Melting of Crystalline and Amorphous Silicon by Ruby, XeCl and KrF Laser Irradiation

摘要

Pulses of radiation from a ruby laser (lambda = 693 nm, FWHM = 12 ns), a XeCl excimer laser (lambda = 308 nm, FWHM = 25 and 70 ns), and a KrF excimer laser (lambda = 248 nm, FWHM = 32 ns) have been used to induce melting of crystalline silicon and thin (<1 mu m) amorphous layers of Si on crystalline silicon substrates. Depths of melting in crystalline Si were measured by TEM observations of the removal of dislocation loops created by low-dose ion implantation. Depths of melting of amorphous Si layers were monitored by observing the boundaries between a large polycrystalline region, assumed to form by normal melting from and resolidification back to the free surface, and a fine polycrystalline region, assumed to form by the explosive propagation inward of a thin buried liquid layer. In this work we report the comparison of predictions of heat flow calculations to the measured depth of melting in both crystalline and amorphous silicon. Excellent agreement is found with the Ruby and the XeCl results. Reasonable agreement with the KrF results is obtained only if the silicon liquid phase reflectivity at 249 nm is significantly less than that obtained by extrapolation of the optical parameters from longer wavelengths. (ERA citation 10:039569)