Showing papers on "Contact resistance published in 2008"

Semiconductor device and method for manufacturing the same, and electric device

Abstract: It is an object of the present invention to simplify steps needed to process a wiring in forming a multilayer wiring. In addition, when a droplet discharging technique or a nanoimprint technique is used to form a wiring in a contact hole having a comparatively long diameter, the wiring in accordance with the shape of the contact hole is formed, and the wiring portion of the contact hole is likely to have a depression compared with other portions. A penetrating opening is formed by irradiating a light-transmitting insulating film with laser light having high intensity and a pulse high in repetition frequency. A plurality of openings having a minute contact area is provided instead of forming one penetrating opening having a large contact area to have an even thickness of a wiring by reducing a partial depression and also to ensure contact resistance.

Nonaqueous electrolyte secondary battery

Abstract: PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte liquid secondary battery superior in charge and discharge cycle characteristics and low-temperature characteristics in which adhesion strength is increased without increasing the contact resistance between an active material layer and a current collector and, even when charge and discharge are repeated, separation of the active material layer from the current collector is suppressed. SOLUTION: In the nonaqueous electrolyte liquid secondary battery, the surface of a binder layer formed beforehand on the positive electrode current collector 1 is roughening treated, and the surface of the current collector is partially exposed. and then the binder layer 3 is kept on a part of the positive electrode current collector 1. COPYRIGHT: (C)2010,JPO&INPIT

Thermal Properties of Metal-Coated Vertically Aligned Single-Wall Nanotube Arrays

Abstract: Owing to their high thermal conductivities, carbon nanotubes (CNTs) are promising for use in advanced thermal interface materials. While there has been much previous research on the properties of isolated CNTs, there are few thermal data for aligned films of single wall nanotubes. Furthermore, such data for nanotube films do not separate volume from interface thermal resistances. This paper uses a thermoreflectance technique to measure the volumetric heat capacity and thermal interface resistance and to place a lower bound on the internal volume resistance of a vertically aligned single wall CNT array capped with an aluminum film and palladium adhesion layer. The total thermal resistance of the structure, including volume and interface contributions, is 12 m 2 K MW -1 . The data show that the top and bottom interfaces of the CNT array strongly reduce its effective vertical thermal conductivity. A low measured value for the effective volumetric heat capacity of the CNT array shows that only a small volume fraction of the CNTs participate in thermal transport by bridging the two interfaces. A thermal model of transport in the array exploits the volumetric heat capacity to extract an individual CNT-metal contact resistance of 10 m 2 K 1 GW -1 (based on the annular area A a =πdb), which is equivalent to the volume resistance of 14 nm of thermal SiO 2 . This work strongly indicates that increasing the fraction of CNT-metal contacts can reduce the total thermal resistance below 1 m 2 K MW -1 .

Gallium–Indium–Zinc-Oxide-Based Thin-Film Transistors: Influence of the Source/Drain Material

Abstract: During the last years, oxide semiconductors have shown that they will have a key role in the future of electronics. In fact, several research groups have already presented working devices with remarkable electrical and optical properties based on these materials, mainly thin-film transistors (TFTs). Most of these TFTs use indium-tin oxide (ITO) as the material for source/drain electrodes. This paper focuses on the investigation of different materials to replace ITO in inverted-staggered TFTs based on gallium-indium-zinc oxide (GIZO) semiconductor. The analyzed electrode materials were indium-zinc oxide, Ti, Al, Mo, and Ti/Au, with each of these materials used in two different kinds of devices: one was annealed after GIZO channel deposition but prior to source/drain deposition, and the other was annealed at the end of device production. The results show an improvement on the electrical properties when the annealing is performed at the end (for instance, with Ti/Au electrodes, mobility rises from 19 to 25 cm2/V ldr s, and turn-on voltage drops from 4 to 2 V). Using time-of-flight secondary ion mass spectrometry (TOF-SIMS), we could confirm that some diffusion exists in the source/drain electrodes/semiconductor interface, which is in close agreement with the obtained electrical properties. In addition to TOF-SIMS results for relevant elements, electrical characterization is presented for each kind of device, including the extraction of source/drain series resistances and TFT intrinsic parameters, such as (intrinsic mobility) and VTi (intrinsic threshold voltage).

