Showing papers on "Silicon oxide published in 2016"

Controlled Prelithiation of Silicon Monoxide for High Performance Lithium-Ion Rechargeable Full Cells

Abstract: Despite the recent considerable progress, the reversibility and cycle life of silicon anodes in lithium-ion batteries are yet to be improved further to meet the commercial standards. The current major industry, instead, adopts silicon monoxide (SiOx, x ≈ 1), as this phase can accommodate the volume change of embedded Si nanodomains via the silicon oxide matrix. However, the poor Coulombic efficiencies (CEs) in the early period of cycling limit the content of SiOx, usually below 10 wt % in a composite electrode with graphite. Here, we introduce a scalable but delicate prelithiation scheme based on electrical shorting with lithium metal foil. The accurate shorting time and voltage monitoring allow a fine-tuning on the degree of prelithiation without lithium plating, to a level that the CEs in the first three cycles reach 94.9%, 95.7%, and 97.2%. The excellent reversibility enables robust full-cell operations in pairing with an emerging nickel-rich layered cathode, Li[Ni0.8Co0.15Al0.05]O2, even at a commerci...

Semiconductor memory device and method for manufacturing same

Abstract: A laminated body is formed by alternately laminating a plurality of dielectric films and electrode films on a silicon substrate. Next, a through hole extending in the lamination direction is formed in the laminated body. Next, a selective nitridation process is performed to selectively form a charge layer made of silicon nitride in a region of an inner surface of the through hole corresponding to the electrode film. Next, a high-pressure oxidation process is performed to form a block layer made of silicon oxide between the charge layer and the electrode film. Next, a tunnel layer made of silicon oxide is formed on an inner side surface of the through hole. Thus, a flash memory can be manufactured in which the charge layer is split for each electrode film.

Selective deposition on metal or metallic surfaces relative to dielectric surfaces

Abstract: Methods are provided for selectively depositing a material on a first metal or metallic surface of a substrate relative to a second, dielectric surface of the substrate, or for selectively depositing metal oxides on a first metal oxide surface of a substrate relative to a second silicon oxide surface. The selectively deposited material can be, for example, a metal, metal oxide, metal nitride, metal silicide, metal carbide and/or dielectric material. In some embodiments a substrate comprising a first metal or metallic surface and a second dielectric surface is alternately and sequentially contacted with a first vapor-phase metal halide reactant and a second reactant. In some embodiments a substrate comprising a first metal oxide surface and a second silicon oxide surface is alternately and sequentially contacted with a first vapor phase metal fluoride or chloride reactant and water.

Ultrasound synthesis of lead halide perovskite nanocrystals

Abstract: We report the ultrasound-induced synthesis of APbX3 perovskite nanocrystals with a wide range of compositions, where A = CH3NH3, Cs, or HNCHNH3 (formamidinium), and X = Cl, Br, or I Ultrasonic irradiation accelerates dissolution of the precursors (AX and PbX2) in toluene, and the dissolution rate determines the growth rate of the nanocrystals We fabricated high-sensitivity photodetectors by homogenously spin coating the uniform size nanocrystals on large-area silicon oxide substrates

Atomic-Level Understanding toward a High-Capacity and High-Power Silicon Oxide (SiO) Material

Abstract: Silicon oxide (SiO) has attracted much attention as a promising anode material for Li-ion batteries. The lithiation of SiO results in the formation of active Li–Si alloy cores embedded in an inactive matrix consisting of Li-silicates (Li2Si2O5, Li6Si2O7, and Li4SiO4) and Li2O. The maximum Li content in lithiated SiO (LixSiO) is known to be x = 4.4 based on experiments. Our calculations reveal that Li-silicates are dominant over Li2O among matrix components of the experimental Li4.4SiO phase. We show that LixSiO can become thermodynamically more stable and thus accommodate more Li ions up to x = 5.2 when Li2O dominates over Li-silicates. The minor portion of Li2O in the experimental phase is attributed to kinetically difficult transformations of Li-silicates into Li2O during electrochemical lithiation. The Li2O subphase can act as a major transport channel for Li ions because the Li diffusivity in Li2O is calculated to be faster by at least 2 orders of magnitude than in Li-silicates. We suggest that Li2O i...

