Practical applications of laser cleaning for removal of surface contaminants

Abstract

As microelectronic fabrication technology advances, there has been an ever-increasing need to develop more effective techniques to remove submicron-sized contaminants.1 A submicron particle adheres strongly onto a surface, with a force as large as millions of times its weight. Recently, it has been demonstrated that explosive vaporization and ablation of a thin liquid film on a solid surface induced by short-pulsed laser irradiation can be efficiently used to remove submicron-sized particulates from the surface.2 It has been also demonstrated that lasers can provide an environmentally sound, cost-effective method of removing organic coatings from a variety of substrates.3 Two kinds of laser-assisted cleaning technique have been developed, i.e., "steam laser cleaning" and "dry laser cleaning."2 The first kind utilizes flash heating and subsequent rapid vaporization of a micron-thick liquid film which is deliberately deposited on the surface. It has been shown that a strong acoustic wave is generated by the explosion which is responsible for the removal of particles.4 The second utilizes ablative photodecomposition of organic substances which are adsorbed on the surface. Hence, cleaning can best be done with the combination of these two laser cleaning modes.