Tetrachloride Precursors Research Articles

Surface Passivation of Polymer Based Redistribution Layers for Area Selective Deposition of an Oxygen Barrier

Heterogeneous 3D integration is being hailed as the driver for new technologies due to its stacked device architecture. This increases functionality as the number and length of interconnecting wires decreases, in turn decreasing power consumption. In these advanced packaging technologies, the metal redistribution layers (RDLs) and the insulating polymer surrounding them are crucial components on which stringent reliability requirements are placed. The metal RDL’s are necessary to reroute signals from device level to packaging level. The polymer insulator, used as an alternative to traditional dielectric materials, must (i) be photosensitive to be compatible with lithography processing steps, (ii) possess high mechanical strength, (iii) exhibit good electrical performance, (iv) have a high thermal stability and glass transition temperature, and crucially (v) it must not be hygroscopic. Low or no moisture uptake of the polymer is essential as any moisture can cause mechanical and electrical reliability issues. Absorbed moisture can cause oxidation of Cu lines leading to the well-known problem of Cu diffusion resulting in voids, contact issues, delamination, electromigration and higher leakage currents.Area selective deposition (ASD) could greatly benefit these RDL’s by preferentially depositing an oxygen barrier to stop the oxidation of the Cu lines. The proprietary polymer used in this work is part of the WPR series by JSR Corporation and is a thermosetting phenol-based polymer which displays a high mechanical stability as it contains rubber nanoparticles, 70 nm in diameter. These are added to the polymer to increase the toughness and to prevent cracks and fractures forming and propagating through the film. However, achieving ASD with this polymer is difficult as the polymer is designed to have good adhesion properties so it will easily adhere to the Cu in the metal lines, and there are two materials of interest to passivate, the polymer itself and the rubber nanoparticles.In this work the surface is passivated by utilizing a polymerizing octafluorocyclobutane (C4F8) plasma which creates a Teflon-like film on the surface. The surface morphology and hydrophobicity are investigated to assess the best plasma exposure time, which was found to be 30 s. Surface chemistry from XPS analysis reveals surface modification through the deposition of fluorine rich groups from the 30 s C4F8 plasma exposure, Figure 1(a). Water contact angle measurements reveal an initial hydrophobic surface (~94°) but this hydrophobicity decreases over the course of several seconds. Following the 30 s C4F8 plasma exposure, the hydrophobicity increases significantly to above 110° and remains stable as shown in Figure 1(b). Surface morphology studies carried out by AFM demonstrates no increase in surface roughness following plasma exposure, Figure 1(c) and (d). ALD tests show the process to be selective to the tetrachloride family of ALD precursors. No selectivity was observed with tetrakis (dimethylamino) or isopropoxide based precursors. This process has the capability to block approximately 2 nm of TiO2 and HfO2 from these tetrachloride precursors. Studies of the same process on Cu substrates show that the metal surface is only temporarily modified, and ALD growth can still take place. Reliability stress and corrosion tests were performed to assess if the selectively deposited barriers could prevent Cu oxidation.Figure 1(a) C 1s XPS spectra showing difference before and after plasma treatment, (b) WCA value increases following plasma treatment, and AFM images in (c) and (d) show no change in the surface following plasma exposure. Figure 1

Isolation of a Dodecanuclear Polyoxo Cluster {Nb12O21} Showing a Rare Case of Five‐fold Coordinated Niobium(V) Centers with a Square Pyramidal Geometry

AbstractThe reactivity of the complexing anthracene‐9‐carboxylate ligand has been investigated with a niobium(IV) tetrachloride precursor (NbCl4 ⋅ 2THF) in isopropanol solvent. This resulted in the crystallization of a molecular assembly containing two distinct {Nb12O21} cores surrounded by multiple isopropanolate and anthracenoate ligands. The compound is formulated [Nb12((μ3‐O)3(μ‐O)18(C15H9O2)8(OiPr)10] ⋅ [Nb12(μ3‐O)2(μ‐O)19(C15H9O2)8(OiPr)10] illustrating the two different dodecameric oxo‐clusters, for which the niobium(IV) precursor was oxidized in the niobium(V) state during the reactional process. The two distinct {Nb12O21} units mainly differs by the environment of the niobium centers, which exhibits unexpected five‐fold coordination (square pyramid) for some of them, together with the classical six‐fold coordination (octahedron) as usually found for niobium(V). In the crystallization process, the. IR spectroscopy was used to analyze the esterification reaction occurring between the anthracene acid an isopropanolate ligands responsible of the production of water used in the oxo‐condensation of the niobium centers. 93Nb Solid state NMR was tentatively used to assess the occurrence of the different niobium environments.

