Abstract :
Polycrystalline silicon-germanium (poly-SiGe) films can be an attractive alternative to poly-Si in several technologies like TFTs where thermal budget allowances may be limited. In this work, we investigate the formation of poly-Si1−xGex films by using a XeCl pulsed excimer laser to induce either alloying (PLIA) or crystallization (PLIC) processes. In the first case, the starting material consisted of an amorphous Ge layer electron-evaporated onto poly-Si grown on quartz substrates. Both the Ge mole fraction and the alloyed junction depth can be controlled by varying the laser energy fluence and/or the number of laser pulses. As an example, poly-Si1−xGex layers with x = 0.3 can be easily obtained by this technique. In the second case, thin amorphous Si/Ge layers, prepared by successive evaporations of the two elements onto oxidized Si substrates, were submitted to the XeCl laser irradiation and the resulting films were investigated using the TEM and Raman spectroscopy techniques. They showed that the processed layers (120 nm thick) are polycrystalline with grains as large as 200 nm and an almost equal Si and Ge content.
