Showing papers on "Contact resistance published in 1980"

Specific contact resistance using a circular transmission line model

Abstract: The measurement of the specific contact resistance of ohmic contacts to semiconductors can be made in a number of ways. One of the methods uses a transmission line model of an ohmic contact on a semiconductor and this paper describes the application of the transmission line model to a contact test pattern of circular symmetry. By using a circular test pattern, the mesa etch step necessary for the standard rectangular test pattern may be omitted, thus simplifying test pattern fabrication.

High-temperature contact structures for silicon semiconductor devices

Abstract: While thin films of TiN and TaN are good diffusion barriers in contact structures which use nickel or gold as a top layer, they show poor barrier properties if aluminum is used as a top layer. It is shown in this letter that stable high‐temperature contacts on silicon semiconductor devices can be produced by using intermetallic compounds of aluminum in combination with TiN and TaN as barrier materials instead of pure aluminum.

Ohmic Contacts to p-GaAs with Au/Zn/Au Structure

Abstract: A reproducible technique for forming ohmic contacts with low contact resistances to p-GaAs is presented. A Au/Zn/Au multilayer structure, which is deposited by sequential evaporation of Au, Zn and Au, is found to realize a satisfactorily low specific contact resistance rc. The value of rc is minimized when the initial thickness of Zn layer is larger than 200 A and the alloying temperature is around 400°C. The minimum value of rc in Ω-cm2 is expressed as rc=1.8×1018p-1.3, where p is the net hole concentration in cm-3. It is also confirmed by Auger spectroscopy that the reduction of rc is caused by the preferential incorporation of Zn atoms into the GaAs bulk during alloying.

Insulative composition for forming polymeric electric current regulating junctions

Abstract: An electric current regulating junction that can be electrically activated to a low resistance state in which it is capable of passing a relatively low reading current. The junction is capable of being activated electrically so as to be switched between low resistance and relatively high resistance states and vice versa. To switch from the low resistance to the high resistance state, one may apply relatively low currents (at least 10 times the magnitude of the reading current) in the form of a current-limited pulse, the pulse being regulated so that it will decay rapidly at the end. The junction comprises a normally insulative, electrically activatable composition having an electrical resistance greater than 10 8 ohms through a layer 0.1-2,540 microns thick. The composition consists essentially of 10 to 90 volume percent of a substantially linear, unitary polymeric binder, and 10 to 90 volume percent of particles substantially homogeneously dispersed in the binder having an electrically conductive metallic interior and a thin insulative surface coating sufficient to impart contact resistance. The unitary polymer has a glass transition temperature of at least 100° C. and may be an aromatic polyimide, poly(amide-imide), poly(ester-imide) or polyamide.

Pd/Ge contacts to n-type GaAs

Abstract: Sintered metal-semiconductor contacts, formed by thin, evaporated layers of Pd and Ge on n -type GaAs, were studied using Auger electron spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, secondary ion mass spectroscopy, current-voltage measurements, and capacitance-voltage measurements. Prior to sintering, the as-deposited Pd/Ge/GaAs contacts were rectifying and exhibited a reproducible Schottky barrier energy φ Bn of 0.67±0.02 eV. Auger analysis indicated the initial behavior of the contact structure, upon sintering, to be an interdiffusion and reaction of Pd and Ge on a non-reacting GaAs substrate. Two germanide phases, Pd 2 Ge and PdGe, were identified using X-ray diffraction and Auger analysis. The intervening Ge layer prevented the reaction of Pd with the GaAs substrate at low temperatures. Because of the PdGe reaction, φ Bn increased to approximately 0.85 eV. Sintering at higher temperatures (i.e. between 300 and 400°C) produced additional reactions between Pd and the GaAs substrate. The electrical properties of the contact remained rectifying and φ Bn exhibited little change from the value of 0.85 eV with the interdiffusion of Pd, Ga, and As. Sintering above 400°C resulted in the formation of ohmic contacts. The diffusion of Ge to the GaAs interface was found to correlate with the onset of ohmic behavior. Current conduction in the contact was best described by thermionic-field emission theory, and a specific contact resistance of 3.5 × 10 −4 Ω-cm 2 was obtained after sintering above 550°C, independent of the initial impurity concentration in the substrate. Over the entire range of sintering temperatures (i.e. at or below 600°C), the interaction between the thin-film layers appeared to be governed by diffusion-controlled, solid-phase processes with no evidence of the formation of a liquid phase. As a result, the surface of the contact structure remained smooth and uniform during sintering.

