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

Based on experimental results, an analytical model of multipulse excimer laser drilling in polymers is developed in this paper. It is shown that the adequate account of the mechanism of radiation propagation and absorption inside the keyhole is important for the good agreement of theory and experiment. The controlling factors of drilling are revealed. Keyhole pro®le and depth versus incident ¯uence are calculated for top-hat beam. The matching conditions for laser ¯uence, parameters of optical scheme and material parameters are derived in an explicit analytical form, allowing to produce deep narrow keyholes with practically parallel side walls and aspect ratios as high as 300±600. # 2000 Published by Elsevier Science B.V.