Silicidation in Ni-Si System
Silicide formation induced by thermal annealing in Ni/Si thin film system has been investigated using glancing incidence X-ray diffraction. Silicide formation takes place at 600degC with Ni2Si, NiSi and NiSi2 phases co-existing with Ni. Complete conversion of intermediate silicide phases to the final NiSi2 phase takes place at 900degC. A comparison of the experimental results in terms of annealing temperature, Ni thickness, and dopant impurities with Ni-Si phases is presented. Nickel silicide (NiSi) is emerging to be the choice material for contact application in semiconductor device processing for sub_65 nm technology node and beyond. The focus of present work is to facilitate better understanding of the influence of thermal budget on nickel silicide solid-state reaction. Requirements for low temperature anneal and improving within wafer sheet resistance uniformity pose challenges for conventional lamp-based rapid thermal processing (RTP) due to lamp response effects on temperature controllability. Evolution of the nickel-rich silicide phase as a function of temperature is recorded using X-ray diffraction (XRD) techniques. It is postulated that lowering the Ni2Si/Si interface energy favors the delay of the agglomeration of the NiSi.
Improved control of silicon nanowire growth by the vapor–liquid–solid method using a diffusion barrier layer between catalyst and substrate
Abstract Vapor–liquid–solid (VLS)-grown nanowires are promising building blocks for next-generation devices because of their unique characteristics. Although Au is a widely used catalyst with the largest operable parameter window for Si nanowire growth by the VLS method, Au catalyst droplets diffuse at a high migration velocity over a Si substrate surface and agglomerate at relatively low temperature, thus degrading the uniformity of Au catalyst droplets and Si nanowires. Our aim is to improve the controllability of nanowire growth, positioning, and diameter, which are essential attributes for practical applications. To accomplish this, a diffusion barrier layer was inserted between the catalyst and substrate. Length and diameter uniformity were considerably improved for nanowires grown together with the formation of a silicide layer as a diffusion barrier.
Interfacial reaction barriers during thin-film solid-state reactions: The crystallographic origin of kinetic barriers at the NiS2/Si(111) interface
Epitaxial NiSi2 islands have been grown on Si(111) substrates by the direct reaction of nickel vapour with the silicon substrate in ultra-high vacuum at 400° C. Growth kinetics was shown to depend on the orientation of the islands: A-oriented islands grow about ten times faster than B-oriented ones, with the ratio of the advance rates of the main growth fronts even reaching 30. Applying plan-view transmission electron microscopy and high-resolution electron microscopy of cross sections, a corresponding difference was found in the structure of the NiSi2/Si(111) growth front: Steps at the B-oriented growth front were of three or six interplanar (111) spacings in height, whereas at the A-oriented growth front step-like defects of less than one interplanar (111) spacing in height were observed. These observations are explained by an atomic-scale model of the solid-state reaction, which involves the diffusion of nickel to the interfaces and the nucleation and subsequent lateral propagation of interfacial steps. The difference in the reaction kinetics originates from the presence of kinetic reaction barriers at the NiSi2/Si(111) growth fronts, the barrier at the B-front being higher owing to the lower formation rate of steps of triple atomic height than that of steps of lower height at the A-NiSi2/Si(111) growth front.