Si (100) Formed On The Substrate Ni - Co Alloy Silicide And Its Features

As CMOS IC fabrication technology continuously progresses, the self-aligned silicide (SALICIDE)material and technology also require corresponding innovations.the industry has converged towards TiSi2, CoSi2, and NiSi one after another for the self-aligned process. To address their disadvantage, the silicide of Ni allied with other materials are well researched. Among them, Ni-Co silicide has been considered one of the most promising silicide for its extraordinary properties.Annealing behaviours of ultrathin Ni-Co deposited on Si (100) substrate are studied. Ultrathin silicide films were formed by starting from1-8nm thick Coi-xNix (with Co fraction of0%-100%) at350-900℃. These ultrathin silicide films have low sheet resistance, good thermal morphology and epitaxial alignment at silicide-Si interface. Raman spectroscopic analysis seems to indicate that "Ni could be dissolved in the CoSi lattice to a certain fraction despite the fact that CoSi and NiSi are distinct with different crystallographic structures. Moreover, the disorder-induced Raman scattering in NiSi2is found to be enhanced by Co incorporation. For each Co fraction, there exists a critical thickness above which the transition temperature from monosilicides CoSi and NiSi to a disilicide-like phase increases with increasing film thickness. Below this thickness, the disilicide phase seems to form without exhibiting the monosilicides within the detection resolution limits of transmission electron microscopy and Raman spectroscopy. This research built a thermodynamic modal according to the classic nucleation theory. The observed annealing behaviours are attributed to variations in free energy change for phase transition caused by differences in metal thickness.