Showing papers on "Contact resistance published in 1981"
TL;DR: In this article, it is suggested that the observed (doping)−1 dependence of the contact resistance is due to spreading resistance domination of current paths through submicron regions where heavy doping occurs.
Abstract: The alloyed AuGe‐based contact is widely used to make ohmic connections to GaAs. It has been presumed that the regrown alloyed region is heavily doped so that carrier transport is by tunneling. The electrical and metallurgical properties of this heterogeneous system have been extensively studied and have been shown to be spatially nonuniform. Details of fabrication technique, analysis, and theoretical interpretation of its behavior will be discussed. It is suggested that the observed (doping)−1 dependence of the contact resistance is due to spreading resistance domination of current paths through submicron regions of the contact area where heavy doping occurs.
226 citations
TL;DR: In this paper, an epitaxial layer of n−Ga1−xInxAs grown by molecular beam epitaxy on n•GaAs which is graded in composition from x = 0 at the GaAs interface to 0.8?x?1.0 at the surface will produce a structure with a nearly zero Schottky barrier height for the metal-Ga 1−xAs interface and hence a low resistance ohmic contact.
Abstract: Ohmic contacts were studied on structures which utilize the fact that for InAs surfaces Fermi level pinning occurs at or in the conduction band. It was found that an epitaxial layer of n‐Ga1−xInxAs grown by molecular beam epitaxy on n‐GaAs which is graded in composition from x = 0 at the GaAs interface to 0.8?x?1.0 at the surface will produce a structure with a nearly zero Schottky barrier height for the metal–Ga1−xInxAs interface and hence a low resistance ohmic contact. A transmission line measurement of non‐alloyed contact resistance of 5×10−7
200 citations
TL;DR: In this paper, a study of base and electroplated gold contacts with the gold in a range of thicknesses revealed that transfer dominates fretting and that an equilibrium distribution of a contact metal with an underplate and a substrate is attained which is the same for both members, although they may initially have been different.
73 citations
TL;DR: In this article, the adhesion and deformation properties of metal contacts were studied in a magnetic scanning electron microscope, incorporating an Auger facility for surface characterization, and it was shown that the loading-unloading cycle is highly irreversible, the junction finally separating in a ductile manner.
53 citations
TL;DR: In this article, the magnetic field dependence of the transconductance of short-gate GaAs FET's was demonstrated to provide a direct means of characterizing the mobility profile of the active layer of the device, which does not require a capacitance measurement, and which is relatively insensitive to the parasitic series resistance associated with the source and drain contacts.
Abstract: It is demonstrated that the magnetic field dependence of the transconductance of short-gate GaAs FET's provides a direct means of characterizing the mobility profile of the active layer of the device, which does not require a capacitance measurement, and which is relatively insensitive to the parasitic series resistance associated with the source and drain contacts. The results are shown to be in agreement with those obtained from conventional measurements on a long-gate FET test structure.
43 citations
Patent•
07 Apr 1981TL;DR: In order to increase the stability of a device comprising at least one electrode and a conductive polymer composition in contact therewith, the contact resistance between the electrode and the composition should be reduced as discussed by the authors.
Abstract: In order to increase the stability of a device comprising at least one electrode and a conductive polymer composition in contact therewith, the contact resistance between the electrode and the composition should be reduced. This can be achieved by contacting the molten polymer composition with the electrode while the electrode is at a temperature above the melting point of the composition. Preferably, the polymer composition is melt-extruded over the electrode or electrodes, as for example when extruding the composition over a pair of pre-heated stranded wires.
39 citations
TL;DR: In this article, the authors discuss the types of contacts that can be obtained from the doped layer of low resistivity between metal system and semiconductor, which is ideal for obtaining good ohmic contacts to compound semiconductors.
Abstract: Publisher Summary With the development of a wide variety of III-Vcompound semiconductor devices ( for e.g., injection lasers, light-emitting diodes, Gunn diodes, microwave Schottky-barrier and avalanche diodes, field-effect transistors, bistable resistors, and photodiodes), the need for low resistance, reproducible, stable, and reliable ohmic contacts to these semiconducting materials is increasingly felt. This chapter discusses the types of contacts. Among the various typed of contacts discussed in the chapter, the doped layer of low resistivity between metal system and semiconductor seems to be ideal for obtaining good ohmic contacts to compound semiconductors. From a considerable reduction in the contact resistance, the influence of injection by the ohmic contact is diminished because the lifetime and diffusion length of the minority carrier decrease appreciably with an increase in doping density. The fundamental processes at the surfaces and interfaces are rather limited and systematic about the metallurgical structure of various ohmic contacts to compound semiconductors. The availability of molecular beam epitaxial and ion implantation techniques may be possible to have more information about the ohmic contacts. Depending on the type of ohmic contact encountered in an actual device, a number of methods are available for the evaluation of specific contact resistance.
