Effects of capping layers on the electrical characteristics of nickel silicided junctions

Abstract

In this paper, effects of capping layers on formation and electrical properties of Ni-silicided junctions have been investigated. Nickel silicide films using the Ti or TiN-capped layer process are used to compare to those by the uncapped process. The uncapped (Ni single layer) and TiN-capped samples are shown to exhibit better thermal stability than the Ti-capped samples. For the silicided junctions, samples using Ti capping layer processes exhibit larger leakage current densities. A high-resistivity NixTiySiz compound layer is formed on the surface during silicidation for the Ti-capped sample, while the uncapped and TiN-capped samples are not. In addition, it is found that the thickness of NiSi layer, as well as the NixTiySiz layer, increases with increasing the Ti capping layer thickness. The formation of NixTiySiz layer not only increases the contact resistance, but also deepens the silicide thickness. © 2007 Elsevier B.V. All rights reserved.