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48
proceedings
GrossHB2016
Fourier optics for investigating the impact of roughness to scatterometry
Proc SPIE
2016
Efficient algorithms are proposed for stochastical
investigations of the impact of structure roughness on light
diffraction pattern of photo masks. This is important for the scatterometry,
i.e. the accurate, indirect determination of geometry
parameters from scattered light intensities in wafer metrology.
The sensitivity to roughness increases the smaller the wavelengths
of the incident light are. For EUV scatterometry at 13.5 nm,
many higher diffraction orders can be measured and they are
sensitive to structure details. We calculate the light diffraction
patterns of apertures with many rough slits in the far field.
Applying Fraunhofer approximation, a 2D-Fourier transform of
the light distribution of the aperture plane yields the sought
diffraction pattern. The rough edges of the aperture are created
by means of power spectrum density (PSD) functions used with
a random complex exponential phase term. The comparison
of the calculated light intensities to those of the undisturbed,
’non-rough’ aperture, whose edges are straight lines, reveal a
systematic decrease in terms of the diffraction order and the
standard deviation of the roughness amplitude. Ensembles of
rough apertures with different values for the imposed standard
deviation of the roughness amplitude, the linear correlation
length, and the roughness exponent were examined. Former
results, obtained by rigorous calculations with computational
expensive finite element methods (FEM) have been confirmed.
The sensitivity of the method is demonstrated for bi-periodic
arrays of hole-space structures too.
critical dimensions (CDs), scatterometry, line
edge roughness (LER), Fourier optics.
International Conference on Circuits, Systems, Signal Processing, Communications and Computers (CSSCC '14): Recent Advances in Electrical and Computer Engineering: (2014)
978-1-61804-228-6
H.Gross
S.Heidenreich
M.Baer
proceedings
BodermannEGHKSW2016
Towards traceability in scatterometric-optical dimensional metrology for optical lithography
2016
Currently, the application of scatterometry for dimensional metrology for optical lithography is limited to a relative measurements for process control and development. To establish scatterometry for traceable and absolute dimensional metrology an estimation of the measurement uncertainty is required. In scatterometry, the geometry of the object is deduced from measured light properties after interaction with the object under test. This indirect method requires the solution of an inverse diffraction problem e. g. by nonlinear optimisation. Different aspects have to be considered: Algorithms are required to propagate the uncertainties of the input parameters, the directly measured optical properties, to the output using covariance or Monte-Carlo methods. The model representation of the geometry of the object and inherent model assumptions of the used mathematical methods are essentially imperfect. We present an analysis of uncertainty contributions based on experimental data.
To enable traceable scatterometry in semiconductor industry, we started to develop a wafer based scatterometry standard. Design, suitable materials and calibration procedures for this standard are discussed.
Mikrolithografie, Gitter, Messtechnik
http://www.dgao-proceedings.de
Eindhoven, The Netherlands
113th annual meeting of the DGaO
29 May - 1 June 2012
English
1614-8436
B.Bodermann
J.Endres
H.Gross
M.-A.Henn
A.Kato
F.Scholze
M.Wurm
article
Correlated Diffuse X-ray Scattering from Periodically Nano-Structured Surfaces
Phys. Rev. Lett.
2015
10
21
Laterally periodic nanostructures were investigated with grazing incidence small angle X-ray scattering. Different contributions to the diffuse X-ray scattering pattern were identified: A palm-like structure of scattering sheets caused by resonant diffuse scattering which is correlated to the grating line shape, the so-called Yoneda band caused by a resonant scatter enhancement at the critical angle of total reflection and higher-order Yoneda bands caused by a subsequent diffraction of the Yoneda enhanced surface scattering at the grating. In order to enable the reconstruction of nano-structured surface geometries, the dynamic scatter contributions were modeled using a solver for the time-harmonic Maxwell's equations based on the finite-element method.
http://arxiv.org/abs/1509.02003
English
1
V.Soltwisch
A.Haase
J.Wernecke
J.Probst
M.Schoengen
S.Burger
M.Krumrey
F.Scholze
article
GrossHHBR2015
Modeling aspects to improve the solution of the inverse problem in scatterometry
Discrete and Continuous Dynamical Systems - Series S (DCDS-S)
2015
6
8
3
497 - 519
The precise and accurate determination of critical dimensions (CDs) of photo masks and their uncertainties is relevant to the lithographic process. Scatterometry is a fast, non-destructive optical method for the indirect determination of geometry parameters of periodic surface structures from scattered light intensities. Shorter wavelengths like extreme ultraviolet (EUV) at 13.5 nm ensure that the measured light diffraction pattern has many higher diffraction orders and is sensitive to the structure details. We present a fast non-rigorous method for the analysis of stochastic line edge roughness with amplitudes in the range of a few nanometers, based on a 2D Fourier transform method. The mean scattering light efficiencies of rough line edges reveal an exponential decrease in terms of the diffraction orders and the standard deviation of the roughness amplitude. Former results obtained by rigorous finite element methods (FEM) are confirmed. The implicated extension of the mathematical model of scatterometry by an exponential damping factor is demonstrated by a maximum likelihood method used to reconstruct the geometrical parameters. Approximate uncertainties are determined by employing the Fisher information matrix and additionally a Monte Carlo method with a limited amount of samplings. It turns out that using incomplete mathematical models may lead to underestimated uncertainties calculated by the Fisher matrix approach and to substantially larger uncertainties for the Monte Carlo method.
Scatterometry, FEM, inverse problem, uncertainties, error model, line edge roughness, Fourier optics
English
10.3934/dcdss.2015.8.497
1
H.Gross
S.Heidenreich
M.-A.Henn
M.Baer
A.Rathsfeld
proceedings
hp-finite element method for simulating light scattering from complex 3D structures
Proc. SPIE 9424
2015
3
19
Methods for solving Maxwell’s equations are integral part of optical metrology and computational lithography setups. Applications require accurate geometrical resolution, high numerical accuracy and/or low computation times. We present a finite-element based electromagnetic field solver relying on unstructured 3D meshes and adaptive hp-refinement. We apply the method for simulating light scattering off arrays of high aspect-ratio nano-posts and FinFETs. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Light scattering ; Optical metrology ; Maxwell equations ; Computational lithography
San Jose, California, United States
Metrology, Inspection, and Process Control for Microlithography XXIX
February 22, 2015
English
10.1117/12.2085795
S.Burger
L.Zschiedrich
J.Pomplun
S.Herrmann
F.Schmidt
article
PetrikKFFJPBU2015
Fourier ellipsometry – an ellipsometric approach to
Fourier scatterometry
JEOS
2015
10
An extension of Fourier scatterometry is presented, aiming at increasing the sensitivity by measuring the phase difference between the reflections polarized parallel and perpendicular to the plane of incidence. The ellipsometric approach requires no additional hardware elements compared with conventional Fourier scatterometry. Furthermore, incoherent illumination is also sufficient, which enables spectroscopy using standard low-cost light sources.
