Dual Wavelength Laser Thermal Processing of Semiconductors

摘要

By employing a dual wavelength laser source and tailoring the time delay between pulses at the two wavelengths to take advantage of the strong temperature dependence of the absorption coefficient for the initially less-strongly absorbed wavelength, the annealing of ion-implantation damage in semiconductors by laser irradiation may be optimized. A solid-state laser emitting high-intensity pulses at 0.53 micrometers and 1.06 micrometers was used in this study in conjunction with an optical fiber delay line to examine the annealing characteristics of an As-implanted silicon solar cell wafer. By varying the length of fiber and thereby varying the delay between pulses of the two wavelengths, it was determined that at 25 nsec delay, the sample surface is preheated by the 0.53 micrometers radiation to provide optimal coupling for the following 1.06 micrometers radiation. These results are in agreement with a theoretical model based on melting and liquid phase epitaxial regrowth. Caculations based on this model are presented.