Structural characterization of α-Si films crystallized by combined furnace and laser annealing

Amorphous Si films grown by low-pressure chemical vapor deposition (LPCVD) were subjected to a two-stage annealing process involving a low-temperature furnace annealing at 600 degrees C for 6h followed by laser annealing under various beam energy densities. The structure of the poly-silicon films was studied by means of transmission electron microscopy (TEM) and atomic force microscopy (AFM). Large, heavily defected grains are formed during the furnace annealing step, the in-grain defects being mainly microtwins. These defects are eliminated by a combined liquid-solid slate process taking place at sufficiently high laser energy densities, whereas the mean grain size remains constant. This process occurs up to the critical energy density corresponding to the near-complete melting of the films. The furnace annealing controls the size of the grains and the subsequent laser annealing the in-grain defect density. The two-step annealing process is far more tolerant compared with the super lateral growth (SLG) method and fully applicable in large area electronics.