Co-precipitation of copper and nickel in crystalline silicon

Co-precipitation of copper and nickel in silicon bicrystals produced by wafer-bonding has been investigated. Transmission electron microscopy and energy-dispersive X-ray analysis show two types of precipitates: copper-rich silicide particles that contain a small partial mole fraction of 5% of nickel and nickel-rich particles containing a partial mole fraction between 15% and 25% of copper. Both types of precipitates are found inside large precipitate colonies typical for copper precipitation in silicon in the absence of nickel co-doping. Thermodynamically these precipitates can be assigned to the known binary metal silicide phases Cu3Si and NiSi2 and a solid solution of a second metal species therein.