Showing papers on "Capacitance published in 1993"

Object position detector

Abstract: A proximity sensor system includes a sensor matrix array having a characteristic capacitance between horizontal and vertical conductors connected to sensor pads. The capacitance changes as a function of the proximity of an object or objects to the sensor matrix. The change in capacitance of each node in both the X and Y directions of the matrix due to the approach of an object is converted to a set of voltages in the X and Y directions. These voltages are processed by analog circuitry to develop electrical signals representative of the centroid of the profile of the object, i.e, its position in the X and Y dimensions. The profile of position may also be integrated to provide Z-axis (pressure) information.

Large suspended inductors on silicon and their use in a 2- mu m CMOS RF amplifier

Abstract: Large spiral inductors encased in oxide over silicon are shown to operate beyond the UHF band when the capacitance and loss resistance are greatly reduced by selective removal of the underlying substrate. Using a 100-nH inductor whose self-resonance lies at 3 GHz, a balanced tuned amplifier with a gain of 14 dB centered at 770 MHz has been implemented in a standard digital 2- mu m CMOS IC process. The core amplifier noise figure is 6 dB, and the power dissipation is 7 mW for a 3-V supply. >

Capacitance, admittance, and rectification properties of small conductors

Abstract: We formulate microscopic expressions for capacitances, admittances and the rectification properties for small phase-coherent samples consisting of a number of metallic layers separated by insulators. The electric potential in such a structure is discussed with the help of characteristic functions which determine the variation of the microscopic potential inside the sample in response to an increase of the electro-chemical potential at a contact. An electrochemical capacitance matrix is derived which allows for field penetration into the conductor. We discuss the admittance matrix for conductors with nearby capacitors (gates) and analyse its magnetic field symmetry. We use the characteristic potentials to discuss the rectification properties of a conduction channel in the presence of nearby capacitors.

Frequency dependence of forward capacitance-voltage characteristics of Schottky barrier diodes

Abstract: The frequency dependence of forward capacitance-voltage characteristics of Schottky barrier diodes were investigated by considering the series resistance effect. It is seen that in presence of a series resistance, the capacitance-voltage plot exhibits a peak. The peak value of the capacitance is found to vary with series resistance, interface state density and the frequency of the a.c. signal. The effect of series resistance on the capacitance is found appreciable at higher frequencies when capacitance decreases rapidly with frequency. On the other hand, the conductance of the diode increases with frequency in the high frequency limit. Such a variation in conductance limits the use of well known conductance technique to determine interface state density.

Capacitance requirements of self-excited induction generators

Abstract: A simple method for computing the minimum value of capacitance, C min. required for initiating voltage build-up in a three-phase self-excited induction generator (SEIG) is presented. Based on the steady-state equivalent circuit model, a consideration of the circuit conductances yields a sixth-degree polynomial in the per-unit frequency. The polynomial can be solved for real roots, which enables the value of C/sub min/ to be calculated. Critical values of load impedance and speed, below which the machine fails to self-excite irrespective of the capacitance used, are found to exist. Closed form solutions for C/sub min/ are derived for no-load and inductive loads. Using the same numerical approach, an interative procedure is developed for predicting the capacitance required for maintaining the terminal voltage at a preset value when the generator is supplying load. Experimental results obtained on a 2 kW induction machine confirm the feasibility and accuracy of the proposed methods. >

Defibrillator Waveform Generator for Generating Waveform of Long Duration

Abstract: An implantable defibrillator/cardioverter which generates a biphasic waveform having a duration of at least 15-80 msec and a small "tilt" between the leading edge and trailing edge voltages of each phase. In one embodiment, two capacitors are connected in parallel to create an effectively large capacitance to generate a slowly decaying waveform. In another embodiment, a high capacitance bipolar capacitor is used, which capacitance is at least 200 microFarads.

Characterization of a tunable thin film microwave YBa2Cu3O7−x/SrTiO3 coplanar capacitor

Abstract: We have fabricated and characterized electrically tunable high temperature superconductor coplanar microstrip resonators incorporating tunable SrTiO3 ferroelectric thin films. The low frequency capacitance of the SrTiO3 capacitor is measured directly. High frequency capacitance and loss information are extracted from the observed resonances and compared with the low frequency data. Hysteresis loops display an onset of ferroelectricity at 160 K. The spontaneous charge and coercive voltage (at 10 kHz) as a function of temperature are extracted from these loops.