Thermo-Optic Characterization of Silicon Nitride Resonators for Cryogenic Photonic Circuits

Abstract: In this paper, we characterize the Thermo-optic properties of silicon nitride ring resonators between 18 and 300 K. The Thermo-optic coefficients of the silicon nitride core and the oxide cladding are measured by studying the temperature dependence of the resonance wavelengths. The resonant modes show low temperature dependence at cryogenic temperatures and higher dependence as the temperature increases. We find the Thermo-optic coefficients of PECVD silicon nitride and silicon oxide to be $2.51 \pm 0.08\ \text{E}$ - $5\ \text{K}^{-1}$ and $0.96 \pm 0.09\ \text{E}$ - $5\ \text{K}^{-1}$ at room temperature while decreasing by an order of magnitude when cooling to 18 K. To show the effect of variations in the thermo-optic coefficients on device performance, we study the tuning of a fully integrated electrically tunable filter as a function of voltage for different temperatures. The presented results provide new practical guidelines in designing photonic circuits for studying low-temperature optical phenomena.

Silicon selective removal

Abstract: A method of etching exposed silicon on patterned heterogeneous structures is described and includes a gas phase etch using plasma effluents formed in a remote plasma The remote plasma excites a fluorine-containing precursor Plasma effluents within the remote plasma are flowed into a substrate processing region where the plasma effluents combine with a hydrogen-containing precursor The combination react with the patterned heterogeneous structures to remove an exposed silicon portion faster than a second exposed portion The silicon selectivity results from the presence of an ion suppressor positioned between the remote plasma and the substrate processing region The methods may be used to selectively remove silicon faster than silicon oxide, silicon nitride and a variety of metal-containing materials The methods may be used to remove small etch amounts in a controlled manner and may result in an extremely smooth silicon surface

III/V nano ridge structures for optical applications on patterned 300 mm silicon substrate

Abstract: We report on an integration approach of III/V nano ridges on patterned silicon (Si) wafers by metal organic vapor phase epitaxy (MOVPE). Trenches of different widths (≤500 nm) were processed in a silicon oxide (SiO2) layer on top of a 300 mm (001) Si substrate. The MOVPE growth conditions were chosen in a way to guarantee an efficient defect trapping within narrow trenches and to form a box shaped ridge with increased III/V volume when growing out of the trench. Compressively strained InGaAs/GaAs multi-quantum wells with 19% indium were deposited on top of the fully relaxed GaAs ridges as an active material for optical applications. Transmission electron microcopy investigation shows that very flat quantum well (QW) interfaces were realized. A clear defect trapping inside the trenches is observed whereas the ridge material is free of threading dislocations with only a very low density of planar defects. Pronounced QW photoluminescence (PL) is detected from different ridge sizes at room temperature. The po...

A method to derivatize surface silanol groups to Si-alkyl groups in carbon-doped silicon oxides

Abstract: A carbon-doped silicon oxide (CDO) finds use as a material with a low dielectric constant (k) for copper interconnects in multilayered integrated circuits (ICs). Hydrophilic silanol groups (Si–OH) on its surface, however, can attract moisture, thereby causing an undesirable increase in the dielectric constant. Modification of the exposed hydrophilic surface to a hydrophobic functional group provides one solution to this problem. We report here a strategy for converting surface Si–OH to hydrophobic silicon hydride (Si–H) without affecting the internal oxide network in CDO. The approach involves esterification of the exposed silanol to its triflate (silyltrifluoromethanesulfonate, Si–O–Tf), followed by reduction to Si–H with diisobutylaluminum hydride. Si–H is further modified by a photochemical reaction with an alkene (1-octadecene) to yield Si–R (R = –C18H37) to provide a more moisture resistant, and less polar Si–C as opposed to the Si–O backbone. Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectrometry (XPS), and measurements of the contact angle with water substantiated the successful conversion. The reaction scheme is versatile, transforming silanol groups to silicon hydride in widely varying chemical sites, from small molecules to the surfaces of silica gels, SiOx and CDO wafers. A comparison with the films (self-assembled monolayers) derivatized with the octadecyltrichlorosilane indicated that the new method leads to a thicker (≈5 nm) but more loosely packed hydrocarbon film with slightly lower contact angles.

