Evolution of grating profiles under ion-beam erosion.

Area of Science:

• Surface Science and Engineering
• Materials Science
• Ion Beam Processing

Background:

• Surface faceting during ion-beam erosion is a critical phenomenon in microfabrication.
• Understanding erosion profiles of grating relief patterns is essential for precise surface modification.
• Existing models often do not fully account for complex redeposition effects.

Purpose of the Study:

• To analyze the faceting phenomenon of ion-beam erosion on grating relief patterns.
• To determine the geometry required for specific facet inclinations.
• To investigate the influence of erosion geometry, shadowing, and redeposition on substrate profiles.

Main Methods:

• Theoretical analysis of ion-beam erosion geometry, defining angles ø and gamma.
• Development of expressions for facet generation in substrates, including shadowing effects.
• Experimental profiling of GaAs surfaces after photoresist mask erosion, varying parameters like ion beam divergence and substrate material.

Main Results:

• Faceting geometry was determined for producing single facets at prescribed angles.
• Experimental profiles in GaAs confirmed theoretical predictions but showed significant modifications due to redeposition.
• Redeposition effects differed between erosion transverse and parallel to grating lines, with buildup observed primarily in the parallel case.

Conclusions:

• The study provides a framework for predicting and controlling ion-beam erosion profiles.
• Redeposition significantly modifies surface topography, particularly under parallel erosion conditions.
• The analysis is broadly applicable to uniformly eroding materials, irrespective of their erosion rate's dependence on incidence angle.