TiW as a direct contact material and a diffusion barrier to n+ and p+ implanted areas

Sputtered TiW(15/85 wt.%) has been investigated as a diffusion barrier layer between Al and Si and as a direct contact material to n⁺-and p⁺-doped silicon areas. Rutherford backscattering spectroscopy (RBS) in combination with reverse leakage current measurements on gated diodes were used to investigate the barrier properties of the deposited TiW films. TiW was observed to prevent intermixing between Al and Si up to 450 °C. Four terminal Kelvin resistor structures, implanted with different doses of As and BF2, ranging from 1E15 cm^-2 up to 1E16 cm^-2, were used to determine the respective contact resistivity. The actual surface doping concentration was determined by spreading resistance profiling (SRP). Contact resistance values well within the acceptable limit for VLSI processing were achieved.