Showing papers on "Substrate (electronics) published in 1997"

Sculptured thin films and glancing angle deposition: Growth mechanics and applications

Abstract: Sculptured thin films with three dimensional microstructure controlled on the 10 nm scale were fabricated with an evaporation technique. Glancing angle deposition (GLAD) and substrate motion were employed to “sculpt” columnar thin film microstructure into desired forms ranging from zigzag shaped to helical to four-sided “square” helical. Computer control of substrate motion was used to accurately position the substrate and to achieve the desired film structures. The growth mechanics of this novel thin film deposition technique are investigated with density measurements, scanning electron microscopy analysis, and measurements of effective refractive index. Adatom diffusion and atomic shadowing are the dominant growth mechanisms with glancing angle deposition conditions creating extreme shadowing. With controlled rotation of the substrate about two axes during deposition, a dense capping layer can be produced on top of the porous sculptured films. The success of the capping process was found to be strongly ...

Thick GaN Epitaxial Growth with Low Dislocation Density by Hydride Vapor Phase Epitaxy

Abstract: Thick GaN layers were grown by hydride vapor phase epitaxy (HVPE) with the aim of using these layers as a homoepitaxial substrate to improve device quality of laser diodes or light emitting diodes. HVPE is very useful for thick layer growth since the growth rate can reach from several ten up to one hundred micron per hour. In this experiment, the growth began as selective growth through openings formed in a SiO2 mask. Facets consisting of {1101} planes were formed in the early stage and a continuous film developed from the coalescence of these facets on the SiO2 mask. As a result, GaN layers with a dislocation density as low as 6×107 cm-2 were grown on 2-inch-diameter sapphire wafers. These GaN layers were crack-free and had mirror-like surface.

Structural, electrical and optical properties of aluminum doped zinc oxide films prepared by radio frequency magnetron sputtering

Abstract: Aluminum doped zinc oxide (AZO) films are prepared by rf magnetron sputtering on glass or Si substrates using specifically designed ZnO targets containing different amount of Al2O3 powder as the Al doping source. The structural, electrical, and optical properties of the AZO films are investigated in terms of the preparation conditions, such as the Al2O3 content in the target, rf power, substrate temperature and working pressure. The crystal structure of the AZO films is hexagonal wurtzite. The orientation, regardless of the Al content, is along the c axis perpendicular to the substrate. The doping concentration in the film is 1.9 at. % for 1 wt % Al2O3 target, 4.0 at. % for 3 wt % Al2O3 target, and 6.2 at. % for 5 wt % Al2O3 target. The resistivity of the AZO film prepared with the 3 wt % Al2O3 target is ∼4.7×10−4 Ω cm, and depends mainly on the carrier concentration. The optical transmittance of a 1500-A-thick film at 550 nm is ∼90%. The optical band gap depends on the Al doping level and on the microstr...

Ultra-thin epitaxial films of graphite and hexagonal boron nitride on solid surfaces

Abstract: In this article, we have reviewed the recent progress of the experimental studies on ultra-thin films of graphite and hexagonal boron nitride (h-BN) by using angle-resolved electron spectroscopy together with other techniques. The fundamental properties of these high-quality films are discussed on the basis of the data on dispersion relations of valence electrons, phonon dispersion etc. The interfacial orbital mixing of the -state of the monolayer graphite (MG) with the d states of the reactive substrates is the origin for the phonon softening, expansion of the nearest-neighbour C - C distance, modification of the -band, low work function, and two-dimensional plasmons with high electron density, etc. In the cases of weak mixing at the interface between the MG and relatively inert substrates, the observed properties of the MG are very close to the bulk ones. In contrast to the case for MG, the interfacial interaction between the h-BN monolayer and the substrate is weak.

Smart-cut process for the production of thin semiconductor material films

Abstract: A process applicable to the production of monocrystalline films improves on the Smart-Cut® process by using an etch stop layer in conjunction with the Smart-Cut® process. Because of the etch stop layer, no chemical-mechanical polishing (CMP) is required after fabrication. Thus, the thickness and smoothness of the device layer in the fabricated silicon on insulator (SOI) substrate is determined by the uniformity and smoothness of the deposited layers and wet etch selectivity, as opposed to the CMP parameters. Therefore, the smoothness and uniformity of the device layer are improved.

