Excimer laser crystallization processes of amorphous silicon thin films by using molecular-dynamics simulations

Crystallization processes of amorphous Si during the excimer laser annealing in the complete-melting and near-complete-melting conditions have been investigated by using molecular-dynamics simulations. The initial amorphous Si MD cell was prepared by quenching a liquid Si layer with 18 666 atoms. KrF excimer laser annealing processes of amorphous Si were calculated by taking account of the change in the optical constant upon melting during a Gaussian-shape laser pulse shot with full width at half maximum (FWHM) of 25 ns. The simulated results well reproduced the observed melting rate and the near-complete-melting and complete-melting conditions were obtained for 160 and 180 mJ/cm² fluence, respectively. It was found that larger grains were obtained in the near-complete-melting condition. Our MD simulations also suggest that the nucleation occur from unmelted amorphous Si region during laser irradiation and crystal growth proceeds toward supercooled /-Si region in the near-complete-melting condition.