Showing papers on "Fabrication published in 1988"

Technique for monolithic fabrication of microlens arrays

Abstract: A microlens fabrication process is described which can be used in applications requiring integration of optical elements (lenses) and microcircuits. The process is fully compatible with IC fabrication technology and uses commercially available IC processing materials. The obtained microlenses are of excellent quality and basically show diffraction-limited resolution with ~1-μm spot size. Extensions of the process to production of nonspherical lenses and use of alternative material packages are also discussed.

Ion-exchanged glass waveguides: a review

Abstract: Passive glass waveguides made by ion-exchange technique are potential candidates for integrated optics (IO) applications. The authors review the advantages in the technology as applied to fabrication of useful single-mode structures. Progress in process, fabrication, modeling, and waveguide performance using different monovalent cation systems and glass compositions is described with emphasis on fiber-compatible single-mode structures prepared from molten baths. It is shown how a systematic study allows a correlation between the process parameters and the waveguide characteristics so desirable in assuring reproducible characteristics of the devices. >

Thermally excited silicon microactuators

Abstract: A cantilever-type micromachined silicon actuator based on the bimetal effect used extensively for the fabrication of temperature-controlled electrical switches is described. The silicon actuator consists of a Si-metal sandwich layer and an integrated poly-Si heating resistor as a driving element. Due to the low heat capacity of the transducer element, a high temperature increase per input power unit can be achieved. For a (Si-Au)-cantilever-type actuator, 500- mu m long and several micrometers thick, a specific deflection of approximately 0.1 mu m/K at the free end has been measured. The design considerations, fabrication process, and experimental results of the actuator are discussed. >

Deep-submicrometer MOS device fabrication using a photoresist-ashing technique

Abstract: A photoresist-ashing process has been developed which, when used in conjunction with conventional g-line optical lithography, permits the controlled definition of deep-submicrometer features. The ultrafine lines were obtained by calibrated ashing of the lithographically defined features in oxygen plasma. The technique has been successfully used to fabricate MOSFETs with effective channel length as small as 0.15 mu m that show excellent characteristics. An NMOS ring oscillator with 0.2- mu m devices has been fabricated with a room-temperature propagation delay of 22 ps/stage. Studies indicate that the thinning is both reproducible and uniform so that it should be usable in circuit as well as device fabrication. Since most polymer-based resist materials are etchable with an oxygen plasma, the basic technique could be extended to supplement other lithographic processes, including e-beam and X-ray processes, for fabricating both silicon and nonsilicon devices and circuits. >

Fabrication techniques of lithium niobate waveguides

Abstract: In the paper, the most commonly used fabrication techniques of optical waveguides in lithium niobate are reviewed. Diffusion processes such as out-diffusion of lithium oxide from the crystal surface, in-diffusion of metals, ion exchange and proton exchange, and ion implantation are analysed. The characteristics of LiNbO3 optical waveguides prepared by the different technological procedures, are reported in relation with the fabrication conditions. High quality optical waveguides on lithium niobate can be produced by Ti in-diffusion in a dry O2 atmosphere at temperatures above 1000°C for long diffusion times (>10 h). However, despite the large amount of research done in this field, correlations between optical properties and structural characteristics have not yet been established.

Fabrication of polysilicon fets on alkaline earth alumino-silicate glasses

Abstract: A method of fabricating polycrystalline silicon thin film field effect transistors on low cost alkaline earth alumino-silicate glass substrates which can tolerate device processing temperatures of approximately 800° C.

Fabrication of high-silica glass article

Abstract: Incorporation of fluorine into a porous silica body, such as an unsintered body produced by a sol-gel method, by VAD or OVPO, reduces or eliminates bubble or pore formation upon re-heating of the glass formed by sintering of the porous material. Effective fluorine concentrations are between 0.01 and 5% by weight. The invention can be used advantageously in producing preforms and optical fiber.

High strength composite component and method of fabrication

Abstract: A composite component suitable for high temperature applications which includes a composite compact that is thermally stable at temperatures up to 1200° C., the composite compact including a thin layer of metal bonded directly to a polycrystalline table in a HP/HT press, and a metallic substrate joined to the thin layer of metal by a high strength braze joint. The method of fabrication includes the steps of: placing a high temperature braze filler metal on the upper surface of the substrate and in contact with the thin layer of metal; applying heat through the table to melt the filler metal and accomplish the high strength joint between the substrate and the thin layer of metal; and cooling the substrate by conducting heat from all but the upper surface thereof.

