Laser-Induced Backside Wet Etching of Transparent Materials with Organic and Metallic Absorbers

Abstract

Laser-induced backside wet etching (LIBWE) allows the high-quality etching of transparent materials for micro- and nanopatterning. Recent own results of LIBWE with hydrocarbon and metallic absorbers (H- and M-LIBWE) are summarized and compared with selected results of other groups regarding the etching process and the etched surface. Significant results on the impact of the liquid absorber, the material and the wavelength, and the pulse length of the laser to the etching are selected for this comparison. The etching of submicron-sized periodic structures in sapphire and fused silica with interference techniques and the selection of the preferred method in dependence on the material and the processing goal discussed. The experimental results are discussed on a thermal model considering both interface and volume absorption of the laser beam. These results have the conclusion that the etching at M-LIBWE is mainly due to material melting and evaporation whereas at H-LIBWE, a modified near-surface region with a very high absorption is ablated.