| Zugriffsnummer | 51087 |
| Dokumenttyp | Konferenzartikel |
| Sprache | Englisch |
| Titel | Analysis of fine milled technical surfaces with angular resolved scatterometry |
| Autor(in); Institution |
Boesche, Sophia; 5.1, Oberflächenmesstechnik, PTB-Braunschweig
Felgner, André; 5.1, Oberflächenmesstechnik, PTB-Braunschweig
Stelzer, G.; Rheinländisch-Pfälzische TU Kaiserslautern-Landau (RPTU), Kaiserslautern, GERMANY
Seewig, Jörg; Rheinländisch-Pfälzische TU Kaiserslautern-Landau (RPTU), Kaiserslautern, GERMANY
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| Quelle/Jahr | NanoScale 2023: Dimensional and related measurements in the micro- and nanometre range:(2023), 155 - 156 |
| Artikelnummer | P-23 |
| Konferenzangaben | NanoScale 2023, Helsinki, Helsinki, 10-12, October, 2023, Finland |
| Freie Schlagworte | scatterometry ; angular-resolved ; optical microscopy ; confocal laser scanning microscopy ; fine milled surface |
| Zusammenfassung | The requirement of areal highspeed measurement at the scale of nano- and micrometer is becoming more and more important in the industry. One major application is the fast measurement of the topography of a surface, which includes waviness, form, and roughness. To characterize the roughness of a surface, a variety of different statistical parameters are calculated. The international standards, ISO 21920-2 and ISO 25178-2, define parameters solely by using the height distribution of a topology. In addition, they define parameters using lateral features of a topography, i.e. gradients, feature width etc. For example, it is the gradient distribution and its statistical moments that are important to describe tribological properties. Optical microscopes are a promising option for areal measurement. Nevertheless, in our experience commonly used optical microscopes have difficulties measuring steep gradients. This is true even for tactile measurement instruments. This problem is illustrated using Figure 1 and Figure 2. Figure 1 shows the topography of a fine-milled surface measured with a x50 objective lens. Figure 2 shows the angular distributions of the topography measured with different objective lenses. The distribution becomes smaller with higher resolution. Steep slopes lead to uncertainty of height measurement relative to sampling intervals. Therefore, for objective lenses with less resolution the steeper gradients are overestimated. A possible and fast solution to retain slopes of small-scale features is scatterometry. It is also exhibiting a good repeatability with high resolution, which can be down to milli radiant. The OptoSurf OS 500 sensor is one possible device for scatterometry. Within this sensor a LED is used as a light source. Its emission is collimated and imaged via an objective lens onto the technical surface. The incident light is reflected within a 0.9 mm light spot on the surface through a Fourier optic. The different reflection angles are recorded with 32 photodiodes mounted in a line. The intensities measured by the diodes represent the distribution of gradients of the surface structure within the illuminated area. The distribution can then be used to calculate the variance Aq, skewness Ask, and kurtosis Aku of the angular distribution. Those parameters will be used to describe the surface microstructure. Intensity values measured by the OptoSurf OS 500 of the given sample are shown in Figure 3. On the sample fine lines are visible. The intensity distributions in this figure have been measured in direction of highest and smallest Aq-value. Therefore, these are mostly the preferential direction and across it. The distribution across the structure has a higher variance and therefore a higher Aq-value than the one inline. Therefore, surfaces which are processed mostly equal, higher Aq corresponds to higher roughness parameters. It is planned to compare the results of fine milled surfaces examined with scatterometry and a confocal microscope. One aim of the ongoing work is to harmonize the results obtained by the confocal microscope and the OptoSurf OS 500 sensor. |
