General Problems of Metrology and Measurement Technique Metrological Aspects of Harmonic Self-Organization

HARMST 2009 was held from June 25 to 28, 2009, in Saskatoon, Saskatchewan, Canada. This workshop continued a biennial tradition that began in 1995 in Karlsruhe, Germany, and travels around Europe, America, and Asia, successively held in Madison, WI, USA (1997), Chiba, Kisarazu, Japan (1999), Baden-Baden, Germany (2001), Monterey, CA, USA (2003), Gyeongju, Korea (2005), and Besancon, France (2007). This series has established itself as a premier, independent international event devoted to the advancement of high aspect ratio micro fabrication technologies and their applications. HARMST 2009 again brought together experts from academia and industry from various disciplines and regions who shared their latest results of investigations and developments. The technical program included sessions on a broad range of aspects of design, modeling, fabrication, metrology, testing, and applications in high aspect ratio microand nanotechnology. Particular focus was cast on X-ray and UV-lithography in thick resist layers, using various resist systems and including nonconventional processes, and subsequent electroforming and replication steps, as well as related simulation, modeling, and metrology techniques. Furthermore, selected advancements in DRIE, mechanical micromachining, and electro discharge micromachining relevant to high aspect ratio technologies were presented, as well as highlights of the integration of nanometer-scale structures, advanced materials, and functionalized surfaces. Applications were another focus of the workshop, from sensors and actuators to RF MEMS, MOEMS, fluidic microsystems, and bio-MEMS. The workshop also included a focus session on challenges and opportunities in micromechanics and microfluidics to discuss a cross section of aspects at the example of a few applications, including industrial needs, fabrication technology capabilities and restrictions, metrology, and testing. HARMST 2009 featured 74 poster and 39 oral presentations from 15 countries as well as 8 short course contributions. The HARMST workshops have been highly successful and continue their tradition not only in terms of presentation and discussion during the workshop, but also with respect to the timely dissemination of cutting edge technologies via the Journal of Microsystem Technologies. This Special Issue of Microsystem Technologies is collecting 53 finally accepted contributions as reviewed and unabridged versions of papers presented at the workshop, following the traditional cooperation between Springer and the HARMST Technical Advisory Committee. We hope that you will enjoy reading the HARMST contributions as much as we did.

In occupational exposure to vibration, the risk assessment process is defined through a regulatory framework that presents some relevant metrological problems. This framework considers methods based on estimation and on measurements. Estimation methods could employ existing information that is provided for each manufacturer to each individual tool or application to carry out such estimation. The use of estimation methods has some problems, such as substantial uncertainty. When using measurement methods, some metrological aspects are not fully defined. Therefore, a new and emerging risk appears due to certain methodologic limitations. Consequently, the variation between the estimated and the actual values could overestimate the level of occupational exposure to vibrations. Thus, with this paper, a critical analysis of this emerging metrological problem is provided. For this, a critical analysis of the metrological requirements regarding European standards is developed. To this end, the estimation method and measure method are investigated, considering, in both cases, the main factors related to uncertainty, reliability, and traceability. With this structure, a set of metrological limitations have been identified, thus pointing towards future lines of research that allow the improvement of the process of assessing the level of occupational exposure to vibrations.

