ELECTRON-BEAM NANO-FABRICATION BY INORGANIC RESIST FOR MIM TUNNEL JUNCTION

This paper describes new developments of electron beam exposure system and fabrication process of metal/insulator/metal tunnel junctions for single electron transport using double-layered inorganic resist. The system has performances of 2.8 nm probe diameter with 127 pA at 50 kV accelerating voltage and the standard deviations of stitching and over lay errors are confirmed to be 14 and 18 nm, respectively for 320x320 mu n(2) chip size. The sample chamber is evacuated down to 2x10(-9) To rr with keeping the stage accuracy and also we can introduce a gas fro m the small nozzle near the sample surface up to 10(-4) Torr. A SiO2/p oly-Si on SiO2/Si substrate is used in order to produce a suspended ma sk for multiple-angle Al deposition with oxidation in 100 mTorr O-2 am bient. This process enables us to produce one-dimensional array of tun nel junctions with a nominal width of 40 nm. The current-voltage chara cteristics of this device show a clear Coulomb staircase with a voltag e period of 63 mV and a current step of 0.18 pA at temperatures of 12 and 20 K.