Showing papers on "Capacitance published in 1971"

Characterization of low 1/f noise in MOS transistors

Abstract: By careful processing MOS transistors have been fabricated with a low value of the interface states density (2 × 1010/cm2eV). Consequently the 1/f noise in these devices is low and in the same order of magnitude as for junction FETs. The experimental values of the equivalent noise voltage and the equivalent noise current are compared to an expression derived from straight physical arguments. From the comparison it is concluded that the noise equivalent voltage in saturated operation is proportional to the effective gate voltage, the interface state density, and inversely proportional to the gate input capacitance. Moreover, it is concluded that a proper heat treatment not only reduces the number of states but also removes the near bandedge peaks, which usually appear in the trap distribution function.

The impedance of stainless-steel electrodes.

Abstract: The resistive and capacitive properties of stainless-steel electrodes in contact with saline solutions of various concentrations were investigated over a frequency range extending from 20 to 10 kHz by using a variable-length conductivity cell. With a low current density, the series-equivalent resistance and capacitance of a single electrode-electrolyte interface were found to vary almost inversely as the square root of frequency. In the frequency range studied, it was found that the reactance was very nearly equal to the resistance and both varied almost inversely as the square root of the frequency, verifying Warburg's postulate. When current density was increased, resistance decreased and capacitance increased at all frequencies studied; the change in each was most apparent in the low frequency region. As a consequence, it can be stated that the impedance of an electrode-electrolyte interface decreases with increasing current density.

Transition region capacitance of diffused p-n junctions

Abstract: The classical capacitance-voltage relations based on abrupt space-charge edge approximations, while adequate at large reverse bias, do not adequately describe the capacitance near zero bias. This paper presents explicit capacitance-voltage relations valid near zero bias for linearly graded and exponential-constant profiles. For linearly graded junctions, the intercept in a 1/C3versus voltage plot is shown to be well approximated by the "gradient voltage" defined by V g = 2/3 kT/q ln a2ekT/q/8qn i 3. Also presented is an accurate numerical technique for machine computation of the transition region capacitance for any doping profile. Explicit relations obtained by dimensional considerations and curve fitting on numerical solutions are free of singularities, hence useful in computer-aided device design and doping profile determination.

Effect of noise on the current--voltage characteristics of a josephson junction.

Abstract: The effect of noise on the current‐voltage characteristic of a Josephson junction is investigated (1) when the temperature is near the transition temperature of the superconductors and (2) when the junction is driven by an external signal. In case (1) the noise source is the quasiparticle tunneling current but in case (2) there is in addition the noise arising from the finite linewidth of the external signal. This latter noise source is shown to dominate when the junction is operating at high harmonics. We treat the problem in the limits of small and large capacitance and obtain a criterion to determine under what circumstances each limit applies. A solution that includes a first‐order correction due to a finite capacitance is given. In the limit of large capacitance the existence and lifetime of hysteresis curves are discussed.

Specific adsorption of fluoride ions on mercury and the structure of the mercury/solutions interface

Abstract: The specific adsorption of fluoride ion on mercury has been studied at two temperatures. The unusual adsorption isotherm of the fluoride ion has been analyzed in terms of the equilibrium conditions prevailing across the double layer; a Freundlich-type isotherm describes the surface pressure of the adsorbed ionic film. The inner layer capacitance has been analyzed and its various components calculated, and from the variations of the inner layer capacitance at constant amount of adsorbed charge, the inner layer capacitance in the absence of adsorption has been evaluated. The anodic hump in the capacitance of fluoride solutions is due mainly to the adsorption of F– ions, and not to adsorbed solvent reorientation. The adsorption of SiF2–6 does not lead to a large increase in the double-layer capacitance at anodic potentials.

