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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 $^{2}\text{V}^{\mathrm {-1}}\text{s}^{\mathrm {-1}}$ at an inversion carrier density (Ninv) of $1\times 10^{13}$ cm $^{\mathrm {-2}}$ for asymmetrically strained SiGe PMOSFETs with Ge% of 65%–70%.

We report InGaAs gate-all-around nanosheet NFETs on Si substrate using template-assisted-selective-epitaxy (TASE) and a gate-last process with thermal budget advantages. Compared to our early report of the TASE process, in this paper we demonstrate that TASE can be scaled to a channel thickness of ∼10 nm, which enables short gate devices without significant leakage. The defects and composition of the fabricated nanosheet FETs are also investigated. Enabled by this VLSI compatible process and a novel high-pressure deuterium annealing process, our 39 nm- $L_{g}$ device shows a peak $g_{m}$ of $1.37 \ \text{mS}/\mu \mathrm{m}$ , a subthreshold slope in saturation of 72 mV/decade, and an $I_{on}$ of $355 \ \mu \mathrm{A}/\mu \mathrm{m}$ at 0.5 V $V_{gs}$ , the highest among reported sub-50 nm- $L_{g}$ III-V FETs on Si.

Electromigration and resistivity of Cu, Co and Ru on-chip interconnection have been investigated. A similar resistivity size effect increase was observed in Cu, Co, and Ru. The effect of liners and cap, e.g. Ta, Co, Ru and SiC x N y H z , on Cu/interface resistivity was not found to be significant. Multilevel Cu, Co or Ru back-end-of-line interconnects were fabricated using 10 nm node technology wafer processing steps. EM in 22 nm to 88 nm wide Co lines, 24 nm wide Cu with and without a thin Co cap and 24 nm wide Ru lines were tested. These data showed that Cu with a Co cap, Co and Ru had highly reliable EM, although Ru was better than Co and Co was better Cu. The electromigration activation energies for Cu with Co cap and Co were found to be 1.5–1.6 eV and 2.1–2.7 eV, respectively.

Lanthanum aluminate (LAO) films were grown epitaxially on Si (001) by atomic layer deposition (ALD) using a buffer layer of strontium titanate (STO) grown by molecular beam epitaxy. The ALD growth of LAO was done at 250 °C by using tris(N,N′-diisopropylformamidinate)–lanthanum, trimethylaluminum, and water as co-reactants. Reflection high-energy electron diffraction, X-ray diffraction and transmission electron microscopy were used to determine film crystallinity. The as-deposited LAO films were amorphous and became crystalline after vacuum annealing at 600 °C for 2 h. In-situ X-ray photoelectron spectroscopy (XPS) was used to characterize the LAO/STO/Si interfaces at various stages throughout the growth and annealing process. XPS analysis showed minimal SiO bonding at the STO/Si interface after the ALD process and after post-deposition annealing at 600 °C for 2 h. The results demonstrate a method to integrate epitaxial LAO films on Si (001) substrates by ALD.

As semiconductor device scaling continues to reduce the structure size, device geometries are also changing to three dimensional structures such as finFETs, and the materials which compose the devices are also evolving to obtain additional device performance gains. The material change studied in this paper is the introduction of silicon germanium into the electrically active region of a finFET test structure. The paper demonstrates a quantitative energy dispersive X-ray spectroscopy transmission electron microscopy (TEM) technique through the use of blanket film calibration samples of known concentration characterized by X-ray diffraction. The technique is used to identify a test structure issue which could only be diagnosed with a technique having nanometer spatial resolution and atomic percent sensitivity. The results of the test structure analysis are independently verified by the complementary TEM electron energy loss spectroscopy technique.

High-spatial-resolution analytical electron microscopy using energy-dispersive X-ray (EDX) and electron energy-loss spectrometry (EELS) of yttrium- and lanthanum-doped Al2O3 has been conducted to ascertain the level of segregation of these impurities to grain boundaries. Line profile analyses indicate that the segregation is confined to a layer thickness of

SUMMARY To extract quantitative electronic structure information from electron energy-loss near-edge structure typically necessitates the separation of spectra into linearly independent components. For this to be accomplished, certain conditions need to be met concerning the localization of chemical bonding and the linear scaling of fine structure with density of states. The dependence of the processing parameters, such as window widths and positions, of the commonly used ‘two-window intensity-ratio’ method to determine the distribution of π and σ bonding of diamond-like carbon films is investigated. It is shown that, although the selection of the integration windows can lead to very large variations in the resultant bonding fractions, the placement of two small windows centred on the edge structures of interest does permit a robust and reliable estimate of bonding. It is demonstrated that the sp3 variations can be reproducibly monitored with a relative accuracy of about ± 5%, and an absolute concentration given with an accuracy of ± 13% for foils of thickness at least up to twice the inelastic mean free path.

