Microstructuring of resist double layers by a femtosecond laser ablation and UV lithography hybrid process

摘要

We report on recent results on selective structuring of photoresist with femtosecond laser pulses in combination with conventional UV photolithography. The advantages of both processes can be combined to generate structures covering lateral dimension from the micron scale up to patterns of millimeter size with high quality in a photoresist double layer system. The fabrication process is based on a photoresist multilayer system where a negative photoresist is placed on a thick SU-8 layer. The negative resist layer is patterned by photolithography and the SU-8 layer by means of selective laser ablation, respectively. An additional thin sacrificial layer of photoresist on the top surface serves as a protective coating and enables the removal of debris which is deposited on the top surface during laser structuring. After resist structuring the process parameters of the femtosecond laser is adapted to enable processing of the glass substrate where drilling of vias and the formation of cavities within the glass substrate is carried out, respectively. This enables resist patterning and substrate processing within one laser step offering a fast and flexible process. Laser processing experiments were carried out with a pulse duration of 400 fs and a wavelength of 520 nm. Photolithography was carried out with a standard mask aligner (MA6, SUESS).