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Area‐selective deposition (ASD) is a bottom‐up technique that provides numerous opportunities for nanoelectronic device fabrication. For example, advanced nano‐interconnect structures with barrierless metals like Ru in the contact holes can be created by Ru ASD with the bottom metals as growth surfaces and dielectrics as non‐growth surfaces. This work investigates Ru ASD by chemical vapor deposition (CVD) on industrially relevant substrates and nanopatterns and reveals how selectivity and growth rate are modulated by the CVD conditions and type of nanopattern. For low‐k dielectric/Cu substrate combinations, the selectivity reverses from metal‐on‐metal to metal‐on‐dielectric upon only changing the CVD co‐reagent from H2 to NH3. In contrast, NH3 is the preferred co‐reagent for SiO2‐TiN line patterns with critical dimension (CD) of 40 nm due to the more favorable adsorption and diffusion kinetics that cause growth rate and selectivity enhancement. Consistent with a diffusion‐mediated mechanism, the growth rate enhances even more for Ru CVD on nanoscale contact holes with CD of 10.5 nm, becoming 2.4 times higher as compared to unpatterned substrates. Thus, the ASD process changes drastically when pattern dimensions reach the nanoscale. The reported insights facilitate rational design of metal ASD processes for multiple applications in nanofabrication. [ABSTRACT FROM AUTHOR]

Area‐selective deposition (ASD) shows great promise for sub‐10 nm manufacturing in nanoelectronics, but significant challenges remain in scaling to ultrasmall dimensions and understanding feature‐dependent nonuniformity and selectivity loss. This work addresses these problems by simultaneously quantifying uniformity and selectivity for passivation/deposition/etch supercycles in 45 nm half‐pitch TiN/SiO2 line/space patterns. This work employs three selective processes that are uniquely suited for supercycle processing: dimethylamino‐trimethylsilane (DMA‐TMS) inhibition, TiO2 atomic layer deposition (ALD), and HBr/BCl3 plasma etch. The DMA‐TMS inhibition selectively passivates the SiO2 nongrowth surface without affecting deposition on the TiN and TiO2 growth surfaces. The plasma etch removes TiO2 defect particles at a faster rate than the conformal TiO2 film or SiO2 lines. Using three supercycles of this process, this work demonstrates 8 nm of TiO2 with 88% uniformity and ≈100% selectivity according to transmission electron microscopy (TEM), a 2×improvement in film thickness from previous reports in similar nanoscale patterns. Integrated consideration of uniformity and selectivity at specific feature scales will facilitate the effective design of selective deposition processes for nanoscale electronic devices. [ABSTRACT FROM AUTHOR]

Small-molecule inhibitors have recently been introduced for passivation during area-selective deposition (ASD). Small silanes like (N,N-dimethylamino)trimethylsilane (DMATMS) selectively react with −OH sites on SiO2 to form a less reactive –OSi(CH3)3 terminated surface. The –OSi(CH3)3 surface termination can inhibit many atomic layer deposition (ALD) processes, including TiCl4/H2O ALD. However, the mechanisms by which ALD is inhibited and by which selectivity is eventually lost are not well understood. This study uses in situ Fourier-transform infrared spectroscopy to probe the adsorption of DMATMS on SiO2 and the subsequent reactions when the passivated surface is exposed to TiCl4/H2O ALD. The chemisorption of DMATMS on isolated –OH groups on SiO2 is shown to inhibit the reaction with TiCl4. Further, we find that starting with an inherently inhibiting H-terminated Si surface, DMATMS can also react with residual –OH groups and reduce the extent of nucleation. Finally, using Rutherford backscattering spectrometry, the effectiveness of DMATMS passivation on SiO2 and H-terminated Si is quantified during extended ALD cycle numbers. The insight into the mechanisms of passivation by DMATMS and passivation loss can enable the rational design of highly selective ASD processes by carefully matching compatible surfaces, passivating agents, and ALD precursors. [ABSTRACT FROM AUTHOR]

Nanoelectronics holds significant promise for two-dimensional (2D) semiconducting transition metal dichalcogenide (TMD) applications. On a polycrystalline WS2 monolayer created by metal-organic chemical vapor deposition (MOCVD) at 950 °C, we studied the nucleation, growth, and development of Al2O3 atomic layer deposition (ALD) on a SiO2/Si substrate. In this investigation, we used various complementary characterization methods, such as Raman spectroscopy, elastic recoil detection, atomic force microscopy, and time-of-flight secondary ion mass spectrometry, to understand thoroughly the intrinsic reactivity of WS2. Strong peak intensity changes at the interfaces in the Raman line scans of the SiO2/Si patterns suggest extremely crystalline WS2. After multiple ALD cycles, triangular WS2 crystals were decorated to provide a two-dimensional growth mode with a great selectivity for grain boundaries and step edges. The results of this work can be used for further exploration of the TMD monolayer structure and properties, which is essential for tailoring 2D materials for a specific application in devices. [ABSTRACT FROM AUTHOR]

During TiO2 atomic layer deposition (ALD) using TiCl4 and H2O at ∼150 °C, nucleation proceeds rapidly on hydroxylated SiO2 but is inherently delayed on passivated surfaces such as H-terminated silicon (Si-H) and trimethylsilyl-passivated SiO2 (SiO2-TMS) formed using dimethylamino-trimethylsilane (DMA-TMS) as a small molecule inhibitor. In this work, we explore details of TiO2 nucleation on both Si-H and SiO2-TMS and show that the mechanisms leading to unwanted nuclei depend strongly on the passivation mechanism. Initial growth is observed as a function of ALD cycles using scanning electron microscopy to obtain average particle size, density, and overall surface coverage fraction. Also, average film thickness vs cycle is estimated using ellipsometry or Rutherford backscattering spectrometry. Data are compared to an analytical model that considers that either nucleation sites are present on the starting non-growth surface or sites are generated during the ALD process. On the Si-H surface, data and modeling indicate that nucleation occurs predominantly from a fixed number of nucleation sites present on the starting growth surface that start to immediately grow. However, on TMS-passivated SiO2, nucleation sites are predominantly generated during the growth process so that the density of nucleation sites increases as growth proceeds. Results indicate that nucleation sites are created when adsorbed ALD reactants become kinetically trapped on the SiO2-TMS surface. This demonstrates that mechanisms associated with unwanted nucleation during area-selective deposition (ASD) can depend on details of the surface passivation scheme, thereby providing insight to help to improve ASD strategies for advanced applications. [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.