Showing papers on "Substrate (electronics) published in 2005"

Methods of making thin film transistors comprising zinc-oxide-based semiconductor materials and transistors made thereby

Abstract: A thin film transistor comprises a zinc-oxide-containing semiconductor material. Such transistors can further comprise spaced apart first and second contact means or electrodes in contact with said material. Further disclosed is a process for fabricating a thin film transistor device, wherein the substrate temperature is no more than 300° C. during fabrication.

Methods of making displays

Abstract: Methods of forming displays are described. The displays have zinc oxide row and column drivers integrated onto the same display substrate as zinc oxide pixel transistors and organic light emitting diodes. The organic light emitting diodes are prepared, at least in part, using a thermal transfer process from a donor sheet.

Enhancement of field-effect mobility due to surface-mediated molecular ordering in regioregular polythiophene thin film transistors

Abstract: With the aim of enhancing the field-effect mobility by promoting surface-mediated two-dimensional molecular ordering in self-aligned regioregular poly(3-hexylthiophene) (P3HT) we have controlled the intermolecular interaction at the interface between P3HT and the insulator substrate by using self-assembled monolayers (SAMs) functionalized with various groups (–NH2, –OH, and –CH3). We have found that, depending on the properties of the substrate surface, the P3HT nanocrystals adopt two different orientations—parallel and perpendicular to the insulator substrate—which have field-effect mobilities that differ by more than a factor of 4, and that are as high as 0.28 cm2 V–1 s–1. This surprising increase in field-effect mobility arises in particular for the perpendicular orientation of the nanocrystals with respect to the insulator substrate. Further, the perpendicular orientation of P3HT nanocrystals can be explained by the following factors: the unshared electron pairs of the SAM end groups, the π–H interactions between the thienyl-backbone bearing π-systems and the H (hydrogen) atoms of the SAM end groups, and interdigitation between the alkyl chains of P3HT and the alkyl chains of the SAMs.

Controlled growth of well-aligned ZnO nanorod array using a novel solution method.

Abstract: A simple method of synthesizing nanomaterials and the ability to control the size and position of them are crucial for fabricating nanodevices. In this work, we developed a novel ammonia aqueous solution method for growing well-aligned ZnO nanorod arrays on a silicon substrate. For ZnO nanorod growth, a thin zinc metal seed layer was deposited on a silicon substrate by thermal evaporation. Uniform ZnO nanorods were grown on the zinc-coated silicon substrate in aqueous solution containing zinc nitrate and ammonia water. The growth temperature was as low as 60−90 °C and a 4-in. wafer size scale up was possible. The morphology of a zinc metal seed layer, pH, growth temperature, and concentration of zinc salt in aqueous solution were important parameters to determine growth characteristics such as average diameters and lengths of ZnO nanorods. We could demonstrate the discrete controlled growth of ZnO nanorods using sequential, tailored growth steps. By combining our novel solution method and general photolit...

The use of functionally graded poly-SiGe layers for MEMS applications

Abstract: It is difficult to meet all the different material and economical requirements posed to a MEMS structural layer that can be integrated with the electronics on the same substrate using a single layer process. Therefore a multilayer process, which uses a combination of a CVD crystallization layer and a high-growth rate PECVD bulk layer was developed. High-quality films with excellent electrical and mechanical properties can be obtained at low temperature (#450°C) and high deposition rates (~100 nm/min). Fine-tuning of the stress gradient is accomplished by the use of a top stress compensation layer, whose optimal thickness was estimated from an evaluation of the stress gradient profile over thickness. These layers have been used for processing a 10 µm thick poly-SiGe gyroscope on top of a standard 0.35 µm CMOS process.

Thickness Dependence of Mobility in Pentacene Thin‐Film Transistors

Abstract: The dependence of the field-effect mobility of organic thin-film transistors (OTFT) was measured using top-contact devices. OTFTs were fabricated by vacuum sublimation of pentacene on thermally oxidized silicon wafers to form films with nominal thickness between 2 and 25 monolayers. The deposition was carried out at a low rate and the substrate was heated in order to yield high-quality films. The results indicate that the mobility saturates when 6 monolayers of pentacene are deposited on the gate dielectric, SiO2.

