Showing papers on "Fabrication published in 1995"

Atomic‐scale formation of ultrasmooth surfaces on sapphire substrates for high‐quality thin‐film fabrication

Abstract: The atomically ultrasmooth surfaces with atomic steps of sapphire substrates were obtained by annealing in air at temperatures between 1000 and 1400 °C. The terrace width and atomic step height of the ultrasmooth surfaces were controlled on an atomic scale by changing the annealing conditions and the crystallographic surface of substrates. The obtained ultrasmooth surface was stable in air. The topmost atomic structure of the terrace was examined quantitatively by atomic force microscopy and ion scattering spectroscopy as well as a theoretical approach using molecular dynamics simulations.

Fabrication method for a thin film semiconductor device, the thin film semiconductor device itself, liquid crystal display, and electronic device

Abstract: In order to fabricate a high performance thin film semiconductor device using a low temperature process in which it is possible to use low price glass substrates, a thin film semiconductor device has been fabricated by forming a silicon film at less than 450° C, and, after crystallization, keeping the maximum processing temperature at or below 350° C In applying the present invention to the fabrication of an active matrix liquid crystal display, it is possible to both easily and reliably fabricate a large, high-quality liquid crystal display Additionally, in applying the present invention to the fabrication of other electronic circuits as well, it is possible to both easily and reliably fabricate high-quality electronic circuits

Afm fabrication of sub-10-nanometer metal-oxide devices with in situ control of electrical properties

Abstract: Metal wires and metal-oxide-metal junctions were fabricated by anodic oxidation with the conducting tip of an atomic force microscope (AFM). The width of the wires and resistance of the junctions were controlled by real-time, in situ measurement of the device resistance during fabrication. Because the properties of nanometer-scale devices are very sensitive to size variations, such measurements provide a more accurate method of controlling device properties than by controlling geometry alone. In this way, structures with critical dimensions of less than 10 nanometers were fabricated with precisely tailored electrical properties.

Micromechanical membrane switches for microwave applications

Abstract: This paper proposes the fabrication of low-cost, low-loss microwave switches using thin metal membranes actuated by electrostatic fields. Measurement of switch test structures and modeling indicates that these devices have a potential 1000 to 2000-GHz figure-of-merit. Various aspects of fabrication, design, performance, and application of these devices are discussed. >

Enhancement of the dielectric constant of Ta 2 O 5 through substitution with TiO 2

Abstract: MICROELECTRONICS research is in large part driven by the demand for smaller components with enhanced performance. For capacitive components, which form the basis of many memory devices, the dielectric constant limits the degree of miniaturization—a limit that is now being approached for the materials currently in use. For this reason, exotic compounds with high dielectric constants, such as barium strontium titanate, are being widely investigated1. But such materials invariably incorporate chemical elements foreign to current microelectronics fabrication procedures, and must pass extensive compatibility tests before they can be used commercially. From a compatibility point of view, tantalum oxide, Ta2O5, is considered more promising2-5 (although its dielectric properties are more modest), and it is known to form high-quality thin films in conventional fabrication processes. Here we show that the dielectric constant of Ta2O5 can be increased by nearly a factor of four — from 35 to 126—through the addition of 8% titanium oxide, TiO2. The minimum area of capacitive components prepared from this material should be reduced by the same factor, and as both tantalum and titanium are compatible with fabrication processes currently in use, the material shows great promise for future microelectronics applications.

Fabrication of Photonic Band-Gap Crystals

Abstract: We describe the fabrication of three-dimensional photonic crystals using a reproducible and reliable procedure consisting of electron beam lithography followed by a sequence of dry etching steps. Careful fabrication has enabled us to define photonic crystals with 280 nm holes defined with 350 nm center to center spacings in GaAsP and GaAs epilayers. We construct these photonic crystals by transferring a submicron pattern of holes from 70-nm-thick polymethylmethacrylate resist layers into 300-nm-thick silicon dioxide ion etch masks, and then anisotropically angle etching the III-V semiconductor material using this mask. Here, we show the procedure used to generate photonic crystals with up to four lattice periods depth.

