Finite metal-sheet-resistance in contact resistivity measurements: Application to Si/TiN contacts

The standard transmission line model cannot be applied to evaluate the contact resistivity of thin TiN layers on highly doped p⁺ and n⁺ substrates because the finite sheet resistance of the TiN must be accounted for. We present two ways to include this effect using existing analytical models. The results are shown to agree with measurements where the effect of the finite sheet resistance of TiN is eliminated with a metallic overlayer. With the help of these evaluation techniques, it is shown that the contact resistivity of TiN changes in opposite ways for p⁺ and n⁺Si after vacuum annealing at 600°C for 15 min. This result is consistent with an increase of the barrier height φ_Bn of the contact by ≅0.1 V to near midgap value.