Interfacial reactions in GaSb/Co metallization contacts during thermal processing

The utility of thermodynamic potential (activity) diagrams in predicting the reaction zone morphology developed in the GaSb/Co metallization contacts during thermal processing is demonstrated. A number of experiments were designed to test the model. These are aimed at determining phase equilibria in the Ga-Sb-Co system and studying the microstructural evolution of the reaction zone in bulk as well as thin-film diffusion couples. Interfacial reactions between cobalt and single-crystal (001) GaSb have been investigated at 500 C. No ternary phases exist in the system at this temperature. The cubic CoGa and CoSb3 phases were observed to be dominant growing compounds in the semi-infinite bulk as well as in thin-film reaction couples, the latter intermetallic being formed next to the GaSb substrate. When the Co film is consumed by the reaction, the final configuration of the metallization layer GaSb/CoSb3/CoGa was found. This information is important in designing uniform, stable contacts for the metallization of gallium antimonide