A Low Temperature Glass‐Ceramic Capacitance Thermometer

Abstract: Dielectric measurements are reported on capacitance thermometers based on SrTiO3 crystallized from glass at 1100 and 1200°C. Multilayer experimental units, approximately 5×2×1 mm, were fabricated using pilot plant facilities and measured from 1.7 to 300 K. If both the capacitance and loss tangent are measured, the range of the 1100°C crystallized thermometer is from at least 1.7 to 300 K. For capacitance measurement alone, the thermometer range is below 72 K, and in this range the capacitance varies smoothly and monotonically with temperature, becoming linear below 5.2 K. The sensitivity is largest in this linear region and averages 250 pF·K−1 for the 1100°C crystallized thermometers. The self‐heating at 4.2 K is about 70 pW (5 kHz, 7 mV) and decreases with decreasing temperature. The effect of a magnetic field on the thermometer was measured in an open Dewar of liquid helium at four frequencies in fields up to 80 kG. The measured changes were ≤±1 mK and are interpreted as fluctuations in the bath temperature rather than an intrinsic magnetocapacitance effect. The response time between 4.2 and 300 K is at least 70 K·sec−1. The main disadvantage of the thermometer is a transient (∼30 min) capacitance instability which is equivalent to a ≤30 mK change before stabilization. Once stabilized, the thermometer repeats to about ±2 mK when compared to a germanium thermometer, and repeats to ±13 mK on cyclically plunging into liquid helium (15 cycles) in the unstabilized case. This instability is apparently due to helium migration into the unencapsulated sensor body. The polar properties of glass crystallized SrTiO3, on which the thermometer is based, are briefly discussed, and comparisons are made with two other capacitance thermometers reported in the literature.

Surface-state density and surface potential in MIS capacitors by surface photovoltage measurements. I

Abstract: A simple method is described for the measurement of surface-state density and surface potential in a MIS capacitor. It is similar in principle to the low frequency capacitance method in so far as a dc relationship is established between the surface potential and the voltage applied to the gate electrode. This is achieved by measuring the saturation surface photovoltage. The method differs from the low frequency capacitance method in that it measures the surface potential directly, requiring no additive constant. Experimental results are presented which agree well with those obtained by the low frequency capacitance method. The present method is complementary to a second method to be described by Lam and Rhoderick (companion paper) in that the surface-state density measurable by this first method has a lower limit while that by the second method has an upper limit, the two overlapping at the value of the space-charge capacitance.

Calculation of Capacitance Coefficients for a System of Irregular Finite Conductors on a Dielectric Sheet

Abstract: The capacitance coefficients for a system of irregular finite conductors on a dielectric sheet are considered. There are two parts to the Green's function-integral equation approach considered herein: the first deals with a derivation of Green's functions for a desired mathematical model; the second solves the integral equation by a discretization procedure in which a solution for a large number of unknowns is required-a significant limitation. This approach, however, allows treatment of rather complex finite geometric configurations that are useful in the design of modern thin-film circuits. An integral representation of the Green's functions for the desired mathematical model is presented in which ground planes are assumed at finite distances from the dielectric sheet. However, in this paper, final results are obtained only for the case in which ground planes are at infinity. Numerical results are presented for some typical multiconductor systems. For the case of a two-dimensional parallel strip problem, the result of the present analysis compares well with that available in the literature.

Capacitance‐Voltage Characteristics of Metal Barriers on p PbTe and p InAs: Effects of the Inversion Layer

Abstract: The dependence of the capacitance C on the voltage is derived for metal‐semiconductor barriers in which there is a strong inversion layer at the metal‐semiconductor interface, a case of interest in the study of surface effects and in applications for laser structures Experimental results for evaporated lead and tin barriers on p PbTe at 77 °K and for evaporated gold barriers on p InAs at 77 and 42 °K are presented and compared to calculations performed with the inversion layer model Both the theory and experiment show an essentially linear dependence of C−2 with voltage, as in the usual Schottky barrier, but a voltage intercept which is surprisingly dependent on band‐structure parameters, bulk carrier concentration, and temperature Reasonable quantitative agreement between the theory and experiment is obtained In all cases the presence of a strong inversion layer can be clearly established The analysis of the capacitance‐voltage data, however, gives only a lower limit to the amount of inversion present

