Showing papers on "Silicon nitride published in 2008"

Bioinspired Self‐Cleaning Antireflection Coatings

Abstract: Millions of years before we began to generate functional nanostructures, biological systems were using nanometer-scale architectures to produce unique functionalities. For instance, moths use hexagonal arrays of nonclose-packed (ncp) nipples as antireflection coatings (ARCs) to reduce reflectivity from their compound eyes. The outer surface of the corneal lenses of moths consists of ncp arrays of conical protuberances, termed corneal nipples, typically of sub-300 nm height and spacing. These arrays of subwavelength nipples generate a graded transition of refractive index, leading to minimized reflection over a broad range of wavelengths and angles of incidence. Similar periodic arrays of ncp pillars have also been observed on the wings of cicada to render superhydrophobic surfaces for self-cleaning functionality. In this Communication, we report a simple and scalable bioinspired templating technique for fabricating broadband and superhydrophobic ARCs on technologically important silicon and glass substrates. Crystalline silicon is the most important material for solar cells. Unfortunately, due to the high refractive index of silicon, more than 30% of incident light is reflected back from the surface of crystalline silicon. ARCs are therefore widely utilized to reduce the unwanted reflective losses. Quarterwavelength silicon nitride (SiNx) films deposited by plasmaenhanced chemical vapor deposition (PECVD) are the industrial standard for ARCs on crystalline silicon substrates. However, the PECVD-deposited SiNx films are expensive to fabricate. Additionally, commercial SiNx ARCs are typically designed to suppress reflection efficiently at wavelengths around 600 nm. The reflective loss is rapidly increased for near-infrared and other visible wavelengths, which contain a large portion of the incident solar energy. In contrast, subwavelength-structured moth-eye ARCs directly patterned in the substrates are broadband and intrinsically more stable and durable than multilayer ARCs since no foreign material is involved. Nevertheless, current topdown lithographic technologies in creating subwavelength

Thermal and Kerr nonlinear properties of plasma-deposited silicon nitride/ silicon dioxide waveguides.

Abstract: We introduce and present experimental evaluations of loss and nonlinear optical response in a waveguide and an optical resonator, both implemented with a silicon nitride/ silicon dioxide material platform prepared by plasma-enhanced chemical vapor deposition with dual frequency reactors that significantly reduce the stress and the consequent loss of the devices. We measure a relatively small loss of approximately 4dB/cm in the waveguides. The fabricated ring resonators in add-drop and all-pass arrangements demonstrate quality factors of Q=12,900 and 35,600. The resonators are used to measure both the thermal and ultrafast Kerr nonlinearities. The measured thermal nonlinearity is larger than expected, which is attributed to slower heat dissipation in the plasma-deposited silicon dioxide film. The n2 for silicon nitride that is unknown in the literature is measured, for the first time, as 2.4 x 10(-15)cm(2)/W, which is 10 times larger than that for silicon dioxide.

High quality mechanical and optical properties of commercial silicon nitride membranes

Abstract: We have measured the optical and mechanical loss of commercial silicon nitride membranes. We find that 50nm thick, 1mm2 membranes have mechanical Q>106 at 293K, and Q>107 at 300mK, well above what has been observed in devices with comparable dimensions. The near-IR optical loss at 293K is less than 2×10−4. This combination of properties make these membranes attractive candidates for studying quantum effects in optomechanical systems.

Atomic layer deposition processes for non-volatile memory devices

Abstract: Embodiments of the invention provide memory devices and methods for forming memory devices. In one embodiment, a memory device is provided which includes a floating gate polysilicon layer disposed over source/drain regions of a substrate, a silicon oxynitride layer disposed over the floating gate polysilicon layer, a first aluminum oxide layer disposed over the silicon oxynitride layer, a hafnium silicon oxynitride layer disposed over the first aluminum oxide layer, a second aluminum oxide layer disposed over the hafnium silicon oxynitride layer, and a control gate polysilicon layer disposed over the second aluminum oxide layer. In another embodiment, a memory device is provided which includes a control gate polysilicon layer disposed over an inter-poly dielectric stack disposed over a silicon oxide layer disposed over the floating gate polysilicon layer. The inter-poly dielectric stack contains two silicon oxynitride layers separated by a silicon nitride layer.