Fabrication of nanometer‐scale side‐gated silicon field effect transistors with an atomic force microscope

Abstract: The fabrication of nanometer‐scale side‐gated silicon field effect transistors using an atomic force microscope is reported. The probe tip was used to define nanometer‐scale source, gate, and drain patterns by the local anodic oxidation of a passivated silicon (100) surface. These thin oxide patterns were used as etch masks for selective etching of the silicon to form the finished devices. Devices with critical features as small as 30 nm have been fabricated with this technique.

Fabrication and performance of selectively oxidized vertical-cavity lasers

Abstract: We report the high yield fabrication and reproducible performance of selectively oxidized vertical-cavity surface emitting lasers. We show that linear oxidation rates of AlGaAs without an induction period allows reproducible fabrication of buried oxide current apertures within monolithic distributed Bragg reflectors. The oxide layers do not induce obvious crystalline defects, and continuous wave operation in excess of 650 h has been obtained. The high yield fabrication enables relatively high laser performance over a wide wavelength span. We observe submilliamp threshold currents over a wavelength range of up to 75 nm, and power conversion efficiencies at 1 mW output power of greater than 20% over a 50-nm wavelength range. >

Evolution of microstructure during fabrication of Zr-2.5 Wt pct Nb alloy pressure tubes

Abstract: Microstructural changes occurring during the fabrication of Zr-2.5 pct Nb alloy pressure tubes by a modified route, involving hot extrusion followed by two pilgering operations with an intermediate annealing step, have been examined in detail. In the conventional fabrication route, the hot extrusion step is followed by a single cold drawing operation in which the cold work to the extent of 25 pct is imparted to the material for achieving the required mechanical properties. Tensile properties obtained at each stage of fabrication have been evaluated and compared between the two processes. The main aim of this work has been to produce a microstructure and texture which are known to yield a lower irradiation growth. Additionally, suitable annealing conditions have been optimized for the intermediate annealing which annihilates the cold work introduced by the first cold pilgering operation without disturbing the two-phase elongated microstructure. This elongated α+ β I microstructure is required for obtaining the desired level of strength at 310 °C. The final microstructure and the crystallographic texture of the finished pressure tube have been compared with those reported for the conventionally processed material.

Theoretical investigation of fabrication‐related disorder on the properties of photonic crystals

Abstract: How various deviations in perfect photonic crystals, which may arise during fabrication, can affect the size of photonic band gaps is investigated theoretically. The emphasis is on determining the effects of misalignment of basic structural elements and overall surface roughness, because of their general fabrication relevance. As an example, calculations on a newly proposed three‐dimensional photonic crystal are performed. It is shown that the size of the gap is tolerant to significant amounts of deviation from the perfect structure.

Gray-scale masks for diffractive-optics fabrication: II. Spatially filtered halftone screens.

Abstract: Fabrication of diffractive optics with binary masks requires multiple photolithographic processes to produce efficient, continuous profile elements (kinoforms). Alignment or etching errors at any stage of fabrication decrease the efficiency of the element. We developed two accessible procedures that minimize fabrication complexity, component turnaround time, and cost. The first technique [Appl. Opt. 34, 7507-7517 (1995)] uses gray-scale masks produced by commercial slide-imager systems. Here, we report on an alternative technique for producing gray-scale masks by spatial filtering of halftone screens. Using the photoreduced gray-scale patterns as lithographic masks, we fabricated diffractiveoptic blazed gratings and lens arrays in both photoresist and quartz. First-order efficiencies as high as 70% are reported. Also, the strengths and limitations of this technique are compared with the previously reported slide-imager method as well as other fabrication methods.

Composite bump structure and methods of fabrication

Abstract: A composite bump structure and methods of forming the composite bump structure. The composite bump structure comprises a polymer body of relatively low Young's Modulus compared to metals covered by a conductive metal coating formed at the input/output pads of an integrated circuit element or substrate. The composite bump is formed using material deposition, lithography, and etching techniques. A layer of soldering metal can be formed on the composite bumps if this is desired for subsequent processing. A base metal pad covering the integrated circuit element input/output pad can be used to provide added flexibility in location of the composite bump. The composite bump can be formed directly on the input/output pad or on the base metal pad.

Scalable high dielectric constant capacitor

Abstract: A capacitor for high density DRAM applications comprises a high-e capacitor dielectric such as BST or PZT in an arrangement which obviates the need for barrier layers during fabrication. The fabrication process allows for electrode placement by simple sputter deposition and further provides for the possibility of capacitor spacing below that of conventional lithographic techniques.

