Dr. J. Alexander Liddle Profile

Dr. J. Alexander Liddle

Scientific Director, Microsystems&Nanotechnology at National Institute of Standards and Technology

SPIE Involvement:

Conference Chair | Editor | Author

Area of Expertise:

Nanofabrication , DNA Self-assembly , Lithography , Nanomanufacturing , Materials Science

Publications (50)

Proceedings Article | 13 March 2024 Presentation

Single molecule orientational microscopy: an accurate measurement?

Muneesh Maheshwari, Kishalay Mahato, John Fourkas, J. Alexander Liddle, Henri Lezec, Dhruv Fomra

Proceedings Volume PC12849, PC1284903 (2024) https://doi.org/10.1117/12.3001259

KEYWORDS: Molecules, Measurement uncertainty, Point spread functions, Fluorophores, Image analysis, Background noise, Proteins, Polarization density, Physical phenomena, Photonic nanostructures

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Proceedings Article | 30 April 2023 Presentation

A total shift show: submilliradian tilt goniometry in scanning electron microscopy

Andrew Madison, John Villarrubia, Daron Westly, Ronald Dixson, Craig Copeland, John Gerling, Katherine Cochrane, Alan Brodie, Lawrence Muray, J. Alexander Liddle, Samuel Stavis

Proceedings Volume 12496, 1249606 (2023) https://doi.org/10.1117/12.2673963

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Proceedings Article | 13 June 2022 Presentation

Dude, where’s my beam? Placement accuracy by localization microscopy

Andrew Madison, Craig Copeland, Ronald Dixson, B. Robert Ilic, J. Alexander Liddle, Samuel Stavis

Proceedings Volume PC12054, PC120540I (2022) https://doi.org/10.1117/12.2640143

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Beam placement accuracy is fundamental to advanced lithography and patterning. As applications of focused ion beams in semiconductor manufacturing and adjacent topics become more demanding, our titular question on the unknown whereabouts of a beam becomes more pressing to answer. Such a question may seem frivolous, but in reality, is quite serious and nontrivial to answer. In a previous study, we identified micrometer-scale systematic errors of feature placement by our focused ion beam across an ultrawide patterning field. Such errors are of particular concern for machining standards that provide reference positions, such as aperture arrays for optical microscopy. , Conversely, our recent advances of localization traceability present a new opportunity to not only measure but also improve placement accuracy. In the present study, we quantitate feature positions by critical-dimension localization microscopy with ultrahigh throughput, revealing complex errors that extend to appalling values of several micrometers across a submillimeter field. We introduce a novel correction that reduces scale errors by three orders of magnitude and distortion errors by more than a factor of 40, dramatically improving the placement accuracy of our focused ion beam. Although this improvement occurs in a research laboratory context and for optical microscopy standards, our methods have broad implications for advanced lithography and patterning. We begin by designing a square array with a lateral extent of 200 µm by 200 µm, a nominal pitch of 2502 nm, and apertures with a nominal diameter of 500 nm. This value of pitch separates aperture centers by an integer number of pixels across our wide patterning field and separates the aperture images beyond the resolution limit for optical microscopy and localization analysis. After fabrication, we trans-illuminate the aperture array, localize each aperture, and register the resulting positions with those of the design through a rigid transformation. This analysis shows total errors with magnitudes exceeding 2 µm, with root-mean-square values of 528.9 nm in the x direction and 1007.7 nm in the y direction (Figure 1a,c-d). A similarity transformation between the experimental and nominal positions distinguishes errors of uniform scale and complex distortion, returning the pitch of the experimental array as 2472.01 nm ± 0.27 nm, which is a scale error of 1.20 %, with additional systematic errors of distortion as large as approximately 1 µm and with root-mean-square values of 399.3 nm in both the x and y directions (Figure 1c-d). We report uncertainties as 68 % coverage intervals. We modify the array design to negate these errors and improve placement accuracy, uniformly increasing the array pitch to account for the 1.20 % scale error and achieve a nominal pitch of 2500 nm. We model the distortion errors by an interpolant that adjusts the design position of each aperture and enables general correction within the extents of our sampling field. We machine and measure a new array and apply a similar analysis, registering the localization data with the new design. We measure a pitch of 2500.03 nm ± 0.27 nm, corresponding to a scale error of 0.001 %, and distortion errors of up to approximately 40 nm and with root-mean-square values of 9.0 nm in the x direction and 9.4 nm in the y direction (Figure 1b,c-d). In this way, we have found our focused ion beam, which had gone several micrometers astray, and returned it to its proper place to within a few tens of nanometers.