Crystalline Molecular Assemblies of Complexes Showing Eightfold Coordinated Niobium(IV) Dodecahedral Geometry in the Pyridine-Dicarboxylic Acid System.

The reactivity of 2,3-pyridine-dicarboxylic (known as quinolinic or H2qui) acid and 2,5-pyridine-dicarboxylic (known as isocinchomeronic or H2icc) acid has been investigated as a complexing agent toward the niobium(IV) tetrachloride precursor (NbCl4·2THF) in different organic solvent mixtures. It resulted in the isolation of four crystalline assemblies of mononuclear coordination complexes 1-4 [Nb(HL)4·solvent], where HL is the monoprotonated quinolinate (Hqui) ligand (complexes 1-3) or the monoprotonated isocinchomeronate ligand (complex 4). For each complex, the discrete niobium(IV) center is eightfold coordinated to four oxygen atoms from the deprotonated carboxylate arm and four nitrogen atoms from the pyridine part of the dicarboxyl ligand with a dodecahedral environment [NbO4N4]. The remaining carboxyl arm (either in 3 or in 5 position) remained under its protonated form, leading to neutral [Nb(HL)4] moieties for compounds 1, 2, and 4, or the anionic [Nb(qui)(Hqui)3]- moiety for compound 3. The complexes are observed in various molecular arrangements, involving intercalated solvent molecules such as acetonitrile in compound 1 ([Nb(Hqui)4·0.8(CH3CN)], obtained at room temperature), a mixture of acetonitrile and pyridine in compound 2 ([Nb(Hqui)4·0.7CH3CN·2PYR], obtained via the solvothermal reaction at 80 °C), a mixture of pyridine and triethylamine, in addition with water and chloride species, in compound 3 ([Nb(qui)(Hqui)3·Cl·HPYR·HTEA·1.5H2O], obtained via solvothermal reaction at 80 °C), and N,N-dimethylformamide in compound 4 ([Nb(Hicc)4·6DMF], obtained at room temperature). The d1 configuration expected for the niobium(IV) centers has been analyzed by magnetic measurements, as well as by EPR and XPS. An anti-ferromagnetism transition has been observed at very low temperatures for complexes 1 (3.6 K) and 4 (3.3 K), for which the shortest Nb···Nb interatomic lengths occur.

Reactor scale simulations of ALD and ALE: Ideal and non-ideal self-limited processes in a cylindrical and a 300 mm wafer cross-flow reactor

We have developed a simulation tool to model self-limited processes such as atomic layer deposition (ALD) and atomic layer etching inside reactors of arbitrary geometry as well the output of in situ quartz crystal microbalance and mass spectrometry. We have applied this model to two standard types of cross-flow reactors: a cylindrical tube reactor and a model 300 mm wafer reactor, and explored both ideal and nonideal self-limited kinetics. The model results are in agreement with experimental results and analytic expressions obtained using a simple plug-flow model for the cylindrical tube reactor. We also extended the simulations to consider two nonideal self-limited processes: soft-saturating processes characterized by a slow reaction pathway and processes where surface by-products can compete with the precursor for the same pool of adsorption sites. Our results show that it is possible to have a self-limited process with saturated yet inhomogeneous growth profiles due to the competition of reactor by-products. This is in agreement with experimental observations for titanium dioxide ALD from titanium tetraisopropoxide and titanium tetrachloride precursors.

TiO2 nanorods with CdS quantum dots for optical applications

We combine CdS semiconductor quantum dots and single-crystalline rutile TiO2 nanorod arrays to produce a practical quantum dot sensitized solar cell. A facile wet-chemical approach was implemented for growth of this CdS@TiO2 architecture. Rutile TiO2 nanorod arrays with lengths of 1–2 mm and diameters of 40–60 nm was synthesized on fluorine-doped tin oxide glass by a hydrothermal process in a titanium tetrachloride precursor solution. CdS quantum dots with a size of 5–10 nm was deposited onto a TiO2 nanorod surface using an ultrasonic-assisted chemical bath deposition method. The resulting CdS quantum dots and TiO2 nanorods formed a type-II heterojunction and showed increased absorption over visible light range. Incident photon-to-current conversion efficiencies (IPCE) as high as 85% and power conversion efficiencies of 2.54% were obtained using a polysulfide electrolyte

