Structural analysis and crystallization studies of germanium-antimony-tellurium sputtered films on different underlayers

Crystallization processes and structures were analyzed, by using modified dynamical reflectance spectroscopy, x-ray diffraction measurement, and transmission electron microscopy for a germanium-antimony-tellurium (Ge-Sb-Te) ternary amorphous film on different underlayer materials: a silicon nitride (Si3N4) film and a zinc sulfide-20 mol % silicon dioxide (ZnS-SiO2) film. The crystallization temperature was almost the same (about 430 K) for each sample. Above the crystallization temperature, the Ge-Sb-Te film on the Si3N4 underlayer film exhibited a face-centered-cubic (fcc) structure and grains grew gradually with transformation to a hexagonal structure, whereas the film on the ZnS-SiO2 underlayer film exhibited mixed phases of the fee and hexagonal structure and abrupt grain growth at 520 K. These crystallization differences are thought to be caused by the interfacial atomic arrangement of amorphous Ge-Sb-Te. This arrangement depends on the chemical affinity at the interface. (C) 1998 American Institute of Physics.