DIVERGENCE MEASUREMENTS FOR CHARACTERIZATION OF THE MICROPATTERNING QUALITY OF BROAD ION-BEAMS

For characterization of the micropatterning qualities of broad ion beam systems we introduce the concept of internal divergence in terms of the ion incidence angle distribution at a point of the processing plane. Methods for determination of this quality are discussed, and measurements are carried out for argon and oxygen for two different ion beam systems. Internal divergence is measured with a two-stage Faraday cup assembly. Results for the divergence angle range from 3° to 9° for Ar as an operating gas, and the values for O2are 10%-20% lower and show the same dependence on operating conditions of the source. Internal divergence within the beam center region is in good agreement with measured divergence values from literature, but deviates at the beam periphery. Divergence angles there are different primarily due to the discharge chamber plasma inhomogeneity. At high angular resolution of the two-stage cup the beamlet structure of a broad beam can be revealed in both ion beam density and ion incidence angle. Consequences for the processing parameters of ion beam systems in micropatterning are deduced. Local measurement of the internal divergence within the processing plane turns out to be an adequate characterization of an ion beam system for large area etching applications. © 1990, American Vacuum Society. All rights reserved.