Eberhard Manske

Recent developments and challenges of nanopositioning and nanomeasuring technology

Rapid progress in several high-tech industries has significantly increased the need for dimensional micro- and nano-metrology. Structures to be measured are becoming more complex with smaller structure widths and higher aspect ratios in increasingly larger surface regions and potentially highly curved surfaces. Significant international effort can be seen to develop high-capacity measuring machines with nanometre precision in growing measuring ranges up to hundreds of millimetres. This paper begins with an outline of the requirements stemming from high-tech developments currently being done or expected in the future and discusses recent developments in the field of nanopositioning and nanomeasuring technology with respect to basic measurement approaches, laser interferometer systems. The large range of nanoprobe systems usable in nanomeasuring machines is discussed, such as optical focus sensors, white light interferometer microscopes, CCD camera microscopes using the depth from the focus method, tactile stylus probes, atomic force microscopes (AFMs) and 3D microprobes. The versatile properties of these sensors allow the machine to be used in many different metrological applications. The paper also introduces a multi-sensor approach using a microscope revolver. It concludes with an illustration of metrologically challenging measurements, e.g., scanning micro-structures of curved optical surfaces or performing AFM scans of very large regions with significant data volume.

New applications of the nanopositioning and nanomeasuring machine by using advanced tactile and non-tactile probes

With the nanopositioning and nanomeasuring machine (NPM-Machine) developed at the Technische Universitat Ilmenau, subnanometre resolution and nanometre uncertainty in a measuring volume of 25 × 25 × 5 mm3 have been demonstrated in the last few years. This machine allows the most various measuring problems to be solved. In practice, however, there are too many different requirements for sensing surfaces or for detecting structures. So, this paper deals with the development and also the improvement of several optical and tactile probes for application in the NPM-Machine. A focus probe with a spot size of approximately 0.5 µm, a working distance of 1.5 mm and a resolution of less than 1 nm was developed and adopted in the NPM-Machine. In the next step, the working distance was improved to exploit the full vertical range of the NPM-Machine of 5 mm. To realize tactile sensing, an atomic force probe and tactile stylus probe were developed on the basis of the focus probe. These probing systems can acquire measuring data only by scanning the surface sequentially and point-by-point. To increase data acquisition, we realized a sensor based on a white-light interference microscope and parallel sampling of 1600 × 1200 data points. First results of fringe evaluation with laser interferometer reference are presented.

Phase measurement of various commercial heterodyne He–Ne-laser interferometers with stability in the picometer regime

In order to be able to resolve displacements of a picometer with widely used commercially available heterodyne interferometers, an advanced phase meter was developed at PTB. Key to this level of accuracy is the use of a state-of-the-art analogue-to-digital converter (ADC) board enabling the implementation of a phase-evaluation method by using embedded field programmable gate arrays. Experimental results obtained with commercially available heterodyne laser interferometer components prove that the proposed phase-evaluation procedure is capable of interpolating an optical fringe down into the picometer regime. The phase evaluation was moreover extended to track simultaneously two heterodyne beat frequencies with only two photodetectors and ADCs. Potential limitations of the long-term stability of heterodyne interferometers are discussed. The phase meter was tested, has been readily applied, can be easily adapted and is therefore to be used in a wide field of applications.

Investigations and calculations into decreasing the uncertainty of a nanopositioning and nanomeasuring machine (NPM-Machine)

Continuously increasing demands on nanopositioning and nanomeasuring (NPM) machines require a detailed analysis of and a decrease in measurement uncertainty. Initial studies have been done in the field of length and angle measurement. The analysis resulted in updated assemblies, which were investigated further. Significant improvements in mechanical stability, drift behaviour and temperature dependence were produced. To minimize the undesired heat production by the non-self-locking vertical linear drive systems, an improved weight force compensation arrangement adaptable to different object masses was developed and tested. Also, the systems natural frequencies were analysed. A modified structure with increased stiffness of the vertical drive system was designed to improve the NPMs dynamic behaviour.

Quasi-monolithic integration of silicon-MEMS with piezoelectric actuators for high-speed non-contact atomic force microscopy

High-speed atomic force microscopy (AFM) is actually a functional tool for the studies of dynamical phenomena of biological and chemical objects on a sub-second timescale. In order to increase the imaging speed, all dynamic components of AFM have to be optimized. This paper presents advancement in the development of a novel x?y scanner for high-speed non-contact AFM. We have developed a quasi-monolithic integration of a silicon parallel kinematic mechanism with piezoelectric actuators. Decoupling of motion in x?y directions is realized due to novel ?-shaped flexures. For the control of the stage motion, we employed piezoresistive sensors integrated into silicon L-shaped guidance features. Due to the use of a push?pull actuation principle, we obtained a large scanning frequency and a 6???6??m2 scanning area. The resonance frequency of the stage is about 26?kHz. The silicon stage facilitates fast quantitative imaging with high lateral resolution.

