Study on solid-phase reactions in Ti/p+-Si1−x−yGexCy/Si(100) contacts

We have investigated the solid phase reactions between Ti and p+-Si1−x−yGexCy (x=0–0.470, y=0–0.020) alloys in Ti/p+-Si1−x−yGexCy/Si(100) systems using two-step annealing. For Si-rich samples, a C49-Ti(SiGe)2 phase is formed after the first annealing at 550 °C. After the second annealing, the C49-Ti(SiGe)2 phase is transformed into a C54-Ti(SiGe)2 phase, which has low sheet resistance. For Ge-rich samples, on the other hand, Ti6Ge5 is formed after the first annealing. At the same time, discontinuous Si-rich SiGeC regions are formed at the Ti6Ge5/p+-Si1−x−yGexCy interface. After the second annealing, the C49-Ti(SiGe)2 film appears in the form of agglomerated morphology. The agglomeration is considered to be due to preferential consumption of the discontinuous Si-rich SiGeC regions during the formation of the C49-Ti(SiGe)2 phase. As a result of the agglomeration of the C49-Ti(SiGe)2 film, the C54-Ti(SiGe)2 film also becomes discontinuous. Moreover, it is found that the C atoms in the p+-Si1−x−yGexCy layer have an effect of elevating the transformation temperature from C49-Ti(SiGe)2 to C54-Ti(SiGe)2. By contrast, the sheet resistance of the C54-Ti(SiGe)2 film is hardly influenced by Ge and C atoms.