Non-destructive thin film analysis
In the extremely dynamic field of semiconductor technology, research and development is one of the key features for long lasting success, as well as an effective quality management. For both tasks, innovative measuring systems give your company a head start in this highly competitive market. In thin-film analysis, an elegant and non-destructive method is ellipsometry.
This is a well-established measurement technique to determine the refractive index and the thickness of thin films. This technique is non-invasive, as the change in polarisation of incident and reflected light at the boundaries of thin films is analysed. One of the most important characteristics in crystalline film systems is the material composition, which can be deduced from the refractive index and the thickness. In the rising market of mid-infrared applications, MIRell Photonics GmbH is the world’s first vendor for Ellipsometer with a laser light source.
How does ellipsometry work?
Light with well-defined polarisation is incident at a specified angle upon the sample surface. At the interfaces of layer boundaries, light will be partially reflected and the polarisation will change depending on the material. This change in polarisation will be detected and analysed by software to make a physically correct model of the measured film system.
What is the meaning of the measured data?
The direct results of the calculated model are the film thickness and the refractive index for every film in the system. The refractive index characterises the behaviour of light in matter. It is based on material parameters like the concentration of donors or the material composition in semiconductor devices. The knowledge of these parameters is crucial for all photonic applications.
Diagram of the measuring process with rotating analyser. Adapted from M. Neshat and N.P. Armitage: "Developments in THz range ellipsometry". https://arxiv.org/pdf/1305.3127.pdf (May 2013).
Exemplary measurement results for the evolution of thickness during the growth process. From S.I. Chikichev and A.V. Vasev: "Condensation and sublimation of thin amorphous arsenic films studied by ellipsometry". https://arxiv.org/ftp/cond-mat/papers/0402/0402592.pdf.