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Electrical and Computer Engineering

Electromagnetics Communication and Electronics Packaging
^ CAD Tools for Communications Microsystems
J. Schutt-Ainé,* D. Lambalot, L. Jiang
Defense Advanced Research Projects Agency, AF ECE0849

Recent developments in the area of wireless communication systems and microelectromechanical systems (MEMS) have enabled the networking of distributed transducers in a wireless mode. It is now possible to integrate monolithic microwave integrated circuit (MMIC) front-end modules with MEMS components such as antennas, switches, and filters. Our objective is to supply the necessary CAD tools to improve first-pass success and reduce design iterations for such systems. In particular, electromagnetic techniques are used to model various MEMS switch structures. These are combined with simulation techniques to predict the transient and steady state response of these components. The goal is to reduce the design cycle from several years to one week in the successful implementation of these MEMS structures.

^ Design and Fabrication of MEMS Probe Station
J. Schutt-Ainé,* C. Liu, D. Lambalot
University of Illinois, Research Board

Recent advances in microelectronics have led to considerable reduction in size of components in integrated circuits (ICs). Typical VLSI circuits have dimensions in the submicron range and feature size that can be as low as 0.25 microns. This reduction is a result of several requirements for higher density and shorter interconnection delays. Future state-of-the-art microprocessors will accommodate more than a million transistors in an area of a few hundred squared millimeters. Along with these trends, several issues related to signal integrity and testing have moved to the forefront. With submicron dimensions, interconnect resistance has become a major bottleneck in circuit performance, leading to signal degradation and delays. In addition, measurement and testing in submicron geometries, which allows for determining the performance of the structure, is a challenging task. Nowadays, the methods employed consist of fabricating special-purpose test vehicles for evaluation, which often require expensive mask processes and complex de-embedding schemes. This investigation proposes to implement a nondestructive testing methodology for submicron integrated circuits using the recent advances in microelectromechanical systems (MEMS). More specifically, we intend to fabricate and test a microprobe structure that will permit the high-frequency characterization of submicron interconnects and devices in integrated circuits.

^ Development and Modeling of Flip Chip and Interconnect Package Technology for Ka and W Band
J. Schutt-Ainé,* F. Liu
National Science Foundation, E-21-N50-G5

(In collaboration with the NSF-Package Research Center Georgia Institute of Technology)

The electrical performance of mixed-signal integrated circuits strongly depends on the electromagnetic behavior of the components within the system. Future wireless and personal communication links will be strongly influenced by these considerations. Currently, millimeter-wave monolithic ICs (MMICs) chip sets are under development in the 24-94 GHz range. In recent years, power distribution and parasitic noise control have become critical issues in the design of these MMICs. Nowadays, with increased frequencies, interconnect schemes, layout and power distribution have become mainstream design issues. It is now recognized in the CAD community that electromagnetic effects will generally take place at the forefront and will represent the critical limiting factor of MMICs performance. The collaborative effort between Georgia Tech and the University of Illinois focuses on developing the technology support for the implementation of low-cost packaging solutions for MMICs. This is to be achieved by harnessing the modeling, simulation, design, fabrication, and measurement infrastructure built over the past decade at these two institutions.

^ High-Frequency Measurements and Validation of Electromagnetic Models in Scattering Interconnects, and Optoelectronics
J. Schutt-Ainé*
AFOSR, AF JS 1660

There is tremendous demand for increased capacity in high-speed communication networks and novel applications in optical control of antenna phased arrays. With clock rates in the GHz range, interconnect considerations and electromagnetic phenomena have moved to the forefront in the design of high-speed computers. Microwave modulation of optoelectronic devices such as semiconductor lasers and modulators plays an important role in determining the high-speed performance of these devices. Continuing development of high-speed optical communication systems is contingent upon advances in high-speed sources and wavelength conversion devices. While numerous theoretical models have been developed to predict ways to improve these devices, much experimental work remains in order to verify these models and characterize devices based on new designs. This project proposes the experimental validation of various computational models in inverse scattering, wave propagation, interconnects, and optoelectronics. Most of the emphasis will be on the higher frequency range where measurement information is nonexistent. Computational electromagnetics has received in recent years growing interest due to the availability of fast computers and the recent development of fast algorithms. Models that allow the prediction of the most complex problems in scattering and wave propagation have been implemented. Unfortunately, the experimental verification of these models is seriously lagging, especially at higher frequencies where measurement accuracy and repeatability are more difficult to achieve. This project will allow us to determine the frequency range of validity of the computational models and generate useful information for high-frequency operation of radiating, optoelectronics, and waveguiding systems.

