Showing papers on "Contact resistance published in 1979"

Photoelectric conversion device

Abstract: A photoelectric conversion device such as a solar cell in which electrodes formed from a conductive paste make ohmic contact with the surfaces of impurity diffused layers respectively formed in a semiconductor substrate. The conductive paste contains ultrafine particles of silver and gold as its principal solid components. The conductive paste further contains, as its additional principal solid components, ultrafine particles of a metal having a eutectic temperature lower than that of silver when alloyed with the semiconductor and a powdery glass material not containing any lead oxide glass component. The electrodes provided by the conductive paste exhibit excellent electrical properties when the conductive paste is subjected to firing treatment at a temperature of about 600° C. Thus, when, for example, the semiconductor substrate is of n-type silicon and a p + -type diffused layer is formed in one of its major surfaces to form a p + /n junction of relatively small depth, the electrode making ohmic contact with the p + -type diffused layer does not penetrate through the p + /n junction and has a low contact resistance. The photoelectric conversion device such as the solar cell thus obtained can operate with a higher conversion efficiency than hitherto and can be manufactured at a lower cost than hitherto.

Ultra low resistance ohmic contacts to n-GaAs

Abstract: Nonalloyed ohmic contacts to n-GaAs with contact resistances (ρc) below 1·0×10−7 Ω cm2 have been obtained using a Ge/GaAs heterojunction system. Metals are evaporated on heavily arsenic-doped germanium (Ge) layers grown on GaAs. Low values of ρc result from the low Schottky barrier height (≈ 0·50 eV) and the high doping levels obtainable for n-Ge(≈ 1020 cm−3).

Improved ohmic properties of Au-Ge Contacts to thin n-GaAs layers alloyed with an SiO 2 overlayer

Abstract: The contact resistivity of Au-Ge contacts on n-type GaAs was reduced by about one order of magnitude by replacing the usual Ni top layer with an SiO 2 layer. Surface coverage and edge definition of the contact areas can be optimised by proper choice of process parameters, making this technology suitable for submicrometre device processing.

Nonalloyed Ohmic contacts to n‐GaAs by pulse‐electron‐beam‐annealed selenium implants

Abstract: Nonalloyed Ohmic contacts to n‐GaAs have been formed by vapor deposition of TiPtAu on pulse‐electron‐beam‐annealed Se‐implanted surfaces. Peak carrier concentrations were about 1.2×1019/cm3, yielding a specific contact resistance rc≲6×10−7 Ω cm2.

Method and apparatus for measuring the ohmic contact resistance of an electrode attached to body tissue

Abstract: A method and apparatus are disclosed for measuring the ohmic, that is, purely d-c, resistance at the area of contact between cardiac tissue and a pacemaker electrode surgically implanted in the heart of a patient requiring a pacemaker. The contact resistance is measured by apparatus connected across the electrical circuit formed by the electrode and heart. The apparatus includes circuitry for sampling and holding the instantaneous voltage across the electrical circuit formed by the electrode and heart at the onset of a pulse generated by the pacemaker pulse generator, at which time the effect of a parallel capacitance in the electrical circuit formed by the pulse generator, electrode wire, electrode, heart, and return path through the body to the pulse generator is such that the current initially produced is determined only by the voltage and equivalent output impedance of the pulse generator, the resistance of the electrode wire, and the resistance at the area of contact between cardiac tissue and the electrode. The apparatus further includes analog signal processing circuitry for deriving the contact resistance from the instantaneous voltage based on an equivalent circuit model for the electrical circuit formed by the pacemaker and the heart taking into account the effect of the parallel capacitance at the onset of a pulse. The apparatus also includes a device for displaying the measured contact resistance. The disclosed method and apparatus are also applicable for measuring the ohmic contact resistance of an electrode attached to other body tissue.

