Silicided Au/Ni bilayer on p-type [001] silicon for low contact resistance metallization schemes

Rear contact terminals of integrated circuits have to satisfy electrical and mechanical requirements, such as low specific contact resistance, good adhesion to the substrate and good solderability with external elements. A new metallization scheme, made of sputtered Ni and Au layers, with the addition of a process step needed to ensure nickel silicide formation at low temperature, has been proposed for p-type silicon substrates and investigated in this work. Its electrical and structural properties have been compared with conventional Cr/Ni/Au and Ti/Ni/Au contacts, showing lower specific contact resistance values (rho(c)), an ohmic behaviour in the explored range of resistivity (i.e. 3 m Omega cm < rho < 18 m Omega cm) despite of the rectifying one of conventional materials, better adhesion with the substrate and limited consumption of nickel and silicon during the reaction process. The proposed metallization scheme provides an effective solution to meet both electrical and mechanical requirements with a single material, with a consequent reduction of logistic and economic effort to realize integrated circuits.