Proceedings Volume 8378

Scanning Microscopies 2012: Advanced Microscopy Technologies for Defense, Homeland Security, Forensic, Life, Environmental, and Industrial Sciences

Michael T. Postek, Dale E. Newbury, S. Frank Platek, et al.
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Proceedings Volume 8378

Scanning Microscopies 2012: Advanced Microscopy Technologies for Defense, Homeland Security, Forensic, Life, Environmental, and Industrial Sciences

Michael T. Postek, Dale E. Newbury, S. Frank Platek, et al.
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 5 June 2012
Contents: 10 Sessions, 19 Papers, 0 Presentations
Conference: SPIE Defense, Security, and Sensing 2012
Volume Number: 8378

Table of Contents

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Table of Contents

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  • Front Matter: Volume 8378
  • Scanning Microscopies for Micro and Nanotechnology Applications: Joint Session with 8373
  • Atomic Force Microscopy for Imaging and Metrology I
  • Atomic Force Microscopy for Imaging and Metrology II
  • Modeling
  • Particle Beam Microscopies I
  • Particle Beam Microscopies II
  • Special Session on Microscopy for STEM Educators I
  • Microscopies for Nanotechnological Applications
  • Special Session on Microscopy for STEM Educators I: addendum
Front Matter: Volume 8378
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Front Matter: Volume 8378
This PDF file contains the front matter associated with SPIE Proceedings Volume 8378, including the Title Page; Copyright information; Table of Contents; Introduction; Introduction to Special Session on Microscopy for Science, Technology, Engineering and Math (STEM) Educators, and the Conference Committee listing.
Scanning Microscopies for Micro and Nanotechnology Applications: Joint Session with 8373
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Past, present, and future of backscatter electron (BSE) imaging
Oliver C. Wells, Michael S. Gordon, Lynne M. Gignac
We describe developments in backscattered electron (BSE) imaging in the scanning electron microscope (SEM) beginning with the pioneering work of Von Ardenne and Knoll in Germany in the 1940's and Charles Oatley, Dennis McMullan, Kenneth Smith and others in the 1950's. Recent work on BSE imaging with very high energy (100's of KeV) electron beams, such as the inspection of voids in metallurgy under thick dielectrics in semiconductor back-end-of-the-line (BEOL) structures will be presented. Finally, we will look toward the future of BSE imaging in terms of the SEM's, detectors, and application areas.
Faults and foibles of quantitative scanning electron microscopy/energy dispersive x-ray spectrometry (SEM/EDS)
Dale E. Newbury, Nicholas W. M. Ritchie
Scanning electron microscopy with energy dispersive x-ray spectrometry (SEM/EDS) is a powerful and flexible elemental analysis method that can identify and quantify elements with atomic numbers > 4 (Be) present as major constituents (where the concentration C > 0.1 mass fraction, or 10 weight percent), minor (0.01≤ C ≤ 0.1) and trace (C < 0.01, with a minimum detectable limit of ≈± 0.0005 - 0.001 under routine measurement conditions, a level which is analyte and matrix dependent ). SEM/EDS can select specimen volumes with linear dimensions from ≈ 500 nm to 5 μm depending on composition (masses ranging from ≈ 10 pg to 100 pg) and can provide compositional maps that depict lateral elemental distributions. Despite the maturity of SEM/EDS, which has a history of more than 40 years, and the sophistication of modern analytical software, the method is vulnerable to serious shortcomings that can lead to incorrect elemental identifications and quantification errors that significantly exceed reasonable expectations. This paper will describe shortcomings in peak identification procedures, limitations on the accuracy of quantitative analysis due to specimen topography or failures in physical models for matrix corrections, and quantitative artifacts encountered in xray elemental mapping. Effective solutions to these problems are based on understanding the causes and then establishing appropriate measurement science protocols. NIST DTSA II and Lispix are open source analytical software available free at www.nist.gov that can aid the analyst in overcoming significant limitations to SEM/EDS.
Does your SEM really tell the truth?
