Nanomeasuring Machine Research Articles

Investigations on tip-based large area nanofabrication and nanometrology using a planar nanopositioning machine (NFM-100)

This paper explores large area application of tip-based nanofabrication by field emission scanning probe lithography and showcases the simultaneous possibility of atomic force microscopy on macroscopic scales. This is made possible by the combination of tip-based technology and a planar nanopositioning and nanomeasuring machine. Using long range atomic force microscopy measurement of regular grating structures, the performance of the machine is thoroughly characterized over the full 100 mm range of motion of the positioning machine, which was confirmed by repeated measurements. After initially focussing on achieving the minimum line width of < 40 nm in microscopic areas, a grating with a pitch of 1 μm is additionally fabricated over a total length of 10 mm, whereby the dimensions and deviations are also considered.

Modular Direct Laser Writing setup for high precision nanostructuring

Abstract The increasing demand for micro- and nanofabrication and in parallel the increasing requirements on feature size and resolution is leading to an enormous growth in the field of multi-photon three-dimensional fabrication. To enable new and diverse investigations in this field and to enable high precision for nanofabrication on large areas, a high precision positioning system is combined with an ultra-short pulse laser system. The aim is a modular setup with constant adherence to the Abbe-comparator principle in order to achieve systematic improvements in the area of Direct Laser Writing. For a high-quality identification of the microstructures a measurement tool based on atomic force microscopy is used. To enable the fabrication of continuous micro- and nanostructures on large area, an extremely high positioning precision is used, where no further stitching methods are necessary. Therefore as base of the Direct Laser Writing system the nanopositioning and nanomeasuring machine (NMM-1) is used, which was developed at Technische Universität Ilmenau together with SIOS Meßtechnik GmbH, with a positioning volume of 25 mm × 25 mm × 5 mm and a positioning resolution in the sub-nanometer range. First investigations already confirmed that microfabrication with a Femtosecond Laser and the NMM-1 could be realized and showed the possibility of further developments in the field of Direct Laser Writing. Now the modular structure as a research platform is designed in such a way that the various extensions and measurement setups for large-scale investigations can always be implemented in a metrologically traceable manner. The presented work shows the development of a modular functional setup of an exposure system and NMM-1, which enables micro- and nanofabrication and an improvement in the structure size over large areas.

Methods and Technical Means for Ensuring Uniformity of Nanoparticle Size Measurements

The paper proposes a set of technical tools for solving the problem of ensuring the uniformity of measurements of micro- and nanoparticles. To do this, it is necessary to ensure the traceabilityof particle size measurements to a unit of length – a meter, as well as equivalent diameters used in measurements in various dispersed media (aerosols and suspensions). To ensure traceability of particle diameter measurements to the meter, it is proposed to use a nanomeasuring machine with an atomic force microscope as a probing system. The paper presents a diagram of the measuring system, describes the principle of operation of the machine and the method for measuring particle sizes. The main alleged sources of errors in particle measurement by this method are also identified. To ensure the traceability of measurements of the hydrodynamic diameter of nanoparticles, which characterizes particles in a liquid (suspension), it is proposed to use a nanoparticle size analyzer that implements the method of dynamic light scattering. The scheme of the analyzer with a description of the principle of measuring the size of nanoparticles by the method of dynamic light scattering is presented in the paper. The scheme of the column of the analyzer of the differential electrical mobility of particles is presented to ensure the traceability of measurements of their diameter, which is equivalent in electrical mobility. Diameter is usually used to characterize particles in the aerosol state. A diagram of an analyzer for the differential electric mobility of particles is given with a description of the operating principle, a formula for calculating the particle diameter is derived.

