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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]

Anisotropic growth of two-dimensional (2D) tungsten disulfide (WS2) crystals occurs during atomic layer deposition (ALD) from WS2 seeds at predetermined locations on large area dielectric substrates. The number of ALD reaction cycles determines the lateral dimensions of the WS2 crystals. This 2D synthesis approach is compatible with temperature sensitive structures due to the low deposition temperature and can be extended to other 2D materials and heterostructures thereof. The crystallinity of the seed and the selectivity of ALD precursors toward seeds and underlying starting surface affect the structural quality of the 2D crystals. [ABSTRACT FROM AUTHOR]

Area-selective atomic layer deposition (AS-ALD) is a coveted method for the fabrication of next-generation nano-electronic devices, as it can complement lithography and improve alignment through atomic scale control. Selective reactions of small molecule inhibitors (SMIs) can be used to deactivate growth on specific surface areas and as such enable AS-ALD. To investigate new applications of ASD, we need insight into the reactions of SMIs with a broad range of technology relevant materials. This paper investigates the reactions of aminosilane SMIs with a broad range of oxide surfaces and the impact on subsequent atomic layer deposition (ALD). We compare the reactions of two aminosilane SMIs, namely, dimethylamino-trimethylsilane (DMA-TMS) and hexamethyldisilazane (HMDS), with a hydroxylated SiO2 surface and the impact on subsequent ALD processes. The DMA-TMS reaction saturates faster than the HMDS reaction and forms a dense trimethylsilyl (TMS) layer with a higher TMS surface concentration. The higher TMS surface concentration yields better inhibition and higher selectivity during subsequent TiO2 ALD. We show that a wide range of surfaces, i.e., MgO, HfO2, ZrO2, Al2O3, TiO2 (TiN/TiOx), SiO2, SnO2, MoOx, and WO3 remain reactive after DMA-TMS exposure for conditions where SiO2 is passivated, indicating that DMA-TMS can enable AS-ALD on these surfaces with respect to SiO2. On these surfaces, DMA-TMS forms residual TMS and/or SiOxCyHz surface species that do not markedly inhibit ALD but may affect interface purity. Surfaces with lower, similar, and higher surface acidity than SiO2 all show less reactivity toward DMA-TMS, suggesting that surface acidity is not the only factor affecting the substrate-inhibitor interaction. Our study also compares a hybrid inorganic-organic SnOxCyHz and inorganic SnO2 material in view of their relevance as resist for extreme ultraviolet lithography. DMA-TMS can enable selective infiltration in SnOxCyHz, as opposed to selective deposition on SnO2, indicating tunable reactivity by bulk and surface composition. These insights into the reactivity of aminosilane SMIs may aid the design of new area-selective deposition processes, broaden the material space, and enable new applications. [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]

Area‐selective deposition (ASD) is a promising bottom‐up approach for fabricating nanoelectronic devices. However, a challenge is to prevent the undesired growth of nanoparticles in the nongrowth area. This work uses kinetic Monte Carlo (KMC) methods to investigate the defectivity in ruthenium ASD by (ethylbenzyl)(1‐ethyl‐1,4‐cyclohexadienyl)Ru/O2 (EBECHRu) atomic layer deposition (ALD) in line‐space nanopatterns with different dimensions. Ru ASD is governed by adsorption as well as diffusion. The defectivity depends on the pattern dimensions, as nanoparticles can diffuse and reach the interface with the growth area where they aggregate. For linewidths of 50 nm and smaller, all Ru adspecies are captured at the growth interface before growth by precursor adsorption is catalyzed. The synergetic effect of diffusion and size‐dependent reactivity reduces defectivity below 1010 Ru atoms cm−2 for at least 1000 ALD cycles. This is more than 1000 times lower than for patterns with a linewidth of 200 nm and larger, where the Ru content decreases significantly only near the interface with the growth surface. The predicted depletion zone is confirmed by experiments in nanoscale line‐space patterns. Overall, this mechanism results in smaller and fewer Ru nanoparticles for smaller patterns, facilitating the development of passivation‐deposition‐etch ASD processes for nanoelectronic device fabrication. [ABSTRACT FROM AUTHOR]