Proceedings Article | 22 February 2021 Presentation

Nucleic acid nanofabrication: existential angst and killer applications

J. Alexander Liddle, Jacob Majikes

Proceedings Volume 11610, 1161015 (2021) https://doi.org/10.1117/12.2588353

KEYWORDS: Nanofabrication, Silicon, Semiconductor manufacturing, Polymers, Parallel computing, Nanolithography, Molecules, Molecular self-assembly, Manufacturing, Logic

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Proceedings Article | 24 March 2020 Presentation

Stochastic processes in self-assembly: limits and strategies for mitigation (Conference Presentation)

J. Alexander Liddle, Michael Zwolak, Jacob Majikes

Proceedings Volume 11324, 1132410 (2020) https://doi.org/10.1117/12.2552246

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Proceedings Article | 25 March 2019 Presentation

Nanoscale polymer property measurement using single-molecule fluorescence (Conference Presentation)

J. Alexander Liddle, Muzhou Wang, Stephen Stranick, Abhishek Kumar, Jeffrey Gilman

Proceedings Volume 10960, 109600H (2019) https://doi.org/10.1117/12.2515658

KEYWORDS: Polymers, Luminescence, Lithography, Optical lithography, Molecules, Life sciences, Image processing, Photoresist processing, Stochastic processes, Statistical modeling

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Polymeric resist materials are a critical part of the lithographic patterning process. Understanding their behavior, particularly at extreme dimensions becomes challenging: the presence of a rigid substrate or free surface, chemical interactions, and stochastic fluctuations can all play a role. Continuum models for polymer material behavior at small length scales not only become inaccurate, but also fail to capture the statistical variations that must be understood in order to determine what are the ultimate limits to producing defect-free structures. Experimental measurement of nanoscale heterogeneities in polymer properties is difficult. Many of the techniques that possess the required spatial resolution use energetic beams of electrons that rapidly damage soft materials, while x-ray or neutron scattering methods provide only ensemble average measurements. Individual fluorescent molecules, however, can yield a significant amount of information about their local environment. Measurements of the fluorescence lifetimes of suitably engineered fluorophores have long been used in the life sciences to probe local pH, and oxygen, or Ca2+ concentration. Lifetimes may also be sensitive to viscosity, giving information about local molecular configurations at nanosecond timescales. Measurements of fluorophore orientation, and rotational mobility, can indicate local molecular ordering and mobility, respectively. While the use of single-molecule fluorescence imaging methods in the life sciences has progressed rapidly, its use in materials science has been slower to develop, with only a handful of studies related to lithographic materials. One principal reason for this is that, in materials, fluorophore orientation is often fixed. Single-molecule images therefore have a complex, orientation-dependent structure, that, if not correctly accounted for, can lead to large errors in determining their position and orientation. Reducing the positional inaccuracies to the few-nanometer or better level, requires more sophisticated approaches to fitting single-molecule images and novel imaging hardware. With these approaches, both the location and orientation of individual fluorophores can be determined accurately. This information, when combined with single molecule lifetime measurements can, in principle, provide nanometer scale on the structure and dynamics of polymeric materials. I will discuss our progress in making accurate and precise measurements of fluorophore position and orientation in materials to enable high-resolution imaging, our development of a straightforward approach to determine how localization uncertainty and fluorophore labeling density together limit our ability to resolve nanoscale structures, how lithographic patterning enables us to partially overcome that limit, and how single-molecule orientation measurements can provide information on deformation in polymers at the 10 nm length scale. Finally, I will speculate on how measurement of single-molecule fluorescence lifetimes might provide information on local polymer heterogeneity at various stages of the image formation process in lithographic material systems.

