Accurate and traceable calibration of two-dimensional gratings
TL;DR: In this paper, the calibration of 1D and 2D gratings is performed using a metrological large range scanning probe microscope with optimized measurement strategies, and two different kinds of data evaluation methods, a gravity center method and a Fourier transform method, are developed and investigated.
Abstract: Accurate and traceable calibration of lateral standards (1D and 2D gratings) is a basic metrological task for nano- and microtechnology. Both the mean pitch and the uniformity of the gratings should be measured quantitatively. Although optical diffractometers are effective for measuring the mean pitch, they are not able to measure the uniformity of gratings. In this study, the calibration of gratings is performed using a metrological large range scanning probe microscope with optimized measurement strategies. Two different kinds of data evaluation methods, a gravity centre method and a Fourier transform method, have been developed and investigated. Cosine error, a significant error source of the measurement, is analysed and corrected. Calibrations on several 1D gratings have been carried out. The calibrated mean pitch values have an excellent agreement with those measured by optical diffractometry. Nevertheless, irregularities of the gratings were only deduced from the SPM results. Finally, the usage of the 1D/2D gratings for the calibration of a typical SPM is illustrated.
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TL;DR: In this paper, the state of the art in scanning force microscopy for dimensional metrology is described and a detailed description is given of the important factors affecting the major components of a scanning force microscope from the metrological point of view.
143 citations
TL;DR: The Molecular Measuring Machine (MME) as discussed by the authors is an SPM and Michelson interferometer-based metrology instrument for point-to-point measurements over a 50 mm by 50 mm working area.
Abstract: Nanometre accuracy and resolution metrology over technically relevant areas is becoming a necessity for the progress of nanomanufacturing. At the National Institute of Standards and Technology, we are developing the Molecular Measuring Machine, a scanned probe microscope (SPM) and Michelson interferometer based metrology instrument, designed to achieve nanometre measurement uncertainty for point-to-point measurements over a 50 mm by 50 mm working area. The salient design features are described, along with example measurements that demonstrate the measurement capabilities so far achieved. Both long-range measurements of sub-micrometre pitch gratings over 10 mm, and short-range, high-resolution measurements of a molecular crystal lattice have been accomplished. The estimated relative measurement uncertainty so far attained for pitch measurements is 6 × 10−5, coverage factor k = 2. We have also used this instrument and scanning probe oxidation lithography for creating some simple nanometre dimension patterns that could serve as prototype calibration standards, utilizing the SPM probe tip positioning accuracy.
100 citations
TL;DR: In this paper, the authors present a brief overview of how this has been achieved, highlights the future requirements for metrology to support developments in AFM technology and describes work in progress to meet this need.
Abstract: Scanning probe microscopes, in particular the atomic force microscope (AFM), have developed into sophisticated instruments that, throughout the world, are no longer used just for imaging, but for quantitative measurements. A role of the national measurement institutes has been to provide traceable metrology for these instruments. This paper presents a brief overview as to how this has been achieved, highlights the future requirements for metrology to support developments in AFM technology and describes work in progress to meet this need.
88 citations
TL;DR: An approach to establishing rigorous nano-and microdimensional metrology using scanning probe microscopes (SPMs) and metrological profilometers is presented in this article, where an overview on calibrations of nanostructures such as step height, one-and two-dimensional gratings, feature width, nanoroughness and geometry of a nanohardness indenter is given.
Abstract: An approach to establishing rigorous nano- and microdimensional metrology using scanning probe microscopes (SPMs) and metrological profilometers is presented. An overview on calibrations of nanostructures—such as step height, one- and two-dimensional gratings, feature width, nanoroughness and geometry of a nanohardness indenter—and microstructures—such as microgroove, microroughness and geometry of a macrohardness indenter—is given in this paper.
77 citations
Cites background from "Accurate and traceable calibration ..."
...Measurement strategies for both 1D and 2D gratings have been proposed [21]....
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TL;DR: The main SPM instruments for realizing the International System of Units (SI) are the Molecular Measuring Machine, the calibrated atomic force microscope and the critical dimension atomic force microscopy as discussed by the authors.
Abstract: Scanning probe microscope (SPM) dimensional metrology efforts at the US National Institute of Standards and Technology (NIST) are reviewed in this paper. The main SPM instruments for realizing the International System of Units (SI) are the Molecular Measuring Machine, the calibrated atomic force microscope and the critical dimension atomic force microscope. These are optimized for long-distance measurements, three-dimensional measurements over conventional SPM distances and critical dimension or linewidth measurements, respectively. 10 mm distances have been measured with the relative standard uncertainty, uc, of 1.5 × 10−5; step heights at the 100 nm scale have been measured with the relative uc of 2.5 × 10−3 and sub-micrometer linewidths have been measured with uc = 0.8 nm.
63 citations
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TL;DR: In this paper, the authors describe a metrological large range scanning probe microscope (LR-SPM) with an Abbe error free design and direct interferometric position measurement capability, aimed at traceable topographic measurements that require nanometer accuracy.