English
10.2971/jeos.2015.15002
1
P.Petrik
N.Kumar
M.Fried
B.Fodor
G.Juhasz
S.F.Pereira
S.Burger
H.P.Urbach
proceedings
Determination of line profiles on photomasks using DUV, EUV and X-ray scattering
Proc. SPIE 9231
2014
10
17
Non-imaging techniques like X-ray scattering are supposed to play an important role in the further development of CD metrology for the semiconductor industry. GISAXS provides directly assessable information on structure roughness and long-range periodic perturbations. The disadvantage of the method is the large footprint of the X-ray beam on the sample due to the extremely shallow angle of incidence. This can be overcome by using wavelengths in the extreme ultraviolet (EUV) spectral range which allow for much steeper angles of incidence but preserve the large range of momentum transfer that can be observed. At the Physikalisch-Technische Bundesanstalt (PTB), the available photon energy range extends from 50 eV up to 10 keV at two adjacent beamlines. PTB commissioned a new versatile Ellipso-Scatterometer which is capable of measuring 6” square substrates in a clean, hydrocarbon-free environment with full flexibility regarding the direction of the incident light polarization. The reconstruction of line profiles using a geometrical model with six free parameters, a finite element method (FEM) Maxwell solver and least-squares optimization yielded consistent results for EUV and deep ultraviolet (DUV) scatterometry. For EUV photomasks, the actinic wavelength EUV scatterometry yields particular advantages. A significant polarization dependence of the diffraction intensities for 0th and +1st orders in the geometry with the grating lines perpendicular to the plane of reflection is observed and the 0th order intensity shows sufficient sensitivity to the line width such that a CD-resolution below 0.1 nm is within reach. In this contribution we present scatterometry data for line gratings using GISAXS, and EUV and DUV scatterometry and consistent reconstruction results of the line geometry for EUV and DUV scatterometry. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Deep ultraviolet ; Extreme ultraviolet ; Extreme ultraviolet lithography ; Photomasks ; Scattering ; X-rays ; Scatterometry ; Polarization ; Finite element methods ; Diffraction
Dresden, Germany
30th European Mask and Lithography Conference
June 24, 2014
English
10.1117/12.2065941
F.Scholze
B.Bodermann
S.Burger
J.Endres
A.Haase
M.Krumrey
C.Laubis
V.Soltwisch
A.Ullrich
J.Wernecke
proceedings
Scatterometric characterization of diffractive optical elements
Proc. SPIE 9173
2014
8
27
Diffractive optical elements offer a great way to control light beyond the capabilities of traditional refractive components. Because of the very small feature sizes, the characterization of diffractive optical elements is challenging. Using current invasive methods, such as scanning electron microscope (SEM) or atomic force microscope (AFM), the measurements are slow and potentially destructive to the element. Employing optical scatterometery, the measurements are not only fast and non-destructive but also integrable to inline control of the fabrication and replication processes. In this work we use scatterometer to determine the dimensional parameters of binary diffractive optical elements and compare the results with the parameters obtained with AFM and SEM.
Diffractive optical elements ; Electron microscopes ; Fabrication ; Scanning ; Atomic force microscope
San Diego, California, United States
Instrumentation, Metrology, and Standards for Nanomanufacturing, Optics, and Semiconductors VIII
August 17, 2014
English
10.1117/12.2061699
T.Saastamoinen
H.Husu
J.Laukkanen
S.Siitonen
J.Turunen
A.Lassila
proceedings
Development of a scatterometry reference standard
Proc. SPIE 9132
2014
5
1
Scatterometry is a common technique for dimensional characterisation of nanostructures in the semiconductor industry. Currently this technique is limited to relative measurements for process development and process control. Although the high sensitivity of scatterometry is well known, it is not yet applied for absolute measurements of critical dimensions (CD) and quality control due to the lack of traceability. Thus we aim to establish scatterometry as traceable and absolute metrological method for dimensional measurements. Suitable high quality calibrated scatterometry reference standard samples are currently developed as one important step to enable traceable absolute measurements in industrial applications. The reference standard materials will base either on Si or on Si3N4. A traceable calibration of these standards will be provided by applying and combining different scatterometric as well as imaging calibration methods. First Silicon test samples have been manufactured and characterised for this purpose. The etched Si gratings have periods down to 50 nm and contain areas of reduced density to enable AFM measurements for comparison. We present the current design and first characterisations of structure details and the grating quality based on AFM measurements, optical, EUV and X-Ray scatterometry as well as spectroscopic ellipsometry. Finally we discuss possible final designs and the aimed specifications of the standard samples to face the tough requirements for future technology nodes in lithography. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Scatterometry ; Calibration ; Dimensional metrology ; Extreme ultraviolet ; Extreme ultraviolet lithography ; Lithography ; Nanostructures ; Process control ; Semiconductors ; Silicon
Brussels, Belgium
Optical Micro- and Nanometrology V
April 14, 2014
English
10.1117/12.2052278
B.Bodermann
B.Loechel
F.Scholze
G.Dai
J.Endres
J.Probst
M.Schoengen
M.Krumrey
P. E.Hansen
V.Soltwisch
proceedings
Measurement comparison of goniometric scatterometry and coherent Fourier scatterometry
Proc. SPIE 9132
2014
5
1
Scatterometry is a common tool for the dimensional characterization of periodic nanostructures. In this paper we compare measurement results of two different scatterometric methods: a goniometric DUV scatterometer and a coherent scanning Fourier scatterometer. We present a comparison between these two methods by analyzing the measurement results on a silicon wafer with 1D gratings having periods between 300 nm and 600 nm. The measurements have been performed with PTB’s goniometric DUV scatterometer and the coherent scanning Fourier scatterometer at TU Delft. Moreover for the parameter reconstruction of the goniometric measurement data, we apply a maximum likelihood estimation, which provides the statistical error model parameters directly from measurement data.
