Showing papers on "Capacitance published in 1973"

Efficient Capacitance Calculations for Three-Dimensional Multiconductor Systems

Abstract: The design and packaging of integrated circuits requires the calculation of capacitances for three-dimensional conductors located on parallel planes. An integral-equation (IE) computer-solution technique is presented, which provides accurate results. The solution technique minimizes computer storage requirements while maintaining calculating efficiency computation times.

The C-V characteristics of Schottky barriers on laboratory grown semiconducting diamonds

Abstract: Measurements of the differential capacitance of evaporated gold Schottky barriers on laboratory-grown, boron-doped semiconducting diamonds have been obtained for the first time as functions of reverse-bias voltage, frequency, and temperature The data are analyzed on the basis of a model which includes the effects of long time constants for hole capture from the deep (boron) level, as well as previously unobserved effects due to the series resistance of the bulk The barrier height at 300°K is found to be 1·73 ± 1·10 eV , in good agreement with the ‘one-third band gap’ value of Mead and Spitzer Excellent correlation is found between optical transmission measurements and the C-V analysis for the uncompensated boron concentration, indicating that all of the optically observable dopant is electrically active By fitting the model with two adjustable parameters at room temperature, good agreement is obtained between measured and calculated capacitance over two and a half decades as a function of temperature The analysis indicates that the activation energy of the acceptor level is 0·26–0·37 eV for the samples studied, while the associated capture cross-sections are 0·9–2·0 × 10 −17 cm 2

Schottky-barrier capacitance measurements for deep level impurity determination

Abstract: The time dependence of a Schottky-barrier capacitance due to thermal excitation of trapping centres has been studied. An expression for the junction capacitance is derived which is not restricted to any special range of reverse bias nor to a special relation between shallow and deep impurity concentration. The concentration ratio of shallow to deep centres is calculated from the values of the capacitance at zero and infinite time. From a capacitance vs. time plot the trap emission rate for electrons e n is obtained. Their energetic level within the forbidden band-gap is determined from the temperature dependence of e n as well as from the capacitance-time variation. Experimental studies which do confirm the calculations were carried out on gold contacts on oxygen-doped n -type GaAs. Representative results of the investigated samples were: shallow donor density 3 × 10 15 cm −3 , trap density 9·8 × 10 15 cm −3 , electron emission rate 6 × 10 −2 sec −1 , energetic level 0·68 eV and capture cross section 7 × 10 −16 cm 2 .

Pressure-sensing capacitor

Abstract: A capacitance type pressure transducer which avoids errors due to changes in temperature has a pressure responsive capacitor and a fixed reference capacitor connected in a circuit to provide an output proportional to the ratio of the capacitances as a function of pressure. Since both capacitors are subjected to the same temperature changes any variations in capacitance due to temperature is cancelled out in the ratio.

Occupancy detector apparatus for automotive safety system

Abstract: Occupancy detector apparatus including a metallic electrode disposed to cooperate with the body of an automobile to form an occupant sensing capacitor, a reference capacitor, and an IC capacitance detecting and logic generating circuit. The IC includes a current source for continuously supplying charging current to the sensing capacitor and the reference capacitor, a first charge detecting circuit for detecting the charge on the sensing capacitor, a second charge detecting circuit for detecting the charge on the reference capacitor, and a comparator circuit for comparing the output signals developed by the first and second charge detecting circuits and for developing a logic output commensurate with the relationship between the capacitances of the sensing capacitor and the reference capacitor.

Current-voltage characteristics and capacitance of single grain boundaries in semiconducting BaTiO3 ceramics

Abstract: Specimens were prepared of doped ceramic barium titanate in the form of bars which, between their metallized ends, contained only one high-resistance grain boundary running across the entire cross-section. The measurements covered the differential capacitance of these individual grain boundaries, under bias, and their d.c. current-voltage characteristics. The results can be described quite well by a model in which a layer of a second phase present between the barium titanate grains is assumed to possess, firstly, acceptor character and, secondly, a dependence of its permittivity on the temperature and the electric field strength.

Theory of dynamic charge current and capacitance characteristics in MIS systems containing distributed surface traps

Abstract: Theoretical studies have been made on the dynamic characteristics of the metal-insulator-semiconductor (MIS) capacitor containing distributed surface traps. It has been shown that when the surface traps are in dynamic equilibrium with the voltage ramp, the device exhibits steady-state charge, current and capacitance characteristics. When the surface traps are out of equilibrium with the voltage ramp, then the emission of trapped charge is a function of time only and not of voltage. Under such conditions, the characteristics are considered to be non-steady-state in nature. In the steady state, the emission of electrons from a continuum of surface traps accounts for the reduction in the slopes of the C–V curves from the ideal ones. Kinks are manifested when the traps just empty the last of their electrons. In the non-steady state, electron emission can be described by the non-steady-state (time-dependent) occupancy function derived herein, which is shown to be similar in shape to the Fermi function. This means that electron emission takes place from a narrow band of energy positioned near the uppermost-filled traps. Hysteresis effects are manifested in the C–V characteristics due to the non-steady-state emission of trapped charge. At the transition from the steady state to the non-steady state and vice versa, kinks are exhibited in the charge and capacitance characteristics, while step changes in current components are also predicted. The physical processes involved have been stressed and closed-form expressions have been obtained for the charge, current and capacitance in terms of the trapping parameters, sweep-rate and temperature.