Step Potentials and Body Currents Near Grounds in Two-Layer Earth

Abstract: The equations customarily used in safety calculations for grounding electrodes assume that soil conductivity does not vary with depth. A more realistic model assumes that the soil consists of two horizontal layers of different conductivity. This may occur, for example, if a thin surface layer consists of wet soil, thawed soil, or concrete, and a thick layer of underlying soil is frozen, or consists of rock or dry soil. Such conditions markedly change the step voltage, contact resistance, and body current a creature on the surface will experience in the vicinity of a buried ground electrode. Equations are presented for voltage, voltage gradient (step voltage), contact resistance, body current, and electrode resistance in the vicinity of a ground electrode in the shape of a long buried wire in a two-layered earth. Graphs are also presented to give a quantitative and qualitative understanding of the effect of such layering on step voltage and body current.

Contact Resistance and Arc Erosion of W/Ag and WC/Ag

Abstract: A multitude of tungsten/silver (W/Ag) and tungsten carbide/silver (WC/Ag) contact materials of different compositions, origins, manufacturing methods, and contact sizes are investigated over a wide current range I = 60-1800 A. Resistance is measured after each switching-off operation and evaluated statistically. The results are a strong dependence of contact resistance on switching current and contact size, with high values caused by semiconducting layers at low arc currents and low metallic values at high currents. Investigations of the contact surfaces after switching help to explain this phenomenon. The resistance decrease nearly coincides with a considerable increase in erosion. While at low currents there is no significant difference in the erosion rates between W/Ag and WC/Ag, the latter tends to have lower rates at high currents.

A Comparison for the Effects of Various Forms of Silicon Contamination on Contact Performance

Abstract: In recent years increased concern has been noted for the effect of silicon contamination on the performance of electrical contacts. Several recent papers have described the effects of silicone contamination on contact behavior. Since contact contamination for the element silicon can exist as both organosilicon and inorganic mineral compounds, a study is made on the effects for the type of silicon compound, as well as the concentration and distribution of the compound on contact behavior. A comparison is made for the performance of contacts contaminated with various silicone, compounds and contacts contaminated in various silicon mineral grit materialS. The performance is measured in terms of contact resistance and electrical circuit continuity immediately after contact closure for both unused contacts and contacts subjected to switching several different electrical loads. From the results it can be seen that besides the concentration of silicon contamination, the particle size and form of silicon contamination are factors which influence contact behavior.

High-Current Brushes, Part III: Performance Evaluation for Sintered Silver-Graphite Grades

Abstract: The results of varying the material composition, specifically the metal mass fraction, on the performance of silver-graphite brushes at high-current densities (0.8 MA/m2) in a carbon dioxide atmosphere, have been evaluated. Material properties which were measured included the brush density, electrical conductivity, and hardness. These properties were used in the evaluation of the brush performance when sliding on copper slip rings at a speed of 12.7 mis. Measured parameters included the contact resistance, friction coefficient, and wear rate. The results of this analysis indicate that the resistive behavior was dominated by constriction effects, with the number of contact spots apparently ranging from 2-15. The film contribution to the total resistance was small, the resistivity being less than 6 X 10-13 \Omega ·m2. Friction measurements indicated a specific shear strength of 10-24 MN/m2which, if caused by an adsorbed water film, would correspond to a film thickness in the range from about 0.2-0.4 nm. Wear rates well into the microwear regime have been observed, even at the high-current densities used. However, a satisfactory explanation for the strong dependence of wear on metal content (from 0.7-60 mm3/Mm) as the metal mass fraction varied from 0.4-0.9 has not yet been evolved.

Contact resistance in metal-semiconductor systems☆

Abstract: A new method for analyzing the influence of extrinsic parameters, such as contact shape and contact area, on the contact resistance of the metal-semiconductor system is developed. The method incorporates a previously established contact theory in the Transmission Line Model used earlier for rectangular and circular contacts. Theory is also extended to the circular ring contact in this article. Good agreement with measured results substantiates the applicability of the method for the design of contact shapes and areas in semiconductor device fabrication processes. Various contact shapes and areas are investigated and the total contact resistances are compared to one another. It is shown that the contact with long thin stripes possesses the lowest contact resistance.

