Laser-Crystallisation of Amorphous Si Layers and Two-Dimensional Simulations of the Process Dynamics

摘要

We investigate the influence of various processing parameters such as laser fluence and thickness of the prior amorphous silicon layer on the structural properties (grain size, defect structure) of laser crystallized films. Experimentally, we use optical microscopy and transmission electron microscopy and theoretically, we apply two-dimensional simulations of the melting and solidification process. The combination of experimental data base and simulation is powerful in defining the optimum processing parameters that maximise the volume fraction of large-grained polycrystallinc material. We base our two-dimensional simulations on the method of finite differences and calculate for each timestep the complete temperature and phase state fields. These data yield the melt front velocity and the cooling rate, which both determine the maximum achievable grain size of the process and control the defect population. Comparison between our simulations and experiments shows that our two-dimensional model describes the real crystallisation process rather well.