Optical properties of excimer laser annealed polycrystalline Si by spectroscopic ellipsometry

Using spectroscopic ellipsometry (SE), optical properties of poly-Si obtained by excimer laser annealing of amorphous silicon (α-Si) are evaluated. Both, amorphous silicon and SiO2 are deposited on Si substrate (α-Si/SiO2/Si) by low temperature chemical vapor deposition (LPCVD). SE measurement shows that the crystallization starts with laser annealing of energy 144–280 mJ/cm2 and above at which it remains amorphous. A linear regression analysis (LRA) and a Bruggeman effective-medium approximation (EMA) indicate that the laser annealed layer consists of 91.3% crystalline Si and 8.7% amorphous Si for samples irradiated in two steps, i.e., 344 and 276 mJ/cm2 of each pulse. The thickness of each layer determined by SE is in good agreement with that of cross-section transmission electron microscopy (TEM).