Use of enclosed thin laminar liquid flows above ablation area for control of ejected material during excimer machining

To observe excimer laser machining through enclosed thin liquid films and the effects thereof on debris control, new equipment was designed to contain a small control volume that can be supplied with an enclosed laminar 0.5 mm film of DI water to flow over the workpiece at a controlled flow rate. Using the same equipment, comparison with open laminar thin film DI water immersed ablation and non-liquid immersed ablation was possible. Reliable calculations of the debris size and density with respect to the distance from the centre of the shot, as well as the identification of modal trends in the dispersion of the debris were obtained from analysis of microscope images with graphical analysis software. The results suggest that debris ejection direction is dependent upon the beam incident angle with the workpiece and that dispersion distance is related to particle size, beam intensity and the material being machined. The results show enclosed, rapid flow liquid immersed ablation provides both better machined feature geometry and higher efficiency of debris removal than the other techniques investigated.