Metrological nanopositioning combined with two-photon direct laser writing

Abstract The extension of nanopositioning and nanomeasuring machines (NPM-machines) to fabrication machines by using a femtosecond laser for the implementation of direct laser writing by means of two-photon absorption (2PA) is a promising approach for cross-scale metrological fabrication in the field of lithographic techniques [24]. To this end, a concept for integrating two-photon technology into an NPM machine was developed and implemented, followed by a characterization of the system and targeted investigations to provide evidence for the synergy of the two techniques. On this basis, a new approach to high-throughput micro- and nano-fabrication was developed and investigated, demonstrating new possibilities in cross-scale, high-precision manufacturing [6]. This mix-and-match approach is based on a combination of 2PA laser writing with field emission lithography to fabricate masters for subsequent nanoimprint lithography. Not only the advantages of the large positioning range of the NMM-1 could be highlighted, but also the advantages resulting from the highly accurate positioning. A systematic reduction of the distance between two adjacent lines resulted in a minimum photoresist width of less than 30 nm 30\hspace{0.1667em}\text{nm} [16], which can be classified among the smallest distances between two laser-written lines described in the literature [4], [10], [20]. The center-to-center distance of the lines of about 1.695 µm 1.695\hspace{0.1667em}\text{\textmu m} at a numerical aperture of 0.16 and a wavelength of 801 nm is only about 56 % 56\hspace{0.1667em}\text{\%} of the Rayleigh diffraction limit extended for the two-photon process. Thus, for the first time, a resist width far below the diffraction limit could be realized with conventional two-photon laser writing in positive photoresist.

The error of transferring the size of a unit of length – a meter in the nanometer range using the nanomeasuring machine

The paper describes the principle of measuring linear dimensions using a nano-measuring machine (NMM), which implements the method of measuring three coordinate axes in the range of 25X25X5 mm3. Sources of non-excluded systematic measurement errors are identified, which are conventionally divided into factors associated with the method of measuring length using an interferometer and factors determined by the design and technological features of the nano-measuring machine. Statistical estimates of the measurement result have been determined and the error in transferring the size – meter length in the nanometer range of measurements has been calculated. The results obtained assert that the nano-measuring machine is a unique tool that allows one to carry out measurements of millimeter dimensions with nanometer accuracy. The results obtained can be used for metrological assessment of the step height and step width, when calibrating measuring instruments in the nanometer range, roughness measures in a large range when calibrating profilometers and contourographs, as well as templates and micrometer objects for measuring high-precision microscopes.

Development and Implementation of a Rotating Nanoimprint Lithography Tool for Orthogonal Imprinting on Edges of Curved Surfaces

Uniform molding and demolding of structures on highly curved surfaces through conformal contact is a crucial yet often-overlooked aspect of nanoimprint lithography (NIL). This study describes the development of a NIL tool and its integration into a nanopositioning and nanomeasuring machine to achieve high-precision orthogonal molding and demolding for soft ultraviolet-assisted NIL (soft UV-NIL). The process was implemented primarily on the edges of highly curved plano-convex substrates to demonstrate structure uniformity on the edges. High-resolution nanostructures of sub-200-nm lateral dimension and microstructures in the range of tens of microns were imprinted. However, the nanostructures on the edges of the large, curved substrates were difficult to characterize precisely. Therefore, microstructures were used to measure the structure fidelity and were characterized using profilometry, white light interferometry, and confocal laser scanning microscopy. Regardless of the restricted imaging capabilities at high inclinations for high-resolution nanostructures, the scanning electron microscope (SEM) imaging of the structures on top of the lens substrate and at an inclination of 45° was performed. The micro and nanostructures were successfully imprinted on the edges of the plano-convex lens at angles of 45°, 60°,and 90° from the center of rotation of the rotating NIL tool. The method enables precise imprinting at high inclinations, thereby presenting a different approach to soft UV-NIL on curved surfaces.