Design of a silicon nitride photonic crystal nanocavity with a Quality factor of one million for coupling to a diamond nanocrystal.

Abstract: A photonic crystal nanocavity with a Quality (Q) factor of 1.4 x 10(6), a mode volume of 0.78(lambda/n)(3), and an operating wavelength of 637 nm is designed in a silicon nitride (SiN(x)) ridge waveguide with refractive index of 2.0. The effect on the cavity Q factor and mode volume of single diamond nanocrystals of various sizes and locations embedded in the center and on top of the nanocavity is simulated, demonstrating that Q > 1 x 10(6) is achievable for realistic parameters. An analysis of the figures of merit for cavity quantum electrodynamics reveals that strong coupling between an embedded diamond nitrogen-vacancy center and the cavity mode is achievable for a range of cavity dimensions.

Method of forming silicon-containing films

Abstract: A method of forming a silicon-containing film comprising providing a substrate in a reaction chamber, injecting into the reaction chamber at least one silicon-containing compound; injecting into the reaction chamber at least one co-reactant in the gaseous form; and reacting the substrate, silicon-containing compound, and co-reactant in the gaseous form at a temperature equal to or less than 550°C to obtain a silicon-containing film deposited onto the substrate. A method of preparing a silicon nitride film comprising introducing a silicon wafer to a reaction chamber; introducing a silicon-containing compound to the reaction chamber; purging the reaction chamber with an inert gas; and introducing a nitrogen-containing co-reactant in gaseous form to the reaction chamber under conditions suitable for the formation of a monomolecular layer of a silicon nitride film on the silicon wafer.

Plasma enhanced cyclic chemical vapor deposition of silicon-containing films

Abstract: The present invention is a process of plasma enhanced cyclic chemical vapor deposition of silicon nitride, silicon carbonitride, silicon oxynitride, silicon carboxynitride, and carbon doped silicon oxide from alkylaminosilanes having Si-H 3 , preferably of the formula (RR 1 N)SiH 3 wherein R and R 1 are selected independently from C 2 to C 10 , and a nitrogen or oxygen source, preferably ammonia or oxygen, which has been developed to provide films with improved properties such as etching rate, hydrogen concentrations, and stress as compared to films from thermal chemical vapor deposition.

Super-tough silicon nitride with R-curve behavior

Abstract: Silicon nitride with a fracture toughness of 10.6 + or - 0.5 MPa sq rt m has been developed. This tough, nontransforming ceramic exhibits pronounced R-curve behavior. Double cantilever-beam and indentation/strength measurements were used to characterize the R-curve, and good agreement between the two methods was obtained. The high toughness and R-curve behavior of this silicon nitride material is attributed to extensive crack deflection and crack bridging phenomena arising from its unique microstructure. As a result of R-curve behavior, the material exhibits flaw tolerance and is, therefore, characterized by a high Weibull modulus. Furthermore, this ceramic is more damage-tolerant than silicon nitrides with flat crack growth resistance. 19 refs.

Selective etching of silicon nitride

Abstract: Methods for etching dielectric layers comprising silicon and nitrogen are provided herein. In some embodiments, such methods may include providing a substrate having a dielectric layer comprising silicon and nitrogen disposed thereon, forming reactive species from a process gas comprising hydrogen (H2) and nitrogen trifluoride (NF3) using a remote plasma; and etching the dielectric layer using the reactive species. In some embodiments, an oxide layer is disposed adjacent to the dielectric layer. In some embodiments, the flow rate ratio of the process gas can be adjusted such that an etch selectivity of the dielectric layer to at least one of the oxide layer or the substrate is between about 0.8 to about 4.

Low wet etch rate silicon nitride film

Abstract: The present invention pertains to methods of depositing low wet etch rate silicon nitride films on substrates using high-density plasma chemical vapor deposition techniques at substrate temperatures below 600° C. The method additionally involves the maintenance of a relatively high ratio of nitrogen to silicon in the plasma and a low process pressure.

Fabrication of silicon nitride waveguides for visible-light using PECVD: a study of the effect of plasma frequency on optical properties.

