The role of interfacial segregation and microstructure in interdiffusion between aluminum and silicon

In this investigation, we studied the interdiffusion behavior between polycrystalline silicon (poly-Si) and aluminum where the poly-Si was doped with antimony via ion implantation. Post sintering sample microstructure was determined by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and optical microscopy, and composition was determined by Rutherford Backscattering Spectrometry (RBS) and Scanning Auger Microscopy. As-implanted samples showed interdiffusion during sintering (465° C, dry N₂) independent of Sb concentrations up to 1.1 × 10²¹ cm^-3 near the Al/Si interface. In samples where the implantation damage was annealed out prior to sintering, interdiffusion is inhibited when the Sb concentration at the interface was above a threshold concentration of 7.3 × 10¹⁹ cm^-3. This threshold concentration is lower if the segregation of Sb is preserved prior to metallization. We propose that interdiffusion is inhibited by dopant (Sb) passivation of interfacial Si defects, the sites where interdiffusion is believed to initiate.