Amorphous diamond films have been prepared by filtered cathodic arc deposition of carbon. The filtered arc is well suited for the growth of amorphous diamond, as it provides carbon ions with optimum kinetic energies at practical deposition rates. These films contain no hydrogen and are therefore structurally different from diamond‐like carbon films generated by plasma chemical vapor deposition. Diamond‐type bonding of carbon is quantitatively determined by electron energy loss spectroscopy, as an sp3 content up to 83% is measured. Data on the macroscopic properties are provided by optical transmittance, ellipsometry, Rutherford backscattering, elastic recoil scattering, and resistivity measurements. The films exhibit high optical transparency and an optical gap of 2.4 eV. Trends in the optical gap and refractive index as a function of deposition energy are consistent with semiconductor theory and indicates a change in the average bond length.

Spatially resolved electron energy-loss spectroscopy has been used to interrogate the chemistry and bonding at grain boundaries in hot isostatically pressed (HIPed) high purity silicon nitride ceramics nominally doped with either 0, 100, 300 or 500 at. ppm calcium. Analysis of the nanometer thick glassy films between grains, shows that there is a monotonic increase in impurity segregation with dopant concentration. The predominant constituents of the grain boundary films are Si, O and N, forming a silicon oxynitride phase ranging in composition from SiO 2 to Si 2 N 2 O. The energy-loss near-edge structure indicates the structure of the glass is composed predominantly of tetrahedra but also suggests the presence of a small concentration of molecular N 2 , possibly as sub-microscopic bubbles. There is still no data on the composition gradients on a sub-nanometer level, though it is shown that in the detection limit set by counting statistics, near single atom sensitivity with a spatial resolution of 0.22 nm is achievable.

High-resolution electron microscopy and nano-beam analytical electron microscopy have been used to characterize both the intergranular silicate film thickness and its local composition in a series of high-purity Si3N4 ceramics doped with 0–450 at. ppm Ca. Calcium was detected at both two-grain junctions and triple junctions, even in the 80-ppm-Ca-doped specimen. The thickness of the intergranular film at two-grain junctions was found to depend sensitively on Ca content. In undoped material, the thickness was 1.0 ± 0.1 nm. With increasing Ca content, the thickness decreased in the dilute region (80 ppm Ca), but then increased. The variation in film thickness can be qualitatively understood in terms of the balance of three long-range forces acting normal to the film, namely the van der Waals dispersion force, a structural “steric” force, and an electrical-double-layer force. By comparing the measured thicknesses to those predicted, estimates for the structural correlation length and the inverse Debye length can be made. These estimates have values of ∼ 0.22 nm and approximately 0.3–0.5 nm, respectively, for the calcia-free and 80 ppm calcia materials.

We demonstrate the potential for ultrathin aluminum-oxide films as alternate gate dielectrics for Si complementary metal–oxide–semiconductor technology. Films are deposited in ultrahigh vacuum utilizing atomic beams of aluminum and oxygen on Si(100) surfaces. We show device-quality Si(100)/Al2O3 interfaces with interfacial trap densities in the 1010 cm−2 eV−1 range, and with leakage current densities five orders of magnitude lower than what is observed in SiO2 insulators at the same equivalent electrical thickness. As-grown films possess an amorphous-to-microcrystalline structure, depending upon the deposition temperature, and any interfacial layers between the Si(100) and Al2O3 layer are

Carbon thin films have been prepared by 248 nm excimer laser vaporization of graphite targets. The effect of a variety of process parameters on the film properties is investigated. Deposition at or below room temperature yields diamond‐like films with low hydrogen content, high optical transmission, and high resistivity. Electron energy loss spectra indicate sp3 bond fractions of 70–85%. Detailed analyses of the pseudodielectric functions, measured using spectroscopic ellipsometry, show the films to have normal dispersion and an index of refraction of 2.5 in the visible wavelength region. The effects of a low pressure hydrogen background and the use of auxiliary pulsed and dc plasma enhancements are also examined.

Thin films of carbon have been deposited at temperatures ranging from 77 to 1073 K. It has been found that diamond‐like properties of the films change with the deposition temperature and the thermal conductivity of the substrate. Densities as high as 2.9 g/cc with an sp3 bond content >40% have been observed. Substrates that have been investigated include graphite, NaCl, Si, Al2O3, fused quartz, and diamond. Density measurements have been made using Rutherford backscattering spectrometry and electron‐energy‐loss spectroscopy while hydrogen profiling was conducted using forward recoil spectrometry.

