Fabrication and characterization of vertical silicon nanopillar Schottky diodes

The authors report fabrication of vertical Schottky diodes using sub-100nm diameter n-type doped Silicon nanopillars. The nanopillars were fabricated using a top-down approach employing the Bosch process. Square-shaped islands of Silicon dioxide patterned using electron beam lithography and deposited by thermal evaporation acted as hard masks for vertical inductively coupled plasma (ICP) etching. Once formed, the nanopillars were conformally covered in a blanket layer of SiO₂ and their tips were exposed using Chemical-Mechanical Polishing. Nickel contacts were patterned and deposited on them using DC magnetron sputtering and were annealed to form Nickel silicide forming Schottky diodes with barrier heights between 0.6 and 0.7 eV. We have thus established a low temperature process (no thermal oxide required) for constructing vertical Silicon Schottky diodes with approximately circular cross-sections of diameters from 40nm to 100nm. The I_ON to I_OFF ratio was at least 10⁴. We also observed non-ideal current-voltage characteristics that differentiate these nanoscale diodes from planar Schottky diodes.