Highly selective ZEP/AlGaAs etching for photonic crystal structures using Cb/HI/Xe mixed plasma

We demonstrate the highly selective etching of AlGaAs photonic crystal (PhC) structures with electron beam (EB) resist masks by using Cl ₂/HI/Xe mixed plasma. We found that the Cl₂/HI plasma etches the AlGaAs layer while suppressing EB mask etching, and the addition of Xe eliminates damage to the EB mask caused by radicals. With this balanced approach, we achieved a 3-fold increase in the etching selectivity of the etching rate ratio of AlGaAs/resist. Moreover, using these conditions we successfully fabricated an AlGaAs PhC slab with a fine structure and very small air holes that had a radius of 48 nm and a lattice constant of 240 nm.