We report on the stabilization of ferroelectric HfxZr1−xO2 (HZO) films crystallized using a low thermal budget millisecond flash lamp annealing technique. Utilizing a 120 s 375 °C preheat step combined with millisecond flash lamp pulses, ferroelectric characteristics can be obtained which are comparable to that achieved using a 300 s 650 °C rapid thermal anneal. X-ray diffraction, capacitance voltage, and polarization hysteresis analysis consistently point to the formation of the ferroelectric phase of HZO. A remanent polarization (Pr) of ∼21 μC/cm2 and a coercive field (Ec) of ∼1.1 MV/cm are achieved in 10 nm thick HZO layers. Such a technique promises a new alternative solution for low thermal budget formation of ferroelectric HZO films.

The metallization of integrated circuits for high performance CMOS devices involves the use of copper with low-k or ultra low-k dielectrics to reduce RC delay and cross talk in devices. For the 90nm to 14 nm CMOS device nodes, conventional silicon nitride was replaced by new dielectric barrier low k materials such as SiCN, C-Rich SiCN and SiNO (1-6). As devices scale down to <=10 nm dimension, further reduction in cap thickness is required for the Cu barrier while maintaining sufficient mechanical strength, low leakage, high dielectric breakdown, and fabrication integration robustness. In a previous report (6), we showed that a single layer SiCN x film deposited by plasma enhanced CVD with TMS+NH 3 is still robust down to around 15-20 nm thickness range. This paper presents the development of the second generation robust Low Hydrogen SiCN to enable cap thickness reduction to <=10 nm by simply altering/reducing the hydrogen concentration in the SiCN film composition. EXPERIMENT The low hydrogen SiCN x films were deposited in a commercial high throughput production worthy 13.6 MHz RF 300 mm Plasma Chemical Vapor Deposition process (PECVD) system at 350 C using a combination of Trimethyl Silane (TMS) + Ammonia (NH 3 ) + Hydrogen precursors with excellent uniformity (1 sigma < 1 %). The as-deposited films were analyzed using various electrical , mechanical and chemical analyses to study the film's properties and compositions, Table 1. An oxidation resistance test (6) was done after the barrier film/copper blanket stack was annealed at 310°C for 24 hours in ambient atmosphere. Multi-level 7nm copper interconnect structures were built for Electro-migration (EM) and Time Dependent Dielectric Breakdown (TDDB) reliability measurement (150-300°C). RESULTS and DISCUSSION Table 1 summarizes SiCN and Low H SiCN cap film properties and device performance. Overall, the low H SiCN cap has better electrical, mechanical, and device reliability performance than the standard SiCN cap. The low H SiCN film has higher density, modulus, hardness and significantly higher compressive stress, both as-deposited and post 5 minutes direct UV cure. Compositional analysis shows that PECVD SiCNx cap films deposited with the addition of hydrogen precursor actually have less hydrogen than films deposited without hydrogen under the same optimized deposition condition. Film deposition rates decrease slightly at higher hydrogen flow rate in the TMS+NH 3 +H 2 precursor chemistry. The reduced deposition rate and the hydrogen reduction in the film’s bulk are attributed to the increase removal (etching) of weakly bonded -Si-H x and -N-H y species in the film during the plasma deposition process. FTIR analysis shows that Si-C and Si-N bonding density increases in the low H SiCN dielectric, which is consistent with the increase in film density, modulus and harness. A minor reduction in the dielectric constant, similar breakdown voltage and reduced leakage are observed for the low H SiCN cap. Figure 1 shows a typical Scanning Transmission Electron Micrograph (STEM) of a 3nm Co/10 nm Low H SiCN cap on a Copper Metal2 7nm interconnect structure. This Cu/Co/Low H SiCN x cap structure achieves 4-10X better EM/TDDB reliability versus a similar structure with the standardcap (Table 1). A Scanning Electron Micrograph (SEM) of the patterned surface after annealing at 310°C for 24 hours in ambient atmosphere (Figure 1) shows that the 10 nm Low H SiCN cap has excellent Cu Oxidation properties with no sign of Cu Oxidation. CONCLUSIONS Low hydrogen SiCN dielectrics with improved mechanical, oxidation and Cu diffusion barrier properties versus standard SiCN were deposited using TMS, NH 3 and H 2 . The new robust low hydrogen SiCN dielectric cap film showed a significant increase in Si-C and Si-N bonding density and a reliability performance improvement in 7 nm Cu interconnect structures at <=10 nm thickness . This enables significant improvement in capacitance, reliability and Cu_low k nano device performance. Acknowledgment This work was performed by the Research Alliance Teams at various IBM Research and Development Facilities. The author would like to thank B. Peethala for some analysis and A. Grill for discussion. REFERENCES [1] L. Xia, M. Naik, H. Xu, V. Zubkov, R. Bhatia, C. Peterson, M. Spuller, and H. M’Saad, Proceeding of Advanced Metallization for Devices and Circuits, (2006) pp. 169. [2] S.G. Lee et al, Jpn. J. Appl. Phys ., 40 , 2663 (2001). [3] Al Grill, Steve Gate, Son Nguyen, D. Priyadarshin, E Tood Ryan; Appl. Phys. Rev. 1, 011306 (2014). [4] Son V. Nguyen et al., Electrochem. Soc. Transaction 2014, Volume 61, issue 3, pp.17-28 . [5] C.Yang et al., IEEE Electron Device Letter, Vol 33, No, 4, pp.588-560 (2012). [6] Son Nguyen et al., Electrochem. Soc. Transaction. 2010, Volume: 33, Issue: 12, pp.137-145. Figure 1