Material for use in fabrication

Abstract: Material for use in fabrication having reference markings spaced uniformly such that the markings can be used for measurement.

Coil design and fabrication: basic design and modifications

Abstract: Basic design considerations The inductor is similar to a transformer primary, and the workpiece is equivalent to the transformer secondary (Fig. 1). Therefore, several of the characteristics of transformers are useful in the development of guidelines for coil design. One of the most important features of transformers is the fact that the efficiency of coupling between the windings is inversely proportional to the square of the distance between them. In addition, the current in the primary of the transformer, multiplied by the number of primary turns, is equal to the current in the secondary, multiplied by the number of secondary turns. Because of these relationships, there are several conditions that should be kept in mind when designing any coil for induction heating: 1) The coil should be coupled to the part as closely as feasible for maximum energy transfer. It is desirable that the largest possible number of magnetic flux lines intersect the workpiece at the area to be heated. The denser the flux at this point, the higher will be the current generated in the part. 2) The greatest number of flux lines in a solenoid coil are toward the center of the coil. The flux lines are concentrated inside the coil, providing the maximum heating rate there. 3) Because the flux is most concentrated close to the coil turns themselves and decreases farther from them, the geometric center of the coil is a weak flux path. Thus, if a part were to be placed off center in a coil, the area closer to the coil turns would intersect a greater number of flux lines and would therefore be heated at a higher rate, whereas the area of the part with less coupling would be heated at a lower rate; the resulting pattern is shown schematically in Fig. 2. This effect is more pronounced in high-frequency induction heating. 4) At the point where the leads and coil join, the magnetic field is weaker; therefore, the magnetic center of the inductor is not necessarily the geometric center. This effect is most apparent in single-turn coils. As the number of coil turns increases and the flux from each turn is added to that from the previous turns, this condition becomes less important. Due to the impracticability of always centering the part in the work coil, the part should be offset slightly toward this area. In addition, the part should be rotated, if practical, to provide uniform exposure.

Model for waveguide fabrication in glass by two-step ion exchange with ionic masking.

Abstract: A theory for optical waveguide fabrication processes, in which potassium ions exchanged into glass are used as a mask to regulate a subsequent silver-ion exchange, is presented. The model is used to examine the use of this technique in restricting the width of narrow-channel waveguides. The diffusion of silver through the potassium-ion mask is calculated, and a novel method of fabricating buried waveguides is described.

Fabrication of quantum wires in GaAs/AlGaAs heterolayers

Abstract: Conducting wires of widths down to 0.1 μm have been fabricated in modulation‐doped GaAs/AlGaAs material using SiCl4 reactive ion etching with a negative resist mask. The resist used was high‐resolution negative (HNR) and its applicability to microstructure fabrication is discussed. A novel dry etch for GaAs, CH4/H2 reactive ion etching, produces low damage and shows much promise for wire fabrication.

High electron mobility power transistor

Abstract: A high electron mobility transistor (HEMT) structure, and a corresponding method for its fabrication, in which the maximum power output is increased by a factor of approximately two. The structure includes a stop etch layer, which is of aluminum arsenide in the disclosed embodiment, and which functions both to facilitate selective etching during fabrication and, because of its relatively wide band-gap, as a current confinement layer during operation. Since the current confinement action has a detrimental effect in the region of the source contact of the device, by tending to raise the source resistance and the threshold voltage at which current saturation occurs, this effect is avoided by aligning the source region with an edge of the gate electrode during fabrication, to minimize the source resistance and the threshold voltage for maximum current saturation.

Fabrication of metal/high-temperature superconductor composites by shock compression

Abstract: By combining techniques of explosive welding and cladding and shock wave compaction and consolidation of powders, a fabrication technology has been developed for consolidating, bonding, and encapsulating reactive and temperamental copper oxide-based high-Tc superconducting powders in a supporting metal matrix. These ceramic superconductor/metal matrix composites have unique features as precursors to a range of superconductor devices and applications. The fabrication strategy utilizes a concept of prototype manufacturing where processed superconductors are characterized and tested to optimize the process variables and reliable behavior. This strategy, may lead to early commercialization and applications for the new high-Tc oxide superconductors.

Fabrication and performance of low loss optical components made by ion exchange in glass

Abstract: Passive optical components made by photolithography with ion exchange in glass have been developed. The technology used to fabricate these components is described, and their performance characterization is discussed. It is shown that this technique produces highly uniform low-loss devices. >

Fabrication of submicrometer freestanding single‐crystal gallium arsenide and silicon structures for quantum transport studies

Abstract: Freestanding wires of submicrometer width and with lengths up to 40 μm have been fabricated from single‐crystal GaAs and Si for studies of quantum transport. Fabrication techniques are described, and the low‐temperature properties for semiconductors and metals such as AuPd are compared. Fabrication of three‐terminal freestanding GaAs metal–semiconductor field effect transistor structures is demonstrated.

