Showing papers in "IEEE Circuits & Devices in 1991"

Defects tail off with six-sigma manufacturing

Abstract: A description is given of the six-sigma technique, the goal of which is to aid in the design of products that will function as intended, despite variations of 6 sigma ( sigma is the standard deviation) in their physical/operating parameters. The six-sigma metric provides a statistically defined yardstick for quantifying a product's level of quality, using process capability indices. The meaning of the indices and why they are useful are explained. The use of Shewhart statistical process control (SPC) charts is briefly discussed. The six steps in the six-sigma program are outlined. >

Optical interconnects speed interprocessor nets

Abstract: Network requirements for interprocessor applications are described, and it is shown that telephone technology is not cost-effective for data processing networks. The elements of a cost/performance-optimized, optical-interconnect technology for interprocessor networks are examined. Optoelectronic transducers, monolithic integration of functions, and high-density packaging are discussed. Future directions in optical link technology are examined. >

Switching light with light

Abstract: The basic characteristics of the light amplifying optical switch (LAOS) are explained. The LAOS, as compared to its electronic counterparts, will substantially reduce the interconnect time between components, chips, PC boards, and machines. The use of the LAOS to implement optical logic circuits with multiple input stages that invert and restore the input signal is discussed. Applications to image and signal processing are examined. Future uses are considered. >

Simulation and modeling-the macro modeling of phase locked loops for the SPICE simulator

Abstract: A modeling approach that uses no semiconductor junctions and no regenerative feedback is described. The voltage-controlled oscillator is implemented by means of a circuit producing essentially infinite ringing, and the comparator characteristics are obtained by means of an odd-order polynomial transfer function. The design of the comparator, phase detector, low-pass filter, and error amplifier are also discussed. Performance of the complete macro-model is such that 8000-point simulations, corresponding to some 150 cycles of local oscillator, can be performed in about 15 min on a platform such as the Sun 3/60, or Apollo DN4500. >

CAD latches onto new techniques for analog ICs

Abstract: Design techniques for low-power, nondigital nonmicrowave circuits are presented. The major objectives in improving analog CAD are described. The current status of CAD for analog circuits is discussed, and interesting trends are examined. An approach to CAD-compatible analog design is discussed. These designs also apply to mixed analog/digital VLSI design environments, particularly to circuits used in signal processing. >

The power of connections

Abstract: The wiring ability of multilayer interconnects is examined. It is shown why the principal force driving interconnection technology has been the computer. Measuring the flexibility of a given technology by the number of ways it allows a designer to interconnect devices to realize a particular logical function is discussed. It is shown that the ability to construct very large systems with high-density wiring stems directly from digital representation and the preservation of a given digital representation through long series of operations. The future of interconnection technology is explored. >

Semiconducting-oxide chemical sensors

Abstract: The Taguchi and thick-film forms of semiconducting metal-oxide sensors and their reproducibility and stability problems are discussed. An attempt to circumvent these problems by producing a modified thin-film sensor based on oxygen absorption rather than adsorption is described. The sensor is made with evaporated bismuth molybdate, which has a very high diffusion constant for oxygen vacancies. The combustion gas to be sensed extracts lattice oxygen from the bismuth molybdate; atmospheric oxygen restores the lattice oxygen. Because the oxygen vacancies move rapidly in the material, the bulk stoichiometry (i.e. metal/oxygen ratio) follows the surface stoichiometry and controls the resistance. Bismuth molybdate films are stable and, as prepared, are highly sensitive to alcohols. Techniques for improving selectivity are considered. The use of electronic circuitry to circumvent inherent sensor problems is examined. >

New DRAM pricing trends: the bi rule

Abstract: Long-term pricing trends are approximately quantified. This is done using the bi rule, named for its prediction that bit cost will be reduced by one half with each succeeding DRAM generation. Pricing trends have been plotted for DRAMs up to 256 K using the pi rule, which describes the trend of the average price of packaged DRAM chips as a function of time, and for 1M DRAMs using the bi rule. >

