Sub-micrometer structuring of surfaces with deep UV lasers

The requirements for the resolution of direct laser structuring are constantly growing and are now firmly in the sub-μm range. The most effective way to achieve such high resolution is the use of laser wavelengths in ultraviolet and deep ultraviolet (DUV) range. As the power of excimer and solid-state lasers continues to increase, not only indirect structuring, such as photolithography, but also direct ablation over large areas is becoming efficient. Still, efficient use of the available laser intensity is required to achieve high throughput of the nanostructuring tools. The contribution will discuss different approaches for sub-μm structuring with DUV radiation, including microscanners and proximity phase masks. The latter is a method that can provide sub-wavelength resolution while minimizing the system’s power loss. Unlike absorber-based masks that absorbs at least 50% of the incoming radiation, phase shift masks redistribute the energy with up to 90% total efficiency. Both one-dimensional and two-dimensional periodic patterns on 100 nm-scale can then be created over large areas, if illumination and process parameters are suitably chosen. The contribution will discuss the theoretical and practical limits of the technology and will demonstrate several selected applications of the technology on basis of high-power excimer and USP solid-state laser systems COMPEX and HyperRapid from Coherent.