Tip- and Laser-based 3D Nanofabrication in Extended Macroscopic Working Areas

The field of optical lithography is subject to intense research and has gained enormous improvement. However, the effort necessary for creating structures at the size of 20 nm and below is considerable using conventional technologies. This effort and the resulting financial requirements can only be tackled by few global companies and thus a paradigm change for the semiconductor industry is conceivable: custom design and solutions for specific applications will dominate future development (Fritze in: Panning EM, Liddle JA (eds) Novel patterning technologies. International society for optics and photonics. SPIE, Bellingham, 2021. https://doi.org/10.1117/12.2593229). For this reason, new aspects arise for future lithography, which is why enormous effort has been directed to the development of alternative fabrication technologies. Yet, the technologies emerging from this process, which are promising for coping with the current resolution and accuracy challenges, are only demonstrated as a proof-of-concept on a lab scale of several square micrometers. Such scale is not adequate for the requirements of modern lithography; therefore, there is the need for new and alternative cross-scale solutions to further advance the possibilities of unconventional nanotechnologies. Similar challenges arise because of the technical progress in various other fields, realizing new and unique functionalities based on nanoscale effects, e.g., in nanophotonics, quantum computing, energy harvesting, and life sciences. Experimental platforms for basic research in the field of scale-spanning nanomeasuring and nanofabrication are necessary for these tasks, which are available at the Technische Universität Ilmenau in the form of nanopositioning and nanomeasuring (NPM) machines. With this equipment, the limits of technical structurability are explored for high-performance tip-based and laser-based processes for enabling real 3D nanofabrication with the highest precision in an adequate working range of several thousand cubic millimeters.

Investigation of a metrological atomic force microscope system with a combined cantilever position, bending and torsion detection system

Abstract. This article presents a new metrological atomic force microscope (MAFM) head with a new beam alignment and a combined one-beam detection of the cantilever deflection. An interferometric measurement system is used for the determination of the position of the cantilever, while a quadrant photodiode measures the bending and torsion of the cantilever. To improve the signal quality and reduce disturbing interferences, the optical design was revised in comparison to the systems of others (Dorozhovets et al., 2006; Balzer et al., 2011; Hausotte et al., 2012). The integration of the MAFM head in a nanomeasuring machine (NMM-1) offers the possibility of large-scale measurements over a range of 25mm×25mm×5 mm with sub-nanometre resolution. A large number of measurements have been performed by this MAFM head in combination with the NMM-1. This paper presents examples of the measurements for the determination of step height and pitch and areal measurement.

Metrological investigation of a scanning electrostatic force microscope on a nano-positioning and nano-measuring machine

A surface profile measurement system was developed by combining a scanning electrostatic force microscope (SEFM) and a nano-measuring machine (NMM-1) and its characteristics were evaluated. SEFM is a type of scanning probe microscope (SPM) advocated in 2012. In SEFM, eliminating the trade-off between measurement accuracy, measurement speed, and stability has been a problem. As with other SPMs, the positioning accuracy of the probe and sample directly affects the measurement accuracy in SEFM. In this research, the SEFM principle was applied to the NMM-1, which is a high-precision positioning platform that achieves an uncertainty of smaller than 10 nm. In order to improve the force detection sensitivity, a probe polishing and assembling procedures was devised and, as a result, the quality factor of the sensor has been significantly improved. Furthermore, a method for optimizing scan parameters based on a theoretical model was proposed. The noise level of the measurement results was reduced by setting appropriate parameters, which agreed well with the theory. Profile measurements utilizing the developed measurement system were performed on line-and-space samples with an amplitude of 270 nm and a pitch of 10 μm. The results were compared with a conventional atomic force microscope as a reference. A surface measurement was performed on the sample, and a complete non-contact scan of a measurement range of 25 μm × 25 μm was demonstrated.

