Kinetics of Ag/Al bilayer self-encapsulation

The self-encapsulation kinetics of Ag/Al bilayers were studied both experim entally and theoretically as part of the effort to introduce Ag as an alter native metallization scheme for future ultra-large-scale-integrated technol ogies. Theoretical modeling was based on an analytical solution of a modifi ed diffusion equation, which incorporated the diffusion of Al atoms through the Ag layers during the Ag/Al bilayer encapsulation progress. The amount of segregated Al atoms was monitored by both Rutherford backscattering spec trometry and film resistivity measurements, and correlated well with the th eoretical predictions. These findings showed that the kinetics of the self- encapsulation could be significantly affected by both (i) the chemical affi nity between Al and Ag atoms, and (ii) the interfacial energy between the m etal layer (Ag) and the newly formed AlxOyNz diffusion barriers. Higher ann eal temperatures were shown to accelerate the encapsulation process, and he nce, achieved a lower resistivity in the underneath Ag layer. This model, i n addition, confirmed the self-passivating characteristics of AlxOyNz diffu sion barriers formed by Ag/Al bilayers annealed between 500 and 725 degrees C. (C) 1999 American Institute of Physics. [S0021-8979(99)07622-7].