Accurate transmission line characterization

Abstract: A method for the characterization of transmission lines fabricated on lossy or dispersive dielectrics is introduced. The method, which is more accurate than conventional techniques, is used to examine the resistance, inductance, capacitance, and conductance per unit length of coplanar waveguide transmission lines fabricated on lossy silicon substrates. >

Battery state of charge determination with plural periodic measurements to determine its internal impedance and geometric capacitance

Abstract: A method and apparatus for measuring the depletion level (depth of discharge) of a lithium-iodine battery in an implantable medical device. A first set of measurements are made to determine the internal impedance of the battery, and a second set of measurements are made to determine the geometric capacitance of the battery, which has been found to correlate closely to the depth of discharge of the battery. The measurements are all made while the pacemaker is first temporarily decoupled from the medical device circuitry. The first measurements are made during a time window following a known change in resistive load across the terminals of the battery, and are capable of being correlated with 1-kHz qualification testing data made on the battery at the time of manufacture. The second measurements are made when the known load is periodically coupled and decoupled to the terminals of the battery at a rate of 80-kHz. The resulting data can be used to monitor depth of discharge throughout the operable life of the battery.

Oscillations of low-current electrical discharges between parallel-plane electrodes. III. Models.

Abstract: Simple models are developed to describe the results of measurements of the oscillatory and negative differential resistance properties of low- to moderate-current discharges in parallel-plane geometry. The time-dependent model assumes that the ion transit time is fixed and is short compared to the times of interest, that electrons are produced at the cathode only by ions, and that space-charge distortion of the electric field is small but not negligible. Illustrative numerical solutions are given for large voltage and current changes and analytic solutions for the time dependence of current and voltage are obtained in the small-signal limit. The small-signal results include the frequency and damping constants for decaying oscillations following a voltage change or following the injection of photoelectrons. The conditions for underdamped, overdamped, and self-sustained or growing oscillations are obtained. A previously developed steady-state, nonequilibrium model for low-pressure hydrogen discharges that includes the effects of space-charge distortion of the electric field on the yield of electrons at the cathode is used to obtain the negative differential resistance. Analytic expressions for the differential resistance and capacitance are developed using the steady-state, local-equilibrium model for electron and ion motion and a first-order perturbation treatment of space-charge electric fields. These models generally show good agreement with data from dc and pulsed discharge experiments presented in the accompanying papers.

Improved equivalent circuit for determination of MESFET and HEMT parasitic capacitances from "Coldfet" measurements

Abstract: An improved equivalent circuit for MESFET and HEMT devices under zero drain bias pinched-off conditions is proposed. Parasitic gate and drain capacitances evaluated from low-frequency Y parameters using this circuit are approximately equal under conditions where equality would be expected from bond pad geometry considerations. In contrast, the previously used circuit considerably overestimates parasitic drain capacitance. >

Microwave Characteristics of TiO2-Bi2O3 Dielectric Resonator

Abstract: The microwave characteristics of the binary-system TiO2-Bi2O3 ceramics, which is widely known to exhibit a comparatively high dielectric constant in the lower-frequency band, are investigated from a new standpoint It is shown in this article that the composition of 0919TiO2-0081Bi2O3 has a high dielectric constant (er=80), high Q (1800 at 5 GHz) and low temperature coefficient of resonant frequency (τf=+21 ppm/°C) From the X-ray diffraction and X-ray microanalysis, it is indicated that the crystal structure of this material is composed of two phases, TiO2 and Bi2Ti4O11, which possess a high er with a negative temperature coefficient and a high er with a positive temperature coefficient, respectively The measurements of linear thermal expansion and temperature coefficient of capacitance are also carried out in order to study the behavior of temperature compensation in this system

Electrical conductivity measurements using microfabricated interdigitated electrodes

