J. Bogan

Synchrotron radiation photoemission study of in situ manganese silicate formation on SiO2 for barrier layer applications

Synchrotron radiation photoelectron spectroscopy (SRPES) is used to investigate the in situ formation of ultra thin Mn silicate layers on SiO2, which has relevance for copper diffusion barrier layers in microelectronic devices. High temperature vacuum annealing of metallic Mn (∼1.5 nm) deposited on a 4 nm thermally grown SiO2 film results in the self limiting formation of a magnesium silicate layer, the stoichiometry of which is consistent with the formation of MnSiO3. Curve fitted Mn 3p SRPES spectra show no evidence for the presence of a manganese oxide phase at the Mn/SiO2 interface, in contrast to previous reports.

Chemical and structural investigation of the role of both Mn and Mn oxide in the formation of manganese silicate barrier layers on SiO2

In this study, Mn silicate (MnSiO3) barrier layers were formed on thermally grown SiO2 using both metallic Mn and oxidized Mn films, in order to investigate the role of oxygen in determining the extent of the interaction between the deposited Mn and the SiO2 substrate. Using x-ray photoelectron spectroscopy, it has been shown that a metallic Mn film with an approximate thickness of 1 nm cannot be fully converted to Mn silicate following vacuum annealing to 500 °C. Transmission electron microscopy (TEM) analysis suggests the maximum MnSiO3 layer thickness obtainable using metallic Mn is ∼1.7 nm. In contrast, a ∼1 nm partially oxidized Mn film can be fully converted to Mn silicate following thermal annealing to 400 °C, forming a MnSiO3 layer with a measured thickness of 2.6 nm. TEM analysis also clearly shows that MnSiO3 growth results in a corresponding reduction in the SiO2 layer thickness. It has also been shown that a fully oxidized Mn oxide thin film can be converted to Mn silicate, in the absence of m...

Photoemission study of carbon depletion from ultralow-κ carbon doped oxide surfaces during the growth of Mn silicate barrier layers

In this study Mn silicate (MnSiO3) barrier layers were formed on ultralow dielectric constant carbon doped oxide (CDO) surfaces, using both metallic Mn and oxidized Mn films, in order to determine the growth method best suited to preventing the depletion of carbon from the CDO surface. Using x-ray photoelectron spectroscopy it has been shown that the deposition of metallic Mn and partially oxidized Mn (MnOx, where x < 1) films on CDO surfaces results in the formation of both MnSiO3 and an Mn carbide species within the barrier layer region. Analysis suggests that Mn carbide species are formed through the depletion of C from the CDO structure, which may increase the dielectric constant of the CDO. In a separate experiment, it was shown that the interaction of a fully oxidized Mn (MnOy, where y ≥ 1) layer on CDO resulted in the growth of a MnSiO3 barrier layer free from Mn carbide, metallic Mn, and Mn oxide. These studies indicate that Mn carbide is only formed on the CDO surface in the presence of metallic ...

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.

Exploring the Role of Adsorption and Surface State on the Hydrophobicity of Rare Earth Oxides

Rare earth oxides (REOs) are attracting attention for use as cost-effective, high-performance dropwise condensers because of their favorable thermal properties and robust nature. However, to engineer a suitable surface for industrial applications, the mechanism governing wetting must be first fully elucidated. Recent studies exploring the water-wetting state of REOs have suggested that these oxides are intrinsically hydrophobic owing to the unique electronic structure of the lanthanide series. These claims have been countered with evidence that they are inherently hydrophilic and that adsorption of contaminants from the environment is responsible for the apparent hydrophobic nature of these surfaces. Here, using X-ray photoelectron spectroscopy and dynamic water contact angle measurements, we provide further evidence to show that REOs are intrinsically hydrophilic, with ceria demonstrating advancing water contact angles of ≈6° in a clean surface state and similar surface energies to two transition metal oxides (≳72 mJ/m2). Using two model volatile species, it is shown that an adsorption mechanism is responsible for the apparent hydrophobic property observed in REOs as well as in transition metal oxides and silica. This is correlated with the screening of the polar surface energy contribution of the underlying oxide with apparent surface energies reduced to <40 mJ/m2 for the case of nonane adsorption. Moreover, we show that the degree of surface hydroxylation plays an important role in the observed contact angle hysteresis with the receding contact angle of ceria increasing from ∼10° to 45° following thermal annealing in an inert atmosphere. Our findings suggest that high atomic number metal oxides capable of strongly adsorbing volatile species may represent a viable paradigm toward realizing robust surface coating for industrial condensers if certain challenges can be overcome.

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.

In-situ surface and interface study of atomic oxygen modified carbon containing porous low-κ dielectric films for barrier layer applications

The surface treatment of ultralow-κ dielectric layers by exposure to atomic oxygen is presented as a potential mechanism to modify the chemical composition of the dielectric surface to facilitate copper diffusion barrier layer formation. High carbon content, low-κ dielectric films of varying porosity were exposed to atomic oxygen treatments at room temperature, and x-ray photoelectron spectroscopy studies reveal both the depletion of carbon and the incorporation of oxygen at the surface. Subsequent dynamic water contact angle measurements show that the chemically modified surfaces become more hydrophilic after treatment, suggesting that the substrates have become more “SiO2-like” at the near surface region. This treatment is shown to be thermally stable up to 400 °C. High resolution electron energy loss spectroscopy elemental profiles confirm the localised removal of carbon from the surface region. Manganese (≈1 nm) was subsequently deposited on the modified substrates and thermally annealed to form surfa...