The structure, crystallinity and properties of as-deposited two-dimensional (2D) transition metal dichalcogenides are determined by nucleation mechanisms in the deposition process. 2D materials grown by atomic layer deposition (ALD) in the absence of a template are polycrystalline or amorphous. Little is known about their nucleation mechanisms. Therefore, the nucleation behavior of WS2 during plasma enhanced ALD from WF6, H2 plasma and H2S at 300 °C is investigated on amorphous ALD Al2O3 starting surface and on monocrystalline, bulk sapphire. Preferential interaction of the precursors with the Al2O3 starting surface promotes fast closure of the WS2 layer. The WS2 layers are fully continuous at WS2 content corresponding to only 1.2 WS2 monolayers. On amorphous Al2O3, (0002) textured and polycrystalline WS2 layers form with grain size of 5 to 20 nm due to high nucleation density (∼1014 nuclei/cm2). The WS2 growth mode changes from 2D (layer-by-layer) growth on the initial Al2O3 surface to three-dimensional (Volmer-Weber) growth after WS2 layer closure. Further growth proceeds from both WS2 basal planes in register with the underlying WS2 grain and from or over grain boundaries of the underlying WS2 layer with different in-plane orientation. In contrast, on monocrystalline sapphire, WS2 crystal grains can locally align along a preferred in-plane orientation. Epitaxial seeding occurs locally albeit a large portion of crystals remain randomly oriented, presumably due to the low deposition temperature. The WS2 sheet resistance is 168 MΩμm, suggesting that charge transport in the WS2 layers is limited by grain boundaries. [ABSTRACT FROM AUTHOR]

The atomic layer deposition (ALD) of Gd2O3 from tris(isopropyl-cyclopentadienyl) gadolinium (Gd(iPrCp)3) and O3 is studied as a function of the O2/N2 ratio used to generate O3. ALD using O3 with low N2 content leads to the formation of a hydroxyl-terminated surface after combustion reactions during O3 exposure followed by proton transfer and ligand release during the Gd(iPrCp)3 half cycle. This condition leads to the presence of parasitic chemical vapor deposition (CVD) due to the hygroscopicity of Gd2O3. By contrast, long O3 pulses with high N2 content lead to the dehydroxylation of the surface and to the suppression of both the proton transfer during the Gd(iPrCp)3 half cycle as well as the parasitic CVD reactions. [ABSTRACT FROM AUTHOR]

Epitaxial Si-O superlattices consist of alternating periods of crystalline Si layers and atomic layers of oxygen (O) with interesting electronic and optical properties. To understand the fundamentals of Si epitaxy on O atomic layers, we investigate the O surface species that can allow epitaxial Si chemical vapor deposition using silane. The surface reaction of ozone on H-terminated Si(100) is used for the O deposition. The oxygen content is controlled precisely at and near the atomic layer level and has a critical impact on the subsequent Si deposition. There exists only a small window of O-contents, i.e. 0.7–0.9 atomic layers, for which the epitaxial deposition of Si can be realized. At these low O-contents, the O atoms are incorporated in the Si-Si dimers or back bonds (-OSiH), with the surface Si atoms mainly in the 1+ oxidation state, as indicated by infrared spectroscopy. This surface enables epitaxial seeding of Si. For O-contents higher than one atomic layer, the additional O atoms are incorporated in the Si-Si back bonds as well as in the Si-H bonds, where hydroxyl groups (-Si-OH) are created. In this case, the Si deposition thereon becomes completely amorphous. [ABSTRACT FROM AUTHOR]

The evolution of the surface roughness during the atomic-layer deposition (ALD) of Al2O3, NiO, and HfO2 was studied by atomic-force microscopy and nonspecular x-ray reflectance. The results indicate that the crystallinity of the films played a crucial role in the roughness evolution during ALD. While the ALD of amorphous oxide films showed replication of the initial starting surface with no roughness build-up, the ALD of polycrystalline oxide films led to a strong anomalous dependence of the roughness on the film thickness. This behavior is explained within a model taking into account spatial variations of the adsorption site density. [ABSTRACT FROM AUTHOR]

Single-wall carbon nanotubes (SWCNTs) have great potential to become the channel material for future high-speed transistor technology. However, to realize a carbon nanotube field effect transistor (CNTFET) with excellent gate control, the high-k dielectrics between the CNT and the metal gate must have superb electrical properties and extremely high uniformity. Thus it is essential to understand the interactions between high-k materials and the SWCNTs to effectively control the transistor characteristics. In this study, we investigate the effects of atomic layer deposited (ALD) high-k dielectrics (Al2O3 and HfO2) on SWCNTs using Raman spectroscopy. We subjected the SWCNTs to various ALD cycles and studied the nucleation and growth of ALD dielectrics at defect sites using scanning electron microscopy and transmission electron microscopy images. We analyzed these samples using Raman spectroscopy and x-ray photoelectron spectroscopy. The Raman peak shifts of the G-peak and the 2D (G0) peaks suggest doping and stress induced effects on the CNTs by the surrounding high-k oxide environment. Trends in the G-peak FWHM and G/D-peak ratios were identified and compared between Al2O3 and HfO2. We confirmed the ALD-deposited HfO2 is polycrystalline using x-ray diffraction and analyzed dielectric-CNT bonding states using XPS measurements. This study provides insights on the effects of ALD high-k materials on SWCNTs for future high-speed transistor applications. [ABSTRACT FROM AUTHOR]

