Excimer laser ablation patterning of dielectric layers

Highly reflective (HR) dielectric layer systems (HfO2/SiO2) were ablated from fused silica substrates using excimer laser radiation. Clean structures without damage of the substrate are achieved, if standard ArF lasers or short pulse KrF lasers (0.5 ps) are applied. In the case of ns-pulses the dielectric coating to be ablated can be irradiated through the air (‘front side ablation’) or through the substrate (‘rear side ablation’). In the front side configuration the number of layers ablated per pulse at about 1 J/cm2 corresponds roughly to the thermal diffusion length. In the rear side configuration the whole layer system is ablated with one single pulse of 200 mJ/cm2 causing less redeposited debris compared to the front side configuration. Patterns of lines and spaces with a periodicity of less than 10 μm can easily be produced. Patterned layer systems can be applied as highly resistant masks in laser micromachining systems.