Metrology Tool Research Articles

Repeatability and Reproducibility of Microdosimetry With a Mini-TEPC

Experimental microdosimetry measures the energy deposited in a microscopic sensitive volume (SV) by single ionizing particles traversing the SV or passing by. The fundamental advantage of experimental microdosimetry over the computational approach is that the first allows to determine distributions of energy deposition when information on the energy and nature of the charged particles at the point of interest is incomplete or fragmentary. This is almost always the case in radiation protection applications, but discrepancies between the modelled and the actual scenarios should be considered also in radiation therapy. Models for physical reality are always imperfect and rely both on basic input data and on assumptions and simplifications that are necessarily implemented. Furthermore, unintended events due to human errors or machine/system failures can be minimized but cannot be completely avoided.Though in proton radiation therapy (PRT) a constant relative biological effectiveness (RBE) of 1.1 is assumed, there is evidence of an increasing RBE towards the end of the proton penetration depth. Treatment Planning Systems (TPS) that take into account a variable linear energy transfer (LET) or RBE are already available and could be implemented in PRT in the near future. However, while the calculated dose distributions produced by the TPS are routinely verified with ionization chambers as part of the quality assurance program of every radiotherapy center, there is no commercial detector currently available to perform routine verification of the radiation quality, calculated by the TPS through LET or RBE distributions. Verification of calculated LET is required to make sure that a complex robustly optimized plan will be delivered as planned. The scientific community is coming to conclusion that a new domain of Quality Assurance additionally to the physical dose verification is required, and microdosimetry can be the right approach to address that. A first important prerequisite is the repeatability and reproducibility of microdosimetric measurements. This work aims at studying experimentally the repeatability and reproducibility of microdosimetric measurements performed with a miniaturized Tissue Equivalent Proportional Counter (mini-TEPC) in a 62 MeV proton beam. Experiments were carried out within 1 year and without propane gas recharging and by different operators. RBE was also calculated by applying the Loncol’s weighting function r(y) to microdosimetric distributions. Demonstration of reproducibility of measured microdosimetric quantities y¯F, y¯D and RBE10 in 62 MeV proton beam makes this TEPC a possible metrological tool for LET verification in proton therapy. Future characterization will be performed in higher energy proton beams.

Quantification and reduction of Poisson-Gaussian mixed noise induced errors in ellipsometry.

Ellipsometry is an important metrology tool in a plethora of industries. The measurement accuracy can be significantly affected by the existence of Poisson-Gaussian mixed noise. This paper quantifies the induced error on normalized Mueller matrix measurements through statistical analysis. A method is then proposed to mitigate the effects of Poisson-Gaussian noise in spectroscopic ellipsometry signal demodulation, based on maximum likelihood estimation. The noise is characterized through experiments on an in-house setup. The improved performance of dimension reconstruction from the proposed method is demonstrated through simulations.

Interference-based weak-value amplification effects in post-selected weak measurement

Weak measurement (WM) based on post-selection is a useful tool for precision metrology due to the ability of amplifying weak physical effects. In this paper, we reveal the underlying mechanism of the amplification in the post-selected WM based on the weak-value amplification (WVA) and the almost balanced weak-values amplification (ABWVA) strategies. We find that the amplification stems from the interference between the local oscillator and signal components which are respectively associated with the initial system state and the state disturbance induced by the weak coupling. The magnitude of the amplification is proportional to the interference strength which is dominated by the post-selection and the coupling strength. Furthermore, our theory can perfectly explain the amplification limit in the WVA strategy and the anomalous amplification in the ABWVA strategy.

Calibrated Phasor Measurement Unit as a Reliable Metrological Tool for National Power Grid Operation in India

At the national power grid in India, stability is one of the most important factors due to disturbances caused by distributed load and time-variant sources. Presently, for monitoring the transmission efficiency and performance of power grids, phasor measurement units (PMUs) are being installed at various locations in the country. Time synchronization, using Coordinated Universal Time (UTC), makes PMU an important and reliable data acquisition equipment across the grids. To ensure reliability and accuracy of the acquired data, PMUs must be calibrated. However, recent development of automated PMU calibrator system by NIST and M/s Fluke, USA has revolutionized the calibration process by enhancing the accuracy and consistency of PMU measurements. The CSIR-NPL PMU system is fully operational to calibrate PMUs according to the IEEE synchrophasor standards. The time consumed to perform the PMU calibration is comparatively much less than the conventional method. A traceable PMU calibrator system has great potential in calibrating PMUs used to monitor, control and protect the power grid.