Radio capsule oscillator circuit

Abstract: This invention relates to a Colpitts oscillator circuit for a radio capsule of the type adapted to be swallowed by a patient for investigating a condition of the gastrointestinal tract. The circuit includes a transistor as the active element and a parallel resonant LC circuit including the series combination of a variable capacitance diode and first and second capacitors, the capacitance of the second capacitor being the larger of the two in order to provide the minimum amount of positive feedback required to cause stable oscillation. The capacitance of the first capacitor, which is connected between the diode and the transistor emitter, approximates that of the diode at the lowest voltage applied to the diode by a sensor device.

Computation of Lumped Microstrip Capacities by Matrix Methods - Rectangular Sections and End Effect (Correspondence)

Abstract: The method of moments is applied to three-dimensional microstrip problems to calculate lumped (or excess) capacitance. As examples, the capacitance of open-circuited microstrip lines and the capacitance of rectangular microstrip sections are computed. The open-circuit data are basic to any three-dimensional problem. The method is a general one and can be used to compute the lumped capacitance of any microstrip discontinuity, such as bends and T junctions.

Studies of a Glass‐Ceramic Capacitance Thermometer in an Intense Magnetic Field at Low Temperatures

Abstract: The effect of an intense magnetic field on an 1100‐type capacitance thermometer (made from an SrTiO3 glass‐ceramic crystallized at 1100°C) was accurately measured at five temperatures between 1.5 and 4.2 K. At each manostatically maintained temperature, the capacitance changes were measured five times between B=0 and B=14 T, and it was found that these changes did not exceed the measurement uncertainty, ±0.3 pF≅±1 mK. Similar results were obtained on a second 1100‐type thermometer. Some suggestions are made for the use of this type of thermometer in magnetic field experiments.

Methods of and systems for measuring capacitance using a constant current charging technique

Abstract: In a constant current charging tenchique for measuring capacitance, a constant current is supplied to a capacitance to be measured and a voltage ramp is produced. Two voltage-level detectors sense the ramp. At a low level on the ramp, a first of the detectors triggers a time-interval meter which begins to count pulses from an oscillator. A second of the detectors stops the counting process when the voltage ramp reaches an upper level. The time measured by the meter is proportional to the value of the capacitance and can be used to calculate the actual value.

One transistor dynamic memory cell

Abstract: A dynamic memory storage cell requires only one field effect transistor to store binary data The data is represented in the form of stored charge utilizing the inherent metal-insulatorsemiconductor capacitance and P-N junction capacitance at the source node of the field-effect transistor An extended portion of the source diffusion in combination with overlying thin oxide and metal layers form a capacitor that further enhances charge storage A matrix of the memory cells form an extremely high density random access memory

The Calculation of Electrical Capacitance

Abstract: : The book describes methods used to calculate electrical capacitance. It contains calculation formulas, tables, and graphs necessary for determination of the capacitance of various forms of conductors.

D.C. measurement of the space charge capacitance and impurity profile beneath the gate of an MOST

Abstract: An analysis of the MOS Transistor with bias between the source and substrate has shown that when the surface is weakly inverted, the silicon space charge capacitance over a wide range of temperature and bias can be obtained from the change in gate voltage required to maintain a constant channel current. The substrate impurity profile beneath the gate oxide can then be calculated from capacitance-bias measurements. Measurements made on n -channell and p -channel transistors following the growth of a thick gate oxide indicate a segregation coefficient of ⋍ 0·3 and ⋍ 100 for boron and phosphorus respectively.