RuCp (ruthenocene) and RuCpPy (cyclopentadienyl pyrrolyl ruthenium) complexes are used in ruthenium (Ru) atomic layer deposition (ALD) but exhibit a markedly different reactivity with respect to the substrate and co-reactant. In search of an explanation, we report here the results of a comparative study of the heterolytic and homolytic dissociation enthalpy of these two ruthenium complexes, making use of either density functional theory (DFT) or multiconfigurational perturbation theory (CASPT2). While both methods predict distinctly different absolute dissociation enthalpies, they agree on the relative values between both molecules. A reduced heterolytic dissociation enthalpy is obtained for RuCpPy compared to RuCp, although the difference obtained from CASPT2 (19.9 kcal/mol) is slightly larger than the one obtained with any of the DFT functionals (around 17 kcal/mol). Both methods also agree on the more pronounced stability of the Cp ligand in RuCpPy than in RuCp (by around 9 kcal/mol with DFT and by 6 kcal/mol with CASPT2). [ABSTRACT FROM AUTHOR]

Due to its high intrinsic mobility, germanium (Ge) is a promising candidate as a channel material (offering a mobility gain of approximately ×2 for electrons and ×4 for holes when compared to conventional Si channels). However, many issues still need to be addressed before Ge can be implemented in high-performance field-effect-transistor (FET) devices. One of the key issues is to provide a high-quality interfacial layer, which does not lead to substantial drive current degradation in both low equivalent oxide thickness and short channel regime. In recent years, a wide range of materials and processes have been investigated to obtain proper interfacial properties, including different methods for Ge surface passivation, various high-k dielectrics and metal gate materials and deposition methods, and different post-deposition annealing treatments. It is observed that each process step can significantly affect the overall metal-oxide-semiconductor (MOS)-FET device performance. In this review, we describe and compare combinations of the most commonly used Ge surface passivation methods (e.g. epi-Si passivation, surface oxidation and/or nitridation, and S-passivation) with various high-k dielectrics. In particular, plasma-based processes for surface passivation in combination with plasma-enhanced atomic layer deposition for high-k depositions are shown to result in high-quality MOS structures. To further improve properties, the gate stack can be annealed after deposition. The effects of annealing temperature and ambient on the electrical properties of the MOS structure are also discussed. [ABSTRACT FROM AUTHOR]

In this work, we have studied the TMA/H2O (TMA = Al(CH3)3) atomic layer deposition (ALD) of Al2O3 on hydroxyl (OH) and thiol (SH) terminated semiconductor substrates. Total reflection x-ray fluorescence reveals a complex growth-per-cycle evolution during the early ALD reaction cycles. OH and SH terminated surfaces demonstrate growth inhibition from the second reaction cycle on. Theoretical calculations, based on density functional theory, are performed on cluster models to investigate the first TMA/H2O reaction cycle. Based on the theoretical results, we discuss possible mechanisms for the growth inhibition from the second reaction cycle on. In addition, our calculations show that AlCH3 groups are hydrolyzed by a H2O molecule adsorbed on a neighboring Al atom, independent of the type of backbonds (Si-O, Ge-O, or Ge-S) of AlCH3. The coordination of Al remains four-fold after the first TMA/H2O reaction cycle. [ABSTRACT FROM AUTHOR]

Area‐selective deposition (ASD) receives increasing attention as a bottom‐up approach for nanoelectronic device fabrication. Uptake of ASD is however limited by defects, which manifest as undesired particle growth on the nongrowth surface. A defect mitigation solution is demonstrated for Ru ASD on TiN/SiO2 nanopatterns by making use of the size‐dependent Ru nanoparticle reactivity. During the initial stages of 1‐(ethylbenzyl)‐1,4‐(ethylcyclohexadienyl)ruthenium and oxygen (EBECHRu/O2) atomic layer deposition (ALD) on dielectrics, Ru particles are too small to catalytically dissociate oxygen, and their growth is suppressed. This phenomenon creates an ASD process window in which particles can be completely etched while retaining the integrity of the ASD pattern on a TiN growth surface. Decreasing the ALD temperature strongly suppresses defect growth, which can be used to expand the process window for ASD. The ASD process window is confirmed by self‐focusing secondary ion mass spectrometry (SF‐SIMS) with its low limit of detection while analyzing 104 structures simultaneously. No defects are detected for Ru ASD on 36 nm TiN/SiO2 patterns by SF‐SIMS. The Ru ASD process is applied for bottom‐up block patterning and functional hardmask patterns are obtained on 300 mm wafers. The approach followed in this work can produce defect‐free ASD processes for a wide variety of applications. [ABSTRACT FROM AUTHOR]