Materials and processes for microstructure fabrication

Abstract: The fabrication of structures considerably smaller than the devices and circuits that are mass-produced for use in computers and other electronic equipment is the subject of this paper. Devices of <1 µm (microstructures) and <100 nm (nanostructures) minimum dimensions were made possible in a practical sense only after the introduction of electron beams and the associated processes, as lithographic tools in the early 1960s. This paper presents a historical perspective of this very important chapter in lithographic technology, primarily from the point of view of materials and processes, since electron-beam systems are covered in other papers in this issue. In addition, the important criteria that have to be considered in the fabrication of small structures, with respect to the interaction of the writing beam with the resist material and the substrate, and the subsequent pattern-transferring processes, are discussed.

Fabrication and properties of high‐Tc superconducting wires

Abstract: The discovery of high‐temperature superconductivity in perovskite‐related oxides has generated an enormous amount of research activity and development effort toward applications. Commercially useful bulk superconductors typically require stabilization using a normal metal cladding for reasons of electrical, thermal, and mechanical protection, and in general need to be fabricated into fine fibers and wound into a solenoid configuration. The YBa2Cu3O7−δ type compound is a ceramic material which is mechanically hard and brittle, and is difficult to fabricate into fine wires. However, this difficulty has been overcome by several fabrication methods such as powder‐in‐tube method (metal‐clad composite), powder‐coating method (metal‐core composite), and molten oxide processing method. The effect of various processing steps on the structure and superconducting properties such as transition temperature and critical current density will be discussed. Some experiments to raise the high field critical current through...

Fabrication and optical spectroscopy of ultra small III–V compound semiconductor structures

Abstract: The paper discusses the fundamental technological processes for the fabrication of one- and zero-dimensional III–V compound semiconductor structures which are developed for optical spectroscopy. Using high-resolution electron beam lithography, two different approaches to the fabrication of quantum wires and dots have been taken: By electron beam lithography and dry etching of quantum well layers lateral confinement of the electron hole pairs can be obtained. Optical investigations of excitonic transitions in these structures, however, show that the properties are largely determined by surface effects. By the combination of implantation induced interdiffusion of quantum wells with high resolution electron-beam lithography on the other hand we define buried quantum wires and dots. Optical spectra from these structures show pronounced energetic shifts which can be traced to changes of the quantum well composition and to lateral quantization.

Non-linear control element for a flat electrooptical display screen and a method of fabrication of said control element

Abstract: A method of fabrication of non-linear control elements as applicable to electrooptical displays and in particular to large-area liquid-crystal displays of the flat-panel type, in which the following layers are stacked successively on a substrate: a first layer of metallic material, a first layer of undoped amorphous semiconductor material, a layer of doped amorphous semiconductor material, a second layer of undoped amorphous semiconductor material, and a second layer of metallic material.

Fabrication and performance of GaAs MESFETs with graded channel doping using focused ion-beam implantation

Abstract: The dopant concentration in the channel region of GaAs MESFETs is tailored by focused ion-beam implantation, allowing the fabrication of devices with higher power ratings than uniformly doped devices of similar dimensions With this technique, multiple masking steps during fabrication and avoided, and dopant concentration can be changed with great precision in both position and magnitude The effect of dopant grading on other device parameters, such as the transconductance and the pinch-off voltage, is reported >

Superconducting and normal state properties of niobium-nitride thin films

Abstract: Niobium nitride (NbN) is one of the leading materials for superconducting thin film applications such as electronic devices and coated r.f. cavities for high energy physics. In the following the fabrication technique of superconducting magnetron-sputtered NbN films is described and the experimental results are discussed.

Fabrication of diode arrays for photovoltaic characterization of silicon substrates

Abstract: A simple process sequence for the fabrication of passivated mesa diode arrays for photovoltaic characterization of single/polycrystalline silicon substrates is described. These diodes are used to measure a variety of substrate and cell parameters including resistivity, minority‐carrier diffusion length, Voc, Jsc, fill factor, and current‐voltage characteristics for analysis of the electronic transport properties. Evaluation techniques which use these diodes for determining spatial variations in the material/device charateristics are described. These devices are also suitable for characterizing various cell fabrication processes and for analysis of crystal defects on the solar cell characteristics.