Broadband circuit for minimizing the effects of crystal shunt capacitance

Abstract: A crystal controlled oscillator circuit having broadband circuitry for balancing out the effects of the static shunt capacitance of a crystal. A broadband phase inverting network is connected across the crystal to cancel the signal flowing through the crystal as a result of capacitive coupling between the plates. The phase inverting network may include a transformer, a center tapped inductor or a broadband inductance-capacitance network. A capacitor having a capacitance value related to the value of the static shunt capacitance is used in conjunction with the phase inverting network to determine the magnitude of the phase inverted cancellation signal.

An instrument for the rapid determination of semiconductor impurity profiles

Abstract: The instrument gives an absolute measurement of impurity concentration in a semiconductor wafer as a function of depth and surface position. A matrix of Schottky barrier diodes is deposited on the surface, contact being made with each diode in turn by a small probe. The probe is fed with a dc bias voltage and a small voltage at 100 kHz, the 100 kHz current flowing in the diode being a measure of the small-signal capacitance Cx. Another small voltage, at 1 kHz, is superimposed. and the consequent depth of modulation of the 100 kHz current is a measure of dCx/dV. The impurity concentration N and the depth are known functions of Cx and dCx/dV, and the instrument does the appropriate analogue computations to provide a direct plot of lg N against depth as the dc reverse-bias voltage is carried. This paper includes a detailed discussion of the sources of error, and also presents some typical impurity profile curves which have been obtained.

LSA relaxation oscillator principles

Abstract: Oversized n-GaAs diodes operating in the LSA mode with doping-to-frequency ratios in the 1-5×105s/cm3range are investigated in circuits that contain a short-circuited high impedance transmission line foreshortened to resonate the electronic parallel capacitance of the diode. By comparing computer simulations with experiments, such diodes are shown to operate in a nonsinusoidal LSA relaxation mode which offers good efficiency, effective space-charge control, and a fast buildup of the oscillations; details of the computer program are also given. A simple analysis is developed which defines the inductive and capacitive time constants controlling the voltage waveshape and explains the frequency tuning with bias voltage and the effective space-charge control. The analysis is shown to be suitable for oscillator design purposes.

Static electric field detector

Abstract: This apparatus is used to detect the presence of static or alternating electric fields. The electric field intensity is sensed with a probe by proximity capacitance coupling. It comprises an antenna which applies any signal it detects to the input of an amplifier. The output of the amplifier is applied to the input of a threshold circuit which conducts when an input signal of greater than a prescribed value is detected. Conduction of the threshold circuit energizes an oscillator which drives indicators of various types. Once a prescribed threshold level is exceeded, display is activated. Hence, the device of this invention provides a go-no-go presentation of field intensities.

Capacitance voltage measurements on n-type InAs MOS diodes

Abstract: Capacitance voltage measurements on interface of pyrolytically deposited n-type silicon dioxide- InAs MOS diodes as function of admittance at room and 77 K temperatures

Studies of electric capacitance of membranes : II. Conformational change in a model membrane composed of a filter paper and a lipid analogue.

Abstract: The electric capacitance and conductance of a model membrane composed of a hydrophobic filter paper and a synthetic lipid analogue, i.e., dioleylphosphate, immersed in an electrolyte solution were observed with various frequencies ranging from 20 to 3×10(6) Hz. With successive increase of salt concentration in the external solution, the capacitance and conductance of the membrane increased discontinuously at a certain critical value of the external salt concentration. This variation of the capacitance and conductance of the membrane with the salt concentration was found to be reversible, and the critical value of salt concentration was independent of the adsorbed quantity of the lipid, and of the pore size of the filter paper as far as the adsorbed quantity of the dioleylphosphate was large.A theoretical analysis based on the membrane model for the filter paper-phospholipid system proposed in Part I of this series revealed that the dioleylphosphate impregnated in the filter paper changed its conformation from oil droplets or globular micelles to a number of bilayer membranes when the salt concentration reached the critical value for a given pair of electrolyte species and the membrane. The conformational change of the lipid analogue in the filter paper is discussed in connection with the ability of formation and stability of a black bilayer membrane of the dioleylphosphate.