X-ray computed tomography evaluations of additive manufactured multimaterial composites.

Additive Manufacturing (AM) often produces complex engineered structures by precisely distributing materials in a layer-by-layer fashion. Multimaterial AM is a particularly flexible technique able to combine a range of hard and soft materials to produce designed composites. Critically, the design of AM multimaterial structures requires the development of precise three-dimensional (3D) computed aided design (CAD) files. While such digital design is heavily used, techniques able to validate the physically manufactured composite against the digital design from which it is generated are lacking for AM, especially as any evaluations must be able to distinguish material variation across the 3D space. Nowadays, there is a growing interest in volumetric tools that can provide topological information hidden by the surface of shaped materials. So far, technologies such as Optical microscopy (OM), Scanning Electron Microscopy (SEM), and Coordinate Measuring Machine (CMM) have paved the way into the metrology field to measure the external geometry of physical objects. Currently, alongside conventional metrology tools, X-ray computed tomography (XCT) is emerging to measure the subsurface of the objects but maintaining the integrity of the probed samples. Thereby, the volumetric nature of the XCT investigations and its associated imaging techniques, ensure 3D quantitative measurements comparable to the output data from 2D metrology tools, but above all, supply the missing subsurface description for an exhaustive metrology study. The reward associated with XCT applied to multimaterial AM is a map reflecting the fabricated distribution of materials following CAD, with the benefits of better understanding the mechanical interplay within phases, hence, describing the hidden processes as well as the changes in phases due to a range of mechanical or chemical phenomena. In this study, a nondestructive approach using X-ray computed tomography (XCT) is used to fully evaluate the 3D distribution of multimaterials from an AM process. Specifically, two diverse hard and soft materials are alternatively produced in the form of a fibre embedded in a matrix via ink-jet printing. XCT coupled with imaging evaluation were able to distinguish between the differing materials and, importantly, to demonstrate a reduction in the expected fabricated volumes when compared to the respective CAD designs. LAY DESCRIPTION: Additive Manufacturing (AM) has recently become important in producing complex engineered structures. Using 3D CAD files and/or reconstructed data sets from imaging, hard and soft materials are manufactured independently or in combination, according to geometrical features and shapes in the input data. However, the evaluation of the resultant manufactured parts in comparison with the original 3D drawing is currently lacking. In this sense, X-ray computed tomography (XCT) provides an important metrology tool for mono and multimaterial AM. In this work a volumetric metrology investigation is proposed using higher resolution XCT to provide 3D information comparable to that of the 3D CAD drawings. A commercial high-resolution multijetting material printer (ProJet 5500X, 3D Systems, USA) is used to manufacture single fibre composites, through a complementary deposition of photo sensible polymers. Hard and soft plastics are produced using a UV curable step, resulting in materials of similar attenuation under an X-ray probe. A critical aim of the evaluations is the potential for XCT to distinguish between different UV curable 3D printing materials.

Deeply sub-wavelength non-contact optical metrology of sub-wavelength objects

Microscopes and various forms of interferometers have been used for decades in optical metrology of objects that are typically larger than the wavelength of light λ. Metrology of sub-wavelength objects, however, was deemed impossible due to the diffraction limit. We report the measurement of the physical size of sub-wavelength objects with deeply sub-wavelength accuracy by analyzing the diffraction pattern of coherent light scattered by the objects with deep learning enabled analysis. With a 633 nm laser, we show that the width of sub-wavelength slits in an opaque screen can be measured with an accuracy of ∼λ/130 for a single-shot measurement or ∼λ/260 (i.e., 2.4 nm) when combining measurements of diffraction patterns at different distances from the object, thus challenging the accuracy of scanning electron microscopy and ion beam lithography. In numerical experiments, we show that the technique could reach an accuracy beyond λ/1000. It is suitable for high-rate non-contact measurements of nanometric sizes of randomly positioned objects in smart manufacturing applications with integrated metrology and processing tools.

