Structural characterization of a Cu/MgO(001) interface using CS-corrected HRTEM

Cazottes, Sophie; Zhang, Zaoli; Daniel, Rostislav; Chawla, J. S.; Gall, Daniel; Dehm, Gerhard

doi:10.1016/j.tsf.2010.09.017

Cited by 27 publications

(18 citation statements)

References 26 publications

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“…In comparison, the lattice mismatch between TiN and fcc Cu amounts to -17% [57,58], thus slightly exceeding the 15% rule. Still, epitaxial growth of Cu on TiN is not an unreasonable assumption, as it has been reported previously for Cu films deposited on MgO, where the lattice mismatch is comparable [59,60]. Pole figure measurements and TEM investigations discussed in the appended Paper I confirm that the TiN/Cu bilayers exhibit a cube-on-cube epitaxial relationship with the substrate, i.e.…”

Section: Epitaxial Growth Of Single-crystalline Filmssupporting

confidence: 68%

High-resolution characterization of TiN diffusion barrier layers

Mühlbacher¹

2015

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Titanium nitride (TiN) films are widely applied as diffusion barrier layers in microelectronic devices. The continued miniaturization of such devices not only poses new challenges to material systems design, but also puts high demands on characterization techniques. To gain understanding of diffusion processes that can eventually lead to failure of the barrier layer and thus of the whole device, it is essential to develop routines to chemically and structurally investigate these layers down to the atomic scale. In the present study, model TiN diffusion barriers with a Cu overlayer acting as the diffusion source were grown by reactive magnetron sputtering on MgO(001) and thermally oxidized Si(001) substrates. Cross-sectional transmission electron microscopy (XTEM) of the pristine samples revealed epitaxial, single-crystalline growth of TiN on MgO(001), while the polycrystalline TiN grown on Si(001) exhibited a [001]-oriented columnar microstructure. Various annealing treatments were carried out to induce diffusion of Cu into the TiN layer. Subsequently, XTEM images were recorded with a high-angle annular dark field detector, which provides strong elemental contrast, to illuminate the correlation between the structure and the barrier efficiency of the single- and polycrystalline TiN layers. Particular regions of interest were investigated more closely by energy dispersive X-ray (EDX) mapping. These investigations are completed by atom probe tomography (APT) studies, which provide a three-dimensional insight into the elemental distribution at the near-interface region with atomic chemical resolution and high sensitivity. In case of the single-crystalline barrier, a uniform Cu-enriched diffusion layer of 12 nm could be detected at the interface after an annealing treatment at 1000 °C for 12 h. This excellent barrier performance can be attributed to the lack of fast diffusion paths such as grain boundaries. Moreover, density-functional theory calculations predict a stoichiometry-dependent atomic diffusion mechanism of Cu in bulk TiN, with Cu diffusing on the N-sublattice for the experimental N/Ti ratio. In comparison, the polycrystalline TiN layers exhibited grain boundaries reaching from the Cu-TiN interface to the substrate, thus providing direct diffusion paths for Cu. However, the microstructure of these columnar layers was still dense without open porosity or voids, so that the onset of grain boundary diffusion could only be found after annealing at 900 °C for 1 h. The present study shows how to combine two high resolution state-of-the-art methods, TEM and APT, to characterize model TiN diffusion barriers. It is shown how to correlate the microstructure with the performance of the barrier layer by two-dimensional EDX mapping and three-dimensional APT. Highly effective Cu-diffusion barrier function is thus demonstrated for single-crystal TiN(001) (up to 1000 °C) and dense polycrystalline TiN (900 °C)

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Section: Epitaxial Growth Of Single-crystalline Filmssupporting

confidence: 68%

High-resolution characterization of TiN diffusion barrier layers

Mühlbacher¹

2015

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“…28). The Cu 002 peak full-widthat-half-maximum (FWHM) increases from 0.46 for Cu/TiN with T s ¼ 25 C, to 0.71 for Cu/MgO with T s ¼ 80 C, to 0.81 for Cu/MgO with T s ¼ 25 C. This corresponds to a decreasing x-ray coherence length of 19, 13, and 11 nm, respectively, which is below the layer thickness of 40 nm and indicates increasing residual strain variations and/or crystalline defects within the Cu layer, 16 which are also responsible for the decreasing peak intensity in Fig. 1(a).…”

