PAG distribution in EUV photoresist and underlayer by hybrid x-ray reflectivity and x-ray standing wave approach

The EUV photoresist (PR) is a light-sensitive film that changes structure when exposed to light, used for creating masks to etch nanostructures, such as semiconductor components. The PR in this study is a prototype organic chemically amplified resist (CAR) for extreme ultraviolet lithography (EUVL), consisting of a modified poly(hydroxystyrene) copolymer blended with tert-butyl methacrylate, a photoacid generator (PAG) containing sulfur (S), and a base quencher. This work aims to study the distribution of PAG across the PR thickness and the interaction between the PR and underlayer after EUV exposure by tracing sulfur fluorescence under x-ray standing wave (XSW) conditions. The modulation of sulfur fluorescence by XSW reveals its distribution within the film, while X-ray reflectivity provides electron density profiles. Two sample types (PR/underlayer and PR/underlayer/x-ray waveguide structure) were prepared on a Si substrate. One piece of each sample type was exposed to EUV radiation, while the other remained unexposed. The results and analysis tolerances will be presented, along with the benefits of complementary measurements.