
IC DfM for Devices and Products 141
The ll pattern overlying and underlying the actual inductor (Figure3.31)
[45] may be added in a relatively nonintrusive way as compared to manual
metal ll over the entire inductor area, just to provide the minimum required
amount of metal coverage. The optimal ll pattern should minimally have an
impact on Q, L, and the self-resonance frequency of a differential inductor
(Figure3.32) built in top-level metal on a high-resistivity substrate. Excluding
the inductor and its surrounding space from ll algorithms will prevent
changes to their characteristics, assuming that the nal pattern density ...