Proceedings Article | 19 March 2015 Paper

Metrology of DSA process using TEM tomography

Tamar Segal-Peretz, Jonathan Winterstein, Jiaxing Ren, Mahua Biswas, J. Alexander Liddle, Jeffery Elam, Leonidas Ocola, Ralu N. Divan, Nestor Zaluzec, Paul Nealey

Proceedings Volume 9424, 94240U (2015) https://doi.org/10.1117/12.2085577

KEYWORDS: Tomography, Nanostructures, Transmission electron microscopy, Scanning transmission electron microscopy, Polymers, Polymethylmethacrylate, Etching, Metrology, Picosecond phenomena, Directed self assembly

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Proceedings Article | 7 March 2007 Paper

Nanoscale pattern transfer for templates, NEMS, and nano-optics

Deirdre Olynick, J. Alexander Liddle, Bruce Harteneck, Stefano Cabrini, Ivo Rangelow

Proceedings Volume 6462, 64620J (2007) https://doi.org/10.1117/12.705033

KEYWORDS: Etching, Silicon, Ions, Nanoimprint lithography, Chemistry, Nanoelectromechanical systems, Nano optics, Plasma etching, Multiplexing, Photomasks

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Proceedings Article | 29 March 2006 Paper

Pattern noise in e-beam exposed sub-35-nm contacts

Wojtek Poppe, Alexander Liddle, Erik Anderson, Andrew Neureuther

Proceedings Volume 6153, 61533Z (2006) https://doi.org/10.1117/12.657055

KEYWORDS: Semiconducting wafers, Scanning electron microscopy, Electrons, Detection and tracking algorithms, Printing, Edge detection, Image processing, Chemically amplified resists, Electron beam lithography, Algorithm development

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Proceedings Article | 23 January 2006 Paper

New nanofabrication technique using overlay for 15-nm zone plate

Weilun Chao, Bruce Harteneck, Erik Anderson, David Attwood, J. Alexander Liddle

Proceedings Volume 6110, 61100D (2006) https://doi.org/10.1117/12.647164

KEYWORDS: Zone plates, Fabrication, Overlay metrology, Spatial resolution, X-ray microscopy, X-rays, Electron beam lithography, Nanofabrication, X-ray imaging, Diffraction

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Proceedings Article | 14 September 2005 Paper

Nanometer-scale imaging with compact soft x-ray lasers

Fernando Brizuela, Georgiy Vaschenko, Courtney Brewer, Michael Grisham, Carmen Menoni, Hector Mancini, Mario Marconi, Jorge Rocca, Weilun Chao, J. Alexander Liddle, Erik Anderson, David Attwood, Alexander Vinogradov, Igor Artioukov, Yuriy Pershyn, Valeriy Kondratenko

Proceedings Volume 5919, 59190N (2005) https://doi.org/10.1117/12.614646

KEYWORDS: Zone plates, Image resolution, X-ray lasers, Imaging systems, Capillaries, Microscopes, X-rays, Spatial resolution, Objectives, Modulation

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Proceedings Article | 8 September 2005 Paper

Ultra-high-accuracy optical testing: creating diffraction-limited short-wavelength optical systems

Kenneth Goldberg, Patrick Naulleau, Senajith Rekawa, Paul Denham, J. Liddle, Eric Gullikson, Keith Jackson, Erik Anderson, John Taylor, Gary Sommargren, Henry Chapman, Donald Phillion, Michael Johnson, Anton Barty, Regina Soufli, Eberhard Spiller, Christopher Walton, Sasa Bajt

Proceedings Volume 5900, 59000G (2005) https://doi.org/10.1117/12.618066

KEYWORDS: Extreme ultraviolet, Optical testing, Interferometry, EUV optics, X-ray optics, X-rays, Lenses, Light sources, Astronomical imaging, X-ray astronomy

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Proceedings Article | 10 May 2005 Paper