Intensity modulated radiation therapy (IMRT) poses a number of challenges for properly measuring commissioning data and quality assurance (QA) radiation dose distributions. This report provides a comprehensive overview of how dosimeters, phantoms, and dose distribution analysis techniques should be used to support the commissioning and quality assurance requirements of an IMRT program. The proper applications of each dosimeter are described along with the limitations of each system. Point detectors, arrays, film, and electronic portal imagers are discussed with respect to their proper use, along with potential applications of 3D dosimetry. Regardless of the IMRT technique utilized, some situations require the use of multiple detectors for the acquisition of accurate commissioning data. The overall goal of this task group report is to provide a document that aids the physicist in the proper selection and use of the dosimetry tools available for IMRT QA and to provide a resource for physicists that describes dosimetry measurement techniques for purposes of IMRT commissioning and measurement-based characterization or verification of IMRT treatment plans. This report is not intended to provide a comprehensive review of commissioning and QA procedures for IMRT. Instead, this report focuses on the aspects of metrology, particularly the practical aspects of measurements that are unique to IMRT. The metrology of IMRT concerns the application of measurement instruments and their suitability, calibration, and quality control of measurements. Each of the dosimetry measurement tools has limitations that need to be considered when incorporating them into a commissioning process or a comprehensive QA program. For example, routine quality assurance procedures require the use of robust field dosimetry systems. These often exhibit limitations with respect to spatial resolution or energy response and need to themselves be commissioned against more established dosimeters. A chain of dosimeters, from secondary standards to field instruments, is established to assure the quantitative nature of the tests. This report is intended to describe the characteristics of the components of these systems; dosimeters, phantoms, and dose evaluation algorithms. This work is the report of AAPM Task Group 120.

Metrology is the art and science of measurement. Precise and reliable measurement methods leading to trustable measurement results with known measurement uncertainty are a prerequisite for meaningful scientific results, comparability and interoperability in a multitude of disciplines in physics and technology. Implementing traceability to the International System of Units (Systeme international d’unites – SI) by establishing an unbroken chain of calibrations to the representation of fundamental or derived units at the National Metrology Institutes (NMIs) is the basis for this. With the advent of new measurement techniques in THz science and technology, metrology aspects become more important in this emerging field as commercial THz systems are appearing on the market. E.g., the compliance with safety limits cannot be proven and interoperability of system components cannot be guaranteed without reliable measurement results including the measurement uncertainty. NMIs but also many other scientific groups work on open questions in the field of THz metrology such as detector calibration, characterization of ultrafast devices, traceability for scattering parameters in vector network analysis and measurement uncertainty in THz spectroscopy. In this special issue on THz Metrology seven invited articles cover the most recent developments in the field. The articles are meant to give a review of the respective topic combined with the most recent results from the authors.

The modern trend of most advanced countries is the active development and implementation of Industry 4.0 technologies, Internet of things and “smart cities”. Despite the “autonomy” of these technologies, they still remain dependent on the achievements of metrology. The article deals with the concept of cyber-physical systems, presents an analysis of the problems of their metrological support, and shows the main metrological problems in the development of these technologies.

The work of the BIPM consultative committee for measurement standards of ionizing radiation section II: Radionuclide measurements

Erratum to: Aggregation of Preferences as a Method of Solving Problems in Metrology and Measurement Technique

The Chapter is devoted to consideration of metrological aspects of intrinsically interconnected characteristics of light fields, such as intensity, polarization and coherence. Conceptually, all these quantities are derived from the Wolf’s coherency matrix [1]. However, new insight on interconnection of them is provided by the novel singular-optical approach [2, 3] predicting existence of important regularities in electromagnetic fields which were early considered as quite random ones. So, phase singularities of scalar (homogeneously polarized), polarization singularities of vector (inhomogeneously polarized) fields, as well as singularities of correlation functions of partially coherent, partially polarized fields constitute specific skeletons, i.e. “bearing” elements of a field. Knowing the loci and characteristics of such elements, one can judge on behavior of a field at its other areas, at least in qualitative manner, but quite reliably [4]. This circumstance opens quite new possibilities for metrology of optical fields and leads to prospective practical applications of new metrological techniques.

