Dr. Albrecht Ullrich Profile

Dr. Albrecht Ullrich

at Advanced Mask Technology Ctr GmbH Co KG

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Author

Publications (9)

Proceedings Article | 13 March 2015 Paper

Polarization resolved measurements with the new EUV ellipsometer of PTB

Victor Soltwisch, Andreas Fischer, Christian Laubis, Christian Stadelhoff, Frank Scholze, Albrecht Ullrich

Proceedings Volume 9422, 942213 (2015) https://doi.org/10.1117/12.2085798

KEYWORDS: Extreme ultraviolet, Polarization, Reflectivity, Mirrors, Diffraction, Photomasks, Metrology, Polarizers, Remote sensing, X-rays

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Proceedings Article | 17 October 2014 Paper

Determination of line profiles on photomasks using DUV, EUV, and x-ray scattering

F. Scholze, B. Bodermann, S. Burger, J. Endres, A. Haase, M. Krumrey, C. Laubis, V. Soltwisch, A. Ullrich, J. Wernecke

Proceedings Volume 9231, 92310M (2014) https://doi.org/10.1117/12.2065941

KEYWORDS: Extreme ultraviolet, Deep ultraviolet, Scatterometry, Diffraction, X-rays, Diffraction gratings, Scattering, Photomasks, Polarization, Finite element methods

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Proceedings Article | 17 October 2014 Paper

Black border, mask 3D effects: covering challenges of EUV mask architecture for 22nm node and beyond

Natalia Davydova, Eelco van Setten, Robert de Kruif, Brid Connolly, Norihito Fukugami, Yutaka Kodera, Hiroaki Morimoto, Yo Sakata, Jun Kotani, Shinpei Kondo, Tomohiro Imoto, Haiko Rolff, Albrecht Ullrich, Ramasubramanian Kottumakulal Jaganatharaja, Ad Lammers, Dorothe Oorschot, Cheuk-Wah Man, Guido Schiffelers, Joep van Dijk

Proceedings Volume 9231, 923102 (2014) https://doi.org/10.1117/12.2066299

KEYWORDS: Deep ultraviolet, Reflectivity, Extreme ultraviolet, Photomasks, Reticles, Scanners, Aluminum, Extreme ultraviolet lithography, Atomic force microscopy, Semiconducting wafers

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Proceedings Article | 28 July 2014 Paper

Achievements and challenges of EUV mask imaging

Proceedings Volume 9256, 925602 (2014) https://doi.org/10.1117/12.2072945

KEYWORDS: Reticles, Photomasks, Extreme ultraviolet, Semiconducting wafers, Reflectivity, 3D metrology, Deep ultraviolet, Neodymium, Atomic force microscopy, Scanners

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Proceedings Article | 8 November 2012 Paper

CD control with defect inspection: you can teach an old dog a new trick

Clemens Utzny, Albrecht Ullrich, Jan Heumann, Elias Mohn, Stefan Meusemann, Rolf Seltmann

Proceedings Volume 8522, 85220B (2012) https://doi.org/10.1117/12.965531

KEYWORDS: Critical dimension metrology, Inspection, Photomasks, Scanning electron microscopy, Defect inspection, Spatial resolution, Semiconducting wafers, Control systems, Manufacturing, Data modeling

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Achieving the required critical dimensions (CD) with the best possible uniformity (CDU) on photo-masks has always played a pivotal role in enabling chip technology. Current control strategies are based on scanning electron microscopy (SEM) based measurements implying a sparse spatial resolution on the order of ~ 10^-2 m to 10^-1 m. A higher spatial resolution could be reached with an adequate measurement sampling, however the increase in the number of measurements makes this approach in the context of a productive environment unfeasible. With the advent of more powerful defect inspection tools a significantly higher spatial resolution of 10^-4 m can be achieved by measuring also CD during the regular defect inspection. This method is not limited to the measurement of specific measurement features thus paving the way to a CD assessment of all electrically relevant mask patterns. Enabling such a CD measurement gives way to new realms of CD control. Deterministic short range CD effects which were previously interpreted as noise can be resolved and addressed by CD compensation methods. This in can lead to substantial improvements of the CD uniformity. Thus the defect inspection mediated CD control closes a substantial gap in the mask manufacturing process by allowing the control of short range CD effects which were up till now beyond the reach of regular CD SEM based control strategies. This increase in spatial resolution also counters the decrease in measurement precision due to the usage of an optical system. In this paper we present detailed results on a) the CD data generated during the inspection process, b) the analytical tools needed for relating this data to CD SEM measurement and c) how the CD inspection process enables new dimension of CD compensation within the mask manufacturing process. We find that the inspection based CD measurement generates typically around 500000 measurements with a homogeneous covering of the active mask area. In comparing the CD inspection results with CD SEM measurement on a single measurement point base we find that optical limitations of the inspection tool play a substantial role within the photon based inspection process. Once these shift are characterized and removed a correlation coefficient of 0.9 between these two CD measurement techniques is found. This finding agrees well with a signature based matching approach. Based on these findings we set up a dedicated pooling algorithm which performs on outlier removal for all CD inspections together with a data clustering according to feature specific tool induced shifts. This way tool induced shift effects can be removed and CD signature computation is enabled. A statistical model of the CD signatures which relates the mask design parameters on the relevant length scales to CD effects thus enabling the computation CD compensation maps. The compensation maps address the CD effects on various distinct length scales and we show that long and short range contributions to the CD variation are decreased. We find that the CD uniformity is improved by 25% using this novel CD compensation strategy.

