Fabrication of conical micropore structure on silicon nitride/silicon using focused ion beam milling for biosensor application

We report the fabrication of conical shape micropore structures on silicon nitride/silicon (Si3N4/Si) substrate to function as a fluidic channel as well as a supporting structure for sensing membrane. Excellent shape of conical structure with large diameter of top hole size and small diameter of bottom hole size (1–2 μm) was successfully fabricated by utilizing a combination of grinding process, fine polishing and multistep focused ion beam (FIB) milling. A so-called re-deposition phenomena seems to be unavoidable in the multistep FIB milling resulted to the formation of tip-like structure at every milling step. Low surface roughness is effective in improving the shape of circumference of the milling area. The possibility to integrate such conical shape structure with graphene was also demonstrated. This result opens up the breakthrough towards new generation of analytical platform for biosensor application.