Effects of Water on Tribochemical Wear of Silicon Oxide Interface: Molecular Dynamics (MD) Study with Reactive Force Field (ReaxFF).

Abstract: Molecular dynamics (MD) simulations with the ReaxFF reactive force field were carried out to find the atomistic mechanisms for tribochemical reactions occurring at the sliding interface of fully hydroxylated amorphous silica and oxidized silicon as a function of interfacial water amount. The ReaxFF-MD simulations showed a significant amount of atom transfers across the interface occurs during the sliding. In the absence of water molecules, the interfacial mixing is initiated by dehydroxylation followed by the Si-O-Si bond formation bridging two solid surfaces. In the presence of submonolayer thick water, the dissociation of water molecules can provide additions reaction pathways to form the Si-O-Si bridge bonds and atom transfers across the interface. However, when the amount of interfacial water molecules is large enough to form a full monolayer, the degree of atom transfer is substantially reduced since the silicon atoms at the sliding interface are terminated with hydroxyl groups rather than forming interfacial Si-O-Si bridge bonds. The ReaxFF-MD simulations clearly showed the role of water molecules in atomic scale mechanochemical processes during the sliding and provided physical insights into tribochemical wear processes of silicon oxide surfaces observed experimentally.

5L-Scale Magnesio-Milling Reduction of Nanostructured SiO2 for High Capacity Silicon Anodes in Lithium-Ion Batteries

Abstract: Nanostructured silicon (Si) is useful in many applications and has typically been synthesized by bottom-up colloid-based solution processes or top-down gas phase reactions at high temperatures. These methods, however, suffer from toxic precursors, low yields, and impractical processing conditions (i.e., high pressure). The magnesiothermic reduction of silicon oxide (SiO2) has also been introduced as an alternative method. Here, we demonstrate the reduction of SiO2 by a simple milling process using a lab-scale planetary-ball mill and industry-scale attrition-mill. Moreover, an ignition point where the reduction begins was consistently observed for the milling processes, which could be used to accurately monitor and control the reaction. The complete conversion of rice husk SiO2 to high purity Si was demonstrated, taking advantage of the rice husk’s uniform nanoporosity and global availability, using a 5L-scale attrition-mill. The resulting porous Si showed excellent performance as a Li-ion battery anode, r...

Tunable nanoporous silicon oxide templates by swift heavy ion tracks technology.

Abstract: Nanoporous silicon oxide templates formed by swift heavy ion tracks technology have been investigated. The influence of the heavy ion characteristics, such as type of ion, energy, stopping power and irradiation fluence on the pore properties of the silicon oxide templates, has been studied. Furthermore, the process of pore formation by chemical etching with hydrofluoric acid has been thoroughly investigated by assessing the effect of etchant concentration and etching time. The outcome of this investigation enables us to have precise control over the resulting geometry of nanopores arrays. As a result, guidelines for the creation of a-SiO2/Si templates with tunable parameters and general recommendations for their further application are presented.

High aspect ratio 3-d flash memory device

Abstract: Methods of selectively etching tungsten from the surface of a patterned substrate are described. The etch electrically separates vertically arranged tungsten slabs from one another as needed, for example, in the manufacture of vertical flash memory devices. The tungsten etch may selectively remove tungsten relative to films such as silicon, polysilicon, silicon oxide, aluminum oxide, titanium nitride and silicon nitride. The methods include exposing electrically-shorted tungsten slabs to remotely-excited fluorine formed in a capacitively-excited chamber plasma region. The methods then include exposing the tungsten slabs to remotely-excited fluorine formed in an inductively-excited remote plasma system. A low electron temperature is maintained in the substrate processing region during each operation to achieve high etch selectivity.