Effect of Fretting on the Contact Resistance of Aluminium with Different Contact Materials

Abstract: The effect of fretting on the contact resistance of aluminium wire (EC grade) and different plating materials (Ag, Cd, Ni, Sn, Zn) has been studied. The fretting tests were conducted with simulated connector configurations using a differential thermal expansion fixture to produce fretting damage. In addition, the waveforms of the contact voltage, scanning electron microscopy (SEM), and X-ray fluorescence analysis were used to study thc processes involved. The results show that the contact resistance of all combinations of aluminium-contact materials increases very rapidly after a given number of fretting cycles. The effects of fretting are reduced to some extent by applying higher electrical and contact loads. The waveforms of the contact voltage across the couples are severely distorted by the fretting action. The SEM and X-ray fluorescence analyses showed that the contact zones are severely damaged and that substantial transfer of material occurred as a result of the fretting action.

Degradation of Electrical Contacts Caused by Oscillatory Micromotion Between the Contact Members

Abstract: The influence of oscillatory movement on the contact resistance is discussed on the basis of experiments with contacts in a crossed rod configuration, the contact members being Al-Al and Cu-Cu. Measurements were carried out for movements of amplitudes within the range 0.4-18 µm and mechanical loads between 20-170 N at frequencies 10-100 cycles/h. The experimental results show that micromotion under certain conditions causes rapid and extensive degradation. For Al contacts with load 20 N, the resistance increases to 50 times the initial value after 200 cycles.

Semiconductor device and its manufacture

Abstract: PURPOSE:To reduce the contact resistance and thus to enhance the reliability by applying plural units of protruded electrodes provided on the semiconductor element onto the plural leads composed of the noble metal layer which is formed by plating and securing a contact between the lead and the electrode through conduction and heating via the bonding tool CONSTITUTION:The copper foil is first adhered onto one main surface of film 2 composed of the heat-resistance, flexible and insulating polyimide resin and with hole 4 provided Then lead 3 is formed by the photo etching, one end of which protrudes through hole 4 to be inner lead 5 along with the other end protruding outside to be used as the outer lead 6 And then Ni plating layer 7 and Au plating layer 8 are coated over lead 3 On the other hand, semiconductor device 9 containing plural units of Sn plating layer 13 coated Au vamp electrode 10 on the surface is prepared to be put on stage 14, and electrode 10 and lead 5 are opposed to each other to be given the pressure contact via bonding tool 15 After this, the conduction is given between electrode 16 and 17 of the tool to fuse layer 13, and then electrode 10 is adhered to lead 5 via the Au-Su eutectic caused

Ohmic contacts on ion‐implanted n‐type GaAs layers

Abstract: Contact resistance of Ohmic electrodes formed on either Se‐ or (Se+Ga) ‐implanted n‐type GaAs layers was studied. Experimental results have shown that a low specific‐contact resistance of 2.9×10−7 Ω cm2 can be achieved on GaAs layers having a maximum carrier concentration of 1.8×1019 cm−3, which have been formed by a dual‐species (4.4×1014 cm−2 Se+ 5.0×1014 cm−2 Ga) implantation in Cr‐doped semi‐insulating GaAs heated to 400 °C and by subsequent annealing at 950 °C using an oxygen‐free CVD Si3N4 layer as an encapsulant.

Laser method for forming low-resistance ohmic contacts on semiconducting oxides

Abstract: This invention is a new method for the formation of high-quality ohmic contacts on wide-band-gap semiconducting oxides As exemplified by the formation of an ohmic contact on n-type BaTiO3 containing a p-n junction, the invention entails depositing a film of a metallic electroding material on the BaTiO3 surface and irradiating the film with a Q-switched laser pulse effecting complete melting of the film and localized melting of the surface layer of oxide immediately underlying the film The resulting solidified metallic contact is ohmic, has unusually low contact resistance, and is thermally stable, even at elevated temperatures The contact does not require cleaning before attachment of any suitable electrical lead This method is safe, rapid, reproducible, and relatively inexpensive

Metallization systems for ohmic contacts to p- and n-type GaAs

Abstract: Various metallization systems to n- and p-type GaAs have been investigated. The fabrication of the ohmic contacts and the method of contact resistance measurements are described. For each metallization system investigated, there exists an optimum alloying cycle (i.e. alloying temperature and time) which gives minimum contact resistance.

