Dot lithography for zero‐dimensional quantum wells using focused ion beams

A 50‐keV focused Ga+ beam formed in a two‐lens microprobe column with prefinal lens deflection was used to expose dot arrays in a negative acting bilevel resist. Dot arrays 600 μm×600 μm with 600‐A‐diam resist posts on 0.6 μm centers (incorporating 1024×1024 dots) were fabricated with ion exposure times of 18 s. By reducing the beam dwell time by a factor of 2, roughly 300‐A‐diam posts were fabricated. Since the ions stop in the bottom resist layer and do not enter the substrate, the optical properties of underlying material should not be altered by damage from the exposure process.