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Study of materials interactions and electrochemical mechanisms at the interfaces of electrodes of a memory stack based on metal oxides

Abstract : This thesis focuses on the understanding of forming mechanisms in oxide-based conductive bridge memories (CBRAM), based on metallic oxides. For this purpose, we compared the memory stack to an electrochemical cell at nanometer scale and consider that the main mechanisms occurring in the memory rely on electrochemical effects. We started our studies from a reference couple CuxTey/Oxide, analyzed by HAXPES and ToF-SIMS before and after electro-forming, in order to observe the diffusions and the modifications of the chemical environment occurring during forming. Then, the ion source layer based on CuxTey alloy and the dielectric (Ta2O5, GdOx or Al2O3) were sequentially modified and results of their analyses were compared to the reference stack, in order to understand the role of each layer and chemical elements present in the memory stack.We evidenced that the properties of the dielectric, such as the strength of its oxygen-metal bonds, its hygroscopicity or the eventual presence of defects such as oxygen vacancies, can promote a given memory behavior from OXRAM to CBRAM or hybrid OXRAM/CBRAM behavior. Moreover, when copper diffuses during the forming, an oxygen counter diffusion also takes place in the dielectric. Also, the presence of tellurium in the ion source layer is required to reset the memory as it enables the dissolution of the copper filament in the ion source layer. We also show that germanium amorphizes the CuxTeyGez alloy, thus enables its integration, and protects it from oxidation. Moreover, it is possible to substitute germanium by zirconium resulting in the dielectric reduction, which eases the forming.
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https://tel.archives-ouvertes.fr/tel-01891068
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Submitted on : Tuesday, October 9, 2018 - 11:29:11 AM
Last modification on : Wednesday, October 14, 2020 - 4:19:04 AM
Long-term archiving on: : Thursday, January 10, 2019 - 2:08:01 PM

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Aurélie Marty. Study of materials interactions and electrochemical mechanisms at the interfaces of electrodes of a memory stack based on metal oxides. Micro and nanotechnologies/Microelectronics. Université Grenoble Alpes, 2018. English. ⟨NNT : 2018GREAT038⟩. ⟨tel-01891068⟩

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