Inter-diffusion, melting and reaction interplay in Ni/4H-SiC under excimer laser annealing

Abstract

We investigated the complex interaction between a nickel layer and a 4H-SiC substrate under UVlaser irradiation since the early stages of the atomic inter-diffusion. An exhaustive description is still lacking in the literature. A multimethod approach based on Transmission Electron Microscopy, Energy Dispersive Spectroscopy and Diffraction (electron and X-ray) techniques has been implemented for a cross-correlated description of the final state of the contact after laser irradiation. They detailed the stoichiometry and the lattice structure of each phase formed as well as the Ni/Si alloy profile along the contact for laser fluences in the range 2.4-3.8 J/cm 2. To make a bridge between process conditions and post-process characterizations, time dependent ultra-fast phenomena (laser pulse ≈160ns), such as intermixing driven melting and Ni-silicides reactions, have been simulated by a modified phase fields approach in the proper many-compounds formulation. We disclose that raising laser fluence has multiple effects: 1) the thickness of the silicide layer formed at the interface with 4H-SiC expands; 2) the silicon content into the reacted layer increases; 3) a Ni 2 Si phase is promoted at the highest fluence 3.8 J/cm 2 ; 4) silicon atomic diffusion into a topmost residual nickel layer occurs, with the Ni/Si ratio increasing towards the contact surface.

Simulations of the Ultra-Fast Kinetics in Ni-Si-C Ternary Systems under Laser Irradiation

“…This scenario is extremely rich, and the laser parameters can be properly tuned with the aid of our simulation results to obtain different composition and space distributions of the different phases, compounds and mixtures in view of technological applications. We notice that the eventual modifications of laser parameters (e.g., shorter pulses to increase further non-equilibrium conditions) could result in the formation of new metastable phases (e.g., Ni-C carbides, Ni-Si carbides or local inclusion of other pure elemental phases in addition to the C clusters) not evident in previous experiments [ 10 , 11 ] with the laser pulse shown in Figure 1 . In this case, the modular implementation of the model (Equations (1)–(18)) allows a fast implementation of the additional reactions and related equations necessary for simulation.…”

“…An experimental measurement of M Ni-rich ( ) and M Silicide ( ) for has been determined by transmission electron microscopy (TEM) for experimental laser annealing processes performed in the same conditions as the ones studied here (see Ref. [ 11 ]) and reported in Figure 10 as black crosses. Simulations and experimental analyses show a noteworthy agreement.…”

“…The increasing importance of silicon carbide (SiC) as an innovative semiconductor material for device applications has recently shifted the focus from Ni-Si to the Ni-Si-C ternary system. Indeed, also for SiC devices, Ni-silicides are key contact materials, and LA could be applied, again thanks to the localized heating features, as a thermal process for the contact formation [ 10 , 11 ]. Of course, the still immature simulation techniques, tentatively introduced in the case of Ni-Si systems, need to be completely readdressed when dealing with the simulation of the silicide formation kinetics on a SiC semiconductor substrate.…”

Multiscale Simulations for Defect-Controlled Processing of Group IV Materials

“…The simulated evolutions evidence a structured scenario which has been validated by the post-process characterization of the corresponding processes. For increasing value of the fluence, different stages occur (sub-melting, partial melting and full melting of the metal rich film) with the proper characteristics, whereas binary compounds stabilize with the proper weights and space distribution [57,58]. An example of the model solutions for these processes (see Section 2) is reported in Figure 7, where the density of the silicide (Ni x Si y ) compounds forming at the Ni-SiC interface is shown as a function of the time for a PLA process with a pulse of about 160 ns (λ = 308 nm) and 3.6 J/cm 2 energy density.…”

An in situ synchrotron X-ray study of reverse austenitic transformation in a metastable FeMnCo alloy

“…The reverse austenitic transformation may be conceived as a processing solution in addition to compositional design. In principle, rapid heat treatment or up-quenching either through laser annealing [19,65] or high-frequency induction heating can be applied to the deformed specimen, realizing the HCP-martensite reverse transformation within a time scale of 10 1 ~ 10 2 s. As suggested by both the hardness and the strain hardenability assessments in Fig. 8(a and b), the resulting microstructures are anticipated to offer sufficient mechanical strength while maintaining plastic deformability.…”