Production of innovative geometries with UV lasers

摘要

Excimer lasers are proven tools to machine 2 1/2-D microstructures with variable lateral dimensions. Therefore developed techniques are limited in the vertical dimension since material is removed along the optical axis perpendicular to the target plane. This paper presents 3-D structures produced with such UV-lasers. In contrast to optical set-ups for machining 2 1/2-D structures, this approach tilts the target plane and ablates material underneath the target superificies. The tilting angle adds two major difficulties to laser machining: the distortion of the image on the target and the alteration of the ablation cross section. These two difficulties were studied in experiments with different tilting angles β_L between target plane and optical axis of the laser. The impact of β_L was identified on the achieved geometry of 3-D structures. A first theoretical approximation integrates the material reflectance and the target cross-section in order to give an estimation of the influence of further effects within the ablation process. This theoretical analysis is a starting point for producing undercutting structures and can additionally be applied to changeable shaped surfaces. Such complex 3-D structures have the potential to be used in micro-tribology as well as in micro guidance systems and are estimated being an important step in micro-mechanics.