min_enclosure

Every shape on the enclosed layer (layers[1]) must sit inside an enclosing region (layers[0]) with at least value µm of margin — on all sides, or on the sides sides names: at least one (a wire’s endcap round a via), the sides bordering a short one, or the side facing a narrow track’s tip.

Semantics

For each enclosed shape, the engine finds the enclosing region(s) that fully contain it and measures the margin as a facing-edge-pair scan: each inner edge is paired with parallel outer edges that have positive projected overlap onto it (KLayout’s projection metric, not a raw closest-point distance), and the worst (smallest) margin among those pairs is the shape’s measured enclosure. A shape not contained by any enclosing region is itself a violation (“not enclosed at all”) unless interacting_only says otherwise.

The measurement is exact on the grid: the coordinates are integers, so a margin between parallel walls is a ratio of two integers and one read at a chamfer under the euclidian metric is compared squared as one, against value rounded up to whole DBU once. Whether a vertex is inside, on or off the enclosing contour is a matter of signs, never of a tolerance. The one reading that is not exact is the per-side margin sides: adjacent takes off a wall at another angle than the side, found by interpolation.

An inner edge that lies exactly on the enclosing contour — a coincident segment, offset ~0 — is geometrically ambiguous: it’s either a genuinely flush 0-margin violation, or an artifact of the enclosed layer having been clipped to the enclosing one by an intersection virtual layer (in which case the “0 margin” isn’t a real design fact, just where the boolean cut it off). The geometry can’t tell these apart, and neither can KLayout — its rules pick per-flag. Two params mirror that choice:

  • skip_coincident drops just the coincident edge pairs, still measuring the region’s other, real margins. Used when a region is deliberately clipped to its enclosing layer on one side (e.g. a seal-ring conductor intersected with EdgeSeal) but must still be checked on the sides that aren’t.

  • skip_clipped is the stronger, region-level form: if any edge of a region is coincident with the enclosing contour, the whole region is skipped, not just that edge pair. This encodes a “surrounded entirely by” semantics — a shape that reaches the enclosing boundary at all is out of scope for this rule (typically because crossing the boundary makes it a different rule’s concern, e.g. IHP’s NW.e explicitly title-scopes itself to ties surrounded entirely by NWell; one that crosses the edge is NW.d territory instead).

Neither flag is on by default: an untouched coincident edge is treated as a real 0-margin violation (e.g. Cnt.c, where a contact genuinely straddling the edge of its active area is exactly the defect being caught).

Layers

Two layers, positional:

  1. layers[0] — the enclosing region.

  2. layers[1] — the enclosed shapes being measured.

Parameters

sides

Optional. Which sides of the enclosed shape have to make the margin. All four read the same per-side margins and differ only in the verdict.

all (the default)

Every side: the worst side must reach value.

any

At least one side: the best side must reach value — the wire endcap. A via at a metal corner is an endcap on one side, with the ordinary rule at a much smaller value covering the rest (IHP V1.c at 0.01 µm alongside V1.c1 at 0.05 µm with sides: any: mostly flush is fine, but one side needs real margin). The margin is the enclosing region’s bounding-box margin on each side, deliberately: an edge-to-contour distance is corner-limited and would understate a long endcap run.

adjacent

A side enclosed by less than trigger is allowed only if the sides bordering it reach value (GF180 S.CO.6_ii: a contact may sit flush on one side when the two sides next to it have the full margin).

line_end

Only the side facing a line end of the enclosing layer — the cap across the tip of a track narrower than max_width that runs for at least min_length (GF180 CO.6a). This is the one mode whose condition comes from the enclosing layer’s own shape: a narrow line’s tip pulls back during processing, so metal that merely reaches the via on paper may not reach it on silicon. The sidewalls are the ordinary rule’s business.

metric

Optional. projection (the default) pairs each inner edge with the parallel outer edges that project onto it; euclidian reads the closest approach, which is KLayout’s own default. The two agree on orthogonal geometry and part company at any corner that is not square.

over (a layer_params entry)

Optional. Only a pair whose margin lies over that layer counts - read just outside the inner wall, so a wall flush with the layer’s own edge has no margin to read - KLayout’s .ext_and(layer) on a margin read. IHP’s TGO.c reads the gate to the thick oxide’s edge where that edge crosses the Activ (over: Activ); the oxide’s edge past the Activ’s end is TGO.a’s, and an Activ ending inside the oxide has no oxide edge over it at all.

