The effect of germane variation on microstructure in polycrystalline Si/Si_1-xGe_x thin films grown by rapid thermal chemical vapour deposition: Fractal characterisation using scanning probemicroscopy

Scanning probe microscopy (SPM) techniques have been employed to image and characterise polycrystalline thin films of both pure silicon and Si/Si _1-xGe_x. The layers were grown on oxidised silicon substrates using a rapid thermal chemical vapour deposition (RTCVD) reactor. Microstructural characteristics (roughness and grain size) were measured and their dependence on germane content to the gas flow during deposition elucidated using a range of analysis techniques, including fractal methods. By tracking the evolution of cross-over points in the fractal spectrum, an estimate for the grain size range can be obtained, which tallies extremely well with actual topographical measurements.