klayout-drc

name	klayout-drc
description	Use when writing, reading, or understanding KLayout DRC rules (.drc files). Provides KLayout Ruby DSL syntax, common DRC patterns, and reference lookup instructions.

KLayout DRC Rule Writing

Reference Documentation

The plugin bundles the full KLayout DRC + Layout reference (3.7K lines). Find it by running:

find ~ -path "*/klayout-tools/refs/klayout_docs_v2.txt" -print -quit

Use Grep to search for specific operations (e.g., separation, enclosing, sized) and Read with line offsets to get surrounding context. Do NOT load the full file into context at once.

For SKY130 layer numbers, read the bundled reference:

find ~ -path "*/klayout-tools/refs/sky130_layers.md" -print -quit

DRC File Template

Every .drc file must have this structure:

source($input)
report("DRC Rule Title", $output)

# Layer inputs
layer_a = input(LAYER_NUM, DATATYPE)
layer_b = input(LAYER_NUM, DATATYPE)

# Rules — each outputs violations to a named category
layer_a.width(MIN_WIDTH.um).output("CATEGORY_NAME", "Description")

Key Rules

1. Always include source($input) and report("Title", $output) at the top
2. Use .um suffix on all distance values: 0.14.um, 5.0.um
3. Layer input uses GDS layer number and datatype: input(68, 20) for met1
4. Every check must end with .output("CATEGORY", "description")
5. Space vs separation: .space() is same-layer, .separation() is cross-layer
6. Overlap + separation: For proximity rules, check BOTH overlap (&) AND spacing

Common Patterns

Width + Space (single layer)

m1 = input(68, 20)
m1.width(0.14.um).output("M1_WIDTH_LT_0p14um", "Metal1 width < 0.14um")
m1.space(0.14.um).output("M1_SPACE_LT_0p14um", "Metal1 space < 0.14um")

Enclosure (layer A must enclose layer B by minimum distance)

m1   = input(68, 20)
mcon = input(67, 44)
# Shrink m1, then check if mcon extends beyond shrunk boundary
(mcon - m1.sized(-0.03.um)).output("MCON_M1_ENC_LT_0p03um", "MCON enclosure by M1 < 0.03um")

Overlap + Separation (two layers must not be too close)

dnw = input(64, 18)
pnp = input(125, 5)
(dnw & pnp).output("DNW_PNP_OVERLAP", "DNW and PNP overlap")
dnw.separation(pnp, 5.0.um).output("DNW_PNP_SEP", "DNW to PNP sep < 5.0um")

Minimum Area

li1 = input(67, 20)
li1.drc(area < 0.0561.um).output("LI1_AREA_LT_0p0561um2", "LI1 area < 0.0561um2")

Common Mistakes

Mistake	Fix
Missing source($input)	Add at top of file
Missing .um suffix	0.14 → 0.14.um
Using space for cross-layer	Use separation instead
Only checking spacing, not overlap	Add (a & b).output(...) for overlap case
Wrong layer/datatype numbers	Check SKY130 layer reference