As integrated circuits for high performance CMOS devices scale down to <= 10 nm dimension, further reductions in cap thickness to reduce capacitance are required for the Cu barrier while maintaining sufficient mechanical strength, low leakage, high dielectric breakdown, and fabrication integration robustness. This paper presents the development of a second generation robust low-hydrogen SiCN films to enable cap thickness reduction to <= 10 nm by simply altering/reducing the hydrogen concentration in the SiCN film. This is achieved by the simple addition of hydrogen precursor in the plasma deposition chemistry. (C) The Author(s) 2017. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. All rights reserved.

The origin of spin-orbit torques, which are generated by the conversion of charge-to-spin currents in non-magnetic materials, is of considerable debate. One of the most interesting materials is tungsten, for which large spin-orbit torques have been found in thin films that are stabilized in the A15 (β-phase) structure. Here we report large spin Hall angles of up to approximately -0.5 by incorporating oxygen into tungsten. While the incorporation of oxygen into the tungsten films leads to significant changes in their microstructure and electrical resistivity, the large spin Hall angles measured are found to be remarkably insensitive to the oxygen-doping level (12-44%). The invariance of the spin Hall angle for higher oxygen concentrations with the bulk properties of the films suggests that the spin-orbit torques in this system may originate dominantly from the interface rather than from the interior of the films.

We report the structural, electronic, and magnetic study of Cr-doped Sb2Te3 thin films grown by a two-step deposition process using molecular-beam epitaxy (MBE). The samples were investigated using a variety of complementary techniques, namely, x-ray diffraction (XRD), atomic force microscopy, SQUID magnetometry, magneto-transport, and polarized neutron reflectometry (PNR). It is found that the samples retain good crystalline order up to a doping level of (in CrxSb2−xTe3), above which degradation of the crystal structure is observed by XRD. Fits to the recorded XRD spectra indicate a general reduction in the c-axis lattice parameter as a function of doping, consistent with substitutional doping with an ion of smaller ionic radius. The samples show soft ferromagnetic behavior with the easy axis of magnetization being out-of-plane. The saturation magnetization is dependent on the doping level, and reaches from to almost per Cr ion. The transition temperature depends strongly on the Cr concentration and is found to increase with doping concentration. For the highest achievable doping level for phase-pure films of , a of 125 K was determined. Electric transport measurements find surface-dominated transport below ∼10 K. The magnetic properties extracted from anomalous Hall effect data are in excellent agreement with the magnetometry data. PNR studies indicate a uniform magnetization profile throughout the film, with no indication of enhanced magnetic order towards the sample surface.