TiO2 nanorods with CdS quantum dots for optical applications

We combine CdS semiconductor quantum dots and single-crystalline rutile TiO2 nanorod arrays to produce a practical quantum dot sensitized solar cell. A facile wet-chemical approach was implemented for growth of this CdS@TiO2 architecture. Rutile TiO2 nanorod arrays with lengths of 1–2 mm and diameters of 40–60 nm was synthesized on fluorine-doped tin oxide glass by a hydrothermal process in a titanium tetrachloride precursor solution. CdS quantum dots with a size of 5–10 nm was deposited onto a TiO2 nanorod surface using an ultrasonic-assisted chemical bath deposition method. The resulting CdS quantum dots and TiO2 nanorods formed a type-II heterojunction and showed increased absorption over visible light range. Incident photon-to-current conversion efficiencies (IPCE) as high as 85% and power conversion efficiencies of 2.54% were obtained using a polysulfide electrolyte.

Investigation of Reduced Graphene Oxide with F-Doped SnO2 as Catalyst Support in Fuel Cells

A main challenge in commercialisation of fuel cells is the performance loss with time of operation. The platinum catalyst is subjected to electrochemical instability, and carbon black as commonly used catalyst support suffers from corrosion.[1,2] To improve the fuel cell stability, alternative support materials can be used. Application of graphene-based carbon in low temperature PEMFCs has demonstrated higher durability than conventional carbon black.[3] The combination with corrosion resistant metal oxides provides additional binding sites for Pt nanoparticles[4,5] and can prevent graphene materials from restacking causing mass transport limitations in fuel cells.[6] In this study, reduced graphene oxide (rGO) is synthesised in two steps. Graphene oxide is received via Hummer’s method[7] and then thermally reduced to rGO. In the following synthesis, fluorine-doped tin (IV) oxide (FTO) nanoparticles are deposited on rGO sheets. Therefore, a sol-gel method using tin tetrachloride precursor followed by addition of NH4F and hydrothermal treatment is carried out on rGO.[8,9] Figure 1a shows the achieved crystalline FTO structure which is similar to cassiterite tin (IV) oxide. Using Scherrer equation an average FTO particle size of 4.8±0.4 nm is calculated. Transmission electron microscopy (TEM) in Figure 1b reveals successful deposition of the FTO nanoparticles on rGO. In the last synthesis step, Pt is precipitated on FTO-rGO via chemical reduction of chloroplatinic acid with ethylene glycol.[4] Then, Pt/FTO-rGO catalyst is intensively investigated for electrochemical stability under fuel cell operation conditions by the use of an accelerated stress test (AST). Within an electrochemical cell the catalyst is exposed to 1,000 potential cycles between -0.02 and 1.40 VRHE at a scan rate of 500 mV s-1under oxygen saturation. To ensure a holistic analysis of possible catalyst and support degradation, this AST is performed twice. During the first test, a rotating disk electrode allows the study of the oxygen reduction reaction (ORR) mechanism and activity at different rotation speeds (400, 900, 1200, 1600, 2000 and 2500 rpm). The electrochemical active surface area (EASA) is carefully determined by hydrogen underpotential deposition as well as carbon monoxide stripping voltammetry. In the second test run, the rotating disk electrode as working electrode is replaced by a catalyst coated grid for identical location TEM analysis. First, the untested Pt/FTO-rGO catalyst on the grid is analysed by TEM and then the catalyst on grid is stressed by exactly the same potential cycling. After performing AST, the same Pt/FTO-rGO particles are investigated again under the microscope. Thus, possible Pt degradation processes like agglomeration can be revealed which allows the supplementation of electrochemical investigations. Fig. 1: XRD pattern of FTO-rGO with comparison to crystalline structure of cassiterite SnO2 (ICDD 98-000-9463) (a) and TEM image of deposited FTO particles on rGO (b). [1] D. Schonvogel, M. Rastedt, P. Wagner, M. Wark, A. Dyck, Fuel Cells 2016, 16, 480-489. [2] Y. Shao-Horn, W. C. Sheng, S. Chen, P. J. Ferreira, E. F. Holby, D. Morgan, Top. Catal. 2007, 46, 285-305. [3] Y. Shao, S. Zhang, C. Wang, Z. Nie, J. Liu, Y. Wang, Y. Lin, J. Power Sources 2010, 195, 4600-4605. [4] R. Kou, Y. Shao, D. Mei, Z. Nie, D. Wang, C. Wang, V. V. Viswanathan, S. Park, I. A. Aksay, Y. Lin, Y. Wang, J. Liu, J. Am. Chem. Soc. 2011, 133, 2541-2547. [5] Y. Liu, W. E. Mustain, J. Am. Chem. Soc. 2013, 135, 530-533. [6] S. Park, Y. Shao, H. Wan, P. C. Rieke, V. V. Viswanathan, S. A. Towne, L. V. Saraf, J. Liu, Y. Lin, Y. Wang, Electrochem. Commun. 2011, 13, 258-261. [7] S. Ratso, I. Kruusenberg, M. Vikkisk, U. Joost, E. Shulga, I. Kink, T. Kallio, K. Tammeveski, Carbon 2014, 73, 361-370. [8] D.-J. Guo, Z.-H. Jing, J. Colloid Interface Sci. 2011, 359, 257-260. [9] H. Xu, L. Shi, Z. Wang, J. Liu, J. Zhu, Y. Zhao, M. Zhang, S. Yuan, ACS Appl. Mater. Interfaces 2015, 7, 27486-27493. Figure 1

