Pulse duration dependent laser-induced plasma etching of polyimide using a high repetition rate laser

Although laser ablation of polymers is well investigated the achievable surface quality of this process is limited due to laser-induced structural and morphological defects, arising surface roughness and redeposition of debris. Because high quality machining with laser radiation is highly requested, laser-induced plasma etching (LIPE) of polyimide film is studied for the development of ultraprecise surface machining (UPSM) techniques for various applications. Thus, the key parameters such as laser power, etching time, plasma distance of the LIPE are studied experimentally to explore the impact to the etching rate and the surface morphology. LIPE rates as low as 1 pm per laser pulse were measured that fulfil UPSM requirements. The footprint of the LIPE is circular shaped and enable therefore the development of areal processing strategies for surface correction, aspherization and freeform processing. In addition, regular nanostructures that feature a highly regular hexagonal pattern with a period of 117 nm to 125 nm were found at particular conditions.