The growth of Co-substituted BaTiO3 (BTO) films on Ge(001) substrates by molecular beam epitaxy is demonstrated. Energy-dispersive x-ray spectroscopy and transmission electron microscopy images confirm the uniform Co distribution. However, no evidence of magnetic ordering is observed in samples grown for Co concentrations between 2% and 40%. Piezoresponse force microscopy measurements show that a 5% Co-substituted BTO sample exhibits ferroelectric behavior. First-principles calculations indicate that while Co atoms couple ferromagnetically in the absence of oxygen vacancies, the occurrence of oxygen vacancies leads to locally antiferromagnetically coupled complexes with relatively strong spin coupling. The presence of a significant amount of oxygen vacancies is suggested by x-ray photoelectron spectroscopy measurements.

Breaking time-reversal symmetry through magnetic doping of topological insulators has been identified as a key strategy for unlocking exotic physical states. Here, we report the growth of Bi2Te3 thin films doped with the highest magnetic moment element Ho. Diffraction studies demonstrate high quality films for up to 21% Ho incorporation. Superconducting quantum interference device magnetometry reveals paramagnetism down to 2 K with an effective magnetic moment of ∼5 μB/Ho. Angle-resolved photoemission spectroscopy shows that the topological surface state remains intact with Ho doping, consistent with the material's paramagnetic state. The large saturation moment achieved makes these films useful for incorporation into heterostructures, whereby magnetic order can be introduced via interfacial coupling.

Breaking the time-reversal symmetry (TRS) in topological insulators (TIs) through ferromagnetic doping is an essential prerequisite for unlocking novel physical phenomena and exploring potential device applications. Here, we report the successful growth of high-quality (Dy(x)Bi(1-x))2Te3 thin films with Dy concentrations up to x = 0.355 by molecular beam epitaxy. Bulk-sensitive magnetisation studies using superconducting quantum interference device magnetometry find paramagnetic behaviour down to 2 K for the entire doping series. The effective magnetic moment, μeff, is strongly doping concentration-dependent and reduces from ∼12.6 μ(B) Dy(-1) for x = 0.023 to ∼4.3 μ(B) Dy(-1) for x = 0.355. X-ray absorption spectra and x-ray magnetic circular dichroism (XMCD) at the Dy M4,5 edge are employed to provide a deeper insight into the magnetic nature of the Dy(3+)-doped films. XMCD, measured in surface-sensitive total-electron-yield detection, gives μ(eff )= 4.2 μ(B) Dy(-1). The large measured moments make Dy-doped films interesting TI systems in which the TRS may be broken via the proximity effect due to an adjacent ferromagnetic insulator.

The breaking of time reversal symmetry (TRS) in three-dimensional (3D) topological insulators (TIs), and thus the opening of a 'Dirac-mass gap' in the linearly dispersed Dirac surface state, is a prerequisite for unlocking exotic physical states. Introducing ferromagnetic long-range order by transition metal doping has been shown to break TRS. Here, we present the study of lanthanide (Ln) doped Bi2Te3, where the magnetic doping with high-moment lanthanides promises large energy gaps. Using molecular beam epitaxy, single-crystalline, rhombohedral thin films with Ln concentrations of up to ~35%, substituting on Bi sites, were achieved for Dy, Gd, and Ho doping. Angle-resolved photoemission spectroscopy shows the characteristic Dirac cone for Gd and Ho doping. In contrast, for Dy doping above a critical doping concentration, a gap opening is observed via the decreased spectral intensity at the Dirac point, indicating a topological quantum phase transition persisting up to room-temperature.

