Characterization of nickel Germanide thin films for use as contacts to p-channel Germanium MOSFETs
We have measured the physical properties and resistivity of nickel germanide thin films formed by the rapid thermal annealing of nickel metal on p-type germanium substrates. Rutherford back scattering and high-resolution electron diffraction confirm that the stoichiometry of the resulting nickel germanide film corresponds to NiGe and has an orthorhombic unit cell with dimensions comparable to that of bulk samples. Transmission electron microscopy shows a poly-crystalline film structure with grain size > 0.1 /spl mu/m. The resistivity values for films annealed in the range 350/spl deg/C-500/spl deg/C are comparable to those of metal silicides. Measurements of the specific contact resistance suggest that values approaching 2 /spl times/ 10/sup -7/ /spl Omega/.cm/sup 2/ can be realized using NiGe formed on heavily doped p-type germanium.