Anthony P. McCoy

Scanning transmission electron microscopy investigations of self-forming diffusion barrier formation in Cu(Mn) alloys on SiO2

Scanning transmission electron microscopy in high angle annular dark field mode has been used to undertake a characterisation study with sub-nanometric spatial resolution of the barrier formation process for a Cu(Mn) alloy (90%/10%) deposited on SiO2. Electron energy loss spectroscopy (EELS) measurements provide clear evidence for the expulsion of the alloying element to the dielectric interface as a function of thermal annealing where it chemically reacts with the SiO2. Analysis of the Mn L23 intensity ratio in the EELS spectra indicates that the chemical composition in the barrier region which has a measured thickness of 2.6 nm is MnSiO3.

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 ∼1 nm 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 inherent...

In Situ XPS Chemical Analysis of MnSiO3 Copper Diffusion Barrier Layer Formation and Simultaneous Fabrication of Metal Oxide Semiconductor Electrical Test MOS Structures

Copper/SiO2/Si metal-oxide-semiconductor (MOS) devices both with and without a MnSiO3 barrier layer at the Cu/SiO2 interface have been fabricated in an ultrahigh vacuum X-ray photoelectron spectroscopy (XPS) system, which allows interface chemical characterization of the barrier formation process to be directly correlated with electrical testing of barrier layer effectiveness. Capacitance voltage (CV) analysis, before and after tube furnace anneals of the fabricated MOS structures showed that the presence of the MnSiO3 barrier layer significantly improved electric stability of the device structures. Evidence of improved adhesion of the deposited copper layer to the MnSiO3 surface compared to the clean SiO2 surface was apparent both from tape tests and while probing the samples during electrical testing. Secondary ion mass spectroscopy (SIMS) depth profiling measurements of the MOS test structures reveal distinct differences of copper diffusion into the SiO2 dielectric layers following the thermal anneal depending on the presence of the MnSiO3 barrier layer.

Chemical and structural investigations of the incorporation of metal manganese into ruthenium thin films for use as copper diffusion barrier layers

The incorporation of manganese into a 3 nm ruthenium thin-film is presented as a potential mechanism to improve its performance as a copper diffusion barrier. Manganese (∼1 nm) was deposited on an atomic layer deposited Ru film, and the Mn/Ru/SiO2 structure was subsequently thermally annealed. X-ray photoelectron spectroscopy studies reveal the chemical interaction of Mn with the SiO2 substrate to form manganese-silicate (MnSiO3), implying the migration of the metal through the Ru film. Electron energy loss spectroscopy line profile measurements of the intensity of the Mn signal across the Ru film confirm the presence of Mn at the Ru/SiO2 interface.

The impact of porosity on the formation of manganese based copper diffusion barrier layers on low- κ dielectric materials

This work investigates the impact of porosity in low-κ dielectric materials on the chemical and structural properties of deposited Mn thin films for copper diffusion barrier layer applications. X-ray photoelectron spectrscopy (XPS) results highlight the difficulty in distinguishing between the various Mn oxidation states which form at the interlayer dielectric (ILD)/Mn interface. The presence of MnSiO3 and MnO were identified using x-ray absorption spectroscopy (XAS) measurements on both porous and non-porous dielectric materials with evidence of Mn2O3 and Mn3O4 in the deposited film on the latter surface. It is shown that a higher proportion of deposited Mn converts to Mn silicate on an ILD film which has 50% porosity compared with the same dielectric material with no porosity, which is attributed to an enhanced chemical interaction with the effective larger surface area of porous dielectric materials. Transmission electron microscopy (TEM) and energy-dispersive x-ray spectroscopy (EDX) data shows that the Mn overlayer remains predominately surface localised on both porous and non-porous materials.

Investigation of the release of Si from SiO2 during the formation of manganese/ruthenium barrier layers

The thermodynamic and structural stability of ruthenium-manganese diffusion barriers on SiO2 is assessed. A ∼2 nm film composed of partially oxidized manganese (MnOx where x < 1) was deposited on a 3 nm thick Ru film and the Mn-MnOx/Ru/SiO2 structure was subsequently thermally annealed. X-ray photoelectron spectroscopy and secondary ion mass spectroscopy studies suggest the release and upward diffusion of Si from the dielectric substrate as a result of manganese-silicate formation at the Ru/SiO2 interface. The migration of Si up through the Ru film results in further manganese-silicate formation upon its interaction with the Mn-MnOx deposited layer.

