Nanoscale Schottky barrier mapping of thermally evaporated and sputter deposited W/Si(001) diodes using ballistic electron emission microscopy

Ballistic electron emission microscopy has been utilized to demonstrate differences in the interface electrostatics of tungsten-Si(001) Schottky diodes fabricated using two different deposition techniques: thermal evaporation using electron-beam heating and magnetron sputtering. A difference of 70 meV in the Schottky barrier heights is measured between the two techniques for both p- and n-type silicon even though the sum of n- and p-type Schottky barrier heights agrees with the band gap of silicon. Spatially resolved nanoscale maps of the Schottky barrier heights are uniform for the sputter film and are highly disordered for the e-beam film. Histograms of the barrier heights show a symmetric Gaussian like profile for the sputter film and a skewed lognormal distribution for e-beam film. A Monte-Carlo model is developed to simulate these histograms which give strong indication that localized elastic scattering is causing this skewing as forces the hot electrons to need a greater total energy to surmount the barrier. These differences are attributed to silicide formation from the unintentional substrate heating during the e-beam deposition, which is confirmed with transmission electron microscopy.