Signoff checks: DRC, LVS, antenna, XOR, and manufacturability

A GDS file is only useful if its geometry is legal and its extracted connectivity matches the intended circuit.

Overview

Several different checks answer different questions.

Passing one does not imply passing the others.

DRC

Design Rule Checking tests geometry rules such as:

minimum metal width
minimum spacing
via enclosure
minimum area
layer interaction rules

LVS

Layout Versus Schematic asks:

Does the circuit extracted from the physical layout
match the intended netlist?

DRC can pass while LVS fails.

A beautiful legal layout can still be electrically wrong.

XOR

LibreLane can stream GDS through more than one backend and compare them.

Geometric differences may reveal stream-out inconsistencies.

Prerequisites

• PPA analysis

Steps

1. Find DRC steps

RUN=$(ls -dt runs/* | head -1)

find "$RUN" -maxdepth 1 -type d \
  \( -iname '*magic-drc*' -o -iname '*klayout-drc*' \)

2. Search DRC reports

grep -RniE "drc|violation|error|count" \
  "$RUN"/*drc* 2>/dev/null | head -120

Record Magic and KLayout DRC results separately if both are present.

3. Find LVS

LVS_DIR=$(find "$RUN" -maxdepth 1 -type d \
  -iname '*netgen-lvs*' | head -1)

echo "$LVS_DIR"

Inspect:

grep -RniE "match|mismatch|lvs|error|net|device" \
  "$LVS_DIR" | head -150

The desired result is logical/layout equivalence under the checker's rules.

4. Find antenna checks

find "$RUN" -maxdepth 1 -type d -iname '*antenna*'

Inspect the reports before and after repair when both exist.

5. Find XOR

find "$RUN" -maxdepth 1 -type d -iname '*xor*'

Look for the reported geometric-difference count.

6. Read the manufacturability summary

Find:

find "$RUN" -maxdepth 2 -type f \
  -iname '*manufactur*' -o -iname '*summary*'

Also inspect:

error.log
warning.log

from the run root.

7. Do not ignore deferred errors

Some flows continue through multiple checks so you can collect more information before the final failure.

That means:

flow reached GDS

does not necessarily mean:

flow passed signoff

Read the final status and checker reports.

8. Understand what "clean" means

For this educational macro, a strong result is:

0 DRC violations
LVS clean
0 unresolved antenna violations
0 disconnected pins/nets
no setup violations
no hold violations
acceptable IR-drop report
consistent stream-out/XOR result

The exact requirements for a real tapeout are defined by the foundry/shuttle/integration platform.

9. Save evidence

Save:

screenshots/drc_clean.png
screenshots/lvs_clean.png
screenshots/signoff_summary.png

Results

Create:

Checklist

• Checked Magic DRC
• Checked KLayout DRC
• Checked LVS
• Checked antenna
• Checked XOR
• Checked setup
• Checked hold
• Checked run error/warning logs
• Continued to page 23

Questions? Ask in the network Discord.