Investigation of the thermal stability of Mo-In0.45Ga0.47As for applications as source/drain contacts

The electrical and chemical stability of Mo-InGaAs films for source-drain applications in transistor structures has been investigated. It was found that for 5 nm thick Mo films, the sheet resistance remains approximately constant with increasing anneal temperatures up to 500 °C. A combined hard x-ray photoelectron spectroscopy and x-ray absorption spectroscopy analysis of the chemical structure of the Mo-InGaAs alloy system as a function of annealing temperature showed that the interface is chemically abrupt with no evidence of inter-diffusion between the Mo and InGaAs layers. These results indicate the suitability of Mo as a thermally stable, low resistance source-drain contact metal for InGaAs-channel devices.

Pulsed-Plasma Physical Vapor Deposition Approach Toward the Facile Synthesis of Multilayer and Monolayer Graphene for Anticoagulation Applications.

We demonstrate the growth of multilayer and single-layer graphene on copper foil using bipolar pulsed direct current (DC) magnetron sputtering of a graphite target in pure argon atmosphere. Single-layer graphene (SG) and few-layer graphene (FLG) films are deposited at temperatures ranging from 700 °C to 920 °C within <30 min. We find that the deposition and post-deposition annealing temperatures influence the layer thickness and quality of the graphene films formed. The films were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and optical transmission spectroscopy techniques. Based on the above studies, a diffusion-controlled mechanism was proposed for the graphene growth. A single-step whole blood assay was used to investigate the anticoagulant activity of graphene surfaces. Platelet adhesion, activation, and morphological changes on the graphene/glass surfaces, compared to bare glass, were analyzed using fluorescence microscopy and SEM techniques. We have found significant suppression of the platelet adhesion, activation, and aggregation on the graphene-covered surfaces, compared to the bare glass, indicating the anticoagulant activity of the deposited graphene films. Our production technique represents an industrially relevant method for the growth of SG and FLG for various applications including the biomedical field.

Highly enhanced UV responsive conductivity and blue emission in transparent CuBr films: implication for emitter and dosimeter applications

Highly efficient transparent blue emitters have been pursued for many years, driven in large part by solid-state lighting technology, and the need for blue/UV spectroscopic sources. CuBr is a strong candidate material, chiefly due to its relatively large excitonic binding energies. However, the semiconductor copper halides (CuCl, CuBr, CuI) have been plagued by their relatively inefficient light emission properties, often attributed to intrinsic defect structures. Here we report a novel UV-treatment based approach to achieve massive and persistent enhancements in the room temperature electrical conductivity and blue photoluminescence (PL) in CuBr films in ambient air, an important finding for future light emitting application. After this treatment (typically UV exposure for ∼20 minutes), we have observed an approximately 5 orders of magnitude enhancement in electrical conductivity, and 2 orders of magnitude enhancement in PL, respectively. These enhancements are correlated with the cumulative UV exposure. We also found that the emission energies of the films can be tuned by varying the excitation wavelength. A mechanism based on the formation of luminescent excimer/exciplexes with cuprophilic interactions is proposed to explain the observed unusual photophysical characteristics. The potential of these films for UV dosimeter application is demonstrated by fabricating a device and monitoring the current readout as a function of UV dose, which is substantially sensitive to a dose range of 1–1000 mJ cm−2. This work provides valuable insights into the interesting photophysical properties of CuBr films, and opens a pathway to their deployment across a wide range of applications.

The addition of aluminium and manganese to ruthenium liner layers for use as a copper diffusion barrier

The chemical interaction of Al and Mn deposited on Ru thin films for use as copper diffusion barrier layers are assessed in-situ using x-ray photoelectron spectroscopy (XPS). Thin (~1-2 nm) Al and Mn films were separately deposited on 3 nm Ru liner layers on SiO₂, and both Al/Ru/SiO₂ and Mn/Ru/SiO₂ structures were subsequently thermally annealed. Results indicate the diffusion of both metals through the Ru thin films and the subsequent chemical interaction with the underlying SiO₂ substrate to form Al₂O₃ and MnSiO₃. In both cases, the reduction of SiO₂ leads to the release of Si from the dielectric and the upward diffusion of Si into the Ru liner layers.