Femtosecond laser ablation of thin films for the fabrication of binary photomasks

Abstract

Femtosecond lasers have considerable advantages over conventional laser sources for microfabrication. Even features with sizes very much less than the focused beam spot size of the laser can be fabricated using these lasers. Considering the potential of the laser for microfabrication, a valuable technique has been developed for the fabrication of binary photomasks by using femtosecond laser ablation of thin films. This is a single-step process and is faster compared to the complex multi-step lithography process currently used for photomask fabrication. A dispersion compensated acousto-optic scanning system has been developed for scanning the beam to transfer the required pattern to the mask blank. The applicability of this technique for microfabrication has been proven conclusively by fabricating microfeatures with the photomask fabricated by this technique. This can be made industrially viable by incorporating femtosecond laser sources with high pulse repetition rates.