21/08/2025

How do you interpret LVS report mismatches?

o   Incorrect Nets / Connectivity Errors: This section details discrepancies in how nets are connected.

o   Shorts: When Schematic has more nets but layout has less nets, layout has short.

o   Opens: A single net in the schematic corresponds to two or more unconnected nets in the layout.

o   Incorrect Instances / Devices: Discrepancies in the number or type of devices.

o   Missing Devices: A device present in the schematic is not found in the corresponding location/netlist in the layout.

o   Extra Devices: A device extracted from the layout has no corresponding instance in the schematic. Debugging: Check if the device was accidentally deleted/added in the layout or schematic, or if the LVS tool misidentified a structure due to layout errors near the device.

o   Incorrect Ports: Mismatches in the number or names of top-level ports between schematic and layout.

o   Parameter Mismatches (Property Errors): Devices match in type and connectivity, but their calculated parameters (e.g., transistor Width, Length, Resistor value, Capacitor value) differ between schematic and layout beyond a specified tolerance.

o   Non-equivalent Points: This is a general term often used in the summary indicating the LVS check failed. The detailed sections (Incorrect Nets, Instances, Properties) provide the specifics.

o   LVS Report Interpretation: https://www.ijraset.com/fileserve.php?FID=25120 (Practical Approach to LVS paper)

 

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