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| Projects High-Throughput Nanometrology with Scatterfield Microscopy Scanning Particle-Beam Microscope Innovations Atomic Force Microsope (AFM) Nanoparticle Metrology Nanoparticle Manipulation Metrology
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Precision Engineering Division Program
Next-Generation Nanometrology Program Solving Industry Needs of Tomorrow Program Manager: John Kramar Annual FTEs: 7 NIST Staff 10 Guest Researchers/Contractors 17 total FTEs Challenge: The next generation of nanotechnology industries will face dimensional measurement and characterization challenges that far exceed the capabilities of current measurement science. The manufacturing paradigm at this scale is rapidly being transformed by major advances in self-assembly, bio-manufacturing, and massively parallel atomically-precise manufacturing. These revolutionary manufacturing methods will require a complete rethinking of the methods and application of measurement science to manufacturing; incremental improvements of existing methods will be inadequate. Nanometer-scale objects and features in complex three-dimensional matrices must be measured with unprecedented precision and uncertainty, and with extremely high throughput. New dimensional measurement technologies and standards must be conceived and developed to meet the daunting measurement challenges of the next generation U.S. nanotechnology industry. Overview The Next-Generation Nanometrology (NextGen) Program is a forward-thinking program geared to advance the science of dimensional metrology and provide measurement technology in support of future emerging U.S. nanotechnology industries such as engineered nanocomposites, molecular electronics and spintronics, and nanoparticle-based pharmaceuticals. This essential research will make possible higher-resolution measurements of increasingly complex, nanoscale products, and enable the measurements of those products to be accomplished with high throughput in order to fully take advantage of the “economy of scale.” The program conceives and develops new metrology techniques, instruments and standards for this purpose. Advanced materials preparation methods are also a vital research and development challenge for the Program, because at the nanometer scale, the specimen properties of interest are easily altered by preparation methods as benign as adhesion to a surface. Thorough understanding and modeling of the specimen and metrology instrument interaction is also necessary since the sizes of the features of interest are often below the conventional instrument resolution limit, and the interaction physics dominates the signal. In addition the measuring instrument must be functioning optimally at all times. The key strategy for the NextGen Program is the discovery and pursuit of revolutionary and paradigm-shifting dimensional metrology methods, and techniques (e.g., scanned helium ion microscopy) for application to new and emerging nanoscale measurands. Cost of ownership and high throughput are also essential considerations for application in real manufacturing environments. The NextGen Program creates and supports critical measurement nanometrology solutions that are viable for meeting the challenges facing next-generation U.S. nanotechnology industries. The work defined within the Program addresses several of the identified U. S. Measurement System Measurement Needs (MN). The specific MNs and page numbers from Appendix B of the Report are found at the end of this document. Why NIST NIST is the right place to do this research because the infrastructural measurement science and technology problems that we are solving for the emerging nanotechnology industries are critical for the advancement of the entire nanomanufacturing technology sector, and are not specific to a single entity. It is NIST’s primary mission to address critically significant industry measurement challenges of this broad scope. NIST has world-leading expertise in nanoscale measurement science, and NIST has world-class measurement facilities in the Advanced Measurement Laboratory (AML). Program Objectives Objective 1: Invent methods to accurately measure nanoscale features and objects that will be extensible to extremely high throughput rates. High-throughput is necessary to effectively control the manufacture of products incorporating billions of nanoscale objects and features. Optical microscopy (OM) is a high-throughput metrology methodology that provides a unique advantage since it is a high-bandwidth measurement method that is inherently parallel. However, OM techniques have not traditionally been considered useful for nanometrology applications because their resolution is conventionally thought to be limited by the Rayleigh limit to one half the illumination wavelength, or at best roughly 200 nm for visible or near ultra-violet illumination. The NextGen Program will develop new optical nanometrology technologies such as Scatterfield microscopy, designed to break the traditional optical resolution barrier. These techniques are based on a more thorough examination of all the angle, polarization, and focus-height dependent optical interaction signals, and can extract quantitative information on features as small as one-twentieth the wavelength of light. The NextGen Program will also develop an advanced 193 nm illumination metrology microscope for further extending the resolution limits and enabling accurate metrology of next generation photomasks. Already in progress, Scatterfield microscopy will transfer the technology, methods and