Method for In-Situ Determination of Material Composition of Optically Thin Layers, Arrangements for Carrying Out the Method and Applications of the Method

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This patent describes a method and arrangement for the real-time, in-situ determination of the material composition of optically thin layers that are deposited on a substrate from the vapor phase (e.g., during thin-film manufacturing). Unlike existing methods that require smooth surfaces, reference measurements, or are only suitable for qualitative control, this invention uses spatially resolved optical detection (such as a CCD camera) of the reflection intensities of incoherent light of at least three different wavelengths during deposition. These reflection measurements are processed using an optical layer model based on electromagnetic field theory, allowing direct quantitative calculation of the layer’s thickness, refractive index, and absorption coefficient. From these parameters, the actual material composition of the thin film can be determined in real time, enabling advanced process monitoring and control.

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• Real-time quality and composition monitoring during the production of thin-film solar cells and semiconductor devices.
• In-situ process control of physical vapor deposition (PVD) or chemical vapor deposition (CVD) of multilayer stacks or complex materials.
• Manufacturing of high-efficiency semiconductor or photovoltaic layers where precise composition is critical.
• Production of optical coatings, thin-film transistors, or sensors requiring exact control over layer properties.
• Layer-by-layer monitoring of multi-stack thin films for display technologies or advanced electronics.
• Research and development labs needing analytical control over evaporation techniques for new material discovery.

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• Provides true quantitative, not just qualitative, in-situ monitoring of material composition and thickness for thin films.
• Works with both smooth and rough surfaces and does not require separate reference or normalization steps, simplifying integration into manufacturing.
• Self-referencing method increases robustness against environmental disturbances and fluctuations in the light source.
• Enables precise closed-loop process control, leading to higher repeatability and reproducibility in thin-film manufacturing.
• Adapts to continuous and sequential deposition processes, supporting advanced manufacturing flows such as roll-to-roll processing.
• Can be extended to monitor temperature and stoichiometry, supporting full process and quality control during deposition.

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Patent Abstract

Known methods are based on the measurement of the total reflection and analyze reflections of optical radiation in the case of smooth surfaces. Therefore, they require a normalization by measurement of the reference light or other measurement of the refractive indices. As a result, they cannot be used universally; in particular they cannot be used for process control of evaporation processes. The control methods known in this field operate only qualitatively on the basis of specific characteristics in the production process. For genuine quantative regulation, however, it is essential that the components to be regulated (optical layer parameter) are also made measurable. The method according to the invention directly determines the material composition of optically thin layers and is based on an optical layer model that was derived from electromagnetic conduction theory with field resistances. The deposited layer is irradiated with preferably incoherent spectral light, preferably from a white light source, and the reflection intensities outside total reflection are detected by a spatially resolving optical detector, preferably CCD, and fed into the layer model. The characteristic functions of the layer model are fitted to the real process values and serve for numerically ascertaining the optical layer parameters from which the specific material composition can be derived.