A process to deposit in situ a dual electron injector structure (DEIS) with 5‐nm SiO2 between two Si‐rich SiO2 (SRO) layers of ∼20 nm each has been developed. The excess silicon, as evaluated by Auger spectroscopy and Rutherford backscattering, was of the order of 15%–17%, in agreement with previously reported values under similar deposition conditions. Thin cross‐sectioned samples of DEIS structures, both as‐deposited and annealed at 1000 °C with Ar in an oxygen and water‐moisture‐free atmosphere, were examined by spatially resolved energy‐loss spectroscopy (EELS) in a scanning transmission electron microscope. The analysis has shown that the excess silicon is present either as nanometer‐sized silicon islands or as submicroscopic silicon oxides of varying stoichiometry resulting from intermediate oxidation states (i.e., Si+3, Si+2, and Si+1). Additionally, the thermal anneal at 1000 °C did not appear to have any effect on silicon island size of the SRO layer in contact with the silicon substrate. This su...

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 5 min 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 ...

Atomic layer deposition (ALD) of epitaxial c-axis oriented BaTiO3 (BTO) on Si(001) using a thin (1.6 nm) 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 7–20 nm-thick BTO films are examined and show an effective dielectric constant of ∼660 for the heterostructure.

Thin carbon films were deposited by ion beam sputtering at temperatures of 77–1073 K. Using Rutherford backscattering spectrometry and electron energy loss spectroscopy, the trends in film density and bonding were examined as a function of deposition conditions. It has been found that film density and sp3 bonding character unexpectedly increased with increased substrate thermal conductivity and decreasing substrate temperature, reaching values of 2.9 g/cc and 50%, respectively.

Detailed analysis of a buried layer of GaAs in 〈100〉 Si was carried out using electron energy loss spectroscopy, Rutherford backscattering spectroscopy, and ion channeling. The layer was formed by 200 keV dual ion implantation of Ga plus As ions, followed by furnace annealing at 600 and 950 °C. It consists of GaAs particles which are surrounded by fully recrystallized silicon. Beneath it is a dislocation network, made up of a mixture of edge and screw dislocations.

Radioactive tracer diffusion data is presented which illustrates some of the more interesting questions that need to be further understood. For example, in Al, Cu and Au alloys, solute decreases the activation energy, Ql, for lattice diffusion while increasing Qb for boundary diffusion in the same test samples. Secondly, this is true only for diffusion in the alloy itself; for example, Qb for Cu in pure Al boundaries is 0.4 eV while for Cu in All%Cu alloy boundaries is 0.73 eV. Also, for Qb, Sn in pure Cu is 0.8 eV, Cu in pure Cu is 0.92 eV, but in the Cu2%Sn alloy Sn is 1.2 eV and Cu 1.39 eV quite substantial changes. Of note is the observation that solute atomic size does not appear to be the deciding feature. The systems selected for study represent smaller, larger and similar solute size for Cu in Al, Sn in Cu and Ta in Au, respectively. Preliminary work has been accomplished on measuring the electron energy loss (EELS) of Cu in Al2%Cu grain boundaries, specifically to observe the electronic structure...

Using density functional theory, we analyze the wetting conditions for Pt on the (001) surface of ferroelectric BaTiO3 (BTO). We estimate the surface energy of (100), (110), and (111) Pt to be 2.42, 2.49, and 2.00 J/m2, respectively. We find the BTO surface energy to vary between 0.26 and 2.28 J/m2 depending on termination, polarization, and chemical environment. The interface energy between TiO2-terminated out-of-plane polarized BTO and (100) Pt is found to be between 1.64 and 2.62 J/m2, indicating that (100) Pt cannot wet BTO for this interface. A similar result is found for an interface with (110) Pt. Cross-sectional transmission electron microscopy of Pt films grown on BTO by molecular beam epitaxy with a low flux at high deposition temperature shows Volmer-Weber islands, consistent with first principles calculations.

Yttrium lanthanum silicate was formed in direct contact with silicon after a rapid thermal annealing at 1000 °C in metal-oxide-semiconductor capacitors leading to an equivalent oxide thickness (EOT) of 7.7 A. This represents one of the lowest EOT value reported for a gate-first process with non Hf-based dielectric. The silicate is formed by interdiffusion of La2O3 and YOx layers and interfacial SiO2 consumption. Yttrium incorporation reduces the leakage current density as well as the large negative flatband voltage (Vfb) shift that is associated with lanthanide-based dielectrics. The Vfb value can be appropriately tuned for n-type field-effect transistor operation by changing the silicate composition.