36 citations
TL;DR: Ohmic contacts to p-type CdTe are important for the development of solar cells based on this semiconductor, as for instance CdS/CdTe or ITO/cdTe solar cells as discussed by the authors.
Abstract: Ohmic contacts to p-type CdTe are important for the development of solar cells based on this semiconductor, as for instance CdS/CdTe or ITO/ CdTe solar cells. Ohmic contacts to CdTe Bridgman crystals, doped with phosphorus, have been examined with respect to their resistivity dependence and their variation as a function of time. The ‘specific’ contact resistance r shows a linear dependence on the bulk resistivity; in addition, it is affected by the oxygen content of the CdTe. The lowest r obtained was 0.07Ω cm. With one exception, ali the contacts with nickel, gold and platinum deposited on different crystals show a more or less pronounced increase of r as a function of time.
32 citations
Abstract: Electrodeposited pure gold, cobalt-hardened gold, and clad palladium, 60Pd40Ag and 40Pd60Ag were exposed for up to four years in air-conditioned telephone central offices and in a nonair-conditioned room at a central office location. The contact resistance of these materials was determined by probing, and surface films were evaluated by several analytical methods. None of the metals were significantly degraded at sites that were relatively free of gaseous air pollutants and where relative humidity was controlled to moderate levels. The gold-coated samples typically displayed lower and more stable contact resistances than the palladium materials. Palladium and the palladium-silver alloys acquired tarnish films which significantly increased contact resistance in the nonair-conditioned room where relative humidity was high some of the time and which contained traces of gaseous chlorine compounds. The 40Pd60Ag alloy was worse than palladium and 60Pd40Ag, in part because it reacted with sulfur-containing pollutants as well as with the chlorine compounds. Porous golds on copper and nickel underplate were not affected by any of the test environments. A finely divided particulate at one site degraded the contact behavior of the smooth claddings, but not the electrodeposited golds which had micronodular surface roughness.
32 citations
TL;DR: In this article, the formation of Mo/Si contacts by implantation of phosphorus ions was studied, and the effect of post-implant annealing was also discussed in terms of doping, microstucture, and contact resistance.
Abstract: Formation of Mo/Si contacts by implantation of phosphorus ions was studied. The implantation was carried out at temperatures of −196, 25, and 150 °C and a fluence ranging between 1015 and 1017 ions cm−2. The morphological and structural characterizations were done with scanning electron microscopy, transmission electron microscopy, and x‐ray diffraction. Hexagonal MoSi2 phase was identified in samples implanted with more than 1016 ions cm−2 at all three implantation temperatures. Traces of MoP were found in the sample implanted with 1017 ions cm−2 at 150 °C. Measured effective contact resistance showed ohmic behavior in as‐implanted samples except for samples implanted with 1015 ions cm−2 at 150 °C. Smooth surfaces of implanted MoSi2 structures remained after post‐implant annealing at 850 °C for 1/2 h in H2 ambient. The effect of post‐implant annealing is also discussed in terms of doping, microstucture, and contact resistance.
31 citations
TL;DR: The major contact wear processes are adhesion, abrasion and fretting as discussed by the authors, which occurs when the metal contacts are worn through to their base substrates, and is characterized by transfer from the member with the larger surface involved in sliding to that with the smaller surface.
TL;DR: In this article, a new kind of low-loss and high-speed diode (LLD) is realized by utilizing this electrode structure, which shows a remarkably fast recovery as a Schottky diode, using no gold doping.
Abstract: A novel electrode structure to realize an "ideal" ohmic contact is proposed. A new kind of low-loss and high-speed diode (LLD) is realized by utilizing this electrode structure. LLD shows a remarkably fast recovery as a Schottky diode, using no gold doping, while the reverse blocking voltage and operating temperature limit are far higher than for a Schottky diode. LLD is easily incorporated into monolithic combination with transistors, and is useful for various power applications.
TL;DR: In this paper, the transient thermal response of two semi-infinite solids not making perfect contact, is treated analytically by modeling the interface to be a series of equally spaced strips with perfect contact.