Abstract: This paper presents work aimed at optimizing the fabrication of silicon nitride Si(x)N(y) thin-film visible-light planar waveguides using plasma-enhanced chemical vapour deposition (PECVD). The effects of plasma frequency, precursor gas ratio, and thermal annealing in relation to waveguide optical properties (refractive index, propagation losses) are studied. Experimental results over a wide range of precursor gas ratios show convincingly that waveguides fabricated using low-frequency PECVD have lower propagation losses in the visible range compared to waveguides of equal refractive index fabricated with high-frequency PECVD.

On the possibility of silicon nitride as a ceramic for structural orthopaedic implants. Part I: processing, microstructure, mechanical properties, cytotoxicity

Abstract: Notwithstanding the good combination of mechanical and tribological properties, the suitability of silicon nitride for application as prosthesis in bone reconstruction or in articular joints replacements is still controversial. This study aims to design and produce three different silicon nitride-based ceramics and to test the materials. In this Part I the microstructure and mechanical properties evidence outstanding characteristics and the cytotoxicity studies confirm that all the materials are extremely inert and biocompatible. In Part II, the wear performance and the wettability and chemical stability against different aqueous media and physiological solutions are investigated and discussed.

Semiconductor device manufacturing method

Abstract: PROBLEM TO BE SOLVED: To improve flatness of a substrate surface by a shallow trench isolation method. SOLUTION: According to the semiconductor device manufacturing method, a trench 16 is formed on the surface of a semiconductor substrate 10 composed of silicon to surround an element placement region 10a by etching processing that uses a silicon oxide film 12 and a silicon nitride film 14 as a selection mask. Thereafter, a CVD oxide film is formed to embed the trench 16. The CVD oxide film is removed to be flat by CMP processing, and part of the CVD oxide film 18a is left in the trench 16. Anneal processing after implanting Ar + on top surface of the substrate reduces an etch rate of the surface of the film 18a. After the selection mask comprising the films 12, 14 is removed, a silicon oxide film is formed as a sacrifice film, and the sacrifice film is etch-removed. The amount of film 18a reduced by the etching is small, making an element separation region comprising the film 18a substantially flush with the element placement region 10a. COPYRIGHT: (C)2008,JPO&INPIT

High lifetime consumable silicon nitride-silicon dioxide plasma processing components

Abstract: A method of increasing mean time between cleans of a plasma etch chamber and chamber parts lifetimes is provided. Semiconductor substrates are plasma etched in the chamber while using at least one sintered silicon nitride component exposed to ion bombardment and/or ionized halogen gas. The sintered silicon nitride component includes high purity silicon nitride and a sintering aid consisting of silicon dioxide. A plasma processing chamber is provided including the sintered silicon nitride component. A method of reducing metallic contamination on the surface of a silicon substrate during plasma processing is provided with a plasma processing apparatus including one or more sintered silicon nitride components. A method of manufacturing a component exposed to ion bombardment and/or plasma erosion in a plasma etch chamber, comprising shaping a powder composition consisting of high purity silicon nitride and silicon dioxide and densifying the shaped component.

Characterization of rice husks and the products of its thermal degradation in air or nitrogen atmosphere

Abstract: Rice husk is a by-product of rice milling process and are a major waste product of the agricultural industry. They have now become a great source as a raw biomass material for manufacturing value-added silicon composite products, including silicon carbide, silicon nitride, silicon tetrachloride, pure silicon, zeolite, fillers of rubber and plastic composites, adsorbent and support of catalysts. The bulk and true densities of raw rice husk with different moisture and sizes were determined. The rice husk was subjected to pyrolysis in fluidized-bed reactor in air or nitrogen atmosphere.

