XAFS atomistic insight of the oxygen gettering in Ti/HfO2 based OxRRAM

Hafnia-based resistive memories technology has come to maturation and acceded to the market of nonvolatile memories. Nevertheless, the physical mechanisms involved in resistive switching are not yet fully understood and the numerous ab initio simulations studies have few many atomic-scale experimental counterparts. In this study we investigate the oxygen migration mechanism from an amorphous HfO2 layer to the Ti cap layer at a local scale before and after a thermal treatment. X-ray absorption spectroscopy at the Ti K edge and Hf L(III )edge has been performed on samples as-deposited and annealed in Ar at 400 degrees C to mimic the back-end-of-line thermal budget (BEOL) of CMOS technology. The short-range Ti and Hf environments have been determined, showing that annealing promotes the migration of O from HfO2 to Ti, the amount of which is quantified. This provokes an expansion and an increase of atomic disorder in the Ti lattice. The nature of the oxygen gettering mechanism by the Ti metal is understood by comparing samples with increasing Ti-capping thickness. We show that the Ti getter effect has to be activated by thermal treatment and that the O diffusion takes place in a region of a few nanometers close to the Ti/HfO2 interface. Therefore, the thermal budget history and the Ti cap-layer thickness determine the oxygen vacancy content in the HfO2 layer, which in turn controls the electrical properties, especially the forming operation

Couches minces de grenat substitué déposées par le procédé pyrosol pour l'enregistrement magnéto-optique

For magneto-optic memories application BiDyGaIG thin films were grown on glass substrates by an aerosol chemical vapor deposition process. After annealing the films behave a non textured polycrystalline garnet phase. The Faraday hysteresis loops measured at λ ࣃ 633nm, exhibited a good squareness with a coercive field higher than 1000Œ and a Faraday rotation higher than 2°/µm. By static recording it has been possible to write small domains of 2 to 15µm.De par leurs propriétés magnéto-optiques et leur très bonne résistance à la corrosion les couches minces de grenat substitué (BiDy)3 (FeGa)5 O12 sont candidates potentielles pour les média magnéto-optiques de deuxième génération. Pour réaliser de telles couches nous développons dans notre laboratoire un procédé chimique peu coûteux, le procédé pyrosol, qui est basé sur la pyrolyse d'un aérosol contenant des précurseurs organométalliques. Les couches, d'une épaisseur de 2000 Å à 5000 Å déposées sur des substrats de verre à 515°C, sont parfaitement transparentes et adhérentes, et font apparaître après recuit en diffraction des rayons X une structure polycristalline non orientée. Un taux de substitution de 2 bismuth par unité de formule permet d'obtenir un effet Faraday supérieur à 2°/µm pour une longueur d'onde de 632,8 nm et des tests d'écriture thermomagnétique par laser ont permis d'inscrire des domaines d'un diamètre inférieur à 2 µm

Deposition by an aerosol assisted MOCVD process of Eu or Er doped Y2O3-P2O5 thin films

The deposition of Er or Eu doped Y2O3-P2O5 thin films by an aerosol assisted MO-CVD atmospheric process is studied. 0.1 to 0.5 µm thick films were obtained on glass substrates in the temperature range 400°C-580°C. The rare earth luminescence is activated by post annealing. The properties of the films were discussed in function of the P2O5 content. For high annealing post-deposition treatments the films with less than 15 Mol % P2O5 tended to crystallise in the yttria phase. The YPO4 phase appeared around 50 Mol % P2O5 . Between these concentration limits the films appeared as a disordered composite Y-P-O phase and exhibited wide luminescence bands

Erbium doped yttria thin films deposited by injection CVD

The deposition of Er doped Y2O3 thin films by a pulsed injection assisted MO-CVD process is studied. Well crystallised Er : Y2O3 films with a columnar growth structure were deposited between 600°C and 900°C. In some cases a monoclinic phase was obtained with the classical yttria cubic phase. The preferential crystalline orientation for the cubic phase ( [111] or [100] ) depended on the deposition temperature and on the oxygen content of the carrier gas. Because the Er and Y precursors are chemically similar (Er or Y tetramethylheptanedionate), the composition of the deposited films are closed to the composition of the solution. The Er luminescence was obtained for all the as deposited samples. The green and Infrared4I13/2 → 4I15/2 transition were observed. The lifetime of 4I13/2 level increased with the deposition temperature. The lifetime of the 4I13/2 level decreased with the erbium content due to up conversion effect. A lifetime of 7.5ms, closed to the bulk value, was obtained at low erbium concentration