trigger

With sides: adjacent: the margin below which a side starts asking something of the sides bordering it.

max_width / min_length

With sides: line_end: what counts as a narrow track, and how far it must run before it is a line rather than a notch.

interacting_only

Off by default (every enclosed shape must be fully inside some enclosing region, or it’s a violation). When set, a shape that overlaps no enclosing region at all is out of scope for this rule entirely (skipped, not flagged) — mirrors KLayout’s enclosed only checking shapes that actually interact with the enclosing layer (a via nowhere near a MIM cap isn’t “a MIM via” to begin with). A shape that partially overlaps an enclosing region is still measured, using only the facing pairs on its contained side — which is what an extension rule is: a cover that must reach past the target it crosses by so much, measured on the target’s walls under the cover and not on the ends that run out past it (IHP Gat.c, the poly endcap over Activ; Sal.c, the salicide block over the active it crosses). The rule’s metric applies here as anywhere: under euclidian a chamfered endcap is read at its corner, and a corner the tile’s cut made is read on the whole wall or left to the tile past it, never taken for a corner of the shape.

skip_coincident

Off by default. Ignore inner/outer edge pairs that are coincident (flush, ~0 offset) — see Semantics.

skip_clipped

Off by default. Skip the whole enclosed region if any of its edges is coincident with the enclosing contour — see Semantics. Also halo-robust: whether an edge is clipped is a purely local property of the region, unlike its remaining margins, whose owning tile can shift with per-suite halo differences.

Violation markers

  • Fully unenclosed shape (no interacting_only): one point marker at the shape’s centroid.

  • Contained (or, under interacting_only, partially overlapping) shape with walls short of value: one edge marker per run of short walls, at the run’s worst margin. Walls that meet at a corner are one run, so a shape short on one side or on two adjacent sides is one marker, a shape short on two opposite sides two, and a comb short at three fingers three; a ring short all the way round is one run for its outer boundary and one for its hole. KLayout reports an edge pair per wall.

  • Under sides: any and for max_enclosure, which read the shape as a whole, one marker per shape; under sides: any it sits on the shape’s first contour edge, since the bounding-box reduction names no single wall.

A shape is read as one whole whatever the tiling: a shape spanning several tiles is put together from its pieces, and the count does not move with the tile size.

KLayout equivalent

inner.enclosed(outer, value, metric: RBA::Region::projection, ...) — skip_coincident mirrors consider_intersecting_edges: false / without_distance(0); skip_clipped has no single built-in KLayout flag and is a region-level generalization of the same idea. Neither sides: any nor adjacent is a single operator; line_end is the enclosed of the via against the enclosing layer’s line-end edges alone.

Example

- id: Cnt.c
  check: min_enclosure
  layers: [Activ, ContOnActivNoSRAMVaricap]
  value: 0.07

# NW.e: only ties fully surrounded by NWell are in scope — one crossing the
# boundary is NW.d's concern instead.
- id: NW.e
  check: min_enclosure
  layers: [NWell, NActivInNWellNoTGO]
  value: 0.24
  params:
    skip_clipped: 1

# Seal.d: SealActiv is itself an `Activ AND EdgeSeal` intersection, so its own
# inward edge is a clip artifact, not a real margin — skip_coincident drops just
# that edge while still checking the genuine cross-frame margins.
- id: Seal.d
  check: min_enclosure
  layers: [SealActiv, SealCont]
  value: 1.30
  params:
    skip_coincident: 1
    interacting_only: 1

# V1.c allows the via to be nearly flush with Metal1 on most sides; V1.c1 requires a
# real endcap on at least one side.
- id: V1.c
  check: min_enclosure
  layers: [Metal1, Via1NoSealring]
  value: 0.01
- id: V1.c1
  check: min_enclosure
  layers: [Metal1, Via1NoSealring]
  value: 0.05
  params:
    sides: any

# Sal.c: SalBlock must extend 0.20 µm past the Activ or GatPoly it crosses; the
# target's own ends, outside the block, are not measured.
- id: Sal.c
  check: min_enclosure
  layers: [SalBlock, ActivOrGatPoly]
  value: 0.20
  params:
    interacting_only: 1