Ohmic contacts to p-type InP using Be-Au metallization

Abstract: A new contact to p‐InP is reported with beryllium as the acceptor. The contact consists of a thin layer of 3 wt.% Be in Au alloy and a Au overlay sequentially deposited by e‐gun evaporation. Alloying at 420 °C yields Ohmic contacts with low specific contact resistance rc⩽8×10−5 Ω cm2 for InP with NA−ND ≲1×1018 cm−3. To minimize the tendency of InP for thermal dissociation, the alloying temperature can be reduced to 375 °C by adding a thin Pd layer at the semiconductor metallization interface. This is achieved at the expense of a slight increase in resistance.

Electrical contact material

Abstract: PURPOSE: To obtain an electrical contact material having a superior consumption resistance and superior welding resistance by adding a specified percentage of Ni to Ag and by dispersing a specified percentage of a transition metallic carbide. CONSTITUTION: To Ag is added 10W60wt% Ni, and 0.0001W0.5wt% in total of 1 or ≥2 kinds of transition metallic carbides is dispersed. By adding Ni, welding resistance and low contact resistance are provided. By dispersing transition metallic carbides, when electrical contacts are brought into contact with each other and separated, the compounds are allowed to precursively generate arc. Accordingly, arc is dispersed over the whole surfaces of the contacts without causing concentration on a point, and the contacts can be uniformly consumed little by little. COPYRIGHT: (C)1983,JPO&Japio

Composite electrical contact material

Abstract: PURPOSE: To provide a composite electrical contact material enabling opening and closing at low contact resistance by adding a specified amount of Cu to Ag and uniformly dispersing oxide of a specified element such as Al, Mg or Si having higher standard energy for forming oxides than Cu. CONSTITUTION: To Ag is added 0.1W60wt% Cu and further added one or more among Al, Mg, Si, Zr, Zn, Ga, Mn, Sn, In, Ti, Sb, Ni, Fe, Co and Cr each having higher standard energy for forming oxide than Cu. This alloy is crushed to fine grains, internally oxidized in an oxygen atmosphere, compressed, sintered, and worked into electrical contacts. Thus, oxide of such a specified metal is uniformly dispersed in the contact material, and the formation of oxide films on the surface of the contacts is controlled to enable opening and closing at low contact resistance. In addition, the melt-sticking resistance of the contact is enhanced. COPYRIGHT: (C)1981,JPO&Japio

I—V characteristics of GaAs MESFET with nonuniform doping profile

Abstract: A simple analytical model of a GaAs MESFET with non-uniform doping is proposed. The analysis shows that at gate voltages well above the threshold (0.2-0.4 V) for a typical device the current saturation is related to the velocity saturation (with a possibility of a stationary domain formation at drain-to-source voltages high enough). Closer to the threshold the saturation is due to the channel pinchoff. In both regimes the nonuniformity of the doping profile may be essential. Another factor taken into consideration is the source series resistance which includes the contact resistance and the resistance of the gate-to-source region of the device. The calculated dependences of the transconductance and drain current on the gate voltage are in good agreement with the experimental results obtained by Eden, Zucca, Long, and others [1].

Influence of Some Geometric Factors on Contact Resistance Probe Measurements

Abstract: The effect of variations in the geometry and preparation of gold probe tips for contact resistance measurements has been evaluated. Tips prepared by melting and by machining and possessing shapes ranging from a point to hemispheres with radii from 0.9 mm to 3.2 mm were used. The contact resistance values are nearly independent of probe geometry on gold and on very lightly filmed (<5 to 10 A) copper targets. On more heavily filmed copper and nickel targets, the contact resistance varies as much as 2½ orders of magnitude at a fixed contact force. The only known variable is the apparent contact area of the various tips, determined by examination in a scanning electron microscope (SEM) after use. It appears that contact pressure predicts contact resistance more reliably than does contact force.

