Global Fitting of thick SiO2 film

This fitting method is useful 1) to avoid local MSE minimum, 2) for complicated models with many parameters, and 3) for thick film.

1. Open the model window.

• This example is the Cauchy model window.

2. Check the parameters, which you want to fit, in the fit boxes. Click "OK".

• Warning: DO NOT check n and k in the "Opt Const Fit" box.

3. Click on the "Fit" window to popup the menu.

4. Choose "Edit Parms" to open the "Edit Fit Parameters" dialog box.

5. Highlight the parameter in the parameter box, using left-click of the mouse.

• This example shows "Thick.1".

6. Set minimum, and click the "Change Parm Coupling" button, so that the display in the box is changed.

7. Set maximum, and click the "Change Parm Coupling" button, so that the display in the box is changed.

8. Set the number of Global guesses, and click the "Change Parm Coupling" button, so that the display in the box is changed.

1. Use ~50 guesses per 1 micron thickness range
2. Use ~10-20 guesses for Index range of 1 (An)
3. Use ~ 5 guesses for Non-ideality
4. Avoid global fitting dispersion (Bn, Cn)
5. Keep total number of guesses under 5000
6. Reduce Wavelengths and Angles to improve speed.
7. NOTE: parameter limits will remain for Normal Fit unless adjusted.

9. Click the "Global Fit" button to start fitting.

10. The result will be shown in the "Fit" window.