Coupling effects are often overlooked until their unwanted effects are quite noticeable. At the system level, coupling can be defeated by means of additional shielding and metal enclosures. But at the integrated-circuit (IC) level, unwanted coupling usually results in a mask redesign and another (expensive) run at the foundry. Fortunately, some of those extra wafer runs can now be avoided by studying the effects of IC component coupling with software, the PeakView suite of software tools from Lorentz Solution, Inc. (Milpitas, CA).
Although digital ICs are often associated with the number of active devices or gates, RF/microwave designs are more likely to be dominated by larger passive structures, such as capacitors and inductors. Such structures have a tendency to couple across a chip, especially when ICs are miniaturized. Passive circuit elements have been difficult to model, typically requiring long simulation runs with three-dimensional electromagnetic modeling tools that may neglect the effects of coupling.
PeakView is a three dimensional electromagnetic (EM) design and verification tool suite that has been developed for high-frequency IC architects dealing with potential coupling from passive structures and components, such as spiral inductors. Based on patent-pending EM coupling simulation/ modeling technology, the software suite provides comprehensive passive component model and layout synthesis capability for a variety of computer platforms, including UNIX workstations and Windows-based personal computers (PCs). The software features a simple Windows graphical user interface (GUI) with drop down menus that allow operators to select components and structures from an existing library or create their own structures with editing tools.
Rather than relying on wafer runs with test patterns and structures to characterize and validate different components, PeakView analyzes the effects of conductors in close proximity, such as the turns of a spiral inductor, and displays coupling as a function of frequency (see figure).
PeakView has been tightly integrated-with popular circuit-design and physical-layout environments, such as IC modeling tools from Cadence Design Systems (www.cadence.com), to assist at both the design and optimization stages. During physical design and layout, for example, PeakView can be used to verify that layout area-optimization methods do not introduce new sources of EM coupling. PeakView is easily calibrated per foundry-specific process design kits (PDKs) to make sure simulation results match measured data.
PeakView can handle large circuits without long simulation runs, and can be used at layout optimization to check for potential coupling problems due to reworked layouts.
Lorentz Solution, 1900 McCarthy Blvd., Suite 208, Milpitas, CA 95035; (408) 922-0765, Internet: www.lorentzsolution.com