Effects of solid phase crystallization by rapid thermal annealing on the optical constants of sputtered amorphous silicon films

Rapid thermal annealing is applied to induce crystallization of sputtered amorphous silicon deposited on thermally grown oxide layers. The influence of annealing temperatures in the range of 600 °C-980 °C is systematically investigated. Using scanning-electron microscopy, ellipsometry and X-ray diffraction techniques, the structural and optical properties of the films are determined. An order-of-magnitude reduction of the extinction coefficient is achieved. We show that the optical constants can be tuned for different design requirements by controlling the process parameters. For example, we obtain a refractive index of ~ 3.66 and an extinction coefficient of ~ 0.0012 at the 1550-nm wavelength as suitable for a particular optical filter application where a high refractive index and low extinction coefficient is desired.