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

TL;DR

This study explores the complex interactions, phase formations, and atomic diffusion processes in Ni/4H-SiC contacts under UV laser irradiation, combining experimental microscopy with phase field simulations.

Contribution

It provides a detailed multimethod analysis of the inter-diffusion, melting, and reaction mechanisms in Ni/4H-SiC under laser annealing, linking process parameters to material transformations.

Findings

Increased laser fluence expands silicide layer thickness.

Higher fluence promotes Ni2Si phase formation.

Silicon diffusion into nickel layer increases with fluence.

Abstract

We investigated the complex interaction between a nickel layer and a 4H-SiC substrate under UV-laser 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/cm2. To make a bridge between process conditions and post-process characterizations, time dependent ultra-fast phenomena (laser pulse about 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 Ni2Si phase is promoted at the highest fluence 3.8 J/cm2; 4) silicon atomic diffusion into a topmost residual nickel layer occurs, with the Ni/Si ratio increasing towards the contact surface.