Metallization systems for silicon integrated circuits

An investigation into single and composite layered metallization systems is described with respect to their limitations, possible failure mechanisms, and problems encountered in fabrication. Systems investigated include metals such as chromium, titanium, tungsten, and molybdenum in conjunction with gold. Comparisons are made to conventional aluminum with respect to ohmic contact to silicon, metallurgical reactions, behavior in adverse environmental conditions, method of deposition, and processing difficulties.     

Linear integrated circuits in communication systems

Advances in monolithic technology are broadening the applications areas in which integrated circuits are becoming economically feasible. This article demonstrates the design approaches that permit the realization of communication circuitry functions while simultaneously meeting the constraints imposed by MSI and LSI techniques.     

Programmable logic circuits for functional integrated smart plastic systems

In this paper, we present a functional integrated plastic system. We have fabricated arrays of organic thin-film transistors (OTFTs) and printed electronic components driving an electrophoretic ink display up to 70 mm by 70 mm on a single flexible transparent plastic foil. Transistor arrays were quickly and reliably configured for different logic functions by an additional process step of inkjet printing conductive silver wires and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) resistors between transistors or between logic blocks. Among the circuit functions and features demonstrated on the arrays are a 7-stage ring oscillator, a D-type flip-flop memory element, a 2:4 demultiplexer, a programmable array logic device (PAL), and printed wires and resistors. Touch input sensors were also printed, thus only external batteries were required for a complete electronic subsystem. The PAL featured 8 inputs, 8 outputs, 32 product terms, and had 1260 p-type polymer transistors in a 3-metal process using diode-load logic. To the best of our knowledge, this is the first time that a PAL concept with organic transistors has been demonstrated, and also the first time that organic transistors have been used as the control logic for a flexible display which have both been integrated on to a single plastic substrate. The versatility afforded by the additive inkjet printing process is well suited to organic programmable logic on plastic substrates, in effect, making flexible organic electronics more flexible.     

Surface micromachining for microelectromechanical systems

Surface micromachining is characterized by the fabrication of micromechanical structures from deposited thin films. Originally employed for integrated circuits, films composed of materials such as low-pressure chemical-vapor-deposition polycrystalline silicon, silicon nitride, and silicon dioxides can be sequentially deposited and selectively removed to build or “machine” three-dimensional structures whose functionality typically requires that they be freed from the planar substrate. Although the process to accomplish this fabrication dates from the 1960's, its rapid extension over the past few years and its application to batch fabrication of micromechanisms and of monolithic microelectromechanical systems (MEMS) make a thorough review of surface micromachining appropriate at this time. Four central issues of consequence to the MEMS technologist are: (i) the understanding and control of the material properties of microstructural films, such as polycrystalline silicon, (ii) the release of the microstructure, for example, by wet etching silicon dioxide sacrificial films, followed by its drying and surface passivation, (iii) the constraints defined by the combination of micromachining and integrated-circuit technologies when fabricating monolithic sensor devices, and (iv) the methods, materials, and practices used when packaging the completed device. Last, recent developments of hinged structures for postrelease assembly, high-aspect-ratio fabrication of molded parts from deposited thin films, and the advent of deep anisotropic silicon etching hold promise to extend markedly the capabilities of surface-micromachining technologies     

Interconnection systems for solid-state components in hybrid integrated circuits

The factors which can influence the performance and reliability of the interconnection system for solid-state components in hybrid integrated circuits are examined. The main emphasis is on materials that have received most attention in the tantalum film and silicon technologies in the Bell System. However, other materials that are being used are discussed. The interrelation of various factors in choosing an interconnection system is discussed. These factors include the composition of the materials, the methods of depositing various metals, and the properties of the substrates. Among the properties of the materials that are considered, emphasis is laid on environmental stability. The results of environmental tests on conductors and thin-film resistors under high-humidity conditions are reported. Some results on the use of silicone rubber as an encapsulant indicate this material is effective in reducing degradative action on hybrid circuits.     

