Repetition rate effect on the laser ablation of polymer structures

Abstract

Multilayer polyimide structures may be used as an etch stop mechanism in laser ablation processing. By changing the optical properties of the polymer it is possible to better control the depth of the patterns produced by the lasers. We present the effect of the repetition rate in the ablation of multilayer structures. The results are obtained from a photothermal model that includes the light absorption by the decomposed fragments, which shield the polymer from the incoming laser beam. The model also includes an intermediate zone in which the polymer suffers a phase transition. The evolution of the temperature profiles is simulated during each pulse taking into account the pulse shape; however, a simple diffusion model is used between pulses. The results of the simulations indicate the range of values for which the multilayer structure may be used as an effective etch stop mechanism. We found that the effectiveness of the multilayer structure deteriorates for increasing repetition rates. © 1995 American Institute of Physics.