Abstract: Microfabricated interdigitated electrode arrays were constructed and evaluated for use as miniature conductivity cells. The arrays were 2×3 mm in size and had digits ranging in size from 10 to 80 μm. The complex electrical impedance of the devices was measured at frequencies spanning from 100 to 100 kHz in solutions with resistivities ranging from 10 to 67 000 Ω/cm. An electromagnetic field model of the interdigitated electrode geometry was used to calculate cell constants. The resulting values ranged from 0.07 to 0.55 cm -1 , and they agreed well with the experimental data. The frequency dependence of the complex electrical impedance could be represented by an equivalent circuit incorporating an interfacial impedance consisting of a double-layer capacitance in series with a Warburg-type diffusion impedance

Field‐emitter‐array development for high‐frequency operation

Abstract: Power amplification at high frequencies is one of many applications under investigation using vacuum microelectronics technology. The results of an ongoing program to develop a gigahertz amplifier using Spindt‐type field‐emitter arrays are reported. The maximum frequency at which a field‐emission source in the form of a Spindt‐type cathode array can be operated is determined by the capacitance of the structure and the transconductance of the array. It has been shown that by fabricating arrays with high emitter‐tip packing densities and small total areas it should be possible to achieve operation in the gigahertz range. Structures having a capacitance in the range of 0.1 pF have been fabricated, and total emission currents of 25 mA with current densities of 1000 A/cm2 have been demonstrated with a 0.1 pF structure having 625 emitter tips (40 μA/tip). The transconductance under these operating conditions was 500 μs or 0.8 μS/tip. Simultaneous experiments with our standard low‐frequency Spindt‐type cathode geometry have shown that average emitter tip loadings of 200 μA/tip and transconductances of 5 μS/tip can be achieved. A 625‐tip, 0.1‐pF array with transconductance of 5 μS/tip would have a cutoff frequency of about 5 GHz. The factors determining the capacitance and transconductance of the device and methods for improving performance are discussed.

Electronic energy spectrum and the concept of capacitance in quantum dots.

Abstract: The chemical potential and the capacitance of a model quantum dot have been computed, including contributions of exchange and correlation in the limit of 0 K temperature. The Schro\ifmmode\ddot\else\textasciidieresis\fi{}dinger equation has been solved self-consistently, taking into account the electron-electron Coulomb interaction and many-body effects within the framework of density-functional theory. We have also studied the effect of conducting backgates and of nearby electrodes using the method of images. Depending on the size of the dot, we derive a prevalance of either the quantization energy or the electrostatic energy: there is a smooth transition from predominant quantum effects for small dots to classical capacitance behavior for large dots. Our simulation reproduces characteristic effects that have been experimentally observed, such as the capacitance increase for increasing electron numbers and irregularities in the chemical potential values when randomly distributed charged impurities are present.

Static Relative Permittivity of Carbon Dioxide and Nitrous Oxide up to 30 MPa

Abstract: The static relative permittivity er of carbon dioxide and nitrous oxide has been measured in a temperature range from 273.15 to 353.15 K at pressures up to 30 MPa. The measurements were performed by means of a transformer ratio-arm bridge with a three-terminal capacitance cell installed in a pressure vessel at frequencies between 10 to 50 kHz. The newly-designed capacitance cell and pressure apparatus are described. Experimental er-values obtained for the two fluids were estimated to be accurate to within ±0.02%. The critical relative permittivity er,C, evaluated from the er-values of coexisting saturated vapor and saturated liquid, was 1.267±0.001 for carbon dioxide and 1.288±0.003 for nitrous oxide. The density dependence of the er-values can be expressed by a quadratic function of density, independent of temperature. The er-data for each fluid were combined with available densities from the literature to calculate the molar polarization Pm given by the Clausius-Mossotti (CM) equation. Some consideration is given for the coefficients of the dielectric virial equation, i.e., the expansion of the CM equation in powers of density.

Sensor for articles such as wafers on end effector

Abstract: The presence of an article at a specified location is detected by measuring a change in capacitance which is caused by the placement of the article at the specified location. The device used for this measurement includes an oscillator the frequency whereof is rendered highly sensitive to the capacitance being measured by structure which includes a triaxial cable and by electrical circuitry which includes a voltage follower circuit.

