15SIB09 3DNano: Traceable three-dimensional nanometrology

• Forschungsstelle: METAS
• Projektnummer: F-5111.30075
• Projekttitel Englisch: 15SIB09 3DNano: Traceable three-dimensional nanometrology

Schlüsselwörter (Englisch)

Traceable three-dimensional metrology, Line width, Step height, Pitch, Roughness, Nanoparticles, Atomic force microscopy (AFM), Scanning electron microscopy (SEM), Probe sample interaction

Kurzbeschreibung (Englisch)

The overall goal of this project is to meet current and future requirements for traceable 3- dimensional (3D) metrology at the nanometre level with measurement uncertainties below 1 nm. To achieve this requires new routes for traceability, further developments of existing instruments and validated 3D measurement procedures. Additionally, new calibration artefacts must be developed and made available to industry as traceable reference standards to enable valid comparison of fabrication and measurement results, and establish a robust basis for design of objects with traceable nanoscale dimensions and tolerances.

Scanning Probe Microscopes (SPMs) available in national metrology institutes (NMIs) have low uncertainties, are traceable to the SI-metre and significantly outperform commercial SPMs in accuracy. However, there is a large gap between SPMs and the rest of 3D metrology. Conventional 3D metrology is based on coordinate measuring machines (CMMs) that have been significantly improved in recent decades e.g. micro CMMs, therefore they can reach almost nanometre level uncertainties. SPM technology has the potential to offer even lower uncertainties. However, the measuring principle, measurand definitions and current written standards are still very far from what could be used for 3D measurements, which explains the use of the term 2.5D for SPM techniques. The aim of the project is to further develop SPM instrumentation, measurement procedures, data interpretation and reference materials to bridge this gap, as proper understanding of probe-sample interactions is crucial for the reduction of measurement uncertainty.

This is a joint research project carried out in the framework of the European Metrology Programme for Innovation and Research (EMPIR) (see:http://www.euramet.org/research-innovation/empir/). The EMPIR initiative is co-funded by the European Unions's Horizon 2020 research and innovation programme and the participating states. METAS is one of the project partners in the Project.

Projektziele (Englisch)

The scientific and technical objectives of this project are to:

1. Reduce the 3D nanomeasurement uncertainty, by means of a bottom up approach, to less than 1 nm for nanodimensional measurands (including line width, height, pitch, and edge/width roughness) on engineered nanostructures and nanoparticles. In addition, to reduce the noise level of metrological AFMs (MAFMs) to 0.1 nm (rms) using a top-down approach, to raise the scanning speed up to 1 mm/s, and to extend the scanning range up to 25 mm/s by further developing the state-of-the-art optical and x-ray interferometry (XRI).
2. Develop reference materials for 3D nanometrology tools including AFM and Scanning Electron Microscopy (SEM). In particular, to realise test structures for characterising the tip geometry in AFMs and the beam size in SEMs and reference standards for width and sidewall roughness measurements.
3. Widen the understanding of probe-sample interactions in AFM and SEM measurements for reducing the measurement uncertainty. In particular, to study the tip-sample interaction force of AFM line width and nanoparticle measurements; to model the image formation of SEM; and to investigate the influence of humidity on AFM measurements.
4. Develop a hybrid metrology for merging measurement results from either different tools (e.g. AFM, SEM, Transmission Electron Microscopy (TEM), Mueller polarimetry and optical scatterometry) or different channels of a single tool.
5. Facilitate the take up of the technology and measurement infrastructure developed by the project by the measurement supply chain (accredited laboratories, instrument manufacturers) and end users (semiconductor industry, precision engineering, optical industry and nanoparticle researchers).

Abstract (Englisch)

The aim of the METAS contribution in this project was to improve the calibration of nanoparticles by an AFM, to improve structure width measurements and to further develop the 3D metrology AFM instrument. METAS has made progress especially in particle calibration and tip geometry determination. At the Nanoscale Conference 2019 in Braunschweig, Germany Oct. 2019, the findings on particle deformations at the substrate contact were presented. For the first time, experimental particle deformation values for small polystyrene (PS) particles with diameters of 50 nm to 700 nm were introduced.

Time schedule and budget were well met. The project objectives were all formally fulfilled, but due to some instrumental difficulties and the late availability of produced artefacts, further results were rather modest.

Umsetzung und Anwendungen (Englisch)

The calibration of the size distribution of reference nanoparticles is becoming increasingly important. Thanks to this project, calibration methods have been refined and there is an increasing demand for customer calibrations at METAS. The results of the measured particle deformations now allow more accurate particle calibrations. Corresponding Calibration and Measurement Capabilities (CMCs) within the framework of the CIPM MRA could be newly entered or improved. Internally, METAS uses the developed AFM methods for the calibration of reference particle samples used for particle counters of the Environmental Laboratory. Methods developed for the geometric characterization of AFM tips help to reduce the measurement uncertainty of structure width calibrations.

Publikationen / Ergebnisse (Englisch)

• Anaïs Nicolet and Felix Meli 2017 "Spherical polystyrene particle deformation measured with the AFM", Meas. Sci. Technol. 28 03400
• R. Koops, M. Valtr, G. Zeng, A. Yacoot, E. Heaps, G. Dai, N. Sebaihi, S. Hauser, T. Hausotte, Yiting Wu, G. Papageorgiou, P. Dimitrakis, H. Spruit, E. van Zeijl, G.B. Picotto and V. Korpelainen, "Progress on the development of reference standards for 3D nanometrology", submitted to MST.
• Further publications listed at https://www.ptb.de/emrp/15sib09-publications.html