Formation of 15nm scale Coulomb blockade structures in silicon by electron beam lithography with a bilayer resist process

Abstract

We have formed Coulomb blockade structures with widths of 15–30nm in silicon-on-insulator (SOI) by electron beam lithography (EBL) in a bilayer resist process. The bilayer structure consisted of HSQ (hydrogen silsesquioxane) and AZ organic resist. The organic resist protects the buried oxide and allows removal of exposed HSQ features with hydrofluoric acid (HF). Measurements at 4.2K show pronounced Coulomb blockade signatures for 15nm wide wires. This bilayer resist process provides direct lithographic access to 15nm level features in SOI without the need for size reduction by oxidation.