A newly designed planar stacked capacitor cell with high dielectric constant film for 256 Mbit DRAM

Abstract: Thin film of (Ba/sub 0.75/Sr/sub 0.25/)TiO/sub 3/ with equivalent SiO/sub 2/ thickness of 0.47 nm has been developed for capacitor dielectric film of 256 Mbit DRAM. A novel cell design named FOGOS (FOlded Global and Open Segment bit-line cell) structure is also proposed for 256 Mbit DRAM. By combining high dielectric constant film and FOGOS design, we have succeeded in making a practical and integrated cell that has sufficient cell capacitance with planar stacked capacitor, small bitline parasitic capacitance and large lithographic tolerance of alignment and DOF. 0.72 /spl mu/m/sup 2/ cell size based on 0.25 /spl mu/m process technology is realized. >

Conductor capacitance reduction in integrated circuits

Abstract: A passive semiconductor structure for reduction of the mutual capacitance between parallel conductors, with two parallel conductors separated from a substrate by a first dielectric layer and covered by a second dielectric layer. The second dielectric layer having a cavity formed between these conductors, whereby the effective relative dielectric constant of the medium between these conductors is reduced.

Double-driven shield capacitive type proximity sensor

Abstract: A capacity type proximity sensor comprised of a capacitance type sensor, a capacitance type reference, and two independent and mutually opposing driven shields respectively adjacent the sensor and reference and which are coupled in an electrical bridge circuit configuration and driven by a single frequency crystal controlled oscillator. The bridge circuit additionally includes a pair of fixed electrical impedance elements which form adjacent arms of the bridge and which comprise either a pair of precision resistances or capacitors. Detection of bridge unbalance provides an indication of the mutual proximity between an object and the sensor. Drift compensation is also utilized to improve performance and thus increase sensor range and sensitivity.

Decoupling capacitor effects on switching noise

Abstract: The experimental procedures and test vehicles used for the characterization of the decoupling capacitor efficiency in reducing the power supply differential switching noise of the multichip-module (MCM) package structure employed in the IBM ES/9000 system are described. The experimental results are summarized for various switching elements. It is demonstrated that careful design of the test vehicles, tester systems, and probes makes the accurate measurement of Delta-1 noise feasible. Experimental results on the BOBCAT tester show that the decoupling capacitor efficiency in reducing the peak of the differential Delta-1 noise is 50-67%. This efficiency can be increased by reducing the effective inductance in the decoupling capacitor current return path. >

Method for manufacturing a semiconductor memory device having a capacitor with increased effective area

Abstract: A storage electrode of a capacitor of a semiconductor memory device and a method for manufacturing the same are disclosed. A first electrode of the capacitor comprises a main electrode having a plurality of microtrenches and micropillars formed therein, an outer wall surrounding the microtrenches and micropillars, a granular silicon layer formed on an outer sidewall of the outer wall, and a column electrode supporting the main electrode and electrically connecting the main electrode to a source region of a transistor of the semiconductor device. The first electrode preferably has a horizontally fin-structured auxiliary electrode formed underneath the main electrode and electrically connected to the column electrode of the first electrode. The capacitor may be formed by using an etching end-point detection layer and an HSG polysilicon layer. The effective surface area of the storage electrode of a capacitor is increased to thereby obtain adequate cell capacitance. Also, uniform shapes of the storage electrodes are preferably obtained to thereby attain uniform cell capacitance.

Capacitive sensing system and technique

Abstract: An arrangement senses a liquid level by monitoring the peak capacitance formed between a probe and the liquid as the probe approaches or departs from the liquid. In an automated system, a computer controls the position of a pipette probe for aspirating or dispensing liquid in the vessel. The charge developed via the capacitance on the probe is coupled to a capacitive sensor circuit which provides a peak detector with an amplified signal representing the peak capacitance between the probe and the liquid. This amplified signal is detected by a peak-capacitance discrimination circuit, the output of which is monitored by the computer for determining the precise position of the probe with respect to the liquid surface level. Other aspects of the present invention include a negative-static elimination circuit coupled to the output of a detector latch and a positive-static elimination circuit coupled to the input of the detector latch.