Understanding the growth mechanisms during the early stages of atomic layer deposition (ALD) is of interest for several applications including thin film deposition, catalysis, and area‐selective deposition. The surface dependence and growth mechanism of (ethylbenzyl)(1‐ethyl‐1,4‐cyclohexadienyl)ruthenium and O2 ALD at 325 °C on HfO2, Al2O3, OH, and SiOSi terminated SiO2, and organosilicate glass (OSG) are investigated. The experimental results show that precursor adsorption is strongly affected by the surface termination of the dielectric, and proceeds most rapidly on OH terminated dielectrics, followed by SiOSi and finally SiCH3 terminated dielectrics. The initial stages of growth are characterized by the formation and growth of Ru nanoparticles, which is mediated by the diffusion of Ru species. Mean‐field and kinetic Monte Carlo modeling show that ALD on OSG is best described when accounting for (1) cyclic generation of new nanoparticles at the surface, (2) surface diffusion of both atomic species and nanoparticles, and (3) size‐dependent nanoparticle reactivity. In particular, the models indicate that precursor adsorption initially occurs only on the dielectric substrate, and occurs on the Ru nanoparticles only when these reach a critical size of about 0.85 nm. This phenomenon is attributed to the catalytic decomposition of oxygen requiring a minimum Ru nanoparticle size. Atomic layer deposition of ruthenium on dielectrics is governed by cyclic nanoparticle generation, surface diffusion, and aggregation of nanoparticles. The nanoparticle reactivity is strongly size‐dependent. This insight in the growth mechanism can help tune the morphology of the deposited material for several applications including thin film deposition, catalytic nanoparticles, and area‐selective deposition. [ABSTRACT FROM AUTHOR]

The reaction chemistry during theatomic layer deposition (ALD)of Sc2O3and Gd2O3fromSc(MeCp)3, Gd(iPrCp)3, and H2O was investigated by in situtime-resolvedquadrupole mass spectrometry. Despite the similarity of the ligandsof the Sc and Gd precursors, the growth characteristics and liganddissociation patterns of the Sc2O3and Gd2O3ALD processes showed considerably differentbehavior. For both processes, the precursors reacted with the hydroxylatedsurface by proton transfer and release of the protonated ligand. Theremaining ligands were then removed by hydrolysis during the H2O pulse. However, for the Sc(MeCp)3/H2O process, ∼56% of MeCpH was released during the Sc(MeCp)3exposure, whereas in the case of the Gd(iPrCp)3/H2O process, as much as 90% of iPrCpHwas released during the Gd(iPrCp)3pulse. Theobservation that almost all iPrCp ligands were removedduring the initial Gd(iPrCp)3absorption stepcan be ascribed to CVD-like reactions between the Gd(iPrCp)3precursor and excess hydroxide or physisorbed H2O on the hygroscopic Gd2O3surface. The influenceof the growth temperature on the ligand exchange behavior and theresulting film properties (thickness uniformity, impurity concentration)was studied in the temperature range between 200 and 350 °C.In addition, the transient growth behavior of Gd2O3on Sc2O3and vice versa was studied,indicating that the hygroscopic nature of Gd2O3also strongly influences the deposition of GdxSc1–xO3ternaryoxides. [ABSTRACT FROM AUTHOR]