Experimental Setup for the Investigation of Reproducibility of Novel Tool Changing Systems in Nanofabrication Machines

Nanomeasuring machines developed at the Technische Universität Ilmenau enable three-dimensional measurements and manufacturing processes with the lowest uncertainties. Due to the requirements for these processes, a highly reproducible and long-term stable tool changing system is needed. For this purpose, kinematically determined couplings are widely used. The state-of-the-art investigations on those are not sufficient for the highest demands on the reproducibility required for this application. A theoretical determination of the reproducibility based on analytical or numerical methods is possible, however not in the desired nanometer range. Due to this, a measurement setup for the determination of the reproducibility in five degrees of freedom with nanometer uncertainty was developed. First, potential measuring devices are systematically examined and measurement principles were developed out of this. A three-dimensional vector-based uncertainty analysis is performed to prove the feasibility of the measurement principle and provides a basis for further design. As a result, a translatory measurement uncertainty of 10 nm and a rotatory uncertainty of 11 nrad can be reached. Afterwards, the measurement setup is designed, focusing on the metrological frame and the lift-off device. The developed setup exceeds the uncertainties of the measurement setups presented in the state-of-the-art by an order of magnitude, allowing new in-depth investigations of the reproducibility of kinematic couplings.

Fundamental Investigations in the Design of Five-Axis Nanopositioning Machines for Measurement and Fabrication Purposes

The majority of nanopositioning and nanomeasuring machines (NPMMs) are based on three independent linear movements in a Cartesian coordinate system. This in combination with the specific nature of sensors and tools limits the addressable part geometries. An enhancement of an NPMM is introduced by the implementation of rotational movements while keeping the precision in the nanometer range. For this purpose, a parameter-based dynamic evaluation system with quantifiable technological parameters has been set up and employed to identify and assess general solution concepts and adequate substructures. Evaluations taken show high potential for three linear movements of the object in combination with two angular movements of the tool. The influence of the additional rotation systems on the existing structure of NPMMs has been investigated further on. Test series on the repeatability of an NPMM enhanced by a chosen combination of a rotary stage and a goniometer setup are realized. As a result of these test series, the necessity of in situ position determination of the tool became very clear. The tool position is measured in situ in relation to a hemispherical reference mirror by three Fabry–Pérot interferometers. FEA optimization has been used to enhance the overall system structure with regard to reproducibility and long-term stability. Results have been experimentally investigated by use of a retroreflector as a tool and the various laser interferometers of the NPMM. The knowledge gained has been formed into general rules for the verification and optimization of design solutions for multiaxial nanopositioning machines.

Two-Photon Direct Laser Writing Beyond the Diffraction Limit Using the Nanopositioning and Nanomeasuring Machine

Since the first realization of two-photon direct laser writing (DLW) in Maruo et al. (Opt Lett 22:132–134, 1997), the manufacturing using direct laser writing techniques spread out in many laboratories all over the world. Photosensitive materials with different material properties open a new field for micro- and nanofabrication. The achievable structuring resolution using this technique is reported to be sub-100 nm (Paz et al. in J. Laser Appl. 24:042004, 2012), while a smallest linewidth of 25 nm could be shown in Tan et al. (Appl Phys Lett 90:071106, 2007). In our approach, the combination of DLW with the nanopositioning and nanomeasuring machine NMM-1 offers an improvement of the technique from the engineering side regarding the ultra-precise positioning (Weidenfeller et al. in Adv Fabr Technol Micro/Nano Opt Photon XI 10544:105440E, 2018). One big benefit besides the high positioning resolution of 0.1 nm is offered by the positioning range of 25,hbox {mm} times 25,hbox {mm} times 5,hbox {mm} (Jäger et al. in Technisches Messen 67:319–323, 2000; Manske et al. in Meas Sci Technol 18:520–527, 2007). Thus, a trans-scale fabrication without any stitching or combination of different positioning systems is necessary. The immense synergy between the highly precise positioning and the DLW is demonstrated by the realization of resist lines and trenches whose center-to-center distance undergoes the modified diffraction limit for two-photon processes. The precise positioning accuracy enables a defined distance between illuminated lines. Hence, with a comparable huge width of the trenches of 1.655,upmu hbox {m} due to a low effective numerical aperture of 0.16, a resist line of 30 nm between two written trenches could be achieved. Although the interrelationships for achieving such narrow trenches have not yet been clarified, much smaller resist lines and trench widths are possible with this approach in the near future.

