Faculty Candidate Seminar

Electromagnetic Simulations of Signal Integrity in Interconnects: Effects of Multiple Vias and Surface Roughness

Professor Leung Tsang

Professor Department of Electrical Engineering
University of Washington
Wednesday, September 18, 2013
09:30am - 10:30am
Johnson Rooms 3rd Floor Lurie


About the Event

We analyzed two problems in signal integrity of interconnects: effects of multiple vertical vias and effects of rough surface roughness. The methodologies are based on multiple scattering of waves. Vias are one of the key structures in multilayered substrates of high speed interconnect circuits, which aim to provide a new design complexity of vertical integration. Parallel-plate waveguide modes and cavity modes are induced by high frequency signals along vertical vias. Because of multiple scattering among the coupled vias, such interference poses serious problems in signal integrity. In electromagnetic simulations, we use the Foldy-Lax equations to compute the full wave solution of Maxwell equations that includes multiple scattering among cylindrical vias in infinite planar waveguides and in finite cavity. The Foldy-Lax approach has been extended by combining with 1D discretization in MoM, T matrix method, cylindrical waves and cavity mode expansions of Green’s functions. Results are in good agreement with HFSS and with experiments . The intentionally roughened interface between signal traces and substrate has a significant impact on signal integrity in high speed interconnects on printed circuit boards (PCBs) and microelectronic packages in the gigahertz frequency range. At such frequencies, the rms heights of roughness are comparable to the copper skin depth, increasing the dissipation in copper. The classical result of absorption enhancement is based on the Hammerstad and Bekkadal formula. We studied roughness effects in waveguide environment using analytical models and numerical simulations. The results show departures from the HB formula. Using second order perturbation method, analytical expressions of the absorption enhancement factors were derived. Numerical simulations are based on mode matching in combination with MoM and FEM. Analytical and simulations results are in good comparisons with experiments.


Leung Tsang received the Ph.D. degree from the Massachusetts Institute of Technology. He has been a Professor of Electrical Engineering at the University of Washington since 1983 and was the Chair of the Department in 2006-2011. He was the President of IEEE Geoscience and Remote Sensing Society in 2006-2007 and the Editor-in-Chief of the IEEE Transactions on Geoscience and Remote Sensing in 1996-2000. He is the co-author of 4 books: Theory of Microwave Remote Sensing (Wiley-Interscience, 1985), Scattering of Electromagnetic Waves, Vols. 1, 2 and 3.(Wiley Interscience, 2000, 2001) . He received the Pecora Award (cosponsored by Department of Interior (USGS) and NASA) in 2012, and the IEEE Electromagnetic's Award in 2013.

Additional Information

Contact: Linda Scovel

Phone: 734-763-3260

Email: lscovel@umich.edu

Sponsor: ECE

Open to: Public