Layout vs. Schematic

The first step in running LVS is to make an extracted view from the layout you have just completed.  In this case, and in most cases, you need to extract with parasitic caps.  We discussed the extraction process in the first section of this tutorial, so we will not discuss it here.Next, click Verify->LVS, which will bring up a form for setting up the LVS.  If LVS has been run before, there will most likely be two windows that come up.  The smaller window will alert the user the the LVS correspondence file and the form contents do not match.  Select Form Contents and click OK.  This window is seen in figure 19.

Figure 19.  LVS window warning that file and form do not match

On the LVS form, make sure you have the run directory set, default is ../LVS.  Make sure you are comparing the schematic and extracted views of the same cell in the same library.  Set the priority to 20 and click Run.  The completed form can be seen in figure 20.

Figure 20. LVS setup form

The CIW will contain a line that says LVS job is now started.  The LVS takes time, and it will appear the nothing is going on because no messages will be displayed in the CIW or anywhere else on the screen.  After some time and window will popup saying the job has succeeded.  This is a bit deceiving because the netlists do not necessarily match, but the message just states that the job did finish.  On the LVS form, click Output to see the results of the verification test.  If it states that the lists match, congratulations, you got it right.  If the lists to not match, there is something wrong in your layout, you will need to fix it, and you will need to re-extract and LVS.  A sample output window can be seen in figure 21.

Figure 21.  LVS output file

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