Electrical resistivity and phase transformation of hematite under shock compression

Abstract: Electrical resistivity measurements of hematite (a-Fe203) were performed under shock compression in the range of 240-760 kbar. The specimens used were coarsely polycrystalline natural material from Bra- zil. The electrical resistivity decreases gradually with increasing shock pressure to 440 kbar and decreases discontinuously to less than Icm from several tens of ohm centimeters at pressures of 440-520 kbar. The phase transformation pressure, implied in Hugoniot equation-of-state is made clear. The transition behavior into the low-resistivity state depends on the crystallographic axis of shock propa- gation. and that the titanium oxide is present only as a trace. Emis- sion spectrochemical analysis shows small amounts of B, Ca, and Si as major impurities. Two types of plate-shaped speci- mens, about 0.6 - 1.0 mm in thickness and 40 to •70 mm 2 in area, were cut from the natural material; the planes of one sample (noted as type 1) are perpendicular to the ( 0112) crys- tallographic axis, which is coincident with one of the principal axes of the octahedron formed by oxygen ions, and the planes of the other sample (type 2) are parallel to that. It is not clear to which direction in the plane normal to (0112) the type 2 specimen corresponds. These orientations were chosen to ob- tain as many samples as possible. Specimens were carefully polished on both parallel faces in order to provide good elec- trical contact with the driver target and the backing electrode. Although the resistivity at atmospheric pressure and room temperature was measured, it was difficult to obtain a good ohmic contact even by vacuum evaporation and deposition of gold or a coating of silver paste on the sample surfaces. The specimen has a resistivity of about 10 kg cm in the 1- to 10-V range, including contact resistance. It was, however, found in other experiments that the contact resistance changed, being lowered about 2 orders and becoming ohmic upon application of pressure, including uniaxial stress components over several kilobars (Kondo et al., 1979a). The initial resistivity of the specimens in the present experiment was estimated to be 250 + 50 g cm by extrapolation from high-pressure values of the above results. The shock experiments were conducted using the double- stage light-gas gun, HS-2, at the Tokyo Institute of Tech- nology. The projectile, 20 mm in diameter, consisted of a high-density polyethylene base with a 1.5-mm-thick copper

Electrode for lead-salt diodes

Abstract: A significantly more stable ohmic contact for a lead-salt semiconductor surface, especially for use in infrared lasers. The contact has layers of platinum, palladium or nickel alternating with gold, and then covered with indium. An Au-Pd-Au-In contact is used on lead-sulfide-selenide, lead-tin-selenide, and lead-tin-telluride of high tin content. A Pt-Au-Pt-Sn contact is preferred for lead-tin-telluride of low tin content. Lower contact resistance is attained if P type lead-tin-selenide and lead-tin-telluride surfaces are previously doped with oxygen, and the initial metal layer is applied in a manner that does not remove it.

Contact Resistance Dependence on InGaAsP Layers Lattice-Matched to InP

Abstract: The effect of composition on the contact resistance between AuZn alloy and p-type InGaAsP layers lattice-matched to InP has been investigated and it was found that a lower contact resistance could be obtained by decreasing the energy gap of the quaternary layer. This fact can be explained in terms of carrier tunnelling as a current transport mechanism.

Field-effect transistors with micron and submicron gate lengths

Abstract: A method for forming ohmic contacts of gold and germanium gold on a gallium arsenide substrate in which a layer of silicon dioxide is placed over the gold in the contact area prior to sinter alloying to improve wetting and reduce contact resistance.

Laser scanning technique for the detection of resistivity inhomogeneities in silicon using liquid rectifying contacts

Abstract: The use of a light-spot scanner presents possibilities of rapid and surveillant measurements of carrier lifetime and resistivity variation in semiconductor crystals. In industrial applications the necessity of a rectifying contact presents problems for further processing of the crystal. Previously, this contact was constructed either by making a p-n junction or a Schottky junction of the wafer under investigation. It is shown here that by using an electrolyte in contact with a plain silicon wafer, one obtains equally accurate measurements of the resistivity variation without contaminating the wafer.

Room‐temperature conductivity and the band structure of n‐Ga1−xAlxAs

Abstract: Conductivity measurements on epitaxially grown silicon‐doped n‐Ga1−xAlxAs as a function of Al concentration x, for 0.10⩽x⩽0.65 are presented. Simple two‐probe measurements were made possible by the development of a low‐resistance Ohmic contact, with the contact resistance independent of x. A calculated three band (Γ, X, and L) conductivity of Ga1−xAlxAs as a function of x shows good agreement with the experimental results. The transition from a direct band‐gap semiconductor to an indirect one occurs at xc =0.45 at 300 °K. The device performance, however, begins to be affected at much lower Al concentration.

