KLayout

KLayout is an open-source tool for layout visualization, editing, DRC, and LVS. It supports multiple layout formats (GDSII, OASIS, DEF, LEF) and provides both a GUI and scripting APIs (Python and Ruby). KLayout is widely used for physical verification and design inspection in open-source flows.

Key features

• View, edit, and merge GDSII, OASIS, and DEF/LEF files.
• Design Rule Check (DRC) and Layout-vs-Schematic (LVS) verification.
• Layer mapping and hierarchical inspection of standard-cell designs.
• Scripting via Python or Ruby (batch and GUI modes).
• Integration with Magic, Netgen, Xschem, and OpenROAD.
• Compatible with open-source PDKs such as Sky130, GF180, and IHP-SG13G2.

Typical workflow integration

Step	Role of KLayout	Input	Output
During PnR (digital)	Inspect DEF/GDS generated by OpenROAD	.def, .gds, .lef	Visualization, geometry check
During layout (analog)	Edit and overlay cells, verify geometry	.gds, .mag, .oas	Corrected GDS
For sign-off	Run DRC/LVS scripts from open PDKs	.gds + .spice	DRC/LVS reports

Launching KLayout

GUI mode

klayout &

Command-line mode (batch)

klayout -b -r scripts/drc_check.lydrc -rd layout=mychip.gds -rd report=reports/drc.lyrdb

Options

Option	Description
-b	Batch mode (no GUI)
-r	Run a DRC/LVS or macro script
-rd	Define runtime variables accessible in the script
-nc	Skip configuration loading
-zz	Start with empty layout

File formats and conversions

Task	Command / Menu	Description
Import DEF/LEF	File → Import → LEF/DEF	Convert digital layouts from OpenROAD
Merge layouts	Tools → Merge Cells	Combine multiple GDS files
Save to OASIS	File → Save As...	Smaller binary output
Export layer map	File → Layer Properties... → Export	Save or reuse color map configuration

Running DRC in KLayout

KLayout includes a built-in DRC engine that uses a Ruby or Python syntax to define rules.

Example DRC script (Ruby)

scripts/drc_check.lydrc

report("DRC report")

layout = Layout::read($layout)
top = layout.top_cell

# Example rules (using micron units)
metal1 = input(1, 0)
metal1.space(0.3.um).output("M1 spacing violation")
metal1.width(0.3.um).output("M1 min width violation")

report.save($report)

Run it:

klayout -b -r scripts/drc_check.lydrc \
  -rd layout=results/chip.gds \
  -rd report=reports/drc.lyrdb

Outputs:

• reports/drc.lyrdb – viewable directly in KLayout (Tools → Marker Browser)
• On-screen DRC markers (colored overlay on the layout)

Running LVS in KLayout

KLayout can perform schematic-to-layout comparison using its LVS plugin. It supports SPICE and Verilog netlists.

Example LVS command

klayout -b -r scripts/lvs_run.lylvs \
  -rd layout=layout/chip.gds \
  -rd schematic=netlists/chip.spice \
  -rd setup=tech/sky130A_setup.lvs \
  -rd report=reports/lvs.lyrdb

Typical setup file:

provided in $PDK_ROOT/$pdk/libs.tech/klayout/lvs/.

Outputs:

• lvs.lyrdb — LVS report file (viewable in KLayout)
• lvs.log — textual summary of matched/unmatched nets/devices

Scripting with Python

KLayout includes a full Python API (pya). You can automate DRC checks, GDS merges, or layout inspection.

Example: generate a layout snapshot

import pya

layout = pya.Layout()
layout.read("results/chip.gds")
top = layout.top_cell()
bbox = top.bbox()

print(f"Top cell: {top.name}, Bounding box: {bbox}")

Run:

klayout -b -r myscript.py

Visualization and debugging tips

• Use “Layer Properties” (Ctrl+L) to toggle layer visibility and colors.
• Hierarchy browser (Ctrl+H) shows cell hierarchy and instances.
• Use “Measure” (M key) to check distances or width violations.
• For dense designs, enable “Low-res mode” to speed up rendering.
• Export screenshots (File → Save Screenshot) for documentation.

Integration with open tools

Tool	Purpose
OpenROAD	View routed GDS or DEF; check PDN, congestion, or macro placement
Magic	Cross-check layout (GDS ↔ MAG)
Netgen	Use same LVS setup file for cross-tool consistency
Xschem	Generate SPICE schematic netlists for LVS comparison
Ngspice	Post-layout simulation after extraction
Open-PDKs	Provide layer maps, DRC/LVS rules, and setup scripts for KLayout

Example sign-off flow using KLayout

Step	Tool	Output
Routing	OpenROAD	chip.def / chip.gds
GDS inspection	KLayout	visual check
DRC check	KLayout	drc.lyrdb
LVS comparison	KLayout / Netgen	lvs.lyrdb
Sign-off export	KLayout	final chip.gds

Best practices

• Always use the PDK-provided DRC/LVS setup files.
• Keep a consistent layer mapping across Magic and KLayout.
• Validate GDS output from OpenROAD before tape-out.
• Save marker reports (.lyrdb) — they are lightweight and easy to share.
• Automate recurring checks with Python batch scripts.
• Use “Diff mode” (Tools → Layout Diff) to compare two GDS revisions.

Further reading