Invited Lecture
Texture evolution during solid-state reactions - silicides and germanides

Silicides and germanides compounds are formed out of a metal and silicon or germanium. In the microelectronics industry, silicides are the preferred material for electrically contacting silicon-based source and drain regions, while germanides are considered as a top candidate for contacting future germanium-based electronics. These compounds are fabricated through thermal processing of a metal layer on top of the silicon or germanium substrate. The thermodynamic and morphological stability of the formed structure is of utmost importance for the micro-electronics industry in order to create a reliable device. The atomic mobility allows the thin-film structures to optimize their geometry upon annealing in order to lower the total energy. As such, thin uniform silicide films evolve into agglomerated islands upon thermal annealing, which destroys their conductive properties.

In this presentation, we elaborate on the discovery of a peculiar correlation between this morphological degradation and the preferential crystallographic orientation of the individual silicide grains. The recently-discovered axiotaxial alignment, which can exist in addition to other textures such as epitaxy and fiber-alignment, plays a crucial role in the agglomeration process. Based on energetic considerations, we explain that the mass transport is expected to occur from randomly- or epitaxially- oriented grains towards axiotaxial grains with a curved interface.

De Keyser et al. Appl. of Texture Analysis: Ceramic Transactions 201 (2008): 3
De Schutter, et al. Applied Physics Reviews 3.3 (2016): 031302.

Figure: Illustration of agglomeration occurring in thin NiSi films on Si(001) during annealing.