| Zugriffsnummer | 51097 |
| Dokumenttyp | Konferenzartikel |
| Sprache | Englisch |
| Titel | EURAMET comparison 1242: Measurement of areal roughness by optical microscopes |
| Autor(in); Institution |
Gao, Sai; 5.1, Oberflächenmesstechnik, PTB-Braunschweig
Felgner, André; 5.1, Oberflächenmesstechnik, PTB-Braunschweig
Dziomba, Thorsten; 5.1, Oberflächenmesstechnik, PTB-Braunschweig
Koenders, Ludger; PTB-Braunschweig, retired staff
Picotto, G-B.; Istituto Nazionale di Ricerca Metrologica, Torino, Italy
Bellotti, R.; Istituto Nazionale di Ricerca Metrologica, Torino, Italy
Zucco, M.; Istituto Nazionale di Ricerca Metrologica, Torino, Italy
Bossen, A.; Federal Institute of Metrology, Bern-Wabern, SWITZERLAND
Meli, F.; Federal Institute of Metrology, Bern-Wabern, SWITZERLAND
Kotter, Christian; Federal Institute of Metrology, Bern-Wabern, SWITZERLAND
Heikkinen, V.; VTT Technical Research Centre - Centre for Metrology, Espoo, FINLAND
Lassila, A.; VTT Technical Research Centre - Centre for Metrology, Espoo, FINLAND
|
| Quelle/Jahr | NanoScale 2023: Dimensional and related measurements in the micro- and nanometre range:(2023), 132 - 134 |
| Artikelnummer | P-30 |
| Konferenzangaben | NanoScale 2023, Helsinki, Helsinki, 10-12, October, 2023, Finland |
| Freie Schlagworte | Euramet comparison ; areal surface texture ; optical microscope |
| Zusammenfassung | Within the framework of the EURAMET project 1242, coordinated by PTB, comparative measurements of areal roughness with different optical microscopes were carried out for the first time at five national metrology institutes. Roughness measurements were performed on four samples. Three samples, which require a rather high spatial resolution but a rather small FOV, are two lapped Si chips (ARS-F1 and ARS-F2) from SiMetrics, Germany, and one ultrafine roughness standard (UFRS) produced by focused ion beam (FIB) from point electronic, Germany. The fourth sample (B40-VP04) is from Rubert & Co., England, with features of very long wavelengths, thus a much larger measurement field is required to reliably determine the roughness. All samples show (nominally) isotropic arbitrary roughness. To get some coarse information about the instrument transfer function, measurements were performed on a resolution standard of type RS-N from SiMetrics. They are realized as 1D gratings with lines of rectangular shape with a nominal height of 190 nm but different grating pitches in the range of 300 nm to 6 μm. The comparison revealed that especially the finer roughness standards with comparatively smallscale features cause unexpectedly great difficulties in optical roughness measurement. The values reported by the individual institutes, e.g. for the roughness parameter Sq, deviate from the reference value by up to 60 %, and the uncertainties reported proved to be too small. In addition, the measurement results show a large dependence on the selected measurement principle and the objectives used. The preliminary analysis shows that the bandwidth of the spatial frequency spectrum and the slope angles of the surface features have a significantly greater influence on the roughness results than previously assumed. By comparing the slope distributions of the surface as measured with different optical microscopes with that of AFM measurements, the following effects are observed: i. If the histograms of the slope distribution of the measured surfaces are similar, the calculated roughness parameters are comparable; ii. If the histogram of the slope distribution of the measured surfaces is broader, the roughness parameter Sq is larger. The slopes measured by some instruments, especially the white light interferometers, are even much larger than the theoretical measurable slope calculated from the numerical aperture, which indicates that the artifacts obtained by optical measurements are leading to strong deviations of the measured roughness characteristics, e.g. sharp steep artefacts that often cannot be identified easily in the obtained images. Therefore, the maximum slope that can be measured reliably by a microscope objective needs to be characterized. Power spectral density (PSD) distributions of the ARS-F1 measured by different optical microscopes have also been calculated and the relationship between the PSD and the surface texture parameters needs to be further investigated. The comparison also underlines that if only rectangular gratings with different pitches are used, the transfer behavior of an instrument for different slopes cannot be fully characterized. Therefore, sinusoidal structures should be used as well for a determination of the topographic spatial resolution and instrument transfer function. The challenge for analyzing the very long wavelength standard (B40-VP04) is the validation of the stitching methods that are implemented in the instruments or developed by the user. Here, the selected stitching algorithm, leveling strategy, and preprocessing methods chosen are responsible for the poor consistency of the roughness values reported by the participants. However, a central reevaluation of the raw data provided by the participants with an evaluation software developed by PTB showed that the measurement results of the participants agreed very well once a uniform procedure is applied. |
Zitierung
Gao, S., Hüser, D., Felgner, A., Dziomba, T., Koenders, L., Picotto, G.-B., Bellotti, R., Zucco, M., Bossen, A., Meli, F., Kotter, C., Heikkinen, V., & Lassila, A. (2023). EURAMET comparison 1242: Measurement of areal roughness by optical microscopes. NanoScale 2023, Helsinki, Helsinki, 10-12, October, 2023, Finland.