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The process characteristics, the surface chemistry, and the resulting film properties of Ru deposited by atomic layer deposition from (ethylbenzyl)(1-ethyl-1,4-cyclohexadienyl)Ru(0) (EBECHRu) and O2 are discussed. The surface chemistry was characterized by both combustion reactions as well as EBECHRu surface reactions by ligand release. The process behavior on TiN starting surfaces at 325 °C was strongly influenced by Ti(O,N)x segregation on the growing Ru surface with consequences for both the growth per cycle as well as the film properties. For optimized process conditions, the films showed high purity with low C and O concentrations of the order of 1020 at./cm3. Higher deposition temperature led to strong (001) fiber texture of the films on SiO2 starting surfaces. Annealing in forming gas improved the crystallinity and led to resistivity values as low as 11 μΩcm for Ru films with a thickness of 10 nm. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) transition metal dichalcogenides are potential low dissipative semiconductor materials for nanoelectronic devices. Such applications require the deposition of these materials in their crystalline form and with controlled number of monolayers on large area substrates, preferably using deposition temperatures compatible with temperature sensitive structures. This paper presents a low temperature plasma-enhanced atomic layer deposition (PEALD) process for 2D WS2 based on a ternary reaction cycle consisting of consecutive WF6, H2 plasma, and H2S reactions. Strongly textured, nanocrystalline WS2 is grown at 300 °C. The composition and crystallinity of these layers depends on the PEALD process conditions, as understood by a model for the redox chemistry of this process. The H2 plasma is essential for the deposition of WS2 as it enables the reduction of -W6+Fx surface species. Nevertheless, the impact of subsurface reduction reactions needs to be minimized to obtain WS2 with well-controlled composition (S/W ratio of 2). [ABSTRACT FROM AUTHOR]

Recently, a step-flow growth mode has been proposed to break the inherent molybdenum disulfide (MoS 2 ) crystal domain bimodality and yield a single-crystalline MoS 2 monolayer on commonly employed sapphire substrates. This work reveals an alternative growth mechanism during the metal-organic chemical vapor deposition (MOCVD) of a single-crystalline MoS 2 monolayer through anisotropic 2D crystal growth. During early growth stages, the epitaxial symmetry and commensurability of sapphire terraces rather than the sapphire step inclination ultimately govern the MoS 2 crystal orientation. Strikingly, as the MoS 2 crystals continue to grow laterally, the sapphire steps transform the MoS 2 crystal geometry into diamond-shaped domains presumably by anisotropic diffusion of ad-species and facet development. Even though these MoS 2 domains nucleate on sapphire with predominantly bimodal 0 and 60° azimuthal rotation, the individual domains reach lateral dimensions of up to 200 nm before merging seamlessly into a single-crystalline MoS 2 monolayer upon coalescence. Plan-view transmission electron microscopy reveals the single-crystalline nature across 50 μm by 50 μm inspection areas. As a result, the median carrier mobility of MoS 2 monolayers peaks at 25 cm 2 V -1 s -1 with the highest value reaching 28 cm 2 V -1 s -1 . This work details synthesis-structure correlations and the possibilities to tune the structure and material properties through substrate topography toward various applications in nanoelectronics, catalysis, and nanotechnology. Moreover, shape modulation through anisotropic growth phenomena on stepped surfaces can provide opportunities for nanopatterning for a wide range of materials.

In view of its epitaxial seeding capability, c -plane single crystalline sapphire represents one of the most enticing, industry-compatible templates to realize manufacturable deposition of single crystalline two-dimensional transition metal dichalcogenides (MX 2 ) for functional, ultrascaled, nanoelectronic devices beyond silicon. Despite sapphire being atomically flat, the surface topography, structure, and chemical termination vary between sapphire terraces during the fabrication process. To date, it remains poorly understood how these sapphire surface anomalies affect the local epitaxial registry and the intrinsic electrical properties of the deposited MX 2 monolayer. Therefore, molybdenum disulfide (MoS 2 ) is deposited by metal-organic chemical vapor deposition (MOCVD) in an industry-standard epitaxial reactor on two types of c -plane sapphire with distinctly different terrace and step dimensions. Complementary scanning probe microscopy techniques reveal an inhomogeneous conductivity profile in the first epitaxial MoS 2 monolayer on both sapphire templates. MoS 2 regions with poor conductivity correspond to sapphire terraces with uncontrolled topography and surface structure. By intentionally applying a substantial off-axis cut angle (1° in this work), the sapphire terrace width and step height-and thus also surface structure-become more uniform across the substrate and MoS 2 conducts the current more homogeneously. Moreover, these effects propagate into the extrinsic MoS 2 device performance: the field-effect transistor variability reduces both within and across wafers at higher median electron mobility. Carefully controlling the sapphire surface topography and structure proves an essential prerequisite to systematically study and control the MX 2 growth behavior and capture the influence on its structural and electrical properties.

Atomic layer deposition of ruthenium is studied as a barrierless metallization solution for future sub-10 nm interconnect technology nodes. We demonstrate the void-free filling in sub-10 nm wide single damascene lines using an ALD process in combination with 2.5 Å of ALD TiN interface and postdeposition annealing. At such small dimensions, the ruthenium effective resistance depends less on the scaling than that of Cu/barrier systems. Ruthenium effective resistance potentially crosses the Cu curve at 14 and 10 nm according to the semiempirical interconnect resistance model for advanced technology nodes. These extremely scaled ruthenium lines show excellent electromigration behavior. Time-dependent dielectric breakdown measurements reveal negligible ruthenium ion drift into low-κ dielectrics up to 200 °C, demonstrating that ruthenium can be used as a barrierless metallization in interconnects. These results indicate that ruthenium is highly promising as a replacement to Cu as the metallization solution for future technology nodes.