We have investigated the interfacial reactions of Ni films on Si1-xGex (x = 0.0-0.2) epitaxial (001) layers as a function of the annealing temperature between 300 and 800°C. It is shown that the Ni-silicided Si1-xGex layers have a higher sheet resistance and poorer surface and interface morphologies, compared to the Ni-silicided Si layer. As the annealing temperature is increased, the silicide layers become irregular with thermal grooving and, consequently, become agglomerated. This is more severe in the sample with a higher Ge content. Glancing angle x-ray diffraction results show that, unlike the Ni-silicided Si sample, for the Si1-xGex (x = 0.1 and 0.2) samples, no phase transition from Ni germanosilicide (Ni(Si1-mGem)) to Ni(Si1-nGen)2 occurs throughout the annealing temperature domain. Transmission electron microscopy and energy dispersive spectroscopy results show that Ge atoms outdiffuse from the Ni germanosilicide as the annealing temperature increases. The outdiffused Ge atoms are segregated at the Ni germanosilicide/Si1-xGex interfaces and at the surface regions between the agglomerated germanosilicide. A simple model is given to describe the Ge segregation and silicide islanding behaviours.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering
- Materials Chemistry