Asymmetric triangular grating profiles with 90° groove angles produced by ion-beam erosion

Authors:
  • LJL. F. Johnson
    L. F. Johnson
  • KIK. A. Ingersoll
    K. A. Ingersoll
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Abstract
A simple phenomenological model has been developed to account for the effects of redeposition during transverse ion-beam erosion of grating relief patterns on surfaces. The model predicts the evolution with time of an inclined facet in the substrate, and the dependence of the facet angle θr on angle of incidence of the ion beam, erosion rates of mask and substrate, and the geometrical parameters of the mask. The results are illustrated by calculation of the angular dependence of θr for AZ-1350 photoresist masks on GaAs and SiO2 substrates and for Ti on SiO2. A strong dependence of θr on mask intercept angle a is found, except for a limited range in angle of incidence of the ion beam. Combined with results derived previously, the facet angles θs and θr and the groove angle θg of the asymmetric triangular groove profiles produced in these systems have been determined. A groove angle of 90° cannot be obtained for AZ-1350 on GaAs and SiO2, but in appropriate conditions a 90° groove angle may be obtained in SiO2 with a Ti mask.

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