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Abstract The resistivity scaling of Cu electrical interconnects represents a critical challenge in Si CMOS technology. As interconnect dimensions reach below 10 nm, Cu resistivity increases significantly due to surface scattering. Topological materials have been considered for application in ultra-scaled interconnects (below 5 nm), due to their topologically protected surface states that have reduced electron scattering. Recent theoretical work on the topological chiral semimetal CoSi suggests that this material could offer lower resistivity than Cu at dimensions smaller than 10 nm. Here we investigate the scaling trend of textured and amorphous CoSi thin films, deposited by molecular beam epitaxy in a thickness range between 2 and 82.5 nm. Contrary to predictions of standard resistivity models, we report here a reduction in resistivity for thin amorphous CoSi films, which is instead consistent with surface-dominated transport. Moreover, magnetotransport measurements reveal significant enhancement of the magnetoresistance in scaled films, highlighting the complex transport mechanisms present in these highly disordered films at thicknesses of a few nanometers.

The resistivity scaling of Cu electrical interconnects represents a critical challenge in Si CMOS technology. As interconnect dimensions reach below 10 nm, Cu resistivity increases significantly due to surface scattering. Topological materials have been considered for application in ultra-scaled interconnects (below 5 nm), due to their topologically protected surface states that have reduced electron scattering. Recent theoretical work on the topological chiral semimetal CoSi suggests that this material could offer lower resistivity than Cu at dimensions smaller than 10 nm. Here we investigate the scaling trend of textured and amorphous CoSi thin films, deposited by molecular beam epitaxy in a thickness range between 2 and 82.5 nm. Contrary to predictions of standard resistivity models, we report here a reduction in resistivity for thin amorphous CoSi films, which is instead consistent with surface-dominated transport. Moreover, magnetotransport measurements reveal significant enhancement of the magnetoresistance in scaled films, highlighting the complex transport mechanisms present in these highly disordered films at thicknesses of a few nanometers. [ABSTRACT FROM AUTHOR]

InGaAs is a potential candidate for Si replacement in upcoming advanced technological nodes because of its excellent electron transport properties and relatively low interface defect density in dielectric gate stacks. Therefore, integrating InGaAs devices with the established Si platforms is highly important. Using template-assisted selective epitaxy (TASE), InGaAs nanowires can be monolithically integrated with high crystal quality, although the mechanisms of group III incorporation in this ternary material have not been thoroughly investigated. Here we present a detailed study of the compositional variations of InGaAs nanostructures epitaxially grown on Si(111) and Silicon-on-insulator substrates by TASE. We present a combination of XRD data and detailed EELS maps and find that the final Ga/In chemical composition depends strongly on both growth parameters and the growth facet type, leading to complex compositional sub-structures throughout the crystals. We can further conclude that the composition is governed by the facet-dependent chemical reaction rates at low temperature and low V/III ratio, while at higher temperature and V/III ratio, the incorporation is transport limited. In this case we see indications that the transport is a competition between Knudsen flow and surface diffusion. [ABSTRACT FROM AUTHOR]

A non-local-means algorithm with non-local averaging is used to reduce noise in an electron holography phase map. The noise level is evaluated through wavelet analysis. The method is shown to be effective in reducing noise in the map while preserving both the spatial resolution and underlying map information. Because of the significant noise reduction, the processed phase map is easier to understand and can produce an internal electric field map with a derivative of the phase map. [ABSTRACT FROM AUTHOR]

Strontium titanate, SrTiO3 (STO), thin films incorporated with lanthanum are grown on Si (001) substrates at a thickness range of 5-25 nm. Atomic layer deposition (ALD) is used to grow the LaxSr1-xTiO3 (La:STO) films after buffering the Si (001) substrate with four-unit-cells of STO deposited by molecular beam epitaxy. The crystalline structure and orientation of the La:STO films are confirmed via reflection high-energy electron diffraction, X-ray diffraction, and cross-sectional transmission electron microscopy. The low temperature ALD growth (∼225 °C) and post-deposition annealing at 550 °C for 5min maintains an abrupt interface between Si (001) and the crystalline oxide. Higher annealing temperatures (650 °C) show more complete La activation with film resistivities of ∼2.0×10-2 Ω cm for 20-nm-thick La:STO (x∼0.15); however, the STO-Si interface is slightly degraded due to the increased annealing temperature. To demonstrate the selective incorporation of lanthanum by ALD, a layered heterostructure is grown with an undoped STO layer sandwiched between two conductive La:STO layers. Based on this work, an epitaxial oxide stack centered on La:STO and BaTiO3 integrated with Si is envisioned as a material candidate for a ferroelectric field-effect transistor. [ABSTRACT FROM AUTHOR]

