12,352 research outputs found
Reduced basis method for computational lithography
A bottleneck for computational lithography and optical metrology are long
computational times for near field simulations. For design, optimization, and
inverse scatterometry usually the same basic layout has to be simulated
multiple times for different values of geometrical parameters. The reduced
basis method allows to split up the solution process of a parameterized model
into an expensive offline and a cheap online part. After constructing the
reduced basis offline, the reduced model can be solved online very fast in the
order of seconds or below. Error estimators assure the reliability of the
reduced basis solution and are used for self adaptive construction of the
reduced system. We explain the idea of reduced basis and use the finite element
solver JCMsuite constructing the reduced basis system. We present a 3D
optimization application from optical proximity correction (OPC).Comment: BACUS Photomask Technology 200
Numerical analysis of nanostructures for enhanced light extraction from OLEDs
Nanostructures, like periodic arrays of scatters or low-index gratings, are
used to improve the light outcoupling from organic light-emitting diodes
(OLED). In order to optimize geometrical and material properties of such
structures, simulations of the outcoupling process are very helpful. The finite
element method is best suited for an accurate discretization of the geometry
and the singular-like field profile within the structured layer and the
emitting layer. However, a finite element simulation of the overall OLED stack
is often beyond available computer resources. The main focus of this paper is
the simulation of a single dipole source embedded into a twofold infinitely
periodic OLED structure. To overcome the numerical burden we apply the Floquet
transform, so that the computational domain reduces to the unit cell. The
relevant outcoupling data are then gained by inverse Flouqet transforming. This
step requires a careful numerical treatment as reported in this paper
A Rigorous Finite-Element Domain Decomposition Method for Electromagnetic Near Field Simulations
Rigorous computer simulations of propagating electromagnetic fields have
become an important tool for optical metrology and design of nanostructured
optical components. A vectorial finite element method (FEM) is a good choice
for an accurate modeling of complicated geometrical features. However, from a
numerical point of view solving the arising system of linear equations is very
demanding even for medium sized 3D domains. In numerics, a domain decomposition
method is a commonly used strategy to overcome this problem. Within this
approach the overall computational domain is split up into smaller domains and
interface conditions are used to assure continuity of the electromagnetic
field. Unfortunately, standard implementations of the domain decomposition
method as developed for electrostatic problems are not appropriate for wave
propagation problems. In an earlier paper we therefore proposed a domain
decomposition method adapted to electromagnetic field wave propagation
problems. In this paper we apply this method to 3D mask simulation.Comment: 9 pages, 7 figures, SPIE conference Advanced Lithography / Optical
Microlithography XXI (2008
Postnatal depression and reproductive success in modern, low-fertility contexts
Background and objectives: Postnatal depression (PND) presents a puzzling phenomenon to evolutionary
anthropologists as it is highly prevalent and yet detrimental to child development and maternal
health. Adaptive explanations have been proposed, but have not been tested with data that directly link
PND to female fertility.
Methodology: A survey was designed to gather complete reproductive histories and retrospective measures
of PND to measure the effects of PND on fitness. Respondents were born between 1930 and 1967,
with the majority based in the UK during their childrearing years. The hypothesis that PND is detrimental
to fitness is assessed using MannâWhitney U tests on completed fertility. Binary logistic regression
modelling is used to test the hypothesis that PND reduces the likelihood of parity progression.
Results: Women experiencing PND at their first or second birth have lower completed fertility, with PND
at the first birth leading to lowered fertility. Logistic regression analyses show that this is the result of
reductions in the likelihood of parity progression to a third birth when PND is experienced at the first
birth or when repeat bouts occur.
Conclusions and implications: Our results call into question adaptationist arguments, contribute to the
growing understanding of the importance of emotional wellbeing to fertility decision making, and given
the economic consequences of markedly below replacement fertility, highlight a potential new source of
financial incentive to invest in screening and preventative measures to ensure good maternal mental
health
Rigorous Simulations of 3D Patterns on Extreme Ultraviolet Lithography Masks
Simulations of light scattering off an extreme ultraviolet lithography mask
with a 2D-periodic absorber pattern are presented. In a detailed convergence
study it is shown that accurate results can be attained for relatively large 3D
computational domains and in the presence of sidewall-angles and
corner-roundings.Comment: SPIE Europe Optical Metrology, Conference Proceeding
Finite-Element Simulations of Light Propagation through Circular Subwavelength Apertures
Light transmission through circular subwavelength apertures in metallic films
with surrounding nanostructures is investigated numerically. Numerical results
are obtained with a frequency-domain finite-element method. Convergence of the
obtained observables to very low levels of numerical error is demonstrated.
Very good agreement to experimental results from the literature is reached, and
the utility of the method is demonstrated in the investigation of the influence
of geometrical parameters on enhanced transmission through the apertures
Metrology of EUV Masks by EUV-Scatterometry and Finite Element Analysis
Extreme ultraviolet (EUV) lithography is seen as a main candidate for
production of future generation computer technology. Due to the short
wavelength of EUV light (around 13 nm) novel reflective masks have to be used
in the production process. A prerequisite to meet the high quality requirements
for these EUV masks is a simple and accurate method for absorber pattern
profile characterization. In our previous work we demonstrated that the Finite
Element Method (FEM) is very well suited for the simulation of EUV
scatterometry and can be used to reconstruct EUV mask profiles from
experimental scatterometric data. In this contribution we apply an indirect
metrology method to periodic EUV line masks with different critical dimensions
(140 nm and 540 nm) over a large range of duty cycles (1:2, ..., 1:20). We
quantitatively compare the reconstructed absorber pattern parameters to values
obtained from direct AFM and CD-SEM measurements. We analyze the reliability of
the reconstruction for the given experimental data. For the CD of the absorber
lines, the comparison shows agreement of the order of 1nm. Furthermore we
discuss special numerical techniques like domain decomposition algorithms and
high order finite elements and their importance for fast and accurate solution
of the inverse problem.Comment: Photomask Japan 2008 / Photomask and Next-Generation Lithography Mask
Technology X
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