Growth kinetics of individual Al-Cu intermetallic compounds

The growth kinetics of Al-Cu intermetallic compounds (IMC) have been investigated on thin film couples and bonded samples in the range 150°C to 250°C using XRD, SEM/EDX and in-situ interface resistance monitoring. Individual diffusion constants D_o and activation energies E_a (1.01eV, 0.97eV, 1.23eV, 1.28eV) have been obtained from thin film couples for the main three IMC phases Al₄Cu₉, AlCu and Al₂Cu, and for the total IMC growth, respectively. Two additional phases (Al₃Cu₂, Al_0.06Cu_0.94) contribute to the total IMC growth at T ≥ 200°C, but do not form at lower temperatures. Lower activation energies of 1.13eV (thin film) and 1.05eV (bonded samples) have thus been derived for T <; 200°C for the overall IMC growth and are recommended to be used for lifetime predictions in the typical regime of device application temperatures.