Interaction of Cu and Cu3Ge thin films with Si1-xGex alloys

The interaction of Cu and Cu3Ge thin films with Si1-xGex (x=0.5) alloy laye rs epitaxially grown on Si(100) has been studied in the temperature range o f 250-400 degrees C. In this temperature range, Cu reacts with the alloy to form a Cu-3(Si1-xGex) ternary phase with an ordered body-centered-cubic cr ystal structure. The Cu-3(Si1-xGex) phase exhibits high-room-temperature (s imilar to 150 mu Omega cm) and nonmetallic resistivity. However, this terna ry phase is not observed and the diffusion of Cu into the alloy is suppress ed when Cu is replaced by low resistivity (typically less than 10 mu Omega cm at room temperature) epsilon(1)-Cu3Ge phase. In contrast to the results reported for films of epsilon(1)-Cu3Ge formed on Si(100), the outdiffusion of Si into the epsilon(1)-Cu3Ge films is found to be suppressed when the fi lms are formed on Si0.5Ge0.5 layers, indicating the increased stability of epsilon(1)-Cu3Ge on Si1-xGex alloys compared to pure silicon. (C) 1999 Amer ican Institute of Physics. [S0003-6951(99)01936-1].