Integrated heterostructures of group III-V nitride semiconductor materials including epitaxial ohmic contact comprising multiple quantum well

Abstract: An integrated heterostructure of Group III-V nitride compound semiconductors is formed on a multicomponent platform which includes a substrate of monocrystalline silicon carbide and a non-nitride buffer layer of monocrystalline zinc oxide. The zinc oxide may be formed by molecular beam epitaxy (MBE) using an MBE effusion cell containing zinc, and a source of atomic oxygen, such as an MBE-compatible oxygen plasma source which converts molecular oxygen into atomic oxygen. An ohmic contact for a semiconductor device formed of Group III-V nitride compound semiconductor materials including a layer of aluminum nitride or aluminum gallium nitride, includes a continuously graded layer of aluminum gallium nitride and a layer of gallium nitride or an alloy thereof on the continuously graded layer. The continuously graded layer eliminates conduction or valence band offsets. A multiple quantum well may also be used instead of the continuously graded layer where the thickness of the layers of gallium nitride increase across the multiple quantum well. The ohmic contacts may be used for Group III-V nitride laser diodes, light emitting diodes, electron emitters, bipolar transistors and field effect transistors.

Structure and composition of passive titanium oxide films

Abstract: The thickness and composition of several kinds of titanium oxide films formed on a titanium substrate were determined by surface analysis techniques: X-ray photoelectron spectroscopy, Rutherford back scattering, X-ray diffraction and atomic force microscopy. Most titanium oxide samples were prepared by anodisation, using a galvanostatic procedure. The films were shown to be composed of an amorphous TiO2 outer layer (10–20 nm thick) and an intermediate TiOx layer, in contact with the TiO2 layer and the metallic substrate. The outer layer is sensitive to the environment: its thickness usually decreases with ageing in a corrosive solution. A stabilisation procedure was proposed in order to improve its ability to withstand corrosion.

Reduced-Temperature Solid Oxide Fuel Cell Based on YSZ Thin-Film Electrolyte

Abstract: A planar thin-film solid oxide fuel cell has been fabricated with an inexpensive, scalable, technique involving colloidal deposition of yttria-stabilized zirconia (YSZ) films on porous NiO-YSZ substrates, yielding solid oxide fuel cells capable of exceptional power density at operating temperatures of 700 to 800°C. The thickness of the YSZ film deposited onto the porous substrate is approximately 10 Rim after sintering, and is well bonded to the NiO/YSZ substrate. Ni-YSZ/YSZ/LSM cells built with this technique have exhibited theoretical open-circuit potentials (OCPs), high current densities, and exceptionally good power densities of over 1900 mW/cm 2 at 800°C. Electrochemical characterization of the cells indicates negligible losses across the Ni-YSZ/YSZ interface and minor polarization of the fuel electrode. Thinfilm cells have been tested for long periods of time (over 700 h) and have been thermally cycled from 650 to 800°C while demonstrating excellent stability over time.

Antireflection behavior of silicon subwavelength periodic structures for visible light

Abstract: We describe subwavelength surfaces etched into silicon wafers that exhibit antireflection characteristics for visible light. The wafers are fabricated by holographically recording a crossed-grating in a photoresist mask followed by reactive-ion etching to transfer the primary mask onto the silicon substrate. The dependence of reflectivity on the wavelength and angle of incidence is measured. The overall antireflection performance of the corrugated silicon wafers is compared with that of standard thin-film stacks, and is interpreted with the effective medium theory and with simulation results obtained from rigorous computations.

Organic electroluminescent device

Abstract: In an organic electroluminescent device including a substrate and formed thereon a multilayered structure successively having at least an anode layer, an organic electroluminescent layer and a cathode layer, a sealing layer having at least one compound selected from the group consisting of a metal oxide, a metal fluoride and a metal sulfide is further provided on the electrode layer formed later A hole injecting and transporting layer is preferably provided between the anode layer and the organic electroluminescent layer An electron injecting and transporting layer may also be provided between the organic electroluminescent layer and the cathode layer At least one layer of the hole injecting and transporting layer, organic electroluminescent layer and electron injecting and transporting layer may be formed of a polyphosphazene compound or a polyether compound or a polyphosphate compound having an aromatic tertiary amine group in its main chain

Method for forming high dielectric constant metal oxides

Abstract: A method for forming a metal gate (20) structure begins by providing a semiconductor substrate (12). The semiconductor substrate (12) is cleaned to reduce trap sites. A nitrided layer (14) having a thickness of less than approximately 20 Angstroms is formed over the substrate (12). This nitrided layer prevents the formation of an oxide at the substrate interface and has a dielectric constant greater than 3.9. After the formation of the nitrided layer(14), a metal oxide layer (16) having a permittivity value of greater than roughly 8.0 is formed over the nitrided layer (14). A metal gate (20) is formed over the nitrided layer whereby the remaining composite gate dielectric (14 and 16) has a larger physical thickness but a high-performance equivalent oxide thickness (EOT).

