Practical excimer laser-assisted cleaning of solid surfaces

Pulsed-laser irradiation on a solid surface induces a highly efficient surface cleaning of submicron-sized particulates and undesirable organic overcoat films. The nanosecond-pulsed UV laser irradiation, shortly after the deposition of a thin liquid film on the surface, induces rapid vaporization of the liquid film and removal of particulates (`steam cleaning'). The laser beam also causes ablative photodecomposition of organic film contaminants on the surface (`dry cleaning'). A laser cleaning tool is constructed with an aim toward practical use based on an industrial grade KrF excimer laser. The tool includes a computer-controlled laser beam scanning system and a stable liquid film deposition unit, providing a cleaning rate of over 200 cm2/min. The cleaning strategy and the physical mechanisms of the laser cleaning techniques are also studied.