Fabrication and properties of dot array using electron-beam-induced deposition

Electron-beam(EB)-induced deposition using precursor molecule of WF6 is applied to making metal/insulator/metal tunnel junctions for single electron transport devices. The SiO2 substrate pre-treated by oxygen plasma is contaminated with hydro-carbon material and the deposits show rapid decrease in resistance with the increase in EB dose and higher resistivity of about 100 Ohm cm at 300 K which decreases by 20% at 130 K. In contrast, the thickness of deposits on clean substrates is 1/20 as small as the case of contaminated substrate for the same exposure dose. Also deposits with a lower resistivity of 4x10(-3) Ohm cm can be obtained. Under such deposition conditions, single electron transistor structure is fabricated which is composed of several dots connected to single line deposits with deposits for gate electrode 300 nm distant from the dot region. The source-drain voltage dependence of source current for 7 dots with 10 nm pitch exhibits Coulomb blockade characteristics at 12 K.