Interfacial Segregation in Disordered Block Copolymers: Effect of Tunable Surface Potentials

Abstract: The response of disordered P({ital d}-S-{ital b}-MMA) diblock copolymers to variable strength surface fields has been studied by neutron reflectivity. Surface interactions were controlled by end grafting P(S-{ital r}-MMA) random copolymers with various styrene contents onto Si substrates. The degree interfacial segregation of the block copolymer was proportional to the surface potential. A first-order transition in the degree of segregation was observed as the brush composition was varied. Conditions were found which yielded neutral boundary conditions {ital simultaneously} at the vacuum and substrate interfaces. {copyright} {ital 1997} {ital The American Physical Society}

Optical Process for Liftoff of Group III-Nitride Films

Abstract: Films of GaN have been separated from a sapphire growth substrate by illuminating the interface with a pulsed ultraviolet laser that induces localized thermal decomposition of the GaN. Free-standing films and devices can be produced in this way. This process is also an alternative to surface etching for patterning of films and can be used for other nitride materials and more complex film systems by choosing an appropriate illumination wavelength or by including a strategically placed sacrificial absorbing layer during the film growth. This process exploits the thermally activated decomposition of GaN that begins to occur above about 800 C, resulting in the effusion of nitrogen gas. We have recently shown that this decomposition can be induced with high spatial resolution by heating the material with a short laser pulse (less than 10 ns). The rapid generation of heat allows a high localized temperature to be reached before the heat is conducted out of the illuminated region. In this way, surface patterning was achieved at illumination intensities above about 0.2 J/cm{sup 2} with 355 nm wavelength, near the absorption threshold of GaN. (orig.)

Energy level alignment at organic/metal interfaces studied by UV photoemission: breakdown of traditional assumption of a common vacuum level at the interface

Abstract: Electronic structures of model interfaces of organic electroluminescent (EL) devices and porphyrin/metal interfaces were investigated by UV photoemission spectroscopy (UPS). At all the measured interfaces, shift of the vacuum level was observed, showing the formation of an interfacial electric dipole layer. For Alq/sub 3/ (tris(8-hydroxyquinolino) aluminum), TPD (N,N'-diphenyl-N,N'-(3-methylphenyl)-1,1-biphenyl-4,4'-diamine), and DP-NTCI (N,N'-diphenyl-1,4,5,8-naphthyltetracarboxylimide)/metal interfaces, interfacial energy diagrams determined by UPS correspond well with the actually observed carrier-injecting character at the interfaces. For ZnTPP (15,10,15,20-zinc-tetraphenylporphyrin), H/sub 2/TPP (5,10,15,20-tetraphenylporphyrin), and H/sub 2/T(4-Py)P (5,10,15,20-tetra(4-pyridyl) porphyrin)/metal interfaces, the shifts of the vacuum level as well as the energies of the levels in porphyrins could be expressed as a linear function of work function of the metal substrate. The slope of the linear function depended on the compound. These findings are in contrast to the traditional assumption of common vacuum level at the interfaces, For ZnTPP/metal interfaces, sample exposure to oxygen induced energy level shift in close relation with the change of the substrate work function at oxygen exposure. The present results have clearly demonstrated that direct observation of the interfacial electronic structure by microscopic method such as UPS is necessary for understanding the organic electronic devices such as EL devices and organic solar cells.

Single-crystal Si films for thin-film transistor devices

Abstract: The fact that single-crystal Si would make an ideal material for thin-film transistor devices has long been recognized. Despite this awareness, a viable method by which such a material could be directly produced on a glass substrate has never been formulated. In this letter, it is shown experimentally that location-controlled single-crystal Si regions on a SiO2 surface can be obtained in a glass-substrate compatible manner, via excimer-laser-based sequential lateral solidification of thin Si films using a beamlet shape that self-selects and extends a single grain over an arbitrarily large area. This is accomplished by controlling the locations, shape, and extent of melting induced by the incident excimer-laser pulses, in such a manner as to induce interface-contour-affected sequential super-lateral growth of crystals, during which the tendency of grain boundaries to align approximately orthogonal to the solidifying interface is systematically exploited.

Process for production of semiconductor substrate

Abstract: A process for producing a semiconductor substrate is provided which comprises steps of forming a porous layer on a first substrate, forming a nonporous monocrystalline semiconductor layer on the porous layer of the first substrate, bonding the nonporous monocrystalline layer onto a second substrate, separating the bonded substrates at the porous layer, removing the porous layer on the second substrate, and removing the porous layer constituting the first substrate.

