Silicide formation in contacts to Si nanowires

Silicides, intermetallic compounds formed by the reaction of a metal and Si, have long been used as contacts for metal oxide semiconductor (CMOS) transistors and have more become interesting for other Si nanowire (SiNW) devices. In the following, experimental results for the Ti, V, Pt, Pd, Fe, and Ni–Si systems are reported and placed in the context of prior work on silicide formation from metal films on Si wafers. For the early transition metals Ti and V, the silicide is formed only underneath the contact pad and is Si-rich (MSi2). For the middle transition metal Fe and late transition metals Pt and Pd, a metal-rich silicide was the first phase observed to form, but poor morphologies were common, making it a challenge to incorporate these contacts into nanowire devices. Nickel contacts were the only ones with well-behaved axial silicide growth away from the contact pad, and silicide formation was strongly dependent on the original SiNW orientation. These findings are discussed in terms of kinetic features of the metal-SiNW systems.