Berlin 2015 – scientific programme

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DS: Fachverband Dünne Schichten

DS 2: Thin Film Characterisation I: Structure Analysis and Composition

DS 2.3: Talk

Monday, March 16, 2015, 10:00–10:15, H 0111

Model-based thin film characterization by confocal and total interference contrast microscopy — •Matthias Vaupel — Carl Zeiss Microscopy GmbH, 37081 Göttingen, Germany

It is investigated how optical models improve the accuracy of thickness measurements of a layer stack. Starting with an optical model for ellipsometry on thin films, we derive optical models for total interference contrast (TIC) and confocal microscopy. The confocal model of incoherent superposition of reflections is tested in case of one thin transparent passivation layer on an electronic chip. The model parameters are obtained by a cross-section with FIB-SEM. Thickness and refractive index of the layer are obtained from the confocal measurement by means of the optical model. TIC measures the phase difference of two adjacent spots on a sample. Consequently the phase difference is independent of vertical sample vibration. This allows for pm-vertical resolution of film thickness. As an example the TIC-optical model is applied to obtain the thickness profile of mono- and bilayers of graphene[1] out of the phase profile measured by means of a micrograph recorded in less than 100 ms. The advantages and restrictions of TIC in comparison to AFM, imaging ellipsometry, Mirau-type white light interferometry are discussed.

[1] M. Vaupel et al., Topography, complex refractive index, and conductivity of graphene layers measured by correlation of optical interference contrast, atomic force, and back scattered electron microscopy, J.Appl.Phys. 114, 183107 (2013)