Multiphase flow challenges in immersion lithography

Immersion lithography, which utilizes a liquid medium between the projection lens and the wafer, remains a cornerstone of advanced semiconductor manufacturing, enabling the continued scaling of process nodes from 45 nm down to 7 nm and beyond. However, the localized immersion technology essential for high-throughput and high-yield production introduces complex multiphase flow challenges that critically affect process stability and defect control. Rather than analyzing defects in isolation, this review offers a unified perspective on defect generation and suppression by examining the fundamental multiphase flow dynamics. It first addresses three primary gas–liquid issues: liquid leakage, flow-induced vibration, and bubble entrainment, elucidating their physical origins and summarizing established suppression methodologies. The discussion then shifts to solid–liquid challenges, including particulate contamination, watermark formation, and film peeling, providing an overview of recent advances in control strategies. By integrating theoretical fluid mechanics with technical progress, this review provides a structured framework for understanding multiphase flow in confined immersion environments, serving as a reference for optimizing defect control and guiding the design of next-generation immersion lithography systems.