Silicon-Rich Silicon Carbide Hole-Selective Rear Contacts for Crystalline-Silicon-Based Solar Cells.

Abstract: The use of passivating contacts compatible with typical homojunction thermal processes is one of the most promising approaches to realizing high-efficiency silicon solar cells. In this work, we investigate an alternative rear-passivating contact targeting facile implementation to industrial p-type solar cells. The contact structure consists of a chemically grown thin silicon oxide layer, which is capped with a boron-doped silicon-rich silicon carbide [SiCx(p)] layer and then annealed at 800–900 °C. Transmission electron microscopy reveals that the thin chemical oxide layer disappears upon thermal annealing up to 900 °C, leading to degraded surface passivation. We interpret this in terms of a chemical reaction between carbon atoms in the SiCx(p) layer and the adjacent chemical oxide layer. To prevent this reaction, an intrinsic silicon interlayer was introduced between the chemical oxide and the SiCx(p) layer. We show that this intrinsic silicon interlayer is beneficial for surface passivation. Optimized p...

Nanoscale Transformations in Metastable, Amorphous, Silicon-Rich Silica.

Abstract: Electrically biasing thin films of amorphous, substoichiometric silicon oxide drives surprisingly large structural changes, apparent as density variations, oxygen movement, and ultimately, emission of superoxide ions. Results from this fundamental study are directly relevant to materials that are increasingly used in a range of technologies, and demonstrate a surprising level of field-driven local reordering of a random oxide network.

Saving ion-damaged spacers

Abstract: Methods of selectively removing silicon oxide are described. Exposed portions of silicon oxide and spacer material may both be present on a patterned substrate. The silicon oxide may be a native oxide formed on silicon by exposure to atmosphere. The exposed portion of spacer material may have been etched back using reactive ion etching (RIE). A portion of the exposed spacer material may have residual damage from the reactive ion etching. A self-assembled monolayer (SAM) is selectively deposited over the damaged portion of spacer material but not on the exposed silicon oxide or undamaged portions of spacer material. A subsequent gas-phase etch may then be used to selectively remove silicon oxide but not the damaged portion of the spacer material because the SAM has been found to not only preferentially adsorb on the damaged spacer but also to halt the etch rate.

Fluorocarbon assisted atomic layer etching of SiO2 and Si using cyclic Ar/C4F8 and Ar/CHF3 plasma

Abstract: The need for atomic layer etching (ALE) is steadily increasing as smaller critical dimensions and pitches are required in device patterning. A flux-control based cyclic Ar/C4F8 ALE based on steady-state Ar plasma in conjunction with periodic, precise C4F8 injection and synchronized plasma-based low energy Ar+ ion bombardment has been established for SiO2 [Metzler et al., J. Vac. Sci. Technol. A 32, 020603 (2014)]. In this work, the cyclic process is further characterized and extended to ALE of silicon under similar process conditions. The use of CHF3 as a precursor is examined and compared to C4F8. CHF3 is shown to enable selective SiO2/Si etching using a fluorocarbon (FC) film build up. Other critical process parameters investigated are the FC film thickness deposited per cycle, the ion energy, and the etch step length. Etching behavior and mechanisms are studied using in situ real time ellipsometry and x-ray photoelectron spectroscopy. Silicon ALE shows less self-limitation than silicon oxide due to higher physical sputtering rates for the maximum ion energies used in this work, ranged from 20 to 30 eV. The surface chemistry is found to contain fluorinated silicon oxide during the etching of silicon. Plasma parameters during ALE are studied using a Langmuir probe and establish the impact of precursor addition on plasma properties.

