| Zugriffsnummer | 54227 |
| Dokumenttyp | Konferenzartikel |
| Sprache | Englisch |
| Titel | Adaptions of a conventional imaging ellipsometer for the full Mueller matrix |
| Autor(in); Institution |
Grundmann, Jana; 4.2, Bild- und Wellenoptik, PTB-Braunschweig
Wurm, Matthias; 4.2, Bild- und Wellenoptik, PTB-Braunschweig
Duwe, Matthias; Park Systems GmbH (Accurion Division), Göttingen, GERMANY
Schneider, Stefan; Park Systems GmbH (Accurion Division), Göttingen, GERMANY
|
| Quelle/Jahr | NanoScale 2023: Dimensional and related measurements in the micro- and nanometre range:(2023), 159 - 160 |
| Artikelnummer | P-24 |
| Konferenzangaben | NanoScale, Helsinki, 10-12, October, 2023, Finland |
| Freie Schlagworte | imagin ellipsometry ; Mueller matrix ; Nanometrology |
| Zusammenfassung | The EP4 imaging ellipsometer from Park Systems (see Fig. 1) combines the properties of a conventional ellipsometer with microscopic properties to determine e.g., the thickness of film layers or the dielectric properties of the layers in a locally resolved manner. Compared to a conventional ellipsometer, an imaging ellipsometer can be used to investigate structures smaller than the illumination spot size or non-periodic structures. Ellipsometry is an optical measurement method and uses the change in the polarization state of light after interaction with the sample to draw conclusions about the optical and geometrical properties of the sample. The EP4 works as a so-called rotating-compensator ellipsometer (RCE). For this purpose, a PCSA (P: polarizer, C: compensator, S: sample, A: analyzer) setup is used, where the polarizer and the analyzer are on a defined fixed position during the measurement and the compensator is rotated for a full optical rotation cycle (180°). The varying light intensities resulting from the rotation of the compensator are detected and the signals are used to calculate the Fourier coefficients. Using these coefficients, the optical properties of the sample, such as Psi and Delta and the Mueller matrix (MM), can be determined via the Stokes-Mueller formalism. The MM is a dimensionless 4x4 matrix with values between -1 and 1 and fully describes the polarization properties of the sample. But with a PCSA setup only the first three rows of the 4x4 MM can be determined. To obtain a complete MM and thus complete information about the properties of the sample, another compensator must be added in the detector arm for a so-called PCSCA setup. For this purpose, we have extended an EP4 device and have implemented the software control of the individual components of the setup in order to be able to perform efficiently the full MM measurements. The new measurement method is called dual rotating-compensator. During the measurement, the polarizer and the analyzer are on fixed defined positions and the compensators rotate in different but harmonic angular steps. For the evaluation of the measurement and the resulting calculation of the MM, there are some points to consider in order to obtain a physically correct MM. These include the properties of the compensators, which do not behave like an ideal quarter-wave plate over the entire wavelength range. The retardation properties must be known for the entire measurable wavelength range to take them into account for the calculation of the Mueller matrix. Furthermore, the camera has a dark current, which can vary across the sensor and is superimposed on the real measurement signal. For this reason, a dark image must be recorded for the respective measurement conditions to subtract it from the measurement signal. Of course, all misalignment errors of optical components involved (polarizers, compensators, objectives) also contribute to the measurement uncertainty. For the evaluation of the routine, a transmission measurement on air is carried out in a first step, whose MM is an identity matrix. The mentioned improvement steps of the evaluation are presented and their influences on the resulted MM are shown. In addition, an outlook is given on further measurements and results besides the measurement in air. |
