The analysis of Ellipsometer spectrograph
Ellipsometery in fact, shaped based on Fresnel's equations in reflection or transmission of polarized light beam from interface of homogeneous multilayer materials. In topic of optics, we have remembered that, when the light beam collides to material, a part of it is reflected but another part of it, the first penetrate into the material and then is reflected.
By measuring the difference between these two reflections, the thickness is determined. Also, due to the fact that, in this process, the polarization of reflected light from the sample is changed, they use of this change to calculate the refractive index and absorption index of layers. As shown in Figure 1, the light after leaving the light source, initially entered into a polarizer and polarize linearly, then this light is entered to compensator to polarized elliptically (or circularly), and then the output light beam collides to the sample and the light is reflected (in some systems, the transmitted light beam also is analyzed).
Figure 1: Right. Schematic view of the used layout in the process of ellipsometery. Left. Schematic view of the physics of the used process, in an ellipsometer spectrograph analysis.
Behavior changes in the passing and returned light, from the sample by detector, determines the properties of the sample. It should be noted that the optical constants and the thickness of thin layers are not measured directly, but are determined based on the change in polarization, in terms of Ψ and Δ. Two Ψ and Δ parameters represents the change in the polarization state of returned light from the sample. In Figure 2, come an example of the application of this system, ie the thickness measuring and stoichiometry.
Figure 2: The thickness and stoichiometry calculation of multilayers, with ellipsometer spectrograph system.
Also in Figure 3, for example, has been shown the measured optical constants n and k, for ZnO, SnO2 and c-Siμ, which have been calculated by the ellipsometer spectrograph system. In Figure 4 is shown, the real view of an ellipsometer spectrograph system.
Figure 3: The measured optical constants n and k, for ZnO, SnO2 and c-Siμ, which are calculated by the ellipsometery spectrograph system.
Figure 4: The real view of a ellipsometer spectrograph.
Ellipsometer spectrograph is an ideal technique, for determining physical and optical properties in a wide range of thin-film materials. This technique without has contact with the sample or cause damage is used with very high accuracy in determining the characterization of materials, especially in thin film technology. In addition, it is also used in the semiconductor manufacturing technology, biological materials and substrates, solar cells, and manufacture of medical equipment. In thin film fields, this technique is used to thickness, roughness, percentage of alloy measuring, and determining the optical properties of thin films, such as refractive index and absorption coefficient, as well as determining the stoichiometry of layers in periodic multilayer .