Thin film compound phase formation sequence: An effective heat of formation model

Abstract

An effective heat of formation (EHF) model for predicting compound phase formation sequence is described. The EHF model defines an effective heat of formation ΔH′, which is concentration-dependent. By choosing the effective concentration of the interacting species at the growth interface to be that of the liquidus minimum, the model correctly predicts first phase formation during formation of silicides, germanides, aluminides and other metal-metal binary systems. The ability to predict phase formation sequence and phase decomposition is illustrated for some silicide and aluminide systems. The EHF model is also used to describe phase formation in lateral and bulk diffusion couples and for the interpretation of the effects of impurities and diffusion barriers on phase formation. It is also shown how the EHF model can be applied to laser and ion-beam induced phase formation and to the formation of amorphous and metastable phases. A compilation of recommended heats of formation for many silicide, germanide, aluminide and other metal-metal binary systems is given. In cases where experimental heats of formation were not available or if they were suspected of being unreliable, use was made of calculated values according to Miedema's model.