Reducing the contact resistance of bottom-contact pentacene thin-film transistors by employing a MoOx carrier injection layer

Abstract: We report on the reduced contact resistance in bottom-contact (BC) pentacene thin-film transistors (TFTs) with a molybdenum oxide (MoOx) carrier injection layer MoOx layers were placed between the gate insulator and the source-drain (S-D) electrodes instead of the conventional adhesive layer such as Cr or Ti The performance of the BC pentacene-TFT with the MoOx injection layer was significantly improved at low operating voltages The contact resistance of the MoOx∕Au S-D electrodes, estimated using the gated-transmission line method, was nearly two orders of magnitude smaller than that of conventional Cr∕Au electrodes at the gate voltage of −10V The highest performance was obtained with a MoOx injection layer a few nanometers thick, which was comparable to the effective channel thickness of the pentacene-TFT on the gate insulator This result indicated the importance of the direct connection between the MoOx injection layer and the effective channel to reduce the contact resistance

Thermal Conductivity and Contact Resistance of Compressed Gas Diffusion Layer of PEM Fuel Cell

Abstract: This paper discusses the effect of compression pressure on the mechanical and thermal properties of gas diffusion layers (GDL). The stress–strain curve of the GDL revealed one nonlinear and two piecewise linear regions within the compression pressure range of 0–5.5 MPa. The thermal conductivity of the compressed GDL seems to be independent of the compression pressure and was determined to be 1.18 ± 0.11 W m–1 K–1 at room temperature. The thermal contact resistance between the GDL and graphite was evaluated by augmenting experiments with computer modelling. The thermal contact resistance decreased nonlinearly with increasing compression pressure. According to the results here, the thermal bulk resistance of the GDL is comparable to the thermal contact resistance between the GDL and graphite. A simple one-dimensional model predicted a temperature drop of 1.7–4.4 °C across the GDL and catalyst layer depending on compression pressures.

Length-dependent conductance of molecular wires and contact resistance in metal-molecule-metal junctions.

Abstract: Molecular wires are covalently bonded to gold electrodes--to form metal-molecule-metal junctions--by functionalizing each end with a -SH group. The conductance of a wide variety of molecular junctions is studied theoretically by using first-principles density functional theory (DFT) combined with the nonequilibrium Green's function (NEGF) formalism. Based on the chain-length-dependent conductance of the series of molecular wires, the attenuation factor beta is obtained and compared with the experimental data. The beta value is quantitatively correlated to the molecular HOMO-LUMO gap. Coupling between the metallic electrode and the molecular bridge plays an important role in electron transport. A contact resistance of 6.0+/-2.0 Kohms is obtained by extrapolating the molecular-bridge length to zero. This value is of the same magnitude as the quantum resistance.

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.

Correlation between grain size and device parameters in pentacene thin film transistors

Abstract: We develop a general approach to precisely extract the device parameters in top-contact pentacene thin film transistors. The charge trap sites are clarified by analyzing the grain size dependence of the device parameters. The channel mobility and threshold voltage are limited by the charge traps in the channel region, most of which are located not at the grain boundaries but at the organic/insulating-layer interface. The contact resistance decreases by increasing the grain size and is controlled by the charge traps in the contact region, which are suggested to be concentrated at the grain boundaries and at the metal/organic interface.

Bias stress instability in pentacene thin film transistors: Contact resistance change and channel threshold voltage shift

Abstract: Bias stress instability in top-contact pentacene thin film transistors was observed to be correlated not only to the channel but also to the metal/organic contact. The drain current decay under bias stress results from the combination of the contact resistance change and the threshold voltage shift in the channel. The contact resistance change is contact-metal dependent, though the corresponding channel threshold voltage shifts are similar. The results suggest that the time-dependent charge trapping into the deep trap states in both the contact and channel regions is responsible for the bias stress effect in organic thin film transistors.

Measurement of metal/carbon nanotube contact resistance by adjusting contact length using laser ablation

Abstract: A technique of measuring contact resistance between an individual nanotube and a deposited metallic film is described Using laser ablation to sequentially shorten the contact length between a nanotube and the evaporated metallic film, the linear resistivity of the nanotube as well as the specific contact resistivity between the nanotube and metallic film can be determined This technique can be generally used to measure the specific contact resistance that develops between a metallic film and a variety of different nanowires and nanotubes

Quantum resistance metrology in graphene

Abstract: We performed a metrological characterization of the quantum Hall resistance in a 1 μm wide graphene Hall bar. The longitudinal resistivity in the center of the ν=±2 quantum Hall plateaus vanishes within the measurement noise of 20 mΩ up to 2 μA. Our results show that the quantization of these plateaus is within the experimental uncertainty (15 ppm for 1.5 μA current) equal to that in conventional semiconductors. The principal limitation of the present experiments is the relatively high contact resistances in the quantum Hall regime, leading to a significantly increased noise across the voltage contacts and a heating of the sample when a high current is applied.