Abstract: The problem of the transient thermal response of two semi-infinite solids not making perfect contact, is treated analytically by modeling the interface to be a series of equally spaced strips making perfect contact The remaining area is assumed to perfectly insulated, and a criterion is established for the validity of this assumption, taking radiation into consideration The mixed interface conditions present a considerable difficulty and a long-time perturbation scheme is therefore used to obtain approximate expressions for the transient temperature distributions, average heat flux and the thermal contact resistance The method is applicable to a large class of problems with mixed boundary conditions for which the existing techniques give exact solutions only for the steady state
TL;DR: In this article, the authors apply percolation theory to the problem of sealing a contact against ingress of corrosive atmospheres, and show that roughly 44 percent of randomly placed real contact area is a threshold value, beyond which open pathways for diffusion of the external atmosphere become blocked.
Abstract: The interface between two contacting metals, neither of which is noble, can be established under conditions such that the electrical resistance is essentially the same as for clean metals. In addition, this behavior has been observed over extended periods of time in chemically hostile environments. Some basic physical properties of contacts are applied for a qualitative understanding of these results. Surface topographical studies have shown that the real load bearing area in a local indentation is never less than 50 percent of · the nominal area of contact. The nature of the bulk deformation during the loading of the interface and the behavior of multiple electrical contact spots ensure that, even in the presence of insulating films, the fraction of true area in electrical contact is sufficient for good conduction. The application of percolation theory to the problem of sealing a contact against ingress of corrosive atmospheres predicts that roughly 44 percent of randomly placed real contact area is a threshold value, beyond which open pathways for diffusion of the external atmosphere become blocked. Since the true contact area exceeds this threshold, such interfaces will be gas-tight.
TL;DR: In this article, the effect of current cycling on the contact 10ad, resistance, and temperature of bolted aluminum-to-aluminum joints of high ampacity has been studied, and the results indicate that current cycling causes significant changes in the contact load, resulting in a drastic loss of contact force.
Abstract: The effect of current cycling on the contact 10ad, resistance, and temperature of bolted aluminum-to-aluminum joints of high ampacity has been studied. The results show that current cycling causes significant changes in the contact load, resulting in a drastic loss of contact force. Contact resistance is less affected by current cycling, and connector temperature shows a normal beating effect produced by the cycling current. A new accelerated current cycling test has been proposed. The test is based on the passage of relatively high current for short periods of time followed by longer cooling times. The results obtained from the new test indicate that this testing procedure is a valid alternative to those presently in use, and that it can be used as a method for detecting the deterioration of electrical connections. The results also show that the use of Belleville washers, plating, and lubrication i lnproves the performance of the bolted joints under current cycling conditions.
TL;DR: In this article, the formation of alloyd ohmic contacts on n -InP using sequentially deposited Sn plus Au films was investigated and the specific contact resistance for metallizations with a Sn content of 5 at. % was determined for annealing temperatures between 250 and 500°C.
Abstract: The formation of alloyd ohmic contacts on n -InP using sequentially deposited Sn plus Au films was investigated. The specific contact resistance for metallizations with a Sn content of 5 at. % was determined for annealing temperatures between 250 and 500°C. The minimum specific contact resistance, r c = (1.8±0.9) × 10 −6 ohm-cm 2 occurred for a narrow range of annealing temperatures between 380 and 410°C on substrates with n = 3 × 10 18 /cm 3 . For annealing temperatures 350°C the contacts were non-Ohmic and above 420°C the resistance increased dramatically. Contact morphology and metallurgy were studied by optical and scanning electron microscopy, X-ray diffraction, Auger electron spectroscopy and Rutherford backscattering. Films annealed above 320°C contained several phases, mainly Au 4 In, AuSn and polycrystalline InP. The contacts annealed at temperatures above 410°C were composed predominantly of the single phase Au 3 In 2 .
Patent•
27 Oct 1981
TL;DR: In this paper, the first wiring layer of polysilicon on the diffusion layer of a silicon substrate to introduce impurities, creating an opening with a surface coated by an insulation film and forming the second metallic wiring layer after the introduction of impurities of high concentration.
Abstract: PURPOSE:To provide a device having low wiring resistance and a high degree of integration by providing the first wiring layer of polysilicon on the diffusion layer of a silicon substrate to introduce impurities, creating an opening with a surface coated by an insulation film and forming the second metallic wiring layer after the introduction of impurities of high concentration CONSTITUTION:p Layer 3 is provided by means of B diffusion on n type silicon substrate 1 to create the first wiring layer with polysilicon 4 of B dope An interlayer insulation film 5 is formed through thermal oxidation, a window is opened selectively and n layer 7 is created by injecting B ion Following this process, aluminum is vaporized to form the second wiring layer Under this constitution, specially a contact resistance between aluminum and polysilicon is significantly reduced by the formation of n layer, thus decreasing a wiring resistance on the polysilicon, making possible high integration and accelerating action properties
TL;DR: In this paper, the compatibility of the Al-Cu-Si metallization with the very large scale integrated requirements of interconnection and Si-metal contacts for shallow junction devices is discussed.
