Conventional light sources have a penetration depth of a few nanometers in metal layers and cannot be used for spectroscopic ellipsometry purpose to measure layer thicknesses of a few 100 nanometres.
Using a laser diode is the best. There are many options to choose different wavelengths. They are powerful and low cost.
Hello Ernst,
I think there is no chance to measure metal layer thickness of a few 100 nm by ellipsometry in the spectral range where conventionnal instruments operate today that is from VUV to IR, whatever the source.
Hello Ernst,
I absolutely agree with Michel's answer, - it is impossible for typical SE to measure thick metal layers. The reason is physically simple - the so-called "skin-effect", i.e., the phenomenon where electromagnetic field decay rapidly with depth inside a good conductor. If we calculate the skin depth for the light from UV (~8x10^14 Hz) to IR (~4x10^14 Hz) ranges in case of copper, we get the depth ~2.2-3.3 nm only. BTW, the skin effect is the reason why a person is safe inside a metal car during a thunderstorm (and not a Faraday cage which works with static electricity). The formulas for the skin effect can be easily found in many textbooks or in Wikipedia, for instance.
Hello. Metal layer thickness (above optical penetration depth of light) could be measured non-destructively by so-called SAW (Surface Acoustic Wave) technique. Please, find attached an article about it.
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