ACOUSTIC-EMISSION IN LASER-SURFACE CLEANING FOR REAL-TIME MONITORING

Real-time monitoring of surface cleanness in laser dry cleaning has be en achieved by monitoring the acoustic waves emitted from the substrat e surface under pulsed laser irradiation. It is found that the acousti c wave emitted from the surface under laser irradiation can reflect th e surface condition, i.e., the surface cleanness. Removal of surface c ontaminants can result in a weakened laser-induced acoustic wave. The surface cleanness, therefore, can be monitored in real time by detecti ng the amplitude and frequency of the acoustic wave during the laser c leaning process. This phenomenon provides the laser cleaning system wi th real-time feedback during the cleaning process.