Excimer laser ablation of microstructures: A numerical model

Abstract

A new model for the ablation of microstructures with excimer laser radiation is presented. The model is based on an interactive two-step approach. The local distribution of the light over the developing structure is evaluated for each pulse. This distribution is then used to calculate the local etch rate, and hence the change to the structure. Despite the assumptions inherent in the model, in particular assumptions made about the propagation of the light through a developing structure and about the etching behavior of the materials, results from the model agree with actual aspects of ablated structures. The model has been used with some success to predict the wall angles of trench structures ablated using partially coherent illumination from a fly's eye homogenizer. Predictions of the model show good agreement with the experiment results. In particular, the model correctly predicts the variation of the wall angles with incident fluence and also predicts structures with well defined wall angles over depths much greater than the depth of focus of the image.

Micromachining of polyurethane (PU) polymer using a KrF excimer laser (248nm)

“…Excimer laser ablation and direct etching of material by pulsed UV light has been an interesting subject of research activity since the early 1980s (Paterson 1999). Among many types of lasers developed during the development era, excimer laser was proved its way as a powerful and reliable piece of equipment for various application areas ranging from biomedical devices to semiconductors.…”

CAD/CAM software for an industrial laser manufacturing tool

“…Some account has to be taken of the angle of incidence, and in the absence of measured data we simply take the component of fluence in the direction of the local normal to the surface. This assumption has been used previously when modelling excimer laser ablation of microstructures, and has been shown to give reasonable agreement with experiment, at least for some common polymer materials [3,4]. A third option for estimating material removal, which we have not yet implemented, would be to store measured single pulse ablation crater profiles, covering a range of spot sizes and pulse energies.…”

A study of angular dependence in the ablation rate of polymers by nanosecond pulses

“…Ignoring the workpiece greatly simplifies the calculation, while at the same time limiting the range of situations to which the simulator can be applied. Details of the calculation, which takes full account of the illumination optics, can be found in earlier publications [9,11].…”

“…Both the cost of mask manufacture and the delay caused by iterative corrections to the mask design can be a problem for many potential users of laser ablation. We have previously reported on the development of simulation tools to aid in the design of laser tool paths and photomasks [9][10][11]. These tools can reduce the need for iterative corrections and reduce the overall cost of producing a prototype structure.…”