Elaboration de grilles à base de matériau metallique pour des filières CMOS avancées

Ce travail de thèse s'est concentré sur la sélection, la mise en œuvre et la caractérisation de matériaux en films minces pour une utilisation en tant que grille métallique dans les transistors MOS de génération sub-45nm. Dans un premier temps, une analyse bibliographique approfondie a permis de préciser les paramètres physico-chimiques essentiels à maîtriser pour obtenir une électrode de grille adaptée c'est à dire un matériau dont le travail de sortie puisse être adapté pour servir soit d'électrode n ou p. Cette synthèse analyse détaillée a conduit au choix du nitrure de titane TiN, déposé à partir d'un précurseur organométallique par deux méthodes (MOCVD et MOALD). Des essais de modulation du travail de sortie ont été réalisés en utilisant des traitements pendant ou après le dépôt : Pour tirer partie de l'anisotropie du travail de sortie du TiN, un traitement plasma qui permet d'adapter l'orientation préférentielle des nano cristallites dans les films a été étudié. Cependant, lorsqu'il est appliqué sur l'interface TiN/diélectrique, le diélectrique s'en retrouve dégradé. Pour tirer partie de l'influence de la nature chimique du TiN sur le travail de sortie, l'insertion de silicium dans le matériau de grille a été étudiée. L'incorporation maîtrisée de Si dans la couche mince de TiN permet de contrôler de manière précise le travail de sortie.Les diverses couches obtenues ont été caractérisées physiquement (composition, nature des liaisons chimiques, morphologie, texture ...) et électriquement (travail de sortie, impact sur les diélectriques sous-jacents). L'évolution de ces propriétés avec la température est étudiée.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Encapsulation Effects on Ge‐Rich GeSbTe Phase‐Change Materials at High Temperature

published by Wiley-VCH GmbHPhys. Status Solidi RRL2024, 2300448https://onlinelibrary.wiley.com/doi/epdf/10.1002/pssr.202300448International audienceGe‐rich GeSbTe chalcogenide alloys have gained significant attention in the field of phase‐change materials due to their remarkable thermal stability and thus their suitability for integration in nonvolatile memories targeting embedded automotive applications. Herein, the effects of different encapsulating materials on the evolution and on the crystallization kinetic of N‐doped Ge‐rich GeSbTe films are focused on. These films are annealed with temperatures compatible with the back‐end‐of‐line of the complementary metal‐oxide‐semiconductor (CMOS) fabrication. First, it shows how the encapsulation layer thickness should be tuned in order to protect the layer from oxidation and at the same time to avoid delamination phenomena. TaN, C, TiN, SiC, and SiN used as encapsulating layers are compared. The segregation and crystallization of Ge‐rich GeSbTe alloys appear more homogeneous in the case of C, TiN, and SiC. On the contrary, the effects of an interfacial heterogeneous nucleation in the case of TaN and SiN are observed. It results in a different final morphology of the chalcogenide layer after annealing depending on the encapsulation, with different grain sizes and kinetic of phase separation

Electroless deposition of NiMoPB : electrical performances and material properties

International audienceElectroless deposited Co-based caps are convicing alternatives to standard SiC(N) barriers for the 45 nm node and beyond to improve electromigration resistance and limit the dielectric constant of the structures. In this work, growth kinetics, process selectivity, microstructure and composition of an alternative self-initiated NiMoPB cap are reported for 300 mm fabrication. This process is very selective, and does not modify the electrical performances of the structures. The film presents very promising barrier properties against copper diffusion, due to a high quantity of phosphorus and refractory metal in the fihn

Phase-change materials for non-volatile memory devices: from technological challenges to materials science issues

International audienceChalcogenide phase-change materials (PCMs), such as Ge-Sb-Te alloys, have shown outstanding properties, which has led to their successful use for a long time in optical memories (DVDs) and, recently, in non-volatile resistive memories. The latter, known as PCM memories or phase-change random access memories (PCRAMs), are the most promising candidates among emerging non-volatile memory (NVM) technologies to replace the current FLASH memories at CMOS technology nodes under 28 nm. Chalcogenide PCMs exhibit fast and reversible phase transformations between crystalline and amorphous states with very different transport and optical properties leading to a unique set of features for PCRAMs, such as fast programming, good cyclability, high scalability, multi-level storage capability, and good data retention. Nevertheless, PCM memory technology has to overcome several challenges to definitively invade the NVM market. In this review paper, we examine the main technological challenges that PCM memory technology must face and we illustrate how new memory architecture, innovative deposition methods, and PCM composition optimization can contribute to further improvements of this technology. In particular, we examine how to lower the programming currents and increase data retention. Scaling down PCM memories for large-scale integration means the incorporation of the PCM into more and more confined structures and raises materials science issues in order to understand interface and size effects on crystallization. Other materials science issues are related to the stability and ageing of the amorphous state of PCMs. The stability of the amorphous phase, which determines data retention in memory devices, can be increased by doping the PCM. Ageing of the amorphous phase leads to a large increase of the resistivity with time (resistance drift), which has up to now hindered the development of ultra-high multi-level storage devices. A review of the current understanding of all these issues is provided from a materials science point of view