Effect of scanning resolution and fluence fluctuation on femtosecond laser ablation of thin films

Abstract

Femtosecond-pulse laser pulses have been shown to hold great potential for high-precision micromachining. Much research has been done to characterize the laser parameters for predicting the feature size, and the most important of these is the number of pulses incident at each point of ablation. Theoretical modeling, so far, has been restricted to a single point where the number of pulses incident at each point of ablation depends on the pulse-repetition rate and the dwell time of the laser beam at that machining point. However, to make the theoretical model useful, a laser scanning system with the ability to fabricate complex microfeatures is considered in this work. In this case, the scanning resolution determines the number of pulses incident at each scanning point. This has been taken into account while presenting a theoretical and experimental analysis of the effect of the scanning resolution on the threshold fluence of the material. Results of ablation on a gold thin film were subjected to theoretical analysis to predict the feature size. In addition, the effect of the energy fluctuation of the laser on the feature size has been evaluated to predict the minimum achievable feature size for a gold thin film.