Scatterometry ; Deep ultraviolet ; Scanning ; Nanostructures ; Silicon
Brussels, Belgium
Optical Micro- and Nanometrology V
April 14, 2014
English
10.1117/12.2052819
J.Endres
N.Kumar
P.Petrik
M.-A.Henn
B.Bodermann
proceedings
SoltwischWHPSKS2014
Nanometrology on gratings with GISAXS: FEM reconstruction and Fourier analysis
Proc. SPIE 9050
2014
4
2
The aim of the semiconductor industry to decrease the feature size of integrated circuits poses a huge technological endeavor. Consequently, new challenges are arising for metrology on structures in the nanometer regime. Scatterometry is a fast method which provides non-contact non-destructive characterization of structures on photomasks or exposed wafers. However, the determination of important line structure parameters with subnanometer accuracy still needs further investigation. Grazing incidence small-angle X-ray scattering (GISAXS) is a scatterometry technique to measure both vertical and lateral structural features in the nanometer range with high sensitivity. We apply GISAXS to the investigation of structural parameters such as period length, sidewall angle, linewidth and height on silicon gratings. Our test structures with nominal widths of 35 nm to 100 nm and a pitch from 100 nm to 250 nm were fabricated by electron beam lithography. The diffraction patterns have been analyzed by power spectral density analysis which directly yields periodical modulations of the structured surface such as line width or groove width. We also apply a finite element method (FEM) to the diffraction peak intensity of the grating structure obtained with GISAXS for the geometric reconstruction of the line shape. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Finite element methods ; Diffraction ; Nanotechnology ; Scatterometry ; Semiconductors ; Silicon ; X-rays ; Photomasks ; Scattering ; Electron beam lithography
San Jose, California, United States
Metrology, Inspection, and Process Control for Microlithography XXVIII
February 23, 2014
English
10.1117/12.2046212
V.Soltwisch
J.Wernecke
A.Haase
J.Probst
M.Schoengen
M.Krumrey
F.Scholze
proceedings
PetrikKAFPLFU2014
Optical characterization of laterally and vertically structured oxides and semiconductors
SPIE Proceedings Vol. 8987
2014
3
8
Optical techniques have been intensively developed for many decades in terms of both experimental and modeling capabilities. In spectroscopy and scatterometry material structures can be measured and modeled from the atomic (binding configurations, electronic band structure) through nanometer (nanocrystals, long range order) to micron scales (photonic structures, gratings, critical dimension measurements). Using optical techniques, atomic scale structures, morphology, crystallinity, doping and a range of other properties that can be related to the changes of the electronic band structure can most sensitively be measured for materials having interband transition energies in the optical photon energy range. This will be demonstrated by different models for the dielectric function of ZnO, a key material in optoelectronics and in numerous other fields. Using polarimetry such as spectroscopic ellipsometry, sub-nanometer precision has long been revealed for the thickness of optical quality layers. The lateral resolution of spectroscopic ellipsometry is limited (> 50 μm) by the use of incoherent light sources, but using single-wavelength imaging ellipsometry, a sub-micron lateral resolution can be reached. In case of sub-wavelength structures, the morphology (of e.g. porous or nanocrystalline materials) can be characterized using the effective medium theory. For structure sizes comparable to the wavelength, scatterometry is applied in a broad versatility of configurations from specular to angle resolved, from coherent to incoherent, from monochromatic to spectroscopic, from reectometric to polarimetric. In this work, we also present an application of coherent Fourier scatterometry for the characterization of periodic lateral structures.
Doping ; Ellipsometry ; Light sources ; Modeling ; Nanocrystals ; Nanotechnology ; Optoelectronics ; Oxides ; Photons ; Polarimetry
San Francisco, California, United States
Oxide-based Materials and Devices V
February 01, 2014
English
10.1117/12.2042181
P.Petrik
N.Kumar
E.Agocs
B.Fodor
S.F.Pereira
T.Lohner
M.Fried
H.P.Urbach
article
KoopsF2014
An approach towards 3D sensitive AFM cantilevers
Measurement Science and Technology
2014
3
5
25
4
The atomic force microscope (AFM) tapping mode is a highly sensitive local probing technique that is very useful to study and measure surface properties down to the atomic scale. The tapping mode is mostly implemented using the resonance of the first bending mode of the cantilever and therefore provides sensitivity mainly along the direction of this oscillation. Driven by the semiconductor industry, there is an increasing need for accurate measurements of nanoscale structures for side wall characterization by AFM that requires additional sensitivity in the lateral direction. The conventional tapping mode has been augmented by various authors, for example by tilting the cantilever system (Cho et al 2011 Rev. Sci. Instrum. 82 023707) to access the sidewall or using a torsion mode (Dai et al 2011 Meas. Sci. Technol. 22 094009) of the cantilever to provide additional lateral sensitivity. These approaches however trade lateral sensitivity for vertical sensitivity or still lack sensitivity in the remaining lateral direction. We present an approach towards true 3D sensitivity for AFM cantilevers based on simultaneous excitation and optical detection of multiple cantilever resonance modes along three axes. Tuning the excitation of the cantilever to specific frequencies provides a mechanism to select only those cantilever modes that have the desired characteristics. Additionally, cantilever engineering has been used to design and create a substructure within the cantilever that has been optimized for specific resonance behavior around 4 MHz. In contrast to the conventional approach of using a piezo to actuate the cantilever modulation, we present results on photo-thermal excitation using an intensity modulated low-power laser source. By tightly focusing the excitation spot on the cantilever we were able to attain a deflection efficiency of 0.7 nm µW−1 for the first bending mode. The presented approach results in an efficient all optical excitation and deflection detection scheme where both the position of the spot to excite the cantilever and the spot position of the read-out beam provide additional parameters to fully control and optimize the multi-mode structure required for 3D AFM measurements.
