9710568 Virga Research Activities - This research is directed at characterizing the performance behavior of high-density interconnect and distribution structures employed in compact high-speed digital and wireless communications circuit packages, The primary focus is to develop advanced measurement-based characterization techniques for complex, three-dimensional (3-D), multi-layer, interconnect structures. Examples of complex interconnects include non-ideal (non-circular and non solid) multi-layer vias, many closely-spaced vertical conductors, fuzz buttons, and transitions between vertical and horizontal conductors. Embedded interconnects are typically inaccessible in a package, thus there are currently no means to directly measure individual structures. Since advanced high-density circuit packages incorporate very mixed-signal technologies, such as digital, analog, and RF signal conductor traces, hybrid measurement methods must be developed to accurately identify interconnect performance. High payoff is achieved when measurement results are linked with advanced packaging design simulation tools. The coordination of computer-aided design (CAD) and computer aided test (CAT) results in improved first past design success and enables the rapid development of novel, low-cost advanced packaging technologies. The research will involve both time-domain and frequency-domain measurement techniques. The work will entail a balance between microwave-based (scattering parameters) and microelectronics-based (unique voltages and currents) methodologies. The specific objectives of this research are develop advanced measurement methodologies based upon a hybrid of time-domain and frequency-domain approaches as well as microwave and microelectronics based approaches for three dimensional embedded interconnect structures employed in high-speed digital and wireless circuits, develop links between measured characteristics and circuit analysis and design simulation tools, characterize a few complex inter connect structures and make test results available to code developers to be used as benchmarks for comparisons with high performance simulation tools. The research will first involve defining various advanced 3-D interconnects for high-speed digital, RF, microwave, and MEMS (Micro-Electromechanical Systems) packaging. The theoretical background and implementation details of current measurement techniques for calibration and interconnect de-embedding will be evaluated. New measurement techniques that overcome the fundamental limitations of existing methods will be developed. Such methods will be developed from hybridizing time-domain & frequency-domain techniques. The new methods will be used to provide accurate calibrations that do not rely on unrealistic packaging assumptions. Interconnect de-embedding and statistical-based interconnect characterization will also be developed. Several structures will be fabricated in order to provide validations to the new approaches. The last part of the research will be geared toward creating links between measured interconnect characteristics and design simulation tools. One novel approach to use in these links is the space-mapping technique that has been successfully used in the simulation-based optimization of some microwave circuits. ***
