Elaboration et caractérisation de structures métal-isolant-métal à base de TiO2 déposé par Atomic Layer Deposition

The requirements for future dynamic random access memory (DRAM) capacitors are summarized in the International Technology Roadmap for Semiconductors. For sub-22 nm node, performances like equivalent oxide thickness (EOT) < 0.5 nm and leakage current density < 1.10-7 A/cm² at 0.8 V are required but are difficult to meet. Titanium dioxide (TiO2) is an attractive dielectric material for such application regarding its high dielectric constant (k). Depending on its growth conditions, TiO2 can be prepared in amorphous, anatase or rutile phase. From the structural point of view, it is generally preferred that TiO2 remains amorphous throughout a complete technological process to minimize leakage transport along grain boundaries. However, the rutile phase exhibits very high dielectric constant ranging from 90 to 170, depending on the lattice orientation. Due to this high dielectric constant, TiO2 rutile phase is considered as a promising material for capacitors in future generations of Dynamic Random Access Memories (DRAMs). A key issue is how to control the high leakage current of rutile phase while keeping the highest dielectric constant in order to get the best electrical performances. In this work, we investigate the growth of high dielectric constant rutile TiO2 films in Metal - Insulator - Metal (MIM) structures deposited on different substrates such as RuO2/Ru or Pt electrodes using ALD (Atomic Layer Deposition). A study of physico-chemical properties of TiO2 layer and influence of bottom electrodes on TiO2's crystalline structure is proposed. Different compositions of dielectrics are processed using flexibility of ALD deposition technique, including Al-doped TiO2 layers and pure TiO2 layers. Electrical properties in terms of leakage current or capacitance density of MIM structures embedding that kind of dielectrics and comparison between these MIM structures in terms of electrical performances is proposed in order to determine the best dielectric film composition to meet the requirements for next generation of DRAM capacitors.Les besoins de la microélectronique pour les condensateurs de type DRAM sont résumés dans la feuille de route ITRS (International Technology Roadmap for Semiconductors). Pour descendre en dessous du noeud technologique 22 nm, des performances électriques telles qu'une épaisseur d'oxyde équivalent (EOT) < 0.5 nm et un niveau de courant de fuite < 1.10-7 A/cm² à 0.8 V sont nécessaires. Ces performances sont difficiles à atteindre si l'on considère des oxydes standards largement utilisés tels que le SiO2, le Si3N4 ou l'Al2O3. Le dioxyde de Titane constitue un matériau diélectrique de choix pour ce type d'application si l'on considère sa forte constante diélectrique, la plus haute des oxydes binaires. Selon les conditions de croissance de la couche de TiO2, celle-ci peut se présenter sous forme amorphe ou posséder une structure cristalline appelé phase anatase ou phase rutile. Cette dernière présente une très forte constante diélectrique (90 à 170 selon l'orientation de la maille cristalline) et en fait un atout indéniable pour le développement de condensateur DRAM. Toutefois, cette phase rutile est aussi à l'origine d'un fort courant de fuite mesuré à partir des structures Métal - Isolant - Métal (MIM) associées. De ce fait, il est primordial de savoir contrôler ces courants de fuite tout en gardant la forte valeur de constante diélectrique de la phase rutile. Dans ce travail, nous proposons de travailler sur la croissance des couches minces de TiO2 intégrées dans des structures MIM et déposées sur des substrats différents tels que des électrodes de RuO2/Ru ou de Pt. La technique de dépôt employée pour les couches minces de TiO2 est la technique ALD pour son contrôle très précis de l'épaisseur déposée et sa souplesse d'utilisation pour ce type d'applications. Les propriétés physico-chimiques des couches de TiO2 et l'influence du substrat sur ces propriétés sont analysées. Des compositions différentes de diélectriques sont élaborées au moyen de la technique de dépôt par ALD et notamment des couches minces de TiO2 dopés à l'aluminium. Les propriétés électriques de ces couches sont étudiées afin de déterminer les performances électriques des structures MIM associées en termes de courant de fuite et de densité capacitive