Nano-imaging with compact extreme ultraviolet laser sources

G. Vaschenko, F. Brizuela, C. Brewer, M. Grisham, Y. Wang, M. Larotonda, B. Luther, C. Menoni, M. Marconi, J. Rocca, W. Chao, J. Liddle, E. Anderson, D. Attwood, A. Vinogradov, I. Artioukov, Y. Pershyn, V. Kondratenko

Proceedings Volume 5752, (2005) https://doi.org/10.1117/12.601899

KEYWORDS: Zone plates, Extreme ultraviolet, Imaging systems, Image resolution, Microscopes, Laser sources, Silicon, Spatial resolution, Objectives, Reflectivity

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Proceedings Article | 6 May 2005 Paper

EUV focus sensor: design and modeling

Kenneth Goldberg, Maureen Teyssier, J. Alexander Liddle

Proceedings Volume 5751, (2005) https://doi.org/10.1117/12.601522

KEYWORDS: Signal to noise ratio, Extreme ultraviolet, Nickel, Sensors, Photomasks, Image transmission, Optical design, Optimization (mathematics), Image sensors, Absorption

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Proceedings Article | 6 May 2005 Paper

A dual-mode actinic EUV mask inspection tool

Yanwei Liu, Anton Barty, Eric Gullikson, John Taylor, J. Liddle, Obert Wood

Proceedings Volume 5751, (2005) https://doi.org/10.1117/12.598559

KEYWORDS: Photomasks, Zone plates, Extreme ultraviolet, Inspection, Imaging systems, Multilayers, Defect inspection, EUV optics, Microscopes, Semiconducting wafers

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Proceedings Article | 31 March 2005 Paper

Plasmonic nanorainbow for label-free biomolecule sensing

Gang Liu, Erik Anderson, James Liddle, Luke Lee

Proceedings Volume 5703, (2005) https://doi.org/10.1117/12.592517

KEYWORDS: Gold, Plasmons, Microfluidics, Scattering, Luminescence, Sensors, Plasmonics, Multiplexing, Polymers, Nanowires

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Proceedings Article | 24 May 2004 Paper

CD metrology for the 45-nm and 32-nm nodes

Bryan Rice, Heidi Cao, Ovijut Chaudhuri, Michael Grumski, Bruce Harteneck, Alex Liddle, Deidre Olynick, Jeanette Roberts

Proceedings Volume 5375, (2004) https://doi.org/10.1117/12.536071

KEYWORDS: Critical dimension metrology, Scanning electron microscopy, Semiconducting wafers, Metrology, Scatterometry, Silicon, Atomic force microscopy, Semiconductors, Manufacturing, Ion beams

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Proceedings Article | 20 May 2004 Paper

EUV resist imaging below 50 nm using coherent spatial filtering techniques

Michael Shumway, Eric Snow, Kenneth Goldberg, Patrick Naulleau, Heidi Cao, Manish Chandhok, James Liddle, Erik Anderson, Jeffrey Bokor

Proceedings Volume 5374, (2004) https://doi.org/10.1117/12.535666

KEYWORDS: Semiconducting wafers, Extreme ultraviolet, Gold, Photomasks, Spatial filters, Line edge roughness, Printing, Wafer-level optics, Extreme ultraviolet lithography, Spatial frequencies

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Proceedings Article | 20 May 2004 Paper

EUV interferometric testing and alignment of the 0.3-NA MET optic

Kenneth Goldberg, Patrick Naulleau, Paul Denham, Senajith Rekawa, Keith Jackson, James Liddle, Erik Anderson

Proceedings Volume 5374, (2004) https://doi.org/10.1117/12.546199

KEYWORDS: Monochromatic aberrations, Extreme ultraviolet, Wavefronts, Interferometry, Optical alignment, Imaging systems, Interferometers, Mirrors, Photovoltaics, EUV optics

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Proceedings Article | 20 May 2004 Paper

Status of EUV micro-exposure capabilities at the ALS using the 0.3-NA MET optic

Patrick Naulleau, Kenneth Goldberg, Erik Anderson, Kevin Bradley, Rene Delano, Paul Denham, Bob Gunion, Bruce Harteneck, Brian Hoef, Hanjing Huang, Keith Jackson, Gideon Jones, Drew Kemp, James Liddle, Ron Oort, Al Rawlins, Senajith Rekawa, Farhad Salmassi, Ron Tackaberry, Carl Chung, Layton Hale, Don Phillion, Gary Sommargren, John Taylor