Enhanced Performance of Si MIS Photocathodes Containing Oxide-Coated Nanoparticle Electrocatalysts

Abstract: Electrodepositing low loadings of metallic nanoparticle catalysts onto the surface of semiconducting photoelectrodes is a highly attractive approach for decreasing catalyst costs and minimizing optical losses. However, securely anchoring nanoparticles to the photoelectrode surface can be challenging—especially if the surface is covered by a thin insulating overlayer. Herein, we report on Si-based photocathodes for the hydrogen evolution reaction that overcome this problem through the use of a 2–10 nm thick layer of silicon oxide (SiOx) that is deposited on top of Pt nanoparticle catalysts that were first electrodeposited on a 1.5 nm SiO2|p-Si(100) absorber layer. Such insulator–metal–insulator–semiconductor (IMIS) photoelectrodes exhibit superior durability and charge transfer properties compared to metal–insulator–semiconductor (MIS) control samples that lacked the secondary SiOx overlayer. Systematic investigation of the influence of particle loading, SiOx layer thickness, and illumination intensity sug...

Compositions and methods using same for carbon doped silicon containing films

Abstract: Described herein are compositions and methods using same for forming a silicon-containing film such as, without limitation, a carbon doped silicon oxide film, a carbon doped silicon nitride, a carbon doped silicon oxynitride film in a deposition process. In one aspect, the composition comprises at least cyclic carbosilane having at least one Si-C-Si linkage and at least one anchoring group selected from a halide atom, an amino group, and combinations thereof.

SELECTIVE SiN LATERAL RECESS

Abstract: Exemplary methods for laterally etching silicon nitride may include flowing a fluorine-containing precursor and an oxygen-containing precursor into a remote plasma region of a semiconductor processing chamber. The methods may include forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor and the oxygen-containing precursor. The methods may also include flowing the plasma effluents into a processing region of the semiconductor processing chamber. A substrate may be positioned within the processing region, and the substrate may include a trench formed through stacked layers including alternating layers of silicon nitride and silicon oxide. The methods may also include laterally etching the layers of silicon nitride from sidewalls of the trench while substantially maintaining the layers of silicon oxide. The layers of silicon nitride may be laterally etched less than 10 nm from the sidewalls of the trench.

Impact of the Ga Droplet Wetting, Morphology, and Pinholes on the Orientation of GaAs Nanowires

Abstract: Ga-catalyzed growth of GaAs nanowires on Si is a candidate process for achieving seamless III/V integration on IV. In this framework, the nature of silicon’s surface oxide is known to have a strong influence on nanowire growth and orientation and therefore important for GaAs nanowire technologies. We show that the chemistry and morphology of the silicon oxide film controls liquid Ga nucleation position and shape; these determine GaAs nanowire growth morphology. We calculate the energies of formation of Ga droplets as a function of their volume and the oxide composition in several nucleation configurations. The lowest energy Ga droplet shapes are then correlated to the orientation of nanowires with respect to the substrate. This work provides the understanding and the tools to control nanowire morphology in self-assembly and pattern growth.

Ultrathin Titanium Dioxide Nanolayers by Atomic Layer Deposition for Surface Passivation of Crystalline Silicon

Abstract: We demonstrate a low surface recombination velocity of 14 cm/s with only 1.5 nm thin titanium dioxide (TiO2 ) layers on undiffused 10 Ωcm p-type crystalline silicon. The TiO2 nanolayers were deposited by thermal atomic layer deposition at 150 °C and 200 °C substrate temperatures using tetrakis-dimethyl-amido titanium as the Ti precursor and water as the oxidant. The influence of a post-deposition anneal in forming gas at different temperatures was investigated. We have observed that a subsequent anneal in forming gas at 350 °C enhances the surface passivation quality of the TiO2 layers tremendously. Increasing the thickness of the TiO2 layers leads to a reduction of the surface passivation quality. Introducing a thin interfacial layer of silicon oxide (1.6 nm) grown by rapid thermal oxidation underneath the TiO2 layer improves the surface passivation of thicker TiO2 layers (5.5 and 15 nm). These results show that ultrathin TiO2 layers with a thickness of only 1.5 nm can be used to effectively passivate the c-Si surface.