Display device and driving method thereof

Abstract: A liquid crystal display is suitable for displaying images with rapid motions, and comprises an active matrix substrate equipped with a plurality of thin film transistors. The active matrix substrate comprises a plurality of pixels that are placed at the encircled areas of a plurality of scanning lines and a plurality of data lines. Each pixel consists of two thin film transistors and one pixel electrode. The data lines connected electrodes of the thin film transistors are connected to two adjoining data lines respectively, whereas the pixel connected electrodes of the two thin film transistors are together connected to the pixel electrode. The gate electrodes of the two thin film transistors are connected to two adjoining scanning lines respectively.

Fundamental boron-oxygen-related carrier lifetime limit in mono- and multicrystalline silicon

Abstract: Boron-doped crystalline silicon is the most relevant material in today's solar cell production. Following the trend towards higher efficiencies, silicon substrate materials with high carrier lifetimes are becoming more and more important. In silicon with sufficiently low metal impurity concentrations, the carrier lifetime is ultimately limited by a metastable boron–oxygen-related defect, which forms under minority-carrier injection. We have analysed 49 different Czochralski-grown silicon materials of numerous suppliers with various boron and oxygen concentrations. On the basis of our measured lifetime data, we have derived a universal empirical parameterisation predicting the stable carrier lifetime from the boron and oxygen content in the crystalline silicon material. For multicrystalline silicon it is shown that the predicted carrier lifetime can be regarded as a fundamental upper limit. Copyright © 2005 John Wiley & Sons, Ltd.

High-mobility Carbon-nanotube Thin-film Transistors on a Polymeric Substrate

Abstract: We report the development of high-mobility carbon-nanotube thin-film transistors fabricated on a polymeric substrate. The active semiconducting channel in the devices is composed of a random two-dimensional network of single-walled carbon nanotubes (SWNTs). The devices exhibit a field-effect mobility of 150cm2∕Vs and a normalized transconductance of 0.5mS∕mm. The ratio of on-current (Ion) to off-current (Ioff) is ∼100 and is limited by metallic SWNTs in the network. With electronic purification of the SWNTs and improved gate capacitance we project that the transconductance can be increased to ∼10–100mS∕mm with a significantly higher value of Ion∕Ioff, thus approaching crystalline semiconductor-like performance on polymeric substrates.

Catalyst-free growth of GaAs nanowires by selective-area metalorganic vapor-phase epitaxy

Abstract: We report on the fabrication of GaAs hexagonal nanowires surrounded by {110} vertical facets on a GaAs (111) B substrate using selective-area (SA) metalorganic vapor-phase epitaxial (MOVPE) growth. The substrate for SA growth was partially covered with thin SiO2, and a circular mask opening with a diameter d0 of 50–200 nm was defined. After SA-MOVPE, GaAs nanowires with a typical diameter d ranging from 50 to 200 nm and a height from 2 to 9μm were formed vertically on the substrate without any catalysts. The size of the nanowire depends on the growth conditions and the opening size of the masked substrate. A possible growth mechanism is also discussed.

Investigations on the propagation characteristics of the substrate integrated waveguide based on the method of lines

Abstract: A rigorous full-wave approach based on the method of lines (MoL) is presented to analyse the propagation characteristics of substrate integrated waveguides (SIWs), in which a generalised matrix eigenvalue equation is derived instead of the conventional transcend equation, greatly improving the computing efficiency. The use of an efficient Z-transform absorbing boundary condition (Z-ABC) further improved the accuracy of the calculated propagation constants. Finally, two empirical equations are proposed for the propagation constants of SIWs, which gives a simple but efficient tool in designing substrate integrated waveguide components.

