422 research outputs found
Characterization of carbon contamination under ion and hot atom bombardment in a tin-plasma extreme ultraviolet light source
Molecular contamination of a grazing incidence collector for extreme
ultraviolet (EUV) lithography was experimentally studied. A carbon film was
found to have grown under irradiation from a pulsed tin plasma discharge. Our
studies show that the film is chemically inert and has characteristics that are
typical for a hydrogenated amorphous carbon film. It was experimentally
observed that the film consists of carbon (~70 at. %), oxygen (~20 at. %) and
hydrogen (bound to oxygen and carbon), along with a few at. % of tin. Most of
the oxygen and hydrogen are most likely present as OH groups, chemically bound
to carbon, indicating an important role for adsorbed water during the film
formation process. It was observed that the film is predominantly sp3
hybridized carbon, as is typical for diamond-like carbon. The Raman spectra of
the film, under 514 and 264 nm excitation, are typical for hydrogenated
diamond-like carbon. Additionally, the lower etch rate and higher energy
threshold in chemical ion sputtering in H2 plasma, compared to
magnetron-sputtered carbon films, suggests that the film exhibits diamond-like
carbon properties.Comment: 18 pages, 10 figure
Graphene defect formation by extreme ultraviolet generated photoelectrons
We have studied the effect of photoelectrons on defect formation in graphene
during extreme ultraviolet (EUV) irradiation. Assuming the major role of these
low energy electrons, we have mimicked the process by using low energy primary
electrons. Graphene is irradiated by an electron beam with energy lower than 80
eV. After e-beam irradiation, it is found that the D peak, I(D), appears in the
Raman spectrum, indicating defect formation in graphene. The evolution of
I(D)/I(G) follows the amorphization trajectory with increasing irradiation
dose, indicating that graphene goes through a transformation from
microcrystalline to nanocrystalline and then further to amorphous carbon.
Further, irradiation of graphene with increased water partial pressure does not
significantly change the Raman spectra, which suggests that, in the extremely
low energy range, e-beam induced chemical reactions between residual water and
graphene is not the dominant mechanism driving defect formation in graphene.
Single layer graphene, partially suspended over holes was irradiated with EUV
radiation. By comparing with the Raman results from e-beam irradiation, it is
concluded that the photoelectrons, especially those from the valence band,
contribute to defect formation in graphene during irradiation.Comment: appears in Journal of Applied Physics 201
Self-contained in-vacuum in situ thin film stress measurement tool
A fully self-contained in-vacuum device for measuring thin film stress in situ is presented. The stress was measured by measuring the curvature of a cantilever on which the thin film was deposited. For this, a dual beam laser deflectometer was used. All optics and electronics needed to perform the measurement are placed inside a vacuum-compatible vessel with the form factor of the substrate holders of the deposition system used. The stand-alone nature of the setup allows the vessel to be moved inside a deposition system independently of optical or electronic feedthroughs while measuring continuously. A Mo/Si multilayer structure was analyzed to evaluate the performance of the setup. A radius of curvature resolution of 270 km was achieved. This allows small details of the stress development to be resolved, such as the interlayer formation between the layers and the amorphous-to-crystalline transition of the molybdenum which occurs at around 2 nm. The setup communicates with an external computer via a Wi-Fi connection. This wireless connection allows remote control over the acquisition and the live feedback of the measured stress. In principle, the vessel can act as a general metrology platform and add measurement capabilities to deposition setups with no modification to the deposition system
Numerical and experimental studies of the carbon etching in EUV-induced plasma
We have used a combination of numerical modeling and experiments to study
carbon etching in the presence of a hydrogen plasma. We model the evolution of
a low density EUV-induced plasma during and after the EUV pulse to obtain the
energy resolved ion fluxes from the plasma to the surface. By relating the
computed ion fluxes to the experimentally observed etching rate at various
pressures and ion energies, we show that at low pressure and energy, carbon
etching is due to chemical sputtering, while at high pressure and energy a
reactive ion etching process is likely to dominate
Narrow-band Borrmann multilayer filters for monitoring of EUV sources
EUV sources currently under development for high volume manufacturing are based on hot plasmas that produce next to 13.5 nm also broadband blackbody radiation and out-of-band line emissions.\ud
For the accurate monitoring of the in-band (13.5 nm ± 2%) radiation power, narrow-band-pass filters are required. Standard filters such as absorptive thin layers can provide neither very narrow bandwidths, nor wavelength selectivity.\ud
We propose an approach based on the Borrmann effect applied to multilayer stacks. This effect relies on the matching of the standing wave field within the multilayer stack with the structure: the minima of the wave field intensity are placed in the center of the absorbing layers, resulting in a resonant decrease in absorption and a narrow-band transmission spectrum for a specific wavelength.\ud
We show calculated transmission spectra of Borrmann filters optimized for different bilayer materials, bandwidths, transmissions and wavelengths
Plasma probe characteristics in low density hydrogen pulsed plasmas
Probe theories are only applicable in the regime where the probe's
perturbation of the plasma can be neglected. However, it is not always possible
to know, a priori, that a particular probe theory can be successfully applied,
especially in low density plasmas. This is especially difficult in the case of
transient, low density plasmas. Here, we applied probe diagnostics in
combination with a 2D particle-in-cell model, to an experiment with a pulsed
low density hydrogen plasma. The calculations took into account the full
chamber geometry, including the plasma probe as an electrode in the chamber. It
was found that the simulations reproduce the time evolution of the probe IV
characteristics with good accuracy. The disagreement between the simulated and
probe measured plasma density is attributed to the limited applicability of
probe theory to measurements of low density pulsed plasmas. Indeed, in the case
studied here, probe measurements would lead to a large overestimate of the
plasma density. In contrast, the simulations of the plasma evolution and the
probe characteristics do not suffer from such strict applicability limits.
These studies show that probe theory cannot be justified through probe
measurements
Analyse van de onderhoudskosten van leidingen, in enkele Drentse waterschappen over het jaar 1965
In verband met de flink gestegen onderhoudskosten van leidingen voor waterschappen werd besloten over te gaan tot een systematische bijhouding van het onderhoud van vijf waterschappen over het jaar 1963: De Oostmoersche Vaart, het Middenveld, de Wold Aa, de Vledder- en Wapserveense Aa en het Riegmeer
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