Electron Transport and Electrolyte Reduction in the Solid-Electrolyte Interphase of Rechargeable Lithium Ion Batteries with Silicon Anodes

Abstract: Understanding the molecular processes that lead to the formation, structure, and transport properties of the solid electrolyte interphase (SEI) found in lithium ion batteries with silicon anodes is of paramount importance for the development of lithium ion batteries (LiB) capable of performing under the extreme exigencies of our present energy needs that are solved presently with nonrenewable energies. We use a combined density functional theory (DFT) and Green’s function approach (DFT-GF) to study the electron transport characteristics in selected finite models of materials formed at the SEI located between the silicon surface of the anode of Li-ion batteries and the electrolyte solvent. The SEI products examined are lithium carbonate (LiCO3) silicon oxide (SiO2) and lithium disilicate (Li2Si2O5). Results show that the leakage of electrons from the Si anode to the solvent is greatly reduced (up to 4 orders of magnitude) with the addition and growth of the SEI components as compared with the solvent-anode...

Interfacial nitrogen stabilizes carbon-coated mesoporous silicon particle anodes

Abstract: We report for the first time that the dehydrogenation process of PAN was suppressed and the silicon oxide of the MSP surface was reduced during annealing in Ar + H2. Consequently, the remaining –NH bonds of the carbon chain can interact with the fresh amorphous Si on the surface of the MSPs to form a Si–N–C layer, which improves the adhesion between Si and C and serves as a stable electrolyte blocking layer. In addition, based on micron-sized MSPs, the structural stability of the electrode is dramatically enhanced through in situ formation of Si nanocrystals of less than 5 nm. The low Li+ diffusion kinetics of the Si–N–C layer and self limiting inhomogeneous lithiation in MSPs jointly create unlithiated Si nanocrystals, acting as supporting frames to prevent pulverization of the anode material. Our nitriding MSP anode has exhibited for the first time a 100% capacity retention (394 mA h g−1) after 2000 cycles (10 cycles each at 0.1, 0.5, 1, 2, and 1 and then 1950 cycles at 0.5 A g−1) and a 100% capacity retention at 0.1 A g−1 (540 mA h g−1) after 400 cycles. Thus, our work proposes a novel avenue to engineer battery materials with large volume changes.

Surface etching, chemical modification and characterization of silicon nitride and silicon oxide--selective functionalization of Si3N4 and SiO2.

Abstract: The ability to selectively chemically functionalize silicon nitride (Si3N4) or silicon dioxide (SiO2) surfaces after cleaning would open interesting technological applications. In order to achieve this goal, the chemical composition of surfaces needs to be carefully characterized so that target chemical reactions can proceed on only one surface at a time. While wet-chemically cleaned silicon dioxide surfaces have been shown to be terminated with surficial Si-OH sites, chemical composition of the HF-etched silicon nitride surfaces is more controversial. In this work, we removed the native oxide under various aqueous HF-etching conditions and studied the chemical nature of the resulting Si3N4 surfaces using infrared absorption spectroscopy (IRAS), x-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS), and contact angle measurements. We find that HF-etched silicon nitride surfaces are terminated by surficial Si-F and Si-OH bonds, with slightly subsurface Si-OH, Si-O-Si, and Si-NH2 groups. The concentration of surficial Si-F sites is not dependent on HF concentration, but the distribution of oxygen and Si-NH2 displays a weak dependence. The Si-OH groups of the etched nitride surface are shown to react in a similar manner to the Si-OH sites on SiO2, and therefore no selectivity was found. Chemical selectivity was, however, demonstrated by first reacting the -NH2 groups on the etched nitride surface with aldehyde molecules, which do not react with the Si-OH sites on a SiO2 surface, and then using trichloro-organosilanes for selective reaction only on the SiO2 surface (no reactivity on the aldehyde-terminated Si3N4 surface).