Growth and chemical characterisation studies of Mn silicate barrier layers on SiO2 and CDO

This thesis investigates the suitability of manganese silicate (MnSiO3) as a possible copper interconnect diffusion barrier layer on both a 5.4 nm thick thermally grown SiO2 and a low dielectric constant carbon doped oxide (CDO), with the focus of understanding the barrier formation process. The self forming nature of this diffusion barrier layer resulting from the chemical interaction of deposited Mn with the insulating substrate has potential application in future generations of copper interconnect technologies as they are significantly thinner than the conventional deposited barrier layers. The principle technique used to study the interface chemistry resulting from the interaction of deposited manganese with the insulating substrates to form a MnSiO3 layer was x-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) measurements provided information on the structure of the barrier layers which could be correlated with the XPS results. Significant differences in the extent of the interface interaction which resulted in the formation of the MnSiO3 barrier layer were found to depend on whether the deposited Mn was partially oxidised. The studies performed on the 5.4 nm thermally grown SiO2 confirmed that the growth of the MnSiO3 resulted in a corresponding reduction in the SiO2 layer thickness. Interactions between residual metallic Mn and subsequently deposited copper layers were also investigated and showed that in order to reduce the width of the barrier layer, it was preferable that all the deposited Mn was fully incorporated into the silicate. TEM measurements were also used to investigate thicker thermally deposited Mn/Cu heterostructures on SiO2 which were subsequently annealed in order to study the diffusion interactions between copper and manganese. The formation of Mn silicate layers on low dielectric constant carbon doped oxide (CDO) was also investigated and compared with the formation characteristics on the thermally grown SiO2

Characterisation of electroless deposited Cobalt by hard and soft X-ray photoemission spectroscopy

Electroless deposited (ELD) cobalt with palladium as a catalyst, and an underlying self-assembled monolayer (SAM) was investigated for potential use in advanced complementary metal oxide semiconductor (CMOS) applications using both hard (HAXPES) and soft (XPS) x-ray photoelectron spectroscopy. HAXPES spectra established the uniformity of the deposited Co film and the nature of the buried Co-Si interface ~20nm below the surface. The Pd is seen to diffuse through the Co following thermal annealing. While the deposited Co film is predominantly metallic, Co-silicide forms at the Co-Si interface upon deposition and decomposes with thermal anneal up to 500°C

A new method for assessing the recyclability of powders within Powder Bed Fusion process

Recycling metallic powders used in the additive manufacturing (AM) process is essential for reducing the process cost, manufacturing time, energy consumption, and metallic waste. In this paper, the focus is on pore formation in recycled powder particles of stainless steel 316L during the selective laser melting process. We have introduced the concept of optimizing the powder bed's printing area in order to see the extent of the affected powders during the 3D-printing process. X-ray Computed Tomography (XCT) is used to characterize the pores inside the particles. The results from image processing of the tomography (rendered in 3D format) indicate a broader pore size distribution and a higher pore density in recycled powders compared to their virgin counterparts. To elucidate on this, the Electron Dispersion spectroscopy (EDX) analysis and Synchrotron-based Hard X-ray Photoelectron Spectroscopy (HAXPES) were performed to reveal the chemical composition distribution across the pore area and bulk of the recycled powder particles. Higher concentrations of Fe, Cr, and Ni were recorded on the interior wall of the pore in recycled particles and higher Mn, S and Si concentrations were recorded in the outer layer around the pore area and on the surface of the recycled particle. The pore formation in recycled powder is attributed to out-diffusion of Mn, S and Si to the outer surface as a result of the incident laser heat during the AM process due to higher electron affinity of such metallic elements to oxygenation. HAXPES analysis shows a higher MnO concentration around the pore area which impedes the in-diffusion of other elements into the bulk and thereby helps to creates a void. The inside wall of the pore area (dendrites), has a higher concentration of Fe and Cr oxide. We believe the higher pore density in recycled powders is due, at least in part to composition redistribution, promoted by laser heat during the AM process. Nanoindentation analyses on both virgin and recycled powder particles shows a lower hardness and higher effective modulus in the recycled powder particles attributed to the higher porosity in recycled powders

SNAPSHOT USA 2019 : a coordinated national camera trap survey of the United States