Electrical contact material

Abstract: PURPOSE: To provide an electrical contact material made of sintered alloy of Ag, Ni and NiCr and having short arc duration, superior fusion bonding resistance, superior consumption resistance, superior contact resistance stability, etc. CONSTITUTION: Ag powder, Ni powder and NiCr powder are mixed in a predetermined ratio, calcined, and sintered to obtain the desired electrical contact material. The NiCr powder consists of, by wt., 65W95% Ni and 35W5% Cr, preferably 80% Ni and 20% Cr. The resulting sintered alloy has a composition consisting of, by wt., 2.5W35.0% NiCr, 5W15% Ni and the balance Ag. In addition, this alloy is very useful as an electrical contact material applicable to a nofuse circuit breaker, etc. COPYRIGHT: (C)1981,JPO&Japio

Electrical contact point material

Abstract: PURPOSE:To provide an electrical contact point material for a relay, etc. with low contact resistance, superior resistance to discharge consumption and fusion, etc., obtd. by adding Ni to Au and further adding noble metals such as Ag and Pb, and metal oxides. CONSTITUTION:The contact point material is made of Au alloy contg. Ni; 1-15 wt%. To the alloy may be added 0.1-10 wt% of one or more out of Ag, Pd, Pt, Ir, Os, Rh, Ru, Re and Cu. In place of the metals, 0.1-15 wt% of one or more out of oxides of Ni, Cu, Zr, Be, Mg, V, Co, Zn, Na, Ga, Sn, Pb, Mn, Rh, Re, Te, Sb, etc. may be added or the metals and the metal oxides may be added simultaneouly.

The Switching Performance of Refractory Carbide-Silver Contacts

Abstract: Eight refractory carbide-silver contacts have been evaluated for switching performance: WC-Ag (WC 40 volume percent); WC-AG-Co ((a)WC 45 volume percent, Co 7 volume percent, (b) WC 35 volume percent, Co 7 volume percent); TiC-Ag ((a)TiC 80 volume percent, b) TiC 60 volume percent, c) TiC 48 volume percent); and NbC-Ag ((a)NbC 72 volume percent b) NbC 48 volume percent). The contacts were placed in an experimental switch and were operated to make and break a 20-A 110-V resistive circuit. The contact resistance was monitored at 0, 1000, 2000, and 3000 switching operations by measuring the temperature rise at the fixed contact terminal after 20 A had been flowing for ½ h. The contact surfaces were examined using a scanning electron microscope. The performance of the WC-Ag was similar to that which was previously observed with W-Ag contacts; high contact resistances were measured after only 1000 operations. The WC-Ag-Co contacts showed consistently lower contact resistance values than were observed for the WC-Ag contacts. The TiC-Ag and NbC-Ag contacts performed about as well as the WC-Ag-Co contacts did. These data showed that the presence of carbon in the WC-Ag contacts did little to alleviate the problem of high contact resistance values resulting from insulating oxides of W and Ag forming on the contact surfaces. The presence of Co, on the other hand, resulted in conditions which were not favorable to the formation of the silver tungstate. The TiC-Ag data showed that Ag was always present on the contact surfaces together with TiC and with oxides of titanium; there was no evidence of the formation of silver titanate. The NbC-Ag data were similar to the TiC-Ag data. After continued switching, however, the TiC and NbC contacts began to form a surface skin of refractory material on the contact surface. The relative merits of these refractory carbide-silver contacts are discussed.