Holographic optical element fabrication using chalcogenide layers

Abstract: Investigations in the field of diffractive optical element (DOE) fabrication using optical methods and registering media based on chalcogenide vitreous semiconductors are reviewed. The peculiarities of the holographic diffraction grating (HDG) fabrication processes using such resists are investigated and the factors that influence the groove profiles are determined. Ways of optimizing media parameters, exposure, and treatment processes are shown. High-quality HDGs are obtained with spatial frequencies in the range 600 to 3600 mm-1, diffraction efficiencies of 80 to 85% in polarized light, and a stray light level of 10-6. The processes of Fresnel lense formation by the holographic method with the consequent diffraction pattern transfer into the substrate are developed and investigated. This provides an opportunity to obtain binary lenses with high numerical apertures and small sizes. The results of investigations of the fabrication processes of DOEs with blazed profiles are discussed. Most promising is the method of direct DOE recording using a sharply focused laser beam, which enables one to obtain kinoform elements with m icrometer-sized distant zones. Additional treatment methods (wet or dry) enable one to obtain blazed gratings using the initial HDG with a symmetrical profile fabricated on the base of the chalcogenide layers.

Glass-fiber lasers in the ultraviolet and visible

Abstract: The recent fabrication of rare earth-doped fluoro-zirconate (ZBLAN) glass fiber has spurred the development of a family of visible and ultraviolet fiber lasers pumped by upconversion. The performance of CW room temperature devices demonstrated to date is reviewed with emphasis on the recently reported Nd-doped ZBLAN fiber laser operating in the ultraviolet at 381 nm. >

Design, Fabrication, And Testing Of A C-shape Actuator

Abstract: SUMMARY This paper describes the design, fabrication, and testing of a microactuator, whose bimorph beams curl up to form a C-shape and reach hundreds of microns from the substrate. The multi-layer C-shape beams were designed by FEM nonlinear analysis and fabricated on a silicon wafer by surface micromachining involving polyimide and metal thin films. The large curvature (i.e., small radius of curvature) is achieved by utilizing the large residual stress difference between thin films. The device is normally curled up, and it opens up by either electrostatic or thermal actuation. The device was operated successfully in liquid as well as in air to their full range between complete curl up and flat positions, demonstrating tip displacements of over two hundred microns.

Fabrication of diffractive optical elements using a single optical exposure with a gray level mask

Abstract: A method for mass fabrication of environmentally rugged monolithic diffractive optical elements (DOEs) is demonstrated. A one‐step optical exposure, with a gray level mask, was used to produce analog resist profiles that were transferred into their substrates using chemically assisted ion beam etching in a single etching step. The described procedure allows mass fabrication of DOEs without the tedious multiple exposure and etching steps commonly used in multilevel DOE fabrication. To generate a multilevel DOE in an optical substrate, only a single exposure using a gray level mask and a single etching step are necessary. The fabrication method presented will reduce processing time and increase manufacturability, which will result in a general cost reduction per element.

Free standing single-crystal silicon microstructures

Abstract: Micromachined structures of single-crystal silicon have been fabricated with a view to developing them for a number of potential uses. The structures which are fabricated in (111) orientation silicon are undoped thus permitting the incorporation of active circuit elements in the structures themselves. Moreover no high temperatures, applied voltages or long etch times are used in the fabrication sequence, thereby simplifying the task of integration with circuit processes. The potential uses of these structures include photodiodes with high speed and efficiency, accelerometers, or structures for stress or thermal isolation.

The black silicon method. IV. The fabrication of three-dimensional structures in silicon with high apect ratios for scanning probe microscopy and other applications

Abstract: The recently developed black silicon method (BSM) is presented as a powerful tool in finding recipes for the fabrication of MEMS building blocks such as Ay-stages. scanning probe tips, inkjet filters, multi-electrodes for neuro-electronic interfaces, and mouldings Lor direct patterning into polymers. The fabrication of these blocks in silicon with high aspect ratios and smooth surface textures will be described and discussed by using the BSM and standard reactive ion etching (ME).

