Excimer laser ablation for micro-machining: geometric effects

KrF laser ablation of an epoxy material has been used to study the effects of surface geometry for micro-machining applications. Morphological features with surface height variations greater than the ablation depth per pulse and transverse dimensions on the scale of the irradiating spot are shown, during multi-pulse ablation, to evolve into surface profiles which may be predicted by considering the local variation in effective fluence. This simple model is seen to be in good agreement with ablation experiments carried out on convex and concave surfaces. Stepped features are more problematical and factors such as diffraction and local pressure inhibition of ablation must also be considered.