Establishing a filter evaluation methodology targeting polymer purification of EUV lithography materials

Continued momentum in the development of EUV photolithography toward high volume manufacturing has increased photoresist purity requirements that accelerate improvements in resolution, sensitivity, and line edge roughness. Previous research indicates 1,2,3 that the composition of photoresist materials is a major contributor to stochastic effects as semiconductor device critical dimensions decrease. Photoresist is a mixture of small molecules of PAG (photo acid generator) and quencher, and large polymer molecules, whose molecular weight can pose significant challenges to filtration and purification operations. It is critical to maintain the compositional balance, stability, and uniformity of photoresist to ensure expected lithographic performance. Contamination control (filtration + purification) technology is important to maintain a material's purity, removal of undesired species, to improve lithographic performance. This paper describes research to develop a new filter evaluation method to understand and assess interactions of filters with photochemicals. The study investigates the ability of various filtration materials to improve polymer uniformity in an EUV polymer analogue. This study also demonstrates the efficacy of optimized filtration design to capture different contamination sources and improve polymer distribution uniformity, providing recommendations to reduce contaminants and their impact on stochastic issues.