Dynamic data storage cell

Abstract: A dynamic data storage cell is disclosed that requires only one insulated gate field effect transistor (IGFET) to store binary data. The drain of the FET is connected to a data input line and data is stored at the source node of the transistor by the inherent capacitance between the source diffusion and the substrate. The capacitance of the source electrode is enhanced by forming a heavily doped layer to underlie a portion of the source diffusion. Using the substrate as circuit ground enables the fabrication of an array of transistors for a random access memory wherein the surface area of the semiconductor chip is minimized.

Arc Extinction Phenomena in Vacuum

Abstract: Experiments have been performed to study the manner in which an arc between copper electrodes in vacuum extinguishes. In an ac circuit where current is limited to less than 1000 A peak, resistively, the extinctions are often prolonged over a period of many microseconds by successive reignitions of the arc caused by circuit‐recovery voltage. These reignitions tend to be suppressed by capacitance paralleling the discharge thus raising the current at which the arc is extingusihed. In a similar circuit where the current is limited by inductance, the extinction most often occurs at a minimum in high‐frequency oscillations of discharge current superimposed upon the 60‐Hz arc current near the end of the half‐cycle period. These oscillations occur at a frequency determined by the capacitance in parallel with the gap and the inductance of the wires used to connect the capacitors to the gap. For the inductive circuit with low values of capacitance, the oscillations are not apparent and extinction times of 10−7 to 1...

Electrolytic capacitor with separate interconnected anode bodies

Abstract: A capacitance device having improved high frequency characteristics comprising a plurality of solid tantalum capacitor units arranged in parallel with both anode and cathode connection made to strip-like terminals.

The exact low-frequency capacitance-voltage characteristics of metal-oxide-semiconductor (MOS) and semiconductor-insulator-semiconductor (SIS) structures

Abstract: Accurate low-frequency MOS (metal-oxide-semiconductor) and SIS (semiconductor-insulator-semiconductor) C-V curves are found by solving Poisson's equation in the bulk semiconductor using regions of analytic solution joined by numerical solutions of specified accuracy. The technique uses the full Fermi function for the electron, hole, and impurity bands; thus valid results can now be obtained for partially ionized impurity bands, and situations in which the valence or conduction bands are bent through the Fermi level. The calculation can be carried out for any temperature and allows for band structure in the valence and conduction bands. Surface states are incorporated at the interface and the usual low-frequency capacitance curves are obtained for the MOS device. As expected, the C-V curves in the SIS case are more complex. The n-i-n (n-type semiconductor, insulator, n-type semiconductor) device shows two depletion minima separated by a center maxima whose size is sensitive to surface-state charge. In the p-i-n device, the depletion minima can be seen separately only if the impurity concentrations of the semiconductors differ by a factor of five or more. In that case, a deep narrow minimum due to the lightly doped semiconductor can be seen superimposed on one end of a broad shallow minimum due to the heavily doped semiconductor. This work predicts an interesting high-frequency response for the n-i-n structure, namely a bell-shaped C-V curve. This type of C-V response has not been observed to date in two-terminal passive devices, and may lead to SIS applications as a new type of parametric capacitor.

Plane-parallel condenser with variable electrode-spacing for determination of electric permittivity of highly conducting liquids below 1 MHz. Part 2.—Experimental approach

Abstract: The theoretical expressions for the capacitance Cx and conductance Gx of a plane parallel-plate condenser as series expressions in negative powers of the electrode spacing, are submitted to experimental verification. Using cells, differing in the dimensions of the electrodes, the measured values of Cx and Gx verify these expressions within experimental accuracy, and that neither the influence of electrode nor edge effects can be neglected for liquids of large conductivity. A semi-empirical approach to the theoretical equations of part 1, devised to increase the accuracy for the computation of the relative electric permittivity, is also presented and tested experimentally.