SPICE macro model for the simulation of zener diode I-V characteristics

Abstract: The problems encountered when using the existing SPICE diode model to represent the I-V characteristics of a Zener diode in the reverse region are examined. A Zener diode macro model that has accurate I-V simulation characteristics and can be easily constructed using SPICE-provided primitives is presented. The static I-V characteristics and temperature response of the diode are reviewed. The performance of the model is discussed, and its main enhancements as compared to the SPICE model are identified. >

Nonlinear optic phase conjugation

Abstract: An overview of the field of nonlinear optical phase conjugation is given. The basic properties of a phase-conjugate mirror are discussed, and examples of how this technology can be applied to the areas of high-power lasers, optical communication systems, and optical data processing (including neural networks) are presented. It is shown that the massively parallel data processing capabilities inherent in nonlinear optical interactions, coupled with their passive, all-optical nature, make this class of system potentially useful for the next generations of advanced laser systems, remote sensors, and communications systems, as well as optical data processors and network systems architectures. >

MODFETs soar to 400 GHz

Abstract: The operation of MODFETs (modulation-doped FETs) is explained. These devices now have switching delays under 5 ps, current-gain cutoff frequencies of about 250 GHz, and maximum oscillation frequencies in excess of 400 GHz. They also perform frequency division up to 26 GHz. Experimental ring oscillators, frequency dividers, static RAMs, and gate arrays are described. The microwave performance of MODFETs is discussed. >

Quantum transistors and circuits break through the barriers

Abstract: Resonant tunneling diodes and transistors, which are 'vertical' quantum devices, in which the current flows perpendicular to the layers instead of along them, are discussed. The operation of both devices is explained. Various types of resonant tunneling transistor are examined, with particular attention to multistate devices. Applications to frequency multipliers, parity generators, and analog-to-digital converters are presented. >

Micro-automating semiconductor fabrication

Abstract: Progress in automating very-small-scale mechanical processes is reviewed. The special requirements of microautomation are identified, and three applications are examined. They are positioning, electrical probing, and mechanical probing. The architecture and design of a microautomation system are described. Microsensors and microactuators are discussed. The use of magnetics technology for driving the microautomation system is reported, and a precision workspace for demonstrating a microautomation system is described. Also described are a coarse/fine positioner and a linear transport path capable of moving the fine manipulator from one precision-demanding area to another. >

Novel techniques to solve sets of coupled differential equations with SPICE

Abstract: The solution of sets of coupled differential equations using SPICE is treated. The equations are rearranged so that each of the variables appears as a current through a 1- Omega resistor, and the SPICE transient analysis option TRAN is used to invoke the DCTRAN module. This module performs the DC operating point analysis, the initial-condition of transient analysis, the DC transfer characteristic analysis, and the transient analysis. By initially invoking the subroutine LOAD, the linearized system of nodal equations for the specific iteration is constructed. Separate computation of the nonlinear devices' contribution to the Y matrix is carried out by the respective subroutines. >

Monolithic bipolar diodes and their models

Abstract: The AC performance of the diode-connected, bipolar junction transistor (BJT) is examined. The discussion covers the BJT's most common connection, its small-signal behavior, and the current repeater that uses the diode as an input device. Looking at the AC behavior reveals the strengths and weaknesses of various models and simulators, primarily SPICE. It is shown that these common circuits are classic cases where models can fail. >

Simulation and modeling-alternate PSPICE switch functions

Abstract: Three different ways of formulating the switching function in PSPICE are discussed. One uses the tank function, one the Gudermannian function, and one the Fermi probability function. The properties of each are given. >

The mathematics of success and failure (SPC)

Abstract: The use of statistical process control (SPC) to improve quality is discussed. Mathematical tools and techniques for SPC are reviewed. How to decide when a change in an indicator is statistically significant is addressed. An approach to SPC in which one attempts to reduce process sensitivity to external variations rather than control these variations more tightly is discussed. >

