Multiphysical Simulation of ns-Laser Ablation of Multi-material LED-structures

Structuring of multilayer stacks with ns-laser pulses is widely used in the industrial production of LEDs. These stacks are built up from several different materials each one layered upon each other. In order to thoroughly understand the physics of the structuring process a multiphysical simulation model has been developed. This model is capable to handle the beam propagation and the energy coupling into the work piece both for transparent and for absorbing materials as well as phase transitions (melting, solidifying, evaporation, condensation) of multiple different materials within the calculation domain. Furthermore a modified volume of fluid approach has been developed to calculate the material and energy flow within both the liquid and vapor phases and thus to track the free surface of the material during laser ablation. The paper gives an insight into this model illuminating the physical background of the ablation process and shows the excellent correspondence of the simulations with experimentally obtained results.