Critical dimension control is a key quality factor for better semiconductor device performance and yield and it is even more critical in 5 nm technology node beyond Si and SiGe device, where very high-mobility channel or new devices based on III-V and Ge, like directed self-assembled vertical nanowires, and tunnel FETs. Several in-line metrology techniques such as CD-SEM and scatterometry (or OCD) show a strong value in CD, LER, LWR, pitch and height monitoring in terms of throughput. The optical metrology technique especially OCD is sensitive to the refractive index, n and extinction coefficient, k of film on the structure. Thus it is hard to develop robust OCD library for III-V compound nanostructure due to change of n and k values as composition variation. Thus, it requires an unique in-line metrology technique that is less sensitive to material properties for robust process monitoring and yield control. In addition, as the drive current in a FinFET device flows along the vertical sidewalls, the surface quality of the sidewall strongly influences carrier mobility and device lifetime, leakage current so on and rough sidewall makes them worse. Sidewall roughness characterization, thus, become a critical issue and it needs to be controlled and monitored during process. However, in-line metrology technique could not been introduced for monitoring the quality of sidewall roughness yet. In this study, in-line 3 dimension atomic force microscopy (3D-AFM) was investigated to measure critical dimension parameters as complementary solution to the current in-line metrology tool sets and to develop fab compatible and high throughput in-line sidewall roughness monitoring solution. 3D-AFM (or CD-AFM) is used to consider as a reference tool for CD calibration in the ITRS roadmap because of high accuracy and atomic resolution without sample damage during measurement, but it is very slow. Therefore, we focus on not only measurement technique itself for compound nanostructure, but also how to implement the technique into the operation from process control perspective. Si, SiGe and InGaAs/InP fins with various pitch were used and their CD, height and sidewall roughness were measured by in-line 3D-AFM (NX-3DM, Park Systems). The system consists of XY and Z scanners independently, which allows the Z scanner head to tilt by 0, 19˚ and 38˚ depending on pattern dimension. Measurement In order to measure fin with the pitch of 45 nm, e-beam deposited amorphous carbon fiber with the diameter of 10 nm and the height of 150 nm (M-CNT-150, Nanotools) was used. In order to evaluate fab operation capabilities such as mapping capabilities, probe to probe reliability and long term reliability of tool, recipes with 27 die map were developed. In order to verify the measurement accuracy TEM verification was performed. Critical dimension of Si, SiGe and InGaAs/InP fins were successfully measured and especially CD and height of Si and SiGe fin with 45 nm pitch were measured successfully with CNT probe and all measured parameters were verified by TEM and it showed all good agreement. It means that CD and height information with material insensitive could be done by in-line 3D-AFM. Long term reliability was also evaluated and it showed that its 3σ value was 0.6 nm and peak to valley of the value was less than 1 nm. We think that non-contact measurement technique allows to reach this good repeatability. In-line 3D-AFM could successfully measure and differentiate between sidewall roughness of Si and InGaAs/InP nanostructures, which were treated at different process. Tilt angle influence was evaluated and different tilt angle did not influence roughness value and its resolution. Roughness value at different space was measured and it shows similar sidewall roughness. Probe to probe repeatability was checked and it shows good long term reliability and repeatability of the in-line 3D AFM system. In-line 3D AFM successfully measured critical dimension and sidewall roughness of Si, SiGe and InGaAs/InP nanostructure in atomic scale with good reliability. AFM with tilt head allows AFM probe to access pattern sidewall. As a result in-line 3D AFM could be used as a process monitoring for next generation device fabrication process such as III-V FinFET and GAA FET. In-line 3D-AFM could be used as complementary solution to other in-line metrology tools. Hybridization of in-line 3D-AFM with CD-SEM and OCD could make metrology system more accurate and learning cycle and recipe development faster.