Fine line printed silicon solar cells exceeding 20% efficiency

Abstract: Silicon solar cells with passivated rear side and laser-fired contacts were produced on float zone material. The front side contacts are built up in two steps, seed and plate. The seed layer is printed using an aerosol jet printer and a silver ink. After firing this seed layer through the silicon nitride layer, the conductive layer is grown by light induced plating. The contact formation is studied on different emitter sheet resistances, 55 Ω/sq, 70 Ω/sq, and on 110 Ω/sq. These emitters are passivated with a PECVD silicon nitride layer which also acts as an anti-reflection coating. Even on the 110 Ω/sq emitters it was possible to reach a fill factor of 80·1%. The electrical properties i.e., the contact resistance of the front side contacts are studied by transfer length model (TLM) measurements. On a cell area of 4 cm2 and emitter sheet resistance of 110 Ω/sq, a record efficiency of 20·3% was achieved. Excellent open-circuit voltage (Voc) and short-circuit current (jsc) values of 661 mV and 38·4 mA/cm2 were obtained due to the low recombination in the 110 Ω/sq emitter and at the passivated rear surface. These results show impressively that it is possible to contact emitter profiles with a very high efficiency potential using optimized printing technologies. Copyright © 2008 John Wiley & Sons, Ltd.

Direct inkjet printing of Si3N4: Characterization of ink, green bodies and microstructure

Abstract: Direct inkjet printing of aqueous ceramic suspensions with high solid content was carried out for generating ceramic layers as well as 3D-components. In this study, silicon nitride (LPS-Si 3 N 4 ) was suspended with organic additives in an aqueous medium. Subsequently the suspension was adapted to this manufacturing technique concerning particle size and deflocculation. Thin layers and micro-scaled 3D-components, e.g. gearwheels and engineering parts, were generated and pressureless sintered. Mechanical properties (fracture toughness K Ic , hardness) and microstructure of printed LPS-Si 3 N 4 were evaluated. Results show that dense structures with good mechanical properties were obtained. No delamination or other flaw-like textures were observed. The high potential for direct inkjet printing to manufacture high performance silicon nitride ceramics is thus demonstrated.

Nitric acid pretreatment for the passivation of boron emitters for n-type base silicon solar cells

Abstract: We have developed a simple method to passivate industrially produced boron-doped emitters for n-type base silicon solar cells using an ultrathin (∼1.5nm) silicon dioxide layer between the silicon emitter and the silicon nitride antireflection coating film. This ultrathin oxide is grown at room temperature by soaking the silicon wafers in a solution of nitric acid prior to the deposition of the silicon nitride antireflection coating film. The n-type solar cells processed in such a way demonstrate a conversion efficiency enhancement of more than 2% absolute over the solar cells passivated without the silicon dioxide layer.

Introducing a Metal Layer Between Sin and Tin to Improve CBD Contact Resistance for P-TSV

Abstract: The present disclosure provide an integrated circuit. The integrated circuit includes a through-silicon-via (TSV) trench configured in a semiconductor substrate; a conductive pad formed on the semiconductor substrate, the conductive pad being adjacent the TSV trench; a silicon nitride layer disposed over the conductive pad and in the TSV trench; a titanium layer disposed on the silicon nitride layer; a titanium nitride layer disposed on the titanium layer; and a copper layer disposed on the titanium nitride layer.

High efficiency silicon nitride surface grating couplers

Abstract: High efficiency surface grating couplers for silicon nitride waveguides have been designed, fabricated, and characterized. Coupling efficiencies exceeding 60 % are reported at a wavelength of 1.31 ...

On the possibility of silicon nitride as a ceramic for structural orthopaedic implants. Part II: chemical stability and wear resistance in body environment

Abstract: In Part I, the processing, microstructure and mechanical properties of three silicon nitride-based ceramics were examined and their non-toxicity was demonstrated. In this Part II, some features critical to biomedical applications were investigated: (i) the wetting behaviour against aqueous media, including physiological solutions; (ii) the chemical stability in water and in physiological solutions; and (iii) the wear resistance, measured under experimental procedures that simulate the conditions typical of the hip joint prosthesis. The results confirmed that silicon nitride may serve as a biomaterial for bone substitution in load bearing prosthesis.

Fourier transform infrared spectroscopy of annealed silicon-rich silicon nitride thin films

Abstract: A correlation between bonding changes in silicon-rich silicon nitride films, subjected to high temperature annealing under N2 ambient, and the formation of silicon nanocrystals is presented. The postannealing appearance of a shoulder between 1000 and 1100 cm−1 in the Fourier transform infrared (FTIR) spectra of silicon-rich silicon nitride films is attributed to a reordering in the films toward an increased SiN4 bonding configuration resulting from the precipitation of silicon nanocrystals. The FTIR monitoring of bonding changes in these films allows for the indirect verification of silicon nanocrystal formation.