calibration samples to industry within the next three years. Scatterfield microscopy will have a major impact because it will make possible the cost-effective mass-production of nanotechnology products. Projects Next-Generation Nanometrology Program Project 1.1: High-Throughput Nanometrology with Scatterfield Microscopy Project Overview The NextGen Program is developing a new microscopy technique called Scatterfield microscopy (SM) that combines the best features of optical microscopy (OM) and scatterometry. Significant dimensional information with sensitivity to features one-twentieth the measurement wavelength can be extracted from the analysis of scattered light profiles through the use of structured illumination, specifically engineered targets, and physics-based image process modeling. These concepts will be applied to making measurements of linewidth, line spacing, line height, super-resolution overlay metrology, and defect metrology. Application of Scatterfield Microscopy will extend the resolution limits of current technology by at least a factor of ten. Deliverables and Intermediate Milestones
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Next-Generation Nanometrology Program Objective 2: Develop accurate methods for the characterization and three-dimensional metrology of nanoscale materials and features. A significant metrology challenge for next-generation manufacturing is the need to identify and measure true three-dimensional (3D) features embedded in complex matrices. The NextGen Program will develop advanced scanned particle beam metrologies to address this need either through high accelerating voltage penetration-imaging of relatively thin slices of the sample with a scanning electron microscope, or through ion-milling into the sample to expose the features of interest for subsequent examination with dual column electron/ion microscopes. In addition, the NextGen Program will advance the development of a scanning helium ion microscope (HeIM) for high resolution metrology, characterization and high-throughput nano-scale materials production. The HeIM is a new and revolutionary instrument with resolution and depth of field far exceeding current scanning electron microscopes, thus providing enhanced 3D surface characterization and metrology. Project 2.1: Scanning Particle-Beam Microscope Innovations Project Overview Scanning electron microscopy (SEM) is one of the workhorse techniques for imaging and characterization for nanotechnology. The NextGen Program will develop advanced methods to enhance this instrument’s capabilities such as: 1) advanced sample stages with high-speed, sub-nanometer-resolution laser interferometer measurements. Such an advanced stages will allow active monitoring and ultimately active compensation control of stage and instrument vibration (a major contributor to loss of resolution through image blurring); 2) super-nanotip electron emitters which will result in a smaller and brighter electron source that will increase resolution by a factor of three. 3) resolution standards and resolution measurement methods, which will place the characterization of this most critical of SEM performance metrics on a solid metrological basis and allow objective comparison between instruments and operating conditions; 4) dual beam (ion/electron) metrology system having a focused ion beam (FIB) for ion milling along with an SEM beam for concurrent imaging allowing the localized, in-situ, simultaneous cross-sectioning and imaging of features of interest for three-dimensional metrology. The NextGen Program will explore the metrological science of a revolutionary new advance in particle beam metrology: the development of a technique called scanning helium ion microscopy (HeIM). HeIM is analogous to the SEM but uses a probing beam of He+ ions instead of electrons. This results in potentially higher resolution and a greater surface sensitivity. The NextGen Program will work in collaboration with the manufacturer and SEMATECH and other NIST Laboratories to understand the science of He+ ion imaging and to optimize the instrument’s metrological capabilities. The NextGen Program will develop a rigorous understanding of the origin of the measured signal thus leading to accurate HeIM metrology. Deliverables and Intermediate Milestones
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Next-Generation Nanometrology Program Objective 3: Invent and provide methods for the accurate measurement of nanoparticles and materials characterization. Size counts in nanotechnology, and accurate particle sizing for the production and use of nanoparticles and nanocomposites is vital to U.S. industrial interests. Nanoparticle dimensional metrology is also a major concern in the environmental safety and health (ESH) field due to the early studies indicating negative health effects from certain carbon nanotubes and nanoparticles. The NextGen Program will develop techniques for immobilizing soft, bio-mimetic nanoparticles on surfaces without distorting or denaturing them, so that they can be imaged and measured with advanced fluid atomic force microscopy (AFM) for applications ranging from imaging contrast agents to therapeutic cancer treatments. In a similar vein, advanced optical trapping (OT) technology will be developed to extend the range of particle sizes that can be trapped down to the nanoscale, giving NIST a unique capability for accurate nanopositioning and nanoassembly. The NextGen Program will also develop accurate scanning electron microscope (SEM), AFM and scanning transmission electron microscope (STEM) metrology methodology for challenging