English
10.1088/0957-0233/25/4/044001
1
R.Koops
V.Fokkema
article
EndresDHHWB2014
Investigations of the influence of common approximations in scatterometry for dimensional nanometrology
Measurement Science and Technology
2014
3
5
25
4
Scatterometry is a common tool for the dimensional characterization of periodic nanostructures. It is an indirect measurement method, where the dimensions and geometry of the structures under test are reconstructed from the measured scatterograms applying inverse rigorous calculations. This approach is numerically very elaborate so that usually a number of approximations are used. The influence of each approximation has to be analysed to quantify its contribution to the uncertainty budget. This is a fundamental step to achieve traceability. In this paper, we experimentally investigate two common approximations: the effect of a finite illumination spot size and the application of a more advanced structure model for the reconstruction. We show that the illumination spot size affects the sensitivity to sample inhomogeneities but has no influence on the reconstruction parameters, whereas additional corner rounding of the trapezoidal grating profile significantly improves the reconstruction result.
English
10.1088/0957-0233/25/4/044004
1
J.Endres
A.Diener
M.-A.Henn
S.Heidenreich
M.Wurm
B.Bodermann
article
DaiHSHGFB2014
Measurements of CD and sidewall profile of EUV photomask structures using CD-AFM and tilting-AFM
[more] Measurement Science and Technology
2014
3
25
4
Accurate and traceable measurements of critical dimension (CD) and sidewall profile of extreme ultraviolet (EUV) photomask structures using atomic force microscopes (AFMs) are introduced in this paper. An instrument complementarily applied with two kinds of AFM techniques, the CD-AFM and the tilting-AFM, has been developed. High measurement stability of the instrument is demonstrated, for instance, the long-term CD stability is better than 1 nm over 500 successive measurements over 55 h. To traceably calibrate the effective tip geometry, transmission electron microscopes-based method is applied, which uses either the silicon crystal lattice or the structure pitch value calibrated by metrological AFMs as an internal scale. Several grating patterns with different nominal CDs and line/space ratios of an EUV photomask have been measured using the developed methods. A data evaluation method with considered higher order tip effect due to the non-vertical sidewall is introduced. Detailed measurement results of a test EUV photomask, such as middle CD, left and right sidewall angle, feature height, line edge roughness and edge profiles are given. Finally, the AFM results are compared to that of a PTB EUV scatterometer. The comparison of the middle CD yields a linear relation within a spread of only about ±2 nm and an offset of the absolute values below 3 nm. For the sidewall angle, both methods yield consistent results within a range of about 2°.
English
10.1088/0957-0233/25/4/044002
1
G.Dai
K.Hahm
F.Scholze
M.-A.Henn
H.Gross
J.Fluegge
H.Bosse
article
HusuSLSTL2014
Scatterometer for characterization of diffractive optical elements
Measurement Science and Technology
2014
3
25
4
Diffractive optical elements can control light beyond the capabilities of traditional optical components, which offers great opportunities for numerous applications. However, modern functionalities are related to even smaller feature sizes, which causes remarkable challenges for the structure measurements in the nanoscale. The current methods are not optimal for the characterization of diffractive structures. Optical scatterometry, however, would be a good tool for non-destructive characterization, and in particular, for inline process control of the fabrication. In this paper, detailed information about a goniometric scatterometer built at MIKES (Centre for Metrology and Accreditation), basics of the inverse problem approach for solving the parameters of the structure and first measurements for confirming the functionality of the scatterometer as well as the capabilities of it are discussed.
English
DOI: 10.1088/0957-0233/25/4/044019
1
H.Husu
T.Saastamoinen
J.Laukkanen
S.Siitonen
J.Turunen
A.Lassila
article
WerneckeGMK2014
Characterization of an in-vacuum PILATUS 1M detector.
Journal of Synchrotron Radiation
2014
2
12
A dedicated in-vacuum X-ray detector based on the hybrid pixel PILATUS 1M detector has been installed at the four-crystal monochromator beamline of PTB at the electron storage ring BESSY II in Berlin. Due to its windowless operation, the detector can be used in the entire photon energy range of the beamline from 10 keV down to 1.75 keV for small-angle X-ray scattering (SAXS) experiments and anomalous SAXS (ASAXS) at absorption edges of light elements. The radiometric and geometric properties of the detector like quantum efficiency, pixel pitch and module alignment have been determined with low uncertainties. The first grazing incidence SAXS (GISAXS) results demonstrate the superior resolution in momentum transfer achievable at low photon energies.
English
10.1107/S160057751400294X
1
J.Wernecke
C.Gollwitzer
P.Müller
M.Krumrey
article
HeidenreichGHEB2014
A surrogate model enables a Bayesian approach to the inverse problem of scatterometry.
Journal of Physics: Conference Series
2014
490
Scatterometry is an indirect optical method for the determination of photomask geometry parameters from scattered light intensities by solving an inverse problem. The Bayesian approach is a powerful method to solve the inverse problem. In the Bayesian framework estimates of parameters and associated uncertainties are obtained from posterior distributions. The determination the probability distribution is typically based on Markov chain Monte Carlo (MCMC) methods. However, in scatterometry the evaluation of MCMC steps require solutions of partial differential equations that are computationally expensive and application of MCMC methods is thus impractical. In this article we introduce a surrogate model for scatterometry based on polynomial chaos that can be treated by Bayesian inference. We compare the results of the surrogate model with rigorous finite element simulations and demonstrate its convergence. The accuracy reaches a value of lower than one percent for a sufficient fine mesh and the speed up amounts more than two order of magnitudes. Furthermore, we apply the surrogate model to MCMC calculations and we reconstruct geometry parameters of a photomask.
English
10.1088/1742-6596/490/1/012007
1
S.Heidenreich
H.Gross
M.-A.Henn
C.Elster
M.Baer
article
HennGHSEB2014
Improved reconstruction of critical dimensions in extreme ultraviolet scatterometry by modeling systematic errors
Measurement Science and Technology
2014
25
4
Scatterometry is a non-imaging indirect optical method that is frequently used to reconstruct the critical dimensions (CD) of periodic nanostructures, e.g. structured wafer surfaces in semiconductor chip production. To solve the inverse problem, we apply a maximum likelihood estimation, introduced in Henn et al (2012 Opt. Express 20 12771-86). Along with the CD values, further relevant quantities like noise parameters of the measured diffraction intensities and the strength of line roughness can be estimated from the measured scattering efficiencies. We investigate three different models for extreme ultraviolet (EUV) scatterometry at an EUV photo mask with increasing complexity by successively including two major sources of systematic errors, namely line roughness and deviations in the multilayer substrate of the EUV mask. Applying the different models to reconstruct the CDs from both simulation and measurement data, we demonstrate the improvements of the reconstruction in terms of simulated and real measurement data. The inclusion of systematic errors in the maximum likelihood approach to the inverse problem leads to a significant reduction of the variances in the estimated CDs implying reduced measurement uncertainty for scatterometry.