Simulation and modeling-a CAD model for the BJT with self heating

Abstract: A Gummel-Poon model that accounts for self heating in the bipolar-junction (BJT) transistor is presented. The model uses a simple but flexible RC analog circuit for thermal effects. Junction temperature as a voltage is a byproduct of the modeling approach. In contrast to the standard model, this model does not require changes in BJT parameters in order to track circuit changes that affect BJT dissipated power. Although not presented here, transient behavior due to self heating and thermal capacitance has been tested, and it is also correctly predicted by this model. >

PC Programs for Engineers

Abstract: Two programs are described. The first is a program for digital signal processing that provides for a wide range of input signals and uses the fast Hartley transform for conversions from the time domain to the frequency domain and vice versa. The desired input waveforms can be created internally by the program or imported from an appropriate disk file. The data obtained can be stored in a file as well as displayed on the screen. The second program extends the use of the PC from performing algebraic operations on matrices to the case in which the matrix elements are complex numbers. It provides a compact, easily applied tool for performing sinusoidal steady-state computations and other operations requiring the manipulation of arrays of complex numbers. Examples of the use of both programs are given. >

Pumping with diodes

Abstract: The development of semiconductor lasers for pumping solid-state laser crystals is discussed. The basic operating principles of solid-state devices are reviewed to show why this new development is so important. Among the first of the new diode-laser technologies to be applied to pumping was the phase-locked array, which produced much higher power outputs and higher brightness from room-temperature CW diode-laser systems. With diode-laser arrays capable of power outputs between 0.2 and 2 W, and relatively good beam quality, it became possible to pump Nd:YAG and other crystals longitudinally, with the pump and laser output beams either parallel or antiparallel in the laser crystal. Diode pumping allows the flowing cooling liquids and fluctuating arc lamps used in conventional lamp-pumped lasers to be replaced by solid heat sinks and stabilized pump lasers. As a result, designers can build low-power solid-state lasers having high mechanical and thermal stability. Short-term linewidths in the kilohertz range can be obtained from diode-pumped devices, and the long-term drift of monolithic devices can be kept within 50 MHz for over an hour (for a center frequency of 3*10/sup 8/ MHz) by controlling the laser-crystal temperature. >

Circuit with nonlinear transformer provides isolation for DC measurements

Abstract: A nonlinear transformer that can be used to isolate a source from the measuring device is presented. A simple RL oscillator constructed with this transformer and a comparator is discussed. The oscillator uses a 220 Hammond pulse transformer and a LF356 operational amplifier with +or-12 V power supply voltage. Using a fast comparator and a small ferrite core transformer will yield a more versatile circuit. Ultimately, the multivibrator can work at frequencies to 30-40 kHz, and an electromagnetically-coupled isolation amplifier can be developed. >

Where do hot electrons come from? (MOSFETs)

Abstract: Troublesome hot electrons that are appearing in MOSFETs, even at reduced drain voltages, due to scattering in the device channel are discussed The use of the concept of 'electron temperature' to describe the energy spread that the electrons have as the result of the scattering is examined The relationship between electron temperature and reliability is considered The improvement in reliability that results from reducing the channel length, and thereby the amount of scattering, is discussed The analysis of short-channel devices, is briefly addressed >

Maxwell's children light the way

Abstract: An overview of the development of electronics is presented, beginning with the discovery, in 1874, of the first metal-semiconductor junction. Parallel advances in photonics are then discussed. The compatibility and complementarity of the two technologies are examined. >

Television by the bit

Abstract: The various types of advanced television (ATV) are defined, and the most advanced type, high-definition TV (HDTV), is discussed. The present status of HDTV development in the US, Japan, and Europe is examined. Signal processing requirements for HDTV are briefly considered, and the benefits of and prospects for all-digital HDTV are explored. Video compression techniques, implementation issues, and the future of HDTV are also discussed. >

