Excimer laser micro machining: fabrication and applications of dielectric masks

Excimer laser ablation is a versatile tool for the micro machining of various materials. Mask projection configurations employing dielectric masks allow fast and flexible high power processing. Due to their high reflectivity at the laser processing wavelength, these dielectric masks show superior performance concerning damage threshold and durability compared to chrome on quartz or metal stencil masks. Dielectric masks are fabricated by laser ablation patterning. The highly reflective (HR) layer stack (e.g., HfO2/SiO2 for HR 248 nm) is ablated with high spatial resolution from the quartz substrate applying 193 nm laser irradiation. A resolution of about 2 mu m is achieved allowing for sub-mu m patterning when using this mask in a demagnifying image projection set up for ablation at 248 nm. The application of these masks for laser micro machining is shown. For example single pulse fabrication of diffractive optical elements (DOE) in transparent polymer material is demonstrated. (C) 2000 Elsevier Science B.V. All rights reserved.