CVD Growth of GeSnSiC Alloys Using Disilane, Digermane, Tin Tetrachloride and Methylsilane

Ge-Sn-Si-C alloys offer a large range of strain engineering which gives the possibility to tailor the material properties for advanced photonic, electronic, photovoltaic and thermoelectric applications. The benefits of Ge-Sn-Si-C alloys are possibilities to obtain a direct-to-indirect transition (for Sn-based alloys) [1], high carrier mobility [2] and low cost process [3]. In this study, Ge1-x-y-zSnxSiyCz layers (0.01≤x≤ 0.24, 0≤y≤0.12 and 0≤z≤0.01) have successfully grown on Ge and Si by using RPCVD technique. It was demonstrated that the quality of epitaxial layers is dependent on the growth parameters, layer thickness and the quality of Ge virtual layer. It was found that a proper strain balance in the matrix during the epitaxy where the Si and Si-C is adjusted carefully compared to Sn flux improves the incorporation of Sn in Ge matrix. This is explained by the compensation of tensile strain induced by Si or Si-C with the compressive strain caused by Sn in order to obtain the minimum energy in Ge matrix. Fig. 1a and 1b show RBS spectra of two GeSnSi samples when the first one has a constant Si flux whereas the sample in Fig. 1b has a graded Si flux within GeSnSi layer. The Sn incorporation improved from 3% to 24% when Si flux was graded.Incorporation of P and B in GeSnSiC matrix has been studied and the effect of dopant concentrations on Sn content has been investigated. A low boron concentration in range of 1017 cm-3 could be incorporated in the epi-layers whereas P-doping in range of 1019 cm-3could be achieved. All Ge1-x-ySnxSiyCz layers were grown at 280-330 °C at 20 torr in a RPCVD reactor. The gas precursors were Si3H8, Ge2H6, 1% B2H6 in H2, 5% PH3 in H2, and SnCl4as Si, Ge, B, P and Sn sources, respectively. The strain in the epi-layers was measured by high-resolution x-ray reciprocal lattice maps (HRRLMs). Transmission electron microscopy (TEM) was applied to detect the defects in the epi-layers and to observe the interfacial quality. The Sn, Si and C content in the samples was measured by Rutherford backscattering spectrometry (RBS) and HRRLMs. The atomic dopant concentration in the epi-layers was measured by secondary ion mass spectrometry (SIMS). Four-probe measurements were done to determine the resistivity of the doped layers.The quality of carrier and reactant gases in terms of oxygen and water vapor was investigated by residual gas analyzer (RGA). The RGA instrument was connected to the exhaust gas output and was situated in 20 mm distance from the reactant gas chamber. A RGA spectrum reveals any absorption or desorption of molecules with accuracy of ppt range. The results showed that the level of oxygen during epitaxy was as low as 10 ppb and the contamination concetration was found as low as 1017 cm-3. This low oxygen level during epitxy is due to the high purity of trisilane, digermane and tetrachloride precursors as well as the hydrogen carrier gas. Acknowledgment The Swedish Research Council (VR) is greatly acknowledged for supporting this work.