Interference signal demodulation for nanopositioning and nanomeasuring machines

The nanopositioning and nanomeasuring machine NMM-1 developed at the Ilmenau University of Technology was designed for measurements within a measuring volume of 25 × 25 × 5 mm3. The interferometric length measuring and drive systems make it possible to move the stage and corner mirror with a resolution of 0.1 nm in all three axes. The object being measured is placed on the corner mirror and can be measured with different probe systems. The high precision of the machine can be attributed to several factors. The most important is the accuracy of the interferometric measuring systems. Starting with a short description of NMM-1 and an improved equation for length calculation, this paper describes a small detail of the measurement uncertainty analysis for a displacement measurement using two positions of the measuring mirror. The overall 3D uncertainty for measurements carried out with the machine depends on the machine itself and the probe system in use as well as the specific measuring task. In particular, this paper discusses only the influence of the interference signal demodulation for homodyne interferometers.

Application of a positioning and measuring machine for metrological long-range scanning force microscopy

This article deals with a high-precision three-dimensional positioning and measuring machine and its application as a metrological long-range scanning force microscope. At the Institute of Process Measurement and Sensor Technology of the Technische Universitaet Ilmenau an interferometric nanopositioning and nanomeasuring machine has been developed. Which is able to achieve a resolution of less than 0.1 nm over the entire positioning and measurement range of 25 mm x 25 mm x 5 mm and is traceable to the length standard. The Abbe offset-free design in conjunction with a corner mirror as a reference coordinate system provides extraordinary accuracy. The integration of several probe systems and nanotools (AFM, STM, focus sensor, tactile probes) makes the nanopositioning and nanomeasuring machine suitable for various tasks in the micro- and nanotechnologies. Various probe systems have been integrated in the last few years. For example, a commercial piezo tube AFM was integrated and tested. Additionally, interferometeric measurement systems of the nanopositioning and nanomeasuring machine enables the calibration of probe systems. Also in order to achieve the best possible measurement results special probe systems have been developed and tested and are discussed briefly.

A focus sensor for an application in a nanopositioning and nanomeasuring machine

A focus sensor on the basis of a hologram laser unit was developed and successfully tested in a nanopositioning and nanomeasuring machine as a zero indicator. The high resolution of the focus sensor is due to a high-precision optical adjustment and special solutions incorporated into the electronic parts. Thus, any sensor malfunctions caused by back-reflected light inside of the assembly could be completely avoided by means of the special high-frequency modulation and laser power stabilization. Common mode noise reduction provides the high SNR of the output signals. The measurements were made according to a dynamic principle by permanent difference formation between the output signal of the focus sensor and the length value of the z-interferometer of the nanopositioning and nanomeasuring machine. The measuring results are presented, and further possibilities of application are outlined.

Automated setup for non-tactile high-precision measurements of roundness and cylindricity using two laser interferometers

An automated setup for non-tactile high-precision measurements of roundness and cylindricity of ring gauges is presented. The aim is to minimize classical problems of tactile and radial roundness measurements such as the error influences of the used rotary table and the work piece alignment and thus to increase the accuracy and reduce the measurement time. To achieve those aims, a double interferometer concept was chosen and combined with a measurement system for the work piece alignment, a high-precision rotary table and an automated four-axis adjustment unit. The main alignment errors of the work pieces (e.g. ring gauges) such as eccentricity and tilting are either suppressed or directly detected and consequently reduced by the automated four-axis adjustment unit. Due to the non-tactile measurement concept, higher measurement velocities are achievable and surface destruction is prevented. In combination with the contactless energy supply of the four-axis adjustment unit, the radial run of the rotary table is not affected.

The Metrological Basis and Operation of Nanopositioning and Nanomeasuring Machine NMM-1Metrologische Grundlagen und Wirkungsweise der Nanopositionier- und Messmaschine NMM-1

Abstract After an explanation of the set-up of a nanomeasuring machine NMM-1, its high performance is described with a metrological analysis. This analysis shows some of today´s limits of nanopositioning and nanomeasuring engineering. Single, double and triple beam plane mirror interferometers are applied in the nanomeasuring machine in order to measure and control the six degrees of freedom of the 3D nanopositioning stage. The various applications of the nanomeasuring machine are based on the installation of optical and tactile nanoprobes above the 3D nanopositioning stage. The set-up, function and measurement results of some zero-point nanoprobes in combination with the nanomeasuring machine are explained.