fulfilled by the conventional electrical methods. In this paper we show that optical emission spectroscopy is a valuable tool for in situ diagnostics of broad ion beams. We report on measurements in Argon ion beams of 300 - 1000 eV energy. Several emission lines of fast and slow atoms and ions are detected in the wavelength range 4000 - 7000 Angström at a resolution of better than 0.1 Angström. Impact of fast particles and electrons on neutral background gas atoms are specified as main excitation mechanisms. From the Doppler-shifted emission lines we obtain information on energy and angular distribution of the beam particles.