Andrew Beckett
Senior Fellow
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Life, don't talk to me about Life...
Posts: 1742
Bracknell, UK
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Well, you end up with more capacitors on the chip, which can increase the amount of coupling between signals. Say you have (sideways view):
------ -------- -------
where the top and bottom shapes are routing, and don't overlap. Without the middle dummy fill (if that's what it is), there would be a much smaller capacitance between the two and bottom shapes, than if the top couples to the dummy plate, which then couples to the bottom routing.
But of course, the dummy fill is to help with planarisation and so on, which also helps improve yield. So there are pluses and minuses!
Andrew.
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