Study of excimer laser ablation of photoresist polymer in presence of hydrogen gas environment for micro-fluidic applications

Abstract

Excimer laser micro-machining has been extensively explored to fabricate micro-patterns in the last few decades in the field of micro-fluidics, precision bearings, optics, micro-electronics etc in their previous work, it was observed by the authors that hydrogen gas has greater impact on the material removal rate and surface quality while ablating photo-resist polymer. In the present work, effect of hydrogen gas on the material removal rate has been mathematically modeled and simulated using finite element technique. In this simulation work, variation of surface temperature as well as ablation depth as a function of laser pulse energy have been analyzed. The simulation result showed an enhanced material removal rate in hydrogen environment due to laser assisted chemical reaction(LACR) involving nascent hydrogen and polymer. Further, a set of laser ablation experiments on polymer using 248 nm KrF Excimer laser has been conducted both with and without Hydrogen environment and under inert gas environment of argon, to validate the mathematical model. Results of the laser ablation experiments have shown the influence of hydrogen gas environment in enhancing both the material removal rate and the excellent edge definition, which is a novel outcome of the present research work and best suited process for the fabrication of micro-fluidic channels. The simulation results have been found in good agreement with the experimental data which supports technical soundness of the proposed model presented and discussed in the paper.