Modelling of high-aspect ratio microdrilling of polymers with UV laser ablation

Based on experimental results, an analytical model of multipulse excimer la ser drilling in polymers is developed in this paper. It is shown that the a dequate account of the mechanism of radiation propagation and absorption in side the keyhole is important for the good agreement of theory and experime nt. The controlling factors of drilling are revealed. Keyhole profile and d epth versus incident fluence are calculated for top-hat beam. The matching conditions for laser fluence, parameters of optical scheme and material par ameters are derived in an explicit analytical form, allowing to produce dee p narrow keyholes with practically parallel side walls and aspect ratios as high as 300-600. (C) 2000 Published by Elsevier Science B.V.