LVS failed with property errors with LVS PROPERTY RESOLUTION MAXIMUM ALL

Document created by matthew_killinger on Sep 7, 2012
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The design has a large number of dummy mosfets with gates connected to power and outputs floating.  LVS is incorrect with property errors, even with LVS PROPERTY RESOLUTION MAXIMUM set to ALL.


The problem is that initial device matching does not group devices by type or size.  All the dummy devices will be put into the same bucket; ambiguity resolution will then use device properties afterward.  Unfortunately, that algorithm can be facing a great deal of ambiguity in this case, even when property resolution maximum is set to a high number (or ALL).  Devices are then arbitrarily matched, giving rise to property errors.


Some aspects of the initial device matching can be arbitrary, so different releases may give different results.




If the dummy mosfets use different types such as hvt, svt, lvt in both source and layout, LVS EXACT SUBTYPES YES can help by reducing the scope of the problem.  The devices get sorted into buckets by type first, then ambiguity resolution has a higher probability of success.


LVS EXACT SUBTYPES YES enforces LVS STRICT SUBTYPES YES, so this may not work if the source netlist does not specify subtypes.


Another possible solution is to add either text to the layout or to specify LVS CPOINT statements to provide additional correspondence points for the compare algorithm.


Lastly, addition of a richer HCELL list may aid in topology matching.