Michael T. Postek, András E. Vladár
The scanning electron microscope (SEM) has gone through a tremendous evolution to become a critical tool for many, diverse scientifi c and industrial applications. The high resolution of the SEM is especially useful for qualitative and quantitative applications for both nanotechnology and nanomanufacturing. It is likely that one of the fi rst questions asked when the fi rst scanning electron micrograph was ever taken was: "...how big is that?" The quality of that answer has improved a great deal over the past few years, especially since SEMs are being used as a primary tool on semiconductor processing lines to monitor the manufacturing processes. The needs of semiconductor production prompted a rapid evolution of the instrument and its capabilities. Over the past 20 years or so, instrument manufacturers, through this substantial semiconductor industry investment of research and development (R&D) money, have vastly improved the performance of these instruments. All users have benefi tted from this investment, especially where metrology with an SEM is concerned. But, how good are these data? This presentation will discuss a sub-set of the most important aspects and larger issues associated with imaging and metrology with the SEM. Every user should know, and understand these issues before any critical quantitative work is attempted.
Atomic Force Microscopy for Imaging and Metrology I
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Progress on CD-AFM tip width calibration standards
Ronald Dixson, Boon Ping Ng, Craig D. McGray, et al.
The National Institute of Standards and Technology (NIST) is developing a new generation of standards for calibration of CD-AFM tip width. These standards, known as single crystal critical dimension reference materials (SCCDRM) have features with near-vertical sidewalls. This is accomplished using preferential etching on (110) silicon-on-insulator (SOI) substrates. As such, these structures are particularly useful for CD-AFM tip width calibration. As part of a previous generation of SCCDRMs that was released to the Member Companies of SEMATECH, we were able to deliver structures with linewidths ranging from as low as 50 nm up to 240 nm. These typically had expanded uncertainties (k = 2) of between 1.5 nm and 2 nm. Subsequently, these chips were used as a traceable source of tip width calibration for CD-AFM by SEMATECH and several Member Companies. We are now working on a new generation of SCCDRMs with the goal of reducing linewidth expanded uncertainties, and we are using our new CD-AFM to support this development. The features are patterned using electron beam lithography with equipment available in the new nanofabrication facility within the Center for Nanoscale Science and Technology (CNST) at NIST. Intact features as small as 10 nm have been observed with line width roughness (LWR) sufficiently low to support 1 nm expanded uncertainties. We believe it will be possible to fabricate features as small as 5 nm, and we are now working to refine the fabrication process and to assess the limits of our approach.
Atomic force microscope cantilevers as encoder for real-time displacement measurements
Xiaomei Chen, Helmut Wolff, Ludger Koenders
We have investigated the use of atomic force microscope (AFM) cantilevers as encoder for real-time high-resolution displacement measurements. Mathematical derivations show that two AFM cantilevers signals are needed for real-time forward and backward displacement measurements in any planar direction and in x- or y-axis direction respectively when two are paired with a 1D sinusoidal grating. Tuning-fork (TF) cantilevers are the best choice among AFM cantilevers for the setup of a multi-cantilever encoder head. During the study an AFM head with up to three TF cantilevers as the encoder has been designed and built. The system was experimentally tested for its performance and feasibility of realtime displacement measurements in x- or y- axis by using two cantilevers. To achieve a correct reading the distance between two cantilever tips is preset in such a way that the two 1D sinusoidal grating position-encoded signals have a quadrature phase shift form. The decoding algorithm is based on directly unwrapping of the phase from the signals in real-time. Cross-correlation filtering and differentiation process of two encoded signals could be applied to suppress the noise and to reduce the offset and tilt of the encoded signals and by this allows a successful implementation of real-time displacement measurements.
Atomic Force Microscopy for Imaging and Metrology II
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Hybrid metrology for critical dimension based on scanning methods for IC manufacturing
Introduction of new material stacks, more sophisticated design rules and complex 3D architectures in semiconductor technology has led to major metrology challenges by posing stringent measurement precision and accuracy requirements for various critical dimensions (CD), feature shape and profile. Current CD metrology techniques being used in R&D and production such as CD-SEM, Scatterometry, CD-AFM, TEM have their inherent limitations that must be overcome to fulfil advanced roadmap requirements. The approach of hybrid automated CD metrology seems necessary. Using multiple tools in unison is an adequate solution when adding their respective strengths to overcome individual limitations. Such solution should give the industry a better metrology solution than the conventional approach. In this work, we will present and discuss a new methodology of CD metrology so-called hybrid CD metrology that mixes CD data coming from different techniques. In parallel to this hybrid metrology approach, we must address individual technique enhancement. Subsequently, scanning techniques enhancement will be presented (CD-SEM and CD-AFM) through contour metrology parameter which should become a pedestal feature for 1x node production. Finally, we will discuss the potential directions of a hybrid metrology engine as a generic tool compatible with any kind of CD metrology techniques.
