Sonnet User's Guide - Sonnet Software

Chapter 16 Vias and 3-D Structures
Chapter 16 Vias and 3-D
Structures
Introduction
Em can handle full 3-D current as well as 2.5 D structures. The third (Z) dimension
of current is handled by a special kind of subsection called a via.
The term “via” commonly refers to a connection from metal on the substrate surface
to the ground plate beneath the substrate. However, as used in Sonnet, a via
can be used to connect metalization between any substrate or dielectric layer, not
just bottom layer to ground. Thus, em’s vias can be used in modeling airbridges,
spiral inductors, wire bonds and probes as well as the standard ground via.
Restrictions on Vias
Em’s vias use a uniform distribution of current along their height and thus are not
intended to be used to model resonant length vertical structures. The height of the
via should be a small fraction of a wavelength. The via height is the same as the
thickness of the substrate (or dielectric layer) it penetrates.
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