Time-resolved spectroscopic investigation of N2/H2 nanosecond pulsed discharges and EUV-induced low-temperature plasmas

Extreme ultraviolet (EUV) lithography is central to advanced semiconductor manufacturing, yet the low-density plasmas triggered by EUV photons in scanner-relevant environments remain only partially characterised. Their transient, photon-driven nature complicates invasive diagnostics and makes equilibrium assumptions unreliable. This thesis addresses this gap by developing and applying optical emission spectroscopy (OES) to EUV-induced plasmas in (\mathrm{H_2}), (\mathrm{N_2}), and (\mathrm{H_2}/\mathrm{N_2}) mixtures, and by benchmarking the results against two complementary reference platforms: nanosecond pulsed discharges (NPD) and a mono-energetic electron-beam radiation (EBR) source. The overarching goal is to separate driver-specific spectral fingerprints from shared low-pressure kinetics, and to identify spectroscopic diagnostics that are robust, quantitative, and deployable under tool-relevant constraints. At the core of the work is a calibrated and internally consistent OES framework spanning the three drivers (NPD, EUV irradiation, and EBR), supported by instrumental-function characterisation and forward modelling of spectra. The (\mathrm{N_2}) Second Positive (SPS) and (\mathrm{N_2^+}) First Negative (FNS) band systems, together with the (\mathrm{H_2}) Fulcher-(\alpha) system, are used as sensitive probes of excitation pathways and as rotational and vibrational descriptors where these concepts remain meaningful. The hydrogen Balmer series is employed to track temporal evolution and relative changes in excitation. The thesis also clarifies where simplified interpretations break down in pulsed, non-stationary plasmas: non-Boltzmann populations and potentially misleading “corona-like” estimates motivate collisional–radiative and kinetic modelling. By combining platform-specific insights with cross-platform comparisons, the thesis distinguishes spectroscopic signatures that are generic to low-pressure (\mathrm{H_2}/\mathrm{N_2}) plasmas from those tied to the driving mechanism. The resulting datasets provide experimental benchmarks and boundary conditions for model development, and support a pathway toward model-guided, non-perturbative plasma monitoring in EUV scanner environments. While driven by industrial questions and carried out in collaboration with ASML and partner laboratories, the diagnostic strategies and several physical conclusions are intended to be transferable to other non-thermal plasmas in nitrogen–hydrogen mixtures.

Grantor dc:publisher

Università degli studi di Trento

Year dc:date

2026

Author dc:creator

• Maestri, Luca

Contributors dc:contributor

• Martini, Luca Matteo

• Extreme ultraviolet (EUV) lithography, EUV-induced plasmas, low-temperature (non-thermal) plasmas, optical emission spectroscopy (OES), H2/N2 mixtures, nanosecond pulsed discharges (NPD), electron-beam radiation (EBR), time-resolved spectroscopy, rotational and vibrational temperatures, molecular band spectroscopy (N2 SPS, N2+ FNS, H2 Fulcher-α), Balmer series emission, collisional–radiative modelling, kinetic modelling, plasma diagnostics

Statement dc:rights

• info:eu-repo/semantics/openAccess
• license:Tutti i diritti riservati (All rights reserved)
• license uri:iris.PRI01

Language dc:language

eng

Identifier

http://dx.doi.org/10.15168/11572_476010
10.15168/11572_476010

OAI identifier oai:identifier

oai:iris.unitn.it:11572/476010