Abstract
An investigation of the electrical and microstructural characteristics of the Ti contact on silicon has been carried out. The presence of As in Ti/n + -Si samples was found to retard the formation of polycrystalline silicide (p-silicide) compared with that in Ti/p + -Si samples with BF 2 + implantation. Amorphous interlayers (a-interlayers) were found to be present in both Ti/n-Si and Ti/p-Si samples annealed at temperatures of and lower than 450 °C. Although the Schottky barrier heights (SBH's) vary for about 0.05-0.08 eV for samples annealed over a temperature range from room temperature to 900 °C, SBH's at the a-interlayer/n-Si and a-interlayer/p-Si were measured to be about 0.52-0.54 and 0.59-0.57 eV, respectively. The specific contact resistance (ρ c ) in the Ti/n + -Si system was measured to be the lowest with a value of 1.4×10 -7 Ω cm 2 when the a interlayer is present. In Ti/p + -Si system, the minimum ρ c is about 3×10 -7 Ω cm 2 . The variation in contact resistance with annealing temperature for both Ti/n + -Si and Ti/p + -Si samples is correlated to the change in dopant concentration beneath the contacts as well as microstructures. In the temperature regime where the a interlayer is in contact with the silicon substrate, the junction diode leakage current densities (J leak 's) are considerably lower than those in samples annealed at higher temperatures. The J leak at -6 V reverse bias is lower than 1 nA/cm 2 . The breakdown voltage is about 14 V (16 V) for the n + /p (p + /n) junction. The thickness of consumed Si is less in samples annealed at low temperature, and the a-interlayer/Si or p-silicide/Si interface is accordingly farther away from the junction as well as the end-of-range defects. The interface of p-silicide/Si is rougher than that of a-interlayer/Si. In addition, the roughness of the p-silicide/Si interface increases with annealing temperature. For both p + /n and n + /p junctions annealed at 900 °C, rough p-silicide/Si interfaces are thought to lead to spiking and increase the leakage currents.