Contact resistance: Al and Al–Si to diffused N+ and P+ silicon

Prealloy and postalloy contact resistances at [(Al–Si)/bulk (100)Si] interfaces have been measured for a range of Al–Si alloy compositions (0–2 at.% Si), alloying temperatures (325–550 °C), and contact sizes (3–5 μm). Contact doping for n+/p junctions was by diffusion from a POCl3 source; for p+/n junctions, by diffusion from a BN source. Al–Si deposition was by S–Gun■ magnetron sputtering. Statistical distributions of prealloy contact resistance to n+ Si were found to provide highly sensitive monitors of contact cut and deposition-system cleanliness.. Minimum postalloy contact resistance values were independent of Al–Si alloy composition, and silicon pitting in the contact cut was not required to achieve good Ohmic contact. The maintenance of consistent, low-resistance Ohmic contacts throughout postalloy processing was found to depend on the silicon concentration in the aluminum being high enough to keep the aluminum supersaturated during all postdeposition temperature cycling.