SIO2 POLY-SI MULTILAYERED ELECTRON-BEAM RESIST PROCESS FOR FABRICATION OF ULTRASMALL TUNNEL-JUNCTIONS/

We have developed an SiO2/poly-Si multilayered electron beam resist pr ocess in order to overcome the resolution limit in conventional polyme r electron beam resists and to form suspended masks for ultrasmall met al-insulator-meta1 tunnel junction fabrication. Using a solution of bu ffered HF and a mixed solution of HNO3 and HF as etching solutions for SiO2 and poly-Si, respectively, suspended masks for metal depositions were produced. Utilizing a multiple-angle deposition-oxidation-deposi tion method, we have realized an ultrasmall Al/Ai(2)O(3)/Al tunnel jun ction array which exhibits a clear Coulomb staircase in the current-vo ltage characteristics at 12 K.