Multi-scale modelling and experimental analysis of ALD alumina : Interplay of process dynamics, chemistry and interfacial phenomena

The constant shrinking of microelectronic devices requires the production of conformal and uniform nanometric thin films, with a high chemical purity and abrupt interfaces. In this context, Atomic Layer Deposition (ALD) has emerged as a favorable process to produce such films. Drawing its advantages from the self-limiting nature of the surface reactions involved, ALD can yield thickness control down to the monolayer, producing conformal films of high purity. Although ALD has many advantages, drawbacks arise when depositing films of some nanometers. In particular, the initial island growth and the formation of an interfacial oxide layer are two of its main limitations, especially for the case of metal oxide ALD on Si. Moreover, the deposition on large area wafers is not always uniform, and depends on the reactor and process design. These drawbacks need to be suppressed in order to establish ALD as the adequate process for the deposition of high-k gate oxides on Si, essential for the production of field effect transistors of the future. In this thesis, the ALD of Al2O3 from TMA and H2O on Si is thoroughly investigated, in order to tackle the above drawbacks. The investigation consists of a combined multiscale computational and experimental approach. Four different numerical models were developed dealing with different space scales. A complete set of characterization techniques was used, including ellipsometry, XRR, TEM, STEM, EDX, XPS and SIMS. Using this framework, the detailed phenomena involved are illuminated, thus allowing to better understand the process and identify the factors responsible for the drawbacks of ALD. The competition between surface mechanisms, namely desorption and surface reactions, was found to be the limiting factor for deposition at low temperatures, up to 200oC. The concentration of surface reactive sites was found to limit the deposition at higher temperatures up to 300oC. Although ALD is conceived as a process depending only on surface chemistry, the analysis of the transport phenomena inside the ALD chamber showed that the reactor and process design can affect the reactant and temperature distribution inside the ALD reactor. The multiscale approach and the coupling among the different computational models revealed that the interplay between surface mechanisms and transport phenomena affects the film uniformity. Using this computational approach, it was possible to derive optimal process conditions that ensure maximum film uniformity. During the first deposition steps, the film deposition was found to be inhibited, leading to an island growth regime. The integrated analysis showed that 25 cycles are needed in order to deposit a continuous Al2O3 film. During this regime, interfacial oxidation of the Si substrate led to the formation of a ~2 nm interfacial oxide layer, consisting of SiOx, AlOx, and Al-silicates, which degrades the properties and thus the potential applications of the deposited structure. An in situ N2-NH3 plasma pretreatment of the HF-cleaned Si substrate was introduced, leading to a formation of a SixNyH layer on the substrate surface. The pretreatment was found to enhance the surface reactivity, as the inhibition period was restricted and linear ALD growth was obtained even after 5 cycles. Furthermore, interfacial Si oxidation was reduced, as the SixNyH layer was found to serve as an effective barrier for O diffusion and Si oxidation. The work presented in this thesis demonstrates the necessity of such integrated approaches to analyze the detailed phenomena involved in ALD. Such studies help in the thorough understanding of the ALD mechanisms, and consequently in elaborating solutions which restrict the drawbacks arising during the initial deposition steps. This could pave the way for the ALD process to industrially produce uniform and conformal nanometric thin films of high purity and abrupt interfaces, able to answer to the demands of the future electronic industry

Impact, Inclusiveness and Outreach: Outputs from the MW-Gaia WG5 School

The main goal of MW-Gaia is to enhance the scientific exploration of the Gaia satellite results across the community in Europe and beyond. WG5 working group is devoted to impact, inclusiveness and outreach, and one of the workshops organized towards this plan is the WG5 School. The program includes four sessions, workshops, hands-on activities covering topics such as public engagement, practical skills for engaging with diverse audiences, and training in social innovation. As a selected participant for the school, we will present the outputs of this event, such as ideas and initiatives to improve inclusion and impact, reinforcing the importance of equity, diversity, and inclusion commitment in research. Lastly, this poster will present the highlights from the participants’ assigned projects, showcasing the ideas developed during the school

