I used Semilab ellipsometer to measure a film(mostly silicon) from evaporation. it measured with 4 different angles. The model has a good fit with 75 65 and 60 measurement while the 70 is not good. So during fitting, I removed the 70 measurement to increase overall fitting accuracy.
I am not sure if this is against the rule of the ellipsometry measurement (keep the good fitting angle and remove the bad fitting angle). Or which angle of measurement provides the best result that is trustworthy for the film.
Thanks a lot.
The best model will fit all angles simultaneously. Either you can increase the resolution of your measurement or include different parameters in your measurement so as to capture more raw data and to be sure you get as much possible information that is available.
Assuming it is an isotropic thin film over an isotropic substrate and has no depolarisation, you can try to add different oscillators like Gaussian or Lorentzian or also try for the Cauchy equation over a transparent region with an Urbach tail to model for absorption to see how the fit goes. You'll probably have an oxide layer on the top which should be included in the model. If you have thickness measurement from AFM or any other Instrument, then that will also help. Drude can be added to model low-energy behaviour. I have not worked with Semilab so do not know what features are available. You can check resources at the JA Wollam ellipsometer website and also book by Hiroyuki Fujiwara. Hope this helps.
Mukul Bhatnagar
Hello Mukul, the measurement for wavelength over 1000 nm (1000-2000nm) is always noisy, which affects the fitting quality. So during fitting, can I narrow the range from 400 nm to 1000 nm? And what specific information does measurement over 1000 nm -2000 nm represent?
Thanks a lot!
Hi, silicon should be transparent in the region from 1100 nm onwards so probably Cauchy equation can be employed. You can always narrow down or select a specific range of interest where the quality of data is good.
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