forbidden_unless_labeled¶

A candidate device that lands in a forbidden region is an error, unless it belongs to an isolation structure tagged by a text label. Every layer role is supplied positionally, so the check is layer-name-agnostic and reusable across PDKs.

Its first (and so far only) user is IHP SG13G2’s Ant.h: an isolated n-type diffusion diode (a Schottky/antenna-protection structure) is forbidden inside an NWell unless it sits inside an isolbox-labelled isolation cluster.

Semantics¶

The rule derives a chain of intermediate regions from the ten positional layers:

nactiv_con   = Activ − GatPoly − (pSD ∪ nSD.block)
cand         = nactiv_con ∩ Recog.diode − Recog.esd
nact_nwell   = nactiv_con ∩ (NWell ∪ PWell.block)
schottky     = nBuLay ∩ Recog.diode ∩ NWell ∩ nSD.block
isolbox_1    = (nBuLay      interacting Recog.diode interacting nact_nwell)
             ∪ (Recog.diode interacting nBuLay      interacting nact_nwell)
isolbox      = isolbox_1 not_interacting schottky, then interacting text ``<text>``
error        = (cand not_interacting isolbox) ∩ NWell

A violation is reported for each connected error region: a candidate diffusion diode that lies in an NWell and is not part of an isolation cluster carrying the exemption label.

Every step is a lazy, tile-bounded virtual layer — the plain union/difference/intersection steps are local per tile; the interacting / not_interacting / with_text steps use the same whole-region stitching that min_region_density-style area checks rely on, so a dense, chip-wide layer like Activ or GatPoly is never unioned globally. This matters in practice: an earlier implementation that globally merged the (anchor-clipped) dense layers worked on small blocks but ran out of memory on a full SoC top cell, where antenna-diode markers are as numerous and widespread as the diffusion itself.

Layers¶

Ten positional roles, in this exact order:

Position	Role	IHP SG13G2 example
0	Base diffusion	`Activ`
1	Gate poly (subtracted from the base)	`GatPoly`
2	p-type source/drain implant (subtracted)	`pSD`
3	n-type source/drain block (subtracted; also used in `schottky`)	`nSD.block`
4	Diode device-recognition marker	`Recog.diode`
5	ESD device-recognition marker (exempted from the candidate set)	`Recog.esd`
6	N-well	`NWell`
7	P-well block	`PWell.block`
8	Buried layer (isolation-cluster anchor)	`nBuLay`
9	Text label layer (the exemption tag lives here)	`TEXT`

Parameters¶

None. value is unused (set it to 0.0 by convention). The exemption label comes from the rule’s text field, not params.

text: The label string that exempts a candidate’s isolation cluster. Matched case-insensitively; a trailing * makes it a prefix match (the same convention as the connectivity engine’s text lookups). Required — an absent or empty text means nothing is ever exempted.

Violation markers¶

One point marker per connected error region, at a representative point inside it (the centroid of its largest tile-clipped piece). A region spanning several tiles is still reported once.

KLayout equivalent¶

Mirrors the derivation in IHP’s reference antenna.drc for the unlabelled-Schottky-diode rule: the same chain of AND/NOT/interacting/interacting_with_text operators, evaluated here as tiled virtual layers rather than one-shot whole-chip booleans.

Example¶

- id: Ant.h
  check: forbidden_unless_labeled
  layers: [Activ, GatPoly, pSD, nSD.block, Recog.diode, Recog.esd, NWell, PWell.block, nBuLay, TEXT]
  value: 0.0
  text: isolbox