English
10.1088/0957-0233/25/4/044003
1
M.-A.Henn
H.Gross
S.Heidenreich
F.Scholze
C.Elster
M.Baer
article
GrossHHDSB2014
Modelling line edge roughness in periodic line-space structures by Fourier optics to improve scatterometry
JEOS
2014
9
In the present paper, we propose a 2D-Fourier transform method as a simple and efficient algorithm for stochastical and numerical studies to investigate the systematic impacts of line edge roughness on light diffraction pattern of periodic line-space structures. The key concept is the generation of ensembles of rough apertures composed of many slits, to calculate the irradiance of the illuminated rough apertures far away from the aperture plane, and a comparison of their light intensities to those of the undisturbed, ’non-rough’ aperture. We apply the Fraunhofer approximation and interpret the rough apertures as binary 2D-gratings to compute their diffraction patterns very efficiently as the 2D-Fourier transform of the light distribution of the source plane. The rough edges of the aperture slits are generated by means of power spectrum density (PSD) functions, which are often used in metrology of rough geometries. The mean efficiencies of the rough apertures reveal a systematic exponential decrease for higher diffraction orders if compared to the diffraction pattern of the unperturbed aperture. This confirms former results, obtained by rigorous calculations with computational expensive finite element methods (FEM) for a simplified roughness model. The implicated model extension for scatterometry by an exponential damping factor for the calculated efficiencies allows to determine the standard deviation σ_r of line edge roughness along with the critical dimensions (CDs), i.e., line widths, heights and other profile properties in the sub-micrometer range. First comparisons with the corresponding roughness value determined by 3D atomic force microscopy (3D AFM) reveal encouraging results.
English
10.2971/jeos.2014.14003
1
H.Gross
S.Heidenreich
M.-A.Henn
G.Dai
F.Scholze
M.Baer
article
KumarPRERPCU2014
Reconstruction of sub-wavelength features and nano-positioning of gratings using coherent Fourier scatterometry
Optics Express
2014
22
20
24678-24688
Optical scatterometry is the state of art optical inspection technique for quality control in lithographic process. As such, any boost in its performance carries very relevant potential in semiconductor industry. Recently we have shown that coherent Fourier scatterometry (CFS) can lead to a notably improved sensitivity in the reconstruction of the geometry of printed gratings. In this work, we report on implementation of a CFS instrument, which confirms the predicted performances. The system, although currently operating at a relatively low numerical aperture (NA = 0.4) and long wavelength (633 nm) allows already the reconstruction of the grating parameters with nanometer accuracy, which is comparable to that of AFM and SEM measurements on the same sample, used as reference measurements. Additionally, 1 nm accuracy in lateral positioning has been demonstrated, corresponding to 0.08% of the pitch of the grating used in the actual experiment.
English
10.1364/OE.22.024678
1
N.Kumar
P.Petrik
G.K.P.Ramanandan
O.El Gawhary
S.Roy
S.F.Pereira
W.M.J.Coene
H.P.Urbach
article
3
Finite-element based electromagnetic field simulations: Benchmark results for isolated structures
Proc. SPIE
2013
10
9
8880
Photomask Technology 2013
We use a finite-element method to obtain highly converged results for a nano-optical light scattering setup with a non-periodic geometry. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
English
10.1117/12.2026213
S.Burger
L.Zschiedrich
J.Pomplun
F.Schmidt
proceedings
ScholzeSDHG2013
Comparison of CD measurements of an EUV photomask by EUV scatterometry and CD-AFM
Proc. SPIE 8880, Photomask Technology 2013
2013
9
9
EUV scatterometry is a potential high-throughput measurement method for the characterization of EUV photomask structures. We present a comparison of angle resolved extreme ultraviolet (EUV) scatterometry and critical dimension atomic force microscope (CD-AFM) as a reference metrology for measurements of geometrical parameters like line width (CD), height and sidewall angle of EUV photomask structures. The structures investigated are dense and semidense bright and dark lines with different nominal CDs between 140 nm and 540 nm. The results show excellent linearity of the critical dimension measured with both methods within a range of only 1.8 nm and an offset of the absolute values below 3 nm. A maximum likelihood estimation (MLE) method is used to reconstruct the shape parameters and to estimate their uncertainties from the measured scattering efficiencies. The newly developed CD-AFM at PTB allows versatile measurements of parameters such as height, CD, sidewall angle, line edge/width roughness, corner rounding, and pitch. It applies flared tips to probe steep and even undercut sidewalls and employs a new vector approaching probing (VAP) strategy which enables very low tip wear and high measurement flexibility. Its traceability is ensured by a set of calibrated step-height and reference CD standards. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Extreme ultraviolet ; Photomasks ; Scatterometry ; Atomic force microscope ; Scattering ; Metrology
Monterey, California, United States
Photomask Technology 2013
September 10, 2013
English
doi:10.1117/12.2025827
F.Scholze
V.Soltwisch
G.Dai
M.-A.Henn
H.Gross
article
RoyKPU2013
Interferometric coherent Fourier scatterometry: a method for obtaining high sensitivity in the optical inverse-grating problem
Journal of Optics
2013
6
4
15
7
In recent times, coherent Fourier scatterometry has been considered as an emerging optical grating scatterometry technique for semiconductor metrology since it shows large sensitivity owing to its scanning ability. However, further utilization of coherence is possible by making additional measurements using the principle of temporal phase-shifting interferometry. In this paper, through numerical simulation, we show how scanning and interferometry can be coupled together to improve the sensitivity of coherent Fourier scatterometry, to extend its range of applicability and to obtain sufficient information to calculate the complex scattering matrix for all angles of incidences inside the numerical aperture of a microscope objective.
