Abstract

Femtosecond laser pulses permit laser ablation almost free of any heat load to the material, which allows the structuring of various materials with high resolution and good edge definition. We present recent results on selective laser ablation of thick photoresists (AZ-Types) from dielectric substrates as a critical process step in MEMS (micro electromechanical systems) fabrication, capitalizing on the different ablation thresholds of the resist layer and the substrate material. The laser used was an ultrafast pulsed Yb:Glass regenerative amplifier with a pulse duration of 300 fs (HighQLaser Inc.). The experiments were carried out with the second harmonic radiation (520 nm). The beam (Gaussian) was focused on the sample surface by a single lens with the pattern transfer performed by suitable scanning algorithms. By carefully choosing the pulse fluence to be in the window between the ablation thresholds of the resist and the substrate (glass), respectively, we were able to structure thick photoresist selectively without affecting the substrate.

© 2007 IEEE