Smart-power devices seek wiser CAE tools

Abstract: The difficulties in developing generalized computer design tools for smart-power semiconductor electronics, a highly specialized field requiring a mix of analog and digital integrated-circuit design, unique semiconductor-device-fabrication technology, and knowledge of application-specific power systems, are examined. These include the problem of dealing with the double-diffused MOS (DMOS) transistor, as well as the simulation of trench refill processes, 2D oxidation phenomena and their stress-induced effects on avalanche breakdown, and the 3D diffusion of the spherical junctions encountered in high-voltage termination. The complexities associated with 2D simulations are discussed in some detail. Dealing with asymmetric devices and with structures consisting of circles, arcs, and 45 degrees angles is also considered. >

Laser post-ionization improves surface analysis

Abstract: Laser post-ionization (PI), a technique that overcomes the greatest handicap of secondary-ion mass spectroscopy (SIMS), namely, its susceptibility to matrix effects is discussed. The SIMS matrix effect is the often unknown relationship between the chemical composition of a solid and the secondary ion yield of an analyte in the sample, which is unpredictable and can vary as much as seven orders of magnitude. PI, which involves passing a laser beam parallel to, and just above, a surface undergoing stimulated desorption, solves the problem by decoupling the ionization and desorption steps. This allows the detection of secondary neutral species, which typically constitute more than 95% of the material removed from the surface during ion beam sputtering. This largely eliminates matrix effects because the chemical matrix generally has much less influence on the emission of charged particles. To compete with SIMS on sensitivity, PI methods efficiently ionize sputtered neutrals and detect those positionized particles. The nonresonant method of PI, which comes in two variations, nonresonant multiphoton and nonresonant single-photon ionization and is called SALI (surface analysis by laser ionization), is described, and its application to semiconductors is examined. >

Designer's Casebook-Simple bipolar, constant-power source

Abstract: Biasing of a gas-flow sensor heating element requires a constant power level, despite resistance changes in this element. A solution to this problem is shown. >

Bringing the fiber to the home

Abstract: The issues involved in replacing copper telephone lines by fiber all the way to the subscriber's home are examined. The advantages of deploying single-mode fiber in the trunk and local-loop feeder networks are enumerated. The biggest problem namely, how to power the electronics in the absence of copper wire, is discussed. The need to allow a graceful upgrade to capture future opportunities for broadband revenue is emphasized, and potential broadband services are described. Predictions are made regarding the ISDN network of the future. >

Sailing off the edge of the earth. . .again

Abstract: The Columbus 500 Space Sail Race, which is intended to stimulate worldwide space exploration, education, and enterprise as well as commemorate the European discovery of the Americas, is described. Three solar sailing flagships-the Nina, Pinta, and Santa Maria -will be the official entries from three geographical regions: Europe, whence Columbus initiated his voyage; Asia, where he was headed; and the Americas, where he landed. Other vessels are also expected to compete. The vessel that takes the shortest time to travel from high Earth orbit to a point where it can place a commemorative plaque in high orbit around Mars will be judged the winner. The rules for the race are given, the science of solar sailing is explained, and some of the physical configurations for the sails and methods of deploying them are briefly described. Some of the experiments that are being considered to be conducted during flight are tested. Some of the technological difficulties anticipated are discussed. Plans to use the race to develop interest in science in grade schools and high schools around the world are described. >

Semiconductor photonic functional devices

Abstract: Recent advances in semiconductor photonic functional devices based on the nonlinearities of laser diodes (LDs) are reviewed Because the current research is driven primarily by the needs of optical fiber communications systems, most devices are made of InGaAsP and operate at wavelengths of between 13 and 155 mu m, the wavelength window in which optical fibers have their most favorable properties Minimum loss is at 155 mu m, and zero dispersion is at 13 mu m AlGaAs devices operating at around 085 mu m have also been reported Two types of optical bistability-absorptive and dispersive-are explained, and devices based on them are described Switching characteristics of bistable devices are discussed Tunable wavelength converters and filters are also examined Applications to all-optical communication and to optical switching systems are considered Directions for future development are indicated >