Thermal Simulation of UV Laser Ablation of Polyimide

Our aim is to provide a simulation tool for manufacturing processes that takes the influence of temperature distribution thus the underlying copper pattern and pulse repetition frequency into account. To establish such simulation software a finite element model was set up which is able to describe the thermal processes and ablation induced by laser irradiation of polymers. The etch rate description usually applied for excimer lasers was slightly altered to be adequate for Gaussian lasers by writing pulse energy instead of fluence. This theoretical consideration was proved by experiments. The experiments also revealed the temperature dependence of etch rate and the influence of pulse repetition frequency on the amount of ablated material. The experimental and simulation results are in good agreement.