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Caractérisation et contrôle industriel des contraintes locales en microélectronique : applications aux transistors de technologie 20 nm

Abstract : For many years, characterization techniques have been used in the microelectronic industry in order to probe and analyze integrated components. Nowadays the critical downscaling of transistors and implementation of new materials and methods, such as silicon-germanium (SiGe) and strain engineering, induce the necessity of developing innovative metrology in order to monitor the fabrication processes at each step. In this context, there is a need for non-destructive and fast strain characterization techniques, capable of in-line analysis of nano-structures. Within that framework, the capabilities of High Resolution X-Ray Diffraction (HRXRD) and Raman spectroscopy for strain measurements is evaluated and a methodology tailored to in-line metrology constraints is proposed.Industrial HRXRD equipment, developed for an in-line strain metrology have demonstrated their ability to measure strain in SiGe thin films of only a few nanometers thick, with a great sensitivity (< 10-4). Nonetheless, when it comes to advanced structures, such as planar transistors, the strain field complexity requires the measurement and the thorough analysis of Reciprocal Space Mappings (RSM). In this study, we demonstrate the interest and capability of RSM for the characterization of strained structures for gratings of pMOS transistors. A reverse method that consists in using a strain field model to reproduce the measured RSMs is used. The benefit of using different mechanical models is explored and a very good agreement between experimental and simulated RSM’s is established. Strain field extracted by this method is successfully correlated to the one measured by Dark-Field Electron Holography (DFEH) technique, emphasizing the capability of HRXRD for pMOS strain field investigation.Alongside, µ-Raman spectroscopy was also identified to be a promising candidate for the industry, due to a sub-micrometers spatial resolution and a low detection threshold. It enables to determine simultaneously the strain state and the average composition of SiGe thin films down to the nanometer scale. Thereby, µ-Raman reveals that a condensation process, critical to create a strained SiGe channel for advanced transistor technology, induces a germanium composition inhomogeneity in the SiGe thin films. To go further, the spatial resolution of µ-Raman and Tip-enhanced Raman Spectroscopy (TERS) techniques is investigated by comparing the measurements with simulations, highlighting that there is still some way to go before fulfilling the demands of the microelectronics industry.Finally, a HRXRD methodology is developed in order to follow the strain field evolution all along process steps in a manufacturing environment. The main method uses a large library computed for a bunch of structures with varying geometries, germanium content and strain parameters. Then the measured RSMs are selectively matched to the simulated RSMs within the library, providing in a simple and a quick way a close corresponding geometry and strain field as an output, which could then be refined by iteration if necessary. Thanks to a homemade software (DXtract), that processes and simulates the RSMs, the whole procedure is automated and is capable to follow, detect and localize even the small strain variations induced by the manufacturing steps. In addition, all the results demonstrate that the procedure is compatible with industrial constraints, meaning fast, robust and easy to operate. This work is therefore a major step towards the use of RSM for in-line monitoring, which is undoubtedly a relevant technique for industrial strain metrology.
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Submitted on : Thursday, February 8, 2018 - 8:24:09 AM
Last modification on : Thursday, June 11, 2020 - 5:04:07 PM
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  • HAL Id : tel-01693673, version 1

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Aurèle Durand. Caractérisation et contrôle industriel des contraintes locales en microélectronique : applications aux transistors de technologie 20 nm. Science des matériaux [cond-mat.mtrl-sci]. Université Grenoble Alpes, 2016. Français. ⟨NNT : 2016GREAY081⟩. ⟨tel-01693673⟩

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