SHALLOW-JUNCTION DIODE FORMATION BY IMPLANTATION OF ARSENIC AND BORON THROUGH TITANIUM-SILICIDE FILMS AND RAPID THERMAL ANNEALING

We have studied the performance of diodes fabricated on n-type and p-type Si substrates by implanting As or B through a low-resistivity titanium-silicide layer. The effects of varying the implant dose, energy, and post-implant thermal treatment were investigated. After implantation, a rapid thermal anneal was found to be sufficient in removing most of the implant damage and activating the dopants, which resulted in n+-p and p+-n junctions under a low-resistivity silicide layer. The n+ -p junctions were as shallow as 1000 A with reverse leakage currents as low as 5.5 μA/cm2. A conventional furnace anneal resulted in a further reduction of this leakage. Shallow p+-n junctions could not be formed with boron implantation because of the large projected range of boron ions at the lowest available energy. Ti silicide films thinner than 600 A exhibited a sharp rise in sheet resistivity after a furnace anneal, whereas thicker films exhibited more stable behavior. This is attributed to coalescence of the films. High-temperature furnace annealing diffused some of the dopants into the silicide film, reducing the surface concentrations at the TiSi2-Si interface. © 1990 IEEE