Semiconductor device and its manufacture

Abstract: PURPOSE:To facilitate the formation of electrodes by depositing Ni and the like on the main surface of one side of a substrate which has a diffused layer on the main surface of the other side, applying conductive paste whose main components are Ag, Au, and Al on the diffused layer, and applying the conductive paste whose main component is Ag on the Ni side at the same sintering temperature. CONSTITUTION:A conductive paste 4 whose main components are Ag, Au, and Al are provided on a diffusion layer 2 which forms a pn junction. On an n-type substrate, is deposited Ni which has the same effect to raise the surface-impurity concentration, and is applied a conductive paste 5 whose main component is Ag. The paste 4 is well contacted at temperatures (550-650 deg.C) lower than before, and the electrode which has low contact resistance and is not subjected to the break through the shallow diffusion layer can be reproduced. The paste 5 is sintered in concurrence with the sintering of the paste 4 and makes ohmic contact with the substrate, generating nickel silicide at the boundary between the substrate and Ni, thereby the resistance is decreased. When the sintering temperature exceeds 650 deg.C, break through occurrs. At the temperature lower than 550 deg.C, the contact resistance is increased, and the transducing efficiency is degraded.

A Low-Cost Solar-Cell Front Contact Using Trapped Silver Mesh and Electrostatic Bonding

Abstract: One of the major costs of modern solar-cell manufacture is that of applying a metallized contact grid to the cell front surface. If solar energy is to become a viable source of !ow-cost electricity, this expense must be reduced significantly. To keep efficiency high, a metallization grid must provide narrow closely spaced high conductivity lines. A new system to provide this contact with a silver mesh trapped between the cell and an encapsulating glass cover has been demonstrated. Borosilicate glass is permanently joined to the cell by electrostatic bonding, an adhesive-free field-assisted glass-metal sealing technique. During this process the glass is deformed around the silver mesh to form a permanent optically coupled integral bond to the cell. This hermetic seal prevents the silver from oxidizing and destroying the electrical contact formed during the bonding process. Cells produced this way have been demonstrated with curve fill factors of 0.69. A thin titanium layer evaporated on the mesh seems to improve the results. Specific contact resistance measured for this system is on the order of 20-30 m \Omega -cm 2 .

Electrical contact materials of internally oxidized Ag-Sn-Bi alloy

Abstract: Internally oxidized Ag-Sn-Bi alloy electrical contact materials are improved of their tensile strength and rate of consumption by the addition of 0.1-8.5 weight % of Cu, whereby they present stable contact resistance and less amount of consumption. The alloy may comprise 0.01-0.5 weight % of one or more elements of the iron family.

MOSFET e.g. silicon-on-sapphire FET - where source, drain, and gate are covered with metal silicide reducing contact resistance

Abstract: The FET has a source zone and a drain zone with a prescribed surface resistance; and above or below the surface of zones is a zone with a lower resistance. The FET also has a polycrystalline silicon gate with a prescribed resistance value; and above or below the surface of gate is a zone with lower resistance. Some zones pref. consist of a metal silicide, in which the metal is Pt, Pd, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, or Ni. The silicide is pref. formed by the selective spraying of one of the above metals onto the source, drain and gate, followed by heating to form the silicide. Metal leads made e.g. of Al can be used; a low contact resistance is obtd.; and the working speed of the FET is increased.

Direct Observation for the Effect of Electric Current on Contact Interface

Abstract: The conditions of the contact interface affect contact resistance characteristics. Therefore, information of the contact interface is very important for the study of contact performance. However, a real contact area, which carries the electric current path, is quite small. If the area can be observed directly, much information of the contact interface will be obtained. Such an investigation has not been performed for electric contacts energized by current. The experimental and technical realization of the equipment for measuring and directly observing the characteristics of contact interface energized by current is described. It is composed of an automatically contact-making apparatus, conductive transparent electrodes, and an inverted type metallurgical microscope. Investigations were carried out for various kinds of contact materials from the viewpoint of how the flowing current affects the interface of real contact area. The real contact area increases markedly by Joule heating when the temperature in the area rises to the recrystallization temperature peculiar to metals. The softening temperature agrees with the recrystallization temperature. Sulfide films deform due to softening. This softening of the films causes !ow contact resistance characteristics.