Showing papers on "Silicon oxide published in 2017"

Silicon/Organic Hybrid Solar Cells with 16.2% Efficiency and Improved Stability by Formation of Conformal Heterojunction Coating and Moisture-Resistant Capping Layer

Abstract: Silicon/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) heterojunction solar cells with 16.2% efficiency and excellent stability are fabricated on pyramid-textured silicon substrates by applying a water-insoluble ester as capping layer. This shows that a conformal coating of PEDOT:PSS on textured silicon can greatly improve the junction quality with the main stability failure routes related to the moisture-induced poly(3,4-ethylenedioxythiophene) aggregations and the tunneling silicon oxide autothickening.

Semiconductor device and method for fabricating the same

Abstract: A semiconductor device including a logic transistor, a non-volatile memory (NVM) cell and a contact etching stop layer (CESL) is shown. The CESL includes a first silicon nitride layer on the logic transistor but not on the NVM cell, a silicon oxide layer on the first silicon nitride layer and on the NVM cell, and a second silicon nitride layer disposed on the silicon oxide layer over the logic transistor and disposed on the silicon oxide layer on the NVM cell.

Tin oxide thin film spacers in semiconductor device manufacturing

Abstract: Thin tin oxide films are used as spacers in semiconductor device manufacturing. In one implementation, thin tin oxide film is conformally deposited onto a semiconductor substrate having an exposed layer of a first material (e.g., silicon oxide or silicon nitride) and a plurality of protruding features comprising a second material (e.g., silicon or carbon). For example, 10-100 nm thick tin oxide layer can be deposited using atomic layer deposition. Next, tin oxide film is removed from horizontal surfaces, without being completely removed from the sidewalls of the protruding features. Next, the material of protruding features is etched away, leaving tin oxide spacers on the substrate. This is followed by etching the unprotected portions of the first material, without removal of the spacers. Next, underlying layer is etched, and spacers are removed. Tin-containing particles can be removed from processing chambers by converting them to volatile tin hydride.

Highly Stable Molybdenum Disulfide Protected Silicon Photocathodes for Photoelectrochemical Water Splitting

Abstract: Developing materials, interfaces, and devices with improved stability remains one of the key challenges in the field of photoelectrochemical water splitting. As a barrier to corrosion, molybdenum disulfide is a particularly attractive protection layer for photocathodes due to its inherent stability in acid, the low permeability of its basal planes, and the excellent hydrogen evolution reaction (HER) activity the MoS2 edge. Here, we demonstrate a stable silicon photocathode containing a protecting layer consisting of molybdenum disulfide, molybdenum silicide, and silicon oxide which operates continuously for two months. We make comparisons between this system and another molybdenum sulfide–silicon photocathode embodiment, taking both systems to catastrophic failure during photoelectrochemical stability measurements and exploring mechanisms of degradation. X-ray photoelectron spectroscopy and transmission electron microscopy provide key insights into the origins of stability.

Pinhole density and contact resistivity of carrier selective junctions with polycrystalline silicon on oxide

Abstract: In the pursuit of ever higher conversion efficiencies for silicon photovoltaic cells, polycrystalline silicon (poly-Si) layers on thin silicon oxide films were shown to form excellent carrier-selective junctions on crystalline silicon substrates. Investigating the pinhole formation that is induced in the thermal processing of the poly-Si on oxide (POLO) junctions is essential for optimizing their electronic performance. We observe the pinholes in the oxide layer by selective etching of the underlying crystalline silicon. The originally nm-sized pinholes are thus readily detected using simple optical and scanning electron microscopy. The resulting pinhole densities are in the range of 6.6 × 106 cm−2 to 1.6 × 108 cm−2 for POLO junctions with selectivities close to S10 = 16, i.e., saturation current density J0c below 10 fA/cm2 and contact resistivity ρc below 10 mΩcm2. The measured pinhole densities agree with values deduced by a pinhole-mediated current transport model. Thus, we conclude pinhole-mediated current transport to be the dominating transport mechanism in the POLO junctions investigated here.

Methods for forming a semiconductor structure and related semiconductor structures

Abstract: A method for forming a forming a semiconductor structure is disclosed. The method may include: forming a silicon oxide layer on a surface of a substrate, depositing a silicon germanium (Si 1-x Ge x ) seed layer directly on the silicon oxide layer, and depositing a germanium (Ge) layer directly on the silicon germanium (Si 1-x Ge x ) seed layer. Semiconductor structures including a germanium (Ge) layer deposited on silicon oxide utilizing an intermediate silicon germanium (Si 1-x Ge x ) seed layer are also disclosed.

