Metastable phase formation during the reaction of Ni films with Si(001): The role of texture inheritance

The thermally induced solid-state reaction between a 10-nm-thick Ni film and a Si(001) substrate was investigated using in situ x-ray diffraction and ex situ pole figure analyses. The reaction begins with the appearance of orthorhombic Ni2Si grains characterized by a strong fiber texture. The formation of the metastable hexagonal θ phase—which inherits the fiber texture of Ni2Si—is then observed. This phase has been observed in every sample studied regardless of dopant, film thickness, deposition method, and anneal profile (>2000 conditions). Texture inheritance allows a reaction pathway with a lower activation energy than the expected formation through thermodynamically stable Ni silicide phases.