Low temperature poly-germanium growth process on insulating substrate using palladium-induced lateral crystallization

A thin palladium layer (~20 A) was selectively formed on top of amorphous germanium film before annealing and the effects of palladium layer on the lateral crystallization behavior of the amorphous germanium film were investigated through optical microscope, Raman spectroscopy, transmission electron microscopy, energy dispersion X-ray spectroscopy and selective area electron diffraction. Lateral crystallization of Ge with high growth rate was observed after annealing at 400°C in N₂ ambient. High quality poly-crystallized Ge film was formed with little metal impurity. This lateral crystallization phenomenon might be useful for fabrication of 3D ICs as the channel materials for thin film transistors, as well as for integration of Ge photodetectors on top of Si ICs.