Postnikov invariants of H-spaces

It is known that the order of all Postnikov k-invariants of an H-space of finite type is finite. This paper establishes the finiteness of the order of the k-invariants $k^{m+1}(X)$ of X in dimensions m ≤ 2n if X is an (n-1)-connected H-space which is not necessarily of finite type (n ≥ 1). Similar results hold more generally for higher k-invariants if X is an iterated loop space. Moreover, we provide in all cases explicit universal upper bounds for the order of the k-invariants of X

Atomic layer deposition: Low temperature process well adapted to ULSI and TFT technologies

The high k dielectrics is an important materials to be integrate in future Ultra Large Scale Integration (ULSI) and future TFT technology. Indeed, to keep on the Moore\u27s Law curve, the reduction of silicon oxide (SiO2) thickness still required, but this reduction is hindered by tunneling current leakage limit. Consequently, it is important to replace SiO2 by another materials with high dielectric constant. The use of this material in manufacturing of gate dielectric in Thin-film transistor (TFT) and in Complementary Metal Oxide Semiconductor (CMOS) will increase gate capacitance with maintaining a low leakage current. Titanium dioxide is a good candidate due to its high dielectric constant in its rutile crystalline phase (180).This rutile structure is obtained at low temperature (250°C) by ALD deposition when TiO2 is deposited on ruthenium dioxide (RuO2) layer thanks to the small lattice mismatch between these two materials

Associations Between Maternal Post-traumatic Stress Disorder and Traumatic Events With Child Psychopathology: Results From a Prospective Longitudinal Study.

Introduction: Exposure to interpersonal violence (IPV) can lead to post-traumatic stress disorder (PTSD) in mothers, and in turn adversely affect the mother-child relationship during early development, as well as the mental health of their children. Our objectives are to assess: (1) the association of maternal IPV-PTSD to child psychopathology, (2) the association of maternal IPV independently of PTSD to child psychopathology, and (3) the relationship between child exposure to violence to the psychopathology of these children. Methods: We used data from the longitudinal Geneva Early Childhood Stress Project. The sample included 64 children [mean age at Phase 1 = 2.4 (1.0-3.7) years] of mothers with or without IPV-PTSD. Data on mothers was collected during Phase 1, using the Clinical Administered PTSD Scale (CAPS), the Brief Physical and Sexual Abuse Questionnaire (BPSAQ) and the Conflict Tactics Scale (CTS2). Modules of a semi-structured diagnostic interview, and the Violence Exposure Scale were used to collect information on child at Phase 2, when children were older [mean age = 7.02 (4.7-10)]. Results: A higher CAPS score in mothers when children were toddler-age was associated with an increased risk of symptoms of attention deficit/hyperactivity disorder (ADHD; β = 0.33, p = 0.014) and PTSD in school-age children. The association between maternal IPV-PTSD and child PTSD (β = 0.48, p &lt; 0.001) symptoms remained significant after adjustment for potential confounders. Among children, exposure to violence was associated with an increased risk of symptoms of generalized anxiety (β = 0.37, p = 0.006), major depressive (β = 0.24, p = 0.039), ADHD (β = 0.27, p = 0.040), PTSD (β = 0.52, p &lt; 0.001), conduct (β = 0.58, p = 0.003) and oppositional defiant (β = 0.34, p = 0.032) disorders. Conclusion: Our longitudinal findings suggest that maternal IPV-PTSD during the period of child development exert an influence on the development of psychopathology in school-aged children. Mothers' IPV was associated with child psychopathology, independently of PTSD. Child lifetime exposure to violence had an additional impact on the development of psychopathology. Careful evaluation of maternal life-events is essential during early childhood to reduce the risk for the development of child psychopathology. Early efforts to curb exposure to violence in children and early intervention are both needed to reduce further risk for intergenerational transmission of trauma, violence, and related psychopathology

On the complex and dimensional relationship of maternal PTSD during early childhood and child outcomes at school-age.