Room-temperature semiconductor gas sensor based on nonstoichiometric tungsten oxide nanorod film

Abstract: Porous tungsten oxide films were deposited onto a sensor substrate with a Si bulk-micromachined hotplate, by drop-coating isopropyl alcohol solution of highly crystalline tungsten oxide (WO2.72) nanorods with average 75nm length and 4nm diameter. The temperature-dependent gas sensing characteristics of the films have been investigated over the mild temperature range from 20to250°C. While the sensing responses for ammonia vapor showed increase in electrical conductivity at temperatures above 150°C as expected for n-type metal oxide sensors, they exhibited the opposite behavior of unusual conductivity decrease below 100°C. Superb sensing ability of the sensors at room temperature in conjunction with their anomalous conductivity behavior might be attributed to unique nanostructural features of very thin, nonstoichiometric WO2.72.

Characterization of sputtered NiO thin films

Abstract: Nickel oxide (NiO) thin films were deposited by RF magnetron sputtering process at different RF powers and substrate temperatures in a pure oxygen atmosphere. The structural, optical and electrical properties of NiO films were investigated using X-ray diffraction (XRD), visible spectrum and Hall effect measurements. The dependences of film properties on substrate temperature, crystalline structure and natural aging effect were studied. The results show that the resistivity increases as sputtering power increases from 100 to 200 W at constant temperature. The lowest resistivity and Hall coefficient obtained are 16.7 V cm and 1.99 cm 3 /C, respectively, as the sputtering power is 100 Wand substrate temperature is 3508. The highest carrier concentration obtained is 3.1310 18 cm 3 as the sputtering power is 100 Wand substrate temperature is 3508. The crystal structure was analyzed by X-ray diffraction method. The preferred orientation of NiO film changes from (111) to (200) when the substrate temperature varies from unheated condition to 3508. Electrical properties of NiO films were unstable and show a natural aging effect. Resistivity of NiO films increases as the time of natural aging increases. Under the substrate-unheated condition, the transmittance of as-deposited samples is lower compared to the film prepared at substrate temperature of 350 8C. The change in transmittance may be due to the microstructural change in the material. It is suggested that the sputtering power affects the preferred orientation of NiO film. Higher substrate temperature induces larger grain size and more perfect crystalline structure, which lead to low resistivity of NiO film. D 2004 Published by Elsevier B.V.

Pulsed-laser-induced nanoscale island formation in thin metal-on-oxide films

Abstract: he mechanisms controlling the nanostructuring of thin metal-on-oxide films by nanosecond pulsed excimer lasers are investigated. When permitted by the interfacial energetics, the breakup of the metal film into nanoscale islands is observed. A range of metals (Au, Ag, Mo, Ni, Ti, and Zn) with differing physical and thermodynamic properties, and differing tendencies for oxide formation, are investigated. The nature of the interfacial metal-substrate interaction, the thermal conductivity of the substrate, and the initial thickness of the metal film are all shown to be of importance when discussing the mechanism for nanoscale island formation under high fluence irradiation. It is postulated that the resulting nanoparticle size distribution is influenced by the surface roughness of the initial film and the Rayleigh instability criterion. The results obtained are compared with simulations of the heat transfer through the film in order to further elucidate the mechanisms. The results are expected to be applicable to the laser induced melting of a large range of different materials, where poor wetting of substrate by the liquid phase is observed.

Plasma enhanced atomic layer deposition system having reduced contamination

Abstract: A plasma enhanced atomic layer deposition (PEALD) system is described, wherein the system comprises a processing space and a high vacuum, ultra-clean transfer space. During processing, the substrate to which the thin conformal film is formed is exposed to the processing space. During substrate transfer, the substrate is exposed to the high vacuum space. Processing gases are introduced sequentially and alternately to the process chamber and the pressures and gas flows within, to and from, and between the process chamber and the high vacuum transfer space are controlled to keep the transfer space ultra-clean.