^ Low-cost Fully Monolithic RF Integrated Circuits for Wireless Applications
J. Schutt-Ainé*
National Science Foundation, ECS-9979292

The performance of radio frequency (RF) integrated circuits will strongly influence the versatility and portability of future wireless communication systems. With the ever-increasing demands for higher bandwidth and capacity as well as reductions in size weight and cost, the need for more robust and efficient RF circuits is expected to increase. Currently, millimeter-wave monolithic ICs (MMICs) chip sets are under development in the 24-94 GHz range and will represent the platform for the RF components of most wireless systems. With the recent advent of microelectromechanical (MEM) systems, new potentials are being discovered for applications in the RF/millimeter wave ranges. In order to implement RFICs for future wireless communication systems, several fundamental issues must be resolved. First, a design methodology must be devised and tested. Next, a low cost solution for the integration of MEM technology into existing MMIC processes must be developed as well as a reliable packaging scheme. Finally, a robust platform of design guidelines, tools and characterization techniques must be made available to insure reliable implementation of these communication systems. More specifically, the effort will focus on these tasks: developing a computer-aided design environment for the robust implementation of MMICs and MEMs as well as the generation of reliable design guidelines; implementing a robust MEM process for the fabrication of switches, filters, and tunable capacitors; integration of MEM components into a reliable and well-established MMIC process; devising a low-cost and reliable packaging solution for RFICs. Executions of these tasks will make use of the existing infrastructure and expertise of the principal investigators in the related areas. These will define several design-build-test cycles that will be optimized through several iterations during the course of the project. Special attention will be devoted to demonstrating the feasibility of these various tasks. Moreover, a testbed prototype will be implemented to validate the proposed flow and assess the hardware advantages of the designed RFICs.

^ Modeling and Simulation of Embedded Transmission Line Structures
J. Schutt-Ainé,* F. Liu
Raytheon Systems

Embedded transmission line (ETL) structures have become very commonplace in many high-frequency and high-speed electronic systems; however the analysis and design tools needed for their design are not readily available. The objective of this effort is the modeling, extraction, and simulation of three-dimensional complex interconnect structures embedded in multilayer structures. The focus of the work will be on the development of software tools that facilitate and automate the designer's task. The tools will be based on recently developed electromagnetic parameter extraction techniques to determine the electrical parasitic capacitance and inductance coefficients of these structures. These parameters can next be used with efficient simulation algorithms to predict the signal response of ETL structures and provide information about noise immunity and high-speed performance. This will permit the generation of reliable design guidelines as well as a significant reduction in the time to market.

^ National Course in Signal Integrity
J. Schutt-Ainé*
IEEE CPMT; National Science Foundation

ASignal integrity has become a critical area in the design of high-speed communications systems and fast computers. Many research areas have emerged from industry and universities to address issues related to electrical performance. However, the educational infrastructure is seriously lagging. The goal of the National Course in Signal Integrity project (http://natcsi.ece.uiuc.edu) project is to establish a web-based educational platform that will provide the education necessary for aggressive packaging schemes in the area of signal integrity. This is achieved by providing a better understanding of electromagnetics problems and through the use of modeling and simulation tools. With the emergence of visualization tools and online simulation packages, access to both qualitative and quantitative answers is immediate. In addition to the standard components of web-based courses, we have focused our attention on two major components. In the first part of the project, a Movie Creator was implemented in this project; the tool allows the incorporation of taped lectures into a web site with synchronization between the audio and video components. In the second part of the project, an efficient Perl/Java interface was created that permits the execution of signal integrity modeling and simulation CAD tools in the web server. The study of signal integrity issues is strongly dependent on the ability to simulate and model signal propagation. This task seeks to supply circuit modeling and simulation capabilities using state-of-the-art techniques and analysis tools that were previously developed. A combination of visualization tools and the ability to perform online simulations can provide students with immediate access to both qualitative and quantitative answers. Using our newly developed tool, simulation results can be displayed and examined in a web browser shortly after execution. This unique feature of executing CAD software via the web will be a major asset in learning environment.


Summary of Engineering Research