nanomaterials such as carbon nanotubes, fuel cell membranes, and cellulose single nanocrystals. Project 3.1: Atomic Force Microsope (AFM) Nanoparticle Metrology Project Overview Nanoparticles and materials containing nanoparticles represent by far the largest fraction of the current nanotechnology product market. Yet the methods available for dimensional measurement and characterization of these products are inadequate for efficient development and cost effective production. The challenge is to find reliable, repeatable, and efficient methods for measuring nanoparticles and nanoparticle-based materials, and to provide the infrastructure needed for measurement traceability. Special challenges include the imaging of soft, deformable materials, and materials with limited sample homogeneity. For nanoparticle metrology, the NextGen Program will develop new measurement approaches that address the challenges of measuring soft as well as hard particles. For medical applications, for example, the Program will develop a systematic methodology for directly determining physical and biological information about nanoparticle delivery systems (NDS) from image data. Approaches will be developed using a unique, Program-developed fluid scanning probe microscopy (SPM) technique for high-resolution imaging of biological systems in solution. The Program will develop and transfer to industry specialized techniques for sample preparation, measurement of the stable feedback operation of an oscillating probe tip in solution, and quantitative force measurements of chemical, mechanical, electrical, hydrodynamic, and magnetic interactions of the molecular constituents of an NDS. Appropriate preparation and measurement techniques for physical characterization of nanobioparticles will be developed in parallel with in-vitro and in-vivo efficacy studies in order to facilitate and accelerate drug discovery and development. These studies will be done in collaboration with the Georgetown University Medical Center (GUMC). Deliverables and Intermediate Milestones
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Next-Generation Nanometrology Program Project 3.2: Nanoparticle Manipulation Metrology Project Overview The Nanoparticle Manipulation Metrology Project will develop an optical tweezers system for the trapping and manipulation of nanoparticles. This will make possible the accurate, controlled placement of nanoparticles at predefined locations on substrates. This will facilitate the development of accurate particle placement standards for the calibration of optical inspection tools. In addition, the simultaneous trapping of multiple particles in three dimensions and control of the orientation of non-symmetric nanoparticles will be demonstrated. This instrument will serve as a testbed for viable assembly methods for nanomanufacturing. Through the controlled placement of nanoparticles, NIST will fabricate an accurate, ordered-array, standard reference material (SRM) for nanoparticle detection and placement. Deliverables and Intermediate Milestones
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Next-Generation Nanometrology Program Objective 4: Develop intrinsic calibration standards based on the crystalline lattice. The ultimate limit for nanoscale length metrology is the development of intrinsic calibration standards, where the reference dimensions are based on atom spacing within an ordered, crystalline lattice. Using techniques developed within this Program, advanced step height, linewidth and pitch standards exhibiting picometer accuracy will be developed, using an ultra-high vacuum scanning tunneling microscope (UHV-STM). In addition, the NextGen Program will validate the use of atomic lattice spacing as a ruler through comparison with interferometric length measurements such as those performed in the Molecular Measuring Machine. The NextGen Program will leverage this knowledge to develop the metrology science needed to enable parallel, high-throughput, atomically-precise manufacturing for NIST standards development and for industrial applications. Project 4.1: Atom-Based Standards and Fabrication Project Overview The NextGen Program will develop a new, comprehensive approach to dimensional metrology using the atom spacings of a crystal as the fundamental “ruler” or scale. Based on this metric, larger scale features will be etched into substrates to serve as critical dimension or pitch references for instruments having less-than-atomic resolution. Crystal-lattice dimensional parameters will be validated through interferometer measurements. This work will primarily be done by employing two complex multi chamber vacuum STMs. The first system is a five chamber ultra high vacuum (UHV) facility regularly capable of producing 1 x 10-8 Pa base pressures, along with vibration isolation that yields a sub-100 pm noise floor. The other system has an field-ion/field-electron microscope (FIFEM), which is used to image scanned probe tips on the atomic scale and will be used to develop repeatable, robust methods for atomically sharp tip production. The Program will develop improved nanofabrication methods using the STM to write atomic-scale features on hydrogen-terminated silicon substrates using scanning probe oxidation (a technique that was invented in PED in the 1990’s) for accurate nano-standard development. Atom-based step height standards having picometer accuracy will also be developed, validated and characterized by an interferometer-instrumented atomic force microscope. Deliverables and Intermediate Milestones:
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