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.
A study of the NiSi to NiSi2 transition in the Ni-Si binary system
Abstract The growth mechanisms of the transition from polycrystalline NiSi to single-crystal NiSi2 have been investigated. Samples were prepared by depositing Ni on 〈100〉 Si substrates by ultra high vacuum electron-beam deposition followed by vacuum annealing to form a silicide. Experiments were carried out at the transition temperature of 750°C for different annealing times. Rutherford backscattering spectroscopy (RBS), cross-sectional transmission electron microscopy (XTEM), scanning electron microscopy (SEM), Auger emission spectroscopy (AES) and X-ray diffraction (XRD) were employed with special emphasis placed on scanning and transmission electron microscopy. Cross-sectional examination in the transmission electron microscope reflects the coexistence of nickel monosilicide and nickel disilicide for samples annealed at 750°C. Scanning electron microscopy shows interesting surface morphology of samples in which island-like NiSi2 growth takes place in an NiSi thin film. Grain boundaries in the initial and final stages of NiSi2 formation are characterized by holes which extend from the surface to the silicon substrate. A mechanism is proposed to account for these observations by involving the following: lattice diffusion of Ni into the Si substrate, the conversion of NiSi grains to NiSi2 via nucleation and diffusion processes and lateral grain growth resulting in accumulation of vacancies on grain boundaries resulting in holes.
Analytical studies of nickel silicide formation through a thin Ti layer
Abstract Interfacial reaction sequences of a Ti Ni diffusion couple on Si were studied by cross-sectional TEM. At all stages of temperature treatment an amorphous interlayer was observed. There is a small window of annealing parameters where epitaxial growth of disconnected NiSi2 islands can be obtained. By further annealing NiSi forms. Principal component analysis (PCA) based AES depth profiling confirms these findings. High energy RBS with 15N4+ ions was successfully applied to study the interdiffusion processes taking place in the whole Ag/Ni/Ti metal multilayer system.