Anomalous Junction Leakage Behavior of Ti Self Aligned Silicide Contacts on Ultra-Shallow Junctions

Abstract

An anomalous junction leakage is observed in Ti self aligned silicide (Ti-SALICIDE) contacts on ultra-shallow junctions less than 0.1 µ m. After annealing at around 460° C for 30 min, the leakage current increases considerably for n+/p junctions and decreases slightly for p+/n junctions. At a reverse bias of 1 V, the activation energies of the leakage current for n+/p junctions and p+/n junctions annealed at 460° C for 30 min are 0.16 eV and 0.97 eV, respectively. The very small activation energy for the n+/p junction can be explained by a tunneling current. The results of secondary-ion mass spectroscopy (SIMS), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) analyses indicate that a considerable amount of Ti diffuses into n+-Si at around 460° C. However, only a small amount of Ti diffuses into p+-Si. This anomalous junction leakage can be explained in terms of tunneling assisted by traps due to the diffused Ti. These low temperature phenomena are thought to represent the process in the early stage of Ti silicidation.