Modeling and evaluation for the infrared suppression ratio of an EUV collector with integrated spectral purity filters

The suppression of infrared (IR) radiation represents a significant functionality in state-of-the-art extreme ultraviolet (EUV) collectors. This study develops an analytical method to define the infrared suppression ratio (IRSR) and provides a systematic evaluation of IR-suppression performance in large-aperture EUV collectors with integrated spectral purity filters (SPFs). By introducing the concept of linear irradiance (LI), the proposed IRSR metric conveniently incorporates and decouples critical parameters, including the collector geometry, radiation source characteristics, Bragg multilayer reflectance, and grating diffraction efficiency. Parametric decomposition enables the precise identification of both the operational mechanisms and quantitative contributions of individual factors affecting IRSR. The method facilitates spatially resolved IRSR analysis and global IRSR evaluations of conventional collector configurations. This work provides practical guidelines for enhancing the IR suppression capabilities in EUV lithography systems and paves the way for IRSR metrology.