Deformation of polystyrene nanoparticles under different AFM tapping loads
Bo-Ching He, Wei-En Fu, Huay-Chung Liou, et al.
Deformation induced by contact force from the tip is the major measurement uncertainty using atomic force microscope (AFM) for the apex height of nanoparticles. Additionally, the contact force by the AFM tip is difficult and not reliable in traditional tapping and contact modes. In this work, the contact forces applied by the AFM were varied using a peak-force tapping method, which is unique technique to perform force-controlled scanning, to characterize the deformation of nanoparticles. The obtained measurement results were compared with a theoretical model developed for predicting the deformation between PS nanoparticles and tip/substrate. It was found that the deformation occurred at low force as 0.5 nN for polystyrene nanoparticles on mica substrate. The deformation was fully plastic. In addition, the deformation has a linear relationship with contact force, which is consistent with contact mechanics model.
Extension of gravity center method for diameter calibration of polystyrene standard particles with a metrological AFM
Ichiko Misumi, Keiji Takahata, Kentaro Sugawara, et al.
In the particle diameter calibration using metrological AFM, the distance between center points of neighboring two particles is referred to as "lateral diameter" when a single-layer close-packed structure of particles is successfully formed. The distance between an apex of a particle and a substrate is referred to as "vertical diameter." In the previous studies, lateral diameter was calculated by manually selecting and extracting a line profile from metrological AFM data and directly applying a method to calculate a pitch of one-dimensional grating. As the manual line profile extraction depends on who does it, however, there is a possibility that calculated lateral diameter is varied from person to person. We developed a technology to calibrate diameter of polystyrene latex (PSL) particles by using our metrological AFM. In this study, the gravity center method is extended to three dimensions to calculate position of and the center of gravity in each particle. Lateral diameter, which was defined as distance between gravity centers of neighboring two particles, is calibrated and uncertainty in the lateral diameter calibration is evaluated. Deformation of particles was also estimated by using Young's modulus of thin film PSL and bulk PSL.
Modeling
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Image processing with Maple for simplified analysis in scanning microscopy
Alejandro Mesa
The images provided by a scanning microscopes show diffraction patterns product of the scanning mechanism. Those are complicated to analyze without computational help, I tried to find a simple way to make it easier, applying an automatic method. I have used some of the tools included in the image processing toolbox of Maple to analyze patterns which are commonly found in the images provided by the scanning microscopes, to make interpretation easier for the ones that want to analyze the image. I consider that, for how simple and opened it is, the method I developed may be useful for the people interested in the applications and further research related to analyzing scanning microscope images.
Particle Beam Microscopies I
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Nanomanipulation system for scanning electron microscope
P. Woo, I. Mekuz, B. Chen
Traditionally scanning electron microscopy (SEM) is often used as a scientific instrument for providing high magnification images and analytical capability for microstructural analysis. In recent years different applications for SEM has been developed and is gaining popularity in doing characterizations of fine-scale materials such as in-situ annealing, cryo-microscopy, micro-tensile testing, electrical resistivity measurements and grain boundary/texture analysis (EBSD). With the increasing demand in these sub-micron to nano-scale characterizations, there's an increasing need to have a more sophisticated stage within the microscope. In other word, a stage that would have "hands" built onto the SEM stage to allow operator to manipulate objects and execute different tasks under high magnification. In this paper we presented a compact nanomanipulation system that is designed to be retrofitted easily onto many SEMs. Capabilities and potential applications of using such manipulation system will be discussed.
Multi-signal FIB/SEM tomography
Focused ion beam (FIB) milling coupled with scanning electron microscopy (SEM) on the same platform enables 3D microstructural analysis of structures using FIB for serial sectioning and SEM for imaging. Since FIB milling is a destructive technique, the acquisition of multiple signals from each slice is desirable. The feasibility of collecting both an inlens backscattered electron (BSE) signal and an inlens secondary electron (SE) simultaneously from a single scan of the electron beam from each FIB slice is demonstrated. The simultaneous acquisition of two different SE signals from two different detectors (inlens vs. Everhart-Thornley (ET) detector) is also possible. Obtaining multiple signals from each FIB slice with one scan increases the acquisition throughput. In addition, optimization of microstructural and morphological information from the target is achieved using multi-signals. Examples of multi-signal FIB/SEM tomography from a dental implant will be provided where both material contrast from the bone/ceramic coating/Ti substrate phases and porosity in the ceramic coating will be characterized.