01 Jan 1981
TL;DR: In this article, the use of low temperature plasma deposited silicon nitride combined with selective tungsten deposition yields a process that is compatible with both low interconnect resistance requirements and standard polysilicon gate technology.
Abstract: Device scaling leads to high resistance interconnects for both polysilicon and diffusion lines. The use of low temperature plasma deposited silicon nitride combined with selective tungsten deposition yields a process that is compatible with both low interconnect resistance requirements and standard polysilicon gate technology. Low interconnect resistance (1Ω) and low contact resistance (< 5× 10-7Ω cm2) to polysilicon and diffusion have been obtained using the process flow described in this paper. Reduced temperature cycles at the end of the process and elimination of phosphorous in the interlayer dielectric make this process ideal for high density, high reliability VLSI applications.
TL;DR: Backside irradiation through the substrate with a Q‐switched Nd:glass laser has been used to produce Au‐Ge ohmic contacts on GaAs that exhibit good ohmic contact behavior and good surface morphology.
Abstract: Backside irradiation through the substrate with a Q‐switched Nd:glass laser (l = 1.06 mm) has been used to produce Au‐Ge ohmic contacts on GaAs. Conventional thermal alloying was done for comparison. The structure of the contacts was investigated by 2‐MeV He‐ion Rutherford backscattering technique, photographs, and I‐V characteristic measurements. The irradiated Au‐Ge contacts exhibit good ohmic contact behavior and good surface morphology. Ohmic contacts with specific contact resistance rc less than 2×10−5 W cm2 have been measured within the laser energy density of 0.3–0.5 J/cm2, while the thermally alloyed contacts yielded rc = 1.3×10−4 W cm2.
01 Jan 1981
TL;DR: In this article, simulation is used to show how the lateral subdiffusion regions of S/D represent a dominant, V GS -dependent portion of the total resistance, since the doping profile there is steeply decreasing and the carrier concentration can be modulated by the gate voltage.
Abstract: At small V DS , g m reduction in MOSFET's is often attributed to mobility degradation due to increased vertical electric field with increasing V GS . This is correct for long channel devices; however, for short channel devices the parasitic series resistance of source/drain, R T , has a similar effect in reducing the g m value. In this paper, simulation is used to show how the lateral subdiffusion regions of S/D represent a dominant, V GS -dependent portion of the total resistance, since the doping profile there is steeply decreasing and the carrier concentration can be modulated by the gate voltage.
TL;DR: In this article, a scanning Auger microanalysis was conducted on the surface and in depth on the thin film structure before and after heating at 300 ˚C for 4 h. This characterization has led to improved understanding of the bonding problems and variation of contact resistance with this metallization system.
Abstract: The gold–nickel–copper system, with nickel the intended diffusion barrier, has been used extensively in the electronics industry for wire spring connectors, thin films on ceramic, and connectors on printed circuit boards. Although no visible contamination can be seen on the surface of the gold, poor bonding or high contact resistance frequently occurs. It has been assumed that some grain boundary diffusion of nickel has been occurring through the 2 μm gold film. A scanning Auger microanalysis was conducted on the surface and in depth on the thin film structure before and after heating at 300 °C for 4 h. Two‐dimensional Auger analysis, after heating, showed the nickel to be distributed along the grain boundaries on the surface of the gold film. Subsequent Auger depth profiling showed the nickel layer to be oxidized and approximately 50 A in depth. This characterization has led to improved understanding of the bonding problems and variation of contact resistance with this metallization system.
TL;DR: In this article, the authors investigated the Si-implanted, n+ layers on semi-insulating InP and found that the Au/Ni/AuGeNi/InP system shows a good ohmic behaviour with the specific contact resistance ρ c of 2 × 10 −5 Ω cm 2 and the minimum contact resistance Z c of ∼ 2 ×10 −3 Ωcm for a Si-dose higher than 2 × 1014 cm−2 at 100 or 200 keV.
Abstract: Ohmic contacts to Si-implanted, n+ layers on semi-insulating InP are investigated on the basis of the transmission line model. It is found that Au/Ni/AuGeNi/InP system shows a good ohmic behaviour with the specific contact resistance ρ c of 2 × 10 −5 Ω cm 2 and the minimum contact resistance Z c of ∼ 2 × 10 −3 Ω cm for a Si-dose higher than 2 × 1014 cm−2 at 100 or 200 keV. The results indicate that, in the FET fabrication, at least 120 μm in length is necessary in order to obtain source and drain electrodes with the minimized resistance.