Methods for removing silicon nitride and other materials during fabrication of contacts

Abstract: Methods for removing silicon nitride and elemental silicon during contact preclean process involve converting these materials to materials that are more readily etched by fluoride-based etching methods, and subsequently removing the converted materials by a fluoride-based etch. Specifically, silicon nitride and elemental silicon may be treated with an oxidizing agent, e.g., with an oxygen-containing gas in a plasma, or with O 2 or O 3 in the absence of plasma to produce a material that is more rich in Si—O bonds and is more easily etched with a fluoride-based etch. Alternatively, silicon nitride or elemental silicon may be doped with a number of doping elements, e.g., hydrogen, to form materials which are more easily etched by fluoride based etches. The methods are particularly useful for pre-cleaning contact vias residing in a layer of silicon oxide based material because they minimize the unwanted increase of critical dimension of contact vias.

Near-field imaging of Bloch surface waves on silicon nitride one-dimensional photonic crystals.

Abstract: We perform a near-field mapping of Bloch Surface Waves excited at the truncation interface of a planar silicon nitride multilayer. We directly determine the field distribution of Bloch Surface Waves along the propagation direction and normally to the surface. Furthermore, we present a direct measurement of a near-field enhancement effect under particular coupling conditions. Experimental evidence demonstrates that a ~102 near-field intensity enhancement can be realistically attained, thus confirming predictions from rigorous calculations.

Microhotplates with TiN heaters

Abstract: Titanium nitride (TiN) has been investigated as a heater material for microhotplates and microreactors. TiN is available in many CMOS processes, unlike many other microheater materials. In addition, TiN has a very high melting point (2950 ◦C) meaning that it is stable up to higher temperatures than platinum (Pt) and polysilicon. For the first time, TiN is tested inside a conventional membrane of LPCVD silicon nitride (SiN). Two types of sputtered TiN are considered: high stress and low stress. Their performance is compared with that of e-beam evaporated Pt. The maximum average temperature of TiN heaters is 11% higher than those of Pt, and reaches over 700 ◦C. Failure of the TiN heaters is due to rupture of the membrane. Failure of the Pt heater is due to electro-stress migration. For high-stress TiN, the temperature coefficient of resistance is almost constant and close to that of Pt, making the material very suitable for temperature sensing. In the case of low-stress TiN the temperature coefficient of resistance (TCR) becomes nonlinear and changes sign. The large differences between the materials are explained by the grain structure. The different grain structures are related to the sputtering parameters according to the Thornton model.

Passivation of wide band-gap based semiconductor devices with hydrogen-free sputtered nitrides

Abstract: A passivated semiconductor structure and associated method are disclosed. The structure includes a silicon carbide substrate or layer; an oxidation layer on the silicon carbide substrate for lowering the interface density between the silicon carbide substrate and the thermal oxidation layer; a first sputtered non-stoichiometric silicon nitride layer on the thermal oxidation layer for reducing parasitic capacitance and minimizing device trapping; a second sputtered non-stoichiometric silicon nitride layer on the first layer for positioning subsequent passivation layers further from the substrate without encapsulating the structure; a sputtered stoichiometric silicon nitride layer on the second sputtered layer for encapsulating the structure and for enhancing the hydrogen barrier properties of the passivation layers; and a chemical vapor deposited environmental barrier layer of stoichiometric silicon nitride for step coverage and crack prevention on the encapsulant layer.

Enhanced light emission in photonic crystal nanocavities with Erbium-doped silicon nanocrystals

Abstract: Photonic crystal nanocavities are fabricated in silicon membranes covered by thermally annealed silicon-rich nitride films with Erbium-doped silicon nanocrystals Silicon nitride films were deposited by sputtering on top of silicon on insulator wafers The nanocavities were carefully designed in order to enhance emission from the nanocrystal sensitized Erbium at the 1540nm wavelength Experimentally measured quality factors of ∼6000 were found to be consistent theoretical predictions The Purcell factor of 14 was estimated from the observed 20-fold enhancement of Erbium luminescence