Systematic TLM Measurements of NiSi and PtSi Specific Contact Resistance to n- and p-Type Si in a Broad Doping Range

Abstract: We present the data on specific silicide-to-silicon contact resistance (rhoc) obtained using optimized transmission-line model structures, processed for a broad range of various n- and p-type Si doping levels, with NiSi and PtSi as the silicides. These structures, despite being attractive candidates for embedding in the CMOS processes, have not been used for NiSi, which is the material of choice in modern technologies. In addition, no database for NiSi-silicon contact resistance exists, particularly for a broad range of doping levels. This letter provides such a database, using PtSi extensively studied earlier as a reference.

Metal–semiconductor contact in organic thin film transistors

Abstract: Optimization of the interface between the source/drain electrode and the organic semiconductor is one of the important factors for organic thin film transistor (OTFT) performance along with the insulator–semiconductor interface. In this Feature Article, items needed for the optimization of the metal–semiconductor interface and methods to measure interface properties are reviewed. Various electrode materials are compared in terms of the work function, contact resistance and the pentacene OTFT performance. The effect of surface modification is also discussed. Experimental data obtained in LAMP is introduced to show the effect of the various material properties more clearly.

Improved conductivity of carbon nanotube networks by in situ polymerization of a thin skin of conducting polymer.

Abstract: The overall conductivity of SWNT networks is dominated by the existence of high resistance and tunneling/Schottky barriers at the intertube junctions in the network. Here we report that in situ polymerization of a highly conductive self-doped conducting polymer “skin” around and along single stranded DNA dispersed and functionalized single wall carbon nanotubes can greatly decrease the contact resistance. The polymer skin also acts as “conductive glue” effectively assembling the SWNTs into a conductive network, which decreases the amount of SWNTs needed to reach the high conductive regime of the network. The conductance of the composite network after the percolation threshold can be 2 orders of magnitude higher than the network formed from SWNTs alone.

A Ruthenium-Based Multimetal-Contact RF MEMS Switch With a Corrugated Diaphragm

Abstract: This paper presents a ruthenium metal-contact RF microelectromechanical system switch based on a corrugated silicon oxide/silicon nitride diaphragm. The corrugations are designed to substantially reduce the influence of the fabrication-induced stress in the membrane, resulting in a highly insensitive design to process parameter variations. Furthermore, a novel multilayer metal-contact concept, comprising a 50-nm chromium/50-nm ruthenium/500-nm gold/50-nm ruthenium structure, is introduced to improve the contact reliability by having a hard-metal surface of ruthenium without substantial compromise in the contact and transmission-line resistances, which is shown by theoretical analysis of the contact physics and confirmed by measurement results. The contact resistance of the novel metallization stack is investigated for different contact pressures and is compared to pure-gold contacts. The contact reliability is investigated for different dc signal currents. At a measurement current of 1.6 mA, the Ru-Au-Ru contacts have an average lifetime of about 100 million cycles, whereas the Au-Au contacts reach 24 million cycles only. For larger signal currents, the metal contacts have proven to be more robust over the Au-Au contacts by a factor of ten. The measured pull-in voltage is reduced significantly from 61 V for flat diaphragm to 36 V for corrugated diaphragm with the introduction of corrugation. The measured RF isolation with a nominal contact separation of 5 mum is better than -30 dB up to 4 GHz and still -21 dB at 15 GHz, whereas the insertion loss of the fully packaged switch including its transmission line is about -0.7 dB up to 4 GHz and -2.8 dB at 15 GHz.

Bias-stress induced contact and channel degradation in staggered and coplanar organic field-effect transistors

Abstract: We have investigated the dependence of bias-stress induced degradation in organic field-effect transistors on the device configuration. We show that separation of contact and channel effects is essential for understanding bias-stress instabilities. In coplanar device configurations, an increase in source contact resistance during current flow is primarily responsible for a rapid device degradation. In contrast, in staggered device configurations, the significantly slower reduction in current is primarily due to charge trapping in the channel leading to an increase in threshold voltage, while the contacts themselves do not exhibit significant degradation.

A Complete Strategy for Conducting Dynamic Contact Resistance Measurements on HV Circuit Breakers

Abstract: Dynamic contact resistance measurement (DRM) is known as an effective technique for assessing the condition of power circuit-breaker (CB) main contacts and arcing contacts. In some SF6 gas CBs, the metallic fluorides (white or gray powder) produced during the arc quenching process mask the actual breaker contact resistance. In this case, the standard DRM method of injecting 100 A dc is no longer applicable. The following paper proposes a complete strategy for conducting DRM on high-voltage CBs based on three relevant parameters: breaker contact speed (low or rated), injected current values (100-2800 A dc), and the presence of metallic fluorides deposited on breaker contacts.