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Développement de nouvelles technologies de gravure : mise en évidence de la stochasticité du bombardement ionique lors de procédés plasma industriels

Abstract : The microelectronics industry is more and more challenged by the miniaturization of devices thus constantly constrained to develop new plasma etching technologies and to overcome limits imposed by CW plasma processes. Among, these new technologies, there are pulsed plasmas and the cycled etching process developed by Applied Materials. A characteristic of these processes is to work with very low flux of ions. However, a problem arises when the number of ions impacting the surface becomes too small (less than 1 ion/atomic site/second). Thus this work focuses on the study of the impact of the stochasticity of ion bombardment on the surface state in two etching processes. In a first part of our work, we studied the interaction between pulsed plasmas of chlorine and silicon. Similarly the effect of pulsed plasmas of HBr was also investigated. At a low duty cycle, a very high surface roughness was observed, unrelated to a micro-masking phenomenon. Under these experimental conditions, plasma diagnostics were carried out to measure the flux of energetic ions and the flux of neutrals. In this way, we highlighted that a very low flux of energetic ions and a high ratio neutrals/ions lead to high chemical reactivity. It results in the creation of a strong surface roughness. In a second part of our work, we studied the modification of SiN layers during the cyclic etching process using capacitive hydrogen plasma. After removal of the modified layer in remote plasma, we brought out the presence of a surface roughness at the top of the nitride spacer. Our parametric study of the surface state highlighted the correlation between the low fluence of hydrogen ions received by the material and the surface roughness. Thus, the stochasticity of ion bombardment implies an inhomogeneous modification of the SiN which is revealed by the remote plasma and amplified during the cycles. In this situation, an important surface roughness is generated. These results are consistent with simulation study in molecular dynamics. Therefore we demonstrated that the number of ions impacting on the surface (ion stochastic effect) appears as being a very limiting parameter in the pulsed plasma processes as well in some CCP processes.Key words: Microelectronics, etching processes, plasma, stochasticity, ions.
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Odile Mourey. Développement de nouvelles technologies de gravure : mise en évidence de la stochasticité du bombardement ionique lors de procédés plasma industriels. Micro et nanotechnologies/Microélectronique. Université Grenoble Alpes, 2017. Français. ⟨NNT : 2017GREAT027⟩. ⟨tel-02905449⟩

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