Characterization of microparticles and oxide layers generated by laser irradiation of diamond-machined silicon wafers

Nanosecond-pulsed laser irradiation is a potential method for removing machining-induced subsurface damage from silicon wafers. In this study, the material compositions and microstructures of microparticles and oxide layers generated during laser irradiation were investigated by atomic force microscopy, energy-dispersive x-ray spectroscopy, cross-sectional transmission electron microscopy, electron energy-loss spectroscopy and Auger electron spectroscopy. The oxide layer was found to be approximately 5 nm thick, which is significantly thicker than the native oxide layer of silicon at room temperature in air (∼1 nm). The microparticles have a low-density amorphous structure and are mainly composed of silicon oxide, while a few particles contain silicon. The particles are attached to the substrate, but are distinct from it. The results indicate that silicon boiled during the laser pulse and that the particles are recondensed and oxidized liquid silicon boiled away from the wafer surface. The microparticles can be completely removed from the wafer surface by hydrofluoric acid etching.