Development and certification of reference standards for phenolic content in biologicals, based on comparison of results obtained by GLC, HPLC, spectrophotometric, and colorimetric methods

Phenol is used as a preservative in a number of biological products. Methods that are used for quantitative determination of phenol differ a lot. Current requirements for accredited laboratories include continuous internal quality control. Reference standards with a certified content of the analyte are an effective metrological tool for ensuring such control. The aim of the study was to develop and certify reference standards for phenolic content in biological products, based on comparison of results obtained by GLC, HPLC, spectrophotometric, and colorimetric methods. Materials and methods: diluent for allergens by (candidate reference standard), 2.5 and 5 mg/mL phenol solutions, and 2.5 mg/mL 2-phenoxyethanol solution were used in the study. The experiments were performed using spectrophotometric, colorimetric, HPLC, and GLC procedures. The statistical analysis of results included calculation of the arithmetic mean, standard deviation, coefficient of variation, and analysis of variance with Student’s t-test and Fisher’s F-test. Results: the results of phenolic content determination by the spectrophotometric, colorimetric, and HPLC methods were statistically comparable. The F value obtained for equal sample sizes (n = 40) was F = 0.9343, given the critical value Fcrit = 3.96. A reference standard certified by one of these methods can be used to control the consistency of phenol determination by a relevant method. The results of phenolic content determination by the GLC method showed statistically significantly differences: F = 17.47, given Fcrit = 3.96, which demonstrated the need for certification of another reference standard. Conclusions: two reference standards were certified in the study: reference standard 42-28-449 with the certified phenolic content of 2.56‒3.32 mg/mL, to be used with the spectrophotometric, colorimetric, and HPLC methods; and reference standard 42-28-451 with the certified phenolic content of 2.92‒3.28 mg/mL, to be used with the GLC method.

SEMI Standards for Consumables for Chemical Mechanical Planarization (CMP)

IC manufacturing is a sophisticated multistep process where parameters need to be monitored and controlled very tightly. Chemical-mechanical polishing (CMP) is an important step in IC manufacturing that is required to achieve global and local planarity for subsequent lithography processes. CMP has been one of the fastest-growing segments of the semiconductor industry for the past 20 years.The CMP process is highly critical for achieving sustainable yields in IC manufacturing. This area is also one of the most difficult to control. Quality issues in the CMP process are extremely expensive and can have a significant impact to device yields and reliability. It is known that CMP consumables, such as CMP pads, CMP slurries, and CMP conditioning disks are critical to achieve the target performance in IC manufacturing processes. As such, reducing the variations in CMP consumables properties through standardized metrology tools and processes has become a high priority for advanced IC manufacturing nodes.In this presentation we will focus on measuring and reporting critical parameters for such critical and widely used consumables in the CMP industry, as CMP pads ([Ref. 1-4]), retainer rings, and conditioning disks.Get InvolvedSEMI Standards development activities take place throughout the year in all major manufacturing regions. To get involved, join the SEMI International Standards Program at: www.semi.org/standardsmembership.For more information please visit our main Web site and current events page. If you have any questions regarding SEMI Standards activities, please contact your local SEMI Standards staff.Standards WatchSEMIwww.semi.org<12/03/2020>

Polarization-Dependent All-Dielectric Metasurface for Single-Shot Quantitative Phase Imaging.

Phase retrieval is a noninterferometric quantitative phase imaging technique that has become an essential tool in optical metrology and label-free microscopy. Phase retrieval techniques require multiple intensity measurements traditionally recorded by camera or sample translation, which limits their applicability mostly to static objects. In this work, we propose the use of a single polarization-dependent all-dielectric metasurface to facilitate the simultaneous recording of two images, which are utilized in phase calculation based on the transport-of-intensity equation. The metasurface acts as a multifunctional device that splits two orthogonal polarization components and adds a propagation phase shift onto one of them. As a proof-of-principle, we demonstrate the technique in the wavefront sensing of technical samples using a standard imaging setup. Our metasurface-based approach fosters a fast and compact configuration that can be integrated into commercial imaging systems.