Silicon-germanium (SiGe) is a material that possesses a multitude of applications ranging from transistors to electro-optical modulators and quantum dots. The diverse properties of SiGe also make it attractive to implementations involving superconducting quantum computing. Here, we demonstrate the fabrication of transmon quantum bits on SiGe layers and investigate the microwave loss properties of SiGe at cryogenic temperatures and single photon microwave powers. We find relaxation times of up to 100 μs, corresponding to a quality factor Q above 4 M for large pad transmons. The high Q values obtained indicate that the SiGe/Si heterostructure is compatible with state-of-the-art performance of superconducting quantum circuits. [ABSTRACT FROM AUTHOR]

We report on the stability of high-permittivity (high-k) TiO2 films incorporated in metal-oxide-silicon capacitor structures with a TiN metal gate electrode, focusing on oxygen migration. Titanium oxide films are deposited by either Ti sputtering [physical vapor deposition (PVD)] followed by radical shower oxidation or by plasma-enhanced atomic layer deposition (PEALD) from titanium isopropoxide (Ti{OCH(CH3)2}4) and O2 plasma. Both PVD and PEALD films result in near-stoichiometric TiO2 prior to high-temperature annealing. We find that dopant activation anneals of TiO2-containing gate stacks at 1000 °C cause 5 Å or more of additional SiO2 to be formed at the gate-dielectric/Si-channel interface. Furthermore, we demonstrate for the first time that oxygen released from TiO2 diffuses through the TiN gate electrode and oxidizes the poly-Si contact. The thickness of this upper SiO2 layer continues to increase with increasing TiO2 thickness, while the thickness of the regrown SiO2 at the gate-dielectric/Si interface saturates. The upper SiO2 layer degrades gate stack capacitance, and simultaneously the oxygen-deficient TiOx becomes a poor insulator. In an attempt to mitigate O loss from the TiO2, top and bottom Al2O3 layers are added to the TiO2 gate dielectric as oxygen barriers. However, they are found to be ineffective, due to Al2O3-TiO2 interdiffusion during activation annealing. Bottom HfO2/Si3N4 interlayers are found to serve as more effective oxygen barriers, reducing, though not preventing, oxygen downdiffusion. [ABSTRACT FROM AUTHOR]

Cu–SiO2–SiNx interconnects that were located 0.65–2.7-μm below the surface of silicon-integrated circuits were imaged in a scanning electron microscope and a transmission electron microscope with a scanning attachment by detecting backscattered electrons (BSEs) with an incident electron-beam energy (Eo) in the range of 30–400 keV. BSE images could be used to detect voids in subsurface Cu interconnects, even in regions covered with upper level Cu lines or vias. As Eo was increased from 30 to 400 keV, structures could be seen as a result of atomic number (Z) contrast farther below the surface while structures closer to the surface had reduced Z contrast. The subsurface beam diameter was measured from BSE images as a function of Eo and depth below the surface. For all Eo, the subsurface beam diameter initially rapidly increased with SiO2 overlayer thickness but, for 150 keV, a leveling off in the beam spread was seen for depths >1.7 μm. Beam broadening affected whether the TaN/Ta liners that surrounded the Cu conductors could be seen at the edges of the lines; this contrast was observed only when the subsurface beam diameter was <=1.5× the liner thickness. The BSE information depth for imaging 0.2-μm-sized voids in subsurface Cu–SiO2–SiNx interconnect structures at 30 and 150 keV was estimated to be 0.65 and 3 μm, respectively. [ABSTRACT FROM AUTHOR]

Focuses on a study which investigated the properties of amorphous diamond films prepared by a filtered cathodic arc. Properties of carbon films; Details of the experiment; Characterization of the film.

Presents a study which examined the effects of process parameters in pulsed laser deposition of diamond-like carbon films on the film properties. Experimental procedure; Results; Discussion.

Presents information on a study which examined trends in reported data on high sp³ fraction, nonhydrogenated amorphous diamond-like carbon films deposited by ion beam sputtering and laser vaporization. Film properties; Evaporation of carbon by electron beam heating; Los-energy deposition mechanisms.

