| Zugriffsnummer | 54230 |
| Dokumenttyp | Konferenzartikel |
| Sprache | Englisch |
| Titel | Enhancement of an on-going photomask CD-comparison by a new approach for model-based optical measurements |
| Autor(in); Institution |
Krüger, Jan; 4.2, Bild- und Wellenoptik, PTB-Braunschweig
Bergmann, Detlef; 4.2, Bild- und Wellenoptik, PTB-Braunschweig
Köning, Rainer; 4.2, Bild- und Wellenoptik, PTB-Braunschweig
Bodermann, Bernd; 4.2, Bild- und Wellenoptik, PTB-Braunschweig
Eder, Christian; Hochschule Aalen, Aalen, GERMANY
Manley, Phillip; JCMwave GmbH, Berlin, GERMANY; Zuse Institute Berlin, GERMANY
Schneider, Philipp-Immanuel; JCMwave GmbH, Berlin, GERMANY; Zuse Institute Berlin, GERMANY
Zschiedrich, Lin; JCMwave GmbH, Berlin, GERMANY; Zuse Institute Berlin, GERMANY
|
| Quelle/Jahr | NanoScale 2023: Dimensional and related measurements in the micro- and nanometre range:(2023), 165 - 166 |
| Artikelnummer | P-26 |
| Konferenzangaben | NanoScale, Helsinki, 10-12, October, 2023, Finland |
| Freie Schlagworte | imagin ellipsometry ; Mueller matrix ; Nanometrology |
| Zusammenfassung | The image formation in a vision-based measurement instrument is a complicated process. The illumination, the light-matter interaction at the sample, optical aberrations of the imaging system and short-comings of the camera will all affect the final image. The distorted intensity distributions at the edge locations of a single line for example, lead to inherent difficulties in the evaluation of its width/ critical dimension (CD). Since the positions of the physical edges cannot be easily located in the distorted images, a sophisticated evaluation scheme is required here. Trivial approaches like the physical edge localization at a threshold of 50 % of the intensity level (˜FWHM) will almost always lead to significant deviations. More advanced approaches employ a model-based measurement evaluation based on rigorous simulations of the optical image. These require a complete characterization of the optical imaging system (illumination and imaging parameters, and related aberrations) and the sample (geometrical dimensions and optical constants). In this contribution we report on significant improvements of this model-based approach, which employs the entire intensity profile of the measured structure as the target function in a least-squares optimization process and not only two threshold values for the opposing edges. The so-called Bayesian Target Vector Optimization (BTVO) is used to iteratively fit the model’s simulated intensity distribution to the measured profile. The BTVO is included in the optimization toolkit of the JCMsuite (FEM; JCMwave GmbH), which is also used to simulate the optical images. Comparisons with different optimizations schemes indicated that BTVO algorithm converges significantly faster for computationally models. Firstly, this model-based approach has been successfully demonstrated on test samples provided by the Hochschule Aalen. In a second step we applied this method to existing measurements performed with a high NA UV-transmitted light microscope on high-quality photomasks which were originally designed for an international linewidth measurement comparison. The relevant features are single lines, grooves, and line gratings on a chrome-on-glass photomask. The CD is varying here from 0.1 μm to 1 μm. The geometrical and optical parameters of the sample, such as refractive indices and edge angles are well documented. The fits of a measurement profiles agree well with all previously estimated data. Fig. 1 shows as an example the result for a nominal 1 μm wide line Finally, we performed new measurements on this photomask using another UV-microscope based on optical components of a commercial mask metrology tool [3] integrated. in a custom setup [4]. The microscope uses a reflected light configuration with an adjustable illumination NA and different objectives (NA of 0.55 or 0.9) and exhibits a magnification of 200. These measurements have been evaluated and compared to already published and so far, unpublished results obtained with PTB’s metrological CD-SEM, CD-AFM and the CD-UV-measurement system. |
Zitierung
Krüger, J., Bergmann, D., Köning, R., Bodermann, B., Eder, C., Manley, P., Schneider, P.-I., & Zschiedrich, L. (2023). Enhancement of an on-going photomask CD-comparison by a new approach for model-based optical measurements. NanoScale, Helsinki, 10-12, October, 2023, Finland.