抄録
Micromachining of silicon was investigated using the fourth-harmonic wavelength (λ=266 nm,τ=6ns) of a pulsed Nd: YAG laser beam. The beam was irradiated onto a silicon workpiece under flowing water. The drilled surfaces were then characterized using an optical microscope, laser interference microscope and a scanning electron microscope. Compared with atmospheric machining, problems, such as debris and reattachment of molten material, were improved clearly and dramatically. Machining under water produced a somewhat smoother ablated surface because the molten silicon was rapidly solidified. When the focal point was set over the surface, the ablated shapes after laser irradiation were irregular because water evaporation caused unstable ablation. On the other hand, stable ablation was produced when the focal point was set under the surface. The relationship between the irradiation parameters and the resulting shape became quantitatively clear from the experiment.