Reviving Horndeski Theory using Teleparallel Gravity after GW170817

Horndeski gravity was highly constrained from the recent gravitational wave observations by the LIGO Collaboration down to $|c_{g}/c-1|\gtrsim 10^{-15}$. In this Letter we study the tensorial perturbations in a flat cosmological background for an analogue version of Horndenki gravity which is based in Teleparallel Gravity constructed from a flat manifold with a nonvanishing torsion tensor. It is found that in this approach, one can construct a more general Horndeski theory satisfying $c_T=c_g/c=1$ without eliminating the coupling functions $G_5(\phi,X)$ and $G_4(\phi,X)$ that were highly constrained in standard Horndeski theory. Hence, in the Teleparallel approach one is able to restore these terms, creating an interesting way to revive Horndeski gravity.Comment: 12 pages, 0 figure

Circulating and Disseminated Tumor Cells in the Management of Advanced Prostate Cancer

Management of prostate cancer is recognized as one of the most important medical problems. Latest findings concerning the role of circulating (CTC) and disseminated tumor cells (DTC) have provided new insights into the biology of metastasis with important implications for the clinical management of prostate cancer patients. Most of the established methods of circulating/disseminated tumor cell enrichment use density-gradient centrifugation and immunomagnetic procedures. Reverse transcriptase polymerase chain reaction is another used detection technique. Novel methods, the CTC-chip and the epithelial immunospot assay already showed promising results. For localized and metastatic prostate cancer, significant correlations between spreading tumor cells and well-established indicators of disease activity have been demonstrated. Careful randomized prospective trials will be required to justify the routine use of CTCs/DTCs for therapy decision making

Consciousness and Social Cognition from an Interactionist Perspective: A New Approach on Understanding Normal and Abnormal Relations between Metacognition and Mindreading

Contemporary discussions on relations between metacognition and mindreading result in several theoretical accounts allowing various combinations of both mechanisms in the process of formation of beliefs, intentions, and decisions with respect to oneself or others. In fact, various prefrontal areas of the brain are activated when individuals mentalize about themselves and about other people. Interestingly, the latest accounts of the relationship between mindreading and metacognition clearly favor arguments for interactionism between functionally different mechanisms in the formation of our social knowledge. In particular, a two-level architecture enables a mutual interaction within a complex metacognitive system that is evolutionarily structured into higher and lower level metacognition with different functions and tasks. In our opinion, cognitive architecture of such systems needs to include conscious mechanisms that incorporate information accessibility as activation through the interaction. Here, we will argue that the combination of the two-level account on mindreading and metacognition along with a global broadcasting architecture embedded in the human brain is a good starting point that explains formation of accurate social knowledge and access to such knowledge. In our opinion, it becomes clear that consciousness via the interaction activates many unconscious brain regions, including interpreter systems such as metacognition and mindreading

Computational Models of Consciousness-Emotion Interactions in Social Robotics: Conceptual Framework

There is a little information on how to design a social robot that effectively executes consciousness-emotion (C-E) interaction in a socially acceptable manner. In fact, development of such socially sophisticated interactions depends on models of human high-level cognition implemented in the robot’s design. Therefore, a fundamental research problem of social robotics in terms of effective C-E interaction processing is to define a computational architecture of the robotic system in which the cognitive-emotional integration occurs and determine cognitive mechanisms underlying consciousness along with its subjective aspect in detecting emotions. Our conceptual framework rests upon assumptions of a computational approach to consciousness, which points out that consciousness and its subjective aspect are specific functions of the human brain that can be implemented into an artificial social robot’s construction. Such research framework of developing C-E addresses a field of machine consciousness that indicates important computational correlates of consciousness in such an artificial system and the possibility to objectively describe such mechanisms with quantitative parameters based on signal-detection and threshold theories