A metrological atomic force microscope system

A new metrological atomic force microscope (MAFM) with combined deflection detection system that comprises a homodyne interferometer and an optical beam deflection measuring system are presented. The combination allows the simultaneous three-dimensional detection of position, bending and torsion of the cantilever. Two wedge plates with a wedge angle of 0.5° have been integrated to reduce the disturbing interferences. The new measuring system uses two tiltable plane mirrors and a shiftable focus lens to adjust the direction of the focused laser beam and the position of the focus. The integration of the MAFM head in a nanomeasuring machine (NMM-1) creates the possibility of traceable dimensional measurements over a large range of 25 mm × 25 mm × 5 mm with sub-nanometre resolution. This paper introduces its setup, realisation and metrological properties, such as stability of the characteristic curves, noise level and combined measurement uncertainty. Finally, exemplary measurement results are presented.

Coordinate transformation and its uncertainty under consideration of a non-orthogonal coordinate base

Nanopositioning and nanomeasuring machines are 3D coordinate measuring systems with nanometer precision at measurement volumes in the cubic centimeter range whose coordinate base is formed by an interferometer system with a common mirror corner. This mirror corner shows a typical deviation from the orthogonal coordinate base of up to 17 µrad with an uncertainty of 0.07 µrad. After a brief description of nanomeasuring and nanopositioning machines, a transformation model from the skewed coordinate system into the orthogonal coordinate system is determined. Starting from this complete transformation model, the result of model simplifications on the transformation behaviour is analysed and discussed. A GUM-based uncertainty calculation shows that the linearised coordinate transformation does not increase the error and the uncertainty significantly.

Multiprobe scanning probe microscope using a probe-array head

We have developed a microelectromechanical system (MEMS)-based multiprobe scanning probe microscope (SPM) to improve imaging efficiency. The SPM head contains seven identical MEMS probes, and each of them integrates a displacement sensor and a Z-axis actuator. Force constant mode is designed based on the force feedback strategy rather than on the position feedback strategy for this kind of SPM head. A nano-measuring machine is equipped with the lateral XY scanners, which can reach a motion range of 25 mm × 25 mm. After calibration, the measurement of one-dimensional grating has been made to demonstrate the capability of multiprobe scanning.

Progress of nanopositioning and nanomeasuring machines for cross-scale measurement with sub-nanometre precision

Nanopositioning and nanomeasuring machines (NPM-machines), developed at Technische Universität Ilmenau, have provided high-precision measurement and positioning of objects across ten decades, from 20 pm resolution up to 200 mm measuring range. They work on the basis of the error-minimal, extended six degrees of freedom Abbe-comparator principle, with high-precision fibre-coupled laser interferometers and optical or atomic force probes. These machines are suitable not only for measuring but also for positioning with an outstanding sub-nanometre performance.Measurements on precision step heights up to 5 mm show a repeatability of 20 pm. Consecutive step positioning of 80 pm can be demonstrated. With the new approach of an atomic clock-stabilized He–Ne-laser via a high-stable-frequency comb, we achieve a frequency stability of less than 300 Hz, respectively 0.6 ċ 10−12 relative frequency stability within 1 h at an integration time of 1 s. For the first time, we can demonstrate a direct, permanent and unbroken chain of traceability between the laser interferometric measurement within an NPM-machine and a GPS satellite-based atomic clock. This paper presents a closer insight into the scientific and metrological background as well as unrivalled measurement results, and discusses the great possibilities of this new technology.

Cryogenic etching for pattern transfer into silicon of Mix-and-Match structured resist layers