Abstract: We describe a metrological large range scanning probe microscope (LR-SPM) with an Abbe error free design and direct interferometric position measurement capability, aimed at versatile traceable topographic measurements that require nanometer accuracy. A dual-stage positioning system was designed to achieve both a large measurement range and a high measurement speed. This dual-stage system consists of a commercially available stage, referred to as nanomeasuring machine (NMM), with a motion range of 25 mm×25 mm×5 mm along x, y, and z axes, and a compact z-axis piezoelectric positioning stage (compact z stage) with an extension range of 2 μm. The metrological LR-SPM described here senses the surface using a stationary fixed scanning force microscope (SFM) head working in contact mode. During operation, lateral scanning of the sample is performed solely by the NMM. Whereas the z motion, controlled by the SFM signal, is carried out by a combination of the NMM and the compact z stage. In this case the compact z...
154 citations
TL;DR: In this article, a long-range atomic force microscope (AFM) profiler system was built based on a commercial metrology AFM and a home-made linear sample displacement stage, consisting of monolithic flexures forming a double parallelogram.
Abstract: A long-range atomic force microscope (AFM) profiler system was built based on a commercial metrology AFM and a home-made linear sample displacement stage. The AFM head includes a parallelogram-type scanner with capacitive position sensors for all three axes. A reference cube located close to the tip acts as the counter electrode for the capacitive sensors. Below this metrology AFM head we placed a linear sample displacement stage, consisting of monolithic flexures forming a double parallelogram. This piezo actuated stage provides a highly linear motion over m. Its displacement is simultaneously measured by a capacitive position sensor and a differential double-pass plane mirror interferometer; both measuring systems have subnanometre resolution capability. For the measurement of periodical structures two operating modes are possible: a direct scanning mode, in which the position of the displacement stage is increased point by point while the AFM head measures the height, and a combined scanning mode where the displacement stage produces offsets which are multiples of the pitch to be measured while the AFM head is simultaneously scanning to locate an edge or a line centre position. Construction details, system characteristics and results from first pitch measurements are presented. The estimated relative combined uncertainties for pitch values on different standards are in the range to . Laser diffraction measurements of comparable uncertainty were performed on the same standards and show a very good agreement.
145 citations
TL;DR: In this paper, the precision measurements of 240 nm-pitch one-dimensional grating standards were carried out using an atomic force microscope (AFM) with a high-resolution three-axis laser interferometer (nanometrological AFM).
Abstract: Precision measurements of 240 nm-pitch one-dimensional grating standards were carried out using an atomic force microscope (AFM) with a high-resolution three-axis laser interferometer (nanometrological AFM). Laser sources of the three-axis laser interferometer in the nanometrological AFM were calibrated with an I2-stabilized He–Ne laser at a wavelength of 633 nm. The results of the precision measurements using the nanometrological AFM have direct traceability to the length standard. The uncertainty in the pitch measurements was estimated in accordance with the Guide to the Expression of Uncertainty in Measurement. The primary source of uncertainty in the measurements was derived from interferometer nonlinearity, and its value was approximately 0.115 nm. Expanded uncertainty (k = 2) of less than 0.31 nm was obtained. It is suggested that the nanometrological AFM is a useful instrument for the nanometrological standard calibration.
116 citations
TL;DR: An atomic force microscope with a high-resolution three-axis laser interferometer for real-time correction of distorted topographic images has been constructed and investigated in this paper, where standard samples for a scanning probe microscope can be directly calibrated on the basis of stabilized wavelength of He-Ne lasers.
Abstract: An atomic force microscope with a high-resolution three-axis laser interferometer for real-time correction of distorted topographic images has been constructed and investigated. With this apparatus, standard samples for a scanning probe microscope can be directly calibrated on the basis of stabilized wavelength of He–Ne lasers. The scanner includes a three-sided mirror block as a mobile target mirror for the interferometer, which realizes a rectangular coordinate system. The position coordinates of the sample is independently and simultaneously acquired with high-resolution (0.04 nm) X/Y/Z interferometer units and fed back for XY servo scanning and height image construction. The probe is placed on the sample surface at the intersection of the three optical axes of the interferometer with good reproducibility, so that the Abbe error caused by the rotation of the scanner is minimized. Image distortion in the XY plane and vertical overshoot/undershoot due to nonlinear motion of piezo devices, hysteresis, and creep are eliminated. The optical properties of the interferometers, mechanical characteristics of the scanner, and system performances in dimensional measurements for calibration standards are demonstrated.
115 citations
TL;DR: The Molecular Measuring Machine (MME) as discussed by the authors is an SPM and Michelson interferometer-based metrology instrument for point-to-point measurements over a 50 mm by 50 mm working area.
Abstract: Nanometre accuracy and resolution metrology over technically relevant areas is becoming a necessity for the progress of nanomanufacturing. At the National Institute of Standards and Technology, we are developing the Molecular Measuring Machine, a scanned probe microscope (SPM) and Michelson interferometer based metrology instrument, designed to achieve nanometre measurement uncertainty for point-to-point measurements over a 50 mm by 50 mm working area. The salient design features are described, along with example measurements that demonstrate the measurement capabilities so far achieved. Both long-range measurements of sub-micrometre pitch gratings over 10 mm, and short-range, high-resolution measurements of a molecular crystal lattice have been accomplished. The estimated relative measurement uncertainty so far attained for pitch measurements is 6 × 10−5, coverage factor k = 2. We have also used this instrument and scanning probe oxidation lithography for creating some simple nanometre dimension patterns that could serve as prototype calibration standards, utilizing the SPM probe tip positioning accuracy.
100 citations