We developed an Al2O3/HfO2 bi-layer gate dielectric with an in-situ O3 treatment for interface state density (Dit) and gate leakage current density (Jg) reductions on SiGe channels. We observed Ge-content dependent equivalent oxide thickness (EOT) scaling and EOT 0.44 nm was achieved with an MOS capacitor with a Si0.05Ge0.95 substrate. The O3 treatment enabled application to non-planar device structures and we demonstrated five orders of magnitude lower off currents (IOFF), a sub-threshold slope of 68 mV/decade, and a very high hole mobility of 457 cm ^2\textV^\mathrm -1\texts^\mathrm -1 at an inversion carrier density (Ninv) of 1\times 10^13 cm ^\mathrm -2 for asymmetrically strained SiGe PMOSFETs with Ge% of 65%–70%. [ABSTRACT FROM PUBLISHER]

A correction to the article "Switching of ferroelectric polarization in epitaxial BaTiO3 films on silicon without a conducting bottom electrode" that was published in the September 29, 2013 issue is presented.

Atomic layer deposition (ALD) of epitaxial c-axis oriented BaTiO3 (BTO) on Si(001) using a thin (1.6nm) buffer layer of SrTiO3 (STO) grown by molecular beam epitaxy is reported. The ALD growth of crystalline BTO films at 225 °C used barium bis(triisopropylcyclopentadienyl), titanium tetraisopropoxide, and water as co-reactants. X-ray diffraction (XRD) reveals a high degree of crystallinity and c-axis orientation of as-deposited BTO films. Crystallinity is improved after vacuum annealing at 600 °C. Two-dimensional XRD confirms the tetragonal structure and orientation of 7-20-nm thick films. The effect of the annealing process on the BTO structure is discussed. A clean STO/Si interface is found using in-situ X-ray photoelectron spectroscopy and confirmed by cross-sectional scanning transmission electron microscopy. The capacitance-voltage characteristics of 7-20nm-thick BTO films are examined and show an effective dielectric constant of ~660 for the heterostructure. [ABSTRACT FROM AUTHOR]

The origins and the recent accomplishments of aberration correction in scanning transmission electron microscopy (STEM) are reviewed. It is remembered that the successful correction of imaging aberrations of round lenses owes much to the successful correction of spectrum aberrations achieved in electron energy loss spectrometers 2-3 decades earlier. Two noteworthy examples of the types of STEM investigation that aberration correction has made possible are shown: imaging of single-atom impurities in graphene and analyzing atomic bonding of single atoms by electron energy loss spectroscopy (EELS). Looking towards the future, a new all-magnetic monochromator is described. The monochromator uses several of the principles pioneered in round lens aberration correction, and it employs stabilization schemes that make it immune to variations in the high voltage of the microscope and in the monochromator main prism current. Tests of the monochromator carried out at 60 keV have demonstrated energy resolution as good as 12 meV and monochromated probe size of ˜1.2 Å. These results were obtained in separate experiments, but they indicate that the instrument can perform imaging and EELS with an atom-sized probe <30 meV wide in energy, and that an improvement in energy resolution to 10 meV and beyond should be possible in the future. [ABSTRACT FROM AUTHOR]

We investigate the determining mechanisms of the inversion-layer capacitance Cinv in the high-k/metal gate stacks, focusing on the two perturbative effects related with the dielectric properties. Those effects are the penetration of inversion-layer carriers into the dielectrics with a finite potential barrier and the image potential acting on the carriers adjacent to the dielectrics with permittivity different from that of the silicon substrate. The experimental and the theoretical analyses of the Cinv dependency on the crystal orientation of silicon substrates enable us to separate the two effects and to prove that the observed Cinv modulation in the high- k/metal gate stacks is attributable not to the image potential effect, but to the penetration effect. Moreover, we investigate the reduction of the total gate capacitance due to the Cinv in the advanced gate stacks scaled down to 0.66-nm equivalent oxide thickness. The influence of the elementary composition, the physical thickness, and the interface layer on a scaling loss due to the Cinv is experimentally evaluated. [ABSTRACT FROM AUTHOR]

The present study summarizes the effects of processing conditions and substrate cleaning procedures on the structure, chemistry and bonding of Cu/(0001)Al2O3 interfaces as determined by advanced transmission electron microscopy techniques. The Cu/(0001)Al2O3 samples were prepared by molecular beam epitaxy (MBE) and solid-state diffusion bonding. Investigations of the MBE samples showed that the Al2O3 cleaning procedure alters the interfacial bonding. Metallic bonds occurred for an Ar+ ion sputtering and subsequent ultra-high vacuum (UHV) annealing treatment. Strongly ionic–covalent bonds were found for a wet chemical cleaning process followed by UHV annealing. The interfacial electronic structure did not reveal any significant changes compared to the bulk electronic structure for samples where the substrate surface was annealed in an oxygen-containing atmosphere after Ar+ ion pre-sputtering and UHV annealing. The results obtained at the solid-state diffusion-bonded Cu/Al2O3 samples indicated that the processing parameters such as temperature and load do not change the bonding behavior. Post-annealing of the solid-state diffusion-bonded Cu/Al2O3 samples in a well-defined oxygen partial pressure led to the formation of CuAlO2 at the interface between Cu and Al2O3, which improved the adhesion. [ABSTRACT FROM AUTHOR]

