Aluminum-silicon ohmic contact on "shallow" {n +}/{p} junctions

In this work various technologies for contacts of Al on n ⁺Si have been experimentally investigated, particularly in view of their suitability to very shallow {n}/{p} junctions. Special test-patterns have been used to measure the contact resistivity, while diodes reverse current density has been checked to evaluate the junction leakage induced by the aluminum-silicon interaction during sintering. Best results are obtained by depositing a thin polysilicon layer on the front surface before the doping process and the Al evaporation. In this case both the requirements of low contact resistivity (< 10 ^-4 ohm · cm ²) and low junction leakage current are satisfied. Comparison with the conventional Al/Si and AgTi/Si ohmic contacts has been performed.