English
10.1088/2040-8978/15/7/075707
1
S.Roy
N.Kumar
S.F.Pereira
H.P.Urbach
article
7
Investigation of microstructured fiber geometries by
scatterometry
Proc. SPIE
2013
5
13
8789
Modeling Aspects in Optical Metrology IV
Hollow-core photonic bandgap fibers guide light using diffraction rather than total internal reflection as is the case with normal single- mode communications fibers. The fibers consist of a hollow capillary (~19 micrometers in diameter) surrounded by capillary (~4 micrometers in diameter) arranged in a honey-comb like structure. The honey-comb structure scatters light in the core such that light within the bandgap wavelengths cannot escape from the core. However, the bandgap properties greatly depend on the accuracy with which the microstructures can be controlled during the fabrication process. For measuring the geometrical properties of hollow core photonic crystal fibers with a honeycomb cladding structure we use an angular scatterometric setup. For analyzing the experimentally obtained data we rigorously compute the scattering signal by solving Maxwell's equations with finite-element methods. This contribution focuses on the numerical analysis of the problem. A convergence analysis demonstrates that we reach highly accurate solutions. Our results show very good qualitative agreement between experimental and numerical results. We furthermore demonstrate concepts for accurately monitoring dimensional parameters in the fiber manufacturing process. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
English
10.1117/12.2020526
P. E.Hansen
S.Burger
article
6
Scatterometry sensitivity analysis for conical diffraction
versus in-plane diffraction geometry with respect to the side wall angle
Proc. SPIE
2013
5
13
8789
Modeling Aspects in Optical Metrology IV
Extreme W scatterometry using radiation in the extreme ultraviolet photon energy range, with wavelengths around 13.5 nm, provides direct information on the performance of EUV optical components, e.g. EUV pho tomasks, in their working wavelength regime. Scatterometry with horizontal diffraction geometry, parallel to the grating lines (conical), and vertical scattering geometry, perpendicular to the lines (in-plane), was performed on EUV lithography mask test structures. Numerical FEM based simulations, using a rigorous Maxwell solver, compare both experimental set-ups with focus on the sensitivity of the diffraction intensities particularly with respect to the side wall angle. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
10.1117/12.2020487
V.Soltwisch
S.Burger
F.Scholze
article
JEndresSMB2013
Numerical investigations of the influence of different commonly applied approximations in scatterometry
Proc. SPIE
2013
5
13
8789
At PTB we investigate the prospects of scatterometric methods for quantitative dimensional metrology of periodic micro- and nanostructures. Commonly applied approximations and simplifications may lead to contributions to the measurement uncertainty or even to systematic measurement errors. Here we present a short overview about the main effects connected with these simplifications. In particular we present numerical investigations of the influence of a finite beam size on the scatterometry results. The results indicate, that an impact of the finite beam size becomes significant only for tightly focused beams with a beam waist radius wo smaller than 10 μm. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
J. Endres and S. Burger and M. Wurm and B. Bodermann
English
10.1117/12.2022108
J.Endres
S.Burger
M.Wurm
B.Bodermann
proceedings
HeidenreichHGBB2013
Alternative methods for uncertainty evaluation in EUV scatterometry
Proc. SPIE 8789
2013
5
13
The precise and accurate determination of critical dimensions of photo masks and their uncertainties is important in the lithographic process to ensure operational reliability of electronic compounds. Scatterometry is known as a fast, non-destructive optical method for the indirect determination of geometry parameters. In recent years novel methods for solving the inverse problem of scatterometry have enabled a more reliable determination of grating parameters. In this article we present results from maximum likelihood parameter estimations based on numerically simulated EUV scatterometry data. We approximately determine uncertainties of these parameters by a Monte Carlo method with a limited amount of samplings and by employing the Fisher information matrix. Furthermore, we demonstrate that the use of incomplete mathematical models may lead to severe distortions in the calculations of the uncertainties by the approximate Fisher matrix approach as well as to substantially larger uncertainties for the Monte Carlo method.
Munich, Germany
Modeling Aspects in Optical Metrology IV
May 13, 2013
English
10.1117/12.2020677
S.Heidenreich
M.-A.Henn
H.Gross
B.Bodermann
M.Baer
proceedings
HennHGBB2013
The effect of line roughness in DUV scatterometry
Proc. SPIE 8789, Modeling Aspects in Optical Metrology IV
2013
5
13
The impact of line-edge (LER) and line-width roughness (LWR) on the measured diffraction patters in extreme ultraviolet (EUV) scatterometry has been investigated in recent publications. Two-dimensional rigorous numerical simulations were carried out to model roughness. Simple analytical expressions for the bias in the mean efficiencies stemming from LER and LWR were obtained. Applying a similar approach for DUV scatterometry to investigate the impact of line roughness we obtain comparable results.
Munich, Germany
Modeling Aspects in Optical Metrology IV
May 13, 2013
English
10.1117/12.2020761
M.-A.Henn
S.Heidenreich
H.Gross
B.Bodermann
M.Baer
proceedings
Advanced finite-element methods for design and analysis of nanooptical structures: Applications
Proc. SPIE 8642
2013
3
5
An overview on recent applications of the finite-element method Maxwell-solver JCMsuite to simulation tasks in nanooptics is given. Numerical achievements in the fields of optical metamaterials, plasmonics, photonic crystal fibers, light emitting devices, solar cells, optical lithography, optical metrology, integrated optics, and photonic crystals are summarized. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Integrated optics ; Nano optics ; Optical lithography ; Optical metamaterials ; Optical metrology ; Photonic crystal fibers ; Photonic crystals ; Plasmonics ; Simulations ; Solar cells
San Francisco, California, USA
Emerging Liquid Crystal Technologies VIII
February 02, 2013
English
10.1117/12.2001094
S.Burger
L.Zschiedrich
J.Pomplun
M.Blome
F.Schmidt
article
2
Fast simulation method for parameter reconstruction in optical metrology
Proc. SPIE
2013
2
24
8681
Metrology, Inspection, and Process Control for Microlithography XXVII
A method for automatic computation of parameter derivatives of numerically computed light scattering signals is demonstrated. The finite-element based method is validated in a numerical convergence study, and it is applied to investigate the sensitivity of a scatterometric setup with respect to geometrical parameters of the scattering target. The method can significantly improve numerical performance of design optimization, parameter reconstruction, sensitivity analysis, and other applications. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
English
10.1117/12.2011154
S.Burger
L.Zschiedrich
J.Pomplun
F.Schmidt
B.Bodermann
article
KumarERPU2013
Phase retrieval between overlapping orders in Coherent Fourier Scatterometry using scanning
JEOS
2013
8
Non-interferometric phase retrieval from the intensity measurements in Coherent Fourier Scatterometry (CFS) is presented using a scanningfocused spot. Formulae to determine the state of polarization of the scattered light and to retrieve the phase difference between overlappingscattered orders are given. The scattered far field is rigorously computed and the functionality of the method is proved with experimentalresults.
