Application: 60 GHz on-chip balun transformer: effect of dummy metal fill

Jul 2018
A new application note has been published by our partner Dr. Volker Mühlhaus

This application note investigates the effect of dummy metall fill on the performance of a 60 GHz balun. The balun design is described in this application note.

Dummy metall fill is used to fulfill metal density design rules. If possible, such filler is blocked underneath and near inductors and transformers, to avoid a reduction in performance. But the question is: how much effect is that, and what filler distance is “safe”? In this document, we investigate the effect of different filler placements on a balun.

In many EM simulations, the electrical effect from fillers is considered small, and they are removed from EM simulation to speed up simulation. But here, to investigate the filler effect, we need to include them and this results in models with >100k metal polygons. Such a large model would be very time- and memory consuming for Method of Moments (MoM) or Finite Elements (FEM) solvers.

Empire XPU was selected for this simulation, because Empires FDTD method scales very efficiently for large number of mesh cells. Empire XPU features very high processing speed and enables models with large number of metal polygons, in reasonable time, with full 3D EM accuracy.

For more information please visit http://muehlhaus.com/support/rfic-em-appnotes/60-ghz-balun-filler-effect