SiO2/c-Si Bilayer Electron-Beam Resist Process for Nano-Fabrication

We have developed an SiO2/c-Si bilayer electron beam resist process in order to overcome the problems encountered in our previously developed SiO2/poly-Si resist system. The process parameters which include the electron beam exposure conditions, thicknesses of resist layers, etching of SiO2 and c-Si by using buffered HF solution and NMD-3 solution, respectively, are optimized. The developed SiO2/c-Si EB resist system is used to produce a suspended mask structure with an opening of 12 nm width for the double angle deposition of Ti for our proposed ultrasmall metal-insulator-metal tunnel junction fabrication process. We have also demonstrated the successful lift-off of inorganic resist by removing underlying c-Si layer of 40 ×40 µ m2 area using NMD-3 solution at 70° C, leaving an array of isolated Ti–TiO x –Ti dots, each having few hundred nm2 area, on the substrate.