Critical dimension atomic force microscope (CD-AFM or 3D-AFM) is an important metrology technique for full three-dimensional measurements of linewidth CD and sidewall shape. Recent improvements in the 3D-AFM platform design, including high-precision/low-drift sample stages and high resolution optics, have been coupled with 'enhanced CD' (eCD) scan mode and novel AFM tip design. Especially, the eCD mode features a fast scanning actuator system (FA) and a bottom corner transitional rescan algorithm (TRS). The actuation system utilizes high gain feedback electronics and high bandwidth piezoelectric actuator to pull away a slender tip much faster from a small trench sidewall. The transitional rescan algorithm detects a rising sidewall before rescanning the transition for better bottom corner profiling. The paper presents evaluation data to show these enhancements resulted in improved measurement capability for small trenches required for shrinking device size, better sidewall profiling, more accurate bottom CD and LWR/LER measurement, faster scan speed, and less tip wear [1]. All the improvements ensure 3D-AFM continues to have the lowest measurement uncertainty among all other dimension metrology techniques.

Extreme ultraviolet lithography (EUVL) is the leading candidate for next generation lithography with the potential for extendibility beyond the 50-nm node. The three-layer absorber stack for EUVL reticles consists of an absorber, repair buffer and etch-stop layers, while a two-layer absorber stack eliminates the etch-stop layer. A portion of the mask pattern distortion can be assigned to the absorber stack's film stress. Ideally, the absorber stack films would have zero stress uniformly across the mask, which would produce zero pattern distortion when the films were removed during the pattern transfer processes. Maintaining adequate thin film stress control and uniformity relies on accurate thin film thickness measurements. The thin film deposition parameters can have a significant influence on the metrology technique's ability to measure the thin film's thickness. We have studied resistive and photonic metrology techniques for absorber stack thin film thickness measurement and stress control.

This chapter addresses the central role played by the International Union of Pure and Applied Physics (IUPAP) Commission on Symbols, Units, and Nomenclature (SUN, later known as Commission C2) in the development of international standards, in coordination with the International Bureau of Weights and Measures (BIPM). The chapter examines the roles of physicists with leadership positions in Commission C2 who furthered international collaboration on the development precision metrology by using light as an instrument for measuring distance and time. In turn, these novel techniques of precision measurement led to redefinitions of fundamental units. Commission C2 shaped metrological practice through international negotiations to redefine units and standards, through international conferences organized or facilitated by IUPAP, and through bringing early career scholars from different countries into contact with leading metrological researchers. Metrological techniques and instruments discussed in the chapter include interferometry, the maser, and atomic clocks.

X-ray computed tomography, first conceived to image internal structures of the human body, has become an important metrology technique for material quality control and dimensional quality control. As a material quality control tool, discontinuities, cracks and voids can be detected without physically destroying or damage the sample under analysis. As a dimensional metrology technique, the complete examination in a non-destructive manner of inner and outer geometries of parts and components has become possible. In this paper, material investigation of connecting rods manufactured through both casting and forging processes and dimensional evaluation of intricate geometries found on connecting rods are described and discussed from the metrology point of view.

The concepts and definitions of smart sensors are analyzed and their minimal structure and functions are made more precise. A review is provided of existing standards aimed at unification of digital sensor interfaces, simplification of sensor network creation, insertion of smart sensors into networks, and network access to sensor resources.

The standard unification of hydrophysical measurements poses a worldwide problem inasmuch as the problems of global climatology cannot be solved without reliable measurement results. Moreover, the unification of measurements is necessary at regional levels, when a common ground of interactive “conversation” becomes possible with regard for the specific hydrological characteristics of the environment, and the results of measurements obtained by different teams using different instruments are compatible and applicable, for example, to forecasting problems, etc. However, the cost of full-scale, in situ testing and measurement compels scientists to look for alternatives that will reduce costs in both time and money. Results obtained in the laboratory, of course, need to be verified in the natural environment; simultaneously, however, prerequisites are created in the laboratory for the standardization of instrument calibrations and measurement procedures under identical conditions. These prerequisites and conditions must be recorded and established by standards documentation of the International Organization for Standardization (ISO), the International Metrological Association (IMA), the World Health Organization (WHO), the United Nations Educational, Scientific, and Cultural Organization (UNESCO), and other agencies so that the practical implementation of international accords for safeguarding the environment and the global climate will be guaranteed at the international level.