Materials with layered van der Waals crystal structures are exciting research topics in condensed matter physics and materials science due to outstanding physical properties associated with their strong two dimensional nature. Prominent examples include bismuth tritelluride and triselenide topological insulators (TIs), which are characterized by a bulk bandgap and pairwise counter-propagating spin-polarized electronic surface states. Angle-resolved photoemission spectroscopy (ARPES) of ex-situ grown thin film samples has been limited by the lack of suitable surface preparation techniques. We demonstrate the shortcomings of previously successful conventional surface preparation techniques when applied to ternary TI systems which are susceptible to severe oxidation. We show that in-situ cleaving is a simple and effective technique for preparation of clean surfaces on ex-situ grown thin films for high quality ARPES measurements. The method presented here is universally applicable to other layered van der Waals systems as well.

Several attractive applications call for the organization of memristive devices (or other resistive non-volatile memory (NVM)) into large, densely-packed crossbar arrays. While resistive-NVM devices frequently possess some degree of inherent nonlinearity (typically 3-30x contrast), the operation of large (> 1000x1000 device) arrays at low power tends to require quite large (> 1e7) ON-to-OFF ratios (between the currents passed at high and at low voltages). One path to such large nonlinearities is the inclusion of a distinct access device (AD) together with each of the state-bearing resistive-NVM elements. While such an AD need not store data, its list of requirements is almost as challenging as the specifications demanded of the memory device. Several candidate ADs have been proposed, but obtaining high performance without requiring single-crystal silicon and/or the high processing temperatures of the front-end-of-the-line-which would eliminate any opportunity for 3D stacking-has been difficult. We review our work at IBM Research-Almaden on high-performance ADs based on Cucontaining mixed-ionic-electronic conduction (MIEC) materials [1-7]. These devices require only the low processing temperatures of the back-end-of-the-line, making them highly suitable for implementing multi-layer cross-bar arrays. MIEC-based ADs offer large ON/OFF ratios (> 1e7), a significant voltage margin V m (over which current < 10 nA), and ultra-low leakage (< 10 pA), while also offering the high current densities needed for phase-change memory and the fully bipolar operation needed for high-performance RRAM. Scalability to critical lateral dimensions < 30 nm and thicknesses < 15 nm, tight distributions and 100% yield in large (512 kBit) arrays, long-term stability of the ultra-low leakage states, and sub-50 ns turn-ON times have all been demonstrated. Numerical modeling of these MIEC-based ADs shows that their operation depends on Cu+ mediated hole conduction. Circuit simulations reveal that while scaled MIEC devices are suitable for large crossbar arrays of resistive-NVM devices with low (< 1.2 V) switching voltages, stacking two MIEC devices can support large crossbar arrays for switching voltages up to 2.5 V.

Tantalum nitride (TaNx) amorphous thin films with varying nitrogen content were grown on SiO2/Si using ionized physical vapor deposition. The composition of the films was examined by Rutherford back scattering spectrometry. The carrier density and the resistivity of TaNx films were measured by Hall effect and Van Der Pauw's method. TaNx thin films showed increased electrical resistivity and reduced carrier density as the amount of nitrogen was increased. By controlling the nitrogen content, the carrier density can be tuned within a large range of 1019–1022 cm−3 for 3 and 15 nm thick TaNx films. The metallicity of the films was confirmed using ultraviolet photoemission spectroscopy. For 3 nm thick TaNx films, carrier densities of ∼1021 cm−3 were obtained with the N2 flow rate in the range of 10–15 sccm. Such films have potential application in a quantum metal field effect transistor.

We report the structural and magnetic study of Cr-doped Bi2Se3 thin films using x-ray diffraction (XRD), magnetometry and polarized neutron reflectometry (PNR). Epitaxial layers were grown on c-plane sapphire by molecular beam epitaxy in a two-step process. High-resolution XRD shows the exceptionally high crystalline quality of the doped films with no parasitic phases up to a Cr concentration of 12% (in % of the Bi sites occupied by substitutional Cr). The magnetic moment, measured by SQUID magnetometry, was found to be per Cr ion. The magnetic hysteresis curve shows an open loop with a coercive field of . The ferromagnetic transition temperature was determined to be analyzing the magnetization-temperature gradient. PNR shows the film to be homogeneously ferromagnetic with no enhanced magnetism near the surface or interface.

