22 February 2008 Influence of beam incidence angle on laser cleaning of surface particles
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Proceedings Volume 6622, International Symposium on Photoelectronic Detection and Imaging 2007: Laser, Ultraviolet, and Terahertz Technology; 662204 (2008) https://doi.org/10.1117/12.790719
Event: International Symposium on Photoelectronic Detection and Imaging: Technology and Applications 2007, 2007, Beijing, China
Abstract
Laser cleaning technology has great advantages. The influence of beam incidence angle was studied in the case of the removal weakly absorbing particles on absorbing particles on absorbing Si wafers by 248 nm DUV light pulse. By decreasing the beam incidence angle from 80° to 10°, the removal efficiency of 0.15-0.30 µm Si3N4 particles was increased by 30-45%, while no improvement was observed with 0.3 μm SiO2 particles. Theoretical calculations show that decreasing the incidence angle from 80° to 10° results in a 30-fold increase of the horizontal component of the radiation pressure force, whereas the vertical component remains unchanged as the beam width must be decreased to keep a constant fluence at the workpiece. This force would help removing particles by making them roll. Based on theoretical calculations, it is proposed that the enhanced removal of particles at grazing incidence is caused by the horizontal component of the beam radiation pressure. The difference between Si3N4 and SiO2 particles is attributed to the influence of particle shape on van der Waals adhesion forces: the adhesion force of irregularly shaped Si3N4 particles would be comparable to the horizontal component of the radiation pressure force, whereas the adhesion force of spherical SiO2 particles would be higher.
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Su-xia Hou, Su-xia Hou, Ji-jun Luo, Ji-jun Luo, Qing-hua Zhang, Qing-hua Zhang, Jin Ma, Jin Ma, } "Influence of beam incidence angle on laser cleaning of surface particles", Proc. SPIE 6622, International Symposium on Photoelectronic Detection and Imaging 2007: Laser, Ultraviolet, and Terahertz Technology, 662204 (22 February 2008); doi: 10.1117/12.790719; https://doi.org/10.1117/12.790719
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