Device for detecting corona discharge in an enclosed electric device

Abstract: In an enclosed electric device in which a conductor to be charged with a voltage is supported by an insulation support in its enclosing metal case, an electrode is disposed on or in the insulation support so as to provide a first static capacitance with respect to the conductor and a second static capacitance with respect to the metal case. A corona discharge detector is connected between the electrode and the metal case and adapted to detect, with the first static capacitance used as a coupling capacitor, a corona discharge occurring from the conductor and the insulation support.

System for detecting wet and icy surface conditions

Abstract: A system for detecting wet and icy conditions on the surface of highways, airport runways and the like. A first capacitor is positioned on a surface the condition of which is being detected. This capacitor has first and second spaced-apart electrodes which are positioned substantially coplanar with the surface and exposed to atmospheric precipitation which affects the capacitor''s dielectric and capacitance. A second capacitor having first and second spaced-apart electrodes is positioned so as not to be exposed to atmospheric precipitation. Respective out-ofphase time-varying signals are applied to the first electrodes of said capacitors and the second electrodes are commonly connected. The system further includes a conductivity sensor having first and second spaced-apart electrodes exposed to atmospheric precipitation which affects the sensor''s resistance, a sensor circuit which supplies an output voltage the magnitude of which is a function of the resistance of the sensor, and a logic circuit responsive to any signal coupled to the second electrodes of the capacitors reaching a predetermined precipitation threshold magnitude and to the output voltage of the sensor circuit reaching a predetermined ice threshold magnitude to provide an output which indicates an icy surface condition.

System for detecting wet and icy surface conditions

Abstract: A system for detecting wet and icy conditions on the surface of highways, airport runways and the like. A first capacitor is positioned on a surface the condition of which is being detected. This capacitor has first and second spaced-apart electrodes which are positioned substantially coplanar with the surface and exposed to atmospheric precipitation which affects the capacitor''s dielectric and capacitance. A second capacitor having first and second spaced-apart electrodes is positioned so as not to be exposed to atmospheric precipitation. Respective out-ofphase time-varying signals are applied to the first electrodes of said capacitors and the second electrodes are commonly connected. Means for indicating when the magnitude of a signal coupled to the commonly connected second electrodes reaches a predetermined magnitude provides an indication of the presence of any atmospheric precipitation on said surface.

A New Method for Calculating the Capacitance of a Circular Disk for Microwave Integrated Circuits (Short Papers)

Abstract: A method for calculating the capacitance of a circular disk on a dielectric substrate backed by a ground plane is presented. Hankel transforms and Galerkin's method are used to derive the expression for the capacitance. Numerical results are compared with the experimental data and good agreement is reported.

Flour confectionery oven control - using capacitance sensing for speed, position, or cycle time regulation

Abstract: A pair of equal sized capacitance sensors, together with common counter electrode is placed across or aligned circuit the output (unbalance signal) of which is amplified, rectified, opt. high pass filtered, and fed to a conventional regulator for the appropriate drive motor.

A capacitance method for measurement of film thickness in two-phase flow

Abstract: A new capacitance method is described for the measurement of local, time‐varying or steady‐state film thickness in two‐phase flow studies The method is suitable for use in simple and complex geometries, and works for either electrically nonconducting or slightly conducting fluids Test data were obtained on bubbles of different lengths rising in a circular tube filled with water Results for film thicknesses and bubble residence times showed good self‐consistency and agreement with other available data

Capacitance-voltage converter

Abstract: A capacitance-voltage converter, in which an unknown capacitance of a measured capacitor is converted to an output dc voltage indicative of the unknown capacitance. The measured capacitor is charged by a reference dc voltage. All the charge of the measured capacitor is transferred to a reference capacitor, after discharging the reference capacitor, by connecting the terminals of the measured capacitor to the input and the output of an impedance converter, which has a high-impedance input and a lowimpedance output. The reference capacitor is connected to the high-impedance input of the impedance converter. The output dc voltage is derived from the output of the impedance converter.

Theory of dynamic charge and capacitance characteristics in MIS systems containing discrete surface traps

Abstract: Theoretical studies have been made on the dynamic characteristics of the metal-insulator-semiconductor (MIS) capacitor containing discrete surface traps. It has been shown that when the surface traps are in dynamic equilibrium with the voltage ramp, the device exhibits steady-state charge and capacitance characteristics. When the surface traps are out of equilibrium with the voltage ramp, then the emission of trapped charge is a function of time only and not of voltage. Under such conditions, the characteristics are considered to be non-steady-state in nature. The emission of trapped charge in the non-steady state gives rise to a plateau or ledge in the C – V characteristics, while characteristics. The transition from the steady state to the non-steady state results in kinks in the characteristics. The physical processes involved have been stressed and simple expressions have been obtained for the charge and capacitance in terms of the trapping parameters, sweep-rate and temperature.