Methods of coordinating fuzzy expert evaluations in the design of metrological support means

The article explores methods of coordinating expert judgments in the design of technical measuring instruments. A methodology for analyzing fuzzy matrices of pairwise comparisons of the effectiveness of preliminary designs of metrological support means is proposed. It includes defuzzification of pairwise comparison matrices; finding a median pairwise comparison matrix; determining fuzzy mean values for each element, and forming fuzzy weights for the compared means by individual levels of the membership function values. The procedure for finding the final membership function of metrological support tools is formalized to minimize the deviations of the fuzzy paired comparison matrices of expert opinions from the final matrix of these comparisons. Methods for optimizing the final ranking of alternative projects based on fuzzy group evaluations were investigated and developed. A fuzzy modification of the Condorcet principle is developed for the case of fuzzy dominance of alternatives. These methods of expert evaluations serve the purpose of increasing the efficiency of development and creation of metrological support means.

Polarization modeling and predictions for Daniel K. Inouye Solar Telescope, part 7: preliminary NCSP system calibration and model fitting

Daniel K. Inouye Solar Telescope (DKIST) is designed to deliver accurate spectropolarimetric solar data across a wide wavelength range, covering a large field of view simultaneously using multiple facility instruments for solar disk, limb, and coronal observations. We show successful design and implementation of National Solar Observatory Coudé Laboratory Spectropolarimeter, a custom metrology tool for efficient continuous broadband polarization calibration of the telescope mirrors through a coudé laboratory focus. We compare multiple fitting techniques for the 10 to >140 variable DKIST system polarization models. We compare results with the first DKIST solar calibration observations and find small thermally forced retardance changes of ±0.2 deg and ±0.5 deg for two separate SiO2 retarders. Modulation matrices derived are stable to < ± 0.01 per element during the first on-Sun calibration tests. We achieve good fit agreement to our metrology-based model over a 390- to 1600-nm bandpass. The solutions are robust and efficient using only 10 input Stokes vectors from elliptical calibration retarders. We developed a custom polarizer assembly used with metrology tools to orient the DKIST polarization coordinates to better than 0.1-deg clocking angle.

Tolerance estimation and metrology for reverse engineering based remanufacturing systems

ABSTRACT Tolerances are critical to the product’s design, manufacturing, and quality. However, tolerances are often overlooked in a reverse engineering (RE) process for industrial applications, especially in legacy parts or spare parts remanufacturing. Ignoring tolerances could either unnecessarily call for high precision remanufacturing processes or make the reproduced parts unqualified. Additive manufacturing (AM) techniques are used in remanufacturing applications because of their ability to manufacturing intricated parts. Due to its layer-by-layer fabrication nature, the metrology for AM-created parts is drastically different when compared to traditional feature-generation processes. In this study, we first propose a novel way to classify manufacturing processes based on whether they directly identify or generate features, which could profoundly affect their metrology tools. Next, a systematic geometric inspection and tolerance estimation methodology for the RE system is proposed. A set of tools is developed to extract various geometric dimensional values from the point clouds based on their tolerancing types. Moreover, based on the domain knowledge in production process design and planning, methods are developed to estimate empirical tolerances from a small batch of legacy parts. Comparisons of empirical tolerances of real machined parts to their designed tolerances are presented to evaluate the performance of the proposed framework.

Measurement of the optical constants of monolayer MoS2 via the photonic spin Hall effect

How to explore the physical effect and characterize physical parameters in atomic scale crystals is still a challenging issue in modern optics. We detect the photonic spin Hall effect in monolayer MoS2 to study the atomic light-matter interaction. Due to the sensitive dependence of the spin-Hall shifts on the optical constants of MoS2, we propose this fundamental effect as a metrological tool for the parameter characterization. Combined with the weak-value technique, the experimental results show that the complex refractive index can be extracted by treating the atomically thin MoS2 as a homogeneous slab with an effective thickness. However, modeling the thin crystal as a surface current can determine the optical conductivity with a high measurement resolution. We believe this fast and precise measurement of optical parameters can provide a reliable approach to investigate optical properties for transition metal dichalcogenides.