Thin Films of Zirconia-Phosphate Glasses Deposited by an Aerosol CVD Process

The polycrystalline state of the ZrO2 films was an disadvantage for some specific protective coating applications. To resolve this fact we proposed to obtain an amorphous thin film by addition of P2O5, which will act as glass formator agent. With an aerosol CVD process by using zirconium acetylacetonate and triphenyl phosphate dissolved in a mixture of acetylacetone and benzyl alcohol, we achieved to deposit mixed P2O5-ZrO2 films between 480°C and 600°C. The P2O5 content varied from 0% up to 60%. By measuring systematically the composition of the film we have noticed the influence on the composition of the films, on the one hand of the hygrometric degree of the carrier gas and on the other hand of the temperature used for the dissolution of the organometallic precursors in the solvent. The highest the dissolution temperature was, the most the phosphorus content was. After an annealing at 500°C during one hour, the films exhibited by Xray diffraction analysis an amorphous structure and a very good transparency. More over the evolution of the I.R. spectra between 1200 cm-1 and 900 cm-1 and arround 400 cm-l are discussed in function of the composition of the films

NEW TECHNIQUE FOR THE DEPOSITION OF HIGH Tc SUPERCONDUCTING FILMS

Des couches minces supraconductrices de composition YBa2Cu3O7-x ont été obtenues par une nouvelle technique de dépôt, basée sur la pyrolyse d'un aérosol pulvérisé par voie ultrasonore et contenant les précurseurs Y-Ba-Cu. Cette technique conduit à un très bon aspect de surface des films et permet de contrôler précisément leur épaisseur. Les couches d'à peu près 0.2 à 6 µm d'épaisseur ont été recuites à l'air à 500°C, chauffées sous oxygène à des températures de 900 à 960°C, puis refroidies lentement à température ambiante sous oxygène. Cette méthode conduit à des couches bien cristallisées, présentant une bonne homogénéité de taille de grain et une texture dans la direction 001 dépendant des conditions de traitement thermique. Des céramiques et monocristaux de SrTiO3, YSZ ou MgO ont été utilisés comme substrats. Dans cet article on discute l'influence des conditions expérimentales sur la microstructure, la morphologie et les propriétés supraconductrices des films.Thin films of YBa2Cu3O7-x superconductors have been prepared using a new deposition technique based on the pyrolysis of an ultrasonic generated aerosol containing the Y-Ba-Cu precursors. This technique leads to a very good quality of the film surface and allows to control accurately the film thickness. Films of about 0.2 to 6 µm in thickness have been annealed in air at 500°C, heated under oxygen at temperatures ranging from 900 to 960°C and then slowly cooled in oxygen to room temperature. This method leads to well crystallized YBa2Cu3O7-x films with a good grain size homogeneity and a texture in the 001 direction depending on the heat treatment conditions. SrTiO3, YSZ or MgO single crystals and ceramics have been used as substrates. In this paper we discuss the influence of the experimental conditions on the microstructure, morphology and superconducting properties of the films

THIN FILM OF CERAMIC OXIDES BY MODIFIED CVD

Nous décrivons un procédé de dépôt utilisant la pyrolyse d'un aérosol généré par ultrasons (procédé Pyrosol). La réaction chimique sur le substrat chauffé est de type CVD. Nous avons étudié les conditions expérimentales de dépôt de zircone stabilisée à l'oxyde d'Yttrium, en vue de la réalisation de microcapteurs de gaz. Nous obtenons directement la phase cubique de la zircone stabilisée. Comme application en tant que média pour l'enregistrement magnéto-optique nous avons obtenu des couches de Y3Fe5O12 non orientées pour des dépôts sur quartz et des couches épitaxiées pour des dépôts sur des substrats monocristallins de GGG.We describe a deposition process which uses the pyrolysis of an aerosol produced by ultrasonic spraying (Pyrosol process). The chemical reaction on the heated substrate corresponds to CVD. Experimental deposition conditions of yttria stabilized zirconia have been studied with the aim of realizing microionic gas sensors. We obtain directly the stabilized cubic phase. For magneto-optical information storage or magneto-optical display devices we have deposited Y3Fe5O12 garnet thin films. Good quality thin layers were obtained, not textured on quartz substrates and epitaxialy grown on GGG substrates