ANOMALOUS JUNCTION LEAKAGE BEHAVIOR OF TI SELF-ALIGNED SILICIDE CONTACTS ON ULTRA-SHALLOW JUNCTIONS

An anomalous junction leakage is observed in Ti self aligned silicide (Ti-SALICIDE) contacts on ultra-shallow junctions less than 0.1 mu m. After annealing at around 460 degrees C for 30 min, the leakage curren t increases considerably for n(+)/p junctions and decreases slightly f or 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 anne aled at 460 degrees 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 expl ained by a tunneling current. The results of secondary-ion mass spectr oscopy (SIMS), transmission electron microscopy (TEM) and energy-dispe rsive X-ray spectroscopy (EDX) analyses indicate that a considerable a mount of Ti diffuses into n(+)-Si at around 460 degrees C. However, on ly 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 rep resent the process in the early stage of Ti silicidation.