Selective Functionalization of In2O3 Nanowire Mat Devices for Biosensing Applications

Abstract: A strategy to covalently attach biological molecules to the electrochemically active surface of indium oxide nanowire (In2O3 NW) mat devices is presented. A self-assembled monolayer (SAM) of 4-(1,4-dihydroxybenzene)butyl phosphonic acid (HQ-PA) was generated on an indium tin oxide (ITO)-coated glass and In2O3 NWs surface. The chemical steps required for surface derivatization were optimized on an ITO surface prior to modifying the In2O3 NWs. The hydroquinone group contained in the HQ-PA SAM was electrochemically oxidized to quinone (Q-PA) at +330 mV. The monolayer of Q-PA was allowed to react with a thiol-terminated DNA. The DNA was paired to its complementary strand tagged with a fluorescence dye. Attachment of DNA was verified using fluorescence microscopy. A device was subsequently prepared on a SiO2-supported mat of In2O3 NWs by depositing gold electrodes on the mat surface. The reaction strategy optimized on ITO was applied to this In2O3 NW-based device. Arrays of In2O3 NWs on a single substrate were...

Multi-gas distribution injector for chemical vapor deposition reactors

Abstract: A gas distribution injector [150] for chemical vapor deposition reactors [100] has precursor gas inlets [160, 165] disposed at spaced-apart locations on an inner surface [155] facing downstream toward a substrate [135], and has carrier openings [167] disposed between the precursor gas inlets [160, 165]. One or more precursor gases [180, 185] are introduced through the precursor gas inlets [160, 165], and a carrier gas [187] substantially nonreactive with the precursor gases is introduced through the carrier gas openings [167]. The carrier gas minimizes deposit formation on the injector [150]. The carrier gas openings may be provided by a porous plate [230] defining the surface or via carrier inlets [167] interspersed between precursor inlets. The gas inlets may removable [1780] or coaxial [1360].

Self-assembled monolayer-enhanced hydrogen sensing with ultrathin palladium films

Abstract: Resistive-type palladium structures for hydrogen sensing remains as a research focus for their simplicity in device construction. We demonstrate that a siloxane self-assembled monolayer placed between a substrate and an evaporated ultrathin Pd film promotes the formation of small Pd nanoclusters and reduces the stiction between the palladium and the substrate. The resulting Pd nanocluster film can detect 2%H2 with a rapid response time of ∼70ms and is sensitive to 25 ppm hydrogen, detectable by a 2% increase in conductance due to the hydrogen-induced palladium lattice expansion.

Rewriteable memory cell comprising a diode and a resistance-switching material

Abstract: In a novel rewriteable nonvolatile memory cell formed above a substrate, a diode is paired with a reversible resistance-switching material, preferably a metal oxide or nitride such as, for example, NiO, Nb 2 O 5 , TiO 2 , HfO 2 , Al 2 O 3 , MgO x , CrO 2 , VO, BN, and AlN. In preferred embodiments, the diode is formed as a vertical pillar disposed between conductors. Multiple memory levels can be stacked to form a monolithic three dimensional memory array. In some embodiments, the diode comprises germanium or a germanium alloy, which can be deposited and crystallized at relatively low temperatures, allowing use of aluminum or copper in the conductors.

First-principles calculation of the electronic structure and EELS spectra at the graphene/Ni(111) interface

Abstract: A spin-polarized first-principles calculation of the atomic and electronic structure of the graphene/Ni(111) interface is presented. Different structural models have been considered, which differ in the positions of the carbon atoms with respect to the nickel topmost layer. The most probable structure, which has the lowest energy, has been determined. The distance between the floating carbon layer and the nickel surface is found smaller than the distance between graphene sheets in bulk graphite, in accordance with experimental measurements. The electronic structure of the graphene layer is strongly modified by interaction with the substrate and the magnetic moment of the surface nickel atoms is lowered in the presence of the graphene layer. Several interface states have been identified in different parts of the interface two-dimensional Brillouin zone. Their influence on the electron energy loss spectra has been evaluated.

