Micro patterning of fused silica by laser ablation mediated by solid coating absorption

Precise patterning by laser ablation requires sufficient absorption. For weak absorbers like fused silica indirect methods using external absorbers have been developed. A novel approach using a solid SiO absorber coating is described. Irradiation by an ArF excimer laser ( wavelength 193 nm) is leading to ablation of the coating and, at sufficiently high fluence, of the fused silica substrate. The remaining coating in the unexposed areas is removed afterwards by large area irradiation. The fluence threshold for substrate ablation using a 28 nmthick absorber layer is about 1.1 J/cm(2). Single pulse ablation rates of up to 800 nm and a surface roughness of R-a < 5 nm are obtained. High resolution grating patterns with 400 nm period and a modulation depth of 80 nm are possible. The process can be described as controlled plasma mediated ablation.