Substrate dependence on the optical properties of Al2O3 films grown by atomic layer deposition

Abstract: The atomic layer deposition technique has been applied to the growth of Al2O3 thin films on the substrates of Si(100), 100-nm-thick SiO2 covered Si(100) [SiO2/Si(100)], and 90-nm-thick TiN covered SiO2/Si(100). The growth rate of Al2O3 films was 0.19 nm/cycle and identical for all substrates employed under the surface controlled process. However, the optical properties of Al2O3 films were significantly affected by different substrates. The average interband-oscillator energy and refractive index parameter were determined to be 3.330 eV and 2.992×10−14 eV m2 for Al2O3 film grown on Si(100), while those for the film grown on SiO2/Si(100) were 4.492 eV and 2.074×10−14 eV m2, respectively.

Chamber seasoning method to improve adhesion of F-containing dielectric film to metal for VLSI application

Abstract: The present invention provides a method of depositing an amorphous fluorocarbon film using a high bias power applied to the substrate on which the material is deposited. The invention contemplates flowing a carbon precursor at rate and at a power level so that equal same molar ratios of a carbon source is available to bind the fragmented fluorine in the film thereby improving film quality while also enabling improved gap fill performance. The invention further provides for improved adhesion of the amorphous fluorocarbon film to metal surfaces by first depositing a metal or TiN adhesion layer on the metal surfaces and then stuffing the surface of the deposited adhesion layer with nitrogen. Adhesion is further improved by coating the chamber walls with silicon nitride or silicon oxynitride.

Semiconductor device method for producing the same and liquid crystal display including the same

Abstract: A liquid crystal display device including: a display section including a liquid crystal layer; a pair of substrates interposing the liquid crystal layer; a plurality of pixel electrodes located in a matrix on one of the pair of substrates; a plurality of first thin film transistors respectively connected to the plurality of pixel electrodes; and a peripheral driving circuit located for driving the display section, the peripheral driving circuit being located on the substrate on which the first thin film transistors are located and having a second thin film transistor. Each of the first thin film transistors includes a first channel layer formed of a first crystalline silicon layer, and the second thin film transistor includes a second channel layer formed of a second crystalline silicon layer having a higher mobility than the mobility of the first crystalline silicon layer. The second crystalline silicon layer includes a catalytic element for promoting crystallization.

Organic light emitting diodes having transparent cathode structures

Abstract: Organic light emitting diodes having a transparent cathode structure is disclosed. The structure consists of a low work function metal in direct contact with the electron transport layer of the OLED covered by a layer of a wide bandgap semiconductor. Calcium is the preferred metal because of its relatively high optical transmissivity for a metal and because of its proven ability to form a good electron injecting contact to organic materials. ZnSe, ZnS or an alloy of these materials are the preferred semiconductors because of their good conductivity parallel to the direction of light emission, their ability to protect the underlying low work function metal and organic films and their transparency to the emitted light. Arrays of these diodes, appropriately wired, can be used to make a self-emissive display. When fabricated on a transparent substrate, such a display is at least partially transparent making it useful for heads-up display applications in airplanes and automobiles. Such a display can also be fabricated on an opaque substrate, such as silicon, in which previously fabricated devices and circuits can be used to drive the display.

Solar battery module

Abstract: PROBLEM TO BE SOLVED: To decrease the lattice defect density of the III-V compound semiconductor film on an amorphous film by a method wherein an amorphous film is formed on the III-V compound semiconductor film formed in a heterogeneous substrate, a window is perforated, a III-VB compound semiconductor film is formed on the amorphous film using the window as a nucleus, and a solar battery is arranged therein. SOLUTION: The III-V compound semiconductor film 2 formed on a heterogeneous substrate is composed of a III-V compound semiconductor film, having the lattice constant approximate to that of GaAs, formed on the substrate 1. An amorphous film 3 is formed by oxidizing the III-V compound semiconductor film. Windows 4 are formed by photolithography and etching. A III-V compound semiconductor film 5 can be formed by the growth method generating no polycrystalline in a dielectric film such as a MOCVD method and the like. As the lower layers of the III-V compound semiconductor film 2 and the III-V group semiconductor film 5 are separated by the amorphous film 3, only the lattice defect generated in the windows 4 affects on the III-V compound semiconductor film 5, defect density does not affect the deterioration of efficiency of a solar battery 6, and lattice defect density can be lowered.