Removable amorphous carbon CMP stop

Abstract: A method is provided for processing a substrate including removing amorphous carbon material disposed on a low k dielectric material with minimal or reduced defect formation and minimal dielectric constant change of the low k dielectric material. In one aspect, the invention provides a method for processing a substrate including depositing at least one dielectric layer on a substrate surface, wherein the dielectric layer comprises silicon, oxygen, and carbon and has a dielectric constant of about 3 or less, forming amorphous carbon material on the at least one dielectric layer, and removing the one or more amorphous carbon layers by exposing the one or more amorphous carbon layers to a plasma of a hydrogen-containing gas.

Semiconductor device and fabrication method thereof

Abstract: A semiconductor device includes a gate electrode formed on a silicon substrate via a gate insulation film in correspondence to a channel region, source and drain regions of a p-type diffusion region formed in the silicon substrate at respective outer sides of sidewall insulation films of the gate electrode, and a pair of SiGe mixed crystal regions formed in the silicon substrate at respective outer sides of the sidewall insulation films in epitaxial relationship to the silicon substrate, the SiGe mixed crystal regions being defined by respective sidewall surfaces facing with each other, wherein, in each of the SiGe mixed crystal regions, the sidewall surface is defined by a plurality of facets forming respective, mutually different angles with respect to a principal surface of the silicon substrate.

Compact super-wide bandpass substrate integrated waveguide (SIW) filters

Abstract: It is known that the substrate integrated waveguide (SIW) features high-pass characteristics of the conventional waveguide, and a periodic structure (PS) generally presents bandstop characteristics. Therefore, a super-wide-band bandpass characteristic should be realized by combining some sort of PS into the SIW. In this paper, three types of compact SIW-PS wide-band bandpass filters are proposed and investigated with simulation and experiment. Performances of a super-wide bandpass, for instance, 8.5-16.5 GHz in this case study, with low insertion loss and sharp out-of-band characteristics are observed from both simulated and measured results.

p-Channel organic semiconductors based on hybrid acene-thiophene molecules for thin-film transistor applications.

Abstract: We report the structural and electrical characterization of two new p-channel organic semiconductors, 5,5‘-bis(2-tetracenyl)-2,2‘-bithiophene (1) and 5,5‘-bis(2-anthracenyl)-2,2‘-bithiophene (2). Both compounds exhibited a high degree of thermal stability with decomposition temperatures of 530 °C and 425 °C for 1 and 2, respectively. The thin-film structures of 1 and 2 were examined using wide-angle X-ray diffraction (XRD), grazing incidence X-ray diffraction (GIXD), and atomic force microscopy (AFM). Films of 1 and 2 pack in similar triclinic unit cells with the long axes of the molecules nearly perpendicular to the substrate. Thin-film transistors (TFTs) based on 1 and 2 exhibit contact-corrected linear regime hole mobility as high as 0.5 cm2/Vs and 0.1 cm2/Vs, respectively. The specific contact resistance at high gate voltages for gold top contacts was 2 × 104 Ω cm and 3 × 104 Ω cm for 35 nm thick films of 1 and 2, respectively. Long-term air stability tests revealed less degradation of the electrical ...

Controlled shallow single ion implantation in silicon using an active substrate for sub-20 keV ions

Abstract: We demonstrate a method for the controlled implantation of single ions into a silicon substrate with energy of sub-20‐keV The method is based on the collection of electron-hole pairs generated in the substrate by the impact of a single ion We have used the method to implant single 14‐keV P31 ions through nanoscale masks into silicon as a route to the fabrication of devices based on single donors in silicon

HDP-CVD deposition process for filling high aspect ratio gaps

Abstract: A method for forming a silicon oxide layer over a substrate disposed in a high density plasma substrate processing chamber. The method includes flowing a process gas that includes a silicon-containing source, an oxygen-containing source and a fluorine-containing source into the substrate processing chamber and forming a plasma from said process gas. The substrate is heated to a temperature above 450° C. during deposition of said silicon oxide layer and the deposited layer has a fluorine content of less than 1.0 atomic percent.