The demand for transistors and memory devices with smaller feature sizes and increasingly complex architectures furthers the need for advanced thin film patterning techniques. A prepatterned, sacrificial layer can be used as a template for bottom-up fill of new materials which would otherwise be difficult to pattern using traditional top-down lithographic methods. This work investigates initial growth of TiN, TiO2, and HfO2 thin films during thermal atomic layer deposition (ALD) onto a high density, amorphous carbon (aC) sacrificial layer. ALD of TiN by TiCl4/NH3 at 390 °C, TiO2 by Ti(OCH3)4/H2O at 250 °C, and HfO2 by HfCl4/H2O at 300 °C on as-deposited aC films resulted in uninhibited, continuous thin film growth. We find that carbon surface reduction and passivation using a H2 plasma resulted in delayed film coalescence for TiN, TiO2, and HfO2 on the aC. After 200 TiN cycles on H2 plasma-treated aC, Rutherford backscattering spectrometry shows Ti levels below the detection limit (8 × 1013 at/cm2), whereas SiO2 or Si3N4 substrates show TiN growth of ~6 nm, corresponding to a selectivity of ~200:1. Exposing plasma-treated aC to H2O induces nucleation for TiN ALD, consistent with favorable nucleation on hydroxyl sites. Therefore, the H2O co-reagent in TiO2 and HfO2 ALD contributes to loss of selectivity compared to TiN ALD using NH3. We confirm scaling of selectivity to sub-50 nm patterns using 45 nm aC/Si3N4 line/space patterns, where 3.5 nm TiO2 and 5.8 nm TiN films are deposited on Si3N4 with minimal particle formation on aC, with selectivity loss primarily on feature corners and edges. We conclude that improved scaling of selectivity to nanometer scale patterns can be achieved by optimizing surface loading and extent of plasma exposure, and by further understanding shape effects in nanoscale surface plasma modification. [ABSTRACT FROM AUTHOR]

Several applications of two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) in nanoelectronic devices require the deposition of ultrathin pinhole free high-κ dielectric films on 2D TMDs. However, deposition of nm-thin high-κ dielectric films on 2D TMDs remains challenging due to the inert TMD surface. Here, we demonstrate that the surface of a synthetic polycrystalline 2D MoS2 film is functionalized with SiO2 to enable the atomic layer deposition (ALD) of thin and continuous Al2O3 and HfO2 layers. The origins of nucleation, the growth mode, and layer coalescence process have been investigated by complementary physical characterization techniques, which can determine the chemical bonds, absolute amount, and surface coverage of the deposited material. SiO2 is prepared by oxidizing physical vapor deposited Si in air. The surface hydrophilicity of MoS2 significantly increases after SiO2functionalization owing to the presence of surface hydroxyl groups. SiO2 layers with a Si content of only 1.5 x 1015 atoms/cm² enable the deposition of continuous 2 nm thin Al2O3 and HfO2 layers on MoS2 at 300 °C. This fast layer closure can be achieved despite the sub-nm thickness and discontinuity of the SiO2 nucleation layer. On the basis of the experimental results, we propose a nucleation mechanism that explains this fast layer closure. Nucleation of Al2O3 and HfO2 occurs on the SiO2 islands, and fast layer closure is achieved by the lateral growth starting from the many nm-spaced SiO2 islands. Finally, the dielectric properties of Al2O3 on the functionalized MoS2 are confirmed in a top-gated capacitor that shows a leakage current of 3.8 x 10-6 A/cm² at a 3.4 nm equivalent oxide thickness. To conclude, fast nucleation and layer closure in ALD can be achieved even for a sub-nm thin, discontinuous nucleation layer. We propose that this insight can also be applied to other ALD processes, materials, or applications where thin and fully continuous layers are required. [ABSTRACT FROM AUTHOR]

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]

The surface chemistryand the interface formation during the initialstages of the atomic layer deposition (ALD) of Al2O3from trimethylaluminum (TMA) and H2O on InP(100)were studied by synchrotron radiation photoemission spectroscopy andscanning tunneling microscopy. The effect of the ex situ surface cleaningby either H2SO4or (NH4)2S was examined. It is shown that the native oxide on the InP surfaceconsisted mainly of indium hydrogen phosphates with a P enrichmentat the interface with InP. After a (NH4)2S treatment,S was present on the surface as a sulfide in both surface and subsurfacesites. Exposure to TMA led to the formation of a thin AlPO4layer, irrespective of the surface cleaning. The surface Fermi levelof p-type InP was found to be pinned close to midgap after H2SO4cleaning and moved only slightly further toward theconduction band edge upon TMA exposure, indicating that the AlPO4/InP interface was rather defective. (NH4)2S passivation led to a Fermi level position of p-type InPclose to the conduction band edge. Hence, the InP surface was weaklyinverted, which can be attributed to surface doping by S donors. TMAexposure was found to remove surface S, which was accompanied by ashift of the Fermi level to midgap, consistent with the removal of(part of) the S donors in combination with a defective AlPO4/InP interface. Further TMA/H2O ALD did not lead to anydetectable changes of the AlPO4/InP interface and suggestedsimple overgrowth with Al2O3. [ABSTRACT FROM AUTHOR]