Reactive Phase Formation in Thin Film Metal/Metal and Metal/Silicon Diffusion Couples

There have been a number of efforts to develop a model that could be used to predict and to describe phase formation in the case of thin film diffusion couples. In this report, thermodynamic and kinetic frameworks as well as some of the proposed models for interface reactions have been critically reviewed. The following conclusions have been made: First, in the early stage, solid-state interface reaction is a kinetic process. Phase selection and phase formation sequence are controlled mainly by nucleation kinetics and/or growth kinetics. Second, in order to simulate interface reactions in thin film diffusion couples, kinetic description of the system is required and should be combined with the thermodynamic description. This in turn requires the assumption of local thermodynamic equilibrium in the system. However, whether or not local equilibrium can be assumed at the interface in a thin film system depends on the thickness of the films, nucleation and growth kinetics, and the diffusivity of elements in the product phases. Finally, based on the theoretical considerations it appears that there is no fundamental difference between thin film and bulk diffusion couples.