A Diode‐Quad Bridge Circuit for Use with Capacitance Transducers

Abstract: A new diode‐quad transducer bridge circuit has been developed which features: (1) a high output that is independent of excitation frequency and waveform; (2) a fractional capacitance (ΔC/Co) resolution of 4.4 × 10−8 at a bandwidth of 10–30 Hz; and (3) the capability of conveniently grounding the transducer. Application to a capacitive transducer for pressure measurements yielded an output resolution of 0.003% corresponding to a pressure resolution of ± 1.5 × 10−4 Torr.

Multielectrode capacitive liquid level sensing system

Abstract: A bridge circuit has in one branch a long capacitive probe and in the other branch a plurality of parallel capacitive probes of different lengths, the probes to be mounted in a storage tank. Inductors used across the respective probes function to subtract the values of capacitances equal to the value of the capacitances of the respective probes when no liquid is present in them, thereby to obtain capacitance readings indicative of only increased capacitances resulting from the presence of liquid. The outputs of the branches resulting from the presence of liquid are compared, and a control voltage is developed for application to a capacitive diode in the one branch of the bridge circuit to maintain the bridge circuit substantially balanced. The control voltage is measured to indicate the level of the liquid in the tank, and the use of a plurality of probes in the other branch extends the useable range of the curve for observable voltage changes. The effect of different densities of liquids is balanced out.

Determination of deep‐level energy and density profiles in inhomogeneous semiconductors

Abstract: A method is proposed for the determination of deep impurity levels and density profiles from C–V measurements and is demonstrated on GaAs Schottky barrier diodes. The technique involves measurements of the time dependence of the bias voltage instead of the barrier capacitance. The spatial distribution of a deep level is observed to exhibit a peak at the boundary between an epitaxial layer and the semi‐insulating substrate. This deep center is located 0.8 eV below the conduction band.

Correcting interface‐state errors in MOS doping profile determinations

Abstract: It is shown that the apparent doping profile obtained from a 1/CHF2 vs V plot (where CHF is the high‐frequency MOS capacitance and V is the voltage across the capacitor) can be corrected for interface‐state effects to obtain a more accurate doping profile. This more accurate doping density, N(w), at distance w from the semiconductor‐insulator interface is related to the uncorrected density, N0(w), obtained by neglecting interface states, by N(w)=N0(w) (1−CLF/Cox) (1−CHF/Cox)−1, where CLF is the quasistatic MOS capacitance at the voltage corresponding to the depletion width w and Cox is the oxide capacitance. This scheme is shown to provide the doping profile to within 5% accuracy for distances from three extrinsic Debye lengths out to the maximum depletion width obtainable in thermal equilibrium. Experimental verification of this method is obtained by measuring the doping profile on a single capacitor before and after bias‐temperature stress. The same doping profile is obtained in both cases despite a lar...

Method for measuring endodontic working lengths

Abstract: A method for measuring the depth of a root canal in a tooth including: (1) forming an opening in the tooth crown, (2) placing a disc-shaped electrode on mucosa adjacent the submerged tooth root, (3) inserting a probe electrode in the form of an endodontic file through the opening into the root canal, (4) measuring the capacitance across the electrodes, (5) continuing to further insert the probe electrode until the capacitance substantially increases, and (6) measuring the depth of penetration at the point the capacitance substantially increases to locate the apical foramen. The device for carrying out the method includes an oscillator set at 10 KHz and a capacitance bridge circuit connected to the oscillator. The electrodes form one arm of the bridge circuit, and a known capacitance of about 0.08 Mu f forms another arm thereof. The output of the bridge circuit is fed into a null detector so that an increase appearing on a null meter is seen when the probe electrode reaches the apical foramen.

Threshold voltage of nonuniformly doped MOS structures

Abstract: The minimum of the HF capacitance and the threshold voltage, for nonuniformly doped MOS structures, are calculated by means of an analytical model containing an adequate definition of the condition of strong surface inversion The results obtained for profiles piling up close to the surface are in excellent agreement with those obtained by a numerical integration of Poisson's equation

Capacitive pressure transducer

Abstract: Pressure responsive diaphragms, in their movement with respect to fixed plates, constitute variable capacitors. Dual diaphragms, on opposite sides of a substrate carrying the corresponding fixed plates, eliminate flexure of the substrate as a factor in the performance of the device. An electrical circuit for converting the varying capacitance to a correspondingly varying electrical signal is housed in the space between the diaphragms. The pressure transducer so formed is contained in a casing which communicates by tubing to any desired source of pressure; such pressure in the interior of the casing is imposed on the transducer. Terminals for external electrical connections are formed by screws which hold the casing members together, and which are electrically continuous with internal conductors.

Measurement of carrier-concentration profiles in epitaxial indium phosphide

Abstract: A technique is described for measuring carrier-concentration profiles of vapour-deposited epitaxial indium phosphide using the capacitance/voltage characteristics of a reverse biased metal-insulator-semiconductor diode. Profiles of layers grown on chromium and tin-doped substrates are presented. The effect of dopant type on the sharpness of electrical interfaces is discussed.