LaxLu1−xO3 thin films were deposited on 300 mm silicon wafers by physical vapor deposition and fabricated into field-effect transistors using a gate-first process flow. The films were characterized using transmission electron microscopy, Rutherford backscattering spectrometry, and synchrotron x-ray diffraction. The results show the films remain amorphous even at temperatures of 1000 °C. The dielectric properties of LaxLu1−xO3 (0.125≤x≤0.875) thin films were evaluated as a function of film composition. The amorphous LaxLu1−xO3 thin films have a dielectric constant (K) of 23 across the composition range. The inversion thickness (Tinv) of the LaxLu1−xO3 thin films was scaled to

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 A 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 inter...

Distribution and migration of oxygen in the highk/metal gate stack has a strong impact on the CMOS transistor electrical characteristics. Excess O can cause interlayer (IL) growth and subsequent increase of Equivalent Oxide Thickness (EOT), whereas O-vacancies induced by the metal gate contact may lead to unpredictable and feature size dependent shifts in threshold voltage (Vt). In addition to these phenomena, we have recently described a new migration pathway for O in poly-Si/TiN/TiO2-based high-k/stacks [1]. Besides re-growth of the bottom IL, excess O –released by the thermal decomposition of TiO2-based high-k stacks upon annealing– was observed to diffuse upwards, resulting in SiO2 growth at the TiN/poly-Si interface, as evidenced by regular SIMS analysis following the O main isotope. Here, we have employed SIMS depth profiling in combination with isotopic labeling –using minority Oisotope– to characterize the migration and/or redistribution of O in the high-k metal gate stack (HK/MG) at different stages of processing. Firstly, the creation of vacancy defects in high-k dielectrics –induced by the TiN-based metal gate contact upon high temperature annealing– is the most probable cause for large (~500 meV) Vt shifts, which is especially problematic for pFET devices. We have demonstrated that these shifts can be largely recovered after a lowtemperature low-pressure top-down oxygenation step on TiN metal gate exposed by poly-Si removal, while preventing excessive oxidation of TiN and parasitic IL regrowth [2]. Using SIMS, we have systematically investigated the incorporation of O by SIMS for different temperatures and TiN thicknesses on TiN-gated high-k films, subjected to top-down oxygenation with isotopic labeled O2, see Figure 1. We have thus established that incorporated O-doses –needed to remove the defects created in a metal-HfO2 contact– amount 1.4e14 to 3.9e14 at.cm. In addition, O-profiles after top-down oxidation show a small but significant shift with respect to pre-existing O towards the TiN-interface (see inset Figure 1). This implies that passivation of vacancies preferentially occurs in the top portion of the high-k layer, consistent with negligibly small oxide (IL) re-growth. Secondly, remote O-scavenging from the SiO2 interlayer (IL) using a poly-Si/doped TiN metal gate stack is a promising technique to achieve aggressive EOT scaling in a gate-first flow, compliant with 16 nm technology node requirements [3]. The remote scavenging mechanism is based on the presence of a metallic element M, inserted in the TiN metal gate at a certain separation from the high-k interface. This scavenging element is capable of scavenging O from the SiO2 IL upon poly activation anneal, as evidenced by TEM and conventional O-SIMS. Here, we have employed SIMS to determine the kinetics of O-scavenging from Hf-based high-k dielectric –enriched in O by isotopic exchange after high-k deposition upon low-temperature O2 exposure– towards M-TiN alloy for different annealing temperatures and IL’s. Use of an O-isotope enriched high-k layer allows following of O-redistribution through scavenging and isotopic exchange for different annealing temperatures, see Figure 2. This approach has revealed a subtle effect of IL composition on remote O-scavenging kinetics. In addition, rapid isotopic exchange between the different interfaces through the TiN metal gate is seen to occur upon high temperature anneal, indicating rapid Odiffusion in these stacks. These examples demonstrate the benefits of using O isotope labeling for SIMS analysis to resolve small quantities of O and to obtain fundamental knowledge on oxygen transport in high-k metal gate stacks.

We present evidence for the instability in the crystalline (metallic) state of binary Te-free phase-change Ge–Sb thin films considered for integration into nonvolatile nanosized memory cells. We find that while the amorphous (semiconducting) phase of eutectic Sb–15at.% Ge is very robust until Sb crystallization at 240°C, at about 350°C, germanium rapidly precipitates out. Ge precipitation, visualized directly with transmission electron microscopy, is exothermic and is found to affect the films’ reflectivity, resistance, and stress. It converts melting into a two-step process, which may seriously impact the switching reliability of a device.