TL;DR: In this article, the results of a study of laser-annealed Au-Ge ohmic contacts to GaAs are presented, and the specific contact resistivity was observed to decrease with increasing laser energy density while the grain size of the polycrystalline microstructure increased.
Abstract: The results of a study of laser-annealed Au-Ge ohmic contacts to GaAs are presented. The specific contact resistivity was observed to decrease with increasing laser energy density while the grain size of the polycrystalline microstructure (as observed by transmission electron microscopy) increased. At higher energy densities, both parameters were found to remain constant within the experimental conditions used. Transmission electron micrographs, and sputtering Auger electron spectroscopic data showing Ga, As, and Ge redistribution within the Au-Ge film are also presented.
TL;DR: In this article, a quantitative investigation of the constraints on dc operation of GaInAsP stripe-geometry lasers at room temperature and above has been made, and sets of theoretical curves have been generated that allow expected de thresholds to be determined from the value of the pulsed threshold.
Abstract: A quantitative investigation of the constraints on dc operation of GaInAsP stripe-geometry lasers at room temperature and above has been made. Laser pulse threshold current, its temperature sensitivity, electrical series resistance, and the thermal resistance of the bonded device are critical parameters in this respect. Sets of theoretical curves have been generated that allow expected de thresholds to be determined from the value of the pulsed threshold. Experimental results confirm the accuracy of the expressions. For GaInAsP lasers, the low values of T 0 reported in the literature (47-80 K) imply that both electrical series resistance and thermal resistance must be minimized in order to obtain stable dc operation over a reasonable temperature range in conventional oxide or proton isolated stripe structures. Both parameters are calculated theoretically for a range of structures. The calculations show that thermal runaway is sensitive to electrical resistance in the range 1-10 \Omega this suggests an area where improvements are possible. To this end, the use of tunneling Schottky contacts to a ternary InGaAs p-capping layer has been developed to minimize contact resistance.
TL;DR: In this article, the AuZn system was used, resulting in a contact resistance of 5×10−3 Ω cm2 for 1.2×1016 cm−3 p•InP.
Abstract: Both n‐ and p‐type Ge films have been grown on InP substrates by vacuum‐vapor‐deposition. Contact resistivity for n‐Ge films on 1.3×1016 cm−3 n‐InP was measured to be 10−5 Ω cm2. On the other hand, p‐Ge films on lightly doped p‐InP resulted in poor ohmic behavior. For contacts to lightly doped p‐InP, the AuZn system was used, resulting in a contact resistance of 5×10−3 Ω cm2 for 1.2×1016 cm−3 p‐InP. The sintering behavior of this AuZn contact to InP and the doping characteristics of deposited Ge films have been correlated with Auger measurements of similarly heat‐treated InP surfaces.
TL;DR: In this article, the resistivities of TiN and Ti-TiN contacts on a shallow junction solar-cell-type silicon substrate have been determined by the method of the transmission line model.
TL;DR: A comparison of contact resistivity for platinum silicide contacts and sputtered chromium contacts to heavily doped n and p silicon has been done, by a method which is suitable for contacts on a highly conductive surface layer on a less conductive base material as discussed by the authors.
Abstract: A comparison of contact resistivity for platinum silicide contacts and sputtered chromium contacts to heavily doped n and p silicon has been done, by a method which is suitable for contacts on a highly conductive surface layer on a less conductive base material. Good statistics was obtained by using 50 separate structures on each wafer. The results showed less spreading and lower specific contact resistance for PtSi contacts on both n+ and p+-Si, than for Cr contacts which on p+ showed a non-ohmic behaviour.
TL;DR: In this article, Auger depth profiling (ADP), transmission electron microscopy (TEM) and measurement of the contact resistance at temperatures ranging from 25 to 418°C were investigated to determine the effect of grain boundaries on concomitant kinetic processes.
TL;DR: In this article, the reliability of pulsed electron-beam-alloyed AuGe/Pt ohmic contacts on GaAs has been studied and compared with thermally alloyed contacts.
Abstract: Reliability of pulsed electron‐beam‐alloyed AuGe/Pt ohmic contacts on GaAs has been studied and compared with thermally alloyed contacts. Electron‐beam‐alloyed contacts have excellent surface morphology and low contact resistance, but are not as reliable as thermally alloyed contacts; the specific contact resistance deteriorates with thermal aging at 250 °C. The degradation is explained by the interdiffusion and compound formation in the metals during aging.