Dissociation of dilute immiscible copper alloy thin films

The dissociation behavior of dilute, immiscible Cu-alloy thin films is foun d to fall into three broad categories that correlate most closely with the form of the Cu-rich end of the binary alloy phase diagrams. Available therm odynamic and tracer diffusion data shed further light on alloy behavior. Ei ght alloying elements were selected for these studies, with five elements f rom groups 5 and 6, two from group 8, and one from group 11 of the periodic table. They are respectively V, Nb, Ta, Cr, Mo, Fe, Ru, and Ag. The progre ss of precipitation in approximately 500-nm-thick alloy films, containing 2 .5-3.8 at. % solute, was followed with in situ resistance and stress measur ements as well as with in situ synchrotron x-ray diffraction. In addition, texture analysis and transmission electron microscopy were used to investig ate the evolution of microstructure and texture of Cu(Ta) and Cu(Ag). For a ll eight alloys, dissociation occurred upon heating, with the rejection of solute and evolution of microstructure often occurring in multiple steps th at range over several hundred degrees between approximately 100 and 900 deg rees C. However, in most cases, substantial reductions in resistivity of th e films took place below 400 degrees C, at temperatures of interest to copp er metallization schemes for silicon chip technology. (C) 2000 American Ins titute of Physics. [S0021-8979(00)07605-2].