Silicide formation and silicide-mediated crystallization of nickel-implanted amorphous silicon thin films

Abstract

The nucleation and growth of isolated nickel disilicide precipitates in Ni-implanted amorphous Si thin films and the subsequent low-temperature silicide-mediated crystallization of Si was studied using in situ transmission electron microscopy. Analysis of the spatial distribution of the NiSi2 precipitates strongly suggested the occurrence of site saturation during nucleation. NiSi2 precipitates were observed in situ to migrate through the amorphous Si thin films leaving a trail of crystalline Si at temperatures as low as ∼484 °C. Initially, a thin region of epitaxial Si formed on {111} faces of the octahedral NiSi2 precipitates with a coherent interface which was shown by high-resolution electron microscopy to be Type A. Migration of the NiSi2 precipitates led to the growth of needles of Si which were parallel to 〈111〉 directions. The growth rate of the crystalline Si was limited by diffusion through the NiSi2 precipitates, and an effective diffusivity was determined at 507 and 660 °C. A mechanism for the enhanced growth rate of crystalline Si is proposed.

Synthesis and properties of ferromagnetic nanostructures embedded within a high-quality crystalline silicon matrix via ion implantation and nanocavity assisted gettering processes

“…We attribute such reverse annealing phenomenon to the effects of nickel silicide mediated crystallization of the amorphous Si zones within the Ni implanted region. The nickel silicide precipitates formed during annealing can act as heterogeneous nucleation sites for displaced Si atoms to recrystallize; and as the silicide precipitates migrate, a trail of Si crystallites of needle-like morphology forms within the matrix, 19 which is also confirmed by our HRTEM morphology (Fig. 2(d)).…”

Characterization of the MIC/MILC interface and its effects on the performance of MILC thin-film transistors

“…Given the proposition that MILC is an "interfacial" process mediated by Ni diffusion across NiSi nodules at the crystallization front [4], [19], it is not surprising that neither Ni diffusion across the MILC region nor its diffusion into the a-Si region are the rate controlling steps in MILC. Interestingly, the MILC values extracted from the two different kinds of substrates, while significantly different from the 1.55 eV for NiSi formation and the 2.9 eV for NiSi degradation [20], are much closer to the value of 2.08 eV for Ni induced lateral secondary grain growth in poly-Si reported by Hong et al [20] and the 1.9 eV for Au induced poly-Si recrystallization reported by Allen et al [21]-who suggested that the activation energy could be attributed to the energy required to attach a Si atom to the growing crystallization front.…”

Metal-Induced Crystallization

“…The presence of excess metallic Ni at the bottom of the stack was attributed to the diffusion of the NiSi 2 nodules. Hayzelden et al (Hayzelden & Batstone, 1993) reported an in-situ transmission electron microscopy study on Ni induced aSi crystallization and suggested a similar mechanism for the diffusion of NiSi 2 in a-Si matrix. According to the mechanism proposed by these authors, Si first crystallizes on one of the eight faces of NiSi 2 crystalline seeds and then it dissociates as Ni and Si atoms at the c-Si/ NiSi 2 interface.…”