STRUCTURAL CHARACTERIZATION OF ALPHA-SI FILMS CRYSTALLIZED BY COMBINED FURNACE AND LASER ANNEALING

Amorphous Si films grown by low-pressure chemical vapor deposition (LP CVD) were subjected to a two-stage annealing process involving a low-t emperature furnace annealing at 600 degrees C for 6h followed by laser annealing under various beam energy densities. The structure of the p oly-silicon films was studied by means of transmission electron micros copy (TEM) and atomic force microscopy (AFM). Large, heavily defected grains are formed during the furnace annealing step, the in-grain defe cts being mainly microtwins. These defects are eliminated by a combine d liquid-solid slate process taking place at sufficiently high laser e nergy densities, whereas the mean grain size remains constant. This pr ocess occurs up to the critical energy density corresponding to the ne ar-complete melting of the films. The furnace annealing controls the s ize of the grains and the subsequent laser annealing the in-grain defe ct density. The two-step annealing process is far more tolerant compar ed with the super lateral growth (SLG) method and fully applicable in large area electronics.