IT-17-O-3384 Nucleation and lateral growth of NiSi phase

The Ni-based self-aligned silicide is widely used as contacts and interconnections in very large-scale integrated circuits [1]. They are obtained by solid state reaction between Ni thin film and Si substrate. Therefore, the fundamental mechanisms related to their formation, including the first stages of the nucleation, phase formation sequence, the growth kinetics, and the microstructures of the silicide, are of great interest for applications. NiSi is the desired phase in the Ni silicide sequence as the contact material in advanced integrated circuits [2]. However, a major disadvantage of NiSi is its degradation at high temperature. The addition of percent-wise Pt to Ni film increases significantly the stability of NiSi on Si substrates [3].
In this work, in situ-XRD annealing followed by atom probe tomography (APT) and in-situ transmission electron microscopy (TEM) analysis were used to study the reaction between 10 nm Ni (10% Pt) alloy film and Si(100) substrate. Isothermal annealing in in-situ XRD at different temperatures (200°C, 215°C and 230°C) have shown a nucleation-controlled behavior for NiSi growth at the epitaxial θ-Ni2Si/Si interface in contrast to the diffusion-controlled growth usually reported for NiSi [4]. TEM measurements have provided information about the NiSi nuclei shape and their distribution in the sample (Figure 1(a)) and additional information about the growth kinetics, while APT analyses were used to determine the 3D distribution of Ni, Si, and Pt atoms (Figure 1(b)). The Pt distribution was obtained in two cases: (1) in the θ-Ni2Si phase without the presence of NiSi nuclei and (2) inside the NiSi nuclei. A model for nucleation and lateral growth of NiSi at θ-Ni2Si/Si interface is proposed.

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