Dummy block in virtuoso layout

[ceyhun]

Hi everyone,
I'm designing the layout of an analog circuit in virtuoso layout. In some of the components I use there are dummy blocks. What do these blocks do? Why do I have to use them?

Thanks

 

[erikl]

• If block = (any) device: devices at both (or all 4) sides of other (2 or more) devices of the same type, which need good matching (keeping matching environment)
• If block = standardCell or any other cell: to have spare parts in case a redesign/repair has to be done. In this case, pay attention that such spare parts can be reconnected by changing metal1 only (repair by 1-mask-change). And those spare dummy cells shouldn't be placed too far from where they could be needed ;-) . Mix dummy stdCells between the used stdCells!