We report the growth of Mn-doped Bi2Se3 thin films by molecular beam epitaxy (MBE), investigated by x-ray diffraction (XRD), atomic force microscopy (AFM), SQUID magnetometry and x-ray magnetic circular dichroism (XMCD). Epitaxial films were deposited on c-plane sapphire substrates by co-evaporation. The films exhibit a spiral growth mechanism typical of this material class, as revealed by AFM. The XRD measurements demonstrate a good crystalline structure which is retained upon doping up to ∼7.5 atomic-% Mn, determined by Rutherford backscattering spectrometry (RBS), and show no evidence of the formation of parasitic phases. However an increasing interstitial incorporation of Mn is observed with increasing doping concentration. A magnetic moment of 5.1 μB/Mn is obtained from bulk-sensitive SQUID measurements, and a much lower moment of 1.6 μB/Mn from surface-sensitive XMCD. At ∼2.5 K, XMCD at the Mn L2,3 edge, reveals short-range magnetic order in the films and indicates ferromagnetic order below 1.5 K.

We report on the controlled removal of an amorphous Se capping layer from Bi2Te3 and Bi2Se3 topological insulators. We show that the Se coalesces into micron-sized islands before desorbing from the surface at a temperature of ∼150 °C. In situ Auger Electron Spectroscopy reveals that Se replaces a significant fraction of the Te near the top surface of the Bi2Te3. Rutherford Backscattering Spectrometry and Transmission Electron Microscopy show that after heating, Se has been incorporated in the Bi2Te3 lattice down to ∼7 nm from its top surface while remaining iso-structural.

The structural, optical, and room-temperature electrical properties of strained La-doped SrTiO3 epitaxial thin films are investigated. Conductive La-doped SrTiO3 thin films with concentration varying from 5 to 25% are grown by molecular beam epitaxy on four different substrates: LaAlO3, (LaAlO3)0.3(Sr2AlTaO6)0.7, SrTiO3, and DyScO3, which result in lattice mismatch strain ranging from −2.9% to +1.1%. We compare the effect of La concentration and strain on the structural and optical properties, and measure their effect on the electrical resistivity and mobility at room temperature. Room temperature resistivities ranging from ∼10−2 to 10−5 Ω cm are obtained depending on strain and La concentration. The room temperature mobility decreases with increasing strain regardless of the sign of the strain. The observed Drude peak and Burstein-Moss shift from spectroscopic ellipsometry clearly confirm that the La addition creates a high density of free carriers in SrTiO3. First principles calculations were performed to help understand the effect of La-doping on the density of states effective mass as well as the conductivity and DC relaxation time.

We show that the magnetic characteristics of Ta|CoFeB|MgO magnetic heterostructures are strongly influenced by doping the Ta underlayer with nitrogen. In particular, the saturation magnetization drops upon doping the Ta underlayer, suggesting that the doped underlayer acts as a boron diffusion barrier. In addition, the thickness of the magnetic dead layer decreases with increasing nitrogen doping. Surprisingly, the interface magnetic anisotropy increases to ∼1.8 erg/cm2 when an optimum amount of nitrogen is introduced into the Ta underlayer. These results show that nitrogen doped Ta serves as a good underlayer for spintronic applications including magnetic tunnel junctions and domain wall devices.

Thin film solar cells on flexible metal substrates require diffusion barriers in order to prevent the diffusion of detrimental species from the metallic flexible substrate into the photovoltaic device layers. This work demonstrates that an electrolessly deposited 300 nm nickel phosphorous film functions as a diffusion barrier to iron and chromium diffusion on a flexible stainless steel substrate. (C) 2013 The Electrochemical Society. [DOI: 10.1149/2.045303jes] All rights reserved.