Novel laser ablation patterning with organic film in running water

In the tri-level resist process, it is sometimes difficult to detect the alignment mark because of the anti-reflection performance of the organic thick anti-reflective (ARL). Laser ablation in running water was one of the most effective techniques for removing the organic thick ARL on the alignment mark. Generally, the ablation process produces many particles. The results of our experiment indicate that the particle distribution area greatly depends on the dome-shape bubble on the ablation area. The particle distribution area could be minimized by optimizing some ablation conditions according to the estimated size of the dome-shape bubble. By optimizing a shift of the narrow slit-laser-beam and its energy so as to keep the ablation/initial thickness ratio to less than 20%, fine ablation area could be obtained. This novel ablation technique is very useful for particle-free selective removal of the organic thick ARL film.