Proceedings Article | 8 November 2012 Paper

Comparison of critical dimension measurements of a mask inspection system with a CD-SEM

Jan Heumann, Albrecht Ullrich, Clemens Utzny, Stefan Meusemann, Frank Kromer, John Whittey, Edgardo Garcia, Mark Wagner, Norbert Schmidt

Proceedings Volume 8522, 85220G (2012) https://doi.org/10.1117/12.977248

KEYWORDS: Critical dimension metrology, Photomasks, Inspection, Semiconducting wafers, Scanning electron microscopy, Optical testing, Electron microscopes, Opacity, Manufacturing, Wafer manufacturing

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Proceedings Article | 25 September 2010 Paper

Improving registration measurement capability by defining a 2D grid standard using multiple registration measurement tools

O. Loeffler, G. Antesberger, A. Ullrich, J. Richter, A. Wiswesser, Masaru Higuchi, Tatsuhiko Kamibayashi, F. Laske, D. Adam, M. Ferber, K.-D. Roeth

Proceedings Volume 7823, 78232K (2010) https://doi.org/10.1117/12.864459

KEYWORDS: Calibration, Metrology, Image registration, Photomasks, Standards development, Double patterning technology, Manufacturing, Lithography, Image processing, Reticles

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Proceedings Article | 25 September 2010 Paper

Detecting measurement outliers: remeasure efficiently

Albrecht Ullrich

Proceedings Volume 7823, 78232I (2010) https://doi.org/10.1117/12.864318

KEYWORDS: Critical dimension metrology, Statistical analysis, Metrology, Optical proximity correction, Photomasks, Pattern recognition, Statistical methods, Manufacturing, Time metrology, Data processing

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Shrinking structures, advanced optical proximity correction (OPC) and complex measurement strategies continually challenge critical dimension (CD) metrology tools and recipe creation processes. One important quality ensuring task is the control of measurement outlier behavior. Outliers could trigger false positive alarm for specification violations impacting cycle time or potentially yield. Constant high level of outliers not only deteriorates cycle time but also puts unnecessary stress on tool operators leading eventually to human errors. At tool level the sources of outliers are natural variations (e.g. beam current etc.), drifts, contrast conditions, focus determination or pattern recognition issues, etc. Some of these can result from suboptimal or even wrong recipe settings, like focus position or measurement box size. Such outliers, created by an automatic recipe creation process faced with more complicated structures, would manifest itself rather as systematic variation of measurements than the one caused by 'pure' tool variation. I analyzed several statistical methods to detect outliers. These range from classical outlier tests for extrema, robust metrics like interquartile range (IQR) to methods evaluating the distribution of different populations of measurement sites, like the Cochran test. The latter suits especially the detection of systematic effects. The next level of outlier detection entwines additional information about the mask and the manufacturing process with the measurement results. The methods were reviewed for measured variations assumed to be normally distributed with zero mean but also for the presence of a statistically significant spatial process signature. I arrive at the conclusion that intelligent outlier detection can influence the efficiency and cycle time of CD metrology greatly. In combination with process information like target, typical platform variation and signature, one can tailor the detection to the needs of the photomask at hand. By monitoring the outlier behavior carefully, weaknesses of the automatic recipe creation process can be spotted.

Proceedings Article | 23 September 2009 Paper

How much is enough? An analysis of CD measurement amount for mask characterization

Albrecht Ullrich, Jan Richter

Proceedings Volume 7488, 74881K (2009) https://doi.org/10.1117/12.830671

KEYWORDS: Critical dimension metrology, Photomasks, Metrology, Tolerancing, Manufacturing, Lead, Mask making, Distance measurement, Photomask technology, Current controlled current source

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Showing 5 of 9 publications

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