Electrochemical Formation of a p–n Junction on Thin Film Silicon Deposited in Molten Salt

Abstract: Herein we report the demonstration of electrochemical deposition of silicon p–n junctions all in molten salt. The results show that a dense robust silicon thin film with embedded junction formation can be produced directly from inexpensive silicates/silicon oxide precursors by a two-step electrodeposition process. The fabricated silicon p–n junction exhibits clear diode rectification behavior and photovoltaic effects, indicating promise for application in low-cost silicon thin film solar cells.

Role of alkali metal promoter in enhancing lateral growth of monolayer transition metal dichalcogenides

Abstract: Synthesis of monolayer transition metal dichalcogenides (TMDs) via chemical vapor deposition relies on several factors such as precursor, promoter, substrate, and surface treatment of substrate. Among them, the use of promoter is crucial for obtaining uniform and large-area monolayer TMDs. Although promoters have been speculated to enhance adhesion of precursors to the substrate, their precise role in the growth mechanism has rarely been discussed. Here, we report the role of alkali metal promoter in growing monolayer TMDs. The growth occurred via the formation of sodium metal oxides which prevent the evaporation of metal precursor. Furthermore, the silicon oxide substrate helped to decrease the Gibbs free energy by forming sodium silicon oxide compounds. The resulting sodium metal oxide was anchored within such concavities created by corrosion of silicon oxide. Consequently, the wettability of the precursors to silicon oxide was improved, leading to enhance lateral growth of monolayer TMDs.

Kinetics and Chemistry of Hydrolysis of Ultrathin, Thermally Grown Layers of Silicon Oxide as Biofluid Barriers in Flexible Electronic Systems.

Abstract: Flexible electronic systems for bioimplants that offer long-term (multidecade) stability and safety in operation require thin, biocompatible layers that can prevent biofluid penetration. Recent work shows that ultrathin films of silicon dioxide thermally grown (TG-SiO2) on device-grade silicon wafers and then released as transferrable barriers offer a remarkable set of attributes in this context. This paper examines the chemical stability of these materials in aqueous solutions with different combinations of chemistries that are present in biofluids. Systematic measurements reveal the dependence of the dissolution rate of TG-SiO2 on concentrations of cations (Na+, K+, Mg2+, Ca2+) and anions (Cl–, HPO42–) at near-neutral pH. Certain results are consistent with previous studies on bulk samples of quartz and nanoparticles of amorphous silica; others reveal significant catalyzing effects associated with divalent cations at high pH and with specific anions at high ionic strength. In particular, Ca2+ and HPO42–...

Fabrication and Modeling of High-Efficiency Front Junction N-Type Silicon Solar Cells With Tunnel Oxide Passivating Back Contact

Abstract: This paper reports on in-depth understanding, modeling, and fabrication of 23.8% efficient 4 cm2 n-type Float Zone (FZ) silicon cells with a selective boron emitter and photolithography contact on front and tunnel oxide passivating contact on the back. Tunnel oxide passivating contact composed of a very thin chemically grown silicon oxide (∼15 A) capped with plasma-enhanced chemical vapor deposition (PECVD) grown 20 nm n+ poly Si gave excellent surface passivation and carrier selectivity with very low saturation current density (∼5 fA/cm2). A high-quality boron selective emitter was formed using ion implantation and solid source diffusion to minimize metal recombination and emitter saturation current density. Process optimization resulted in a cell $V_{{\rm{oc}}}$ of 712 mV, $J_{{\rm{sc}}}$ of 41.2 mA/cm2, and FF of 0.811. A simple methodology is used to model these cells which replaces tunnel oxide passivating contact region by electron and hole recombination velocities extracted from measured saturation current density of tunnel oxide passivating contact region and analysis. Using this approach and two-dimensional device modeling gave an excellent match between the measured and simulated cell parameters and efficiency, supporting excellent passivation and carrier selectivity of these contacts. Extended simulations showed that 26% cell efficiency can be achieved with this cell structure by further optimization of wafer quality, emitter profile, and contact design.

Calibration-free quantitative analysis of thin-film oxide layers in semiconductors using laser induced breakdown spectroscopy (LIBS)

Abstract: The current largest market share and continually growing industry of the semiconductor manufacturing sector in the US demands rapid and cost-effective quality control and characterization of thin film semiconducting materials. To this end, we demonstrate Laser Induced Breakdown Spectroscopy (LIBS) as a facile and effective analytical tool for rapid process-line characterization of metal-oxide-semiconductor (MOS) transistors and capacitors. Specifically, we carry out quantitative LIBS analysis on silicon oxide (SiO2) thin-films of various thicknesses grown by high-temperature moisture-free oxidation on industrial-grade Si wafers. The stoichiometric ratios of oxygen to silicon ([O]/[Si]) in various SiO2 films are measured by LIBS analyses using an internal calibration technique. The results are verified against benchmark analyses based on oxide layer thicknesses and laser-induced crater profile topographies from ellipsometry, scanning electron microscopy (SEM), atomic force microscopy (AFM), and profilometry measurements. The stoichiometric ratios of [O]/[Si] calculated from thickness and profilometry measurements are used to compare with our direct LIBS measurements. Our results indicate good agreement between the LIBS and profilometry calculation results, demonstrating the future capability of LIBS for thin film characterization during their industrial processing.

