Embodiments described herein relate to methods and apparatus for forming gratings having a plurality of fins with different slant angles on a substrate and forming fins with different slant angles on successive substrates using angled etch systems and/or an optical device. The methods include positioning portions of substrates retained on a platen in a path of an ion beam. The substrates have a grating material disposed thereon. The ion beam is configured to contact the grating material at an ion beam angle ϑ relative to a surface normal of the substrates and form gratings in the grating material.