NiSi/p⁺-Si(n⁺-Si)/n-Si(p-Si) Diodes With Dopant Segregation (DS): p-n or Schottky Junctions?

Abstract

Dopant segregation (DS) technique has been extensively employed to tune Schottky barrier heights (SBHs) of NiSi/Si diodes, either leading to reduced specific contact resistivity ( $\rho _{\text {c}}$ ) in source/drain (S/D) Ohmic contacts, or enhanced current drivability in Schottky barrier S/D MOSFET (SB-MOSFET) where metallic NiSi is employed as S/D. A capacitance–voltage ( ${C}$ – ${V}$ ) method is usually adopted to reliably extract the SBHs of NiSi/Si for investigating the effectiveness of such a DS technique. In order to avoid large reverse leakage current which rules out the possibility of SBHs extraction during ${C}$ – ${V}$ measurements, dopants with opposite polarity to that in epitaxial Si substrate segregate at the NiSi/Si interface, for instance, boron DS (B DS) for NiSi/n-Si and arsenic DS (As DS) for NiSi/p-Si. This, however, raises one critical question, i.e., NiSi/p+-Si (B DS)/n-Si and NiSi/n+-Si (As DS)/p-Si are p-n or Schottky junctions. In this work, a dedicated circuit is devised to distinguish the type of as-fabricated NiSi/Si diodes with DS based on different switching mechanisms between p-n and Schottky junctions.