Use of smartphones as optical metrology tools for surface wear detection

Proper wear level information and early wear detection are crucial goals in many engineering applications and industrial components in order to improve efficiency and reduce production, maintenance, or replacements costs. Furthermore, this should ideally be achieved with a user-friendly, low-cost, and easy to implement methodology for wear level monitoring and detection. In this work, we present the design of a new approach to accomplish early wear detection that is implemented by means of a stand-alone smartphone device and application providing real-time online metrology. The online monitoring is done by means of optical measurements and image processing based on the advanced smartphone vision system technology currently available in commercial devices. The developed mobile App works in continuous mode without interrupting the wear process. Specifically, it traces surface changes and monitors the progression of wear enabling just-in-time warning alarms for “significant wear” and “critical wear” detection. We demonstrate that critical wear of a surface prior to fatal rupture can be detected, which is the main objective in many industrial applications.

Direct generation of relativistic isolated attosecond pulses in transmission from laser-driven plasmas.

Isolated attosecond pulses are useful to perform pump-probe experiments at a high temporal resolution, and provide a new tool for ultrafast metrology. However, it is still a challenging task to generate such pulses of high intensity, even for a few-cycle laser. Through particle-in-cell simulations, we show that it is possible to directly generate a giant isolated attosecond pulse in the transmission direction from relativistic laser-driven plasmas. Compared to attosecond pulse generation in the reflection direction, no further spectral filtering is needed. The underlying radiation mechanism is coherent synchrotron emission, and the transmitted isolated attosecond pulse can reach relativistic intensity. This provides a promising alternative to generate intense isolated attosecond pulses for ultrafast studies.

A methodology to obtain traceability for internal and external measurements of Inconel 718 components by means of XRCT

There is undoubtedly an increasing trend towards the use of XRCT as a dimensional metrology tool, driven mainly by the proliferation of complex and hollow parts in the industry. While this technology is suitable for qualitative analysis, a consistent methodology is nevertheless needed, so that XRCT could be considered an accurate and reliable technology for carrying out dimensional and geometrical quantitative analysis.Therefore, the main aim of this approach is to develop a methodology for a traceable measurement of external and internal features.To do it, each measurement is associated with its corresponding task-specific uncertainty estimation by an adapted substitution approach, and thus providing a novel traceable XRCT measurement methodology. The proposed methodology is based on using a reference object related to the workpiece to measure external and internal features of an Inconel 718 component by means of XRCT. In both cases, traceability is guaranteed by the use of conventional dimensional metrology instruments. Results show that wall thicknesses can be accurately measured with errors below 2% for all the cases studied (wall thicknesses from 0.957 to 2.648 mm). As internal measurements are more prone to suffer artifacts, inner diameter deviations from nominal values are from 0.3% in the best XRCT conditions to 19.5% in the worst conditions.With the aim of providing a better scientific understanding of the measurement by means of XRCT, further tests were carried out. CT parameters influence on the beam hardening effect and on the surface definition was studied. Results show that the traceability is assured when the proposed methodology is used.

Creation of a New European Metrology Network on Pollution Monitoring (POLMO)

