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

Area of Science:

• Materials Science
• Surface Physics
• Microfabrication

Background:

• Ion-beam erosion is crucial for creating surface relief patterns.
• Redeposition of sputtered material can significantly alter pattern evolution and final geometry.
• Understanding these effects is key to controlling nanoscale surface structuring.

Purpose of the Study:

• To develop a phenomenological model for redeposition effects during transverse ion-beam erosion.
• To predict the time evolution of inclined facets and facet angles.
• To determine the dependence of facet angles on ion beam parameters and mask geometry.

Main Methods:

• Development of a simple phenomenological model.
• Calculation of facet angle evolution with time.
• Analysis of facet angle dependence on ion beam angle of incidence, erosion rates, and mask parameters.
• Application to specific mask/substrate systems (AZ-1350/GaAs, AZ-1350/SiO(2), Ti/SiO(2)).

Main Results:

• The model successfully predicts facet angle evolution and its dependence on various parameters.
• A strong dependence of the facet angle on mask intercept angle was observed, with exceptions.
• Facet angles (theta(S), theta(r)) and groove angles (theta(g)) were determined for asymmetric triangular groove profiles.
• Achieving a 90-degree groove angle was found to be impossible for AZ-1350 masks on GaAs and SiO(2).

Conclusions:

• The developed model provides a framework for understanding and predicting redeposition effects in ion-beam etching.
• Precise control over groove angles, including achieving 90 degrees, is possible under specific conditions (e.g., Ti mask on SiO(2)).
• The findings are valuable for optimizing fabrication processes for nanostructured surfaces.