6 Replies Latest reply on Mar 7, 2018 12:44 PM by khan

    Help in resolving LVS errors



      I am using Calibre LVS for the first time and I am using it while trying to follow the design flow document which comes with the 180nm PDK from TSMC. I am having an issue with my two stage buffer. I am attaching the LVS report, the schematic and the layout itself here. I generated the layout from the schematic source itself using Cadence's layout XL. All the pins and ports have labels associated with them in the layout but I still get error when compiling the LVS when it comes to the number of ports. I am also getting different number of instances (both PMOS and NMOS) which is stemming from the fact that I am using multifingered transistors.


      Again I am using calibre for the first time. Any help in resolving these error messages is appreciated.

        • 1. Re: Help in resolving LVS errors

          Hi Khan-


          Probably the only problem is a mismatch in ports. Two common causes of that are no port objects in the layout, or the SVRF rules don't indicate how to recognize the ports (by text or polygons).

          • Text ports need PORT LAYER TEXT somewhere in the rule file.  If it uses explicit label attachment, you'll also want to check the ATTACH rules.  If the rule file has TEXT LAYER + connectivity, you can use the same layer as PORT LAYER TEXT.
          • Polygon ports need to be idetnified with PORT LAYER POLYGON.  Should probably also check any ATTACH statement, as explicitly attached text will make it easier to identify the ports in the output.

          Hope that helps-



          • 2. Re: Help in resolving LVS errors

            Hello Miss Lizak,


            I am new to the Calibre environment so I am not familiar with the format of Calibre rules files. Are PORT LAYER TEXT and PORT LAYER POLYGON variables with the rules file? Is it advisable to edit the rules file provided by the foundry or are there  GUI options where I can turn them on/off?


            -Marouf Khan

            • 3. Re: Help in resolving LVS errors

              The parts in all capitals are SVRF statements and should be somewhere in the rule file.  (If you are using batch mode, the rule file is specified at the end of the invocation -- "calibre -lvs <bunch of -options> <filename>".  Rule files can include other rule files using INCLUDE statements, though, so you may need to dig a bit.  Some foundries also encrypt their rules, but I think that is not common for LVS. 


              If you are using Calibre Interactive, there are some ways to enter SVRF statements in the GUI.  I haven't used Calibre Interactive in a while (I am primarily OPC these days) so it would be best to check the manual on where that is done.  And, of course, if you are invoking Calibre from Cadence, there may be something in the configuration files that sets it up.  (In that case, best to check with whoever is responsible for gluing the tools together.)


              Sorry I can't be more help-



              • 4. Re: Help in resolving LVS errors

                Thanks for the reply Miss Lizak,

                Yes  I am using calibre interactive. could you direct me as to where I can invoke the manual? If I understand you right, there is a way to modify SVRF statements using the gui without needing to modify the LVS rules file provided by the foundry?


                And one more question, does Calibre LVS compare the schematic with the extracted view of the layout only? Does it work if you compare the schematic with the pre-extraction layout?  I am asking because DIVA from cadence only compares the schematic with the extracted layout. Should I run Calibre PEX on my layout before I do LVS?




                -Marouf Khan

                • 5. Re: Help in resolving LVS errors

                  Hi Mr Khan-


                  To open the manual from Calibre Interactive, use the Help menu (right side of the menu bar) in the nmLVS window. The "Open User's Manual" item opens an HTML version of the Calibre Interactive manual.

                  If the doc variables aren't set up, or your site has wrapped the standard Calibre Interactive window so that the Help menu isn't available, you can navigate directly to the manuals.  The CI manual is located in $CALIBRE_HOME/docs/pdfdocs/calbr_inter_user.pdf.  (There is also an HTML version; load the htmldocs/calbr_inter_user/index.htm file in a browser.)


                  Regarding extraction or pre-extraction, pre-extraction would be simpler.  Calibre does parasitic extraction with the PEX products (xRC or xACT, and xL), which are supposed to be run after the layout is LVS clean.  (You can run them without an LVS database, but it is less common.)  The output from PEX shows the parasitics as connected to the intended nets; running LVS again on a layout that included the parasitics would definitely report a mismatch.


                  May I also recommend the Calibre Quick Start for some self-paced training?  It includes a design and rule files along with a manual that walks you through how to perform the basic operations of the common tools. Because there are complete rule files, Mentor places it behind a click-through license on Support Center but it is absolutely free.

                  1. On Support Center in the Calibre area, go to Downloads.  If you are using a Calibre version older than 2017.3, see if you can set your version to that so that you'll get the Quick Start that best matches what you are using. (The version selection is a dropdown list on the right, "Restrict content to version".)

                  2. Click "Related Downloads" (it is in the line of smaller font between the date and the big blue download link).

                  3. Click "Calibre Utilities, Examples, Scripts and Interface Software".

                  4. Click "I agree".

                  5. Scroll to the bottom or click the link "Calibre Example Kits (eKits) and Tutorials".

                  6. Look for "calbr_QS_ekit_<version>.tgz".


                  Good luck-



                  • 6. Re: Help in resolving LVS errors

                    Hello Miss Lizak,

                    I managed to resolve the issue.

                    You mention the quick start guide which helps with some self-paced training. I have a support account but it says external next to it. I don't see a Calibre or Downloads area in my support center dashboard. I am guessing I need a site id. I am going to have contact the system admin at my university. Once I get it, how do I update my support account with it?