Advances in high-speed low-latency communications for nanopositioning in advanced microscopy
Scott C. Jordan
We present a comparison of classical and recently developed communications interfacing technologies relevant to scanned imaging. We adopt an applications perspective, with a focus on interfacing techniques as enablers for enhanced resolution, speed, stability, information density or similar benefits. A wealth of such applications have emerged, ranging from nanoscale-stabilized force microscopy yielding 100X resolution improvement thanks to leveraging the latest in interfacing capabilities, to novel approaches in analog interfacing which improve data density and DAC resolution by several orders of magnitude. Our intent is to provide tools to understand, select and implement advanced interfacing to take applications to the next level. We have entered an era in which new interfacing techniques are enablers, in their own right, for novel imaging techniques. For example, clever leveraging of new interfacing technologies has yielded nanoscale stabilization and atomic-force microscopy (AFM) resolution enhancement. To assist in choosing and implementing interfacing strategies that maximize performance and enable new capabilities, we review available interfaces such as USB2, GPIB and Ethernet against the specific needs of positioning for the scanned-imaging community. We spotlight recent developments such as LabVIEW FPGA, which allows non-specialists to quickly devise custom logic and interfaces of unprecedentedly high performance and parallelism. Notable applications are reviewed, including a clever amalgamation of AFM and optical tweezers and a picometer-scaleaccuracy interferometer devised for ultrafine positioning validation. We note the Serial Peripheral Interface (SPI), emerging as a high-speed/low-latency instrumentation interface. The utility of instrument-specific parallel (PIO) and TTL sync/trigger (DIO) interfaces is also discussed. Requirements of tracking and autofocus are reviewed against the time-critical needs of typical applications (to avoid, for example, photobleaching), as exemplified in recent capabilities for fast acquisition of focus with bumpless transition between optical and electronic position control. A novel planarization approach is reviewed, providing a nanoscale-accurate datum plane over mesoscale scan areas without scanline flattening. Finally, not to be overlooked is the original real-time interface: analog I/O, with novel capabilities introduced in recent months. Here additional developments are discussed, including a resolution-enhancing technique for analog voltage generation and a useful combination of high-speed block-mode and single-point data acquisitions.
Particle Beam Microscopies II
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Improving the performance of the critical dimension-scanning electron microscope with the contrast transfer function
Aron J. Cepler, Bradley L Thiel
Critical dimension scanning electron microscopes (CD-SEMs) are used extensively by the semiconductor industry to perform highly accurate dimensional metrology of patterned features. To ensure optimal feedback for process control, these tools must produce highly reproducible measurements. This means monitoring and minimizing not only day-to-day variations on a given tool, but also tool-to-tool variations whether within the same production facility or at different sites. It has been shown that the contrast transfer function (CTF) can be used to evaluate the imaging performance of SEMs by giving a quantitative measure of the fidelity with which specimen contrast information (i.e., point-to-point variations in emitted signal intensity) is represented in the image data as a function of spatial frequency. Because all imaging defects and artifacts as well as the point spread function impact the shape of the CTF, it is an ideal means with which to monitor deviations from a baseline performance. By using a thoughtfully designed and thoroughly characterized test specimen, the CTF of a given tool can be decoupled from the specimen information, allowing for characterization of the imaging system itself. Fresnel zone plates and pseudorandom arrays of dots are good candidates for such test structures, if they can be fabricated with sufficient resolution to assess the performance of the tool up to its information limit. The feasibility of this approach has been assessed with test structures fabricated using nano-imprint lithography with 22 nm design rules. The advantages of using the CTF of a specific instrument to improve CD-SEM image simulations are also demonstrated.