Thermal conduction across a boron nitride and silicon oxide interface

Abstract: The needs for efficient heat removal and superior thermal conduction in nano/micro devices have triggered tremendous studies in low-dimensional materials with high thermal conductivity. Hexagonal boron nitride (h-BN) is believed to be one of the candidates for thermal management and heat dissipation due to its novel physical properties, i.e. thermal conductor and electrical insulator. Here we reported interfacial thermal resistance between few-layer h-BN and its silicon oxide substrate using differential 3 omega method. The measured interfacial thermal resistance is around ~1.6*10-8 m2K/W for monolayer h-BN and ~3.4*10-8 m2K/W for 12.8nm-thick h-BN in metal/h-BN/SiO2 interfaces. Our results suggest that the voids and gaps between substrate and thick h-BN flakes limit the interfacial thermal conduction. This work provides a deeper understanding of utilizing h-BN flake as lateral heat spreader in electronic and optoelectronic nano/micro devices with further miniaturization and integration.

What Governs Friction of Silicon Oxide in Humid Environment: Contact Area between Solids, Water Meniscus around the Contact, or Water Layer Structure?

Abstract: In order to understand the interfacial parameters governing the friction force (Ft) between silicon oxide surfaces in humid environment, the sliding speed (v) and relative humidity (RH) dependences of Ft were measured for a silica sphere (1 μm radius) sliding on a silicon oxide (SiOx) surface, using atomic force microscopy (AFM), and analyzed with a mathematical model describing interfacial contacts under a dynamic condition. Generally, Ft decreases logarithmically with increasing v to a cutoff value below which its dependence on interfacial chemistry and sliding condition is relatively weak. Above the cutoff value, the logarithmic v dependence could be divided into two regimes: (i) when RH is lower than 50%, Ft is a function of both v and RH; (ii) in contrast, at RH ≥ 50%, Ft is a function of v only, but not RH. These complicated v and RH dependences were hypothesized to originate from the structure of the water layer adsorbed on the surface and the water meniscus around the annulus of the contact area. This hypothesis was tested by analyzing Ft as a function of the water meniscus area (Am) and volume (Vm) estimated from a thermally activated water-bridge formation model. Surprisingly, it was found that Ft varies linearly with Vm and correlates poorly with Am at RH < 50%; and then its Vm dependence becomes weaker as RH increases above 50%. Comparing the friction data with the attenuated total reflection infrared (ATR-IR) spectroscopy analysis result of the adsorbed water layer, it appeared that the solidlike water layer structure formed on the silica surface plays a critical role in friction at RH < 50% and its contribution diminishes at RH ≥ 50%. These findings give a deeper insight into the role of water condensation in friction of the silicon oxide single asperity contact under ambient conditions.

Applications of Monolayer-Functionalized H-Terminated Silicon Surfaces: A Review

Abstract: Silicon is an attractive semiconductor material for wide-ranging applications, from electronics and sensing to solar cells. Functionalization of H-terminated silicon surfaces with molecular monolayers can be used to tune the properties of the material toward a desired application. Several applications require the removal of the, often insulating, silicon oxide between the silicon surface and a monolayer, thus precluding the more conventional silane-based chemistry. Here, the applications of monolayer-functionalized silicon surfaces are surveyed starting from H-terminated silicon. The oxide-free routes available for Si–C, Si–N, Si–O–C, and Si–S bond formation are described, of which the most commonly used techniques include hydrosilylation and a chlorination/alkylation route onto H-terminated silicon. Applications are subdivided into the areas of surface passivation, electronics, doping, optics, biomedical devices, and sensors. Overall, these methods provide great prospects for the development of stabilized silicon micro-/nanosystems with engineered functionalities.

