EUV-Induced Plasma Dynamics and Contamination Control

Extreme ultraviolet (EUV) lithography employs 13.5 nm photons in a near-vacuum hydrogen background, producing a highly transient, low-density plasma on each exposure pulse. This plasma undergoes rapid ionisation, sheath formation at material surfaces and subsequent decay via ambipolar and free diffusion processes. The resulting ion and radical fluxes can erode multilayer mirrors, reticles and pellicles, degrade reflectivity and deposit carbonaceous films from residual hydrocarbons and water vapour. Confinement within scanner chambers modifies plasma evolution by delaying sheath onset, thus lowering peak ion energies but extending radical exposure. Contamination control strategies combine in situ hydrogen cleaning, optimised background pressure, robust capping layers and real-time diagnostics. Advanced simulations—particularly hybrid particle-in-cell and diffusion models—offer three-dimensional, multi-pulse insights that guide materials selection and chamber design. These efforts support the global drive towards sub-10 nm patterning, extended tool lifetimes and improved process yield through an integrated approach spanning plasma physics, surface chemistry and materials engineering.

Research from Nature Portfolio

Recent studies have examined the resilience of optical coatings under ion bombardment representative of EUV-induced plasmas. Investigations of TiO₂/Al bilayer coatings subjected to helium ions at varied keV energies revealed that damage peaks at intermediate energies due to maximised interfacial stress. Detailed optical, morphological and structural analyses demonstrated that capping layer selection and interface engineering are critical to mitigating irradiation-induced degradation. These findings inform the design of multilayer mirrors with enhanced lifetime under repeated EUV-plasma exposure.

EUV-Induced Plasma Dynamics and Contamination Control publication trend

The graph below shows the total number of articles in euv-induced plasma dynamics and contamination control across all publications each year (not limited to Nature Index journals).

Technical terms

EUV (Extreme Ultraviolet): Electromagnetic radiation around 13.5 nm used for high-resolution lithography. Plasma sheath: The boundary layer near a surface where electric fields accelerate ions toward or away from that surface. Ambipolar diffusion: Coupled transport of electrons and ions under a self-generated electric field that maintains quasi-neutrality. Free diffusion: Independent motion of charged particles once ambipolar fields have collapsed below a critical density. Multilayer mirror: A stack of alternating thin films (e.g., Mo/Si) engineered for high reflectivity at EUV wavelengths. Pellicle: A thin, transparent membrane that shields reticles from contamination within lithography tools.

References

1. Evaluation of H2 Plasma‐Induced Damage in Materials for EUV Lithography. Advanced Materials Interfaces (2023).
2. EUV-Induced Plasma: A Peculiar Phenomenon of a Modern Lithographic Technology. Applied Sciences (2019).
3. EUV-induced hydrogen plasma: pulsed mode operation and confinement in scanner. Journal of Micro/Nanopatterning Materials and Metrology (2021).
4. Transition from ambipolar to free diffusion in an EUV-induced argon plasma. Applied Physics Letters (2020).
5. Detection and characterization of carbon contamination on EUV multilayer mirrors.. Optics Express (2009).