Silicon bipolar integrated circuits for multi-Gb/second opticalcommunication systems

The authors discuss several important circuits for fiber-optic transmission, implemented in an advanced silicon bipolar integrated circuit technology. Specifically, the authors discuss the design considerations and measured performance of a 2:1 multiplexer, front end receiver, limiting amplifier, and decision circuit IC. Also discussed are three hybrid circuit modules: a 2:1 multiplexer, 1:2 demultiplexer, and parallel processing decision circuit. These ICs and hybrid circuit modules operate at multi-Gb/s data rates. The performance of these ICs indicates that advanced silicon bipolar integrated circuits with their high speed, functionality and low cost potential could play an important role in alleviating the electronic bottleneck in future multigigabit optical communication systems     

Packaging for microelectromechanical and nanoelectromechanical systems

Packaging is a core technology for the advancement of microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS). We discuss MEMS packaging challenges in the context of functional interfaces, reliability, modeling and integration. These challenges are application-dependent; therefore, two case studies on accelerometers and BioMEMS are presented for an in-depth illustration. Presently, most NEMS are in the exploratory stage and hence a unique path to identify the relevant packaging issues for these devices has not been determined. We do, however, expect the self-assembly of nano-devices to play a key role in NEMS packaging. We demonstrate this point in two case studies, one on a silicon nanowire biosensor, and the other on self-assembly in molecular biology. MEMS/NEMS have the potential to have a tremendous impact on various sectors such as automotive, aerospace, heavy duty applications, and health care. Packaging engineers have an opportunity to make this impact a reality by developing low-cost, high-performance and high-reliability packaging solutions.     

Millimeter-wave integrated circuits

Monolithic millimeter-wave integrated circuits have been designed and fabricated on semi-insulating GaAs substrates using microstrip transmission lines. Circuits using hybrid techniques have also been constructed on quartz and ceramics. This paper shows that microstrip-line integrated circuits are feasible at millimeter-wave frequencies. Circuit functions have been constructed and tested in the 25- to 100-GHz range. The loss in microstrip line on semi-insulating GaAs was found to be less than 0.3 dB/λ. Couplers from waveguide to microstrip have been made with transmission losses less than 0.5 dB. Monolithic integrated detectors showed 5-dB better sensitivity than a 1N53 diode in a philips detector mount. Monolithic diodes delivered 1.5 mW at 28 GHz. The results are encouraging and a fully monolithic integrated receiver is under development.     

Coupled package-device modeling for microelectromechanical systems

Microelectromechanical systems (MEMS), by their nature as sensors and actuators, require application specific packaging. The package is the near environment of the MEMS device and hence has a direct effect on its thermal behavior, mechanical effects, environmental compatibility and contamination. Therefore, understanding the influence of the packaging on MEMS device performance is critical to a successfully coupled package-device co-design. Here, an automated package-device interaction simulator has been developed. The simulator uses separate finite element method models for both the package and the device analysis and ties the simulations together through parametric behavioral package models. This technique allows the generation of package model libraries and supports the co-design of application specific packaging and MEMS devices. In the current implementation, thermomechanical package models have been implemented. Experimental verification of the technique is demonstrated by the comparison of simulation results to the measured package strain data. Although MEMS device-package interactions are not the only systems that could benefit from this method, they are a significant application area, focused on here.     

GaAs integrated circuits for error-rate measurement in high-speed digital transmission systems

A high-speed GaAs MSI PRBS generator and an error detector have been built, tested, and applied to bit-error ratio measurements in a fiber-optic transmission link. The generator produces a 1023 bit sequence at 2 Gbit/s data rate. The detector compares, bit-by-bit, the input data with a locally regenerated sequence. With a 2 GHz clock, the direct-coupled generator/detector combination, without an optical link, exhibits less than one error in 10/SUP 14/ clock cycles. The complete fiber-optic link test system incorporates a 1 km multimode fiber, operates at 1.9 Gbits/s, and exhibits a bit-error ratio below 10/SUP -12/.     

Power estimation methods for analog circuits for architecturalexploration of integrated systems

This paper describes methods for analog-power estimation and applies them practically to two different classes of analog circuits. Such power estimators, which return a power estimate given only a block's specification values without knowing its detailed circuit implementation, are valuable components for architectural exploration tools and hence interesting for high-level system designers. As an illustration, two estimators are presented: one for high-speed analog-to-digital converters (ADCs) and one for analog-continuous time filters. The ADC power estimator is a technology scalable closed formula and yields first-order results within an accuracy factor of about 2.2 for the whole class of high-speed Nyquist-rate ADCs. The filter-power estimator is of a more complex nature. It uses a crude filter synthesis, in combination with operational transconductor amplifier behavioral models to generate accurate results as well, but restricted to certain filter implementations