Anomalous Gate-Edge Leakage Current in nMOSFETs Caused by Encroached Growth of Nickel Silicide and Its Suppression by Confinement of Silicidation Region Using Advanced $\hbox{Si}^{+}$ Ion-Implantation Technique

Abstract

The anomalous gate-edge leakage current in n-channel metal-oxide-semiconductor field-effect transistors (nMOSFETs), which is caused by the encroached growth of nickel silicide across the p-n junction, is first reported. Furthermore, this encroached growth, which is caused by the isotropic and rapid diffusion of Ni atoms during the silicidation annealing, is successfully suppressed by the advanced Si+ ion-implantation (Si-I.I.) technique. Using the Si-I.I. technique, both the anisotropic silicidation to the perpendicular direction and the phase transition from Ni2Si to NiSi are enhanced by the introduction of damaged layers into Si substrates, such as vacancy and amorphous Si layers, and as a result, the silicidation region is confined at the source and drain regions. In addition, we propose a new evaluation method for the quantitative analysis of the encroached growth based on its growth properties, namely, the variability of encroached growths, which is three standard deviations of the roughness at silicide edges. The usefulness of this simple analysis for a large number of nMOSFETs is also demonstrated.