Hydrothermal growth of photoelectrochemically active titanium dioxide cauliflower-like nanostructures

Hierarchical titanium dioxide nanostructures have been synthesized by a simple and cost-effective hydrothermal deposition method onto the conducting glass substrates. In order to study the effect of titanium tetrachloride precursor quantity on the growth of TiO2; the thin films of TiO2 have been synthesized with the variations in the TiCl4 from 0.4mL to 1.0mL at the interval of 0.2mL. These films are characterized for their optical, structural, compositional, morphological properties using UV-vis spectrophotometer, Photoluminescence, X-ray Diffraction, High resolution transmission electron microscopy, X-ray Photoelectron Spectroscopy and Field Emission Scanning Electron Microscopy techniques. The optical band gap energy is found to increase from 2.74 to 3.06eV with the increase in TiCl4 quantities exhibiting a blue shift. XRD patterns show the formation of polycrystalline TiO2 with the tetragonal crystal structure possessing rutile phase. Rise in the TiCl4 quantity leads to the decrease in the particle size. The chemical composition and valence states of the constituent elements were analysed by XPS. FESEM images showed the formation of cauliflower-like structure at the highest TiCl4 precursor quantity. The films were photoelectrochemically active with the maximum current density of 202μA/cm2 for the sample prepared at 1.0mL.

Photosensitization of TiO2 nanorods with CdS quantum dots for photovoltaic applications: A wet-chemical approach

We combine CdS semiconductor quantum dots and single-crystalline rutile TiO2 nanorod arrays to produce a practical quantum dot sensitized solar cell. A facile wet-chemical approach was implemented for growth of this CdS@TiO2 architecture. Rutile TiO2 nanorod arrays with lengths of 1–2μm and diameters of 40–60nm were synthesized on fluorine-doped tin oxide glass by a hydrothermal process in a titanium tetrachloride precursor solution. CdS quantum dots with a size of 5–10nm were deposited onto a TiO2 nanorod surface using an ultrasonic-assisted chemical bath deposition method. The resulting CdS quantum dots and TiO2 nanorods formed a type-II heterojunction and showed increased absorption over visible light range. Incident photon-to-current conversion efficiencies (IPCE) as high as 85% and power conversion efficiencies of 2.54% were obtained using a polysulfide electrolyte.

TEM and SEM-CL Studies of SiC Nanowires

-SiC and -SiC/SiO2 core-shell nanowires (NWs) grown on silicon substrates by three different processes, based on the use of i) carbon monoxide, ii) silane with propane and iii) carbon tetrachloride precursors, are analysed by structural and optical techniques. Spectroscopic cathodoluminescence studies show a luminescence enhancement in core-shell structures, ascribed to an effective role of the shell as both carrier injecting barrier and passivation layer. In NWs grown using CCl4 precursor, a peculiar luminescence with dominant red component at about 2 eV has been detected and ascribed to point defects related to an unintentional oxygen incorporation.

Interaction of Alkaline Metal Cations with Oxidic Surfaces: Effect on the Morphology of SnO2Nanoparticles

Reaction pathways to SnO(2) nanomaterials through the hydrolysis of hydrated tin tetrachloride precursors were investigated. The products were prepared solvothermally starting from hydrated tin tetrachloride and various (e.g., alkali) hydroxides. The influence of the precursor base on the final morphology of the nanomaterials was studied. X-ray powder diffraction (XRD) data indicated the formation of rutile-type SnO(2). Transmission electron microscopy (TEM) studies revealed different morphologies that were formed with different precursor base cations. Data from molecular dynamics (MD) simulations provide theoretical evidence that the adsorption of the cations of the precursor base to the faces of the growing SnO(2) nanocrystals is crucial for the morphology of the nanostructures.

Characterization of Porous Titania and Ceria Ceramics by Small-Angle Neutron Scattering

Titania powder was prepared by a solution based hydroxide precipitation technique using the tetrachloride precursor and ammonia as the precipitating agent. Ceria powder was prepared by homogeneous precipitation method using cerium nitrate and hexamethylenetetramine. The particle size distribution of titania and ceria powders was measured by laser light scattering. The powder particles were found to follow a log-normal size distribution and the average size of the particles for both the powders was ∼0.7 microns. Small-angle neutron scattering (SANS) was used to study the sintering behaviour and evolution of pore morphology in sintered compacts of titania and ceria by varying the sintering temperature/time. The SANS profiles were analyzed in the light of poly-disperse spherical pore model using log-normal size distribution. The pore sizes in both the ceramic compacts varied from 10 to 1000 nm and the mean value of the distribution shifted from a lower, 50 nm to a higher, 350 nm size. This trend could be attributed to both densification and grain growth occurring in the compacts with the progress of sintering.