Ion-beam lithography is the practice of scanning a focused beam of ions in a patterned fashion across a surface in order to create very small structures such as integrated circuits or other nanostructures.
There is also a reduced potential radiation effect to sensitive underlying structures compared to x-ray and e-beam lithography.
In addition to diffraction being negligible, ions move in straighter paths than electrons do both through vacuum and through matter, so there seems be a potential for very high resolution.
Secondary particles (electrons and atoms) have very short range, because of the lower speed of the ions.
On the other hand, intense sources are more difficult to make and higher acceleration voltages are needed for a given range.