Laser surface cleaning - basic understanding, engineering efforts and technical barriers

Abstract

Laser cleaning as a new cleaning technique has emerged in order to effectively remove contaminants from solid surfaces. Two types of laser cleaning techniques have been developed recently, relying on pulsed laser heating of the surface without or with the presence of a thin liquid coating. Laser cleaning was demonstrated both theoretically and experimentally to be an effective cleaning technique for removing contaminants from solid surfaces without damage. For dry laser cleaning, two cleaning models were established for removal of particles from substrate surfaces from the viewpoint of energy and force. For steam laser cleaning, a cleaning model was established for removal of particles from substrate surfaces with a thin liquid layer by taking Van der Waals force, capillary force, cleaning force, and chemical bonding into account. The models not only explain the influence of incident direction, wavelength, fluence on cleaning efficiency, but also predict the cleaning thresholds. The experimental results show that the laser cleaning efficiency increases with increasing fluence and pulse number, but does not depend on the repetition rate. The surface cleanliness can be monitored in real time by acoustic, electric and optical means. Applications of laser cleaning to clean magnetic slider surface, magnetic media surface, silicon wafer and IC mold surface will also be addressed. Engineering efforts and technical barriers of laser cleaning will be discussed in detail.