Section: Methodsmentioning

confidence: 95%

“…The wider rocking curve for Cu/MgO indicates a lower crystalline quality, however, this may also be due to the tilt of the Cu grains to relieve misfit strain, as previously reported for Cu(001)/MgO(001). 15,16 XRD pole figure measurements for all samples, using constant 2h values corresponding to Cu 002 and Cu 111 reflections at 50.42 and 43.32 , respectively, show only a single peak for Cu 002 at the origin (not shown) and fourfold symmetric peaks at a tilt, w ¼ 54.7 , and at polar angles, / ¼ 45, 135, 225, and 315 for Cu 111, as presented in the representative Fig. 1(c) 15 Figure 1(d) shows / scans about the peak at / ¼ 45 for the Cu 111 reflection for the same layers as in Figs.…”

Section: Methodsmentioning

confidence: 99%

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Epitaxial TiN(001) wetting layer for growth of thin single-crystal Cu(001)

Chawla

Zhang

Gall

2011

Journal of Applied Physics

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Articles you may be interested inEpitaxial Ag(001) grown on MgO(001) and TiN(001): Twinning, surface morphology, and electron surface scattering J. Appl. Phys. 111, 043708 (2012); 10.1063/1.3684976Reactive magnetron cosputtering of hard and conductive ternary nitride thin films: Ti-Zr-N and Ti-Ta-N Single-crystal Cu(001) layers, 4-1400 nm thick, were deposited on MgO(001) with and without a 2.5-nm-thick TiN(001) buffer layer. X-ray diffraction and reflection indicate that the TiN(001) surface suppresses Cu-dewetting, yielding a 4 Â lower defect density and a 9 Â smaller surface roughness than if grown on MgO(001) at 25 C. In situ and low temperature electron transport measurements indicate that ultra-thin (4 nm) Cu(001) remains continuous and exhibits partial specular scattering at the Cu-vacuum boundary with a Fuchs-Sondheimer specularity parameter p ¼ 0.6 6 0.2, suggesting that the use of epitaxial wetting layers is a promising approach to create low-resistivity single-crystal Cu nanoelectronic interconnects.

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“…In particular, the optimal design and fabrication of metal-oxide composites through in situ internal oxidation require a fundamental (rather than phenomenological) understanding of the thermodynamics and kinetics of in situ formed metal-oxide interfaces, and how they interplay with processing parameters during oxidation fabrication. Over the last two decades, remarkable efforts have been spent in employing experimental high-resolution electron microscopy for characterizing the metal-oxide interface details, from interfacial orientation and structure, to lattice mismatch and even misfit dislocations (if any) [1][2][3][4]. However, these characterization techniques might be sufficient for structural and element identification, but cannot provide much useful insight into the chemical interactions across the interfaces, such as interface stoichiometry, interface bonds, and the associated free energetics, that are equally-if not more-critical for an appropriate assessment of interface stability and the overall mechanical properties of the composites.…”

Section: Introductionmentioning

confidence: 99%

Interface-level thermodynamic stability diagram for in situ internal oxidation of Ag(SnO2)p composites

Jiang

et al. 2014

J Mater Sci

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We present a combined experimental and theoretical study on interfacial structure and thermodynamics in internally oxidized Ag(SnO 2 ) p composites. The orientation relation between in situ formed SnO 2 particles and the silver matrix was characterized using high-resolution transmission electron microscopy techniques. First-principles energetic calculations were then performed to predict the equilibrium interface structures and corresponding adhesion properties as functions of temperature and oxygen partial pressure. All results were combined to construct the interface-level thermodynamic stability diagram, for guiding the optimal design of internal oxidation parameters.

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Structural characterization of a Cu/MgO(001) interface using CS-corrected HRTEM

Cited by 27 publications

References 26 publications

High-resolution characterization of TiN diffusion barrier layers

High-resolution characterization of TiN diffusion barrier layers

Epitaxial TiN(001) wetting layer for growth of thin single-crystal Cu(001)

Interface-level thermodynamic stability diagram for in situ internal oxidation of Ag(SnO2)p composites

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