Several studies have shown associations between maternal interpersonal violence-related posttraumatic stress disorder (PTSD), child mental health problems, and impaired socioemotional development. However, the existing literature lacks evidence linking constellations of risk factors such as maternal interpersonal-violence-related PTSD, psychopathology, and interactive behavior with toddlers and outcome measures at school-age. This study involved a prospective, longitudinal investigation of 62 mothers and examined the relationship between maternal variables measured when children were in early childhood (mean age 27 months), and child outcomes when children were school-age (age mean = 83.2 months) while retaining a focus on the context of maternal PTSD. To identify and weigh associated dimensions comparatively, we employed sparse canonical correlation analysis (sCCA) aimed at associating dimensions of a dataset of 20 maternal variables in early childhood with that of more than 20 child outcome variables (i.e., child psychopathology, life-events, and socioemotional skills) at school-age. Phase 1 variables with the highest weights were those of maternal psychopathology: PTSD, depressive and dissociative symptoms, and self-report of parental stress. The highest weighted Phase 2 child outcome measures were those of child psychopathology: PTSD, anxiety, and depressive symptoms as well as peer bullying and victimization. sCCA revealed that trauma-related concepts in mothers were significantly and reliably associated with child psychopathology and other indicators of risk for intergenerational transmission of violence and victimization. The results highlight the dimensional and multifaceted nature-both for mothers as well as children-of the intergenerational transmission of violence and associated psychopathology

Identificação de polimorfismos em genótipos de Coffea arabica de uma coleção da Etiópia.

Os marcadores moleculares são ferramentas importantes para acelerar os programas de melhoramento. Para o cafeeiro, uma espécie perene, o uso de marcadores é particularmente desejável devido ao tempo e recursos gastos para o lançamento de uma nova cultivar. Duas espécies do gênero Coffea são responsáveis por quase toda a produção de café: Coffea arabica e C. canephora. Contudo, para C. arabica, o número de marcadores polimórficos é relativamente baixo comparado a C. canephora e outras culturas, uma vez que a espécie apresenta baixa diversidade genética. Muitos estudos com marcadores genéticos foram feitos para analisar a diversidade da C. arabica, mas os resultados não foram eficientes para a discriminação genotípica detalhada e mapeamento genético. O Instituto Agronômico do Paraná (IAPAR) possui uma coleção de 132 acessos de C. arabica originários da Etiópia, que apresentam variabilidade fenotípica com potencial para serem utilizados para exploração da diversidade. Neste sentido, este estudo buscou analisar a diversidade nucleotídica pela identificação de polimorfismos, SNPs e INDELs, de uma população do centro de origem de C. arabica, associado com o sequenciamento de nova geração. O RNA-seq de dois tecidos, frutos e folhas, de quatro genótipos de C. arabica de uma população da Etiópia, C. arabica cv. Mundo Novo e de um dos seus ancestrais de C. arabica ? C. eugenioides, foram sequenciados pela metodologia Illumina HiSeq2000. Os reads obtidos foram processados e posteriormente as sequências foram mapeadas em uma referência de C. canephora para identificação dos polimorfismos. Foram feitas duas estratégias: i) na primeira estratégia, foi utilizado uma ferramenta chamada SNiPloid com critérios de cobertura para o polimorfismo identificado e ii) uma segunda estratégia que considera os polimorfismos encontrados diretamente dos arquivos de detecção dos polimorfismos. Os resultados identificaram um número grande de polimorfismos. Na primeira estratégia, foram encontrados pelo menos 5.500 SNPs potenciais para a genotipagem e na segunda, 103.791 SNPs potenciais. Para essa última, ainda é necessário estabelecer critérios e filtros para escolher os polimorfismos que serão inicialmente genotipados. Os dados também mostraram a importância de utilizar um grupo mais diverso de genótipos associado com o sequenciamento de nova geração para detecção de SNPs. Este trabalho será importante para direcionar futuros trabalhos na caracterização da diversidade genética em C. arabica, além de estudos de mapeamento genético por associação