A Mix-and-Match lithography method for a high-resolution, high-precision and cost effective lithography tool using DLW and FE-SPL was developed and successfully realized. The pattern transfer from the photoresist to the silicon substrate is done by so-called “cryogenic etching”. It means that the substrate is cooled down to cryogenic temperatures. In contrast to etching processes at standard room temperature, the cryogenic temperatures (below −100 °C) enable a highly anisotropic etching process. The difference between etching at room temperature compared to cryogenic etching is carried out in this work. The advantages of the etching process are highlighted for the pattern transfer from Mix-and-Match-structured samples. Therefore, the used photoresist mr-P 1201LIL (microresist technologies GmbH) has been examined concerning its silicon-to-resist selectivity which could be determined to be 6:1 for the applied etching recipe. Using cryogenic etching, we are now able to transfer the Mix-and-Match-structured patterns into silicon with appreciable high selectivities. This opens a novel pathway for the manufacturing of quantum devices on large wafers.The paper discusses current research results based on the TU Ilmenau Nanopositioning and Nanomeasuring Machines (NPMM) including the novel application of nanofabrication. First, the basic setup and the resulting benefits of the NPMMs for measuring and fabrication in a working volume of up to 200 mm × 200 mm × 25 mm while abiding nanometer accuracy is described. This is in contradiction to state-of-the-art AFM scanners, which have a limited working range of appr. 100 μm × 100 μm. Next, the principle and the results of different nanofabrication technologies are shown. These include Scanning Probe Lithography (SPL), Direct Laser Writing (DLW) and UV-nanoimprint lithography (NIL). Last, efforts for further improving the feature placement accuracy of the NPMMs as well as attempts to combine several fabrication technologies to improve their throughput are touched on.

Tip-based nano-manufacturing and -metrology

Sub-5 nm lithography and metrology are the key technologies for more CMOS and beyond CMOS nanoelectronics. To keep up with scaling down of nanoelectronic components, novel instrumentation for nanometer precise placement, overlay alignment, and measurement are essential to enable fabrication of next generation nanoelectronic systems. In particular, scanning probe microscopy (SPM) based methods for surface modification and measurement are the emerging techniques for producing and testing of sub-5 nm features. In this article, the authors demonstrate nanoscale lithography and coordinate metrology technologies, both being based on SPM methodology. Scanning probes with a piezoresistive deflection read-out and an integrated deflection actuator, later on referred to as the active piezoresistive cantilevers, were used for lithography employing field emission patterning. They were also integrated with the so-called nanomeasuring machine (NPM) and used for surface imaging, which made it possible to measure the structure dimensions in the 25 × 25 × 5 mm3 space with 0.1 nm resolution and great accuracy. The basic NPM concept relies on a unique arrangement, enabling the so-called Abbe error-free measurements in all axes over the total scan range. The combination of the active piezoresistive cantilevers and NPM technologies makes it possible to store the exact location on the investigated surface, which can be found again with an accuracy of less than 2.5 nm. This system is also predestinated for the critical dimension, quality, and overlay control.

Voxel size and calibration for CT measurements with a small field of view

Dimensional tomographic measurement is influenced by many factors. To achieve metrological traceability of results, knowledge of influence factors and their effect on measurement is important. This includes knowledge of the true value of voxel size and edge detection. Phantoms used for characterization and correction of error sources are calibrated usually on tactile or optical coordinate measuring machines. The challenge here is the manufacturing and calibration of small phantoms, which can be used in the field of view approximately 1 mm and less, which is the case of tomographic devices aiming at high resolution. In this work, abilities of a nano-coordinate measuring machine (nano-CMM) SIOS NMM-1 (Nanopositioning and Nanomeasuring Machine) to calibration of a phantom for X-ray computed tomography (CT) with the small field of view and high resolution are tested.

Trans-scale Nanofabrication with Nanopositioning and Nanomeasuring Machines

Nanofabrication in macroscopic working areas addresses the manipulation with nanometer precision in large scale working areas of several hundred millimeters. In order to reduce the fabrication time of large objects, high dynamic position tracking is required. The position and orientation of the nanopositioning and nanomeasuring machine have to be controlled permanently to compensate external disturbances like ground motion, sound waves, et cetera. Many applications have strict demands on following the track, e.g. to reduce the line roughness. High performant data and signal processing and efficient control algorithms are required to overcome these challenges. This work presents the nanopositioning and measuring machine as well as the utilized control system. Several scanning and fabrication experiments have been carried out in order to demonstrate the performance of the setup.