The electron-energy-loss near-edge structure (ELNES ) of a Cu-alpha-Al2O3 interface grown by molecular beam epitaxy has been studied using spatial difference electron-energy-loss spectroscopy in the scanning transmission electron microscope. Interpretation of the interface-specific Cu L2,3, Al L2,3 O K ELNES components implies the existence of Cu-O bonding at the interface together with the retention of a local octahedral oxygen coordination of aluminium atoms and hence their non-participation in the interface plane. There is significant evidence for interfacial charge transfer from the copper layer to the oxygen layer, resulting in the existence of one monolayer of copper at the interface nominally in the Cu + oxidation state. Furthermore, the ELNES studies reveal that the interfacial Cu-O bonds are of mixed ionic-covalent character. This becomes apparent when considering the O K ELNES where the presence of hybridized Cu 3d-O 2p states is indicated. The basal plane of alpha-Al2O3 at the interface is terminated by a layer of oxygen atoms which is directly bonded to the copper lattice. This chemical information was employed as an initial assumption in the subsequent simulation of experimental high-resolution transmission electron microscopy (HRTEM ) images of the same interface. A structural model for the atomistic arrangement at the interface was derived which exhibited a projected Cu-O distance of 0.2 nm. Since the O K ELNES provides information on medium-range order, the HRTEM-derived model of the interface was then used as input for the simulation of the experimental interface-specific O K ELNES component using multiple-scattering calculations. Excellent agreement between the theoretical and experimental ELNES results confirms the HRTEM model and rules out the possibility of an aluminium-terminated alpha-Al2O3 basal plane at the interface. This study attempts to demonstrate the synergism between HRTEM and spatially resolved electron-energy-loss spectroscopy measurements for structure determination and highlights the self-consistent aspect of such combined information. [ABSTRACT FROM AUTHOR]

The need for an analytical electron microscope (AEM) characterization standard capable of determining the consistency and relative quality of analytical performance has become increasingly evident as advances in the instrumentation are made. In this paper the fabrication of a Cr thin-film AEM standard by conventional thermal evaporation techniques is described. A 100-nm-thick Cr film on a 20-nm C-support film provided by the National Institute of Standards and Technology (NIST) served as a model against which the present film was evaluated. Improvements over the NIST film in terms of diffraction pattern clarity and simplification of parallel electron energy-loss spectrometry (PEELS) analysis were achieved by removal of the C-support film and the creation of a self-supported Cr (SS-Cr) film. Qualitative grain-size comparisons between the NIST model and the SS-Cr films made by scanning transmission electron microscopy found the SS-Cr films to have a slightly larger grain size. Thickness measurements were verified by X-ray energy dispersive spectrometry, PEELS and field-emission gun scanning electron microscopy. SS-Cr film standard specimens are available for use by the AEM community, by contacting the authors directly. [ABSTRACT FROM AUTHOR]

Origins of effective work function (EWF) roll-off behavior accompanied by equivalent oxide thickness (EOT) scaling for high- κ last replacement metal gate (RMG) stacks are investigated using a low-temperature interfacial layer (IL) scavenging technique. The EWF-EOT roll-off is driven by a high work function metal and the trend is linear and reversible by means of IL scavenging and regrowth reactions. These findings are consistent with the oxygen vacancy model, indicating that the same mechanism that plagued gate-first devices emerges as the IL thickness is scaled <; 4 Å (EOT 8 Å) for RMG stacks. [ABSTRACT FROM AUTHOR]

The benefit of La–Al–O higher-k gate dielectrics is maximized by optimizing the Al/(La+Al) atomic ratio. The Al/(La+Al) atomic ratio modulates the band gap, dielectric constant, and interface dipoles, resulting in change of energy band alignment. The La–Al–O film with an Al/(La+Al) atomic ratio of 0.25 yields a maximum leakage current reduction exceeding \HfO2 and \La2\O3, owing to the optimized band alignment structure. Moreover, a SiON underlayer instead of \SiO2 enables additional equivalent oxide thickness scaling down to 7.4 Å while maintaining the fully reduced leakage current with a gate-first process. [ABSTRACT FROM PUBLISHER]

Studies sputter deposition of dense diamond-like carbon films at low temperature. Use of Rutherford backscattering spectrometry and electron energy loss spectroscopy; Trends in film density and bonding.