A spacing algorithm for performance enhancement and cross-talk reduction

Abstract: With the shrinking of feature size on silicon, the coupled capacitance between adjacent wires is contributing a significant factor to the interconnect delay, which already dominates the circuit performance. In the near future coupled capacitance could contribute as much as 50-75% to the interconnect delay which has been largely ignored by performance-oriented layout tools. Given a routed design, this work minimizes the delay and the peak cross-talk by re-adjusting the space between interconnects. It can reduce the circuit delay significantly and, in addition, reduce the peak cross-talk problem. An efficient technique based on the network simplex algorithm is used to solve the problem in the paradigm of compaction.

Neuron transistor: Electrical transfer function measured by the patch-clamp technique

Abstract: Leech neurons are attached to metal-free field-effect transistors in electrolyte. The voltage in a neuron is controlled through a pipette fused to its membrane. Gaussian transients and ac voltages are applied. The response of the source-drain current is measured. Two types of neuron-transistor couplings are observed. (A) Efficient coupling above 100 Hz with a phase shift of 90\ifmmode^\circ\else\textdegree\fi{}. (B) Efficient coupling from 0.1--1000 Hz without a phase shift. The responses are described by a circuit made of capacitance and resistance of the membrane, by the gate capacitance and by the resistance of the junction.

Methods and circuits for measuring the conductivity of solutions

Abstract: Improved circuits for measuring the conductivity of a solution confined between two electrodes in a cell compensate for series capacitance and parallel capacitance between the electrodes. A bipolar square-wave signal is applied to the cell. In one embodiment, the current through the cell is measured by an op-amp in current-to-voltage converter configuration. A feedback resistance employed with the op-amp in a feedback loop is controlled to a low value to ensure that the parallel capacitance is fully charged during an initial portion of each half-cycle of the drive signal. The feedback resistance is then selected so that the gain of the feedback loop is responsive to the range of the resistivity of the solution, and the measurement is made. In a further embodiment, charge proportional to the current through the cell is integrated across the op-amp, and the rate of charge is measured by measuring the time required to integrate the current to a predetermined level, and used to determine the resistivity of the solution. In this embodiment, the parallel capacitance is fully charged before each integration period begins. The voltage developed across the series capacitance is constant and can be compensated mathematically.

Method of making a semiconductor integrated circuit device having a capacitor with a porous surface of an electrode

Abstract: A capacitor incorporated in a semiconductor integrated circuit device is expected to have a large amount of capacitance without increase of the occupation area, and has a lower electrode increased in surface area by using a roughening technique selected from the group consisting of an anodizing technique, an anodic oxidation, a wet etching and a dry etching so that a surface of the lower electrode becomes porous, thereby increasing the capacitance.

Capacitive electrode system for detecting open solder joints in printed circuit assemblies

Abstract: Disclosed is a system that determines whether input and output leads of semiconductor components are present and properly soldered to a printed circuit board. The system includes a signal source which is connected to a wiring trace on the printed circuit board, which is soldered to the lead being tested. A capacitive test probe is placed on top of the component and connected to a capacitance measuring device. The signal source signal is capacitively coupled through the lead of the integrated circuit package being tested to the capacitive test probe, so if a predetermined capacitance is measured by the capacitance measuring device, the lead is connected to the circuit assembly. As the capacitances being measured are small, the capacitive test probe may include an amplifier, a shield or a buffer circuit to reduce stray capacitance.

Processing and microwave characterization of multilevel interconnects using benzocyclobutene dielectric

Abstract: Interconnection density is one of the most significant factors affecting cost, performance, and reliability of integrated circuits (ICs) and multichip modules (MCMs). In this paper, high density multilayer interconnect structures were fabricated using gold metallization and polymer interlayer dielectric. A number of polymers were investigated and benzocyclobutene (BCB) was selected for its electrical, mechanical, and thermal properties. A design of experiments was carried out to optimize plasma etching of vias in BCB. All metal depositions were done by lift-off techniques. A microwave characterization layout was designed to evaluate microstrip transmission lines, transmission line cross-overs, and multilevel spiral inductors. Two layers of metal separated by a layer of BCB were processed on a glass wafer. RF-on-wafer measurements were carried out at frequencies from 0.1 to 20 GHz. Equivalent circuit models fitted to the experimental data were used to derive the effective dielectric constant and characteristic impedance of the transmission lines, cross-over capacitance, and inductance and Q-factor for the multilevel spiral inductors. >