Characterization of Shallow p⁺(bf₂)/n Junctions with Tisi₂

This paper investigates the fabrication of titanium silicided shallow p⁺/n junctions by BF₃ implantation and diffusion. The implant dose and energy are fixed at 2 x 10¹⁵ cm^-2, 20 keV. We investigate the effect of various furnace and rapid thermal annealing (RTA) cycles on the dopant profile and the junction depth by secondary ion mass spectroscopy (SIMS). We also report on reverse bias diode leakage of the —1800 A deep junctions with a background concentration of 10¹⁷ cm^-3 P, below —500 Å thick TiSi₂. Low leakage diodes are made by either furnace annealing at 850°C or RTA at 1050°C. However, the RTA is preferred over the furnace annealing because more B dose is active in the underlying Si. Shallower junctions are made by several techniques. Junctions made with Ge preamorphization are —200 Å shallower than those made without preamorphization. However, the diode leakage of the preamorphized diodes is significantly higher. Low temperature (500°C) recrystallization of the BF₂-implanted Si before furnace diffusion results in junctions which are shallower by —300 A. Recrystallization has a negative effect on the junctions made by the preferred RTA process.