Process Variation-Induced Contact Resistivity Variability in Nanoscale MS and MIS Contacts

This article presents contact resistivity variability (CRV) in metal-semiconductor (MS) and metal-interfacial layer (IL)-semiconductor (MIS) contacts on Ge and Si source/drain regions resulting from process-induced random dopant fluctuation (RDF) and IL thickness variation (ILTV). CRV is modeled by combining the effect of RDF and ILTV in statistical simulations incorporating Fermi-level pinning physics. CRV is also shown to have a direct and significant impact on 7-nm FinFET on-current variability. The choice of contact architecture depends strongly on the source/drain doping. RDF dominates at low doping and MIS contacts provide lower CRV as well as lower resistivity (ρc) due to a lower contact barrier height. Impact of RDF decreases and that of ILTV increases with increasing doping resulting in lower CRV with comparable ρc for MS contacts.