A coronary endoprosthesis and a method for its fabrication

Abstract: A stent for implantation in a coronary artery (1) is assembled from discrete modules (2) fashioned in a biocompatible material, each composed of two "C" shaped members joined at the ends by respective rectilinear and mutually parallel members (3a, 3b); the individual modules are linked together by a single helicoid element (4), likewise fashioned in a biocompatible material, which is coiled around the rectilinear members (3a, 3b) in such a way as to effect a closure of the modules, disposed one alongside another, in a direction parallel with their longitudinal axis (X). The modules (2) and the helicoid element (4) are plastically deformable both in the radial and in the axial dimension, so that the surgeon can vary the axial distribution of the modules internally of the blood vessel (1) and modify the ultimate configuration of the helicoid element (4).

Fabrication of vapor-deposited micro heat pipe arrays as an integral part of semiconductor devices

Abstract: Vapor-deposited micro heat pipe arrays (VDMHP) were fabricated as an integral part of semiconductor devices to act as efficient heat spreaders by reducing the thermal path between the heat sources and heat sink. Fabrication of the VDMHP was accomplished by first establishing a series of grooves in a silicon wafer. Orientation dependent etching (ODE) using a KOH-1-propanol-H/sub 2/O solution on a (100) wafer with a (111) flat covered with an oxide mask, resulted in grooves 25 /spl mu/m wide and 25 /spl mu/m deep with sharp, perpendicular edges. The wafers were predeposited with a layer of chromium followed by a layer of gold to improve the adhesion characteristics. Dual electron beam vapor deposition, followed by planetary process using molybdenum crucibles, were used to deposit copper 31.5-33.0 /spl mu/m thick, and provide complete closure of the grooves. A glass cover slip was bonded on the top of the deposited layer. The grooves were finally charged and sealed. A computer model Simulation and Modeling of Evaporated Deposition Profiles (SAMPLE) was used to optimize the metal step coverage and successfully predict the cross-sectional profile of the VDMHP. >

Oxychloride glasses based on the TeO2-ZnO-ZnCl2 system

Abstract: A series of glasses based on the TeO2-ZnO-ZnCl2 system was prepared and their physical, thermal and optical propeties were investigated. This system provides a wide and stable glass formation range in which a Tc-Tg gap beyond 140°C can be achieved. An infrared cut-off edge up to 6.5 μm can be obtained, while the optical energy gap was found to be in the range of 2.0–2.5 eV. Most properties are observed to be dependent in a systematic manner on the ZnCl2 content.

DEEMO: a new technology for the fabrication of microstructures

Abstract: The recent innovations in dry etching make it a promising technology for the fabrications of micromoulds. The high aspect ratios, directional freedom, low roughness, high etch rates and high selectivity with respect to the mask material allow a versatile fabrication process of micromoulds for subsequent electroplating and embossing, as is demonstrated with the DEEMO process. DEEMO is an English acronym and stands for Dry Etching, Electroplating and Moulding.

Fabrication of column‐based silicon field emitter arrays for enhanced performance and yield

Abstract: In this article, simulation, fabrication, and direct current (dc) characterization data are presented for column‐based silicon field emitter array (FEA) devices, made using anisotropic or isotropic etching of silicon to form emitter tips In the design of the fabrication process, we have attempted to minimize spatial nonuniformity of process parameters affecting the geometry of the device structure, and, where possible, counteract the nonuniformity through a proper choice of processing variables FEA devices, with as many as 232 630 tips, on 4–10 μm centers, have been successfully fabricated The highest electron emission current measured was over 18 mA at the gate voltage of 150 V for a 6648 tip array

Head mounted color display system

Abstract: A head mounted display device includes a high resolution active matrix display which reduces center of gravity offset in a compact design. The display panel may be formed using a single crystal thin-film material that is transferred to substrates for display fabrication. Pixel arrays form light valves or switches that can be fabricated with control electronics in the thin-film material prior to transfer. The resulting circuit panel is then incorporated into a color display panel with a light emitting or liquid crystal material to provide the desired light valve.

Fused Deposition of Ceramics: A New Technique for the Rapid Fabrication of Ceramic Components

Abstract: (1995). Fused Deposition of Ceramics: A New Technique for the Rapid Fabrication of Ceramic Components. Materials Technology: Vol. 10, No. 7-8, pp. 144-146.