Liquid-Assisted Excimer Laser Micromaching for Ablation Enhancement and Debris Reduction

Previous studies demonstrated that laser ablation under transparent liquid can result in ablation enhacement and particle removal from the surface. In this work, the liquid-assisted excimer laser ablation process is examined for polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), Si, and alumina with emphasis on ablation enhacement, surface topography, and debris formation. In the case of PET and PMMA, the effect of liquid is analyzed both for thin water film and bulk water. As the ablation enhanement by liquid is already known for Si and alumina, the analysis focuses on surface topography and debris formation resulting from the liquid-assisted laser ablation process. A KrF excimer laser is utilized for ablationg the materials in the fluence range 1~10 J/cm 2 . The results show that application of liquid increases the ablation rate of PMMA while that of PET remains unchanged even in the liquid-assisted process. It is also revealed that the liquid can significantly improve the surface quality by reducing the debris deposition. However, the surface roughness is generally deteriorated in the liquid-assisted process. The surface toporaphy is found to be strongly dependent on the method of liquid application, i.e., thin film or bulk liquid.