Ellipsometer is an optical measuring instrument used to detect thin film thickness, optical constants, and material microstructure.

Selection guide:

1. Determine the spectral range based on the material properties studied or tested, and further select an ellipsometer suitable for the light source. For transparent materials, consider the refractive index spectral region of concern; For short wave absorption and long wave transparent materials, if we are concerned about the refractive index and film thickness in the absorption region, we can extend it to the infrared transparent region to first determine the film thickness, and then solve for the refractive index.

The ideal light source for a light source ellipsometer is a stable intensity, with an approximate constant output across the entire wavelength range from ultraviolet to near-infrared. Currently, helium or Hg are mostly used. Helium lamps are reasonable, but they have weaker intensity at UV (below 260nm) and strong atomic radiation lines at 880-1010nm. Laser is also used as a light source (HeNe) for monochromatic ellipsometry measurement.

2. Selection of incident angle method. Multi angle measurement increases reliability, but it is not always necessary. Multi angle is suitable for the following situations: multi-layer film structures, absorption films, anisotropic films, films with optical constants distributed along thickness gradients, etc

3. Consider measurement accuracy and severity. Instrument repeatability is defined as the comparison of the results of multiple measurements by an instrument, which is relatively easy to define and compare. Generally, when measuring accuracy, air is used as a standard sample (there are no other ideal standard samples).

4. Comparative analysis software. Elliptical measurement is a non direct measurement mode, and data needs to be fitted and analyzed, so the quality of the analysis software will directly affect the analysis results.