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A simple and selective new technique for atomic hydrogen flux measurements in a hydrogen plasma environment is introduced and demonstrated in this work. This technique works by measuring the etching rate of an amorphous carbon film and translating this to an incoming hydrogen radical flux through a well-defined carbon etch yield per radical. Ions present in the plasma environment have a much higher etch yield than radicals do. For that reason, suppression of the ion flux toward the carbon film is crucial to ensure that the observed carbon etch rate is dominated by atomic hydrogen etching. It is demonstrated that this can be achieved using a simple cylindrical pipe (hereinafter "chimney") in which a bend is introduced to enforce ion–wall collisions, neutralizing the ions. The chimney is made out of Macor, a material with low catalytic surface activity, to preserve the incoming atomic hydrogen flux while effectively suppressing ions. Ultimately, the etching sensor is deployed in a radio frequency inductively coupled hydrogen plasma operated at low pressure (1–10 Pa). Atomic hydrogen fluxes are measured and compared with heat flux sensor and vacuum ultraviolet absorption spectroscopy measurements in the same setup. All sensors agreed within a factor 4 in the atomic hydrogen flux range 1019 to 1021 m−2 s−1. [ABSTRACT FROM AUTHOR]

Since the introduction of extreme ultraviolet (EUV) lithography (EUVL), the inevitable presence of EUV-induced plasmas inside the lithography tools impacts the operation of EUV optical components. EUV-induced plasmas are created everywhere in the optical path due to the ionizing interaction between the high energy (92 eV) EUV photons and the tools' background gas, which typically is hydrogen gas at a pressure of 1–10 Pa. From a physical point of view, the main impact of the plasma is due to the presence of ions that imping the plasma-facing surfaces. Experimental research into the fluence and energy distribution functions (IEDFs) of ions from EUV-induced plasmas has been limited to time-averaged measurements. In this Letter, we present time-resolved measurements of IEDFs for H+, H2+, and H3+ ions from an EUV-induced plasma in pure hydrogen gas. To this end, an electrostatic quadrupole plasma (EQP) analyzer has been used. The measurements pinpointed momentary fluxes up to three orders of magnitude higher than earlier reported average ion fluxes. In addition, the mean ion energy was unexpectedly found to remain elevated up to 50 μs after the gas had been irradiated with EUV photons. Also, it was shown that the EQP detects H2+ ions on time scales much larger than expected. The presented results are valuable not only for the understanding of elementary processes regarding EUV-induced plasmas interacting with surfaces but also for simulating and predicting the impact of EUV-induced plasma on the lifetime and stability of optical components in EUVL. [ABSTRACT FROM AUTHOR]

This work reports on the measurements of ion flux composition and ion energy distribution functions (IEDFs) at surfaces in contact with hydrogen plasmas induced by extreme ultraviolet (EUV) radiation. This special type of plasma is gaining interest from industries because of its appearance in extreme ultraviolet lithography tools, where it affects exposed surfaces. The studied plasma is induced in 5 Pa hydrogen gas by irradiating the gas with short (30 ns) pulses of EUV radiation ( λ = 10–20 nm). Due to the low duty cycle (10–4), the plasma is highly transient. The composition and IEDF are measured using an energy resolved ion mass spectrometer. The total ion flux consists of H + , H 2 + , and H 3 + . H 3 + is the dominant ion as a result of the efficient conversion of H 2 + to H 3 + upon collision with background hydrogen molecules. The IEDFs of H 2 + and H 3 + appear similar, showing a broad distribution with a cut-off energy at approximately 8 eV. In contrast, the IEDF of H+ shows an energetic tail up to 18 eV. Most probably, the ions in this tail gain their energy during their creation process by photoionization and dissociative electron impact ionization. [ABSTRACT FROM AUTHOR]