Surface cleaning of silicon wafer by laser sparking

The removal of small particles (∼1 μm diameter) on a silicon wafer surface has been carried out by laser sparking, i.e., an intense laser pulse is focused in air generating a gas breakdown. It has been found that the airborne plasma shock waves induced by laser sparking initiated above the surface can successfully remove the particles such as tungsten, copper, and gold from the silicon surface. This new cleaning technique provides superior characteristics as an efficient, fast, damage-free process compared with conventional laser cleaning employing direct interactions between laser pulse and particles. The basic idea behind this technique and how to apply it for cleaning of the surface are described in detail. The cleaning mechanism is also discussed by comparing the adhesion force of a particle on a surface with the pressure of the shock wave generated by laser sparking in air.