Proceedings Volume 5374, (2004) https://doi.org/10.1117/12.556538

KEYWORDS: Reticles, Semiconducting wafers, Sensors, Fiber optic illuminators, Printing, Extreme ultraviolet lithography, Metrology, Wafer-level optics, Scanners, Lithography

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Proceedings Article | 29 December 2003 Paper

Design and fabrication of advanced EUV diffractive elements

Patrick Naulleau, James Liddle, Farhad Salmassi, Erik Anderson, Eric Gullikson

Proceedings Volume 5347, (2003) https://doi.org/10.1117/12.537195

KEYWORDS: Diffusers, Extreme ultraviolet, Molybdenum, Modulation, Multilayers, Diffraction gratings, Reflectivity, Diffraction, Extreme ultraviolet lithography, Computer generated holography

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Proceedings Article | 16 June 2003 Paper

EUV interferometry of the 0.3-NA MET optic

Kenneth Goldberg, Patrick Naulleau, Paul Denham, Senajith Rekawa, Keith Jackson, Erik Anderson, J. Liddle, Jeffrey Bokor

Proceedings Volume 5037, (2003) https://doi.org/10.1117/12.484735

KEYWORDS: Extreme ultraviolet, Interferometry, Interferometers, EUV optics, Photomasks, Optical alignment, Optical testing, Wavefronts, Sensors, Diffraction

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Proceedings Article | 22 January 2001 Paper

SCALPEL mask parametric study

Gerald Dicks, Roxann Engelstad, Edward Lovell, James Liddle

Proceedings Volume 4186, (2001) https://doi.org/10.1117/12.410749

KEYWORDS: Metals, Photomasks, Kinematics, Charged-particle lithography, Lithography, Projection lithography, Device simulation, Scattering, Cobalt, Electron beam lithography

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Proceedings Article | 22 January 2001 Paper

Fabrication process and transmission characteristics of SCALPEL mask blanks with thin SiNx membranes

Sang-In Han, Pawitter Mangat, William Dauksher, Michael Chor, James Liddle, Anthony Novembre

Proceedings Volume 4186, (2001) https://doi.org/10.1117/12.410751

KEYWORDS: Photomasks, Etching, Charged-particle lithography, Silicon, Semiconducting wafers, Refraction, Silicon films, Scattering, Low pressure chemical vapor deposition, Chromium

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Proceedings Article | 21 July 2000 Paper

Thermomechanical modeling of the SCALPEL mask during exposure

Carl Martin, Roxann Engelstad, Edward Lovell, James Liddle

Proceedings Volume 3997, (2000) https://doi.org/10.1117/12.390094

KEYWORDS: Photomasks, Charged-particle lithography, Finite element methods, Lithography, Semiconducting wafers, Electron beams, Thermal modeling, Scattering, Silicon, Thermal analysis

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Proceedings Article | 15 November 1999 Paper

Modeling of laminar e-beam source for SCALPEL

Warren Waskiewicz, James Liddle, Victor Katsap

Proceedings Volume 3777, (1999) https://doi.org/10.1117/12.370140

KEYWORDS: Charged-particle lithography, Photomasks, Electron beam lithography, Charged particle optics, Lithographic illumination, Objectives, Lenses, Optical design, Tantalum, Electrodes

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Proceedings Article | 30 August 1999 Paper

SCALPEL mask blank fabrication

Thomas Saunders, Myrtle Blakey, Carlos Caminos, Gregory Bogart, Reginald Farrow, Chester Knurek, Avi Kornblit, James Liddle, Anthony Novembre, Milton Peabody

Proceedings Volume 3874, (1999) https://doi.org/10.1117/12.361228

KEYWORDS: Photomasks, Etching, Silicon, Charged-particle lithography, Semiconducting wafers, Electron beam lithography, Lithography, Scattering, Crystals, Dry etching

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