Abstract
Influence of stress on the formation of iron disilicide films on (001)Si substrates has been investigated by X-ray diffraction, auger electron spectroscopy, transmission electron microscope, and sheet resistance measurements. From the glancing-angle X-ray and AES analysis, FeSi was found to be the dominant phase at 500 oC. Above 600 oC, b-FeSi2 was found to be the dominant phase. Sheet resistance measurements showed that the Rs is of higher value at 600 oC for the compressively stressed sample indicating that the transformation to the high resistivity phase ( orthorhombic b-FeSi2 ) is faster in these samples. Planview TEM micrographs showed that the microstructure (grain size) and defect (stacking fault) density is affected by the presence of stress. Analysis of the electron diffraction pattern revealed the appearance of the b-FeSi2 phase above 500 oC. No epitaxial silicide formation was observed on (001)Si at higher temperatures. From the XTEM micrographs, the samples annealed at 500 oC showed a dual-layered structure, a needle shaped top layer and the bottom layer with polygonal grains. Using EDS, it was identified that the top layer was g-FeSi2 and the bottom layer was FeSi. When the annealing temperature was higher than 500 oC, the film structure transformed to b-FeSi2. As the volume of b-FeSi2 phase is larger than FeSi, at high tempratures, the films on the compressively stressed wafers are subjected to tensile stress to accommodate the change in volume and this enhances the formation of b-FeSi2.