Abstract: A method of forming angled structures in a substrate. The method may include the operation of forming a mask by etching angled mask features in a mask layer, disposed on a substrate base of the substrate, the angled mask features having sidewalls, oriented at a non-zero angle of inclination with respect to perpendicular to a main surface of the substrate. The method may include etching the substrate with the mask in place, the etching comprising directing ions having trajectories arranged at a non-zero angle of incidence with respect to a perpendicular to the main surface.