Special Session on Microscopy for STEM Educators I
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Forensic practice in the field of protection of cultural heritage
Marek Kotrlý, Ivana Turková
Microscopic methods play a key role in issues covering analyses of objects of art that are used on the one hand as screening ones, on the other hand they can lead to obtaining data relevant for completion of expertise. Analyses of artworks, gemmological objects and other highly valuable commodities usually do not rank among routine ones, but every analysis is specific, be it e.g. material investigation of artworks, historical textile materials and other antiques (coins, etc.), identification of fragments (from transporters, storage places, etc.), period statues, sculptures compared to originals, analyses of gems and jewellery, etc. A number of analytical techniques may be employed: optical microscopy in transmitted and reflected light, polarization and fluorescence in visible, UV and IR radiation; image analysis, quantitative microspectrophotometry; SEM/EDS/WDS; FTIR and Raman spectroscopy; XRF and microXRF, including mobile one; XRD and microXRD; x-ray backlight or LA-ICP-MS, SIMS, PIXE; further methods of organic analysis are also utilised - GS-MS, MALDI-TOF, etc.
Integrating research and advanced microscopy into the high school curriculum
Craig Queenan, Alyssa Calabro, David Becker
The Bergen County Academies (BCA) is a public magnet high school in New Jersey focused on science, technology, engineering and mathematics (STEM) education. The research program offered at the school offers students the opportunity to conduct, present and defend their own scientific research using advanced tools and techniques, including scientific equipment unavailable in most high schools, such as scanning and transmission electron microscopes. Through their journey into research, students are given a skill set that can be transferred to future education and their careers, and will help shape the next generation of leaders in the fields of science, technology, engineering and math. By serving as an educational model for reformed STEM education, BCA is at the forefront of what STEM education in the United States will look like in the years ahead.
Microscopies for Nanotechnological Applications
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Robust probes for high resolution chemical detection and imaging
Rebecca L. Agapov, Alexei P. Sokolov, Mark D. Foster
There are needs for both high resolution imaging and high sensitivity detection/analysis of surface chemistry on a nanometer scale. These needs can be addressed with Raman spectroscopy coupled with schemes that provide extraordinary enhancement of the Raman signal, namely surface enhanced (SERS) and tip enhanced Raman spectroscopy (TERS). Advances in applications of high resolution imaging and high sensitivity detection will be enabled by two specific improvements: increased signal enhancement and increased robustness of the plasmonic structures needed to achieve enhancement. Robustness and stability are especially important for those plasmonic structures made of silver that usually provide the best enhancements. Here we focus particularly on TERS, in which a plasmonic structure is placed on a scanning probe microscope tip in order to achieve high lateral resolution imaging. We have demonstrated that aluminum oxide protected silver plasmonic structures show significantly increased robustness against chemical and mechanical degradation when compared to unprotected analogues without loss of enhancement. A 2-3 nm thick coating of aluminum oxide prevents chemical attack of the underlying silver film for three months in a desiccator, significantly increasing the storage life of current probes. The same protective coating also extends the scanning life of the probe when the probe is used to image a hard patterned silicon substrate.
Response of electrospun CNT composites to irradiation
S. M. Rosa, J. P. Crespo, J. J. Santiago-Avilés, et al.
In this work, we investigate the suitability of Electrospinning as a manufacturing technique to produce CNT-polymer composites with a response to light. This objective is explored by way of developing a precursor solution comprised of a polymeric blend, suitable of CNT dispersion and further electrospinning. The MWCNTs were dispersed using Sodium dodecyl sulfate (SDS) and added to a polymeric solution consisting of Polydimethylsiloxane (PDMS) and Polymethyl methacrylate (PMMA) in Tetrahydrofuran (THF) and Dimethylformamide (DMF). The dispersion of the CNTs during synthesis was studied using UV-VIs and XRD techniques. Fibers electrospun out of this precursor and their response to irradiation will also be discussed. Fiber morphology was characterized by SEM and the response to irradiation was examined by photoelectric conductivity.
Special Session on Microscopy for STEM Educators I: addendum
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Introduction to special session on microscopy for Science, Technology, Engineering and Math (STEM) educators
Michael T. Postek, Mary Satterfield, Bradley Damazo, et al.
The future of our nation hinges on our ability to prepare our next generation to be innovators in science, technology, engineering and math (STEM). Excitement for STEM must begin at the earliest stages of our education process. Yet, today far too few of our students are prepared for the challenges ahead. Several initiatives are trying to change this situation. “Microscopy for STEM Educators” was an initiative that demonstrated the value of incorporating microscopy into STEM education. Several notable invited speakers discussed their successful programs implementing microscopy in STEM education in order to foster student interest and excitement. A hands-on session with table-top scanning electron microscopes was held at the end of the presentations and the attendees were encouraged to bring samples of interest and operate the instruments. This paper outlines some of the accomplishments and goals of this session.