Interference-governed electromagnetic-thermal coupling and heat transport in pulse EUV-irradiated multilayer nanofilms

TL;DR

This paper presents an analytical model linking electromagnetic interference effects with heat transport in multilayer nanofilms under EUV irradiation, revealing trade-offs affecting mirror performance and lifetime.

Contribution

It introduces a novel electromagnetic-thermal coupling model that accounts for interference-controlled energy deposition and transient heat conduction in multilayer nanostructures.

Findings

Increasing multilayer period enhances reflectivity but raises temperature.

Interference-driven volumetric absorption causes axial temperature gradients.

The model predicts scaling laws for thermal confinement and mirror lifetime.

Abstract

Mo-Si multilayer mirrors are central to extreme ultraviolet lithography, where nanoscale optical interference and heat accumulation together constrain reflectivity and operational stability. Here we develop an analytical electromagnetic-thermal coupling model that directly links transfer-matrix-based interference-controlled energy deposition with transient heat conduction in EUV-irradiated multilayers. The model reveals a fundamental trade-off whereby increasing the multilayer period number enhances reflectivity but simultaneously elevates temperature by impeding heat dissipation. Interference-driven volumetric absorption further gives rise to pronounced axial temperature gradients and a post-pulse downward migration of the heat-flux maximum, a delayed-heating effect inaccessible to conventional surface-flux-based models. Systematic analysis establishes scaling laws connecting interfacial thermal resistance, beam size, and incident energy density to thermal confinement and temperature rise. By incorporating interfacial compaction kinetics, the model enables a quantitative assessment of mirror lifetime. This work offers a theoretical tool for thermal-optical co-design of multilayer nanostructures including EUV mirrors under pulsed irradiation across a wide spectral range.