This article is protected by copyright. All rights reserved.With the accelerating pace of global change, it is imperative that we obtain rapid inventories of the status and distribution of wildlife for ecological inferences and conservation planning. To address this challenge, we launched the SNAPSHOT USA project, a collaborative survey of terrestrial wildlife populations using camera traps across the United States. For our first annual survey, we compiled data across all 50 states during a 14-week period (17 August - 24 November of 2019). We sampled wildlife at 1509 camera trap sites from 110 camera trap arrays covering 12 different ecoregions across four development zones. This effort resulted in 166,036 unique detections of 83 species of mammals and 17 species of birds. All images were processed through the Smithsonian's eMammal camera trap data repository and included an expert review phase to ensure taxonomic accuracy of data, resulting in each picture being reviewed at least twice. The results represent a timely and standardized camera trap survey of the USA. All of the 2019 survey data are made available herein. We are currently repeating surveys in fall 2020, opening up the opportunity to other institutions and cooperators to expand coverage of all the urban-wild gradients and ecophysiographic regions of the country. Future data will be available as the database is updated at eMammal.si.edu/snapshot-usa, as well as future data paper submissions. These data will be useful for local and macroecological research including the examination of community assembly, effects of environmental and anthropogenic landscape variables, effects of fragmentation and extinction debt dynamics, as well as species-specific population dynamics and conservation action plans. There are no copyright restrictions; please cite this paper when using the data for publication.Publisher PDFPeer reviewe

Mammal responses to global changes in human activity vary by trophic group and landscape

Wildlife must adapt to human presence to survive in the Anthropocene, so it is critical to understand species responses to humans in different contexts. We used camera trapping as a lens to view mammal responses to changes in human activity during the COVID-19 pandemic. Across 163 species sampled in 102 projects around the world, changes in the amount and timing of animal activity varied widely. Under higher human activity, mammals were less active in undeveloped areas but unexpectedly more active in developed areas while exhibiting greater nocturnality. Carnivores were most sensitive, showing the strongest decreases in activity and greatest increases in nocturnality. Wildlife managers must consider how habituation and uneven sensitivity across species may cause fundamental differences in human–wildlife interactions along gradients of human influence.Peer reviewe

Growth and chemical characterisation studies of Mn silicate barrier layers on SiO2 and CDO

This thesis investigates the suitability of manganese silicate (MnSiO3) as a possible copper interconnect diffusion barrier layer on both a 5.4 nm thick thermally grown SiO2 and a low dielectric constant carbon doped oxide (CDO), with the focus of understanding the barrier formation process. The self forming nature of this diffusion barrier layer resulting from the chemical interaction of deposited Mn with the insulating substrate has potential application in future generations of copper interconnect technologies as they are significantly thinner than the conventional deposited barrier layers. The principle technique used to study the interface chemistry resulting from the interaction of deposited manganese with the insulating substrates to form a MnSiO3 layer was x-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) measurements provided information on the structure of the barrier layers which could be correlated with the XPS results. Significant differences in the extent of the interface interaction which resulted in the formation of the MnSiO3 barrier layer were found to depend on whether the deposited Mn was partially oxidised. The studies performed on the 5.4 nm thermally grown SiO2 confirmed that the growth of the MnSiO3 resulted in a corresponding reduction in the SiO2 layer thickness. Interactions between residual metallic Mn and subsequently deposited copper layers were also investigated and showed that in order to reduce the width of the barrier layer, it was preferable that all the deposited Mn was fully incorporated into the silicate. TEM measurements were also used to investigate thicker thermally deposited Mn/Cu heterostructures on SiO2 which were subsequently annealed in order to study the diffusion interactions between copper and manganese. The formation of Mn silicate layers on low dielectric constant carbon doped oxide (CDO) was also investigated and compared with the formation characteristics on the thermally grown SiO2

Chemical and structural investigations of the interactions of Cu with MnSiO3 diffusion barrier layers

X-ray photoelectron spectroscopy (XPS) has been used to investigate the thermodynamic stability of Cu layers deposited onto Mn silicate (MnSiO3) barrier layers formed on SiO2 surfaces. Using a fully in situ growth and analysis experimental procedure, it has been shown that 1nm Cu layers do not chemically react with ultra thin ( 2.6 nm) MnSiO3 surfaces following 400 C annealing, with no evidence for the growth of Cu oxide species, which are known to act as an intermediate step in the Cu diffusion process into silica based dielectrics. The effectiveness of MnSiO3 as a barrier to Cu diffusion following high temperature annealing was also investigated, with electron energy loss spectroscopy suggesting that a 2.6 nm MnSiO3 layer prevents Cu diffusion at 400 C. The chemical composition of a barrier layer formed following the deposition of a partially oxidised Mn (MnOx)/Cu alloy was also investigated using XPS in order to determine if the presence of Cu at the Mn/SiO2 interface during MnSiO3 growth inherently changes the chemical composition of the barrier layer. In contrast to previous publications, it has been shown that Mn oxide species do not form in the barrier region during thermal annealing, with Cu appearing to be chemically inert in the presence of Mn and SiO2.Fundación de Ciencias de Irlanda 08/IN.1/I205