Microwave monolithic integrated circuit with coplaner waveguide having silicon-on-insulator composite substrate

Abstract: A microwave monolithic integrated circuit includes a coplanar waveguide (CPW) formed by a composite silicon structure constituted by a relatively high resistivity substrate, a first oxide layer on the upper surface thereof, a relatively thin silicon layer formed on the surface of the first oxide layer, and a very thin second oxide layer formed on the surface of the thin silicon layer. The silicon layer and the first oxide layer on which it is formed constitutes a silicon-on-insulator or SOI structure. A metallic signal line and ground planes are bonded to the surface of the second oxide layer. The zone of the thin silicon layer which extends between the ground planes is doped with an active impurity to produce high conductivity therein. As a result, the electric component of a quasi-TEM wave traversing the waveguide is substantially restricted to the thin silicon layer and does not penetrate to the underlying bulk silicon substrate. This achieves significantly reduced transmission loss and a quality factor Q in the vicinity of 17 for the CPW. Passive and active circuits may be formed in regions of the thin silicon layer other than those used for the CPW.

Orientation-controlled organic electroluminescence of p-sexiphenyl films

Abstract: A multilayered electroluminescent device was constructed with epitaxially oriented films of p-sexiphenyl with its molecular axis lying or standing next to the substrate surface. The films with the lying and standing orientations were prepared by vapor deposition onto the KCl (001) surface kept at 20 and 150 °C, respectively. After successive depositions of electron-transport layer and Al cathode, the films were removed from the KCl substrate and transferred on an indium tin oxide coated glass anode. The cell with lying molecules emitted a higher electroluminescence with a narrowed spectrum at remarkably low driving voltages, as compared to one with standing molecules. This electroluminescent behaviors depend upon anisotropic distribution of the polarized emission light as well as efficiency of the carrier transport in the ordered molecular arrays with different orientation modes.

Scanning force microscopic exploration of the lubrication capabilities of n-alkanethiolate monolayers chemisorbed at gold : Structural basis of microscopic friction and wear

Abstract: This paper explores the ability of n-alkanethiolates chemisorbed at Au(111) to function as boundary lubricants at microscopic length scales as probed by scanning force microscopy (SFM). Through an examination of the influence of alkyl chain length, we show that the macroscopic structure of this system, as developed from insights into the chain-packing density via infrared reflection spectroscopy, greatly influences the observed friction and wear. That is, the longer chain monolayers exhibit a markedly lower friction and a reduced propensity to wear than the shorter chain monolayers, a situation that reflects the more extensive cohesive interactions between chains. From the combined weight of these findings, we examine the frictional process within the context of an activation mechanism that involves pressure and shear activation volumes. The ability of longer chain alkanethiolate monolayers to lubricate features that arise from changes in substrate topography is also presented, and the resulting mechanist...

Technique for producing small islands of silicon on insulator

Abstract: Using sub-micron technology, silicon on insulator (SOI) rows and islands are formed in a silicon substrate. Trenches are directionally-etched in the silicon substrate, leaving rows of silicon between the trenches. Silicon nitride is then deposited over the trenches, extending partly down the sides of the trenches. An isotropic chemical etch is then used to partially undercut narrow rows of silicon in the substrate. A subsequent oxidation step fully undercuts the rows of silicon, isolating the silicon rows from adjacent active areas. Devices, such as transistors for CMOS and DRAMs, are then formed in active areas, wherein the active areas are defined on the silicon rows by LOCal Oxidation of Silicon (LOCOS).

Electroluminescent element and manufacture thereof

Abstract: PROBLEM TO BE SOLVED: To manufacture a highly reliable electroluminescent element which has a wide surface area and whose electric power consumption is low by forming a poly phenylene vinylene PPV film with the thickness within a specified μm range on the surface of a first charge injection contact layer. SOLUTION: Using a borosilicate glass 1 as a glass substrate, a first electric charge injection contact layer 2 is formed on the upper face of the substrate. This electric charge injection contact layer 2 is formed by thermal evaporation of aluminum through a shadow mask and the resultant substrate is exposed to air to form a thin film surface oxidized layer 3 and the electric charge injection contact layer is thus obtained. Next, a polymer solution is applied to the whole surface area of a joining substrate and while keeping the upper face in a horizontal state, the substrate is rotated at a specified rotation speed on an axis and the resultant substrate coated with a polymer precursor layer is thermally treated in a vacuum oven to convert the precursor into poly phenylene vinylene PPV. The obtained PPV film 4 has 100-300nm thickness. After that, a second electric charge injection contact layer 5 is formed on the PPV film 4 by evaporation of gold or aluminum and an electric charge injection contact layer with 20-30nm thickness is thus obtained.