Preparation method of metal mono-atoms

Abstract: The invention relates to a preparation method of metal mono-atoms and belongs to the technical field of materials science and engineering The metal mono-atoms prepared through the method may include: Pt, Ag, Au, Pd, Rh, Ir, Ru, Co, Ni and Cu, and metal mono-atoms supported on TiO2, zinc oxide, cerium oxide, aluminum oxide, silicon oxide, ferric oxide, manganese oxide, C3N4, mesoporous carbon, ultrathin carbon films, graphene, carbon nano tubes or molecular sieve materials, etc The method includes the steps of: preparing a precursor solution in a certain concentration, and freezing the solution; and under an ice phase, processing ice cubes by means of external field or reaction between reactants in the ice cubes, and when the ice cubes are molten, a mono-atom solution is finally produced; mixing the mono-atom solution with different materials, performing ultrasonic treatment, filtration, cleaning and drying to finally obtain the mono-atoms supported on various materials The preparation method is quick, has high product density, allows mass production, is high in efficiency and has wide application range, and compared with a co-precipitation method and an impregnation method, the method has significant advantages

Synthesis of Electrical Conductive Silica Nanofiber/Gold Nanoparticle Composite by Laser Pulses and Sputtering Technique

Abstract: Biocompatible-sensing materials hold an important role in biomedical applications where there is a need to translate biological responses into electrical signals. Increasing the biocompatibility of these sensing devices generally causes a reduction in the overall conductivity due to the processing techniques. Silicon is becoming a more feasible and available option for use in these applications due to its semiconductor properties and availability. When processed to be porous, it has shown promising biocompatibility; however, a reduction in its conductivity is caused by its oxidization. To overcome this, gold embedding through sputtering techniques are proposed in this research as a means of controlling and further imparting electrical properties to laser induced silicon oxide nanofibers. Single crystalline silicon wafers were laser processed using an Nd:YAG pulsed nanosecond laser system at different laser parameters before undergoing gold sputtering. Controlling the scanning parameters (e.g., smaller line spacings) was found to induce the formation of nanofibrous structures, whose diameters grew with increasing overlaps (number of laser beam scanning through the same path). At larger line spacings, nano and microparticle formation was observed. Overlap (OL) increases led to higher light absorbance’s by the wafers. The gold sputtered samples resulted in greater conductivities at higher gold concentrations, especially in samples with smaller fiber sizes. Overall, these findings show promising results for the future of silicon as a semiconductor and a biocompatible material for its use and development in the improvement of sensing applications.

Low temperature SiOx thin film deposited by plasma enhanced atomic layer deposition for thin film encapsulation applications

Abstract: Silicon oxide (SiOx) films were synthesized by plasma enhanced atomic layer deposition (PEALD) using di-isopropylaminosilane [SiH3N(C3H7)2] as the precursor and an oxygen plasma as the reactant. The layers were characterized with respect to different growth temperatures between 60 and 150 °C. The film density and surface roughness values measured by x-ray reflectometry and atomic force microscopy all approached those of thermally grown SiOx. Also, reasonably high breakdown voltages were observed at all deposition temperatures. An interesting phenomenon involves the fact that the SiOx layer deposited at 60 °C is most effective as a moisture barrier, as it exhibits the lowest water vapor transmission rate. X-ray photoelectron spectroscopy analyses indicate that the silicon monoxide bonding characteristic becomes more pronounced as the growth temperature decreases. It is conjectured that such a difference in the bonding state renders the surface of the low temperature SiOx films rather hydrophobic, which sup...

Selective growth of silicon nitride

Abstract: Methods and apparatuses for selectively depositing silicon nitride on silicon surfaces relative to silicon oxide surfaces and selectively depositing silicon nitride on silicon oxide surfaces relative to silicon surfaces are provided herein. Methods involve blocking one surface while leaving another surface unblocked and selectively depositing silicon nitride on the unblocked surface. The blocked surface may include an organic moiety having an Si—C bond. The method may include blocking one of an exposed hydroxyl-terminated silicon-containing surface and an exposed hydrogen-terminated silicon-containing surface of the substrate. Apparatuses include a process chamber having a pedestal, an outlet, and a controller for providing instructions for causing delivery of a semiconductor substrate to the pedestal, causing introduction of a silicon-containing precursor and causing introduction of a nitrogen-containing reactant without igniting a plasma.

Control of the interaction strength of photonic molecules by nanometer precise 3D fabrication.

Abstract: Applications for high resolution 3D profiles, so-called grayscale lithography, exist in diverse fields such as optics, nanofluidics and tribology. All of them require the fabrication of patterns with reliable absolute patterning depth independent of the substrate location and target materials. Here we present a complete patterning and pattern-transfer solution based on thermal scanning probe lithography (t-SPL) and dry etching. We demonstrate the fabrication of 3D profiles in silicon and silicon oxide with nanometer scale accuracy of absolute depth levels. An accuracy of less than 1nm standard deviation in t-SPL is achieved by providing an accurate physical model of the writing process to a model-based implementation of a closed-loop lithography process. For transfering the pattern to a target substrate we optimized the etch process and demonstrate linear amplification of grayscale patterns into silicon and silicon oxide with amplification ratios of ∼6 and ∼1, respectively. The performance of the entire process is demonstrated by manufacturing photonic molecules of desired interaction strength. Excellent agreement of fabricated and simulated structures has been achieved.