Illegal via ("tsmc18rf" "M1_POLY1" &quot

I run "Design synthesis -->Layout XL" in virtuoso schematic editor , then I run "Placer" or "Export to Router",there will be warnings in CIW,says:
......
\o Export from DFII: Starting export.
\o Exporting "Inverter inv_sym layout" from DFII...
\o Exporting version 11.0.9 syntax from exportVersion environment variable.
\w *WARNING* Illegal via ("tsmc18rf" "M1_POLY1" "symbolic") specified in (("tsmc18rf" "M1_POLY1" "symbolic") t).
\w *WARNING* Illegal via ("tsmc18rf" "M2_M1" "symbolic") specified in (("tsmc18rf" "M2_M1" "symbolic") t).
\w *WARNING* Illegal via ("tsmc18rf" "M3_M2" "symbolic") specified in (("tsmc18rf" "M3_M2" "symbolic") t).
\w *WARNING* Illegal via ("tsmc18rf" "M4_M3" "symbolic") specified in (("tsmc18rf" "M4_M3" "symbolic") t).
\w *WARNING* Illegal via ("tsmc18rf" "M5_M4" "symbolic") specified in (("tsmc18rf" "M5_M4" "symbolic") t).
\w *WARNING* Illegal via ("tsmc18rf" "M6_M5" "symbolic") specified in (("tsmc18rf" "M6_M5" "symbolic") t).
\o Export from DFII: Export completed.
\o Successfully exported "Inverter inv_sym layout" from DFII.
\o Export from DFII: Starting Router...
.....
how to solve this problem???
I'm using ic5141 base.
thank you .

It looks like it doesn't like the symbolic type of via. Try to replace one of these vias in your design by a self-made layout cell, (just flatten one of this vias into your cell called viaM1M2, layout) and see if you still get the warning