Wafer Charakterisierung

One challenge in Terahertz spectroscopy is the independent determination of refractive index and geometrical thickness of a given sample. This can be solved for semiconductor wafers by making use of the etalon effect induced by the plane parallel surfaces:

In a first step the frequency dependent transmission is measured. This could be done by tuning the beat frequency emitted by a dual mode Y-Laser [Link zu Y-Laser]. Extracting the envelope and performing a mean square error optimization to the theoretical etalon transmission will then result in n and d without any further sample knowledge.


  • N. Surkamp u. a., „Current tuned slotted Y‐branch laser for wafer thickness measurements with THz radiation“, Electronics letters, Bd. 57, Nr. 24, S. 936–938, Sep. 2021, doi: 10.1049/ell2.12314.



Ruhr-Universität Bochum
Fakultät für Elektrotechnik und Informationstechnik
Lehrstuhl für Photonik und Terahertztechnologie
Postfach ID 16
Universitätsstraße 150
D-44801 Bochum


Raum: ID 04/327
Telefon: (+49) (0) 234 32 - 23051
Fax: (+49) (0) 234 32 - 14167 
E-Mail: ptt+office(at)rub.de
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Prof. Dr.-Ing. Martin Hofmann
Raum: ID 04/329
Te­le­fon: (+49) (0) 234 32 - 22259
Fax: (+49) (0) 234 32 - 14167
E-Mail: martin.hofmann(at)rub.de

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