Driven by a wide set of European regulations, strategies and action plans, to cope with and to minimize environmental pollution in Europe, the need for pollution monitoring especially on chemicals and radionuclides is constantly growing in importance as it supports the ambition of the European Union: “In 2050, we live well within the planet’s ecological limits”. This can be reached only on the basis of high-quality data on pollution monitoring as well as strong metrological cooperation between all relevant European partners and stakeholders. To foster this goal a strong, collaborative, multi-disciplinary, long-term and self-sustaining “European Metrology Network on pollution monitoring”, as a metrological reference infrastructure, needs to be generated and managed. Such a metrological network will be developed over the next years within the framework of an EMPIR network project called POLMO. POLMO will focus first on chemicals and radionuclides pollution in the different compartments of the environment (water, air, soil) but also will strive to expand its expertise to other areas such as light or noise pollution on longer terms. The detailed objectives of the POLMO network are: To become an international point of focus and create stronger connections for all the different stakeholder communities (active networks and associations, research centres, testing laboratories, manufacturers, industry, standardization bodies, regulators) with NMIs/DIs. This should allow new approaches to meet stakeholder requirements by developing multidisciplinary metrological research overpassing current regulatory principles. To maximize efficiency of NMIs/DIs activity and minimise resources (human, infrastructures, financial) as well as knowledge, data and best-practice transfers between NMIs/DIs and with the main EU organisations as well as stakeholders in the POLMO context. Demonstrate the role of metrology in the European research area. Moreover, to define the place and role of the metrology in the pollution monitoring chain of measurements and to demonstrate its added value and benefit. To maximize and accelerate dissemination of reliable metrology practices for pollution monitoring through mutually recognized and agreed approaches The goal of this poster is to describe how the POLMO Metrology Network will be implemented from mid 2022 in particular by the means of an EMPIR JNP (Joint Network Programme) in the framework of EURAMET (European Association of National Metrology Institutes). The project could support the need for harmonization and reliability of e-DNA measurements, as necessary to support their recognition, by organizing the development of missing metrological tools at European level

Standardization and control of thread parameters of a roller-screw gear

Among the mechanisms that transform rotational motion into translational motion, helical gears of rolling, which provide higher efficiency and speed, are currently dominant. These include ball-screw gears and roller-screw gears. A comparative analysis of these showed that the latter has a number of limitations compared to the former. Serial production requires the development of automated technologies for machining, assembly and testing, the use of high-precision metrological equipment to control functional surfaces with minimal time costs in digital automated systems. Modern measuring instruments, such as contour meters allow for element-by-element control of the parameters of threaded surfaces. In the manufacture of high-tech products such as an electromechanical drive, the use of element-wise control is the only way to ensure product quality. However, not enough standardization of the parameters of the thread of the roller-screw gears requires the development of a set of requirements that provide the specified operational characteristics of the product. The work is devoted to the standardization of the parameters of the special roller-screw gears thread used in the electromechanical drive manufactured by AO Diakont. This article discusses issues related to the standardization of the accuracy parameters of the profiles of high-precision roller-screw gears, metrological support tools, a set of techniques and software based on a systematic approach to inputting, outputting and transmitting information about measurement results and evaluating their validity. The application of the proposed control methodology allowed improving the quality of products and reducing its cost.

34.4: Applications of Electron Beam Review System for AMOLED Patterning Process Control

As the development of display technologies, much smaller critical dimension design is an inevitable trend and much tighter statistical process control is needed and necessary. Electron Beam Review System can provide much more precise critical dimension measurement without glass to be broken compared with traditional optical metrology tools. Besides, taper CD or taper angle is a critical parameter for display product quality control and Electron Beam Review System is the only tool in display Fabs that can provide such information.

Synchrotron X-ray metrology of dopant distribution and oxidation state in high pressure CVD grown TM2+:ZnSe optical fibers

High pressure chemical vapor deposition (HPCVD) has shown to be a promising method for producing Cr2+:ZnSe and Fe2+:ZnSe mid-IR optical fiber lasers. The oxidation state of the dopants and their spatial homogeneity are critical for the characterization of effective fiber laser performance; however, this is challenging for small fiber cores and small doping concentrations. We demonstrate using synchrotron micro X-ray fluorescence (XRF) mapping to study the distribution of the dopants throughout the fiber cross-sections. Furthermore, we study the local chemical environment of these unique fiber structures using micro X-ray near edge absorption spectroscopy (XANES). Our study reveals that transition metal doped ZnSe deposited using HPCVD has nanoscale dopant aggregation although the material is chemically identical to the commercially produced diffusion doped laser crystals, as indicated by the presence +2 oxidation state of the dopants. This work demonstrates the power of synchrotron-based X-ray techniques for use as metrology tools for improving the performance of laser materials in fiber geometry.