Fabrication of Columnar Sub-microstructures using a Q-switched Nd:YAG Laser in the Nanosecond Time Regime

摘要

We report here on the formation of columnar sub-microstructures in single-side polished silicon wafers by optimizing ablation laser parameters. Laser ablation was performed in air and the parameters, fluence and the number of pulses of the third harmonic of a Q-switched Nd:YAG laser operated at fixed repetition rate of 10 Hz were investigated. Columnar sub-microstructures were predominantly observed along the border of the ablation centers in the silicon substrates that were placed 9.3 cm in front of a 10 cm focal length quartz lens. Silicon substrates were exposed to flu-ence of 1.0 and 1.5 J/cm2 and 50-2000 laser pulses. Columnar sub-microstructures at the ablation centers were observed only for 50 and 100 pulses at 1.0 J/cm2. The average period of these struc-tures, with the parameters optimized, was close to the wavelength, reaching heights in the hundreds of nanometers to slightly greater than 1 μm above the surface. Columnar formation was non-existent at lower fluence of 0.15 and 0.3 J/cm2, which were characterized by laser-induced periodic surface structures.