Effects of contact resistance and dopant concentration in metal&#8212;Semiconductor thermoelectric coolers

Abstract: The maximum heat that can be pumped by a metal-semiconductor thermoelectric cooling stage depends strongly on the dopant concentration in the semiconductor and on contact resistance at the metal-semiconductor interface which is cooled. A comparison is made between theoretical models describing these effects and experimental data for GaAs, both taken from original measurements and compiled from the literature. A convenient, new technique for determining the Peltier coefficient and the contact resistance of a metal-semiconductor contact is described. The results indicate that, in the case of GaAs, Au:Ge:Ni alloy contacts are effective in minimizing the contact resistance.

Application of polycrystalline silicon load for high performance bipolar memory

Abstract: N-type polysilicon was used for resistor load of high performance bipolar memory. Resistance area and contact area of polysilicon were made by low and high dose As+implantation, respectively. Resistance of polysilicon load was formed with standard deviation of 10% in wafer by controlling lateral diffusion of As from contact area to high resistance area of polysilicon load. A 256 bit ECL RAM with polysilicon resistor load of 9.8 kΩ was fabricated with a cell size of 1870 µm2Typical address access time of 4.6 ns and power dissipation of 340 mW were successfully obtained.

Improved electric contact material of aggsnnbi bas alloy internally oxidation

Abstract: PURPOSE:To increase tensile strength and elongation, a apecific amount of Cu is added to Ag-Sn, Bi based alloy, internal oxidation contact matarial. CONSTITUTION:An Ag alloy containing Sn: 3 to 15 %, Bi: 0.01 to 1.0 %, and Cu: 0.5 to 8.5 % is produced by melting process. The alloy is cast into an approx. 5 kg ingot, the surface of which is peeled off, and the peeled surface is contactly welded with pure Ag plate at high temperatures, then rolled into an approx. 2 mm thickness. The rolled plate is internally oxidized under oxygen atmosphere at 650 deg.C for 200 hours. This process often causes cracks. To prevent this to occur, Fe group metal is added in amount of 0.01 to 0.5% and Cu content is made to 0.1 to 8.5%. The plate is punched into diameter 6 mm disk and used as electric contact material. The material maintains heat resistivity for long periods, is excellent in tensile strength and elongation, and has stabilized contact resistance.

Effect of Si dissolution and recrystallization upon ohmic Al/p‐Si contacts

Abstract: The electrical behavior of a sintered Al/p‐Si ohmic contact is evaluated by means of a new computer fitting technique, the diameter perturbation method. Both the specific contact resistance and the semiconductor resistivity are accurately determined. The effect of sintering temperature and duration is explained by the presence of a nonuniform recrystallized surface layer (Si doped with Al atoms). Certain hypotheses are confirmed by scanning electron micrographs.

Behavior of Line Contacts Upon the Effect of Fault Currents

Abstract: The effect of the passage of high-fault currents (5 kA to 50 kA) through closed contacts has been measured. The contact surfaces were designed so that a region of line contact was established. After the passage of the high current, the contact resistance and the contact weld force were measured. A model of the line contact resistance was established which took into account the heating effects of the current. It was shown, to a first approximation, that the line contact resistance was proportional to the temperature of the contact zone.

Electrodeposited Ruthenium as an Electrical Contact Material A REVIEW OF ITS PROPERTIES AND ECONOMIC ADVANTAGES

Abstract: The potential advantages of ruthenium plating are becoming increasingly appreciated in the electrical contact field. By comparison with rhodium, electrodeposited ruthenium is much less costly and possesses very similar properties of extremely high hardness and resistance to corrosion but with superior resistance to wear; while the dramatic increase in the price of gold has further emphasised the importance of evaluating its merits of low contact resistance and much

Design considerations for planar Schottky barrier diodes

Abstract: The cut-off frequency of the simplest planar Schottky diode on a uniformly doped n-layer of GaAs is derived. The theoretical results are given as functions of doping concentration and layer thickness with the specific contact resistance as parameter. An improved planar diode structure is presented with several short Schottky contact fingers connected in parallel. Experimental values ranging from 100 to 300 GHz agree with the calculated values when parasitic capacitances are taken into account.