Dual Wavelength Laser Thermal Processing of Semiconductors

摘要

The annealing of ion-implantation damage in semiconductors by laser irradiation is optimized by employing a dual wavelength laser source and tailoring the time delay between pulses at the two wavelengths. This takes advantage of the strong temperature dependence of the absorption coefficient for the initially less-strongly absorbed wavelength. A solid-state laser emitting high-intensity pulses at 0.53 millimicrons and 2.06 millimicrons was used in conjunction with an optical fiber delay line to experimentally study the annealing characteristics of an arsenic-implanted silicon solar cell wafer. By varying the length of fiber and varying the delay between pulses of the two wavelengths, it was determined that at 25 nanoseconds delay, the sample surface is preheated by the 0.53 millimicron radiation. These results are in agreement with a theoretical model based on melting and liquid phase epitaxial regrowth. Calculations based on this model are presented.