Effect of phosphorus doping on the performance of Au/Si inter-diffusion

In this work, both phosphorus doped and undoped Au/Si contact structures were investigated by scanning electron microscope (SEM) and Rutherford backscattering spectrometry (RBS) analysis after annealing at 350°C for 30 min. The effect of phosphorus doping on the performance of Au/Si inter-diffusion is discussed in this paper. The SEM image of the undoped Au/Si contact structure revealed that inverted pyramid-shaped diffusion outline formed at the contact interface after annealing due to the non-uniformity and anisotropy of Au/Si inter-diffusion. However, when the crystal Si substrate was heavily phosphorus doped by ion implantation, the inverted pyramid-shaped outline was eliminated and a smooth contact interface was obtained. In addition, RBS analysis showed that the average diffusion depths in both cases were nearly the same, which indicates the phosphorus doping can alter the anisotropy of Au/Si interdiffusion but has no significant influence on the Au/Si interdiffusion rate.