Transmission electron microscopy study of the platinum germanide formation process in the Ge/Pt/Ge/SiO2/Si structure

The mechanisms of the platinum germanide formation by RTA processes in the Ge/Pt/Ge/SiO2/Si structure in the temperature range from 200 deg C to 600 deg C were investigated by means of transmission electron microscopy (TEM) techniques. The studies were focused on the observations of the layer microstructure and of Ge/Pt/Ge interfaces at an atomic scale by high resolution TEM (HRTEM), as well as on the identification of formed phases using analytical TEM and diffraction techniques. The formation of platinum germanides in the Ge/Pt/Ge/SiO2/Si structure is visible at 200 deg C. However, at this temperature only a part of Ge reacted with the whole Pt during annealing. The whole Ge layer reacted with the Pt layer at 300 deg C. The formed Pt-Ge layer is not a mono-layer but consists of two platinum germanides layers. The results of the annealing of Ge/Pt/Ge/SiO2/Si structure at higher temperatures are very similar to the results obtained at 300 deg C. Various Pt-Ge phases have been found in the samples studied. The PtGe phase in the germanide layer of the sample annealed at 200 deg C was found by means of TEM diffraction analysis and the energy-dispersive X-ray spectroscopy (EDXS) in scanning TEM. At 300 deg C the diffraction pattern reveals the reflections corresponding to PtGe and Pt2Ge3 phases. Analytical TEM studies showed that the phase composition depends on annealing temperature and that the Ge content in the Pt-Ge phases increases with temperature.