Spectroscopic vs. single wavelength ellipsometry

[lcr2139]

Hello, I know that spectroscopic ellipsometry (SE) is more accurate than single-wavelength ellipsometry (SWE), but I would like to know how to create a dispersion model using SWE instead of SE.

SE sweeps over wavelength, measures reflectivity vs. wavelength, and gives a variety of optical constants, but SWE only gives out thickness and refractive index. SWE's are made with lasers and can only measure at one wavelength. I know that having a spectrum of wavelengths can give more accurate measures than SWE, but can we make a dispersion model out of measuring only the thickness and refractive index?

 

[AndyW]

Hello there,

Thank you for your question. Spectroscopic ellipsometry (SE) is indeed more accurate than single-wavelength ellipsometry (SWE) due to its ability to measure over a range of wavelengths and provide a variety of optical constants. However, it is possible to create a dispersion model using SWE by using a few additional techniques.

Firstly, it is important to note that SWE measurements are typically taken at multiple angles of incidence. This allows for the calculation of the ellipsometric parameters, which can then be used to determine the thickness and refractive index of the sample. By varying the angle of incidence, it is possible to obtain information about how the refractive index changes with wavelength.

Additionally, the use of multiple SWE measurements at different wavelengths can also provide information about the dispersion of the refractive index. By measuring the thickness and refractive index at different wavelengths, it is possible to create a dispersion curve and fit it to a suitable model, such as the Cauchy or Sellmeier equations.

Furthermore, other techniques such as variable-angle spectroscopic ellipsometry (VASE) can also be used to obtain dispersion information from SWE measurements. VASE involves taking multiple SWE measurements at different angles of incidence and wavelengths, and then fitting the data to a model to obtain a dispersion curve.

In summary, while SE may provide more accurate dispersion information, it is possible to create a dispersion model using SWE by combining multiple measurements at different angles of incidence and wavelengths, and utilizing additional techniques such as VASE. I hope this helps answer your question. Let me know if you have any further queries.