[Libre-silicon-devel] Design rules

Tim Edwards tim at opencircuitdesign.com
Thu Aug 1 14:40:29 CEST 2019


Hello David,

> Magic uses the MOSIS design rules by default (on which we've built our rules).
> The minimum width and length for contacts (including poly contact) is 4 lambda
> (2 microns side length).

Be aware that magic defines a contact layer in the same way that a LEF
technology file would describe a "VIARULE".  It is an area that defines
not only the contact cut, but also all metal overlaps, and potentially
any number of contact cuts that will fill the area.

The "cifoutput" section of the techfile usually defines the contact
layer using the "squares" statement.  The "squares" statement defines
the cut size, spacing, and metal overlap.

For any real process, you would want to define the cut size, spacing,
and overlap as needed.  They do not follow lambda rules, but are in
centimicron units corresponding to physical dimensions in the output
GDS file.

It is possible to define a contact layer in magic as corresponding to
exactly one contact cut, but that is not the intent of the SCMOS ruleset.

					Regards,
					Tim

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