Ellipsometry

Spectroscopic Ellipsometry (SE) is a contact-free, nondestructive method for the characterization of the dielectric and optical properties (refractive index, absorption coefficient, anisotropy) and structural properties (roughness, thickness and intermix of layers) in the thickness range of < 1 nm to few µm.

Ellipsometry is an accurate technique for calculating materials’ parameters, including complex refractive index or dielectric function. The samples are measured in reflection and the information is given based on the change of the polarization of the reflected light. Standard SE methods measure the Fresnel reflection coefficients as a function of wavelength only. While variable angle SE (VASE) measures the sample’s coefficients in s- and p-polarized light as a function of wavelength and angle of incidence. In addition, thanks to the vertical configuration it can be measured also the sample transmittance to be coupled with the ellipsometric data during fitting. All measurements can be done with a motor stage on a 4x4cm area.

Depending on the spectral coverage of a VASE instrument, dielectrics, semiconductors, and metals can be characterized. Typical applications are the characterization of manufactured thin films used in devices. Sample size can vary from 1x1cm up to a 6” wafer.

Finally, the measurements, thanks to a closed cell, can be performed in an N₂ environment in the case of air-sensitive samples and or by varying the temperature in the range -90°C up to 600°C to identify phase changes.