KLayout Notes

Where the names come from

GDS files don't store layer names, only integer pairs of layer number and datatype (for example 66/20). The names come from a layer properties file (.lyp), an XML file that maps each pair to a name, color, and fill pattern:

<properties>
  <fill-color>#ff0000</fill-color>
  <name>poly.drawing - 66/20</name>
  <source>66/20@1</source>
</properties>

<source> is the pair to match (@1 means the first loaded layout) and <name> is the label shown in the layer panel. Without a .lyp, KLayout shows only the raw pairs (66/20).

For sky130 the file ships with the PDK at $PDK_ROOT/sky130A/libs.tech/klayout/tech/sky130A.lyp; this site uses a copy in gds/. To rename layers or change colors, edit the XML or adjust the layer panel in KLayout and use File → Save Layer Properties.

Datatypes (purposes)

The same physical layer carries several kinds of shapes. For met1 (layer 68):

Name	Pair	Meaning
met1.drawing	68/20	The metal geometry that is actually manufactured
met1.pin	68/16	Marks pin locations, for LVS and routing
met1.label	68/5	Text labels naming nets
met1.net	68/23	Net-highlighting shapes
met1.res	68/13	Marks a metal resistor
met1.blockage	68/10	"Don't route here" areas for place-and-route
met1.boundary	68/4	Cell boundary on this layer

So met1.drawing and met1.pin are both metal 1. The first becomes metal on the chip; the second is bookkeeping for the design tools.

sky130 drawing layers

From sky130A.lyp, bottom of the stack to top:

Layer	Pair	What it is
nwell	64/20	N-well (body of PMOS devices)
diff	65/20	Active area: transistor source/drain
tap	65/44	Active area for well/substrate ties
nsdm	93/44	N+ source/drain implant
psdm	94/20	P+ source/drain implant
poly	66/20	Polysilicon (gates)
npc	95/20	Nitride poly cut (under poly contacts)
licon1	66/44	Contact: diff/tap/poly to li1
li1	67/20	Local interconnect
mcon	67/44	Contact: li1 to met1
met1	68/20	Metal 1
via	68/44	Via: met1 to met2
met2	69/20	Metal 2
via2	69/44	Via: met2 to met3
met3	70/20	Metal 3
capm	89/44	MiM capacitor plate (over met3)
via3	70/44	Via: met3 to met4
met4	71/20	Metal 4
via4	71/44	Via: met4 to met5
met5	72/20	Metal 5
pad	76/20	Passivation opening over bond pads

sky130 conventions worth knowing

• Contacts and vias share the number of the layer they sit on, with datatype 44: licon1 is 66/44 (poly is 66/20), mcon is 67/44 (li1 is 67/20), via is 68/44 (met1 is 68/20). The datatype is what tells them apart.
• "drawing" isn't always datatype 20. Contacts, vias, tap (65/44), and nsdm (93/44) use 44 for their drawn shapes.
• Don't confuse layer numbers across PDKs. 66/20 is poly in sky130 but can mean something else entirely in another process; always go through the PDK's .lyp or layer map.