English
10.2971/jeos.2013.13048
1
N.Kumar
O.El Gawhary
S.Roy
S.E.Pereira
H.P.Urbach
proceedings
EndresBDGWHS2013
Comparison of DUV scatterometry for CD and edge profile metrology on EUV masks
Proc SPIE
2013
Nürtingen, Germany
FRINGE 2013
8 - 11 September 2013
English
978-3-642-36358-0
10.1007/978-3-642-36359-7_128
J.Endres
B.Bodermann
G.Dai
H.Gross
M.Wurm
M.-A.Henn
F.Scholze
proceedings
GrossHHRB2012_2
Impact of line edge and line width roughness on diffraction intensities in scatterometry
Proc. SPIE 8550
2012
12
18
The characterization of nanostructured surfaces by scatterometry is an established method in wafer metrology. From measured light diffraction patterns, critical dimensions (CD) of surface profiles are determined, i.e., line widths, heights and other profile properties in the sub-micrometer range. As structures become smaller and smaller, shorter wavelengths like extreme ultraviolet (EUV) at 13.5 nm ensure a sufficient sensitivity of the measured light diffraction pattern with regard to the structure details. Obviously, the impact of structure roughness with amplitudes in the range of a few nanometers can no longer be neglected in the course of the profile reconstruction. To model line roughness, i.e., line edge (LER) and line width (LWR) roughness, a large number of finite element (FEM) simulations are performed for domains with large periods, each containing many pairs of line and space with stochastically chosen widths. These structures are composed of TaN -absorber lines with an underlying MoSi -multilayer stack representing a typical EUV mask. The resulting mean efficiencies and the variances of the efficiencies in dependence on different degrees of roughness are calculated. A systematic decrease of the mean efficiencies for higher diffraction orders along with increasing variances are observed. In particular, we obtain a simple analytical expression for the bias in the mean efficiencies and the additional uncertainty contribution stemming from the presence of LER and/or LWR. As a consequence, the bias has to be included into the model to provide accurate values for the reconstructed critical profile parameters. The sensitivity of the reconstructed CDs in respect of roughness is demonstrated by using numerous LER/LWR perturbed datasets of efficiencies as input data for the reconstructions. Finally, the reconstructed critical dimensions are significantly improved toward the nominal values if the scattering efficiencies are bias-corrected.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Line width roughness ; Diffraction ; Scatterometry ; Extreme ultraviolet ; Finite element methods ; Simulations ; Metrology ; Multilayers ; Nanostructuring ; Scattering
Barcelona, Spain
Optical Systems Design 2012
November 26, 2012
English
doi:10.1117/12.981327
H.Gross
M.-A.Henn
S.Heidenreich
A.Rathsfeld
M.Baer
article
HennHGRSB2012
Improved grating reconstruction by determination of line roughness in extreme ultraviolet scatterometry
Opt Lett
2012
12
15
37
24
5229-31
The accurate determination of critical dimensions and roughness is necessary to ensure the quality of photoresist masks that are crucial for the operational reliability of electronic components. Scatterometry provides a fast indirect optical nondestructive method for the determination of profile parameters that are obtained from scattered light intensities using inverse methods. We illustrate the effect of line roughness on the reconstruction of grating parameters employing a maximum likelihood scheme. Neglecting line roughness introduces a strong bias in the parameter estimations. Therefore, such roughness has to be included in the mathematical model of the measurement in order to obtain accurate reconstruction results. In addition, the method allows to determine line roughness from scatterometry. The approach is demonstrated for simulated scattering intensities as well as for experimental data of extreme ultraviolet light scatterometry measurements. The results obtained from the experimental data are in agreement with independent atomic force microscopy measurements.
English
10.1364/OL.37.005229.
1
M.A.Henn
S.Heidenreich
H.Gross
A.Rathsfeld
F.Scholze
M.Baer
article
GrossHHRB2012
Modeling of line roughness and its impact on the diffraction intensities and the reconstructed critical dimensions in scatterometry
Applied Optics
2012
10
20
51
7384-7394
We investigate the impact of line-edge and line-width roughness (LER, LWR) on the measured diffraction intensities in angular resolved extreme ultraviolet (EUV) scatterometry for a periodic line-space structure designed for EUV lithography. LER and LWR with typical amplitudes of a few nanometers were previously neglected in the course of the profile reconstruction. The two-dimensional (2D) rigorous numerical simulations of the diffraction process for periodic structures are carried out with the finite element method providing a numerical solution of the 2D Helmholtz equation. To model roughness, multiple calculations are performed for domains with large periods, containing many pairs of line and space with stochastically chosen line and space widths. A systematic decrease of the mean efficiencies for higher diffraction orders along with increasing variances is observed and established for different degrees of roughness. In particular, we obtain simple analytical expressions for the bias in the mean efficiencies and the additional uncertainty contribution stemming from the presence of LER and/or LWR. As a consequence this bias can easily be included into the reconstruction model to provide accurate values for the evaluated profile parameters. We resolve the sensitivity of the reconstruction from this bias by using simulated data with LER/LWR perturbed efficiencies for multiple reconstructions. If the scattering efficiencies are bias-corrected, significant improvements are found in the reconstructed bottom and top widths toward the nominal values.
English
10.1364/AO.51.007384
1
H.Gross
M.-A.Henn
S.Heidenreich
A.Rathsfeld
M.Baer
article
KaramehmedoviHDKW2012
Profile estimation for Pt submicron wire on rough Si substrate from experimental data
Opt Express
2012
9
10
19
21678-86
An efficient forward scattering model is constructed for penetrable 2D submicron particles on rough substrates. The scattering and the particle-surface interaction are modeled using discrete sources with complex images. The substrate micro-roughness is described by a heuristic surface transfer function. The forward model is applied in the numerical estimation of the profile of a platinum (Pt) submicron wire on rough silicon (Si) substrate, based on experimental Bidirectional Reflectance Distribution Function (BRDF) data.
doi: 10.1364/OE.20.021678
1
M.Karamehmedović
P.E.Hansen
K.Discherl
E.Karamehmedović
T.Wriedt
article
5
Analytical modeling and {3D} finite element simulation of line edge roughness in scatterometry
Appl. Optics
2012
9
The influence of edge roughness in angle-resolved scatterometry at periodically structured surfaces is investigated. A good description of the radiation interaction with structured surfaces is crucial for the understanding of optical imaging processes such as, e.g., in photolithography. We compared an analytical two-dimensional (2D) model and a numerical three-dimensional simulation with respect to the characterization of 2D diffraction of a line grating involving structure roughness. The results show a remarkably high agreement. The diffraction intensities of a rough structure can therefore be estimated using the numerical simulation result of an undisturbed structure and an analytically derived correction function. This work allows to improve scatterometric results for the case of practically relevant 2D structures.
English
10.1364/AO.51.006457
A.Kato
S.Burger
F.Scholze
article
WerneckeSK2012
Direct structural characterisation of line gratings with grazing incidence small-angle x-ray scattering
Rev. Sci. Instrum.
2012
83
Grazing incidence small-angle x-ray scattering (GISAXS) and x-ray reflectometry (XRR) have been used to investigate structural parameters, especially period length, line width, groove width, and line height, of grating test structures in the sub-micron range. The gratings are e-beam written structures on a quartz substrate with a fixed period length, but different line and groove widths, covered by a layer of ruthenium. A Ru layer thickness of 9.4 nm has been determined with XRR. GISAXS was performed in two orientations, with an incident beam alignment perpendicular and parallel to the grating lines. The scattering patterns in parallel orientation have been analysed without numerical simulation by Fourier transformation. The obtained results for line and groove width are in good agreement with nominal values. The analysis method has been validated by analysing simulated scattering data. A superposition of scattering intensities measured for different azimuthal rotation angles close to parallel alignment was used to determine the line height of a grating of 27.3 nm, which is also close to the nominal value. The Fourier analysis procedure opens up the possibility of traceable structure determination with GISAXS in the nanometre range.
http://dx.doi.org/10.1063/1.4758283
English
1
J.Wernecke
F.Scholze
M.Krumrey
article
BodermannHBHGBSEW2012
First steps towards a scatterometry reference standard
Proc. SPIE
2012
8466
English
B.Bodermann
P.-E.Hansen
S.Burger
M.-A.Henn
H. A.Gross
M.Bär
F.Scholz
J.Endres
M.Wurm
article
123456
A maximum likelihood approach to the inverse problem of scatterometry
Opt. Exp.
2012
20
12771-12786
PTB
English
M.-A.Henn
H.Gross
F.Scholze
M.Wurm
C.Elster
M.Bär
article
4
Investigation of {3D} Patterns on {EUV} Masks by Means of
Scatterometry and Comparison to Numerical Simulations
Proc. SPIE
2011
9
19
8166
Photomask Technology 2011
EUV scatterometry is performed on 3D patterns on EUV lithography masks. Numerical simulations of the experimental setup are performed using a rigorous Maxwell solver. Mask geometry is determined by minimizing the difference between experimental results and numerical results for varied geometrical input parameters for the simulations.
English
10.1117/12.896839
S.Burger
L.Zschiedrich
J.Pomplun
F.Schmidt
A.Kato
C.Laubis
F.Scholze
proceedings
BodermannBBDW2011
High precision dimensional metrology of periodic nanostructures using laser scatterometry
2011
9
12
At PTB different laser scatterometers with partly novel and outstanding metrological
capabilities have been developed and are available for high-resolution dimensional
metrology of periodic nanostructures. Two different systems are described and their
metrological potential discussed: a laser diffractometer for pitch calibration and a versatile
goniometric scatterometer for multi-parameter characterisation of nanostructures.
http://www.imeko.org/publications/tc14-2011/IMEKO-TC14-2011-29.pdf
PTB, Braunschweig, GERMANY
10th IMEKO TC14 Symposium on Laser Metrology for Precision Measurement and Inspection in Industry
2011, September 12-14
English
978-3-18-092156-3
B.Bodermann
S.Bonifer
E.Buhr
A.Diener
M.Wurm
proceedings
1
Rigorous simulations of 3D patterns on extreme
ultraviolet lithography masks
2011
5
23
8083
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.
http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1340520
B. Bodermann
Proc. SPIE
Modeling Aspects in Optical Metrology III
English
10.1117/12.889831
S.Burger
L.Zschiedrich
J.Pomplun
F.Schmidt
article
Bodermann 2011
Joint Research on Scatterometry and AFM Wafer Metrology
AIP Conf. Proc.
2011
Volume 1395
319
English
1
B.Bodermann
E.Buhr
H.-U.Danzebrink
M.Bär
F.Scholz
M.Krumrey
M.Wurm
P.Klapetek
P.-E.Hansen
V.Korpelainen
M.van Veghel
A.Yacoot
S.Siitonen
O. El.Gawhary
S.Burger
T.Sastamoinen
article
Scatterometric linewidth measurements on subwavelength gratings
Opticts Letters
submitted
English
1
J.Endres
M.Wurm
A.Diener
B.Bodermann
J.Probst
article
Comparison measurements of a hexangonal 2D Si grating using DUV scatterometry, GISAX, AFM and SEM microscopy
Meas. Sci. Technol.
in_preparation
English
1
D.Bergmann
B.Bodermann
E.Buhr
S.Burger
A.Diener
J.Endres
M.Krumrey
B. P.Ng
F.Scholze
V.Soltwisch
M.Wurm
article
Gsvit – open source software for realistic modeling in nanoscale
Optics Express
in_preparation
English
1
P.Klapetek
M.Valtr
R.Slesinger